Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

25 files changed, 12487 insertions, 0 deletions

diff --git a/compiler/rustc_lint/Cargo.toml b/compiler/rustc_lint/Cargo.toml
new file mode 100644
index 000000000..7c0f2c440
--- /dev/null
+++ b/compiler/rustc_lint/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+name = "rustc_lint"
+version = "0.0.0"
+edition = "2021"
+
+[dependencies]
+tracing = "0.1"
+unicode-security = "0.0.5"
+rustc_middle = { path = "../rustc_middle" }
+rustc_ast_pretty = { path = "../rustc_ast_pretty" }
+rustc_attr = { path = "../rustc_attr" }
+rustc_errors = { path = "../rustc_errors" }
+rustc_hir = { path = "../rustc_hir" }
+rustc_target = { path = "../rustc_target" }
+rustc_ast = { path = "../rustc_ast" }
+rustc_span = { path = "../rustc_span" }
+rustc_data_structures = { path = "../rustc_data_structures" }
+rustc_feature = { path = "../rustc_feature" }
+rustc_index = { path = "../rustc_index" }
+rustc_session = { path = "../rustc_session" }
+rustc_trait_selection = { path = "../rustc_trait_selection" }
+rustc_parse_format = { path = "../rustc_parse_format" }
+rustc_infer = { path = "../rustc_infer" }
+rustc_type_ir = { path = "../rustc_type_ir" }
+rustc_macros = { path = "../rustc_macros" }
diff --git a/compiler/rustc_lint/src/array_into_iter.rs b/compiler/rustc_lint/src/array_into_iter.rs
new file mode 100644
index 000000000..121fefdc6
--- /dev/null
+++ b/compiler/rustc_lint/src/array_into_iter.rs
@@ -0,0 +1,155 @@
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_errors::{fluent, Applicability};
+use rustc_hir as hir;
+use rustc_middle::ty;
+use rustc_middle::ty::adjustment::{Adjust, Adjustment};
+use rustc_session::lint::FutureIncompatibilityReason;
+use rustc_span::edition::Edition;
+use rustc_span::symbol::sym;
+use rustc_span::Span;
+
+declare_lint! {
+    /// The `array_into_iter` lint detects calling `into_iter` on arrays.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,edition2018
+    /// # #![allow(unused)]
+    /// [1, 2, 3].into_iter().for_each(|n| { *n; });
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Since Rust 1.53, arrays implement `IntoIterator`. However, to avoid
+    /// breakage, `array.into_iter()` in Rust 2015 and 2018 code will still
+    /// behave as `(&array).into_iter()`, returning an iterator over
+    /// references, just like in Rust 1.52 and earlier.
+    /// This only applies to the method call syntax `array.into_iter()`, not to
+    /// any other syntax such as `for _ in array` or `IntoIterator::into_iter(array)`.
+    pub ARRAY_INTO_ITER,
+    Warn,
+    "detects calling `into_iter` on arrays in Rust 2015 and 2018",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>",
+        reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
+    };
+}
+
+#[derive(Copy, Clone, Default)]
+pub struct ArrayIntoIter {
+    for_expr_span: Span,
+}
+
+impl_lint_pass!(ArrayIntoIter => [ARRAY_INTO_ITER]);
+
+impl<'tcx> LateLintPass<'tcx> for ArrayIntoIter {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+        // Save the span of expressions in `for _ in expr` syntax,
+        // so we can give a better suggestion for those later.
+        if let hir::ExprKind::Match(arg, [_], hir::MatchSource::ForLoopDesugar) = &expr.kind {
+            if let hir::ExprKind::Call(path, [arg]) = &arg.kind {
+                if let hir::ExprKind::Path(hir::QPath::LangItem(
+                    hir::LangItem::IntoIterIntoIter,
+                    ..,
+                )) = &path.kind
+                {
+                    self.for_expr_span = arg.span;
+                }
+            }
+        }
+
+        // We only care about method call expressions.
+        if let hir::ExprKind::MethodCall(call, args, _) = &expr.kind {
+            if call.ident.name != sym::into_iter {
+                return;
+            }
+
+            // Check if the method call actually calls the libcore
+            // `IntoIterator::into_iter`.
+            let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id).unwrap();
+            match cx.tcx.trait_of_item(def_id) {
+                Some(trait_id) if cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_id) => {}
+                _ => return,
+            };
+
+            // As this is a method call expression, we have at least one argument.
+            let receiver_arg = &args[0];
+            let receiver_ty = cx.typeck_results().expr_ty(receiver_arg);
+            let adjustments = cx.typeck_results().expr_adjustments(receiver_arg);
+
+            let Some(Adjustment { kind: Adjust::Borrow(_), target }) = adjustments.last() else {
+                return
+            };
+
+            let types =
+                std::iter::once(receiver_ty).chain(adjustments.iter().map(|adj| adj.target));
+
+            let mut found_array = false;
+
+            for ty in types {
+                match ty.kind() {
+                    // If we run into a &[T; N] or &[T] first, there's nothing to warn about.
+                    // It'll resolve to the reference version.
+                    ty::Ref(_, inner_ty, _) if inner_ty.is_array() => return,
+                    ty::Ref(_, inner_ty, _) if matches!(inner_ty.kind(), ty::Slice(..)) => return,
+                    // Found an actual array type without matching a &[T; N] first.
+                    // This is the problematic case.
+                    ty::Array(..) => {
+                        found_array = true;
+                        break;
+                    }
+                    _ => {}
+                }
+            }
+
+            if !found_array {
+                return;
+            }
+
+            // Emit lint diagnostic.
+            let target = match *target.kind() {
+                ty::Ref(_, inner_ty, _) if inner_ty.is_array() => "[T; N]",
+                ty::Ref(_, inner_ty, _) if matches!(inner_ty.kind(), ty::Slice(..)) => "[T]",
+                // We know the original first argument type is an array type,
+                // we know that the first adjustment was an autoref coercion
+                // and we know that `IntoIterator` is the trait involved. The
+                // array cannot be coerced to something other than a reference
+                // to an array or to a slice.
+                _ => bug!("array type coerced to something other than array or slice"),
+            };
+            cx.struct_span_lint(ARRAY_INTO_ITER, call.ident.span, |lint| {
+                let mut diag = lint.build(fluent::lint::array_into_iter);
+                diag.set_arg("target", target);
+                diag.span_suggestion(
+                    call.ident.span,
+                    fluent::lint::use_iter_suggestion,
+                    "iter",
+                    Applicability::MachineApplicable,
+                );
+                if self.for_expr_span == expr.span {
+                    diag.span_suggestion(
+                        receiver_arg.span.shrink_to_hi().to(expr.span.shrink_to_hi()),
+                        fluent::lint::remove_into_iter_suggestion,
+                        "",
+                        Applicability::MaybeIncorrect,
+                    );
+                } else if receiver_ty.is_array() {
+                    diag.multipart_suggestion(
+                        fluent::lint::use_explicit_into_iter_suggestion,
+                        vec![
+                            (expr.span.shrink_to_lo(), "IntoIterator::into_iter(".into()),
+                            (
+                                receiver_arg.span.shrink_to_hi().to(expr.span.shrink_to_hi()),
+                                ")".into(),
+                            ),
+                        ],
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+                diag.emit();
+            })
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
new file mode 100644
index 000000000..bd58021f7
--- /dev/null
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -0,0 +1,3172 @@
+//! Lints in the Rust compiler.
+//!
+//! This contains lints which can feasibly be implemented as their own
+//! AST visitor. Also see `rustc_session::lint::builtin`, which contains the
+//! definitions of lints that are emitted directly inside the main compiler.
+//!
+//! To add a new lint to rustc, declare it here using `declare_lint!()`.
+//! Then add code to emit the new lint in the appropriate circumstances.
+//! You can do that in an existing `LintPass` if it makes sense, or in a
+//! new `LintPass`, or using `Session::add_lint` elsewhere in the
+//! compiler. Only do the latter if the check can't be written cleanly as a
+//! `LintPass` (also, note that such lints will need to be defined in
+//! `rustc_session::lint::builtin`, not here).
+//!
+//! If you define a new `EarlyLintPass`, you will also need to add it to the
+//! `add_early_builtin!` or `add_early_builtin_with_new!` invocation in
+//! `lib.rs`. Use the former for unit-like structs and the latter for structs
+//! with a `pub fn new()`.
+//!
+//! If you define a new `LateLintPass`, you will also need to add it to the
+//! `late_lint_methods!` invocation in `lib.rs`.
+
+use crate::{
+    types::{transparent_newtype_field, CItemKind},
+    EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext,
+};
+use rustc_ast::attr;
+use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast::visit::{FnCtxt, FnKind};
+use rustc_ast::{self as ast, *};
+use rustc_ast_pretty::pprust::{self, expr_to_string};
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::stack::ensure_sufficient_stack;
+use rustc_errors::{
+    fluent, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString,
+    LintDiagnosticBuilder, MultiSpan,
+};
+use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
+use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, PatKind, PredicateOrigin};
+use rustc_index::vec::Idx;
+use rustc_middle::lint::in_external_macro;
+use rustc_middle::ty::layout::{LayoutError, LayoutOf};
+use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::Instance;
+use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
+use rustc_span::edition::Edition;
+use rustc_span::source_map::Spanned;
+use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_span::{BytePos, InnerSpan, Span};
+use rustc_target::abi::VariantIdx;
+use rustc_trait_selection::traits::{self, misc::can_type_implement_copy};
+
+use crate::nonstandard_style::{method_context, MethodLateContext};
+
+use std::fmt::Write;
+use tracing::{debug, trace};
+
+// hardwired lints from librustc_middle
+pub use rustc_session::lint::builtin::*;
+
+declare_lint! {
+    /// The `while_true` lint detects `while true { }`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,no_run
+    /// while true {
+    ///
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// `while true` should be replaced with `loop`. A `loop` expression is
+    /// the preferred way to write an infinite loop because it more directly
+    /// expresses the intent of the loop.
+    WHILE_TRUE,
+    Warn,
+    "suggest using `loop { }` instead of `while true { }`"
+}
+
+declare_lint_pass!(WhileTrue => [WHILE_TRUE]);
+
+/// Traverse through any amount of parenthesis and return the first non-parens expression.
+fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
+    while let ast::ExprKind::Paren(sub) = &expr.kind {
+        expr = sub;
+    }
+    expr
+}
+
+impl EarlyLintPass for WhileTrue {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+        if let ast::ExprKind::While(cond, _, label) = &e.kind {
+            if let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind {
+                if let ast::LitKind::Bool(true) = lit.kind {
+                    if !lit.span.from_expansion() {
+                        let condition_span = e.span.with_hi(cond.span.hi());
+                        cx.struct_span_lint(WHILE_TRUE, condition_span, |lint| {
+                            lint.build(fluent::lint::builtin_while_true)
+                                .span_suggestion_short(
+                                    condition_span,
+                                    fluent::lint::suggestion,
+                                    format!(
+                                        "{}loop",
+                                        label.map_or_else(String::new, |label| format!(
+                                            "{}: ",
+                                            label.ident,
+                                        ))
+                                    ),
+                                    Applicability::MachineApplicable,
+                                )
+                                .emit();
+                        })
+                    }
+                }
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `box_pointers` lints use of the Box type.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(box_pointers)]
+    /// struct Foo {
+    ///     x: Box<isize>,
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint is mostly historical, and not particularly useful. `Box<T>`
+    /// used to be built into the language, and the only way to do heap
+    /// allocation. Today's Rust can call into other allocators, etc.
+    BOX_POINTERS,
+    Allow,
+    "use of owned (Box type) heap memory"
+}
+
+declare_lint_pass!(BoxPointers => [BOX_POINTERS]);
+
+impl BoxPointers {
+    fn check_heap_type(&self, cx: &LateContext<'_>, span: Span, ty: Ty<'_>) {
+        for leaf in ty.walk() {
+            if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
+                if leaf_ty.is_box() {
+                    cx.struct_span_lint(BOX_POINTERS, span, |lint| {
+                        lint.build(fluent::lint::builtin_box_pointers).set_arg("ty", ty).emit();
+                    });
+                }
+            }
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for BoxPointers {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        match it.kind {
+            hir::ItemKind::Fn(..)
+            | hir::ItemKind::TyAlias(..)
+            | hir::ItemKind::Enum(..)
+            | hir::ItemKind::Struct(..)
+            | hir::ItemKind::Union(..) => {
+                self.check_heap_type(cx, it.span, cx.tcx.type_of(it.def_id))
+            }
+            _ => (),
+        }
+
+        // If it's a struct, we also have to check the fields' types
+        match it.kind {
+            hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
+                for struct_field in struct_def.fields() {
+                    let def_id = cx.tcx.hir().local_def_id(struct_field.hir_id);
+                    self.check_heap_type(cx, struct_field.span, cx.tcx.type_of(def_id));
+                }
+            }
+            _ => (),
+        }
+    }
+
+    fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
+        let ty = cx.typeck_results().node_type(e.hir_id);
+        self.check_heap_type(cx, e.span, ty);
+    }
+}
+
+declare_lint! {
+    /// The `non_shorthand_field_patterns` lint detects using `Struct { x: x }`
+    /// instead of `Struct { x }` in a pattern.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// struct Point {
+    ///     x: i32,
+    ///     y: i32,
+    /// }
+    ///
+    ///
+    /// fn main() {
+    ///     let p = Point {
+    ///         x: 5,
+    ///         y: 5,
+    ///     };
+    ///
+    ///     match p {
+    ///         Point { x: x, y: y } => (),
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The preferred style is to avoid the repetition of specifying both the
+    /// field name and the binding name if both identifiers are the same.
+    NON_SHORTHAND_FIELD_PATTERNS,
+    Warn,
+    "using `Struct { x: x }` instead of `Struct { x }` in a pattern"
+}
+
+declare_lint_pass!(NonShorthandFieldPatterns => [NON_SHORTHAND_FIELD_PATTERNS]);
+
+impl<'tcx> LateLintPass<'tcx> for NonShorthandFieldPatterns {
+    fn check_pat(&mut self, cx: &LateContext<'_>, pat: &hir::Pat<'_>) {
+        if let PatKind::Struct(ref qpath, field_pats, _) = pat.kind {
+            let variant = cx
+                .typeck_results()
+                .pat_ty(pat)
+                .ty_adt_def()
+                .expect("struct pattern type is not an ADT")
+                .variant_of_res(cx.qpath_res(qpath, pat.hir_id));
+            for fieldpat in field_pats {
+                if fieldpat.is_shorthand {
+                    continue;
+                }
+                if fieldpat.span.from_expansion() {
+                    // Don't lint if this is a macro expansion: macro authors
+                    // shouldn't have to worry about this kind of style issue
+                    // (Issue #49588)
+                    continue;
+                }
+                if let PatKind::Binding(binding_annot, _, ident, None) = fieldpat.pat.kind {
+                    if cx.tcx.find_field_index(ident, &variant)
+                        == Some(cx.tcx.field_index(fieldpat.hir_id, cx.typeck_results()))
+                    {
+                        cx.struct_span_lint(NON_SHORTHAND_FIELD_PATTERNS, fieldpat.span, |lint| {
+                            let binding = match binding_annot {
+                                hir::BindingAnnotation::Unannotated => None,
+                                hir::BindingAnnotation::Mutable => Some("mut"),
+                                hir::BindingAnnotation::Ref => Some("ref"),
+                                hir::BindingAnnotation::RefMut => Some("ref mut"),
+                            };
+                            let suggested_ident = if let Some(binding) = binding {
+                                format!("{} {}", binding, ident)
+                            } else {
+                                ident.to_string()
+                            };
+                            lint.build(fluent::lint::builtin_non_shorthand_field_patterns)
+                                .set_arg("ident", ident.clone())
+                                .span_suggestion(
+                                    fieldpat.span,
+                                    fluent::lint::suggestion,
+                                    suggested_ident,
+                                    Applicability::MachineApplicable,
+                                )
+                                .emit();
+                        });
+                    }
+                }
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unsafe_code` lint catches usage of `unsafe` code.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(unsafe_code)]
+    /// fn main() {
+    ///     unsafe {
+    ///
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint is intended to restrict the usage of `unsafe`, which can be
+    /// difficult to use correctly.
+    UNSAFE_CODE,
+    Allow,
+    "usage of `unsafe` code"
+}
+
+declare_lint_pass!(UnsafeCode => [UNSAFE_CODE]);
+
+impl UnsafeCode {
+    fn report_unsafe(
+        &self,
+        cx: &EarlyContext<'_>,
+        span: Span,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        // This comes from a macro that has `#[allow_internal_unsafe]`.
+        if span.allows_unsafe() {
+            return;
+        }
+
+        cx.struct_span_lint(UNSAFE_CODE, span, decorate);
+    }
+
+    fn report_overridden_symbol_name(
+        &self,
+        cx: &EarlyContext<'_>,
+        span: Span,
+        msg: DiagnosticMessage,
+    ) {
+        self.report_unsafe(cx, span, |lint| {
+            lint.build(msg).note(fluent::lint::builtin_overridden_symbol_name).emit();
+        })
+    }
+
+    fn report_overridden_symbol_section(
+        &self,
+        cx: &EarlyContext<'_>,
+        span: Span,
+        msg: DiagnosticMessage,
+    ) {
+        self.report_unsafe(cx, span, |lint| {
+            lint.build(msg).note(fluent::lint::builtin_overridden_symbol_section).emit();
+        })
+    }
+}
+
+impl EarlyLintPass for UnsafeCode {
+    fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
+        if attr.has_name(sym::allow_internal_unsafe) {
+            self.report_unsafe(cx, attr.span, |lint| {
+                lint.build(fluent::lint::builtin_allow_internal_unsafe).emit();
+            });
+        }
+    }
+
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+        if let ast::ExprKind::Block(ref blk, _) = e.kind {
+            // Don't warn about generated blocks; that'll just pollute the output.
+            if blk.rules == ast::BlockCheckMode::Unsafe(ast::UserProvided) {
+                self.report_unsafe(cx, blk.span, |lint| {
+                    lint.build(fluent::lint::builtin_unsafe_block).emit();
+                });
+            }
+        }
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
+        match it.kind {
+            ast::ItemKind::Trait(box ast::Trait { unsafety: ast::Unsafe::Yes(_), .. }) => self
+                .report_unsafe(cx, it.span, |lint| {
+                    lint.build(fluent::lint::builtin_unsafe_trait).emit();
+                }),
+
+            ast::ItemKind::Impl(box ast::Impl { unsafety: ast::Unsafe::Yes(_), .. }) => self
+                .report_unsafe(cx, it.span, |lint| {
+                    lint.build(fluent::lint::builtin_unsafe_impl).emit();
+                }),
+
+            ast::ItemKind::Fn(..) => {
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
+                    self.report_overridden_symbol_name(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_no_mangle_fn,
+                    );
+                }
+
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
+                    self.report_overridden_symbol_name(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_export_name_fn,
+                    );
+                }
+
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
+                    self.report_overridden_symbol_section(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_link_section_fn,
+                    );
+                }
+            }
+
+            ast::ItemKind::Static(..) => {
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
+                    self.report_overridden_symbol_name(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_no_mangle_static,
+                    );
+                }
+
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
+                    self.report_overridden_symbol_name(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_export_name_static,
+                    );
+                }
+
+                if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::link_section) {
+                    self.report_overridden_symbol_section(
+                        cx,
+                        attr.span,
+                        fluent::lint::builtin_link_section_static,
+                    );
+                }
+            }
+
+            _ => {}
+        }
+    }
+
+    fn check_impl_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
+        if let ast::AssocItemKind::Fn(..) = it.kind {
+            if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::no_mangle) {
+                self.report_overridden_symbol_name(
+                    cx,
+                    attr.span,
+                    fluent::lint::builtin_no_mangle_method,
+                );
+            }
+            if let Some(attr) = cx.sess().find_by_name(&it.attrs, sym::export_name) {
+                self.report_overridden_symbol_name(
+                    cx,
+                    attr.span,
+                    fluent::lint::builtin_export_name_method,
+                );
+            }
+        }
+    }
+
+    fn check_fn(&mut self, cx: &EarlyContext<'_>, fk: FnKind<'_>, span: Span, _: ast::NodeId) {
+        if let FnKind::Fn(
+            ctxt,
+            _,
+            ast::FnSig { header: ast::FnHeader { unsafety: ast::Unsafe::Yes(_), .. }, .. },
+            _,
+            _,
+            body,
+        ) = fk
+        {
+            let msg = match ctxt {
+                FnCtxt::Foreign => return,
+                FnCtxt::Free => fluent::lint::builtin_decl_unsafe_fn,
+                FnCtxt::Assoc(_) if body.is_none() => fluent::lint::builtin_decl_unsafe_method,
+                FnCtxt::Assoc(_) => fluent::lint::builtin_impl_unsafe_method,
+            };
+            self.report_unsafe(cx, span, |lint| {
+                lint.build(msg).emit();
+            });
+        }
+    }
+}
+
+declare_lint! {
+    /// The `missing_docs` lint detects missing documentation for public items.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(missing_docs)]
+    /// pub fn foo() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint is intended to ensure that a library is well-documented.
+    /// Items without documentation can be difficult for users to understand
+    /// how to use properly.
+    ///
+    /// This lint is "allow" by default because it can be noisy, and not all
+    /// projects may want to enforce everything to be documented.
+    pub MISSING_DOCS,
+    Allow,
+    "detects missing documentation for public members",
+    report_in_external_macro
+}
+
+pub struct MissingDoc {
+    /// Stack of whether `#[doc(hidden)]` is set at each level which has lint attributes.
+    doc_hidden_stack: Vec<bool>,
+}
+
+impl_lint_pass!(MissingDoc => [MISSING_DOCS]);
+
+fn has_doc(attr: &ast::Attribute) -> bool {
+    if attr.is_doc_comment() {
+        return true;
+    }
+
+    if !attr.has_name(sym::doc) {
+        return false;
+    }
+
+    if attr.value_str().is_some() {
+        return true;
+    }
+
+    if let Some(list) = attr.meta_item_list() {
+        for meta in list {
+            if meta.has_name(sym::hidden) {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+impl MissingDoc {
+    pub fn new() -> MissingDoc {
+        MissingDoc { doc_hidden_stack: vec![false] }
+    }
+
+    fn doc_hidden(&self) -> bool {
+        *self.doc_hidden_stack.last().expect("empty doc_hidden_stack")
+    }
+
+    fn check_missing_docs_attrs(
+        &self,
+        cx: &LateContext<'_>,
+        def_id: LocalDefId,
+        article: &'static str,
+        desc: &'static str,
+    ) {
+        // If we're building a test harness, then warning about
+        // documentation is probably not really relevant right now.
+        if cx.sess().opts.test {
+            return;
+        }
+
+        // `#[doc(hidden)]` disables missing_docs check.
+        if self.doc_hidden() {
+            return;
+        }
+
+        // Only check publicly-visible items, using the result from the privacy pass.
+        // It's an option so the crate root can also use this function (it doesn't
+        // have a `NodeId`).
+        if def_id != CRATE_DEF_ID {
+            if !cx.access_levels.is_exported(def_id) {
+                return;
+            }
+        }
+
+        let attrs = cx.tcx.hir().attrs(cx.tcx.hir().local_def_id_to_hir_id(def_id));
+        let has_doc = attrs.iter().any(has_doc);
+        if !has_doc {
+            cx.struct_span_lint(MISSING_DOCS, cx.tcx.def_span(def_id), |lint| {
+                lint.build(fluent::lint::builtin_missing_doc)
+                    .set_arg("article", article)
+                    .set_arg("desc", desc)
+                    .emit();
+            });
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for MissingDoc {
+    fn enter_lint_attrs(&mut self, _cx: &LateContext<'_>, attrs: &[ast::Attribute]) {
+        let doc_hidden = self.doc_hidden()
+            || attrs.iter().any(|attr| {
+                attr.has_name(sym::doc)
+                    && match attr.meta_item_list() {
+                        None => false,
+                        Some(l) => attr::list_contains_name(&l, sym::hidden),
+                    }
+            });
+        self.doc_hidden_stack.push(doc_hidden);
+    }
+
+    fn exit_lint_attrs(&mut self, _: &LateContext<'_>, _attrs: &[ast::Attribute]) {
+        self.doc_hidden_stack.pop().expect("empty doc_hidden_stack");
+    }
+
+    fn check_crate(&mut self, cx: &LateContext<'_>) {
+        self.check_missing_docs_attrs(cx, CRATE_DEF_ID, "the", "crate");
+    }
+
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        match it.kind {
+            hir::ItemKind::Trait(..) => {
+                // Issue #11592: traits are always considered exported, even when private.
+                if cx.tcx.visibility(it.def_id)
+                    == ty::Visibility::Restricted(
+                        cx.tcx.parent_module_from_def_id(it.def_id).to_def_id(),
+                    )
+                {
+                    return;
+                }
+            }
+            hir::ItemKind::TyAlias(..)
+            | hir::ItemKind::Fn(..)
+            | hir::ItemKind::Macro(..)
+            | hir::ItemKind::Mod(..)
+            | hir::ItemKind::Enum(..)
+            | hir::ItemKind::Struct(..)
+            | hir::ItemKind::Union(..)
+            | hir::ItemKind::Const(..)
+            | hir::ItemKind::Static(..) => {}
+
+            _ => return,
+        };
+
+        let (article, desc) = cx.tcx.article_and_description(it.def_id.to_def_id());
+
+        self.check_missing_docs_attrs(cx, it.def_id, article, desc);
+    }
+
+    fn check_trait_item(&mut self, cx: &LateContext<'_>, trait_item: &hir::TraitItem<'_>) {
+        let (article, desc) = cx.tcx.article_and_description(trait_item.def_id.to_def_id());
+
+        self.check_missing_docs_attrs(cx, trait_item.def_id, article, desc);
+    }
+
+    fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
+        // If the method is an impl for a trait, don't doc.
+        if method_context(cx, impl_item.hir_id()) == MethodLateContext::TraitImpl {
+            return;
+        }
+
+        // If the method is an impl for an item with docs_hidden, don't doc.
+        if method_context(cx, impl_item.hir_id()) == MethodLateContext::PlainImpl {
+            let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
+            let impl_ty = cx.tcx.type_of(parent);
+            let outerdef = match impl_ty.kind() {
+                ty::Adt(def, _) => Some(def.did()),
+                ty::Foreign(def_id) => Some(*def_id),
+                _ => None,
+            };
+            let is_hidden = match outerdef {
+                Some(id) => cx.tcx.is_doc_hidden(id),
+                None => false,
+            };
+            if is_hidden {
+                return;
+            }
+        }
+
+        let (article, desc) = cx.tcx.article_and_description(impl_item.def_id.to_def_id());
+        self.check_missing_docs_attrs(cx, impl_item.def_id, article, desc);
+    }
+
+    fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'_>) {
+        let (article, desc) = cx.tcx.article_and_description(foreign_item.def_id.to_def_id());
+        self.check_missing_docs_attrs(cx, foreign_item.def_id, article, desc);
+    }
+
+    fn check_field_def(&mut self, cx: &LateContext<'_>, sf: &hir::FieldDef<'_>) {
+        if !sf.is_positional() {
+            let def_id = cx.tcx.hir().local_def_id(sf.hir_id);
+            self.check_missing_docs_attrs(cx, def_id, "a", "struct field")
+        }
+    }
+
+    fn check_variant(&mut self, cx: &LateContext<'_>, v: &hir::Variant<'_>) {
+        self.check_missing_docs_attrs(cx, cx.tcx.hir().local_def_id(v.id), "a", "variant");
+    }
+}
+
+declare_lint! {
+    /// The `missing_copy_implementations` lint detects potentially-forgotten
+    /// implementations of [`Copy`].
+    ///
+    /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(missing_copy_implementations)]
+    /// pub struct Foo {
+    ///     pub field: i32
+    /// }
+    /// # fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Historically (before 1.0), types were automatically marked as `Copy`
+    /// if possible. This was changed so that it required an explicit opt-in
+    /// by implementing the `Copy` trait. As part of this change, a lint was
+    /// added to alert if a copyable type was not marked `Copy`.
+    ///
+    /// This lint is "allow" by default because this code isn't bad; it is
+    /// common to write newtypes like this specifically so that a `Copy` type
+    /// is no longer `Copy`. `Copy` types can result in unintended copies of
+    /// large data which can impact performance.
+    pub MISSING_COPY_IMPLEMENTATIONS,
+    Allow,
+    "detects potentially-forgotten implementations of `Copy`"
+}
+
+declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
+
+impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
+        if !cx.access_levels.is_reachable(item.def_id) {
+            return;
+        }
+        let (def, ty) = match item.kind {
+            hir::ItemKind::Struct(_, ref ast_generics) => {
+                if !ast_generics.params.is_empty() {
+                    return;
+                }
+                let def = cx.tcx.adt_def(item.def_id);
+                (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
+            }
+            hir::ItemKind::Union(_, ref ast_generics) => {
+                if !ast_generics.params.is_empty() {
+                    return;
+                }
+                let def = cx.tcx.adt_def(item.def_id);
+                (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
+            }
+            hir::ItemKind::Enum(_, ref ast_generics) => {
+                if !ast_generics.params.is_empty() {
+                    return;
+                }
+                let def = cx.tcx.adt_def(item.def_id);
+                (def, cx.tcx.mk_adt(def, cx.tcx.intern_substs(&[])))
+            }
+            _ => return,
+        };
+        if def.has_dtor(cx.tcx) {
+            return;
+        }
+        let param_env = ty::ParamEnv::empty();
+        if ty.is_copy_modulo_regions(cx.tcx.at(item.span), param_env) {
+            return;
+        }
+        if can_type_implement_copy(
+            cx.tcx,
+            param_env,
+            ty,
+            traits::ObligationCause::misc(item.span, item.hir_id()),
+        )
+        .is_ok()
+        {
+            cx.struct_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, |lint| {
+                lint.build(fluent::lint::builtin_missing_copy_impl).emit();
+            })
+        }
+    }
+}
+
+declare_lint! {
+    /// The `missing_debug_implementations` lint detects missing
+    /// implementations of [`fmt::Debug`].
+    ///
+    /// [`fmt::Debug`]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(missing_debug_implementations)]
+    /// pub struct Foo;
+    /// # fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Having a `Debug` implementation on all types can assist with
+    /// debugging, as it provides a convenient way to format and display a
+    /// value. Using the `#[derive(Debug)]` attribute will automatically
+    /// generate a typical implementation, or a custom implementation can be
+    /// added by manually implementing the `Debug` trait.
+    ///
+    /// This lint is "allow" by default because adding `Debug` to all types can
+    /// have a negative impact on compile time and code size. It also requires
+    /// boilerplate to be added to every type, which can be an impediment.
+    MISSING_DEBUG_IMPLEMENTATIONS,
+    Allow,
+    "detects missing implementations of Debug"
+}
+
+#[derive(Default)]
+pub struct MissingDebugImplementations {
+    impling_types: Option<LocalDefIdSet>,
+}
+
+impl_lint_pass!(MissingDebugImplementations => [MISSING_DEBUG_IMPLEMENTATIONS]);
+
+impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
+        if !cx.access_levels.is_reachable(item.def_id) {
+            return;
+        }
+
+        match item.kind {
+            hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
+            _ => return,
+        }
+
+        let Some(debug) = cx.tcx.get_diagnostic_item(sym::Debug) else {
+            return
+        };
+
+        if self.impling_types.is_none() {
+            let mut impls = LocalDefIdSet::default();
+            cx.tcx.for_each_impl(debug, |d| {
+                if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
+                    if let Some(def_id) = ty_def.did().as_local() {
+                        impls.insert(def_id);
+                    }
+                }
+            });
+
+            self.impling_types = Some(impls);
+            debug!("{:?}", self.impling_types);
+        }
+
+        if !self.impling_types.as_ref().unwrap().contains(&item.def_id) {
+            cx.struct_span_lint(MISSING_DEBUG_IMPLEMENTATIONS, item.span, |lint| {
+                lint.build(fluent::lint::builtin_missing_debug_impl)
+                    .set_arg("debug", cx.tcx.def_path_str(debug))
+                    .emit();
+            });
+        }
+    }
+}
+
+declare_lint! {
+    /// The `anonymous_parameters` lint detects anonymous parameters in trait
+    /// definitions.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,edition2015,compile_fail
+    /// #![deny(anonymous_parameters)]
+    /// // edition 2015
+    /// pub trait Foo {
+    ///     fn foo(usize);
+    /// }
+    /// fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This syntax is mostly a historical accident, and can be worked around
+    /// quite easily by adding an `_` pattern or a descriptive identifier:
+    ///
+    /// ```rust
+    /// trait Foo {
+    ///     fn foo(_: usize);
+    /// }
+    /// ```
+    ///
+    /// This syntax is now a hard error in the 2018 edition. In the 2015
+    /// edition, this lint is "warn" by default. This lint
+    /// enables the [`cargo fix`] tool with the `--edition` flag to
+    /// automatically transition old code from the 2015 edition to 2018. The
+    /// tool will run this lint and automatically apply the
+    /// suggested fix from the compiler (which is to add `_` to each
+    /// parameter). This provides a completely automated way to update old
+    /// code for a new edition. See [issue #41686] for more details.
+    ///
+    /// [issue #41686]: https://github.com/rust-lang/rust/issues/41686
+    /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
+    pub ANONYMOUS_PARAMETERS,
+    Warn,
+    "detects anonymous parameters",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
+        reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
+    };
+}
+
+declare_lint_pass!(
+    /// Checks for use of anonymous parameters (RFC 1685).
+    AnonymousParameters => [ANONYMOUS_PARAMETERS]
+);
+
+impl EarlyLintPass for AnonymousParameters {
+    fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
+        if cx.sess().edition() != Edition::Edition2015 {
+            // This is a hard error in future editions; avoid linting and erroring
+            return;
+        }
+        if let ast::AssocItemKind::Fn(box Fn { ref sig, .. }) = it.kind {
+            for arg in sig.decl.inputs.iter() {
+                if let ast::PatKind::Ident(_, ident, None) = arg.pat.kind {
+                    if ident.name == kw::Empty {
+                        cx.struct_span_lint(ANONYMOUS_PARAMETERS, arg.pat.span, |lint| {
+                            let ty_snip = cx.sess().source_map().span_to_snippet(arg.ty.span);
+
+                            let (ty_snip, appl) = if let Ok(ref snip) = ty_snip {
+                                (snip.as_str(), Applicability::MachineApplicable)
+                            } else {
+                                ("<type>", Applicability::HasPlaceholders)
+                            };
+
+                            lint.build(fluent::lint::builtin_anonymous_params)
+                                .span_suggestion(
+                                    arg.pat.span,
+                                    fluent::lint::suggestion,
+                                    format!("_: {}", ty_snip),
+                                    appl,
+                                )
+                                .emit();
+                        })
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// Check for use of attributes which have been deprecated.
+#[derive(Clone)]
+pub struct DeprecatedAttr {
+    // This is not free to compute, so we want to keep it around, rather than
+    // compute it for every attribute.
+    depr_attrs: Vec<&'static BuiltinAttribute>,
+}
+
+impl_lint_pass!(DeprecatedAttr => []);
+
+impl DeprecatedAttr {
+    pub fn new() -> DeprecatedAttr {
+        DeprecatedAttr { depr_attrs: deprecated_attributes() }
+    }
+}
+
+impl EarlyLintPass for DeprecatedAttr {
+    fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
+        for BuiltinAttribute { name, gate, .. } in &self.depr_attrs {
+            if attr.ident().map(|ident| ident.name) == Some(*name) {
+                if let &AttributeGate::Gated(
+                    Stability::Deprecated(link, suggestion),
+                    name,
+                    reason,
+                    _,
+                ) = gate
+                {
+                    cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
+                        // FIXME(davidtwco) translatable deprecated attr
+                        lint.build(fluent::lint::builtin_deprecated_attr_link)
+                            .set_arg("name", name)
+                            .set_arg("reason", reason)
+                            .set_arg("link", link)
+                            .span_suggestion_short(
+                                attr.span,
+                                suggestion.map(|s| s.into()).unwrap_or(
+                                    fluent::lint::builtin_deprecated_attr_default_suggestion,
+                                ),
+                                "",
+                                Applicability::MachineApplicable,
+                            )
+                            .emit();
+                    });
+                }
+                return;
+            }
+        }
+        if attr.has_name(sym::no_start) || attr.has_name(sym::crate_id) {
+            cx.struct_span_lint(DEPRECATED, attr.span, |lint| {
+                lint.build(fluent::lint::builtin_deprecated_attr_used)
+                    .set_arg("name", pprust::path_to_string(&attr.get_normal_item().path))
+                    .span_suggestion_short(
+                        attr.span,
+                        fluent::lint::builtin_deprecated_attr_default_suggestion,
+                        "",
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+            });
+        }
+    }
+}
+
+fn warn_if_doc(cx: &EarlyContext<'_>, node_span: Span, node_kind: &str, attrs: &[ast::Attribute]) {
+    use rustc_ast::token::CommentKind;
+
+    let mut attrs = attrs.iter().peekable();
+
+    // Accumulate a single span for sugared doc comments.
+    let mut sugared_span: Option<Span> = None;
+
+    while let Some(attr) = attrs.next() {
+        let is_doc_comment = attr.is_doc_comment();
+        if is_doc_comment {
+            sugared_span =
+                Some(sugared_span.map_or(attr.span, |span| span.with_hi(attr.span.hi())));
+        }
+
+        if attrs.peek().map_or(false, |next_attr| next_attr.is_doc_comment()) {
+            continue;
+        }
+
+        let span = sugared_span.take().unwrap_or(attr.span);
+
+        if is_doc_comment || attr.has_name(sym::doc) {
+            cx.struct_span_lint(UNUSED_DOC_COMMENTS, span, |lint| {
+                let mut err = lint.build(fluent::lint::builtin_unused_doc_comment);
+                err.set_arg("kind", node_kind);
+                err.span_label(node_span, fluent::lint::label);
+                match attr.kind {
+                    AttrKind::DocComment(CommentKind::Line, _) | AttrKind::Normal(..) => {
+                        err.help(fluent::lint::plain_help);
+                    }
+                    AttrKind::DocComment(CommentKind::Block, _) => {
+                        err.help(fluent::lint::block_help);
+                    }
+                }
+                err.emit();
+            });
+        }
+    }
+}
+
+impl EarlyLintPass for UnusedDocComment {
+    fn check_stmt(&mut self, cx: &EarlyContext<'_>, stmt: &ast::Stmt) {
+        let kind = match stmt.kind {
+            ast::StmtKind::Local(..) => "statements",
+            // Disabled pending discussion in #78306
+            ast::StmtKind::Item(..) => return,
+            // expressions will be reported by `check_expr`.
+            ast::StmtKind::Empty
+            | ast::StmtKind::Semi(_)
+            | ast::StmtKind::Expr(_)
+            | ast::StmtKind::MacCall(_) => return,
+        };
+
+        warn_if_doc(cx, stmt.span, kind, stmt.kind.attrs());
+    }
+
+    fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
+        let arm_span = arm.pat.span.with_hi(arm.body.span.hi());
+        warn_if_doc(cx, arm_span, "match arms", &arm.attrs);
+    }
+
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
+        warn_if_doc(cx, expr.span, "expressions", &expr.attrs);
+    }
+
+    fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
+        warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
+    }
+
+    fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
+        warn_if_doc(cx, block.span, "blocks", &block.attrs());
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        if let ast::ItemKind::ForeignMod(_) = item.kind {
+            warn_if_doc(cx, item.span, "extern blocks", &item.attrs);
+        }
+    }
+}
+
+declare_lint! {
+    /// The `no_mangle_const_items` lint detects any `const` items with the
+    /// [`no_mangle` attribute].
+    ///
+    /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #[no_mangle]
+    /// const FOO: i32 = 5;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Constants do not have their symbols exported, and therefore, this
+    /// probably means you meant to use a [`static`], not a [`const`].
+    ///
+    /// [`static`]: https://doc.rust-lang.org/reference/items/static-items.html
+    /// [`const`]: https://doc.rust-lang.org/reference/items/constant-items.html
+    NO_MANGLE_CONST_ITEMS,
+    Deny,
+    "const items will not have their symbols exported"
+}
+
+declare_lint! {
+    /// The `no_mangle_generic_items` lint detects generic items that must be
+    /// mangled.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #[no_mangle]
+    /// fn foo<T>(t: T) {
+    ///
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// A function with generics must have its symbol mangled to accommodate
+    /// the generic parameter. The [`no_mangle` attribute] has no effect in
+    /// this situation, and should be removed.
+    ///
+    /// [`no_mangle` attribute]: https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute
+    NO_MANGLE_GENERIC_ITEMS,
+    Warn,
+    "generic items must be mangled"
+}
+
+declare_lint_pass!(InvalidNoMangleItems => [NO_MANGLE_CONST_ITEMS, NO_MANGLE_GENERIC_ITEMS]);
+
+impl<'tcx> LateLintPass<'tcx> for InvalidNoMangleItems {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        let attrs = cx.tcx.hir().attrs(it.hir_id());
+        let check_no_mangle_on_generic_fn = |no_mangle_attr: &ast::Attribute,
+                                             impl_generics: Option<&hir::Generics<'_>>,
+                                             generics: &hir::Generics<'_>,
+                                             span| {
+            for param in
+                generics.params.iter().chain(impl_generics.map(|g| g.params).into_iter().flatten())
+            {
+                match param.kind {
+                    GenericParamKind::Lifetime { .. } => {}
+                    GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
+                        cx.struct_span_lint(NO_MANGLE_GENERIC_ITEMS, span, |lint| {
+                            lint.build(fluent::lint::builtin_no_mangle_generic)
+                                .span_suggestion_short(
+                                    no_mangle_attr.span,
+                                    fluent::lint::suggestion,
+                                    "",
+                                    // Use of `#[no_mangle]` suggests FFI intent; correct
+                                    // fix may be to monomorphize source by hand
+                                    Applicability::MaybeIncorrect,
+                                )
+                                .emit();
+                        });
+                        break;
+                    }
+                }
+            }
+        };
+        match it.kind {
+            hir::ItemKind::Fn(.., ref generics, _) => {
+                if let Some(no_mangle_attr) = cx.sess().find_by_name(attrs, sym::no_mangle) {
+                    check_no_mangle_on_generic_fn(no_mangle_attr, None, generics, it.span);
+                }
+            }
+            hir::ItemKind::Const(..) => {
+                if cx.sess().contains_name(attrs, sym::no_mangle) {
+                    // Const items do not refer to a particular location in memory, and therefore
+                    // don't have anything to attach a symbol to
+                    cx.struct_span_lint(NO_MANGLE_CONST_ITEMS, it.span, |lint| {
+                        let mut err = lint.build(fluent::lint::builtin_const_no_mangle);
+
+                        // account for "pub const" (#45562)
+                        let start = cx
+                            .tcx
+                            .sess
+                            .source_map()
+                            .span_to_snippet(it.span)
+                            .map(|snippet| snippet.find("const").unwrap_or(0))
+                            .unwrap_or(0) as u32;
+                        // `const` is 5 chars
+                        let const_span = it.span.with_hi(BytePos(it.span.lo().0 + start + 5));
+                        err.span_suggestion(
+                            const_span,
+                            fluent::lint::suggestion,
+                            "pub static",
+                            Applicability::MachineApplicable,
+                        );
+                        err.emit();
+                    });
+                }
+            }
+            hir::ItemKind::Impl(hir::Impl { generics, items, .. }) => {
+                for it in *items {
+                    if let hir::AssocItemKind::Fn { .. } = it.kind {
+                        if let Some(no_mangle_attr) = cx
+                            .sess()
+                            .find_by_name(cx.tcx.hir().attrs(it.id.hir_id()), sym::no_mangle)
+                        {
+                            check_no_mangle_on_generic_fn(
+                                no_mangle_attr,
+                                Some(generics),
+                                cx.tcx.hir().get_generics(it.id.def_id).unwrap(),
+                                it.span,
+                            );
+                        }
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+declare_lint! {
+    /// The `mutable_transmutes` lint catches transmuting from `&T` to `&mut
+    /// T` because it is [undefined behavior].
+    ///
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// unsafe {
+    ///     let y = std::mem::transmute::<&i32, &mut i32>(&5);
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Certain assumptions are made about aliasing of data, and this transmute
+    /// violates those assumptions. Consider using [`UnsafeCell`] instead.
+    ///
+    /// [`UnsafeCell`]: https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html
+    MUTABLE_TRANSMUTES,
+    Deny,
+    "transmuting &T to &mut T is undefined behavior, even if the reference is unused"
+}
+
+declare_lint_pass!(MutableTransmutes => [MUTABLE_TRANSMUTES]);
+
+impl<'tcx> LateLintPass<'tcx> for MutableTransmutes {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        if let Some((&ty::Ref(_, _, from_mt), &ty::Ref(_, _, to_mt))) =
+            get_transmute_from_to(cx, expr).map(|(ty1, ty2)| (ty1.kind(), ty2.kind()))
+        {
+            if to_mt == hir::Mutability::Mut && from_mt == hir::Mutability::Not {
+                cx.struct_span_lint(MUTABLE_TRANSMUTES, expr.span, |lint| {
+                    lint.build(fluent::lint::builtin_mutable_transmutes).emit();
+                });
+            }
+        }
+
+        fn get_transmute_from_to<'tcx>(
+            cx: &LateContext<'tcx>,
+            expr: &hir::Expr<'_>,
+        ) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
+            let def = if let hir::ExprKind::Path(ref qpath) = expr.kind {
+                cx.qpath_res(qpath, expr.hir_id)
+            } else {
+                return None;
+            };
+            if let Res::Def(DefKind::Fn, did) = def {
+                if !def_id_is_transmute(cx, did) {
+                    return None;
+                }
+                let sig = cx.typeck_results().node_type(expr.hir_id).fn_sig(cx.tcx);
+                let from = sig.inputs().skip_binder()[0];
+                let to = sig.output().skip_binder();
+                return Some((from, to));
+            }
+            None
+        }
+
+        fn def_id_is_transmute(cx: &LateContext<'_>, def_id: DefId) -> bool {
+            cx.tcx.is_intrinsic(def_id) && cx.tcx.item_name(def_id) == sym::transmute
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unstable_features` is deprecated and should no longer be used.
+    UNSTABLE_FEATURES,
+    Allow,
+    "enabling unstable features (deprecated. do not use)"
+}
+
+declare_lint_pass!(
+    /// Forbids using the `#[feature(...)]` attribute
+    UnstableFeatures => [UNSTABLE_FEATURES]
+);
+
+impl<'tcx> LateLintPass<'tcx> for UnstableFeatures {
+    fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
+        if attr.has_name(sym::feature) {
+            if let Some(items) = attr.meta_item_list() {
+                for item in items {
+                    cx.struct_span_lint(UNSTABLE_FEATURES, item.span(), |lint| {
+                        lint.build(fluent::lint::builtin_unstable_features).emit();
+                    });
+                }
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unreachable_pub` lint triggers for `pub` items not reachable from
+    /// the crate root.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(unreachable_pub)]
+    /// mod foo {
+    ///     pub mod bar {
+    ///
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// A bare `pub` visibility may be misleading if the item is not actually
+    /// publicly exported from the crate. The `pub(crate)` visibility is
+    /// recommended to be used instead, which more clearly expresses the intent
+    /// that the item is only visible within its own crate.
+    ///
+    /// This lint is "allow" by default because it will trigger for a large
+    /// amount existing Rust code, and has some false-positives. Eventually it
+    /// is desired for this to become warn-by-default.
+    pub UNREACHABLE_PUB,
+    Allow,
+    "`pub` items not reachable from crate root"
+}
+
+declare_lint_pass!(
+    /// Lint for items marked `pub` that aren't reachable from other crates.
+    UnreachablePub => [UNREACHABLE_PUB]
+);
+
+impl UnreachablePub {
+    fn perform_lint(
+        &self,
+        cx: &LateContext<'_>,
+        what: &str,
+        def_id: LocalDefId,
+        vis_span: Span,
+        exportable: bool,
+    ) {
+        let mut applicability = Applicability::MachineApplicable;
+        if cx.tcx.visibility(def_id).is_public() && !cx.access_levels.is_reachable(def_id) {
+            if vis_span.from_expansion() {
+                applicability = Applicability::MaybeIncorrect;
+            }
+            let def_span = cx.tcx.def_span(def_id);
+            cx.struct_span_lint(UNREACHABLE_PUB, def_span, |lint| {
+                let mut err = lint.build(fluent::lint::builtin_unreachable_pub);
+                err.set_arg("what", what);
+
+                err.span_suggestion(
+                    vis_span,
+                    fluent::lint::suggestion,
+                    "pub(crate)",
+                    applicability,
+                );
+                if exportable {
+                    err.help(fluent::lint::help);
+                }
+                err.emit();
+            });
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
+        // Do not warn for fake `use` statements.
+        if let hir::ItemKind::Use(_, hir::UseKind::ListStem) = &item.kind {
+            return;
+        }
+        self.perform_lint(cx, "item", item.def_id, item.vis_span, true);
+    }
+
+    fn check_foreign_item(&mut self, cx: &LateContext<'_>, foreign_item: &hir::ForeignItem<'tcx>) {
+        self.perform_lint(cx, "item", foreign_item.def_id, foreign_item.vis_span, true);
+    }
+
+    fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
+        let def_id = cx.tcx.hir().local_def_id(field.hir_id);
+        self.perform_lint(cx, "field", def_id, field.vis_span, false);
+    }
+
+    fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &hir::ImplItem<'_>) {
+        // Only lint inherent impl items.
+        if cx.tcx.associated_item(impl_item.def_id).trait_item_def_id.is_none() {
+            self.perform_lint(cx, "item", impl_item.def_id, impl_item.vis_span, false);
+        }
+    }
+}
+
+declare_lint! {
+    /// The `type_alias_bounds` lint detects bounds in type aliases.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// type SendVec<T: Send> = Vec<T>;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The trait bounds in a type alias are currently ignored, and should not
+    /// be included to avoid confusion. This was previously allowed
+    /// unintentionally; this may become a hard error in the future.
+    TYPE_ALIAS_BOUNDS,
+    Warn,
+    "bounds in type aliases are not enforced"
+}
+
+declare_lint_pass!(
+    /// Lint for trait and lifetime bounds in type aliases being mostly ignored.
+    /// They are relevant when using associated types, but otherwise neither checked
+    /// at definition site nor enforced at use site.
+    TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
+);
+
+impl TypeAliasBounds {
+    fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
+        match *qpath {
+            hir::QPath::TypeRelative(ref ty, _) => {
+                // If this is a type variable, we found a `T::Assoc`.
+                match ty.kind {
+                    hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
+                        matches!(path.res, Res::Def(DefKind::TyParam, _))
+                    }
+                    _ => false,
+                }
+            }
+            hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
+        }
+    }
+
+    fn suggest_changing_assoc_types(ty: &hir::Ty<'_>, err: &mut Diagnostic) {
+        // Access to associates types should use `<T as Bound>::Assoc`, which does not need a
+        // bound.  Let's see if this type does that.
+
+        // We use a HIR visitor to walk the type.
+        use rustc_hir::intravisit::{self, Visitor};
+        struct WalkAssocTypes<'a> {
+            err: &'a mut Diagnostic,
+        }
+        impl Visitor<'_> for WalkAssocTypes<'_> {
+            fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) {
+                if TypeAliasBounds::is_type_variable_assoc(qpath) {
+                    self.err.span_help(span, fluent::lint::builtin_type_alias_bounds_help);
+                }
+                intravisit::walk_qpath(self, qpath, id, span)
+            }
+        }
+
+        // Let's go for a walk!
+        let mut visitor = WalkAssocTypes { err };
+        visitor.visit_ty(ty);
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
+        let hir::ItemKind::TyAlias(ty, type_alias_generics) = &item.kind else {
+            return
+        };
+        if let hir::TyKind::OpaqueDef(..) = ty.kind {
+            // Bounds are respected for `type X = impl Trait`
+            return;
+        }
+        // There must not be a where clause
+        if type_alias_generics.predicates.is_empty() {
+            return;
+        }
+
+        let mut where_spans = Vec::new();
+        let mut inline_spans = Vec::new();
+        let mut inline_sugg = Vec::new();
+        for p in type_alias_generics.predicates {
+            let span = p.span();
+            if p.in_where_clause() {
+                where_spans.push(span);
+            } else {
+                for b in p.bounds() {
+                    inline_spans.push(b.span());
+                }
+                inline_sugg.push((span, String::new()));
+            }
+        }
+
+        let mut suggested_changing_assoc_types = false;
+        if !where_spans.is_empty() {
+            cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
+                let mut err = lint.build(fluent::lint::builtin_type_alias_where_clause);
+                err.set_span(where_spans);
+                err.span_suggestion(
+                    type_alias_generics.where_clause_span,
+                    fluent::lint::suggestion,
+                    "",
+                    Applicability::MachineApplicable,
+                );
+                if !suggested_changing_assoc_types {
+                    TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
+                    suggested_changing_assoc_types = true;
+                }
+                err.emit();
+            });
+        }
+
+        if !inline_spans.is_empty() {
+            cx.lint(TYPE_ALIAS_BOUNDS, |lint| {
+                let mut err = lint.build(fluent::lint::builtin_type_alias_generic_bounds);
+                err.set_span(inline_spans);
+                err.multipart_suggestion(
+                    fluent::lint::suggestion,
+                    inline_sugg,
+                    Applicability::MachineApplicable,
+                );
+                if !suggested_changing_assoc_types {
+                    TypeAliasBounds::suggest_changing_assoc_types(ty, &mut err);
+                }
+                err.emit();
+            });
+        }
+    }
+}
+
+declare_lint_pass!(
+    /// Lint constants that are erroneous.
+    /// Without this lint, we might not get any diagnostic if the constant is
+    /// unused within this crate, even though downstream crates can't use it
+    /// without producing an error.
+    UnusedBrokenConst => []
+);
+
+impl<'tcx> LateLintPass<'tcx> for UnusedBrokenConst {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        match it.kind {
+            hir::ItemKind::Const(_, body_id) => {
+                let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
+                // trigger the query once for all constants since that will already report the errors
+                cx.tcx.ensure().const_eval_poly(def_id);
+            }
+            hir::ItemKind::Static(_, _, body_id) => {
+                let def_id = cx.tcx.hir().body_owner_def_id(body_id).to_def_id();
+                cx.tcx.ensure().eval_static_initializer(def_id);
+            }
+            _ => {}
+        }
+    }
+}
+
+declare_lint! {
+    /// The `trivial_bounds` lint detects trait bounds that don't depend on
+    /// any type parameters.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(trivial_bounds)]
+    /// pub struct A where i32: Copy;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Usually you would not write a trait bound that you know is always
+    /// true, or never true. However, when using macros, the macro may not
+    /// know whether or not the constraint would hold or not at the time when
+    /// generating the code. Currently, the compiler does not alert you if the
+    /// constraint is always true, and generates an error if it is never true.
+    /// The `trivial_bounds` feature changes this to be a warning in both
+    /// cases, giving macros more freedom and flexibility to generate code,
+    /// while still providing a signal when writing non-macro code that
+    /// something is amiss.
+    ///
+    /// See [RFC 2056] for more details. This feature is currently only
+    /// available on the nightly channel, see [tracking issue #48214].
+    ///
+    /// [RFC 2056]: https://github.com/rust-lang/rfcs/blob/master/text/2056-allow-trivial-where-clause-constraints.md
+    /// [tracking issue #48214]: https://github.com/rust-lang/rust/issues/48214
+    TRIVIAL_BOUNDS,
+    Warn,
+    "these bounds don't depend on an type parameters"
+}
+
+declare_lint_pass!(
+    /// Lint for trait and lifetime bounds that don't depend on type parameters
+    /// which either do nothing, or stop the item from being used.
+    TrivialConstraints => [TRIVIAL_BOUNDS]
+);
+
+impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
+        use rustc_middle::ty::visit::TypeVisitable;
+        use rustc_middle::ty::PredicateKind::*;
+
+        if cx.tcx.features().trivial_bounds {
+            let predicates = cx.tcx.predicates_of(item.def_id);
+            for &(predicate, span) in predicates.predicates {
+                let predicate_kind_name = match predicate.kind().skip_binder() {
+                    Trait(..) => "trait",
+                    TypeOutlives(..) |
+                    RegionOutlives(..) => "lifetime",
+
+                    // Ignore projections, as they can only be global
+                    // if the trait bound is global
+                    Projection(..) |
+                    // Ignore bounds that a user can't type
+                    WellFormed(..) |
+                    ObjectSafe(..) |
+                    ClosureKind(..) |
+                    Subtype(..) |
+                    Coerce(..) |
+                    ConstEvaluatable(..) |
+                    ConstEquate(..) |
+                    TypeWellFormedFromEnv(..) => continue,
+                };
+                if predicate.is_global() {
+                    cx.struct_span_lint(TRIVIAL_BOUNDS, span, |lint| {
+                        lint.build(fluent::lint::builtin_trivial_bounds)
+                            .set_arg("predicate_kind_name", predicate_kind_name)
+                            .set_arg("predicate", predicate)
+                            .emit();
+                    });
+                }
+            }
+        }
+    }
+}
+
+declare_lint_pass!(
+    /// Does nothing as a lint pass, but registers some `Lint`s
+    /// which are used by other parts of the compiler.
+    SoftLints => [
+        WHILE_TRUE,
+        BOX_POINTERS,
+        NON_SHORTHAND_FIELD_PATTERNS,
+        UNSAFE_CODE,
+        MISSING_DOCS,
+        MISSING_COPY_IMPLEMENTATIONS,
+        MISSING_DEBUG_IMPLEMENTATIONS,
+        ANONYMOUS_PARAMETERS,
+        UNUSED_DOC_COMMENTS,
+        NO_MANGLE_CONST_ITEMS,
+        NO_MANGLE_GENERIC_ITEMS,
+        MUTABLE_TRANSMUTES,
+        UNSTABLE_FEATURES,
+        UNREACHABLE_PUB,
+        TYPE_ALIAS_BOUNDS,
+        TRIVIAL_BOUNDS
+    ]
+);
+
+declare_lint! {
+    /// The `ellipsis_inclusive_range_patterns` lint detects the [`...` range
+    /// pattern], which is deprecated.
+    ///
+    /// [`...` range pattern]: https://doc.rust-lang.org/reference/patterns.html#range-patterns
+    ///
+    /// ### Example
+    ///
+    /// ```rust,edition2018
+    /// let x = 123;
+    /// match x {
+    ///     0...100 => {}
+    ///     _ => {}
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The `...` range pattern syntax was changed to `..=` to avoid potential
+    /// confusion with the [`..` range expression]. Use the new form instead.
+    ///
+    /// [`..` range expression]: https://doc.rust-lang.org/reference/expressions/range-expr.html
+    pub ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
+    Warn,
+    "`...` range patterns are deprecated",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
+        reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
+    };
+}
+
+#[derive(Default)]
+pub struct EllipsisInclusiveRangePatterns {
+    /// If `Some(_)`, suppress all subsequent pattern
+    /// warnings for better diagnostics.
+    node_id: Option<ast::NodeId>,
+}
+
+impl_lint_pass!(EllipsisInclusiveRangePatterns => [ELLIPSIS_INCLUSIVE_RANGE_PATTERNS]);
+
+impl EarlyLintPass for EllipsisInclusiveRangePatterns {
+    fn check_pat(&mut self, cx: &EarlyContext<'_>, pat: &ast::Pat) {
+        if self.node_id.is_some() {
+            // Don't recursively warn about patterns inside range endpoints.
+            return;
+        }
+
+        use self::ast::{PatKind, RangeSyntax::DotDotDot};
+
+        /// If `pat` is a `...` pattern, return the start and end of the range, as well as the span
+        /// corresponding to the ellipsis.
+        fn matches_ellipsis_pat(pat: &ast::Pat) -> Option<(Option<&Expr>, &Expr, Span)> {
+            match &pat.kind {
+                PatKind::Range(
+                    a,
+                    Some(b),
+                    Spanned { span, node: RangeEnd::Included(DotDotDot) },
+                ) => Some((a.as_deref(), b, *span)),
+                _ => None,
+            }
+        }
+
+        let (parenthesise, endpoints) = match &pat.kind {
+            PatKind::Ref(subpat, _) => (true, matches_ellipsis_pat(&subpat)),
+            _ => (false, matches_ellipsis_pat(pat)),
+        };
+
+        if let Some((start, end, join)) = endpoints {
+            let msg = fluent::lint::builtin_ellipsis_inclusive_range_patterns;
+            let suggestion = fluent::lint::suggestion;
+            if parenthesise {
+                self.node_id = Some(pat.id);
+                let end = expr_to_string(&end);
+                let replace = match start {
+                    Some(start) => format!("&({}..={})", expr_to_string(&start), end),
+                    None => format!("&(..={})", end),
+                };
+                if join.edition() >= Edition::Edition2021 {
+                    let mut err = cx.sess().struct_span_err_with_code(
+                        pat.span,
+                        msg,
+                        rustc_errors::error_code!(E0783),
+                    );
+                    err.span_suggestion(
+                        pat.span,
+                        suggestion,
+                        replace,
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+                } else {
+                    cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, pat.span, |lint| {
+                        lint.build(msg)
+                            .span_suggestion(
+                                pat.span,
+                                suggestion,
+                                replace,
+                                Applicability::MachineApplicable,
+                            )
+                            .emit();
+                    });
+                }
+            } else {
+                let replace = "..=";
+                if join.edition() >= Edition::Edition2021 {
+                    let mut err = cx.sess().struct_span_err_with_code(
+                        pat.span,
+                        msg,
+                        rustc_errors::error_code!(E0783),
+                    );
+                    err.span_suggestion_short(
+                        join,
+                        suggestion,
+                        replace,
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+                } else {
+                    cx.struct_span_lint(ELLIPSIS_INCLUSIVE_RANGE_PATTERNS, join, |lint| {
+                        lint.build(msg)
+                            .span_suggestion_short(
+                                join,
+                                suggestion,
+                                replace,
+                                Applicability::MachineApplicable,
+                            )
+                            .emit();
+                    });
+                }
+            };
+        }
+    }
+
+    fn check_pat_post(&mut self, _cx: &EarlyContext<'_>, pat: &ast::Pat) {
+        if let Some(node_id) = self.node_id {
+            if pat.id == node_id {
+                self.node_id = None
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unnameable_test_items` lint detects [`#[test]`][test] functions
+    /// that are not able to be run by the test harness because they are in a
+    /// position where they are not nameable.
+    ///
+    /// [test]: https://doc.rust-lang.org/reference/attributes/testing.html#the-test-attribute
+    ///
+    /// ### Example
+    ///
+    /// ```rust,test
+    /// fn main() {
+    ///     #[test]
+    ///     fn foo() {
+    ///         // This test will not fail because it does not run.
+    ///         assert_eq!(1, 2);
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In order for the test harness to run a test, the test function must be
+    /// located in a position where it can be accessed from the crate root.
+    /// This generally means it must be defined in a module, and not anywhere
+    /// else such as inside another function. The compiler previously allowed
+    /// this without an error, so a lint was added as an alert that a test is
+    /// not being used. Whether or not this should be allowed has not yet been
+    /// decided, see [RFC 2471] and [issue #36629].
+    ///
+    /// [RFC 2471]: https://github.com/rust-lang/rfcs/pull/2471#issuecomment-397414443
+    /// [issue #36629]: https://github.com/rust-lang/rust/issues/36629
+    UNNAMEABLE_TEST_ITEMS,
+    Warn,
+    "detects an item that cannot be named being marked as `#[test_case]`",
+    report_in_external_macro
+}
+
+pub struct UnnameableTestItems {
+    boundary: Option<LocalDefId>, // Id of the item under which things are not nameable
+    items_nameable: bool,
+}
+
+impl_lint_pass!(UnnameableTestItems => [UNNAMEABLE_TEST_ITEMS]);
+
+impl UnnameableTestItems {
+    pub fn new() -> Self {
+        Self { boundary: None, items_nameable: true }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for UnnameableTestItems {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        if self.items_nameable {
+            if let hir::ItemKind::Mod(..) = it.kind {
+            } else {
+                self.items_nameable = false;
+                self.boundary = Some(it.def_id);
+            }
+            return;
+        }
+
+        let attrs = cx.tcx.hir().attrs(it.hir_id());
+        if let Some(attr) = cx.sess().find_by_name(attrs, sym::rustc_test_marker) {
+            cx.struct_span_lint(UNNAMEABLE_TEST_ITEMS, attr.span, |lint| {
+                lint.build(fluent::lint::builtin_unnameable_test_items).emit();
+            });
+        }
+    }
+
+    fn check_item_post(&mut self, _cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        if !self.items_nameable && self.boundary == Some(it.def_id) {
+            self.items_nameable = true;
+        }
+    }
+}
+
+declare_lint! {
+    /// The `keyword_idents` lint detects edition keywords being used as an
+    /// identifier.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,edition2015,compile_fail
+    /// #![deny(keyword_idents)]
+    /// // edition 2015
+    /// fn dyn() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Rust [editions] allow the language to evolve without breaking
+    /// backwards compatibility. This lint catches code that uses new keywords
+    /// that are added to the language that are used as identifiers (such as a
+    /// variable name, function name, etc.). If you switch the compiler to a
+    /// new edition without updating the code, then it will fail to compile if
+    /// you are using a new keyword as an identifier.
+    ///
+    /// You can manually change the identifiers to a non-keyword, or use a
+    /// [raw identifier], for example `r#dyn`, to transition to a new edition.
+    ///
+    /// This lint solves the problem automatically. It is "allow" by default
+    /// because the code is perfectly valid in older editions. The [`cargo
+    /// fix`] tool with the `--edition` flag will switch this lint to "warn"
+    /// and automatically apply the suggested fix from the compiler (which is
+    /// to use a raw identifier). This provides a completely automated way to
+    /// update old code for a new edition.
+    ///
+    /// [editions]: https://doc.rust-lang.org/edition-guide/
+    /// [raw identifier]: https://doc.rust-lang.org/reference/identifiers.html
+    /// [`cargo fix`]: https://doc.rust-lang.org/cargo/commands/cargo-fix.html
+    pub KEYWORD_IDENTS,
+    Allow,
+    "detects edition keywords being used as an identifier",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
+        reason: FutureIncompatibilityReason::EditionError(Edition::Edition2018),
+    };
+}
+
+declare_lint_pass!(
+    /// Check for uses of edition keywords used as an identifier.
+    KeywordIdents => [KEYWORD_IDENTS]
+);
+
+struct UnderMacro(bool);
+
+impl KeywordIdents {
+    fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
+        for tt in tokens.into_trees() {
+            match tt {
+                // Only report non-raw idents.
+                TokenTree::Token(token, _) => {
+                    if let Some((ident, false)) = token.ident() {
+                        self.check_ident_token(cx, UnderMacro(true), ident);
+                    }
+                }
+                TokenTree::Delimited(_, _, tts) => self.check_tokens(cx, tts),
+            }
+        }
+    }
+
+    fn check_ident_token(
+        &mut self,
+        cx: &EarlyContext<'_>,
+        UnderMacro(under_macro): UnderMacro,
+        ident: Ident,
+    ) {
+        let next_edition = match cx.sess().edition() {
+            Edition::Edition2015 => {
+                match ident.name {
+                    kw::Async | kw::Await | kw::Try => Edition::Edition2018,
+
+                    // rust-lang/rust#56327: Conservatively do not
+                    // attempt to report occurrences of `dyn` within
+                    // macro definitions or invocations, because `dyn`
+                    // can legitimately occur as a contextual keyword
+                    // in 2015 code denoting its 2018 meaning, and we
+                    // do not want rustfix to inject bugs into working
+                    // code by rewriting such occurrences.
+                    //
+                    // But if we see `dyn` outside of a macro, we know
+                    // its precise role in the parsed AST and thus are
+                    // assured this is truly an attempt to use it as
+                    // an identifier.
+                    kw::Dyn if !under_macro => Edition::Edition2018,
+
+                    _ => return,
+                }
+            }
+
+            // There are no new keywords yet for the 2018 edition and beyond.
+            _ => return,
+        };
+
+        // Don't lint `r#foo`.
+        if cx.sess().parse_sess.raw_identifier_spans.borrow().contains(&ident.span) {
+            return;
+        }
+
+        cx.struct_span_lint(KEYWORD_IDENTS, ident.span, |lint| {
+            lint.build(fluent::lint::builtin_keyword_idents)
+                .set_arg("kw", ident.clone())
+                .set_arg("next", next_edition)
+                .span_suggestion(
+                    ident.span,
+                    fluent::lint::suggestion,
+                    format!("r#{}", ident),
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        });
+    }
+}
+
+impl EarlyLintPass for KeywordIdents {
+    fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef, _id: ast::NodeId) {
+        self.check_tokens(cx, mac_def.body.inner_tokens());
+    }
+    fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
+        self.check_tokens(cx, mac.args.inner_tokens());
+    }
+    fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
+        self.check_ident_token(cx, UnderMacro(false), ident);
+    }
+}
+
+declare_lint_pass!(ExplicitOutlivesRequirements => [EXPLICIT_OUTLIVES_REQUIREMENTS]);
+
+impl ExplicitOutlivesRequirements {
+    fn lifetimes_outliving_lifetime<'tcx>(
+        inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
+        index: u32,
+    ) -> Vec<ty::Region<'tcx>> {
+        inferred_outlives
+            .iter()
+            .filter_map(|(pred, _)| match pred.kind().skip_binder() {
+                ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(a, b)) => match *a {
+                    ty::ReEarlyBound(ebr) if ebr.index == index => Some(b),
+                    _ => None,
+                },
+                _ => None,
+            })
+            .collect()
+    }
+
+    fn lifetimes_outliving_type<'tcx>(
+        inferred_outlives: &'tcx [(ty::Predicate<'tcx>, Span)],
+        index: u32,
+    ) -> Vec<ty::Region<'tcx>> {
+        inferred_outlives
+            .iter()
+            .filter_map(|(pred, _)| match pred.kind().skip_binder() {
+                ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(a, b)) => {
+                    a.is_param(index).then_some(b)
+                }
+                _ => None,
+            })
+            .collect()
+    }
+
+    fn collect_outlives_bound_spans<'tcx>(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        bounds: &hir::GenericBounds<'_>,
+        inferred_outlives: &[ty::Region<'tcx>],
+    ) -> Vec<(usize, Span)> {
+        use rustc_middle::middle::resolve_lifetime::Region;
+
+        bounds
+            .iter()
+            .enumerate()
+            .filter_map(|(i, bound)| {
+                if let hir::GenericBound::Outlives(lifetime) = bound {
+                    let is_inferred = match tcx.named_region(lifetime.hir_id) {
+                        Some(Region::EarlyBound(index, ..)) => inferred_outlives.iter().any(|r| {
+                            if let ty::ReEarlyBound(ebr) = **r { ebr.index == index } else { false }
+                        }),
+                        _ => false,
+                    };
+                    is_inferred.then_some((i, bound.span()))
+                } else {
+                    None
+                }
+            })
+            .filter(|(_, span)| !in_external_macro(tcx.sess, *span))
+            .collect()
+    }
+
+    fn consolidate_outlives_bound_spans(
+        &self,
+        lo: Span,
+        bounds: &hir::GenericBounds<'_>,
+        bound_spans: Vec<(usize, Span)>,
+    ) -> Vec<Span> {
+        if bounds.is_empty() {
+            return Vec::new();
+        }
+        if bound_spans.len() == bounds.len() {
+            let (_, last_bound_span) = bound_spans[bound_spans.len() - 1];
+            // If all bounds are inferable, we want to delete the colon, so
+            // start from just after the parameter (span passed as argument)
+            vec![lo.to(last_bound_span)]
+        } else {
+            let mut merged = Vec::new();
+            let mut last_merged_i = None;
+
+            let mut from_start = true;
+            for (i, bound_span) in bound_spans {
+                match last_merged_i {
+                    // If the first bound is inferable, our span should also eat the leading `+`.
+                    None if i == 0 => {
+                        merged.push(bound_span.to(bounds[1].span().shrink_to_lo()));
+                        last_merged_i = Some(0);
+                    }
+                    // If consecutive bounds are inferable, merge their spans
+                    Some(h) if i == h + 1 => {
+                        if let Some(tail) = merged.last_mut() {
+                            // Also eat the trailing `+` if the first
+                            // more-than-one bound is inferable
+                            let to_span = if from_start && i < bounds.len() {
+                                bounds[i + 1].span().shrink_to_lo()
+                            } else {
+                                bound_span
+                            };
+                            *tail = tail.to(to_span);
+                            last_merged_i = Some(i);
+                        } else {
+                            bug!("another bound-span visited earlier");
+                        }
+                    }
+                    _ => {
+                        // When we find a non-inferable bound, subsequent inferable bounds
+                        // won't be consecutive from the start (and we'll eat the leading
+                        // `+` rather than the trailing one)
+                        from_start = false;
+                        merged.push(bounds[i - 1].span().shrink_to_hi().to(bound_span));
+                        last_merged_i = Some(i);
+                    }
+                }
+            }
+            merged
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for ExplicitOutlivesRequirements {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
+        use rustc_middle::middle::resolve_lifetime::Region;
+
+        let def_id = item.def_id;
+        if let hir::ItemKind::Struct(_, ref hir_generics)
+        | hir::ItemKind::Enum(_, ref hir_generics)
+        | hir::ItemKind::Union(_, ref hir_generics) = item.kind
+        {
+            let inferred_outlives = cx.tcx.inferred_outlives_of(def_id);
+            if inferred_outlives.is_empty() {
+                return;
+            }
+
+            let ty_generics = cx.tcx.generics_of(def_id);
+
+            let mut bound_count = 0;
+            let mut lint_spans = Vec::new();
+            let mut where_lint_spans = Vec::new();
+            let mut dropped_predicate_count = 0;
+            let num_predicates = hir_generics.predicates.len();
+            for (i, where_predicate) in hir_generics.predicates.iter().enumerate() {
+                let (relevant_lifetimes, bounds, span, in_where_clause) = match where_predicate {
+                    hir::WherePredicate::RegionPredicate(predicate) => {
+                        if let Some(Region::EarlyBound(index, ..)) =
+                            cx.tcx.named_region(predicate.lifetime.hir_id)
+                        {
+                            (
+                                Self::lifetimes_outliving_lifetime(inferred_outlives, index),
+                                &predicate.bounds,
+                                predicate.span,
+                                predicate.in_where_clause,
+                            )
+                        } else {
+                            continue;
+                        }
+                    }
+                    hir::WherePredicate::BoundPredicate(predicate) => {
+                        // FIXME we can also infer bounds on associated types,
+                        // and should check for them here.
+                        match predicate.bounded_ty.kind {
+                            hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
+                                let Res::Def(DefKind::TyParam, def_id) = path.res else {
+                                    continue
+                                };
+                                let index = ty_generics.param_def_id_to_index[&def_id];
+                                (
+                                    Self::lifetimes_outliving_type(inferred_outlives, index),
+                                    &predicate.bounds,
+                                    predicate.span,
+                                    predicate.origin == PredicateOrigin::WhereClause,
+                                )
+                            }
+                            _ => {
+                                continue;
+                            }
+                        }
+                    }
+                    _ => continue,
+                };
+                if relevant_lifetimes.is_empty() {
+                    continue;
+                }
+
+                let bound_spans =
+                    self.collect_outlives_bound_spans(cx.tcx, bounds, &relevant_lifetimes);
+                bound_count += bound_spans.len();
+
+                let drop_predicate = bound_spans.len() == bounds.len();
+                if drop_predicate {
+                    dropped_predicate_count += 1;
+                }
+
+                if drop_predicate && !in_where_clause {
+                    lint_spans.push(span);
+                } else if drop_predicate && i + 1 < num_predicates {
+                    // If all the bounds on a predicate were inferable and there are
+                    // further predicates, we want to eat the trailing comma.
+                    let next_predicate_span = hir_generics.predicates[i + 1].span();
+                    where_lint_spans.push(span.to(next_predicate_span.shrink_to_lo()));
+                } else {
+                    where_lint_spans.extend(self.consolidate_outlives_bound_spans(
+                        span.shrink_to_lo(),
+                        bounds,
+                        bound_spans,
+                    ));
+                }
+            }
+
+            // If all predicates are inferable, drop the entire clause
+            // (including the `where`)
+            if hir_generics.has_where_clause_predicates && dropped_predicate_count == num_predicates
+            {
+                let where_span = hir_generics.where_clause_span;
+                // Extend the where clause back to the closing `>` of the
+                // generics, except for tuple struct, which have the `where`
+                // after the fields of the struct.
+                let full_where_span =
+                    if let hir::ItemKind::Struct(hir::VariantData::Tuple(..), _) = item.kind {
+                        where_span
+                    } else {
+                        hir_generics.span.shrink_to_hi().to(where_span)
+                    };
+                lint_spans.push(full_where_span);
+            } else {
+                lint_spans.extend(where_lint_spans);
+            }
+
+            if !lint_spans.is_empty() {
+                cx.struct_span_lint(EXPLICIT_OUTLIVES_REQUIREMENTS, lint_spans.clone(), |lint| {
+                    lint.build(fluent::lint::builtin_explicit_outlives)
+                        .set_arg("count", bound_count)
+                        .multipart_suggestion(
+                            fluent::lint::suggestion,
+                            lint_spans
+                                .into_iter()
+                                .map(|span| (span, String::new()))
+                                .collect::<Vec<_>>(),
+                            Applicability::MachineApplicable,
+                        )
+                        .emit();
+                });
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `incomplete_features` lint detects unstable features enabled with
+    /// the [`feature` attribute] that may function improperly in some or all
+    /// cases.
+    ///
+    /// [`feature` attribute]: https://doc.rust-lang.org/nightly/unstable-book/
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(generic_const_exprs)]
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Although it is encouraged for people to experiment with unstable
+    /// features, some of them are known to be incomplete or faulty. This lint
+    /// is a signal that the feature has not yet been finished, and you may
+    /// experience problems with it.
+    pub INCOMPLETE_FEATURES,
+    Warn,
+    "incomplete features that may function improperly in some or all cases"
+}
+
+declare_lint_pass!(
+    /// Check for used feature gates in `INCOMPLETE_FEATURES` in `rustc_feature/src/active.rs`.
+    IncompleteFeatures => [INCOMPLETE_FEATURES]
+);
+
+impl EarlyLintPass for IncompleteFeatures {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
+        let features = cx.sess().features_untracked();
+        features
+            .declared_lang_features
+            .iter()
+            .map(|(name, span, _)| (name, span))
+            .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
+            .filter(|(&name, _)| features.incomplete(name))
+            .for_each(|(&name, &span)| {
+                cx.struct_span_lint(INCOMPLETE_FEATURES, span, |lint| {
+                    let mut builder = lint.build(fluent::lint::builtin_incomplete_features);
+                    builder.set_arg("name", name);
+                    if let Some(n) = rustc_feature::find_feature_issue(name, GateIssue::Language) {
+                        builder.set_arg("n", n);
+                        builder.note(fluent::lint::note);
+                    }
+                    if HAS_MIN_FEATURES.contains(&name) {
+                        builder.help(fluent::lint::help);
+                    }
+                    builder.emit();
+                })
+            });
+    }
+}
+
+const HAS_MIN_FEATURES: &[Symbol] = &[sym::specialization];
+
+declare_lint! {
+    /// The `invalid_value` lint detects creating a value that is not valid,
+    /// such as a null reference.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,no_run
+    /// # #![allow(unused)]
+    /// unsafe {
+    ///     let x: &'static i32 = std::mem::zeroed();
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In some situations the compiler can detect that the code is creating
+    /// an invalid value, which should be avoided.
+    ///
+    /// In particular, this lint will check for improper use of
+    /// [`mem::zeroed`], [`mem::uninitialized`], [`mem::transmute`], and
+    /// [`MaybeUninit::assume_init`] that can cause [undefined behavior]. The
+    /// lint should provide extra information to indicate what the problem is
+    /// and a possible solution.
+    ///
+    /// [`mem::zeroed`]: https://doc.rust-lang.org/std/mem/fn.zeroed.html
+    /// [`mem::uninitialized`]: https://doc.rust-lang.org/std/mem/fn.uninitialized.html
+    /// [`mem::transmute`]: https://doc.rust-lang.org/std/mem/fn.transmute.html
+    /// [`MaybeUninit::assume_init`]: https://doc.rust-lang.org/std/mem/union.MaybeUninit.html#method.assume_init
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    pub INVALID_VALUE,
+    Warn,
+    "an invalid value is being created (such as a null reference)"
+}
+
+declare_lint_pass!(InvalidValue => [INVALID_VALUE]);
+
+impl<'tcx> LateLintPass<'tcx> for InvalidValue {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
+        #[derive(Debug, Copy, Clone, PartialEq)]
+        enum InitKind {
+            Zeroed,
+            Uninit,
+        }
+
+        /// Information about why a type cannot be initialized this way.
+        /// Contains an error message and optionally a span to point at.
+        type InitError = (String, Option<Span>);
+
+        /// Test if this constant is all-0.
+        fn is_zero(expr: &hir::Expr<'_>) -> bool {
+            use hir::ExprKind::*;
+            use rustc_ast::LitKind::*;
+            match &expr.kind {
+                Lit(lit) => {
+                    if let Int(i, _) = lit.node {
+                        i == 0
+                    } else {
+                        false
+                    }
+                }
+                Tup(tup) => tup.iter().all(is_zero),
+                _ => false,
+            }
+        }
+
+        /// Determine if this expression is a "dangerous initialization".
+        fn is_dangerous_init(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<InitKind> {
+            if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
+                // Find calls to `mem::{uninitialized,zeroed}` methods.
+                if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
+                    let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
+                    match cx.tcx.get_diagnostic_name(def_id) {
+                        Some(sym::mem_zeroed) => return Some(InitKind::Zeroed),
+                        Some(sym::mem_uninitialized) => return Some(InitKind::Uninit),
+                        Some(sym::transmute) if is_zero(&args[0]) => return Some(InitKind::Zeroed),
+                        _ => {}
+                    }
+                }
+            } else if let hir::ExprKind::MethodCall(_, ref args, _) = expr.kind {
+                // Find problematic calls to `MaybeUninit::assume_init`.
+                let def_id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
+                if cx.tcx.is_diagnostic_item(sym::assume_init, def_id) {
+                    // This is a call to *some* method named `assume_init`.
+                    // See if the `self` parameter is one of the dangerous constructors.
+                    if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
+                        if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
+                            let def_id = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
+                            match cx.tcx.get_diagnostic_name(def_id) {
+                                Some(sym::maybe_uninit_zeroed) => return Some(InitKind::Zeroed),
+                                Some(sym::maybe_uninit_uninit) => return Some(InitKind::Uninit),
+                                _ => {}
+                            }
+                        }
+                    }
+                }
+            }
+
+            None
+        }
+
+        /// Test if this enum has several actually "existing" variants.
+        /// Zero-sized uninhabited variants do not always have a tag assigned and thus do not "exist".
+        fn is_multi_variant<'tcx>(adt: ty::AdtDef<'tcx>) -> bool {
+            // As an approximation, we only count dataless variants. Those are definitely inhabited.
+            let existing_variants = adt.variants().iter().filter(|v| v.fields.is_empty()).count();
+            existing_variants > 1
+        }
+
+        /// Return `Some` only if we are sure this type does *not*
+        /// allow zero initialization.
+        fn ty_find_init_error<'tcx>(
+            cx: &LateContext<'tcx>,
+            ty: Ty<'tcx>,
+            init: InitKind,
+        ) -> Option<InitError> {
+            use rustc_type_ir::sty::TyKind::*;
+            match ty.kind() {
+                // Primitive types that don't like 0 as a value.
+                Ref(..) => Some(("references must be non-null".to_string(), None)),
+                Adt(..) if ty.is_box() => Some(("`Box` must be non-null".to_string(), None)),
+                FnPtr(..) => Some(("function pointers must be non-null".to_string(), None)),
+                Never => Some(("the `!` type has no valid value".to_string(), None)),
+                RawPtr(tm) if matches!(tm.ty.kind(), Dynamic(..)) =>
+                // raw ptr to dyn Trait
+                {
+                    Some(("the vtable of a wide raw pointer must be non-null".to_string(), None))
+                }
+                // Primitive types with other constraints.
+                Bool if init == InitKind::Uninit => {
+                    Some(("booleans must be either `true` or `false`".to_string(), None))
+                }
+                Char if init == InitKind::Uninit => {
+                    Some(("characters must be a valid Unicode codepoint".to_string(), None))
+                }
+                // Recurse and checks for some compound types.
+                Adt(adt_def, substs) if !adt_def.is_union() => {
+                    // First check if this ADT has a layout attribute (like `NonNull` and friends).
+                    use std::ops::Bound;
+                    match cx.tcx.layout_scalar_valid_range(adt_def.did()) {
+                        // We exploit here that `layout_scalar_valid_range` will never
+                        // return `Bound::Excluded`.  (And we have tests checking that we
+                        // handle the attribute correctly.)
+                        (Bound::Included(lo), _) if lo > 0 => {
+                            return Some((format!("`{}` must be non-null", ty), None));
+                        }
+                        (Bound::Included(_), _) | (_, Bound::Included(_))
+                            if init == InitKind::Uninit =>
+                        {
+                            return Some((
+                                format!(
+                                    "`{}` must be initialized inside its custom valid range",
+                                    ty,
+                                ),
+                                None,
+                            ));
+                        }
+                        _ => {}
+                    }
+                    // Now, recurse.
+                    match adt_def.variants().len() {
+                        0 => Some(("enums with no variants have no valid value".to_string(), None)),
+                        1 => {
+                            // Struct, or enum with exactly one variant.
+                            // Proceed recursively, check all fields.
+                            let variant = &adt_def.variant(VariantIdx::from_u32(0));
+                            variant.fields.iter().find_map(|field| {
+                                ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(
+                                    |(mut msg, span)| {
+                                        if span.is_none() {
+                                            // Point to this field, should be helpful for figuring
+                                            // out where the source of the error is.
+                                            let span = cx.tcx.def_span(field.did);
+                                            write!(
+                                                &mut msg,
+                                                " (in this {} field)",
+                                                adt_def.descr()
+                                            )
+                                            .unwrap();
+                                            (msg, Some(span))
+                                        } else {
+                                            // Just forward.
+                                            (msg, span)
+                                        }
+                                    },
+                                )
+                            })
+                        }
+                        // Multi-variant enum.
+                        _ => {
+                            if init == InitKind::Uninit && is_multi_variant(*adt_def) {
+                                let span = cx.tcx.def_span(adt_def.did());
+                                Some((
+                                    "enums have to be initialized to a variant".to_string(),
+                                    Some(span),
+                                ))
+                            } else {
+                                // In principle, for zero-initialization we could figure out which variant corresponds
+                                // to tag 0, and check that... but for now we just accept all zero-initializations.
+                                None
+                            }
+                        }
+                    }
+                }
+                Tuple(..) => {
+                    // Proceed recursively, check all fields.
+                    ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
+                }
+                Array(ty, len) => {
+                    if matches!(len.try_eval_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
+                        // Array length known at array non-empty -- recurse.
+                        ty_find_init_error(cx, *ty, init)
+                    } else {
+                        // Empty array or size unknown.
+                        None
+                    }
+                }
+                // Conservative fallback.
+                _ => None,
+            }
+        }
+
+        if let Some(init) = is_dangerous_init(cx, expr) {
+            // This conjures an instance of a type out of nothing,
+            // using zeroed or uninitialized memory.
+            // We are extremely conservative with what we warn about.
+            let conjured_ty = cx.typeck_results().expr_ty(expr);
+            if let Some((msg, span)) =
+                with_no_trimmed_paths!(ty_find_init_error(cx, conjured_ty, init))
+            {
+                // FIXME(davidtwco): make translatable
+                cx.struct_span_lint(INVALID_VALUE, expr.span, |lint| {
+                    let mut err = lint.build(&format!(
+                        "the type `{}` does not permit {}",
+                        conjured_ty,
+                        match init {
+                            InitKind::Zeroed => "zero-initialization",
+                            InitKind::Uninit => "being left uninitialized",
+                        },
+                    ));
+                    err.span_label(expr.span, "this code causes undefined behavior when executed");
+                    err.span_label(
+                        expr.span,
+                        "help: use `MaybeUninit<T>` instead, \
+                            and only call `assume_init` after initialization is done",
+                    );
+                    if let Some(span) = span {
+                        err.span_note(span, &msg);
+                    } else {
+                        err.note(&msg);
+                    }
+                    err.emit();
+                });
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `clashing_extern_declarations` lint detects when an `extern fn`
+    /// has been declared with the same name but different types.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// mod m {
+    ///     extern "C" {
+    ///         fn foo();
+    ///     }
+    /// }
+    ///
+    /// extern "C" {
+    ///     fn foo(_: u32);
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Because two symbols of the same name cannot be resolved to two
+    /// different functions at link time, and one function cannot possibly
+    /// have two types, a clashing extern declaration is almost certainly a
+    /// mistake. Check to make sure that the `extern` definitions are correct
+    /// and equivalent, and possibly consider unifying them in one location.
+    ///
+    /// This lint does not run between crates because a project may have
+    /// dependencies which both rely on the same extern function, but declare
+    /// it in a different (but valid) way. For example, they may both declare
+    /// an opaque type for one or more of the arguments (which would end up
+    /// distinct types), or use types that are valid conversions in the
+    /// language the `extern fn` is defined in. In these cases, the compiler
+    /// can't say that the clashing declaration is incorrect.
+    pub CLASHING_EXTERN_DECLARATIONS,
+    Warn,
+    "detects when an extern fn has been declared with the same name but different types"
+}
+
+pub struct ClashingExternDeclarations {
+    /// Map of function symbol name to the first-seen hir id for that symbol name.. If seen_decls
+    /// contains an entry for key K, it means a symbol with name K has been seen by this lint and
+    /// the symbol should be reported as a clashing declaration.
+    // FIXME: Technically, we could just store a &'tcx str here without issue; however, the
+    // `impl_lint_pass` macro doesn't currently support lints parametric over a lifetime.
+    seen_decls: FxHashMap<Symbol, HirId>,
+}
+
+/// Differentiate between whether the name for an extern decl came from the link_name attribute or
+/// just from declaration itself. This is important because we don't want to report clashes on
+/// symbol name if they don't actually clash because one or the other links against a symbol with a
+/// different name.
+enum SymbolName {
+    /// The name of the symbol + the span of the annotation which introduced the link name.
+    Link(Symbol, Span),
+    /// No link name, so just the name of the symbol.
+    Normal(Symbol),
+}
+
+impl SymbolName {
+    fn get_name(&self) -> Symbol {
+        match self {
+            SymbolName::Link(s, _) | SymbolName::Normal(s) => *s,
+        }
+    }
+}
+
+impl ClashingExternDeclarations {
+    pub(crate) fn new() -> Self {
+        ClashingExternDeclarations { seen_decls: FxHashMap::default() }
+    }
+    /// Insert a new foreign item into the seen set. If a symbol with the same name already exists
+    /// for the item, return its HirId without updating the set.
+    fn insert(&mut self, tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> Option<HirId> {
+        let did = fi.def_id.to_def_id();
+        let instance = Instance::new(did, ty::List::identity_for_item(tcx, did));
+        let name = Symbol::intern(tcx.symbol_name(instance).name);
+        if let Some(&hir_id) = self.seen_decls.get(&name) {
+            // Avoid updating the map with the new entry when we do find a collision. We want to
+            // make sure we're always pointing to the first definition as the previous declaration.
+            // This lets us avoid emitting "knock-on" diagnostics.
+            Some(hir_id)
+        } else {
+            self.seen_decls.insert(name, fi.hir_id())
+        }
+    }
+
+    /// Get the name of the symbol that's linked against for a given extern declaration. That is,
+    /// the name specified in a #[link_name = ...] attribute if one was specified, else, just the
+    /// symbol's name.
+    fn name_of_extern_decl(tcx: TyCtxt<'_>, fi: &hir::ForeignItem<'_>) -> SymbolName {
+        if let Some((overridden_link_name, overridden_link_name_span)) =
+            tcx.codegen_fn_attrs(fi.def_id).link_name.map(|overridden_link_name| {
+                // FIXME: Instead of searching through the attributes again to get span
+                // information, we could have codegen_fn_attrs also give span information back for
+                // where the attribute was defined. However, until this is found to be a
+                // bottleneck, this does just fine.
+                (
+                    overridden_link_name,
+                    tcx.get_attr(fi.def_id.to_def_id(), sym::link_name).unwrap().span,
+                )
+            })
+        {
+            SymbolName::Link(overridden_link_name, overridden_link_name_span)
+        } else {
+            SymbolName::Normal(fi.ident.name)
+        }
+    }
+
+    /// Checks whether two types are structurally the same enough that the declarations shouldn't
+    /// clash. We need this so we don't emit a lint when two modules both declare an extern struct,
+    /// with the same members (as the declarations shouldn't clash).
+    fn structurally_same_type<'tcx>(
+        cx: &LateContext<'tcx>,
+        a: Ty<'tcx>,
+        b: Ty<'tcx>,
+        ckind: CItemKind,
+    ) -> bool {
+        fn structurally_same_type_impl<'tcx>(
+            seen_types: &mut FxHashSet<(Ty<'tcx>, Ty<'tcx>)>,
+            cx: &LateContext<'tcx>,
+            a: Ty<'tcx>,
+            b: Ty<'tcx>,
+            ckind: CItemKind,
+        ) -> bool {
+            debug!("structurally_same_type_impl(cx, a = {:?}, b = {:?})", a, b);
+            let tcx = cx.tcx;
+
+            // Given a transparent newtype, reach through and grab the inner
+            // type unless the newtype makes the type non-null.
+            let non_transparent_ty = |ty: Ty<'tcx>| -> Ty<'tcx> {
+                let mut ty = ty;
+                loop {
+                    if let ty::Adt(def, substs) = *ty.kind() {
+                        let is_transparent = def.repr().transparent();
+                        let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
+                        debug!(
+                            "non_transparent_ty({:?}) -- type is transparent? {}, type is non-null? {}",
+                            ty, is_transparent, is_non_null
+                        );
+                        if is_transparent && !is_non_null {
+                            debug_assert!(def.variants().len() == 1);
+                            let v = &def.variant(VariantIdx::new(0));
+                            ty = transparent_newtype_field(tcx, v)
+                                .expect(
+                                    "single-variant transparent structure with zero-sized field",
+                                )
+                                .ty(tcx, substs);
+                            continue;
+                        }
+                    }
+                    debug!("non_transparent_ty -> {:?}", ty);
+                    return ty;
+                }
+            };
+
+            let a = non_transparent_ty(a);
+            let b = non_transparent_ty(b);
+
+            if !seen_types.insert((a, b)) {
+                // We've encountered a cycle. There's no point going any further -- the types are
+                // structurally the same.
+                return true;
+            }
+            let tcx = cx.tcx;
+            if a == b {
+                // All nominally-same types are structurally same, too.
+                true
+            } else {
+                // Do a full, depth-first comparison between the two.
+                use rustc_type_ir::sty::TyKind::*;
+                let a_kind = a.kind();
+                let b_kind = b.kind();
+
+                let compare_layouts = |a, b| -> Result<bool, LayoutError<'tcx>> {
+                    debug!("compare_layouts({:?}, {:?})", a, b);
+                    let a_layout = &cx.layout_of(a)?.layout.abi();
+                    let b_layout = &cx.layout_of(b)?.layout.abi();
+                    debug!(
+                        "comparing layouts: {:?} == {:?} = {}",
+                        a_layout,
+                        b_layout,
+                        a_layout == b_layout
+                    );
+                    Ok(a_layout == b_layout)
+                };
+
+                #[allow(rustc::usage_of_ty_tykind)]
+                let is_primitive_or_pointer = |kind: &ty::TyKind<'_>| {
+                    kind.is_primitive() || matches!(kind, RawPtr(..) | Ref(..))
+                };
+
+                ensure_sufficient_stack(|| {
+                    match (a_kind, b_kind) {
+                        (Adt(a_def, _), Adt(b_def, _)) => {
+                            // We can immediately rule out these types as structurally same if
+                            // their layouts differ.
+                            match compare_layouts(a, b) {
+                                Ok(false) => return false,
+                                _ => (), // otherwise, continue onto the full, fields comparison
+                            }
+
+                            // Grab a flattened representation of all fields.
+                            let a_fields = a_def.variants().iter().flat_map(|v| v.fields.iter());
+                            let b_fields = b_def.variants().iter().flat_map(|v| v.fields.iter());
+
+                            // Perform a structural comparison for each field.
+                            a_fields.eq_by(
+                                b_fields,
+                                |&ty::FieldDef { did: a_did, .. },
+                                 &ty::FieldDef { did: b_did, .. }| {
+                                    structurally_same_type_impl(
+                                        seen_types,
+                                        cx,
+                                        tcx.type_of(a_did),
+                                        tcx.type_of(b_did),
+                                        ckind,
+                                    )
+                                },
+                            )
+                        }
+                        (Array(a_ty, a_const), Array(b_ty, b_const)) => {
+                            // For arrays, we also check the constness of the type.
+                            a_const.kind() == b_const.kind()
+                                && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
+                        }
+                        (Slice(a_ty), Slice(b_ty)) => {
+                            structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
+                        }
+                        (RawPtr(a_tymut), RawPtr(b_tymut)) => {
+                            a_tymut.mutbl == b_tymut.mutbl
+                                && structurally_same_type_impl(
+                                    seen_types, cx, a_tymut.ty, b_tymut.ty, ckind,
+                                )
+                        }
+                        (Ref(_a_region, a_ty, a_mut), Ref(_b_region, b_ty, b_mut)) => {
+                            // For structural sameness, we don't need the region to be same.
+                            a_mut == b_mut
+                                && structurally_same_type_impl(seen_types, cx, *a_ty, *b_ty, ckind)
+                        }
+                        (FnDef(..), FnDef(..)) => {
+                            let a_poly_sig = a.fn_sig(tcx);
+                            let b_poly_sig = b.fn_sig(tcx);
+
+                            // We don't compare regions, but leaving bound regions around ICEs, so
+                            // we erase them.
+                            let a_sig = tcx.erase_late_bound_regions(a_poly_sig);
+                            let b_sig = tcx.erase_late_bound_regions(b_poly_sig);
+
+                            (a_sig.abi, a_sig.unsafety, a_sig.c_variadic)
+                                == (b_sig.abi, b_sig.unsafety, b_sig.c_variadic)
+                                && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
+                                    structurally_same_type_impl(seen_types, cx, *a, *b, ckind)
+                                })
+                                && structurally_same_type_impl(
+                                    seen_types,
+                                    cx,
+                                    a_sig.output(),
+                                    b_sig.output(),
+                                    ckind,
+                                )
+                        }
+                        (Tuple(a_substs), Tuple(b_substs)) => {
+                            a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
+                                structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
+                            })
+                        }
+                        // For these, it's not quite as easy to define structural-sameness quite so easily.
+                        // For the purposes of this lint, take the conservative approach and mark them as
+                        // not structurally same.
+                        (Dynamic(..), Dynamic(..))
+                        | (Error(..), Error(..))
+                        | (Closure(..), Closure(..))
+                        | (Generator(..), Generator(..))
+                        | (GeneratorWitness(..), GeneratorWitness(..))
+                        | (Projection(..), Projection(..))
+                        | (Opaque(..), Opaque(..)) => false,
+
+                        // These definitely should have been caught above.
+                        (Bool, Bool) | (Char, Char) | (Never, Never) | (Str, Str) => unreachable!(),
+
+                        // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
+                        // enum layout optimisation is being applied.
+                        (Adt(..), other_kind) | (other_kind, Adt(..))
+                            if is_primitive_or_pointer(other_kind) =>
+                        {
+                            let (primitive, adt) =
+                                if is_primitive_or_pointer(a.kind()) { (a, b) } else { (b, a) };
+                            if let Some(ty) = crate::types::repr_nullable_ptr(cx, adt, ckind) {
+                                ty == primitive
+                            } else {
+                                compare_layouts(a, b).unwrap_or(false)
+                            }
+                        }
+                        // Otherwise, just compare the layouts. This may fail to lint for some
+                        // incompatible types, but at the very least, will stop reads into
+                        // uninitialised memory.
+                        _ => compare_layouts(a, b).unwrap_or(false),
+                    }
+                })
+            }
+        }
+        let mut seen_types = FxHashSet::default();
+        structurally_same_type_impl(&mut seen_types, cx, a, b, ckind)
+    }
+}
+
+impl_lint_pass!(ClashingExternDeclarations => [CLASHING_EXTERN_DECLARATIONS]);
+
+impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
+    fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, this_fi: &hir::ForeignItem<'_>) {
+        trace!("ClashingExternDeclarations: check_foreign_item: {:?}", this_fi);
+        if let ForeignItemKind::Fn(..) = this_fi.kind {
+            let tcx = cx.tcx;
+            if let Some(existing_hid) = self.insert(tcx, this_fi) {
+                let existing_decl_ty = tcx.type_of(tcx.hir().local_def_id(existing_hid));
+                let this_decl_ty = tcx.type_of(this_fi.def_id);
+                debug!(
+                    "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
+                    existing_hid, existing_decl_ty, this_fi.def_id, this_decl_ty
+                );
+                // Check that the declarations match.
+                if !Self::structurally_same_type(
+                    cx,
+                    existing_decl_ty,
+                    this_decl_ty,
+                    CItemKind::Declaration,
+                ) {
+                    let orig_fi = tcx.hir().expect_foreign_item(existing_hid.expect_owner());
+                    let orig = Self::name_of_extern_decl(tcx, orig_fi);
+
+                    // We want to ensure that we use spans for both decls that include where the
+                    // name was defined, whether that was from the link_name attribute or not.
+                    let get_relevant_span =
+                        |fi: &hir::ForeignItem<'_>| match Self::name_of_extern_decl(tcx, fi) {
+                            SymbolName::Normal(_) => fi.span,
+                            SymbolName::Link(_, annot_span) => fi.span.to(annot_span),
+                        };
+                    // Finally, emit the diagnostic.
+                    tcx.struct_span_lint_hir(
+                        CLASHING_EXTERN_DECLARATIONS,
+                        this_fi.hir_id(),
+                        get_relevant_span(this_fi),
+                        |lint| {
+                            let mut expected_str = DiagnosticStyledString::new();
+                            expected_str.push(existing_decl_ty.fn_sig(tcx).to_string(), false);
+                            let mut found_str = DiagnosticStyledString::new();
+                            found_str.push(this_decl_ty.fn_sig(tcx).to_string(), true);
+
+                            lint.build(if orig.get_name() == this_fi.ident.name {
+                                fluent::lint::builtin_clashing_extern_same_name
+                            } else {
+                                fluent::lint::builtin_clashing_extern_diff_name
+                            })
+                            .set_arg("this_fi", this_fi.ident.name)
+                            .set_arg("orig", orig.get_name())
+                            .span_label(
+                                get_relevant_span(orig_fi),
+                                fluent::lint::previous_decl_label,
+                            )
+                            .span_label(get_relevant_span(this_fi), fluent::lint::mismatch_label)
+                            // FIXME(davidtwco): translatable expected/found
+                            .note_expected_found(&"", expected_str, &"", found_str)
+                            .emit();
+                        },
+                    );
+                }
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `deref_nullptr` lint detects when an null pointer is dereferenced,
+    /// which causes [undefined behavior].
+    ///
+    /// ### Example
+    ///
+    /// ```rust,no_run
+    /// # #![allow(unused)]
+    /// use std::ptr;
+    /// unsafe {
+    ///     let x = &*ptr::null::<i32>();
+    ///     let x = ptr::addr_of!(*ptr::null::<i32>());
+    ///     let x = *(0 as *const i32);
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
+    /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
+    ///
+    /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
+    pub DEREF_NULLPTR,
+    Warn,
+    "detects when an null pointer is dereferenced"
+}
+
+declare_lint_pass!(DerefNullPtr => [DEREF_NULLPTR]);
+
+impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &hir::Expr<'_>) {
+        /// test if expression is a null ptr
+        fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
+            match &expr.kind {
+                rustc_hir::ExprKind::Cast(ref expr, ref ty) => {
+                    if let rustc_hir::TyKind::Ptr(_) = ty.kind {
+                        return is_zero(expr) || is_null_ptr(cx, expr);
+                    }
+                }
+                // check for call to `core::ptr::null` or `core::ptr::null_mut`
+                rustc_hir::ExprKind::Call(ref path, _) => {
+                    if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
+                        if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
+                            return matches!(
+                                cx.tcx.get_diagnostic_name(def_id),
+                                Some(sym::ptr_null | sym::ptr_null_mut)
+                            );
+                        }
+                    }
+                }
+                _ => {}
+            }
+            false
+        }
+
+        /// test if expression is the literal `0`
+        fn is_zero(expr: &hir::Expr<'_>) -> bool {
+            match &expr.kind {
+                rustc_hir::ExprKind::Lit(ref lit) => {
+                    if let LitKind::Int(a, _) = lit.node {
+                        return a == 0;
+                    }
+                }
+                _ => {}
+            }
+            false
+        }
+
+        if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
+            if is_null_ptr(cx, expr_deref) {
+                cx.struct_span_lint(DEREF_NULLPTR, expr.span, |lint| {
+                    let mut err = lint.build(fluent::lint::builtin_deref_nullptr);
+                    err.span_label(expr.span, fluent::lint::label);
+                    err.emit();
+                });
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `named_asm_labels` lint detects the use of named labels in the
+    /// inline `asm!` macro.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// use std::arch::asm;
+    ///
+    /// fn main() {
+    ///     unsafe {
+    ///         asm!("foo: bar");
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// LLVM is allowed to duplicate inline assembly blocks for any
+    /// reason, for example when it is in a function that gets inlined. Because
+    /// of this, GNU assembler [local labels] *must* be used instead of labels
+    /// with a name. Using named labels might cause assembler or linker errors.
+    ///
+    /// See the explanation in [Rust By Example] for more details.
+    ///
+    /// [local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
+    /// [Rust By Example]: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels
+    pub NAMED_ASM_LABELS,
+    Deny,
+    "named labels in inline assembly",
+}
+
+declare_lint_pass!(NamedAsmLabels => [NAMED_ASM_LABELS]);
+
+impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+        if let hir::Expr {
+            kind: hir::ExprKind::InlineAsm(hir::InlineAsm { template_strs, .. }),
+            ..
+        } = expr
+        {
+            for (template_sym, template_snippet, template_span) in template_strs.iter() {
+                let template_str = template_sym.as_str();
+                let find_label_span = |needle: &str| -> Option<Span> {
+                    if let Some(template_snippet) = template_snippet {
+                        let snippet = template_snippet.as_str();
+                        if let Some(pos) = snippet.find(needle) {
+                            let end = pos
+                                + snippet[pos..]
+                                    .find(|c| c == ':')
+                                    .unwrap_or(snippet[pos..].len() - 1);
+                            let inner = InnerSpan::new(pos, end);
+                            return Some(template_span.from_inner(inner));
+                        }
+                    }
+
+                    None
+                };
+
+                let mut found_labels = Vec::new();
+
+                // A semicolon might not actually be specified as a separator for all targets, but it seems like LLVM accepts it always
+                let statements = template_str.split(|c| matches!(c, '\n' | ';'));
+                for statement in statements {
+                    // If there's a comment, trim it from the statement
+                    let statement = statement.find("//").map_or(statement, |idx| &statement[..idx]);
+                    let mut start_idx = 0;
+                    for (idx, _) in statement.match_indices(':') {
+                        let possible_label = statement[start_idx..idx].trim();
+                        let mut chars = possible_label.chars();
+                        let Some(c) = chars.next() else {
+                            // Empty string means a leading ':' in this section, which is not a label
+                            break
+                        };
+                        // A label starts with an alphabetic character or . or _ and continues with alphanumeric characters, _, or $
+                        if (c.is_alphabetic() || matches!(c, '.' | '_'))
+                            && chars.all(|c| c.is_alphanumeric() || matches!(c, '_' | '$'))
+                        {
+                            found_labels.push(possible_label);
+                        } else {
+                            // If we encounter a non-label, there cannot be any further labels, so stop checking
+                            break;
+                        }
+
+                        start_idx = idx + 1;
+                    }
+                }
+
+                debug!("NamedAsmLabels::check_expr(): found_labels: {:#?}", &found_labels);
+
+                if found_labels.len() > 0 {
+                    let spans = found_labels
+                        .into_iter()
+                        .filter_map(|label| find_label_span(label))
+                        .collect::<Vec<Span>>();
+                    // If there were labels but we couldn't find a span, combine the warnings and use the template span
+                    let target_spans: MultiSpan =
+                        if spans.len() > 0 { spans.into() } else { (*template_span).into() };
+
+                    cx.lookup_with_diagnostics(
+                            NAMED_ASM_LABELS,
+                            Some(target_spans),
+                            |diag| {
+                                diag.build(fluent::lint::builtin_asm_labels).emit();
+                            },
+                            BuiltinLintDiagnostics::NamedAsmLabel(
+                                "only local labels of the form `<number>:` should be used in inline asm"
+                                    .to_string(),
+                            ),
+                        );
+                }
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
new file mode 100644
index 000000000..b95fc341d
--- /dev/null
+++ b/compiler/rustc_lint/src/context.rs
@@ -0,0 +1,1259 @@
+//! Implementation of lint checking.
+//!
+//! The lint checking is mostly consolidated into one pass which runs
+//! after all other analyses. Throughout compilation, lint warnings
+//! can be added via the `add_lint` method on the Session structure. This
+//! requires a span and an ID of the node that the lint is being added to. The
+//! lint isn't actually emitted at that time because it is unknown what the
+//! actual lint level at that location is.
+//!
+//! To actually emit lint warnings/errors, a separate pass is used.
+//! A context keeps track of the current state of all lint levels.
+//! Upon entering a node of the ast which can modify the lint settings, the
+//! previous lint state is pushed onto a stack and the ast is then recursed
+//! upon. As the ast is traversed, this keeps track of the current lint level
+//! for all lint attributes.
+
+use self::TargetLint::*;
+
+use crate::levels::LintLevelsBuilder;
+use crate::passes::{EarlyLintPassObject, LateLintPassObject};
+use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync;
+use rustc_errors::{add_elided_lifetime_in_path_suggestion, struct_span_err};
+use rustc_errors::{
+    Applicability, DecorateLint, LintDiagnosticBuilder, MultiSpan, SuggestionStyle,
+};
+use rustc_hir as hir;
+use rustc_hir::def::Res;
+use rustc_hir::def_id::{CrateNum, DefId};
+use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
+use rustc_middle::middle::privacy::AccessLevels;
+use rustc_middle::middle::stability;
+use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
+use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
+use rustc_session::lint::{BuiltinLintDiagnostics, LintExpectationId};
+use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
+use rustc_session::Session;
+use rustc_span::lev_distance::find_best_match_for_name;
+use rustc_span::symbol::{sym, Ident, Symbol};
+use rustc_span::{BytePos, Span, DUMMY_SP};
+use rustc_target::abi;
+use tracing::debug;
+
+use std::cell::Cell;
+use std::iter;
+use std::slice;
+
+/// Information about the registered lints.
+///
+/// This is basically the subset of `Context` that we can
+/// build early in the compile pipeline.
+pub struct LintStore {
+    /// Registered lints.
+    lints: Vec<&'static Lint>,
+
+    /// Constructor functions for each variety of lint pass.
+    ///
+    /// These should only be called once, but since we want to avoid locks or
+    /// interior mutability, we don't enforce this (and lints should, in theory,
+    /// be compatible with being constructed more than once, though not
+    /// necessarily in a sane manner. This is safe though.)
+    pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
+    /// This is unique in that we construct them per-module, so not once.
+    pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
+
+    /// Lints indexed by name.
+    by_name: FxHashMap<String, TargetLint>,
+
+    /// Map of registered lint groups to what lints they expand to.
+    lint_groups: FxHashMap<&'static str, LintGroup>,
+}
+
+/// The target of the `by_name` map, which accounts for renaming/deprecation.
+#[derive(Debug)]
+enum TargetLint {
+    /// A direct lint target
+    Id(LintId),
+
+    /// Temporary renaming, used for easing migration pain; see #16545
+    Renamed(String, LintId),
+
+    /// Lint with this name existed previously, but has been removed/deprecated.
+    /// The string argument is the reason for removal.
+    Removed(String),
+
+    /// A lint name that should give no warnings and have no effect.
+    ///
+    /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
+    Ignored,
+}
+
+pub enum FindLintError {
+    NotFound,
+    Removed,
+}
+
+struct LintAlias {
+    name: &'static str,
+    /// Whether deprecation warnings should be suppressed for this alias.
+    silent: bool,
+}
+
+struct LintGroup {
+    lint_ids: Vec<LintId>,
+    from_plugin: bool,
+    depr: Option<LintAlias>,
+}
+
+#[derive(Debug)]
+pub enum CheckLintNameResult<'a> {
+    Ok(&'a [LintId]),
+    /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
+    NoLint(Option<Symbol>),
+    /// The lint refers to a tool that has not been registered.
+    NoTool,
+    /// The lint is either renamed or removed. This is the warning
+    /// message, and an optional new name (`None` if removed).
+    Warning(String, Option<String>),
+    /// The lint is from a tool. If the Option is None, then either
+    /// the lint does not exist in the tool or the code was not
+    /// compiled with the tool and therefore the lint was never
+    /// added to the `LintStore`. Otherwise the `LintId` will be
+    /// returned as if it where a rustc lint.
+    Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
+}
+
+impl LintStore {
+    pub fn new() -> LintStore {
+        LintStore {
+            lints: vec![],
+            pre_expansion_passes: vec![],
+            early_passes: vec![],
+            late_passes: vec![],
+            late_module_passes: vec![],
+            by_name: Default::default(),
+            lint_groups: Default::default(),
+        }
+    }
+
+    pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
+        &self.lints
+    }
+
+    pub fn get_lint_groups<'t>(
+        &'t self,
+    ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
+        // This function is not used in a way which observes the order of lints.
+        #[allow(rustc::potential_query_instability)]
+        self.lint_groups
+            .iter()
+            .filter(|(_, LintGroup { depr, .. })| {
+                // Don't display deprecated lint groups.
+                depr.is_none()
+            })
+            .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
+                (*k, lint_ids.clone(), *from_plugin)
+            })
+    }
+
+    pub fn register_early_pass(
+        &mut self,
+        pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.early_passes.push(Box::new(pass));
+    }
+
+    /// This lint pass is softly deprecated. It misses expanded code and has caused a few
+    /// errors in the past. Currently, it is only used in Clippy. New implementations
+    /// should avoid using this interface, as it might be removed in the future.
+    ///
+    /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
+    /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
+    pub fn register_pre_expansion_pass(
+        &mut self,
+        pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.pre_expansion_passes.push(Box::new(pass));
+    }
+
+    pub fn register_late_pass(
+        &mut self,
+        pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.late_passes.push(Box::new(pass));
+    }
+
+    pub fn register_late_mod_pass(
+        &mut self,
+        pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.late_module_passes.push(Box::new(pass));
+    }
+
+    // Helper method for register_early/late_pass
+    pub fn register_lints(&mut self, lints: &[&'static Lint]) {
+        for lint in lints {
+            self.lints.push(lint);
+
+            let id = LintId::of(lint);
+            if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
+                bug!("duplicate specification of lint {}", lint.name_lower())
+            }
+
+            if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
+                if let Some(edition) = reason.edition() {
+                    self.lint_groups
+                        .entry(edition.lint_name())
+                        .or_insert(LintGroup {
+                            lint_ids: vec![],
+                            from_plugin: lint.is_plugin,
+                            depr: None,
+                        })
+                        .lint_ids
+                        .push(id);
+                } else {
+                    // Lints belonging to the `future_incompatible` lint group are lints where a
+                    // future version of rustc will cause existing code to stop compiling.
+                    // Lints tied to an edition don't count because they are opt-in.
+                    self.lint_groups
+                        .entry("future_incompatible")
+                        .or_insert(LintGroup {
+                            lint_ids: vec![],
+                            from_plugin: lint.is_plugin,
+                            depr: None,
+                        })
+                        .lint_ids
+                        .push(id);
+                }
+            }
+        }
+    }
+
+    pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
+        self.lint_groups.insert(
+            alias,
+            LintGroup {
+                lint_ids: vec![],
+                from_plugin: false,
+                depr: Some(LintAlias { name: lint_name, silent: true }),
+            },
+        );
+    }
+
+    pub fn register_group(
+        &mut self,
+        from_plugin: bool,
+        name: &'static str,
+        deprecated_name: Option<&'static str>,
+        to: Vec<LintId>,
+    ) {
+        let new = self
+            .lint_groups
+            .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
+            .is_none();
+        if let Some(deprecated) = deprecated_name {
+            self.lint_groups.insert(
+                deprecated,
+                LintGroup {
+                    lint_ids: vec![],
+                    from_plugin,
+                    depr: Some(LintAlias { name, silent: false }),
+                },
+            );
+        }
+
+        if !new {
+            bug!("duplicate specification of lint group {}", name);
+        }
+    }
+
+    /// This lint should give no warning and have no effect.
+    ///
+    /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
+    #[track_caller]
+    pub fn register_ignored(&mut self, name: &str) {
+        if self.by_name.insert(name.to_string(), Ignored).is_some() {
+            bug!("duplicate specification of lint {}", name);
+        }
+    }
+
+    /// This lint has been renamed; warn about using the new name and apply the lint.
+    #[track_caller]
+    pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
+        let Some(&Id(target)) = self.by_name.get(new_name) else {
+            bug!("invalid lint renaming of {} to {}", old_name, new_name);
+        };
+        self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
+    }
+
+    pub fn register_removed(&mut self, name: &str, reason: &str) {
+        self.by_name.insert(name.into(), Removed(reason.into()));
+    }
+
+    pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
+        match self.by_name.get(lint_name) {
+            Some(&Id(lint_id)) => Ok(vec![lint_id]),
+            Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
+            Some(&Removed(_)) => Err(FindLintError::Removed),
+            Some(&Ignored) => Ok(vec![]),
+            None => loop {
+                return match self.lint_groups.get(lint_name) {
+                    Some(LintGroup { lint_ids, depr, .. }) => {
+                        if let Some(LintAlias { name, .. }) = depr {
+                            lint_name = name;
+                            continue;
+                        }
+                        Ok(lint_ids.clone())
+                    }
+                    None => Err(FindLintError::Removed),
+                };
+            },
+        }
+    }
+
+    /// Checks the validity of lint names derived from the command line.
+    pub fn check_lint_name_cmdline(
+        &self,
+        sess: &Session,
+        lint_name: &str,
+        level: Level,
+        registered_tools: &RegisteredTools,
+    ) {
+        let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
+        if lint_name_only == crate::WARNINGS.name_lower() && matches!(level, Level::ForceWarn(_)) {
+            struct_span_err!(
+                sess,
+                DUMMY_SP,
+                E0602,
+                "`{}` lint group is not supported with ´--force-warn´",
+                crate::WARNINGS.name_lower()
+            )
+            .emit();
+            return;
+        }
+        let db = match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
+            CheckLintNameResult::Ok(_) => None,
+            CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
+            CheckLintNameResult::NoLint(suggestion) => {
+                let mut err =
+                    struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
+
+                if let Some(suggestion) = suggestion {
+                    err.help(&format!("did you mean: `{}`", suggestion));
+                }
+
+                Some(err.forget_guarantee())
+            }
+            CheckLintNameResult::Tool(result) => match result {
+                Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
+                    "lint name `{}` is deprecated \
+                     and does not have an effect anymore. \
+                     Use: {}",
+                    lint_name, new_name
+                ))),
+                _ => None,
+            },
+            CheckLintNameResult::NoTool => Some(
+                struct_span_err!(
+                    sess,
+                    DUMMY_SP,
+                    E0602,
+                    "unknown lint tool: `{}`",
+                    tool_name.unwrap()
+                )
+                .forget_guarantee(),
+            ),
+        };
+
+        if let Some(mut db) = db {
+            let msg = format!(
+                "requested on the command line with `{} {}`",
+                match level {
+                    Level::Allow => "-A",
+                    Level::Warn => "-W",
+                    Level::ForceWarn(_) => "--force-warn",
+                    Level::Deny => "-D",
+                    Level::Forbid => "-F",
+                    Level::Expect(_) => {
+                        unreachable!("lints with the level of `expect` should not run this code");
+                    }
+                },
+                lint_name
+            );
+            db.note(&msg);
+            db.emit();
+        }
+    }
+
+    /// True if this symbol represents a lint group name.
+    pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
+        debug!(
+            "is_lint_group(lint_name={:?}, lint_groups={:?})",
+            lint_name,
+            self.lint_groups.keys().collect::<Vec<_>>()
+        );
+        let lint_name_str = lint_name.as_str();
+        self.lint_groups.contains_key(lint_name_str) || {
+            let warnings_name_str = crate::WARNINGS.name_lower();
+            lint_name_str == warnings_name_str
+        }
+    }
+
+    /// Checks the name of a lint for its existence, and whether it was
+    /// renamed or removed. Generates a DiagnosticBuilder containing a
+    /// warning for renamed and removed lints. This is over both lint
+    /// names from attributes and those passed on the command line. Since
+    /// it emits non-fatal warnings and there are *two* lint passes that
+    /// inspect attributes, this is only run from the late pass to avoid
+    /// printing duplicate warnings.
+    pub fn check_lint_name(
+        &self,
+        lint_name: &str,
+        tool_name: Option<Symbol>,
+        registered_tools: &RegisteredTools,
+    ) -> CheckLintNameResult<'_> {
+        if let Some(tool_name) = tool_name {
+            // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
+            if tool_name != sym::rustc
+                && tool_name != sym::rustdoc
+                && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
+            {
+                return CheckLintNameResult::NoTool;
+            }
+        }
+
+        let complete_name = if let Some(tool_name) = tool_name {
+            format!("{}::{}", tool_name, lint_name)
+        } else {
+            lint_name.to_string()
+        };
+        // If the lint was scoped with `tool::` check if the tool lint exists
+        if let Some(tool_name) = tool_name {
+            match self.by_name.get(&complete_name) {
+                None => match self.lint_groups.get(&*complete_name) {
+                    // If the lint isn't registered, there are two possibilities:
+                    None => {
+                        // 1. The tool is currently running, so this lint really doesn't exist.
+                        // FIXME: should this handle tools that never register a lint, like rustfmt?
+                        tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
+                        let tool_prefix = format!("{}::", tool_name);
+                        return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
+                            self.no_lint_suggestion(&complete_name)
+                        } else {
+                            // 2. The tool isn't currently running, so no lints will be registered.
+                            // To avoid giving a false positive, ignore all unknown lints.
+                            CheckLintNameResult::Tool(Err((None, String::new())))
+                        };
+                    }
+                    Some(LintGroup { lint_ids, .. }) => {
+                        return CheckLintNameResult::Tool(Ok(&lint_ids));
+                    }
+                },
+                Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
+                // If the lint was registered as removed or renamed by the lint tool, we don't need
+                // to treat tool_lints and rustc lints different and can use the code below.
+                _ => {}
+            }
+        }
+        match self.by_name.get(&complete_name) {
+            Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
+                format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
+                Some(new_name.to_owned()),
+            ),
+            Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
+                format!("lint `{}` has been removed: {}", complete_name, reason),
+                None,
+            ),
+            None => match self.lint_groups.get(&*complete_name) {
+                // If neither the lint, nor the lint group exists check if there is a `clippy::`
+                // variant of this lint
+                None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
+                Some(LintGroup { lint_ids, depr, .. }) => {
+                    // Check if the lint group name is deprecated
+                    if let Some(LintAlias { name, silent }) = depr {
+                        let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
+                        return if *silent {
+                            CheckLintNameResult::Ok(&lint_ids)
+                        } else {
+                            CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
+                        };
+                    }
+                    CheckLintNameResult::Ok(&lint_ids)
+                }
+            },
+            Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
+            Some(&Ignored) => CheckLintNameResult::Ok(&[]),
+        }
+    }
+
+    fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
+        let name_lower = lint_name.to_lowercase();
+
+        if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
+            // First check if the lint name is (partly) in upper case instead of lower case...
+            return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
+        }
+        // ...if not, search for lints with a similar name
+        let groups = self.lint_groups.keys().copied().map(Symbol::intern);
+        let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
+        let names: Vec<Symbol> = groups.chain(lints).collect();
+        let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
+        CheckLintNameResult::NoLint(suggestion)
+    }
+
+    fn check_tool_name_for_backwards_compat(
+        &self,
+        lint_name: &str,
+        tool_name: &str,
+    ) -> CheckLintNameResult<'_> {
+        let complete_name = format!("{}::{}", tool_name, lint_name);
+        match self.by_name.get(&complete_name) {
+            None => match self.lint_groups.get(&*complete_name) {
+                // Now we are sure, that this lint exists nowhere
+                None => self.no_lint_suggestion(lint_name),
+                Some(LintGroup { lint_ids, depr, .. }) => {
+                    // Reaching this would be weird, but let's cover this case anyway
+                    if let Some(LintAlias { name, silent }) = depr {
+                        let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
+                        return if *silent {
+                            CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
+                        } else {
+                            CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
+                        };
+                    }
+                    CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
+                }
+            },
+            Some(&Id(ref id)) => {
+                CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
+            }
+            Some(other) => {
+                tracing::debug!("got renamed lint {:?}", other);
+                CheckLintNameResult::NoLint(None)
+            }
+        }
+    }
+}
+
+/// Context for lint checking outside of type inference.
+pub struct LateContext<'tcx> {
+    /// Type context we're checking in.
+    pub tcx: TyCtxt<'tcx>,
+
+    /// Current body, or `None` if outside a body.
+    pub enclosing_body: Option<hir::BodyId>,
+
+    /// Type-checking results for the current body. Access using the `typeck_results`
+    /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
+    // FIXME(eddyb) move all the code accessing internal fields like this,
+    // to this module, to avoid exposing it to lint logic.
+    pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
+
+    /// Parameter environment for the item we are in.
+    pub param_env: ty::ParamEnv<'tcx>,
+
+    /// Items accessible from the crate being checked.
+    pub access_levels: &'tcx AccessLevels,
+
+    /// The store of registered lints and the lint levels.
+    pub lint_store: &'tcx LintStore,
+
+    pub last_node_with_lint_attrs: hir::HirId,
+
+    /// Generic type parameters in scope for the item we are in.
+    pub generics: Option<&'tcx hir::Generics<'tcx>>,
+
+    /// We are only looking at one module
+    pub only_module: bool,
+}
+
+/// Context for lint checking of the AST, after expansion, before lowering to HIR.
+pub struct EarlyContext<'a> {
+    pub builder: LintLevelsBuilder<'a>,
+    pub buffered: LintBuffer,
+}
+
+pub trait LintPassObject: Sized {}
+
+impl LintPassObject for EarlyLintPassObject {}
+
+impl LintPassObject for LateLintPassObject {}
+
+pub trait LintContext: Sized {
+    type PassObject: LintPassObject;
+
+    fn sess(&self) -> &Session;
+    fn lints(&self) -> &LintStore;
+
+    fn lookup_with_diagnostics(
+        &self,
+        lint: &'static Lint,
+        span: Option<impl Into<MultiSpan>>,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+        diagnostic: BuiltinLintDiagnostics,
+    ) {
+        self.lookup(lint, span, |lint| {
+            // We first generate a blank diagnostic.
+            let mut db = lint.build("");
+
+            // Now, set up surrounding context.
+            let sess = self.sess();
+            match diagnostic {
+                BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
+                    let spans: Vec<_> = content
+                        .char_indices()
+                        .filter_map(|(i, c)| {
+                            TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
+                                let lo = span.lo() + BytePos(2 + i as u32);
+                                (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
+                            })
+                        })
+                        .collect();
+                    let (an, s) = match spans.len() {
+                        1 => ("an ", ""),
+                        _ => ("", "s"),
+                    };
+                    db.span_label(span, &format!(
+                        "this comment contains {}invisible unicode text flow control codepoint{}",
+                        an,
+                        s,
+                    ));
+                    for (c, span) in &spans {
+                        db.span_label(*span, format!("{:?}", c));
+                    }
+                    db.note(
+                        "these kind of unicode codepoints change the way text flows on \
+                         applications that support them, but can cause confusion because they \
+                         change the order of characters on the screen",
+                    );
+                    if !spans.is_empty() {
+                        db.multipart_suggestion_with_style(
+                            "if their presence wasn't intentional, you can remove them",
+                            spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
+                            Applicability::MachineApplicable,
+                            SuggestionStyle::HideCodeAlways,
+                        );
+                    }
+                },
+                BuiltinLintDiagnostics::Normal => (),
+                BuiltinLintDiagnostics::AbsPathWithModule(span) => {
+                    let (sugg, app) = match sess.source_map().span_to_snippet(span) {
+                        Ok(ref s) => {
+                            // FIXME(Manishearth) ideally the emitting code
+                            // can tell us whether or not this is global
+                            let opt_colon =
+                                if s.trim_start().starts_with("::") { "" } else { "::" };
+
+                            (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
+                        }
+                        Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
+                    };
+                    db.span_suggestion(span, "use `crate`", sugg, app);
+                }
+                BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
+                    db.span_label(
+                        span,
+                        "names from parent modules are not accessible without an explicit import",
+                    );
+                }
+                BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
+                    span_def,
+                ) => {
+                    db.span_note(span_def, "the macro is defined here");
+                }
+                BuiltinLintDiagnostics::ElidedLifetimesInPaths(
+                    n,
+                    path_span,
+                    incl_angl_brckt,
+                    insertion_span,
+                ) => {
+                    add_elided_lifetime_in_path_suggestion(
+                        sess.source_map(),
+                        &mut db,
+                        n,
+                        path_span,
+                        incl_angl_brckt,
+                        insertion_span,
+                    );
+                }
+                BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
+                    db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
+                }
+                BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
+                    if !replaces.is_empty() {
+                        db.tool_only_multipart_suggestion(
+                            &message,
+                            replaces,
+                            Applicability::MachineApplicable,
+                        );
+                    }
+
+                    if let Some(span) = in_test_module {
+                        db.span_help(
+                            self.sess().source_map().guess_head_span(span),
+                            "consider adding a `#[cfg(test)]` to the containing module",
+                        );
+                    }
+                }
+                BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
+                    for (span, is_imported) in spans {
+                        let introduced = if is_imported { "imported" } else { "defined" };
+                        db.span_label(
+                            span,
+                            format!("the item `{}` is already {} here", ident, introduced),
+                        );
+                    }
+                }
+                BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
+                    stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
+                }
+                BuiltinLintDiagnostics::UnusedDocComment(span) => {
+                    db.span_label(span, "rustdoc does not generate documentation for macro invocations");
+                    db.help("to document an item produced by a macro, \
+                                  the macro must produce the documentation as part of its expansion");
+                }
+                BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
+                    db.span_suggestion(span, "remove `mut` from the parameter", ident, Applicability::MachineApplicable);
+                }
+                BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
+                    db.span_label(span, "ABI should be specified here");
+                    db.help(&format!("the default ABI is {}", default_abi.name()));
+                }
+                BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
+                    db.span_label(span, "the attribute is introduced here");
+                }
+                BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
+                    db.note(&note);
+                }
+                BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
+                    db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
+                }
+                BuiltinLintDiagnostics::ReservedPrefix(span) => {
+                    db.span_label(span, "unknown prefix");
+                    db.span_suggestion_verbose(
+                        span.shrink_to_hi(),
+                        "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
+                        " ",
+                        Applicability::MachineApplicable,
+                    );
+                }
+                BuiltinLintDiagnostics::UnusedBuiltinAttribute {
+                    attr_name,
+                    macro_name,
+                    invoc_span
+                } => {
+                    db.span_note(
+                        invoc_span,
+                        &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
+                    );
+                }
+                BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
+                    if is_trailing {
+                        db.note("macro invocations at the end of a block are treated as expressions");
+                        db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
+                    }
+                }
+                BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
+                    db.multipart_suggestion(
+                        "wrap this expression in parentheses",
+                        vec![(span.shrink_to_lo(), "(".to_string()),
+                             (span.shrink_to_hi(), ")".to_string())],
+                        Applicability::MachineApplicable
+                    );
+                }
+                BuiltinLintDiagnostics::NamedAsmLabel(help) => {
+                    db.help(&help);
+                    db.note("see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information");
+                },
+                BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), None) => {
+                    let Some(names_valid) = &sess.parse_sess.check_config.names_valid else {
+                        bug!("it shouldn't be possible to have a diagnostic on a name if name checking is not enabled");
+                    };
+                    let possibilities: Vec<Symbol> = names_valid.iter().map(|s| *s).collect();
+
+                    // Suggest the most probable if we found one
+                    if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
+                        db.span_suggestion(name_span, "did you mean", best_match, Applicability::MaybeIncorrect);
+                    }
+                },
+                BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), Some((value, value_span))) => {
+                    let Some(values) = &sess.parse_sess.check_config.values_valid.get(&name) else {
+                        bug!("it shouldn't be possible to have a diagnostic on a value whose name is not in values");
+                    };
+                    let possibilities: Vec<Symbol> = values.iter().map(|&s| s).collect();
+
+                    // Show the full list if all possible values for a given name, but don't do it
+                    // for names as the possibilities could be very long
+                    if !possibilities.is_empty() {
+                        {
+                            let mut possibilities = possibilities.iter().map(Symbol::as_str).collect::<Vec<_>>();
+                            possibilities.sort();
+
+                            let possibilities = possibilities.join(", ");
+                            db.note(&format!("expected values for `{name}` are: {possibilities}"));
+                        }
+
+                        // Suggest the most probable if we found one
+                        if let Some(best_match) = find_best_match_for_name(&possibilities, value, None) {
+                            db.span_suggestion(value_span, "did you mean", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
+                        }
+                    } else {
+                        db.note(&format!("no expected value for `{name}`"));
+                        if name != sym::feature {
+                            db.span_suggestion(name_span.shrink_to_hi().to(value_span), "remove the value", "", Applicability::MaybeIncorrect);
+                        }
+                    }
+                },
+                BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(new_span, suggestion) => {
+                    db.multipart_suggestion(
+                        "move it to the end of the type declaration",
+                        vec![(db.span.primary_span().unwrap(), "".to_string()), (new_span, suggestion)],
+                        Applicability::MachineApplicable,
+                    );
+                    db.note(
+                        "see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information",
+                    );
+                },
+                BuiltinLintDiagnostics::SingleUseLifetime {
+                    param_span,
+                    use_span: Some((use_span, elide)),
+                    deletion_span,
+                } => {
+                    debug!(?param_span, ?use_span, ?deletion_span);
+                    db.span_label(param_span, "this lifetime...");
+                    db.span_label(use_span, "...is used only here");
+                    let msg = "elide the single-use lifetime";
+                    let (use_span, replace_lt) = if elide {
+                        let use_span = sess.source_map().span_extend_while(
+                            use_span,
+                            char::is_whitespace,
+                        ).unwrap_or(use_span);
+                        (use_span, String::new())
+                    } else {
+                        (use_span, "'_".to_owned())
+                    };
+                    db.multipart_suggestion(
+                        msg,
+                        vec![(deletion_span, String::new()), (use_span, replace_lt)],
+                        Applicability::MachineApplicable,
+                    );
+                },
+                BuiltinLintDiagnostics::SingleUseLifetime {
+                    param_span: _,
+                    use_span: None,
+                    deletion_span,
+                } => {
+                    debug!(?deletion_span);
+                    db.span_suggestion(
+                        deletion_span,
+                        "elide the unused lifetime",
+                        "",
+                        Applicability::MachineApplicable,
+                    );
+                },
+                BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
+                    db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");
+                    if let Some(positional_arg_for_msg) = position_sp_for_msg {
+                        let msg = format!("this formatting argument uses named argument `{}` by position", named_arg_name);
+                        db.span_label(positional_arg_for_msg, msg);
+                    }
+
+                    if let Some(positional_arg_to_replace) = position_sp_to_replace {
+                        let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
+
+                        db.span_suggestion_verbose(
+                            positional_arg_to_replace,
+                            "use the named argument by name to avoid ambiguity",
+                            name,
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
+                }
+            }
+            // Rewrap `db`, and pass control to the user.
+            decorate(LintDiagnosticBuilder::new(db));
+        });
+    }
+
+    // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
+    // set the span in their `decorate` function (preferably using set_span).
+    fn lookup<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: Option<S>,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    );
+
+    /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
+    /// typically generated by `#[derive(LintDiagnostic)]`).
+    fn emit_spanned_lint<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: S,
+        decorator: impl for<'a> DecorateLint<'a, ()>,
+    ) {
+        self.lookup(lint, Some(span), |diag| decorator.decorate_lint(diag));
+    }
+
+    fn struct_span_lint<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: S,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        self.lookup(lint, Some(span), decorate);
+    }
+
+    /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
+    /// generated by `#[derive(LintDiagnostic)]`).
+    fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
+        self.lookup(lint, None as Option<Span>, |diag| decorator.decorate_lint(diag));
+    }
+
+    /// Emit a lint at the appropriate level, with no associated span.
+    fn lint(
+        &self,
+        lint: &'static Lint,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        self.lookup(lint, None as Option<Span>, decorate);
+    }
+
+    /// This returns the lint level for the given lint at the current location.
+    fn get_lint_level(&self, lint: &'static Lint) -> Level;
+
+    /// This function can be used to manually fulfill an expectation. This can
+    /// be used for lints which contain several spans, and should be suppressed,
+    /// if either location was marked with an expectation.
+    ///
+    /// Note that this function should only be called for [`LintExpectationId`]s
+    /// retrieved from the current lint pass. Buffered or manually created ids can
+    /// cause ICEs.
+    fn fulfill_expectation(&self, expectation: LintExpectationId) {
+        // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
+        // and stored between compilation sessions. To not manually do these steps, we simply create
+        // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
+        // expected lint diagnostic.
+        self.sess()
+            .struct_expect(
+                "this is a dummy diagnostic, to submit and store an expectation",
+                expectation,
+            )
+            .emit();
+    }
+}
+
+impl<'a> EarlyContext<'a> {
+    pub(crate) fn new(
+        sess: &'a Session,
+        warn_about_weird_lints: bool,
+        lint_store: &'a LintStore,
+        registered_tools: &'a RegisteredTools,
+        buffered: LintBuffer,
+    ) -> EarlyContext<'a> {
+        EarlyContext {
+            builder: LintLevelsBuilder::new(
+                sess,
+                warn_about_weird_lints,
+                lint_store,
+                registered_tools,
+            ),
+            buffered,
+        }
+    }
+}
+
+impl LintContext for LateContext<'_> {
+    type PassObject = LateLintPassObject;
+
+    /// Gets the overall compiler `Session` object.
+    fn sess(&self) -> &Session {
+        &self.tcx.sess
+    }
+
+    fn lints(&self) -> &LintStore {
+        &*self.lint_store
+    }
+
+    fn lookup<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: Option<S>,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        let hir_id = self.last_node_with_lint_attrs;
+
+        match span {
+            Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
+            None => self.tcx.struct_lint_node(lint, hir_id, decorate),
+        }
+    }
+
+    fn get_lint_level(&self, lint: &'static Lint) -> Level {
+        self.tcx.lint_level_at_node(lint, self.last_node_with_lint_attrs).0
+    }
+}
+
+impl LintContext for EarlyContext<'_> {
+    type PassObject = EarlyLintPassObject;
+
+    /// Gets the overall compiler `Session` object.
+    fn sess(&self) -> &Session {
+        &self.builder.sess()
+    }
+
+    fn lints(&self) -> &LintStore {
+        self.builder.lint_store()
+    }
+
+    fn lookup<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: Option<S>,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
+    }
+
+    fn get_lint_level(&self, lint: &'static Lint) -> Level {
+        self.builder.lint_level(lint).0
+    }
+}
+
+impl<'tcx> LateContext<'tcx> {
+    /// Gets the type-checking results for the current body,
+    /// or `None` if outside a body.
+    pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
+        self.cached_typeck_results.get().or_else(|| {
+            self.enclosing_body.map(|body| {
+                let typeck_results = self.tcx.typeck_body(body);
+                self.cached_typeck_results.set(Some(typeck_results));
+                typeck_results
+            })
+        })
+    }
+
+    /// Gets the type-checking results for the current body.
+    /// As this will ICE if called outside bodies, only call when working with
+    /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
+    #[track_caller]
+    pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
+        self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
+    }
+
+    /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
+    /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
+    /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
+    pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
+        match *qpath {
+            hir::QPath::Resolved(_, ref path) => path.res,
+            hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
+                .maybe_typeck_results()
+                .filter(|typeck_results| typeck_results.hir_owner == id.owner)
+                .or_else(|| {
+                    if self.tcx.has_typeck_results(id.owner.to_def_id()) {
+                        Some(self.tcx.typeck(id.owner))
+                    } else {
+                        None
+                    }
+                })
+                .and_then(|typeck_results| typeck_results.type_dependent_def(id))
+                .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
+        }
+    }
+
+    /// Check if a `DefId`'s path matches the given absolute type path usage.
+    ///
+    /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
+    /// inherent `impl` blocks are matched with the name of the type.
+    ///
+    /// Instead of using this method, it is often preferable to instead use
+    /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
+    /// as paths get invalidated if the target definition moves.
+    ///
+    /// # Examples
+    ///
+    /// ```rust,ignore (no context or def id available)
+    /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
+    ///     // The given `def_id` is that of an `Option` type
+    /// }
+    /// ```
+    ///
+    /// Used by clippy, but should be replaced by diagnostic items eventually.
+    pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
+        let names = self.get_def_path(def_id);
+
+        names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
+    }
+
+    /// Gets the absolute path of `def_id` as a vector of `Symbol`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust,ignore (no context or def id available)
+    /// let def_path = cx.get_def_path(def_id);
+    /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
+    ///     // The given `def_id` is that of an `Option` type
+    /// }
+    /// ```
+    pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
+        pub struct AbsolutePathPrinter<'tcx> {
+            pub tcx: TyCtxt<'tcx>,
+        }
+
+        impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
+            type Error = !;
+
+            type Path = Vec<Symbol>;
+            type Region = ();
+            type Type = ();
+            type DynExistential = ();
+            type Const = ();
+
+            fn tcx(&self) -> TyCtxt<'tcx> {
+                self.tcx
+            }
+
+            fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
+                Ok(())
+            }
+
+            fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
+                Ok(())
+            }
+
+            fn print_dyn_existential(
+                self,
+                _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
+            ) -> Result<Self::DynExistential, Self::Error> {
+                Ok(())
+            }
+
+            fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
+                Ok(())
+            }
+
+            fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
+                Ok(vec![self.tcx.crate_name(cnum)])
+            }
+
+            fn path_qualified(
+                self,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+            ) -> Result<Self::Path, Self::Error> {
+                if trait_ref.is_none() {
+                    if let ty::Adt(def, substs) = self_ty.kind() {
+                        return self.print_def_path(def.did(), substs);
+                    }
+                }
+
+                // This shouldn't ever be needed, but just in case:
+                with_no_trimmed_paths!({
+                    Ok(vec![match trait_ref {
+                        Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
+                        None => Symbol::intern(&format!("<{}>", self_ty)),
+                    }])
+                })
+            }
+
+            fn path_append_impl(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _disambiguated_data: &DisambiguatedDefPathData,
+                self_ty: Ty<'tcx>,
+                trait_ref: Option<ty::TraitRef<'tcx>>,
+            ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+
+                // This shouldn't ever be needed, but just in case:
+                path.push(match trait_ref {
+                    Some(trait_ref) => {
+                        with_no_trimmed_paths!(Symbol::intern(&format!(
+                            "<impl {} for {}>",
+                            trait_ref.print_only_trait_path(),
+                            self_ty
+                        )))
+                    }
+                    None => {
+                        with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
+                    }
+                });
+
+                Ok(path)
+            }
+
+            fn path_append(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                disambiguated_data: &DisambiguatedDefPathData,
+            ) -> Result<Self::Path, Self::Error> {
+                let mut path = print_prefix(self)?;
+
+                // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
+                if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
+                    return Ok(path);
+                }
+
+                path.push(Symbol::intern(&disambiguated_data.data.to_string()));
+                Ok(path)
+            }
+
+            fn path_generic_args(
+                self,
+                print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
+                _args: &[GenericArg<'tcx>],
+            ) -> Result<Self::Path, Self::Error> {
+                print_prefix(self)
+            }
+        }
+
+        AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
+    }
+}
+
+impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
+    #[inline]
+    fn data_layout(&self) -> &abi::TargetDataLayout {
+        &self.tcx.data_layout
+    }
+}
+
+impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
+    #[inline]
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+}
+
+impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
+    #[inline]
+    fn param_env(&self) -> ty::ParamEnv<'tcx> {
+        self.param_env
+    }
+}
+
+impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
+    type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
+
+    #[inline]
+    fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
+        err
+    }
+}
+
+pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
+    match lint_name.split_once("::") {
+        Some((tool_name, lint_name)) => {
+            let tool_name = Symbol::intern(tool_name);
+
+            (Some(tool_name), lint_name)
+        }
+        None => (None, lint_name),
+    }
+}
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
new file mode 100644
index 000000000..d13711c3a
--- /dev/null
+++ b/compiler/rustc_lint/src/early.rs
@@ -0,0 +1,456 @@
+//! Implementation of lint checking.
+//!
+//! The lint checking is mostly consolidated into one pass which runs
+//! after all other analyses. Throughout compilation, lint warnings
+//! can be added via the `add_lint` method on the Session structure. This
+//! requires a span and an ID of the node that the lint is being added to. The
+//! lint isn't actually emitted at that time because it is unknown what the
+//! actual lint level at that location is.
+//!
+//! To actually emit lint warnings/errors, a separate pass is used.
+//! A context keeps track of the current state of all lint levels.
+//! Upon entering a node of the ast which can modify the lint settings, the
+//! previous lint state is pushed onto a stack and the ast is then recursed
+//! upon. As the ast is traversed, this keeps track of the current lint level
+//! for all lint attributes.
+
+use crate::context::{EarlyContext, LintContext, LintStore};
+use crate::passes::{EarlyLintPass, EarlyLintPassObject};
+use rustc_ast::ptr::P;
+use rustc_ast::visit::{self as ast_visit, Visitor};
+use rustc_ast::{self as ast, walk_list, HasAttrs};
+use rustc_middle::ty::RegisteredTools;
+use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
+use rustc_session::Session;
+use rustc_span::symbol::Ident;
+use rustc_span::Span;
+
+use std::slice;
+use tracing::debug;
+
+macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
+    $cx.pass.$f(&$cx.context, $($args),*);
+}) }
+
+pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
+    context: EarlyContext<'a>,
+    pass: T,
+}
+
+impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
+    fn check_id(&mut self, id: ast::NodeId) {
+        for early_lint in self.context.buffered.take(id) {
+            let BufferedEarlyLint { span, msg, node_id: _, lint_id, diagnostic } = early_lint;
+            self.context.lookup_with_diagnostics(
+                lint_id.lint,
+                Some(span),
+                |lint| {
+                    lint.build(&msg).emit();
+                },
+                diagnostic,
+            );
+        }
+    }
+
+    /// Merge the lints specified by any lint attributes into the
+    /// current lint context, call the provided function, then reset the
+    /// lints in effect to their previous state.
+    fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let is_crate_node = id == ast::CRATE_NODE_ID;
+        let push = self.context.builder.push(attrs, is_crate_node, None);
+
+        self.check_id(id);
+        debug!("early context: enter_attrs({:?})", attrs);
+        run_early_pass!(self, enter_lint_attrs, attrs);
+        f(self);
+        debug!("early context: exit_attrs({:?})", attrs);
+        run_early_pass!(self, exit_lint_attrs, attrs);
+        self.context.builder.pop(push);
+    }
+}
+
+impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
+    fn visit_param(&mut self, param: &'a ast::Param) {
+        self.with_lint_attrs(param.id, &param.attrs, |cx| {
+            run_early_pass!(cx, check_param, param);
+            ast_visit::walk_param(cx, param);
+        });
+    }
+
+    fn visit_item(&mut self, it: &'a ast::Item) {
+        self.with_lint_attrs(it.id, &it.attrs, |cx| {
+            run_early_pass!(cx, check_item, it);
+            ast_visit::walk_item(cx, it);
+            run_early_pass!(cx, check_item_post, it);
+        })
+    }
+
+    fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
+        self.with_lint_attrs(it.id, &it.attrs, |cx| {
+            ast_visit::walk_foreign_item(cx, it);
+        })
+    }
+
+    fn visit_pat(&mut self, p: &'a ast::Pat) {
+        run_early_pass!(self, check_pat, p);
+        self.check_id(p.id);
+        ast_visit::walk_pat(self, p);
+        run_early_pass!(self, check_pat_post, p);
+    }
+
+    fn visit_anon_const(&mut self, c: &'a ast::AnonConst) {
+        self.check_id(c.id);
+        ast_visit::walk_anon_const(self, c);
+    }
+
+    fn visit_expr(&mut self, e: &'a ast::Expr) {
+        self.with_lint_attrs(e.id, &e.attrs, |cx| {
+            run_early_pass!(cx, check_expr, e);
+            ast_visit::walk_expr(cx, e);
+        })
+    }
+
+    fn visit_expr_field(&mut self, f: &'a ast::ExprField) {
+        self.with_lint_attrs(f.id, &f.attrs, |cx| {
+            ast_visit::walk_expr_field(cx, f);
+        })
+    }
+
+    fn visit_stmt(&mut self, s: &'a ast::Stmt) {
+        // Add the statement's lint attributes to our
+        // current state when checking the statement itself.
+        // This allows us to handle attributes like
+        // `#[allow(unused_doc_comments)]`, which apply to
+        // sibling attributes on the same target
+        //
+        // Note that statements get their attributes from
+        // the AST struct that they wrap (e.g. an item)
+        self.with_lint_attrs(s.id, s.attrs(), |cx| {
+            run_early_pass!(cx, check_stmt, s);
+            cx.check_id(s.id);
+        });
+        // The visitor for the AST struct wrapped
+        // by the statement (e.g. `Item`) will call
+        // `with_lint_attrs`, so do this walk
+        // outside of the above `with_lint_attrs` call
+        ast_visit::walk_stmt(self, s);
+    }
+
+    fn visit_fn(&mut self, fk: ast_visit::FnKind<'a>, span: Span, id: ast::NodeId) {
+        run_early_pass!(self, check_fn, fk, span, id);
+        self.check_id(id);
+        ast_visit::walk_fn(self, fk, span);
+
+        // Explicitly check for lints associated with 'closure_id', since
+        // it does not have a corresponding AST node
+        if let ast_visit::FnKind::Fn(_, _, sig, _, _, _) = fk {
+            if let ast::Async::Yes { closure_id, .. } = sig.header.asyncness {
+                self.check_id(closure_id);
+            }
+        }
+    }
+
+    fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
+        if let Some(ctor_hir_id) = s.ctor_id() {
+            self.check_id(ctor_hir_id);
+        }
+        ast_visit::walk_struct_def(self, s);
+    }
+
+    fn visit_field_def(&mut self, s: &'a ast::FieldDef) {
+        self.with_lint_attrs(s.id, &s.attrs, |cx| {
+            ast_visit::walk_field_def(cx, s);
+        })
+    }
+
+    fn visit_variant(&mut self, v: &'a ast::Variant) {
+        self.with_lint_attrs(v.id, &v.attrs, |cx| {
+            run_early_pass!(cx, check_variant, v);
+            ast_visit::walk_variant(cx, v);
+        })
+    }
+
+    fn visit_ty(&mut self, t: &'a ast::Ty) {
+        run_early_pass!(self, check_ty, t);
+        self.check_id(t.id);
+        ast_visit::walk_ty(self, t);
+    }
+
+    fn visit_ident(&mut self, ident: Ident) {
+        run_early_pass!(self, check_ident, ident);
+    }
+
+    fn visit_local(&mut self, l: &'a ast::Local) {
+        self.with_lint_attrs(l.id, &l.attrs, |cx| {
+            run_early_pass!(cx, check_local, l);
+            ast_visit::walk_local(cx, l);
+        })
+    }
+
+    fn visit_block(&mut self, b: &'a ast::Block) {
+        run_early_pass!(self, check_block, b);
+        self.check_id(b.id);
+        ast_visit::walk_block(self, b);
+    }
+
+    fn visit_arm(&mut self, a: &'a ast::Arm) {
+        self.with_lint_attrs(a.id, &a.attrs, |cx| {
+            run_early_pass!(cx, check_arm, a);
+            ast_visit::walk_arm(cx, a);
+        })
+    }
+
+    fn visit_expr_post(&mut self, e: &'a ast::Expr) {
+        // Explicitly check for lints associated with 'closure_id', since
+        // it does not have a corresponding AST node
+        match e.kind {
+            ast::ExprKind::Closure(_, _, ast::Async::Yes { closure_id, .. }, ..)
+            | ast::ExprKind::Async(_, closure_id, ..) => self.check_id(closure_id),
+            _ => {}
+        }
+    }
+
+    fn visit_generic_arg(&mut self, arg: &'a ast::GenericArg) {
+        run_early_pass!(self, check_generic_arg, arg);
+        ast_visit::walk_generic_arg(self, arg);
+    }
+
+    fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
+        run_early_pass!(self, check_generic_param, param);
+        self.check_id(param.id);
+        ast_visit::walk_generic_param(self, param);
+    }
+
+    fn visit_generics(&mut self, g: &'a ast::Generics) {
+        run_early_pass!(self, check_generics, g);
+        ast_visit::walk_generics(self, g);
+    }
+
+    fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
+        ast_visit::walk_where_predicate(self, p);
+    }
+
+    fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef, m: &'a ast::TraitBoundModifier) {
+        run_early_pass!(self, check_poly_trait_ref, t, m);
+        ast_visit::walk_poly_trait_ref(self, t, m);
+    }
+
+    fn visit_assoc_item(&mut self, item: &'a ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
+        self.with_lint_attrs(item.id, &item.attrs, |cx| match ctxt {
+            ast_visit::AssocCtxt::Trait => {
+                run_early_pass!(cx, check_trait_item, item);
+                ast_visit::walk_assoc_item(cx, item, ctxt);
+            }
+            ast_visit::AssocCtxt::Impl => {
+                run_early_pass!(cx, check_impl_item, item);
+                ast_visit::walk_assoc_item(cx, item, ctxt);
+            }
+        });
+    }
+
+    fn visit_lifetime(&mut self, lt: &'a ast::Lifetime, _: ast_visit::LifetimeCtxt) {
+        self.check_id(lt.id);
+    }
+
+    fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
+        self.check_id(id);
+        ast_visit::walk_path(self, p);
+    }
+
+    fn visit_path_segment(&mut self, path_span: Span, s: &'a ast::PathSegment) {
+        self.check_id(s.id);
+        ast_visit::walk_path_segment(self, path_span, s);
+    }
+
+    fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
+        run_early_pass!(self, check_attribute, attr);
+    }
+
+    fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
+        run_early_pass!(self, check_mac_def, mac, id);
+        self.check_id(id);
+    }
+
+    fn visit_mac_call(&mut self, mac: &'a ast::MacCall) {
+        run_early_pass!(self, check_mac, mac);
+        ast_visit::walk_mac(self, mac);
+    }
+}
+
+struct EarlyLintPassObjects<'a> {
+    lints: &'a mut [EarlyLintPassObject],
+}
+
+#[allow(rustc::lint_pass_impl_without_macro)]
+impl LintPass for EarlyLintPassObjects<'_> {
+    fn name(&self) -> &'static str {
+        panic!()
+    }
+}
+
+macro_rules! expand_early_lint_pass_impl_methods {
+    ([$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
+            for obj in self.lints.iter_mut() {
+                obj.$name(context, $($param),*);
+            }
+        })*
+    )
+}
+
+macro_rules! early_lint_pass_impl {
+    ([], [$($methods:tt)*]) => (
+        impl EarlyLintPass for EarlyLintPassObjects<'_> {
+            expand_early_lint_pass_impl_methods!([$($methods)*]);
+        }
+    )
+}
+
+crate::early_lint_methods!(early_lint_pass_impl, []);
+
+/// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
+/// This trait generalizes over those nodes.
+pub trait EarlyCheckNode<'a>: Copy {
+    fn id(self) -> ast::NodeId;
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b;
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b;
+}
+
+impl<'a> EarlyCheckNode<'a> for &'a ast::Crate {
+    fn id(self) -> ast::NodeId {
+        ast::CRATE_NODE_ID
+    }
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b,
+    {
+        &self.attrs
+    }
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b,
+    {
+        run_early_pass!(cx, check_crate, self);
+        ast_visit::walk_crate(cx, self);
+        run_early_pass!(cx, check_crate_post, self);
+    }
+}
+
+impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
+    fn id(self) -> ast::NodeId {
+        self.0
+    }
+    fn attrs<'b>(self) -> &'b [ast::Attribute]
+    where
+        'a: 'b,
+    {
+        self.1
+    }
+    fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
+    where
+        'a: 'b,
+    {
+        walk_list!(cx, visit_attribute, self.1);
+        walk_list!(cx, visit_item, self.2);
+    }
+}
+
+fn early_lint_node<'a>(
+    sess: &Session,
+    warn_about_weird_lints: bool,
+    lint_store: &LintStore,
+    registered_tools: &RegisteredTools,
+    buffered: LintBuffer,
+    pass: impl EarlyLintPass,
+    check_node: impl EarlyCheckNode<'a>,
+) -> LintBuffer {
+    let mut cx = EarlyContextAndPass {
+        context: EarlyContext::new(
+            sess,
+            warn_about_weird_lints,
+            lint_store,
+            registered_tools,
+            buffered,
+        ),
+        pass,
+    };
+
+    cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
+    cx.context.buffered
+}
+
+pub fn check_ast_node<'a>(
+    sess: &Session,
+    pre_expansion: bool,
+    lint_store: &LintStore,
+    registered_tools: &RegisteredTools,
+    lint_buffer: Option<LintBuffer>,
+    builtin_lints: impl EarlyLintPass,
+    check_node: impl EarlyCheckNode<'a>,
+) {
+    let passes =
+        if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
+    let mut passes: Vec<_> = passes.iter().map(|p| (p)()).collect();
+    let mut buffered = lint_buffer.unwrap_or_default();
+
+    if sess.opts.unstable_opts.no_interleave_lints {
+        for (i, pass) in passes.iter_mut().enumerate() {
+            buffered =
+                sess.prof.extra_verbose_generic_activity("run_lint", pass.name()).run(|| {
+                    early_lint_node(
+                        sess,
+                        !pre_expansion && i == 0,
+                        lint_store,
+                        registered_tools,
+                        buffered,
+                        EarlyLintPassObjects { lints: slice::from_mut(pass) },
+                        check_node,
+                    )
+                });
+        }
+    } else {
+        buffered = early_lint_node(
+            sess,
+            !pre_expansion,
+            lint_store,
+            registered_tools,
+            buffered,
+            builtin_lints,
+            check_node,
+        );
+
+        if !passes.is_empty() {
+            buffered = early_lint_node(
+                sess,
+                false,
+                lint_store,
+                registered_tools,
+                buffered,
+                EarlyLintPassObjects { lints: &mut passes[..] },
+                check_node,
+            );
+        }
+    }
+
+    // All of the buffered lints should have been emitted at this point.
+    // If not, that means that we somehow buffered a lint for a node id
+    // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
+    for (id, lints) in buffered.map {
+        for early_lint in lints {
+            sess.delay_span_bug(
+                early_lint.span,
+                &format!(
+                    "failed to process buffered lint here (dummy = {})",
+                    id == ast::DUMMY_NODE_ID
+                ),
+            );
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
new file mode 100644
index 000000000..f41ee6404
--- /dev/null
+++ b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
@@ -0,0 +1,88 @@
+use crate::{context::LintContext, LateContext, LateLintPass};
+use rustc_errors::fluent;
+use rustc_hir as hir;
+use rustc_middle::ty::{visit::TypeVisitable, Ty};
+use rustc_span::{symbol::sym, Span};
+
+declare_lint! {
+    /// The `enum_intrinsics_non_enums` lint detects calls to
+    /// intrinsic functions that require an enum ([`core::mem::discriminant`],
+    /// [`core::mem::variant_count`]), but are called with a non-enum type.
+    ///
+    /// [`core::mem::discriminant`]: https://doc.rust-lang.org/core/mem/fn.discriminant.html
+    /// [`core::mem::variant_count`]: https://doc.rust-lang.org/core/mem/fn.variant_count.html
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(enum_intrinsics_non_enums)]
+    /// core::mem::discriminant::<i32>(&123);
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In order to accept any enum, the `mem::discriminant` and
+    /// `mem::variant_count` functions are generic over a type `T`.
+    /// This makes it technically possible for `T` to be a non-enum,
+    /// in which case the return value is unspecified.
+    ///
+    /// This lint prevents such incorrect usage of these functions.
+    ENUM_INTRINSICS_NON_ENUMS,
+    Deny,
+    "detects calls to `core::mem::discriminant` and `core::mem::variant_count` with non-enum types"
+}
+
+declare_lint_pass!(EnumIntrinsicsNonEnums => [ENUM_INTRINSICS_NON_ENUMS]);
+
+/// Returns `true` if we know for sure that the given type is not an enum. Note that for cases where
+/// the type is generic, we can't be certain if it will be an enum so we have to assume that it is.
+fn is_non_enum(t: Ty<'_>) -> bool {
+    !t.is_enum() && !t.needs_subst()
+}
+
+fn enforce_mem_discriminant(
+    cx: &LateContext<'_>,
+    func_expr: &hir::Expr<'_>,
+    expr_span: Span,
+    args_span: Span,
+) {
+    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    if is_non_enum(ty_param) {
+        cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, expr_span, |builder| {
+            builder
+                .build(fluent::lint::enum_intrinsics_mem_discriminant)
+                .set_arg("ty_param", ty_param)
+                .span_note(args_span, fluent::lint::note)
+                .emit();
+        });
+    }
+}
+
+fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
+    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    if is_non_enum(ty_param) {
+        cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, span, |builder| {
+            builder
+                .build(fluent::lint::enum_intrinsics_mem_variant)
+                .set_arg("ty_param", ty_param)
+                .note(fluent::lint::note)
+                .emit();
+        });
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        let hir::ExprKind::Call(func, args) = &expr.kind else { return };
+        let hir::ExprKind::Path(qpath) = &func.kind else { return };
+        let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() else { return };
+        let Some(name) = cx.tcx.get_diagnostic_name(def_id) else { return };
+        match name {
+            sym::mem_discriminant => enforce_mem_discriminant(cx, func, expr.span, args[0].span),
+            sym::mem_variant_count => enforce_mem_variant_count(cx, func, expr.span),
+            _ => {}
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/expect.rs b/compiler/rustc_lint/src/expect.rs
new file mode 100644
index 000000000..699e81543
--- /dev/null
+++ b/compiler/rustc_lint/src/expect.rs
@@ -0,0 +1,59 @@
+use crate::builtin;
+use rustc_errors::fluent;
+use rustc_hir::HirId;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::{lint::LintExpectation, ty::TyCtxt};
+use rustc_session::lint::LintExpectationId;
+use rustc_span::symbol::sym;
+use rustc_span::Symbol;
+
+pub(crate) fn provide(providers: &mut Providers) {
+    *providers = Providers { check_expectations, ..*providers };
+}
+
+fn check_expectations(tcx: TyCtxt<'_>, tool_filter: Option<Symbol>) {
+    if !tcx.sess.features_untracked().enabled(sym::lint_reasons) {
+        return;
+    }
+
+    let fulfilled_expectations = tcx.sess.diagnostic().steal_fulfilled_expectation_ids();
+    let lint_expectations = &tcx.lint_levels(()).lint_expectations;
+
+    for (id, expectation) in lint_expectations {
+        // This check will always be true, since `lint_expectations` only
+        // holds stable ids
+        if let LintExpectationId::Stable { hir_id, .. } = id {
+            if !fulfilled_expectations.contains(&id)
+                && tool_filter.map_or(true, |filter| expectation.lint_tool == Some(filter))
+            {
+                emit_unfulfilled_expectation_lint(tcx, *hir_id, expectation);
+            }
+        } else {
+            unreachable!("at this stage all `LintExpectationId`s are stable");
+        }
+    }
+}
+
+fn emit_unfulfilled_expectation_lint(
+    tcx: TyCtxt<'_>,
+    hir_id: HirId,
+    expectation: &LintExpectation,
+) {
+    tcx.struct_span_lint_hir(
+        builtin::UNFULFILLED_LINT_EXPECTATIONS,
+        hir_id,
+        expectation.emission_span,
+        |diag| {
+            let mut diag = diag.build(fluent::lint::expectation);
+            if let Some(rationale) = expectation.reason {
+                diag.note(rationale.as_str());
+            }
+
+            if expectation.is_unfulfilled_lint_expectations {
+                diag.note(fluent::lint::note);
+            }
+
+            diag.emit();
+        },
+    );
+}
diff --git a/compiler/rustc_lint/src/hidden_unicode_codepoints.rs b/compiler/rustc_lint/src/hidden_unicode_codepoints.rs
new file mode 100644
index 000000000..fe2712525
--- /dev/null
+++ b/compiler/rustc_lint/src/hidden_unicode_codepoints.rs
@@ -0,0 +1,141 @@
+use crate::{EarlyContext, EarlyLintPass, LintContext};
+use ast::util::unicode::{contains_text_flow_control_chars, TEXT_FLOW_CONTROL_CHARS};
+use rustc_ast as ast;
+use rustc_errors::{fluent, Applicability, SuggestionStyle};
+use rustc_span::{BytePos, Span, Symbol};
+
+declare_lint! {
+    /// The `text_direction_codepoint_in_literal` lint detects Unicode codepoints that change the
+    /// visual representation of text on screen in a way that does not correspond to their on
+    /// memory representation.
+    ///
+    /// ### Explanation
+    ///
+    /// The unicode characters `\u{202A}`, `\u{202B}`, `\u{202D}`, `\u{202E}`, `\u{2066}`,
+    /// `\u{2067}`, `\u{2068}`, `\u{202C}` and `\u{2069}` make the flow of text on screen change
+    /// its direction on software that supports these codepoints. This makes the text "abc" display
+    /// as "cba" on screen. By leveraging software that supports these, people can write specially
+    /// crafted literals that make the surrounding code seem like it's performing one action, when
+    /// in reality it is performing another. Because of this, we proactively lint against their
+    /// presence to avoid surprises.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(text_direction_codepoint_in_literal)]
+    /// fn main() {
+    ///     println!("{:?}", '‮');
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    pub TEXT_DIRECTION_CODEPOINT_IN_LITERAL,
+    Deny,
+    "detect special Unicode codepoints that affect the visual representation of text on screen, \
+     changing the direction in which text flows",
+}
+
+declare_lint_pass!(HiddenUnicodeCodepoints => [TEXT_DIRECTION_CODEPOINT_IN_LITERAL]);
+
+impl HiddenUnicodeCodepoints {
+    fn lint_text_direction_codepoint(
+        &self,
+        cx: &EarlyContext<'_>,
+        text: Symbol,
+        span: Span,
+        padding: u32,
+        point_at_inner_spans: bool,
+        label: &str,
+    ) {
+        // Obtain the `Span`s for each of the forbidden chars.
+        let spans: Vec<_> = text
+            .as_str()
+            .char_indices()
+            .filter_map(|(i, c)| {
+                TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
+                    let lo = span.lo() + BytePos(i as u32 + padding);
+                    (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
+                })
+            })
+            .collect();
+
+        cx.struct_span_lint(TEXT_DIRECTION_CODEPOINT_IN_LITERAL, span, |lint| {
+            let mut err = lint.build(fluent::lint::hidden_unicode_codepoints);
+            err.set_arg("label", label);
+            err.set_arg("count", spans.len());
+            err.span_label(span, fluent::lint::label);
+            err.note(fluent::lint::note);
+            if point_at_inner_spans {
+                for (c, span) in &spans {
+                    err.span_label(*span, format!("{:?}", c));
+                }
+            }
+            if point_at_inner_spans && !spans.is_empty() {
+                err.multipart_suggestion_with_style(
+                    fluent::lint::suggestion_remove,
+                    spans.iter().map(|(_, span)| (*span, "".to_string())).collect(),
+                    Applicability::MachineApplicable,
+                    SuggestionStyle::HideCodeAlways,
+                );
+                err.multipart_suggestion(
+                    fluent::lint::suggestion_escape,
+                    spans
+                        .into_iter()
+                        .map(|(c, span)| {
+                            let c = format!("{:?}", c);
+                            (span, c[1..c.len() - 1].to_string())
+                        })
+                        .collect(),
+                    Applicability::MachineApplicable,
+                );
+            } else {
+                // FIXME: in other suggestions we've reversed the inner spans of doc comments. We
+                // should do the same here to provide the same good suggestions as we do for
+                // literals above.
+                err.set_arg(
+                    "escaped",
+                    spans
+                        .into_iter()
+                        .map(|(c, _)| format!("{:?}", c))
+                        .collect::<Vec<String>>()
+                        .join(", "),
+                );
+                err.note(fluent::lint::suggestion_remove);
+                err.note(fluent::lint::no_suggestion_note_escape);
+            }
+            err.emit();
+        });
+    }
+}
+impl EarlyLintPass for HiddenUnicodeCodepoints {
+    fn check_attribute(&mut self, cx: &EarlyContext<'_>, attr: &ast::Attribute) {
+        if let ast::AttrKind::DocComment(_, comment) = attr.kind {
+            if contains_text_flow_control_chars(comment.as_str()) {
+                self.lint_text_direction_codepoint(cx, comment, attr.span, 0, false, "doc comment");
+            }
+        }
+    }
+
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
+        // byte strings are already handled well enough by `EscapeError::NonAsciiCharInByteString`
+        let (text, span, padding) = match &expr.kind {
+            ast::ExprKind::Lit(ast::Lit { token, kind, span }) => {
+                let text = token.symbol;
+                if !contains_text_flow_control_chars(text.as_str()) {
+                    return;
+                }
+                let padding = match kind {
+                    // account for `"` or `'`
+                    ast::LitKind::Str(_, ast::StrStyle::Cooked) | ast::LitKind::Char(_) => 1,
+                    // account for `r###"`
+                    ast::LitKind::Str(_, ast::StrStyle::Raw(val)) => *val as u32 + 2,
+                    _ => return,
+                };
+                (text, span, padding)
+            }
+            _ => return,
+        };
+        self.lint_text_direction_codepoint(cx, text, *span, padding, true, "literal");
+    }
+}
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
new file mode 100644
index 000000000..c26d78247
--- /dev/null
+++ b/compiler/rustc_lint/src/internal.rs
@@ -0,0 +1,469 @@
+//! Some lints that are only useful in the compiler or crates that use compiler internals, such as
+//! Clippy.
+
+use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_errors::{fluent, Applicability};
+use rustc_hir::def::Res;
+use rustc_hir::{def_id::DefId, Expr, ExprKind, GenericArg, PatKind, Path, PathSegment, QPath};
+use rustc_hir::{HirId, Impl, Item, ItemKind, Node, Pat, Ty, TyKind};
+use rustc_middle::ty;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::hygiene::{ExpnKind, MacroKind};
+use rustc_span::symbol::{kw, sym, Symbol};
+use rustc_span::Span;
+use tracing::debug;
+
+declare_tool_lint! {
+    pub rustc::DEFAULT_HASH_TYPES,
+    Allow,
+    "forbid HashMap and HashSet and suggest the FxHash* variants",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(DefaultHashTypes => [DEFAULT_HASH_TYPES]);
+
+impl LateLintPass<'_> for DefaultHashTypes {
+    fn check_path(&mut self, cx: &LateContext<'_>, path: &Path<'_>, hir_id: HirId) {
+        let Res::Def(rustc_hir::def::DefKind::Struct, def_id) = path.res else { return };
+        if matches!(cx.tcx.hir().get(hir_id), Node::Item(Item { kind: ItemKind::Use(..), .. })) {
+            // don't lint imports, only actual usages
+            return;
+        }
+        let replace = match cx.tcx.get_diagnostic_name(def_id) {
+            Some(sym::HashMap) => "FxHashMap",
+            Some(sym::HashSet) => "FxHashSet",
+            _ => return,
+        };
+        cx.struct_span_lint(DEFAULT_HASH_TYPES, path.span, |lint| {
+            lint.build(fluent::lint::default_hash_types)
+                .set_arg("preferred", replace)
+                .set_arg("used", cx.tcx.item_name(def_id))
+                .note(fluent::lint::note)
+                .emit();
+        });
+    }
+}
+
+/// Helper function for lints that check for expressions with calls and use typeck results to
+/// get the `DefId` and `SubstsRef` of the function.
+fn typeck_results_of_method_fn<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &Expr<'_>,
+) -> Option<(Span, DefId, ty::subst::SubstsRef<'tcx>)> {
+    match expr.kind {
+        ExprKind::MethodCall(segment, _, _)
+            if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) =>
+        {
+            Some((segment.ident.span, def_id, cx.typeck_results().node_substs(expr.hir_id)))
+        },
+        _ => {
+            match cx.typeck_results().node_type(expr.hir_id).kind() {
+                &ty::FnDef(def_id, substs) => Some((expr.span, def_id, substs)),
+                _ => None,
+            }
+        }
+    }
+}
+
+declare_tool_lint! {
+    pub rustc::POTENTIAL_QUERY_INSTABILITY,
+    Allow,
+    "require explicit opt-in when using potentially unstable methods or functions",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY]);
+
+impl LateLintPass<'_> for QueryStability {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+        let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
+        if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs) {
+            let def_id = instance.def_id();
+            if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
+                cx.struct_span_lint(POTENTIAL_QUERY_INSTABILITY, span, |lint| {
+                    lint.build(fluent::lint::query_instability)
+                        .set_arg("query", cx.tcx.item_name(def_id))
+                        .note(fluent::lint::note)
+                        .emit();
+                })
+            }
+        }
+    }
+}
+
+declare_tool_lint! {
+    pub rustc::USAGE_OF_TY_TYKIND,
+    Allow,
+    "usage of `ty::TyKind` outside of the `ty::sty` module",
+    report_in_external_macro: true
+}
+
+declare_tool_lint! {
+    pub rustc::USAGE_OF_QUALIFIED_TY,
+    Allow,
+    "using `ty::{Ty,TyCtxt}` instead of importing it",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(TyTyKind => [
+    USAGE_OF_TY_TYKIND,
+    USAGE_OF_QUALIFIED_TY,
+]);
+
+impl<'tcx> LateLintPass<'tcx> for TyTyKind {
+    fn check_path(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        path: &'tcx rustc_hir::Path<'tcx>,
+        _: rustc_hir::HirId,
+    ) {
+        if let Some(segment) = path.segments.iter().nth_back(1)
+        && let Some(res) = &segment.res
+        && lint_ty_kind_usage(cx, res)
+        {
+            let span = path.span.with_hi(
+                segment.args.map_or(segment.ident.span, |a| a.span_ext).hi()
+            );
+            cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
+                lint.build(fluent::lint::tykind_kind)
+                    .span_suggestion(
+                        span,
+                        fluent::lint::suggestion,
+                        "ty",
+                        Applicability::MaybeIncorrect, // ty maybe needs an import
+                    )
+                    .emit();
+            });
+        }
+    }
+
+    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx Ty<'tcx>) {
+        match &ty.kind {
+            TyKind::Path(QPath::Resolved(_, path)) => {
+                if lint_ty_kind_usage(cx, &path.res) {
+                    cx.struct_span_lint(USAGE_OF_TY_TYKIND, path.span, |lint| {
+                        let hir = cx.tcx.hir();
+                        match hir.find(hir.get_parent_node(ty.hir_id)) {
+                            Some(Node::Pat(Pat {
+                                kind:
+                                    PatKind::Path(qpath)
+                                    | PatKind::TupleStruct(qpath, ..)
+                                    | PatKind::Struct(qpath, ..),
+                                ..
+                            })) => {
+                                if let QPath::TypeRelative(qpath_ty, ..) = qpath
+                                    && qpath_ty.hir_id == ty.hir_id
+                                {
+                                    lint.build(fluent::lint::tykind_kind)
+                                        .span_suggestion(
+                                            path.span,
+                                            fluent::lint::suggestion,
+                                            "ty",
+                                            Applicability::MaybeIncorrect, // ty maybe needs an import
+                                        )
+                                        .emit();
+                                    return;
+                                }
+                            }
+                            Some(Node::Expr(Expr {
+                                kind: ExprKind::Path(qpath),
+                                ..
+                            })) => {
+                                if let QPath::TypeRelative(qpath_ty, ..) = qpath
+                                    && qpath_ty.hir_id == ty.hir_id
+                                {
+                                    lint.build(fluent::lint::tykind_kind)
+                                        .span_suggestion(
+                                            path.span,
+                                            fluent::lint::suggestion,
+                                            "ty",
+                                            Applicability::MaybeIncorrect, // ty maybe needs an import
+                                        )
+                                        .emit();
+                                    return;
+                                }
+                            }
+                            // Can't unify these two branches because qpath below is `&&` and above is `&`
+                            // and `A | B` paths don't play well together with adjustments, apparently.
+                            Some(Node::Expr(Expr {
+                                kind: ExprKind::Struct(qpath, ..),
+                                ..
+                            })) => {
+                                if let QPath::TypeRelative(qpath_ty, ..) = qpath
+                                    && qpath_ty.hir_id == ty.hir_id
+                                {
+                                    lint.build(fluent::lint::tykind_kind)
+                                        .span_suggestion(
+                                            path.span,
+                                            fluent::lint::suggestion,
+                                            "ty",
+                                            Applicability::MaybeIncorrect, // ty maybe needs an import
+                                        )
+                                        .emit();
+                                    return;
+                                }
+                            }
+                            _ => {}
+                        }
+                        lint.build(fluent::lint::tykind).help(fluent::lint::help).emit();
+                    })
+                } else if !ty.span.from_expansion() && let Some(t) = is_ty_or_ty_ctxt(cx, &path) {
+                    if path.segments.len() > 1 {
+                        cx.struct_span_lint(USAGE_OF_QUALIFIED_TY, path.span, |lint| {
+                            lint.build(fluent::lint::ty_qualified)
+                                .set_arg("ty", t.clone())
+                                .span_suggestion(
+                                    path.span,
+                                    fluent::lint::suggestion,
+                                    t,
+                                    // The import probably needs to be changed
+                                    Applicability::MaybeIncorrect,
+                                )
+                                .emit();
+                        })
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+fn lint_ty_kind_usage(cx: &LateContext<'_>, res: &Res) -> bool {
+    if let Some(did) = res.opt_def_id() {
+        cx.tcx.is_diagnostic_item(sym::TyKind, did) || cx.tcx.is_diagnostic_item(sym::IrTyKind, did)
+    } else {
+        false
+    }
+}
+
+fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
+    match &path.res {
+        Res::Def(_, def_id) => {
+            if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(*def_id) {
+                return Some(format!("{}{}", name, gen_args(path.segments.last().unwrap())));
+            }
+        }
+        // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
+        Res::SelfTy { trait_: None, alias_to: Some((did, _)) } => {
+            if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
+                if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(adt.did())
+                {
+                    // NOTE: This path is currently unreachable as `Ty<'tcx>` is
+                    // defined as a type alias meaning that `impl<'tcx> Ty<'tcx>`
+                    // is not actually allowed.
+                    //
+                    // I(@lcnr) still kept this branch in so we don't miss this
+                    // if we ever change it in the future.
+                    return Some(format!("{}<{}>", name, substs[0]));
+                }
+            }
+        }
+        _ => (),
+    }
+
+    None
+}
+
+fn gen_args(segment: &PathSegment<'_>) -> String {
+    if let Some(args) = &segment.args {
+        let lifetimes = args
+            .args
+            .iter()
+            .filter_map(|arg| {
+                if let GenericArg::Lifetime(lt) = arg {
+                    Some(lt.name.ident().to_string())
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<_>>();
+
+        if !lifetimes.is_empty() {
+            return format!("<{}>", lifetimes.join(", "));
+        }
+    }
+
+    String::new()
+}
+
+declare_tool_lint! {
+    pub rustc::LINT_PASS_IMPL_WITHOUT_MACRO,
+    Allow,
+    "`impl LintPass` without the `declare_lint_pass!` or `impl_lint_pass!` macros"
+}
+
+declare_lint_pass!(LintPassImpl => [LINT_PASS_IMPL_WITHOUT_MACRO]);
+
+impl EarlyLintPass for LintPassImpl {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        if let ast::ItemKind::Impl(box ast::Impl { of_trait: Some(lint_pass), .. }) = &item.kind {
+            if let Some(last) = lint_pass.path.segments.last() {
+                if last.ident.name == sym::LintPass {
+                    let expn_data = lint_pass.path.span.ctxt().outer_expn_data();
+                    let call_site = expn_data.call_site;
+                    if expn_data.kind != ExpnKind::Macro(MacroKind::Bang, sym::impl_lint_pass)
+                        && call_site.ctxt().outer_expn_data().kind
+                            != ExpnKind::Macro(MacroKind::Bang, sym::declare_lint_pass)
+                    {
+                        cx.struct_span_lint(
+                            LINT_PASS_IMPL_WITHOUT_MACRO,
+                            lint_pass.path.span,
+                            |lint| {
+                                lint.build(fluent::lint::lintpass_by_hand)
+                                    .help(fluent::lint::help)
+                                    .emit();
+                            },
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+declare_tool_lint! {
+    pub rustc::EXISTING_DOC_KEYWORD,
+    Allow,
+    "Check that documented keywords in std and core actually exist",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(ExistingDocKeyword => [EXISTING_DOC_KEYWORD]);
+
+fn is_doc_keyword(s: Symbol) -> bool {
+    s <= kw::Union
+}
+
+impl<'tcx> LateLintPass<'tcx> for ExistingDocKeyword {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &rustc_hir::Item<'_>) {
+        for attr in cx.tcx.hir().attrs(item.hir_id()) {
+            if !attr.has_name(sym::doc) {
+                continue;
+            }
+            if let Some(list) = attr.meta_item_list() {
+                for nested in list {
+                    if nested.has_name(sym::keyword) {
+                        let v = nested
+                            .value_str()
+                            .expect("#[doc(keyword = \"...\")] expected a value!");
+                        if is_doc_keyword(v) {
+                            return;
+                        }
+                        cx.struct_span_lint(EXISTING_DOC_KEYWORD, attr.span, |lint| {
+                            lint.build(fluent::lint::non_existant_doc_keyword)
+                                .set_arg("keyword", v)
+                                .help(fluent::lint::help)
+                                .emit();
+                        });
+                    }
+                }
+            }
+        }
+    }
+}
+
+declare_tool_lint! {
+    pub rustc::UNTRANSLATABLE_DIAGNOSTIC,
+    Allow,
+    "prevent creation of diagnostics which cannot be translated",
+    report_in_external_macro: true
+}
+
+declare_tool_lint! {
+    pub rustc::DIAGNOSTIC_OUTSIDE_OF_IMPL,
+    Allow,
+    "prevent creation of diagnostics outside of `SessionDiagnostic`/`AddSubdiagnostic` impls",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(Diagnostics => [ UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSIDE_OF_IMPL ]);
+
+impl LateLintPass<'_> for Diagnostics {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+        let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
+        debug!(?span, ?def_id, ?substs);
+        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs)
+            .ok()
+            .and_then(|inst| inst)
+            .map(|inst| cx.tcx.has_attr(inst.def_id(), sym::rustc_lint_diagnostics))
+            .unwrap_or(false);
+        if !has_attr {
+            return;
+        }
+
+        let mut found_impl = false;
+        for (_, parent) in cx.tcx.hir().parent_iter(expr.hir_id) {
+            debug!(?parent);
+            if let Node::Item(Item { kind: ItemKind::Impl(impl_), .. }) = parent &&
+                let Impl { of_trait: Some(of_trait), .. } = impl_ &&
+                let Some(def_id) = of_trait.trait_def_id() &&
+                let Some(name) = cx.tcx.get_diagnostic_name(def_id) &&
+                matches!(name, sym::SessionDiagnostic | sym::AddSubdiagnostic | sym::DecorateLint)
+            {
+                found_impl = true;
+                break;
+            }
+        }
+        debug!(?found_impl);
+        if !found_impl {
+            cx.struct_span_lint(DIAGNOSTIC_OUTSIDE_OF_IMPL, span, |lint| {
+                lint.build(fluent::lint::diag_out_of_impl).emit();
+            })
+        }
+
+        let mut found_diagnostic_message = false;
+        for ty in substs.types() {
+            debug!(?ty);
+            if let Some(adt_def) = ty.ty_adt_def() &&
+                let Some(name) =  cx.tcx.get_diagnostic_name(adt_def.did()) &&
+                matches!(name, sym::DiagnosticMessage | sym::SubdiagnosticMessage)
+            {
+                found_diagnostic_message = true;
+                break;
+            }
+        }
+        debug!(?found_diagnostic_message);
+        if !found_diagnostic_message {
+            cx.struct_span_lint(UNTRANSLATABLE_DIAGNOSTIC, span, |lint| {
+                lint.build(fluent::lint::untranslatable_diag).emit();
+            })
+        }
+    }
+}
+
+declare_tool_lint! {
+    pub rustc::BAD_OPT_ACCESS,
+    Deny,
+    "prevent using options by field access when there is a wrapper function",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(BadOptAccess => [ BAD_OPT_ACCESS ]);
+
+impl LateLintPass<'_> for BadOptAccess {
+    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
+        let ExprKind::Field(base, target) = expr.kind else { return };
+        let Some(adt_def) = cx.typeck_results().expr_ty(base).ty_adt_def() else { return };
+        // Skip types without `#[rustc_lint_opt_ty]` - only so that the rest of the lint can be
+        // avoided.
+        if !cx.tcx.has_attr(adt_def.did(), sym::rustc_lint_opt_ty) {
+            return;
+        }
+
+        for field in adt_def.all_fields() {
+            if field.name == target.name &&
+                let Some(attr) = cx.tcx.get_attr(field.did, sym::rustc_lint_opt_deny_field_access) &&
+                let Some(items) = attr.meta_item_list()  &&
+                let Some(item) = items.first()  &&
+                let Some(literal) = item.literal()  &&
+                let ast::LitKind::Str(val, _) = literal.kind
+            {
+                cx.struct_span_lint(BAD_OPT_ACCESS, expr.span, |lint| {
+                    lint.build(val.as_str()).emit(); }
+                );
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/late.rs b/compiler/rustc_lint/src/late.rs
new file mode 100644
index 000000000..a329b3751
--- /dev/null
+++ b/compiler/rustc_lint/src/late.rs
@@ -0,0 +1,482 @@
+//! Implementation of lint checking.
+//!
+//! The lint checking is mostly consolidated into one pass which runs
+//! after all other analyses. Throughout compilation, lint warnings
+//! can be added via the `add_lint` method on the Session structure. This
+//! requires a span and an ID of the node that the lint is being added to. The
+//! lint isn't actually emitted at that time because it is unknown what the
+//! actual lint level at that location is.
+//!
+//! To actually emit lint warnings/errors, a separate pass is used.
+//! A context keeps track of the current state of all lint levels.
+//! Upon entering a node of the ast which can modify the lint settings, the
+//! previous lint state is pushed onto a stack and the ast is then recursed
+//! upon. As the ast is traversed, this keeps track of the current lint level
+//! for all lint attributes.
+
+use crate::{passes::LateLintPassObject, LateContext, LateLintPass, LintStore};
+use rustc_ast as ast;
+use rustc_data_structures::sync::join;
+use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
+use rustc_hir::intravisit as hir_visit;
+use rustc_hir::intravisit::Visitor;
+use rustc_middle::hir::nested_filter;
+use rustc_middle::ty::{self, TyCtxt};
+use rustc_session::lint::LintPass;
+use rustc_span::symbol::Symbol;
+use rustc_span::Span;
+
+use std::any::Any;
+use std::cell::Cell;
+use std::slice;
+use tracing::debug;
+
+/// Extract the `LintStore` from the query context.
+/// This function exists because we've erased `LintStore` as `dyn Any` in the context.
+pub fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
+    let store: &dyn Any = &*tcx.lint_store;
+    store.downcast_ref().unwrap()
+}
+
+macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
+    $cx.pass.$f(&$cx.context, $($args),*);
+}) }
+
+struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
+    context: LateContext<'tcx>,
+    pass: T,
+}
+
+impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
+    /// Merge the lints specified by any lint attributes into the
+    /// current lint context, call the provided function, then reset the
+    /// lints in effect to their previous state.
+    fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let attrs = self.context.tcx.hir().attrs(id);
+        let prev = self.context.last_node_with_lint_attrs;
+        self.context.last_node_with_lint_attrs = id;
+        debug!("late context: enter_attrs({:?})", attrs);
+        lint_callback!(self, enter_lint_attrs, attrs);
+        f(self);
+        debug!("late context: exit_attrs({:?})", attrs);
+        lint_callback!(self, exit_lint_attrs, attrs);
+        self.context.last_node_with_lint_attrs = prev;
+    }
+
+    fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let old_param_env = self.context.param_env;
+        self.context.param_env =
+            self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
+        f(self);
+        self.context.param_env = old_param_env;
+    }
+
+    fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
+        lint_callback!(self, check_mod, m, s, n);
+        hir_visit::walk_mod(self, m, n);
+    }
+}
+
+impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
+    type NestedFilter = nested_filter::All;
+
+    /// Because lints are scoped lexically, we want to walk nested
+    /// items in the context of the outer item, so enable
+    /// deep-walking.
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.context.tcx.hir()
+    }
+
+    fn visit_nested_body(&mut self, body_id: hir::BodyId) {
+        let old_enclosing_body = self.context.enclosing_body.replace(body_id);
+        let old_cached_typeck_results = self.context.cached_typeck_results.get();
+
+        // HACK(eddyb) avoid trashing `cached_typeck_results` when we're
+        // nested in `visit_fn`, which may have already resulted in them
+        // being queried.
+        if old_enclosing_body != Some(body_id) {
+            self.context.cached_typeck_results.set(None);
+        }
+
+        let body = self.context.tcx.hir().body(body_id);
+        self.visit_body(body);
+        self.context.enclosing_body = old_enclosing_body;
+
+        // See HACK comment above.
+        if old_enclosing_body != Some(body_id) {
+            self.context.cached_typeck_results.set(old_cached_typeck_results);
+        }
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, |cx| {
+            hir_visit::walk_param(cx, param);
+        });
+    }
+
+    fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
+        lint_callback!(self, check_body, body);
+        hir_visit::walk_body(self, body);
+        lint_callback!(self, check_body_post, body);
+    }
+
+    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = it.kind.generics();
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        let old_enclosing_body = self.context.enclosing_body.take();
+        self.with_lint_attrs(it.hir_id(), |cx| {
+            cx.with_param_env(it.hir_id(), |cx| {
+                lint_callback!(cx, check_item, it);
+                hir_visit::walk_item(cx, it);
+                lint_callback!(cx, check_item_post, it);
+            });
+        });
+        self.context.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
+        self.context.generics = generics;
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |cx| {
+            cx.with_param_env(it.hir_id(), |cx| {
+                lint_callback!(cx, check_foreign_item, it);
+                hir_visit::walk_foreign_item(cx, it);
+            });
+        })
+    }
+
+    fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
+        lint_callback!(self, check_pat, p);
+        hir_visit::walk_pat(self, p);
+    }
+
+    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
+        self.with_lint_attrs(e.hir_id, |cx| {
+            lint_callback!(cx, check_expr, e);
+            hir_visit::walk_expr(cx, e);
+            lint_callback!(cx, check_expr_post, e);
+        })
+    }
+
+    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
+        // See `EarlyContextAndPass::visit_stmt` for an explanation
+        // of why we call `walk_stmt` outside of `with_lint_attrs`
+        self.with_lint_attrs(s.hir_id, |cx| {
+            lint_callback!(cx, check_stmt, s);
+        });
+        hir_visit::walk_stmt(self, s);
+    }
+
+    fn visit_fn(
+        &mut self,
+        fk: hir_visit::FnKind<'tcx>,
+        decl: &'tcx hir::FnDecl<'tcx>,
+        body_id: hir::BodyId,
+        span: Span,
+        id: hir::HirId,
+    ) {
+        // Wrap in typeck results here, not just in visit_nested_body,
+        // in order for `check_fn` to be able to use them.
+        let old_enclosing_body = self.context.enclosing_body.replace(body_id);
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        let body = self.context.tcx.hir().body(body_id);
+        lint_callback!(self, check_fn, fk, decl, body, span, id);
+        hir_visit::walk_fn(self, fk, decl, body_id, span, id);
+        self.context.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
+    }
+
+    fn visit_variant_data(
+        &mut self,
+        s: &'tcx hir::VariantData<'tcx>,
+        _: Symbol,
+        _: &'tcx hir::Generics<'tcx>,
+        _: hir::HirId,
+        _: Span,
+    ) {
+        lint_callback!(self, check_struct_def, s);
+        hir_visit::walk_struct_def(self, s);
+    }
+
+    fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
+        self.with_lint_attrs(s.hir_id, |cx| {
+            lint_callback!(cx, check_field_def, s);
+            hir_visit::walk_field_def(cx, s);
+        })
+    }
+
+    fn visit_variant(
+        &mut self,
+        v: &'tcx hir::Variant<'tcx>,
+        g: &'tcx hir::Generics<'tcx>,
+        item_id: hir::HirId,
+    ) {
+        self.with_lint_attrs(v.id, |cx| {
+            lint_callback!(cx, check_variant, v);
+            hir_visit::walk_variant(cx, v, g, item_id);
+        })
+    }
+
+    fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
+        lint_callback!(self, check_ty, t);
+        hir_visit::walk_ty(self, t);
+    }
+
+    fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
+        hir_visit::walk_inf(self, inf);
+    }
+
+    fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
+        if !self.context.only_module {
+            self.process_mod(m, s, n);
+        }
+    }
+
+    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
+        self.with_lint_attrs(l.hir_id, |cx| {
+            lint_callback!(cx, check_local, l);
+            hir_visit::walk_local(cx, l);
+        })
+    }
+
+    fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
+        lint_callback!(self, check_block, b);
+        hir_visit::walk_block(self, b);
+        lint_callback!(self, check_block_post, b);
+    }
+
+    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
+        lint_callback!(self, check_arm, a);
+        hir_visit::walk_arm(self, a);
+    }
+
+    fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
+        lint_callback!(self, check_generic_param, p);
+        hir_visit::walk_generic_param(self, p);
+    }
+
+    fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
+        lint_callback!(self, check_generics, g);
+        hir_visit::walk_generics(self, g);
+    }
+
+    fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
+        hir_visit::walk_where_predicate(self, p);
+    }
+
+    fn visit_poly_trait_ref(
+        &mut self,
+        t: &'tcx hir::PolyTraitRef<'tcx>,
+        m: hir::TraitBoundModifier,
+    ) {
+        lint_callback!(self, check_poly_trait_ref, t, m);
+        hir_visit::walk_poly_trait_ref(self, t, m);
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = Some(&trait_item.generics);
+        self.with_lint_attrs(trait_item.hir_id(), |cx| {
+            cx.with_param_env(trait_item.hir_id(), |cx| {
+                lint_callback!(cx, check_trait_item, trait_item);
+                hir_visit::walk_trait_item(cx, trait_item);
+            });
+        });
+        self.context.generics = generics;
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
+        let generics = self.context.generics.take();
+        self.context.generics = Some(&impl_item.generics);
+        self.with_lint_attrs(impl_item.hir_id(), |cx| {
+            cx.with_param_env(impl_item.hir_id(), |cx| {
+                lint_callback!(cx, check_impl_item, impl_item);
+                hir_visit::walk_impl_item(cx, impl_item);
+                lint_callback!(cx, check_impl_item_post, impl_item);
+            });
+        });
+        self.context.generics = generics;
+    }
+
+    fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
+        hir_visit::walk_lifetime(self, lt);
+    }
+
+    fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
+        lint_callback!(self, check_path, p, id);
+        hir_visit::walk_path(self, p);
+    }
+
+    fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
+        lint_callback!(self, check_attribute, attr);
+    }
+}
+
+struct LateLintPassObjects<'a> {
+    lints: &'a mut [LateLintPassObject],
+}
+
+#[allow(rustc::lint_pass_impl_without_macro)]
+impl LintPass for LateLintPassObjects<'_> {
+    fn name(&self) -> &'static str {
+        panic!()
+    }
+}
+
+macro_rules! expand_late_lint_pass_impl_methods {
+    ([$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
+            for obj in self.lints.iter_mut() {
+                obj.$name(context, $($param),*);
+            }
+        })*
+    )
+}
+
+macro_rules! late_lint_pass_impl {
+    ([], [$hir:tt], $methods:tt) => {
+        impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_> {
+            expand_late_lint_pass_impl_methods!([$hir], $methods);
+        }
+    };
+}
+
+crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
+
+fn late_lint_mod_pass<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: LocalDefId,
+    pass: T,
+) {
+    let access_levels = &tcx.privacy_access_levels(());
+
+    let context = LateContext {
+        tcx,
+        enclosing_body: None,
+        cached_typeck_results: Cell::new(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: unerased_lint_store(tcx),
+        last_node_with_lint_attrs: tcx.hir().local_def_id_to_hir_id(module_def_id),
+        generics: None,
+        only_module: true,
+    };
+
+    let mut cx = LateContextAndPass { context, pass };
+
+    let (module, span, hir_id) = tcx.hir().get_module(module_def_id);
+    cx.process_mod(module, span, hir_id);
+
+    // Visit the crate attributes
+    if hir_id == hir::CRATE_HIR_ID {
+        for attr in tcx.hir().attrs(hir::CRATE_HIR_ID).iter() {
+            cx.visit_attribute(attr)
+        }
+    }
+}
+
+pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    module_def_id: LocalDefId,
+    builtin_lints: T,
+) {
+    if tcx.sess.opts.unstable_opts.no_interleave_lints {
+        // These passes runs in late_lint_crate with -Z no_interleave_lints
+        return;
+    }
+
+    late_lint_mod_pass(tcx, module_def_id, builtin_lints);
+
+    let mut passes: Vec<_> =
+        unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
+
+    if !passes.is_empty() {
+        late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
+    }
+}
+
+fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
+    let access_levels = &tcx.privacy_access_levels(());
+
+    let context = LateContext {
+        tcx,
+        enclosing_body: None,
+        cached_typeck_results: Cell::new(None),
+        param_env: ty::ParamEnv::empty(),
+        access_levels,
+        lint_store: unerased_lint_store(tcx),
+        last_node_with_lint_attrs: hir::CRATE_HIR_ID,
+        generics: None,
+        only_module: false,
+    };
+
+    let mut cx = LateContextAndPass { context, pass };
+
+    // Visit the whole crate.
+    cx.with_lint_attrs(hir::CRATE_HIR_ID, |cx| {
+        // since the root module isn't visited as an item (because it isn't an
+        // item), warn for it here.
+        lint_callback!(cx, check_crate,);
+        tcx.hir().walk_toplevel_module(cx);
+        tcx.hir().walk_attributes(cx);
+        lint_callback!(cx, check_crate_post,);
+    })
+}
+
+fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
+    let mut passes = unerased_lint_store(tcx).late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
+
+    if !tcx.sess.opts.unstable_opts.no_interleave_lints {
+        if !passes.is_empty() {
+            late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
+        }
+
+        late_lint_pass_crate(tcx, builtin_lints);
+    } else {
+        for pass in &mut passes {
+            tcx.sess.prof.extra_verbose_generic_activity("run_late_lint", pass.name()).run(|| {
+                late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+            });
+        }
+
+        let mut passes: Vec<_> =
+            unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
+
+        for pass in &mut passes {
+            tcx.sess.prof.extra_verbose_generic_activity("run_late_module_lint", pass.name()).run(
+                || {
+                    late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
+                },
+            );
+        }
+    }
+}
+
+/// Performs lint checking on a crate.
+pub fn check_crate<'tcx, T: LateLintPass<'tcx>>(
+    tcx: TyCtxt<'tcx>,
+    builtin_lints: impl FnOnce() -> T + Send,
+) {
+    join(
+        || {
+            tcx.sess.time("crate_lints", || {
+                // Run whole crate non-incremental lints
+                late_lint_crate(tcx, builtin_lints());
+            });
+        },
+        || {
+            tcx.sess.time("module_lints", || {
+                // Run per-module lints
+                tcx.hir().par_for_each_module(|module| tcx.ensure().lint_mod(module));
+            });
+        },
+    );
+}
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
new file mode 100644
index 000000000..00e96f20d
--- /dev/null
+++ b/compiler/rustc_lint/src/levels.rs
@@ -0,0 +1,813 @@
+use crate::context::{CheckLintNameResult, LintStore};
+use crate::late::unerased_lint_store;
+use rustc_ast as ast;
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, LintDiagnosticBuilder, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::{intravisit, HirId};
+use rustc_middle::hir::nested_filter;
+use rustc_middle::lint::{
+    struct_lint_level, LevelAndSource, LintExpectation, LintLevelMap, LintLevelSets,
+    LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
+};
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::{RegisteredTools, TyCtxt};
+use rustc_session::lint::{
+    builtin::{self, FORBIDDEN_LINT_GROUPS, SINGLE_USE_LIFETIMES, UNFULFILLED_LINT_EXPECTATIONS},
+    Level, Lint, LintExpectationId, LintId,
+};
+use rustc_session::parse::{add_feature_diagnostics, feature_err};
+use rustc_session::Session;
+use rustc_span::symbol::{sym, Symbol};
+use rustc_span::{Span, DUMMY_SP};
+use tracing::debug;
+
+fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
+    let store = unerased_lint_store(tcx);
+    let levels =
+        LintLevelsBuilder::new(tcx.sess, false, &store, &tcx.resolutions(()).registered_tools);
+    let mut builder = LintLevelMapBuilder { levels, tcx };
+    let krate = tcx.hir().krate();
+
+    builder.levels.id_to_set.reserve(krate.owners.len() + 1);
+
+    let push =
+        builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), true, Some(hir::CRATE_HIR_ID));
+
+    builder.levels.register_id(hir::CRATE_HIR_ID);
+    tcx.hir().walk_toplevel_module(&mut builder);
+    builder.levels.pop(push);
+
+    builder.levels.update_unstable_expectation_ids();
+    builder.levels.build_map()
+}
+
+pub struct LintLevelsBuilder<'s> {
+    sess: &'s Session,
+    lint_expectations: Vec<(LintExpectationId, LintExpectation)>,
+    /// Each expectation has a stable and an unstable identifier. This map
+    /// is used to map from unstable to stable [`LintExpectationId`]s.
+    expectation_id_map: FxHashMap<LintExpectationId, LintExpectationId>,
+    sets: LintLevelSets,
+    id_to_set: FxHashMap<HirId, LintStackIndex>,
+    cur: LintStackIndex,
+    warn_about_weird_lints: bool,
+    store: &'s LintStore,
+    registered_tools: &'s RegisteredTools,
+}
+
+pub struct BuilderPush {
+    prev: LintStackIndex,
+    pub changed: bool,
+}
+
+impl<'s> LintLevelsBuilder<'s> {
+    pub fn new(
+        sess: &'s Session,
+        warn_about_weird_lints: bool,
+        store: &'s LintStore,
+        registered_tools: &'s RegisteredTools,
+    ) -> Self {
+        let mut builder = LintLevelsBuilder {
+            sess,
+            lint_expectations: Default::default(),
+            expectation_id_map: Default::default(),
+            sets: LintLevelSets::new(),
+            cur: COMMAND_LINE,
+            id_to_set: Default::default(),
+            warn_about_weird_lints,
+            store,
+            registered_tools,
+        };
+        builder.process_command_line(sess, store);
+        assert_eq!(builder.sets.list.len(), 1);
+        builder
+    }
+
+    pub(crate) fn sess(&self) -> &Session {
+        self.sess
+    }
+
+    pub(crate) fn lint_store(&self) -> &LintStore {
+        self.store
+    }
+
+    fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
+        &self.sets.list[self.cur].specs
+    }
+
+    fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
+        &mut self.sets.list[self.cur].specs
+    }
+
+    fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
+        self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
+
+        self.cur =
+            self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: COMMAND_LINE });
+        for &(ref lint_name, level) in &sess.opts.lint_opts {
+            store.check_lint_name_cmdline(sess, &lint_name, level, self.registered_tools);
+            let orig_level = level;
+            let lint_flag_val = Symbol::intern(lint_name);
+
+            let Ok(ids) = store.find_lints(&lint_name) else {
+                // errors handled in check_lint_name_cmdline above
+                continue
+            };
+            for id in ids {
+                // ForceWarn and Forbid cannot be overridden
+                if let Some((Level::ForceWarn(_) | Level::Forbid, _)) =
+                    self.current_specs().get(&id)
+                {
+                    continue;
+                }
+
+                if self.check_gated_lint(id, DUMMY_SP) {
+                    let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
+                    self.current_specs_mut().insert(id, (level, src));
+                }
+            }
+        }
+    }
+
+    /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
+    /// (e.g. if a forbid was already inserted on the same scope), then emits a
+    /// diagnostic with no change to `specs`.
+    fn insert_spec(&mut self, id: LintId, (level, src): LevelAndSource) {
+        let (old_level, old_src) =
+            self.sets.get_lint_level(id.lint, self.cur, Some(self.current_specs()), &self.sess);
+        // Setting to a non-forbid level is an error if the lint previously had
+        // a forbid level. Note that this is not necessarily true even with a
+        // `#[forbid(..)]` attribute present, as that is overridden by `--cap-lints`.
+        //
+        // This means that this only errors if we're truly lowering the lint
+        // level from forbid.
+        if level != Level::Forbid {
+            if let Level::Forbid = old_level {
+                // Backwards compatibility check:
+                //
+                // We used to not consider `forbid(lint_group)`
+                // as preventing `allow(lint)` for some lint `lint` in
+                // `lint_group`. For now, issue a future-compatibility
+                // warning for this case.
+                let id_name = id.lint.name_lower();
+                let fcw_warning = match old_src {
+                    LintLevelSource::Default => false,
+                    LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
+                    LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
+                };
+                debug!(
+                    "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
+                    fcw_warning,
+                    self.current_specs(),
+                    old_src,
+                    id_name
+                );
+
+                let decorate_diag = |diag: &mut Diagnostic| {
+                    diag.span_label(src.span(), "overruled by previous forbid");
+                    match old_src {
+                        LintLevelSource::Default => {
+                            diag.note(&format!(
+                                "`forbid` lint level is the default for {}",
+                                id.to_string()
+                            ));
+                        }
+                        LintLevelSource::Node(_, forbid_source_span, reason) => {
+                            diag.span_label(forbid_source_span, "`forbid` level set here");
+                            if let Some(rationale) = reason {
+                                diag.note(rationale.as_str());
+                            }
+                        }
+                        LintLevelSource::CommandLine(_, _) => {
+                            diag.note("`forbid` lint level was set on command line");
+                        }
+                    }
+                };
+                if !fcw_warning {
+                    let mut diag_builder = struct_span_err!(
+                        self.sess,
+                        src.span(),
+                        E0453,
+                        "{}({}) incompatible with previous forbid",
+                        level.as_str(),
+                        src.name(),
+                    );
+                    decorate_diag(&mut diag_builder);
+                    diag_builder.emit();
+                } else {
+                    self.struct_lint(
+                        FORBIDDEN_LINT_GROUPS,
+                        Some(src.span().into()),
+                        |diag_builder| {
+                            let mut diag_builder = diag_builder.build(&format!(
+                                "{}({}) incompatible with previous forbid",
+                                level.as_str(),
+                                src.name(),
+                            ));
+                            decorate_diag(&mut diag_builder);
+                            diag_builder.emit();
+                        },
+                    );
+                }
+
+                // Retain the forbid lint level, unless we are
+                // issuing a FCW. In the FCW case, we want to
+                // respect the new setting.
+                if !fcw_warning {
+                    return;
+                }
+            }
+        }
+
+        // The lint `unfulfilled_lint_expectations` can't be expected, as it would suppress itself.
+        // Handling expectations of this lint would add additional complexity with little to no
+        // benefit. The expect level for this lint will therefore be ignored.
+        if let Level::Expect(_) = level && id == LintId::of(UNFULFILLED_LINT_EXPECTATIONS) {
+            return;
+        }
+
+        match (old_level, level) {
+            // If the new level is an expectation store it in `ForceWarn`
+            (Level::ForceWarn(_), Level::Expect(expectation_id)) => self
+                .current_specs_mut()
+                .insert(id, (Level::ForceWarn(Some(expectation_id)), old_src)),
+            // Keep `ForceWarn` level but drop the expectation
+            (Level::ForceWarn(_), _) => {
+                self.current_specs_mut().insert(id, (Level::ForceWarn(None), old_src))
+            }
+            // Set the lint level as normal
+            _ => self.current_specs_mut().insert(id, (level, src)),
+        };
+    }
+
+    /// Pushes a list of AST lint attributes onto this context.
+    ///
+    /// This function will return a `BuilderPush` object which should be passed
+    /// to `pop` when this scope for the attributes provided is exited.
+    ///
+    /// This function will perform a number of tasks:
+    ///
+    /// * It'll validate all lint-related attributes in `attrs`
+    /// * It'll mark all lint-related attributes as used
+    /// * Lint levels will be updated based on the attributes provided
+    /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
+    ///   `#[allow]`
+    ///
+    /// Don't forget to call `pop`!
+    pub(crate) fn push(
+        &mut self,
+        attrs: &[ast::Attribute],
+        is_crate_node: bool,
+        source_hir_id: Option<HirId>,
+    ) -> BuilderPush {
+        let prev = self.cur;
+        self.cur = self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: prev });
+
+        let sess = self.sess;
+        let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
+        for (attr_index, attr) in attrs.iter().enumerate() {
+            if attr.has_name(sym::automatically_derived) {
+                self.current_specs_mut().insert(
+                    LintId::of(SINGLE_USE_LIFETIMES),
+                    (Level::Allow, LintLevelSource::Default),
+                );
+                continue;
+            }
+
+            let level = match Level::from_attr(attr) {
+                None => continue,
+                // This is the only lint level with a `LintExpectationId` that can be created from an attribute
+                Some(Level::Expect(unstable_id)) if let Some(hir_id) = source_hir_id => {
+                    let stable_id = self.create_stable_id(unstable_id, hir_id, attr_index);
+
+                    Level::Expect(stable_id)
+                }
+                Some(lvl) => lvl,
+            };
+
+            let Some(mut metas) = attr.meta_item_list() else {
+                continue
+            };
+
+            if metas.is_empty() {
+                // This emits the unused_attributes lint for `#[level()]`
+                continue;
+            }
+
+            // Before processing the lint names, look for a reason (RFC 2383)
+            // at the end.
+            let mut reason = None;
+            let tail_li = &metas[metas.len() - 1];
+            if let Some(item) = tail_li.meta_item() {
+                match item.kind {
+                    ast::MetaItemKind::Word => {} // actual lint names handled later
+                    ast::MetaItemKind::NameValue(ref name_value) => {
+                        if item.path == sym::reason {
+                            if let ast::LitKind::Str(rationale, _) = name_value.kind {
+                                if !self.sess.features_untracked().lint_reasons {
+                                    feature_err(
+                                        &self.sess.parse_sess,
+                                        sym::lint_reasons,
+                                        item.span,
+                                        "lint reasons are experimental",
+                                    )
+                                    .emit();
+                                }
+                                reason = Some(rationale);
+                            } else {
+                                bad_attr(name_value.span)
+                                    .span_label(name_value.span, "reason must be a string literal")
+                                    .emit();
+                            }
+                            // found reason, reslice meta list to exclude it
+                            metas.pop().unwrap();
+                        } else {
+                            bad_attr(item.span)
+                                .span_label(item.span, "bad attribute argument")
+                                .emit();
+                        }
+                    }
+                    ast::MetaItemKind::List(_) => {
+                        bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
+                    }
+                }
+            }
+
+            for (lint_index, li) in metas.iter_mut().enumerate() {
+                let level = match level {
+                    Level::Expect(mut id) => {
+                        id.set_lint_index(Some(lint_index as u16));
+                        Level::Expect(id)
+                    }
+                    level => level,
+                };
+
+                let sp = li.span();
+                let meta_item = match li {
+                    ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
+                    _ => {
+                        let mut err = bad_attr(sp);
+                        let mut add_label = true;
+                        if let Some(item) = li.meta_item() {
+                            if let ast::MetaItemKind::NameValue(_) = item.kind {
+                                if item.path == sym::reason {
+                                    err.span_label(sp, "reason in lint attribute must come last");
+                                    add_label = false;
+                                }
+                            }
+                        }
+                        if add_label {
+                            err.span_label(sp, "bad attribute argument");
+                        }
+                        err.emit();
+                        continue;
+                    }
+                };
+                let tool_ident = if meta_item.path.segments.len() > 1 {
+                    Some(meta_item.path.segments.remove(0).ident)
+                } else {
+                    None
+                };
+                let tool_name = tool_ident.map(|ident| ident.name);
+                let name = pprust::path_to_string(&meta_item.path);
+                let lint_result =
+                    self.store.check_lint_name(&name, tool_name, self.registered_tools);
+                match &lint_result {
+                    CheckLintNameResult::Ok(ids) => {
+                        // This checks for instances where the user writes `#[expect(unfulfilled_lint_expectations)]`
+                        // in that case we want to avoid overriding the lint level but instead add an expectation that
+                        // can't be fulfilled. The lint message will include an explanation, that the
+                        // `unfulfilled_lint_expectations` lint can't be expected.
+                        if let Level::Expect(expect_id) = level {
+                            // The `unfulfilled_lint_expectations` lint is not part of any lint groups. Therefore. we
+                            // only need to check the slice if it contains a single lint.
+                            let is_unfulfilled_lint_expectations = match ids {
+                                [lint] => *lint == LintId::of(UNFULFILLED_LINT_EXPECTATIONS),
+                                _ => false,
+                            };
+                            self.lint_expectations.push((
+                                expect_id,
+                                LintExpectation::new(
+                                    reason,
+                                    sp,
+                                    is_unfulfilled_lint_expectations,
+                                    tool_name,
+                                ),
+                            ));
+                        }
+                        let src = LintLevelSource::Node(
+                            meta_item.path.segments.last().expect("empty lint name").ident.name,
+                            sp,
+                            reason,
+                        );
+                        for &id in *ids {
+                            if self.check_gated_lint(id, attr.span) {
+                                self.insert_spec(id, (level, src));
+                            }
+                        }
+                    }
+
+                    CheckLintNameResult::Tool(result) => {
+                        match *result {
+                            Ok(ids) => {
+                                let complete_name =
+                                    &format!("{}::{}", tool_ident.unwrap().name, name);
+                                let src = LintLevelSource::Node(
+                                    Symbol::intern(complete_name),
+                                    sp,
+                                    reason,
+                                );
+                                for id in ids {
+                                    self.insert_spec(*id, (level, src));
+                                }
+                                if let Level::Expect(expect_id) = level {
+                                    self.lint_expectations.push((
+                                        expect_id,
+                                        LintExpectation::new(reason, sp, false, tool_name),
+                                    ));
+                                }
+                            }
+                            Err((Some(ids), ref new_lint_name)) => {
+                                let lint = builtin::RENAMED_AND_REMOVED_LINTS;
+                                let (lvl, src) = self.sets.get_lint_level(
+                                    lint,
+                                    self.cur,
+                                    Some(self.current_specs()),
+                                    &sess,
+                                );
+                                struct_lint_level(
+                                    self.sess,
+                                    lint,
+                                    lvl,
+                                    src,
+                                    Some(sp.into()),
+                                    |lint| {
+                                        let msg = format!(
+                                            "lint name `{}` is deprecated \
+                                             and may not have an effect in the future.",
+                                            name
+                                        );
+                                        lint.build(&msg)
+                                            .span_suggestion(
+                                                sp,
+                                                "change it to",
+                                                new_lint_name,
+                                                Applicability::MachineApplicable,
+                                            )
+                                            .emit();
+                                    },
+                                );
+
+                                let src = LintLevelSource::Node(
+                                    Symbol::intern(&new_lint_name),
+                                    sp,
+                                    reason,
+                                );
+                                for id in ids {
+                                    self.insert_spec(*id, (level, src));
+                                }
+                                if let Level::Expect(expect_id) = level {
+                                    self.lint_expectations.push((
+                                        expect_id,
+                                        LintExpectation::new(reason, sp, false, tool_name),
+                                    ));
+                                }
+                            }
+                            Err((None, _)) => {
+                                // If Tool(Err(None, _)) is returned, then either the lint does not
+                                // exist in the tool or the code was not compiled with the tool and
+                                // therefore the lint was never added to the `LintStore`. To detect
+                                // this is the responsibility of the lint tool.
+                            }
+                        }
+                    }
+
+                    &CheckLintNameResult::NoTool => {
+                        let mut err = struct_span_err!(
+                            sess,
+                            tool_ident.map_or(DUMMY_SP, |ident| ident.span),
+                            E0710,
+                            "unknown tool name `{}` found in scoped lint: `{}::{}`",
+                            tool_name.unwrap(),
+                            tool_name.unwrap(),
+                            pprust::path_to_string(&meta_item.path),
+                        );
+                        if sess.is_nightly_build() {
+                            err.help(&format!(
+                                "add `#![register_tool({})]` to the crate root",
+                                tool_name.unwrap()
+                            ));
+                        }
+                        err.emit();
+                        continue;
+                    }
+
+                    _ if !self.warn_about_weird_lints => {}
+
+                    CheckLintNameResult::Warning(msg, renamed) => {
+                        let lint = builtin::RENAMED_AND_REMOVED_LINTS;
+                        let (renamed_lint_level, src) = self.sets.get_lint_level(
+                            lint,
+                            self.cur,
+                            Some(self.current_specs()),
+                            &sess,
+                        );
+                        struct_lint_level(
+                            self.sess,
+                            lint,
+                            renamed_lint_level,
+                            src,
+                            Some(sp.into()),
+                            |lint| {
+                                let mut err = lint.build(msg);
+                                if let Some(new_name) = &renamed {
+                                    err.span_suggestion(
+                                        sp,
+                                        "use the new name",
+                                        new_name,
+                                        Applicability::MachineApplicable,
+                                    );
+                                }
+                                err.emit();
+                            },
+                        );
+                    }
+                    CheckLintNameResult::NoLint(suggestion) => {
+                        let lint = builtin::UNKNOWN_LINTS;
+                        let (level, src) = self.sets.get_lint_level(
+                            lint,
+                            self.cur,
+                            Some(self.current_specs()),
+                            self.sess,
+                        );
+                        struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
+                            let name = if let Some(tool_ident) = tool_ident {
+                                format!("{}::{}", tool_ident.name, name)
+                            } else {
+                                name.to_string()
+                            };
+                            let mut db = lint.build(format!("unknown lint: `{}`", name));
+                            if let Some(suggestion) = suggestion {
+                                db.span_suggestion(
+                                    sp,
+                                    "did you mean",
+                                    suggestion,
+                                    Applicability::MachineApplicable,
+                                );
+                            }
+                            db.emit();
+                        });
+                    }
+                }
+                // If this lint was renamed, apply the new lint instead of ignoring the attribute.
+                // This happens outside of the match because the new lint should be applied even if
+                // we don't warn about the name change.
+                if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
+                    // Ignore any errors or warnings that happen because the new name is inaccurate
+                    // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
+                    if let CheckLintNameResult::Ok(ids) =
+                        self.store.check_lint_name(&new_name, None, self.registered_tools)
+                    {
+                        let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
+                        for &id in ids {
+                            if self.check_gated_lint(id, attr.span) {
+                                self.insert_spec(id, (level, src));
+                            }
+                        }
+                        if let Level::Expect(expect_id) = level {
+                            self.lint_expectations.push((
+                                expect_id,
+                                LintExpectation::new(reason, sp, false, tool_name),
+                            ));
+                        }
+                    } else {
+                        panic!("renamed lint does not exist: {}", new_name);
+                    }
+                }
+            }
+        }
+
+        if !is_crate_node {
+            for (id, &(level, ref src)) in self.current_specs().iter() {
+                if !id.lint.crate_level_only {
+                    continue;
+                }
+
+                let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
+                    continue
+                };
+
+                let lint = builtin::UNUSED_ATTRIBUTES;
+                let (lint_level, lint_src) =
+                    self.sets.get_lint_level(lint, self.cur, Some(self.current_specs()), self.sess);
+                struct_lint_level(
+                    self.sess,
+                    lint,
+                    lint_level,
+                    lint_src,
+                    Some(lint_attr_span.into()),
+                    |lint| {
+                        let mut db = lint.build(&format!(
+                            "{}({}) is ignored unless specified at crate level",
+                            level.as_str(),
+                            lint_attr_name
+                        ));
+                        db.emit();
+                    },
+                );
+                // don't set a separate error for every lint in the group
+                break;
+            }
+        }
+
+        if self.current_specs().is_empty() {
+            self.sets.list.pop();
+            self.cur = prev;
+        }
+
+        BuilderPush { prev, changed: prev != self.cur }
+    }
+
+    fn create_stable_id(
+        &mut self,
+        unstable_id: LintExpectationId,
+        hir_id: HirId,
+        attr_index: usize,
+    ) -> LintExpectationId {
+        let stable_id =
+            LintExpectationId::Stable { hir_id, attr_index: attr_index as u16, lint_index: None };
+
+        self.expectation_id_map.insert(unstable_id, stable_id);
+
+        stable_id
+    }
+
+    /// Checks if the lint is gated on a feature that is not enabled.
+    ///
+    /// Returns `true` if the lint's feature is enabled.
+    fn check_gated_lint(&self, lint_id: LintId, span: Span) -> bool {
+        if let Some(feature) = lint_id.lint.feature_gate {
+            if !self.sess.features_untracked().enabled(feature) {
+                let lint = builtin::UNKNOWN_LINTS;
+                let (level, src) = self.lint_level(builtin::UNKNOWN_LINTS);
+                struct_lint_level(self.sess, lint, level, src, Some(span.into()), |lint_db| {
+                    let mut db =
+                        lint_db.build(&format!("unknown lint: `{}`", lint_id.lint.name_lower()));
+                    db.note(&format!("the `{}` lint is unstable", lint_id.lint.name_lower(),));
+                    add_feature_diagnostics(&mut db, &self.sess.parse_sess, feature);
+                    db.emit();
+                });
+                return false;
+            }
+        }
+        true
+    }
+
+    /// Called after `push` when the scope of a set of attributes are exited.
+    pub fn pop(&mut self, push: BuilderPush) {
+        self.cur = push.prev;
+    }
+
+    /// Find the lint level for a lint.
+    pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
+        self.sets.get_lint_level(lint, self.cur, None, self.sess)
+    }
+
+    /// Used to emit a lint-related diagnostic based on the current state of
+    /// this lint context.
+    pub fn struct_lint(
+        &self,
+        lint: &'static Lint,
+        span: Option<MultiSpan>,
+        decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
+    ) {
+        let (level, src) = self.lint_level(lint);
+        struct_lint_level(self.sess, lint, level, src, span, decorate)
+    }
+
+    /// Registers the ID provided with the current set of lints stored in
+    /// this context.
+    pub fn register_id(&mut self, id: HirId) {
+        self.id_to_set.insert(id, self.cur);
+    }
+
+    fn update_unstable_expectation_ids(&self) {
+        self.sess.diagnostic().update_unstable_expectation_id(&self.expectation_id_map);
+    }
+
+    pub fn build_map(self) -> LintLevelMap {
+        LintLevelMap {
+            sets: self.sets,
+            id_to_set: self.id_to_set,
+            lint_expectations: self.lint_expectations,
+        }
+    }
+}
+
+struct LintLevelMapBuilder<'tcx> {
+    levels: LintLevelsBuilder<'tcx>,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl LintLevelMapBuilder<'_> {
+    fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
+    where
+        F: FnOnce(&mut Self),
+    {
+        let is_crate_hir = id == hir::CRATE_HIR_ID;
+        let attrs = self.tcx.hir().attrs(id);
+        let push = self.levels.push(attrs, is_crate_hir, Some(id));
+
+        if push.changed {
+            self.levels.register_id(id);
+        }
+        f(self);
+        self.levels.pop(push);
+    }
+}
+
+impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
+    type NestedFilter = nested_filter::All;
+
+    fn nested_visit_map(&mut self) -> Self::Map {
+        self.tcx.hir()
+    }
+
+    fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
+        self.with_lint_attrs(param.hir_id, |builder| {
+            intravisit::walk_param(builder, param);
+        });
+    }
+
+    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |builder| {
+            intravisit::walk_item(builder, it);
+        });
+    }
+
+    fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
+        self.with_lint_attrs(it.hir_id(), |builder| {
+            intravisit::walk_foreign_item(builder, it);
+        })
+    }
+
+    fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
+        // We will call `with_lint_attrs` when we walk
+        // the `StmtKind`. The outer statement itself doesn't
+        // define the lint levels.
+        intravisit::walk_stmt(self, e);
+    }
+
+    fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
+        self.with_lint_attrs(e.hir_id, |builder| {
+            intravisit::walk_expr(builder, e);
+        })
+    }
+
+    fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
+        self.with_lint_attrs(s.hir_id, |builder| {
+            intravisit::walk_field_def(builder, s);
+        })
+    }
+
+    fn visit_variant(
+        &mut self,
+        v: &'tcx hir::Variant<'tcx>,
+        g: &'tcx hir::Generics<'tcx>,
+        item_id: hir::HirId,
+    ) {
+        self.with_lint_attrs(v.id, |builder| {
+            intravisit::walk_variant(builder, v, g, item_id);
+        })
+    }
+
+    fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
+        self.with_lint_attrs(l.hir_id, |builder| {
+            intravisit::walk_local(builder, l);
+        })
+    }
+
+    fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
+        self.with_lint_attrs(a.hir_id, |builder| {
+            intravisit::walk_arm(builder, a);
+        })
+    }
+
+    fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
+        self.with_lint_attrs(trait_item.hir_id(), |builder| {
+            intravisit::walk_trait_item(builder, trait_item);
+        });
+    }
+
+    fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
+        self.with_lint_attrs(impl_item.hir_id(), |builder| {
+            intravisit::walk_impl_item(builder, impl_item);
+        });
+    }
+}
+
+pub fn provide(providers: &mut Providers) {
+    providers.lint_levels = lint_levels;
+}
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
new file mode 100644
index 000000000..389a0b5d1
--- /dev/null
+++ b/compiler/rustc_lint/src/lib.rs
@@ -0,0 +1,538 @@
+//! Lints, aka compiler warnings.
+//!
+//! A 'lint' check is a kind of miscellaneous constraint that a user _might_
+//! want to enforce, but might reasonably want to permit as well, on a
+//! module-by-module basis. They contrast with static constraints enforced by
+//! other phases of the compiler, which are generally required to hold in order
+//! to compile the program at all.
+//!
+//! Most lints can be written as [LintPass] instances. These run after
+//! all other analyses. The `LintPass`es built into rustc are defined
+//! within [rustc_session::lint::builtin],
+//! which has further comments on how to add such a lint.
+//! rustc can also load user-defined lint plugins via the plugin mechanism.
+//!
+//! Some of rustc's lints are defined elsewhere in the compiler and work by
+//! calling `add_lint()` on the overall `Session` object. This works when
+//! it happens before the main lint pass, which emits the lints stored by
+//! `add_lint()`. To emit lints after the main lint pass (from codegen, for
+//! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
+//! in `context.rs`.
+//!
+//! Some code also exists in [rustc_session::lint], [rustc_middle::lint].
+//!
+//! ## Note
+//!
+//! This API is completely unstable and subject to change.
+
+#![allow(rustc::potential_query_instability)]
+#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
+#![feature(array_windows)]
+#![feature(box_patterns)]
+#![feature(control_flow_enum)]
+#![feature(if_let_guard)]
+#![feature(iter_intersperse)]
+#![feature(iter_order_by)]
+#![feature(let_chains)]
+#![feature(let_else)]
+#![feature(never_type)]
+#![recursion_limit = "256"]
+
+#[macro_use]
+extern crate rustc_middle;
+#[macro_use]
+extern crate rustc_session;
+
+mod array_into_iter;
+pub mod builtin;
+mod context;
+mod early;
+mod enum_intrinsics_non_enums;
+mod expect;
+pub mod hidden_unicode_codepoints;
+mod internal;
+mod late;
+mod levels;
+mod methods;
+mod non_ascii_idents;
+mod non_fmt_panic;
+mod nonstandard_style;
+mod noop_method_call;
+mod pass_by_value;
+mod passes;
+mod redundant_semicolon;
+mod traits;
+mod types;
+mod unused;
+
+pub use array_into_iter::ARRAY_INTO_ITER;
+
+use rustc_ast as ast;
+use rustc_hir as hir;
+use rustc_hir::def_id::LocalDefId;
+use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::TyCtxt;
+use rustc_session::lint::builtin::{
+    BARE_TRAIT_OBJECTS, ELIDED_LIFETIMES_IN_PATHS, EXPLICIT_OUTLIVES_REQUIREMENTS,
+};
+use rustc_span::symbol::Ident;
+use rustc_span::Span;
+
+use array_into_iter::ArrayIntoIter;
+use builtin::*;
+use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
+use hidden_unicode_codepoints::*;
+use internal::*;
+use methods::*;
+use non_ascii_idents::*;
+use non_fmt_panic::NonPanicFmt;
+use nonstandard_style::*;
+use noop_method_call::*;
+use pass_by_value::*;
+use redundant_semicolon::*;
+use traits::*;
+use types::*;
+use unused::*;
+
+/// Useful for other parts of the compiler / Clippy.
+pub use builtin::SoftLints;
+pub use context::{CheckLintNameResult, FindLintError, LintStore};
+pub use context::{EarlyContext, LateContext, LintContext};
+pub use early::{check_ast_node, EarlyCheckNode};
+pub use late::{check_crate, unerased_lint_store};
+pub use passes::{EarlyLintPass, LateLintPass};
+pub use rustc_session::lint::Level::{self, *};
+pub use rustc_session::lint::{BufferedEarlyLint, FutureIncompatibleInfo, Lint, LintId};
+pub use rustc_session::lint::{LintArray, LintPass};
+
+pub fn provide(providers: &mut Providers) {
+    levels::provide(providers);
+    expect::provide(providers);
+    *providers = Providers { lint_mod, ..*providers };
+}
+
+fn lint_mod(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
+    late::late_lint_mod(tcx, module_def_id, BuiltinCombinedModuleLateLintPass::new());
+}
+
+macro_rules! pre_expansion_lint_passes {
+    ($macro:path, $args:tt) => {
+        $macro!($args, [KeywordIdents: KeywordIdents,]);
+    };
+}
+
+macro_rules! early_lint_passes {
+    ($macro:path, $args:tt) => {
+        $macro!(
+            $args,
+            [
+                UnusedParens: UnusedParens,
+                UnusedBraces: UnusedBraces,
+                UnusedImportBraces: UnusedImportBraces,
+                UnsafeCode: UnsafeCode,
+                AnonymousParameters: AnonymousParameters,
+                EllipsisInclusiveRangePatterns: EllipsisInclusiveRangePatterns::default(),
+                NonCamelCaseTypes: NonCamelCaseTypes,
+                DeprecatedAttr: DeprecatedAttr::new(),
+                WhileTrue: WhileTrue,
+                NonAsciiIdents: NonAsciiIdents,
+                HiddenUnicodeCodepoints: HiddenUnicodeCodepoints,
+                IncompleteFeatures: IncompleteFeatures,
+                RedundantSemicolons: RedundantSemicolons,
+                UnusedDocComment: UnusedDocComment,
+            ]
+        );
+    };
+}
+
+macro_rules! declare_combined_early_pass {
+    ([$name:ident], $passes:tt) => (
+        early_lint_methods!(declare_combined_early_lint_pass, [pub $name, $passes]);
+    )
+}
+
+pre_expansion_lint_passes!(declare_combined_early_pass, [BuiltinCombinedPreExpansionLintPass]);
+early_lint_passes!(declare_combined_early_pass, [BuiltinCombinedEarlyLintPass]);
+
+macro_rules! late_lint_passes {
+    ($macro:path, $args:tt) => {
+        $macro!(
+            $args,
+            [
+                // Tracks state across modules
+                UnnameableTestItems: UnnameableTestItems::new(),
+                // Tracks attributes of parents
+                MissingDoc: MissingDoc::new(),
+                // Builds a global list of all impls of `Debug`.
+                // FIXME: Turn the computation of types which implement Debug into a query
+                // and change this to a module lint pass
+                MissingDebugImplementations: MissingDebugImplementations::default(),
+                // Keeps a global list of foreign declarations.
+                ClashingExternDeclarations: ClashingExternDeclarations::new(),
+            ]
+        );
+    };
+}
+
+macro_rules! late_lint_mod_passes {
+    ($macro:path, $args:tt) => {
+        $macro!(
+            $args,
+            [
+                HardwiredLints: HardwiredLints,
+                ImproperCTypesDeclarations: ImproperCTypesDeclarations,
+                ImproperCTypesDefinitions: ImproperCTypesDefinitions,
+                VariantSizeDifferences: VariantSizeDifferences,
+                BoxPointers: BoxPointers,
+                PathStatements: PathStatements,
+                // Depends on referenced function signatures in expressions
+                UnusedResults: UnusedResults,
+                NonUpperCaseGlobals: NonUpperCaseGlobals,
+                NonShorthandFieldPatterns: NonShorthandFieldPatterns,
+                UnusedAllocation: UnusedAllocation,
+                // Depends on types used in type definitions
+                MissingCopyImplementations: MissingCopyImplementations,
+                // Depends on referenced function signatures in expressions
+                MutableTransmutes: MutableTransmutes,
+                TypeAliasBounds: TypeAliasBounds,
+                TrivialConstraints: TrivialConstraints,
+                TypeLimits: TypeLimits::new(),
+                NonSnakeCase: NonSnakeCase,
+                InvalidNoMangleItems: InvalidNoMangleItems,
+                // Depends on access levels
+                UnreachablePub: UnreachablePub,
+                ExplicitOutlivesRequirements: ExplicitOutlivesRequirements,
+                InvalidValue: InvalidValue,
+                DerefNullPtr: DerefNullPtr,
+                // May Depend on constants elsewhere
+                UnusedBrokenConst: UnusedBrokenConst,
+                UnstableFeatures: UnstableFeatures,
+                ArrayIntoIter: ArrayIntoIter::default(),
+                DropTraitConstraints: DropTraitConstraints,
+                TemporaryCStringAsPtr: TemporaryCStringAsPtr,
+                NonPanicFmt: NonPanicFmt,
+                NoopMethodCall: NoopMethodCall,
+                EnumIntrinsicsNonEnums: EnumIntrinsicsNonEnums,
+                InvalidAtomicOrdering: InvalidAtomicOrdering,
+                NamedAsmLabels: NamedAsmLabels,
+            ]
+        );
+    };
+}
+
+macro_rules! declare_combined_late_pass {
+    ([$v:vis $name:ident], $passes:tt) => (
+        late_lint_methods!(declare_combined_late_lint_pass, [$v $name, $passes], ['tcx]);
+    )
+}
+
+// FIXME: Make a separate lint type which do not require typeck tables
+late_lint_passes!(declare_combined_late_pass, [pub BuiltinCombinedLateLintPass]);
+
+late_lint_mod_passes!(declare_combined_late_pass, [BuiltinCombinedModuleLateLintPass]);
+
+pub fn new_lint_store(no_interleave_lints: bool, internal_lints: bool) -> LintStore {
+    let mut lint_store = LintStore::new();
+
+    register_builtins(&mut lint_store, no_interleave_lints);
+    if internal_lints {
+        register_internals(&mut lint_store);
+    }
+
+    lint_store
+}
+
+/// Tell the `LintStore` about all the built-in lints (the ones
+/// defined in this crate and the ones defined in
+/// `rustc_session::lint::builtin`).
+fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
+    macro_rules! add_lint_group {
+        ($name:expr, $($lint:ident),*) => (
+            store.register_group(false, $name, None, vec![$(LintId::of($lint)),*]);
+        )
+    }
+
+    macro_rules! register_pass {
+        ($method:ident, $ty:ident, $constructor:expr) => {
+            store.register_lints(&$ty::get_lints());
+            store.$method(|| Box::new($constructor));
+        };
+    }
+
+    macro_rules! register_passes {
+        ($method:ident, [$($passes:ident: $constructor:expr,)*]) => (
+            $(
+                register_pass!($method, $passes, $constructor);
+            )*
+        )
+    }
+
+    if no_interleave_lints {
+        pre_expansion_lint_passes!(register_passes, register_pre_expansion_pass);
+        early_lint_passes!(register_passes, register_early_pass);
+        late_lint_passes!(register_passes, register_late_pass);
+        late_lint_mod_passes!(register_passes, register_late_mod_pass);
+    } else {
+        store.register_lints(&BuiltinCombinedPreExpansionLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedEarlyLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedModuleLateLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedLateLintPass::get_lints());
+    }
+
+    add_lint_group!(
+        "nonstandard_style",
+        NON_CAMEL_CASE_TYPES,
+        NON_SNAKE_CASE,
+        NON_UPPER_CASE_GLOBALS
+    );
+
+    add_lint_group!(
+        "unused",
+        UNUSED_IMPORTS,
+        UNUSED_VARIABLES,
+        UNUSED_ASSIGNMENTS,
+        DEAD_CODE,
+        UNUSED_MUT,
+        UNREACHABLE_CODE,
+        UNREACHABLE_PATTERNS,
+        UNUSED_MUST_USE,
+        UNUSED_UNSAFE,
+        PATH_STATEMENTS,
+        UNUSED_ATTRIBUTES,
+        UNUSED_MACROS,
+        UNUSED_MACRO_RULES,
+        UNUSED_ALLOCATION,
+        UNUSED_DOC_COMMENTS,
+        UNUSED_EXTERN_CRATES,
+        UNUSED_FEATURES,
+        UNUSED_LABELS,
+        UNUSED_PARENS,
+        UNUSED_BRACES,
+        REDUNDANT_SEMICOLONS
+    );
+
+    add_lint_group!(
+        "rust_2018_idioms",
+        BARE_TRAIT_OBJECTS,
+        UNUSED_EXTERN_CRATES,
+        ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
+        ELIDED_LIFETIMES_IN_PATHS,
+        EXPLICIT_OUTLIVES_REQUIREMENTS // FIXME(#52665, #47816) not always applicable and not all
+                                       // macros are ready for this yet.
+                                       // UNREACHABLE_PUB,
+
+                                       // FIXME macro crates are not up for this yet, too much
+                                       // breakage is seen if we try to encourage this lint.
+                                       // MACRO_USE_EXTERN_CRATE
+    );
+
+    // Register renamed and removed lints.
+    store.register_renamed("single_use_lifetime", "single_use_lifetimes");
+    store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");
+    store.register_renamed("bare_trait_object", "bare_trait_objects");
+    store.register_renamed("unstable_name_collision", "unstable_name_collisions");
+    store.register_renamed("unused_doc_comment", "unused_doc_comments");
+    store.register_renamed("async_idents", "keyword_idents");
+    store.register_renamed("exceeding_bitshifts", "arithmetic_overflow");
+    store.register_renamed("redundant_semicolon", "redundant_semicolons");
+    store.register_renamed("overlapping_patterns", "overlapping_range_endpoints");
+    store.register_renamed("safe_packed_borrows", "unaligned_references");
+    store.register_renamed("disjoint_capture_migration", "rust_2021_incompatible_closure_captures");
+    store.register_renamed("or_patterns_back_compat", "rust_2021_incompatible_or_patterns");
+    store.register_renamed("non_fmt_panic", "non_fmt_panics");
+
+    // These were moved to tool lints, but rustc still sees them when compiling normally, before
+    // tool lints are registered, so `check_tool_name_for_backwards_compat` doesn't work. Use
+    // `register_removed` explicitly.
+    const RUSTDOC_LINTS: &[&str] = &[
+        "broken_intra_doc_links",
+        "private_intra_doc_links",
+        "missing_crate_level_docs",
+        "missing_doc_code_examples",
+        "private_doc_tests",
+        "invalid_codeblock_attributes",
+        "invalid_html_tags",
+        "non_autolinks",
+    ];
+    for rustdoc_lint in RUSTDOC_LINTS {
+        store.register_ignored(rustdoc_lint);
+    }
+    store.register_removed(
+        "intra_doc_link_resolution_failure",
+        "use `rustdoc::broken_intra_doc_links` instead",
+    );
+    store.register_removed("rustdoc", "use `rustdoc::all` instead");
+
+    store.register_removed("unknown_features", "replaced by an error");
+    store.register_removed("unsigned_negation", "replaced by negate_unsigned feature gate");
+    store.register_removed("negate_unsigned", "cast a signed value instead");
+    store.register_removed("raw_pointer_derive", "using derive with raw pointers is ok");
+    // Register lint group aliases.
+    store.register_group_alias("nonstandard_style", "bad_style");
+    // This was renamed to `raw_pointer_derive`, which was then removed,
+    // so it is also considered removed.
+    store.register_removed("raw_pointer_deriving", "using derive with raw pointers is ok");
+    store.register_removed("drop_with_repr_extern", "drop flags have been removed");
+    store.register_removed("fat_ptr_transmutes", "was accidentally removed back in 2014");
+    store.register_removed("deprecated_attr", "use `deprecated` instead");
+    store.register_removed(
+        "transmute_from_fn_item_types",
+        "always cast functions before transmuting them",
+    );
+    store.register_removed(
+        "hr_lifetime_in_assoc_type",
+        "converted into hard error, see issue #33685 \
+         <https://github.com/rust-lang/rust/issues/33685> for more information",
+    );
+    store.register_removed(
+        "inaccessible_extern_crate",
+        "converted into hard error, see issue #36886 \
+         <https://github.com/rust-lang/rust/issues/36886> for more information",
+    );
+    store.register_removed(
+        "super_or_self_in_global_path",
+        "converted into hard error, see issue #36888 \
+         <https://github.com/rust-lang/rust/issues/36888> for more information",
+    );
+    store.register_removed(
+        "overlapping_inherent_impls",
+        "converted into hard error, see issue #36889 \
+         <https://github.com/rust-lang/rust/issues/36889> for more information",
+    );
+    store.register_removed(
+        "illegal_floating_point_constant_pattern",
+        "converted into hard error, see issue #36890 \
+         <https://github.com/rust-lang/rust/issues/36890> for more information",
+    );
+    store.register_removed(
+        "illegal_struct_or_enum_constant_pattern",
+        "converted into hard error, see issue #36891 \
+         <https://github.com/rust-lang/rust/issues/36891> for more information",
+    );
+    store.register_removed(
+        "lifetime_underscore",
+        "converted into hard error, see issue #36892 \
+         <https://github.com/rust-lang/rust/issues/36892> for more information",
+    );
+    store.register_removed(
+        "extra_requirement_in_impl",
+        "converted into hard error, see issue #37166 \
+         <https://github.com/rust-lang/rust/issues/37166> for more information",
+    );
+    store.register_removed(
+        "legacy_imports",
+        "converted into hard error, see issue #38260 \
+         <https://github.com/rust-lang/rust/issues/38260> for more information",
+    );
+    store.register_removed(
+        "coerce_never",
+        "converted into hard error, see issue #48950 \
+         <https://github.com/rust-lang/rust/issues/48950> for more information",
+    );
+    store.register_removed(
+        "resolve_trait_on_defaulted_unit",
+        "converted into hard error, see issue #48950 \
+         <https://github.com/rust-lang/rust/issues/48950> for more information",
+    );
+    store.register_removed(
+        "private_no_mangle_fns",
+        "no longer a warning, `#[no_mangle]` functions always exported",
+    );
+    store.register_removed(
+        "private_no_mangle_statics",
+        "no longer a warning, `#[no_mangle]` statics always exported",
+    );
+    store.register_removed("bad_repr", "replaced with a generic attribute input check");
+    store.register_removed(
+        "duplicate_matcher_binding_name",
+        "converted into hard error, see issue #57742 \
+         <https://github.com/rust-lang/rust/issues/57742> for more information",
+    );
+    store.register_removed(
+        "incoherent_fundamental_impls",
+        "converted into hard error, see issue #46205 \
+         <https://github.com/rust-lang/rust/issues/46205> for more information",
+    );
+    store.register_removed(
+        "legacy_constructor_visibility",
+        "converted into hard error, see issue #39207 \
+         <https://github.com/rust-lang/rust/issues/39207> for more information",
+    );
+    store.register_removed(
+        "legacy_directory_ownership",
+        "converted into hard error, see issue #37872 \
+         <https://github.com/rust-lang/rust/issues/37872> for more information",
+    );
+    store.register_removed(
+        "safe_extern_statics",
+        "converted into hard error, see issue #36247 \
+         <https://github.com/rust-lang/rust/issues/36247> for more information",
+    );
+    store.register_removed(
+        "parenthesized_params_in_types_and_modules",
+        "converted into hard error, see issue #42238 \
+         <https://github.com/rust-lang/rust/issues/42238> for more information",
+    );
+    store.register_removed(
+        "duplicate_macro_exports",
+        "converted into hard error, see issue #35896 \
+         <https://github.com/rust-lang/rust/issues/35896> for more information",
+    );
+    store.register_removed(
+        "nested_impl_trait",
+        "converted into hard error, see issue #59014 \
+         <https://github.com/rust-lang/rust/issues/59014> for more information",
+    );
+    store.register_removed("plugin_as_library", "plugins have been deprecated and retired");
+    store.register_removed(
+        "unsupported_naked_functions",
+        "converted into hard error, see RFC 2972 \
+         <https://github.com/rust-lang/rfcs/blob/master/text/2972-constrained-naked.md> for more information",
+    );
+    store.register_removed(
+        "mutable_borrow_reservation_conflict",
+        "now allowed, see issue #59159 \
+         <https://github.com/rust-lang/rust/issues/59159> for more information",
+    );
+}
+
+fn register_internals(store: &mut LintStore) {
+    store.register_lints(&LintPassImpl::get_lints());
+    store.register_early_pass(|| Box::new(LintPassImpl));
+    store.register_lints(&DefaultHashTypes::get_lints());
+    store.register_late_pass(|| Box::new(DefaultHashTypes));
+    store.register_lints(&QueryStability::get_lints());
+    store.register_late_pass(|| Box::new(QueryStability));
+    store.register_lints(&ExistingDocKeyword::get_lints());
+    store.register_late_pass(|| Box::new(ExistingDocKeyword));
+    store.register_lints(&TyTyKind::get_lints());
+    store.register_late_pass(|| Box::new(TyTyKind));
+    store.register_lints(&Diagnostics::get_lints());
+    store.register_late_pass(|| Box::new(Diagnostics));
+    store.register_lints(&BadOptAccess::get_lints());
+    store.register_late_pass(|| Box::new(BadOptAccess));
+    store.register_lints(&PassByValue::get_lints());
+    store.register_late_pass(|| Box::new(PassByValue));
+    // FIXME(davidtwco): deliberately do not include `UNTRANSLATABLE_DIAGNOSTIC` and
+    // `DIAGNOSTIC_OUTSIDE_OF_IMPL` here because `-Wrustc::internal` is provided to every crate and
+    // these lints will trigger all of the time - change this once migration to diagnostic structs
+    // and translation is completed
+    store.register_group(
+        false,
+        "rustc::internal",
+        None,
+        vec![
+            LintId::of(DEFAULT_HASH_TYPES),
+            LintId::of(POTENTIAL_QUERY_INSTABILITY),
+            LintId::of(USAGE_OF_TY_TYKIND),
+            LintId::of(PASS_BY_VALUE),
+            LintId::of(LINT_PASS_IMPL_WITHOUT_MACRO),
+            LintId::of(USAGE_OF_QUALIFIED_TY),
+            LintId::of(EXISTING_DOC_KEYWORD),
+            LintId::of(BAD_OPT_ACCESS),
+        ],
+    );
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/compiler/rustc_lint/src/methods.rs b/compiler/rustc_lint/src/methods.rs
new file mode 100644
index 000000000..ff5a01749
--- /dev/null
+++ b/compiler/rustc_lint/src/methods.rs
@@ -0,0 +1,103 @@
+use crate::LateContext;
+use crate::LateLintPass;
+use crate::LintContext;
+use rustc_errors::fluent;
+use rustc_hir::{Expr, ExprKind, PathSegment};
+use rustc_middle::ty;
+use rustc_span::{symbol::sym, ExpnKind, Span};
+
+declare_lint! {
+    /// The `temporary_cstring_as_ptr` lint detects getting the inner pointer of
+    /// a temporary `CString`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// # use std::ffi::CString;
+    /// let c_str = CString::new("foo").unwrap().as_ptr();
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The inner pointer of a `CString` lives only as long as the `CString` it
+    /// points to. Getting the inner pointer of a *temporary* `CString` allows the `CString`
+    /// to be dropped at the end of the statement, as it is not being referenced as far as the typesystem
+    /// is concerned. This means outside of the statement the pointer will point to freed memory, which
+    /// causes undefined behavior if the pointer is later dereferenced.
+    pub TEMPORARY_CSTRING_AS_PTR,
+    Warn,
+    "detects getting the inner pointer of a temporary `CString`"
+}
+
+declare_lint_pass!(TemporaryCStringAsPtr => [TEMPORARY_CSTRING_AS_PTR]);
+
+fn in_macro(span: Span) -> bool {
+    if span.from_expansion() {
+        !matches!(span.ctxt().outer_expn_data().kind, ExpnKind::Desugaring(..))
+    } else {
+        false
+    }
+}
+
+fn first_method_call<'tcx>(
+    expr: &'tcx Expr<'tcx>,
+) -> Option<(&'tcx PathSegment<'tcx>, &'tcx [Expr<'tcx>])> {
+    if let ExprKind::MethodCall(path, args, _) = &expr.kind {
+        if args.iter().any(|e| e.span.from_expansion()) { None } else { Some((path, *args)) }
+    } else {
+        None
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for TemporaryCStringAsPtr {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if in_macro(expr.span) {
+            return;
+        }
+
+        match first_method_call(expr) {
+            Some((path, args)) if path.ident.name == sym::as_ptr => {
+                let unwrap_arg = &args[0];
+                let as_ptr_span = path.ident.span;
+                match first_method_call(unwrap_arg) {
+                    Some((path, args))
+                        if path.ident.name == sym::unwrap || path.ident.name == sym::expect =>
+                    {
+                        let source_arg = &args[0];
+                        lint_cstring_as_ptr(cx, as_ptr_span, source_arg, unwrap_arg);
+                    }
+                    _ => return,
+                }
+            }
+            _ => return,
+        }
+    }
+}
+
+fn lint_cstring_as_ptr(
+    cx: &LateContext<'_>,
+    as_ptr_span: Span,
+    source: &rustc_hir::Expr<'_>,
+    unwrap: &rustc_hir::Expr<'_>,
+) {
+    let source_type = cx.typeck_results().expr_ty(source);
+    if let ty::Adt(def, substs) = source_type.kind() {
+        if cx.tcx.is_diagnostic_item(sym::Result, def.did()) {
+            if let ty::Adt(adt, _) = substs.type_at(0).kind() {
+                if cx.tcx.is_diagnostic_item(sym::cstring_type, adt.did()) {
+                    cx.struct_span_lint(TEMPORARY_CSTRING_AS_PTR, as_ptr_span, |diag| {
+                        diag.build(fluent::lint::cstring_ptr)
+                            .span_label(as_ptr_span, fluent::lint::as_ptr_label)
+                            .span_label(unwrap.span, fluent::lint::unwrap_label)
+                            .note(fluent::lint::note)
+                            .help(fluent::lint::help)
+                            .emit();
+                    });
+                }
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/non_ascii_idents.rs b/compiler/rustc_lint/src/non_ascii_idents.rs
new file mode 100644
index 000000000..764003e61
--- /dev/null
+++ b/compiler/rustc_lint/src/non_ascii_idents.rs
@@ -0,0 +1,345 @@
+use crate::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::fluent;
+use rustc_span::symbol::Symbol;
+
+declare_lint! {
+    /// The `non_ascii_idents` lint detects non-ASCII identifiers.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// # #![allow(unused)]
+    /// #![deny(non_ascii_idents)]
+    /// fn main() {
+    ///     let föö = 1;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint allows projects that wish to retain the limit of only using
+    /// ASCII characters to switch this lint to "forbid" (for example to ease
+    /// collaboration or for security reasons).
+    /// See [RFC 2457] for more details.
+    ///
+    /// [RFC 2457]: https://github.com/rust-lang/rfcs/blob/master/text/2457-non-ascii-idents.md
+    pub NON_ASCII_IDENTS,
+    Allow,
+    "detects non-ASCII identifiers",
+    crate_level_only
+}
+
+declare_lint! {
+    /// The `uncommon_codepoints` lint detects uncommon Unicode codepoints in
+    /// identifiers.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// const µ: f64 = 0.000001;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint warns about using characters which are not commonly used, and may
+    /// cause visual confusion.
+    ///
+    /// This lint is triggered by identifiers that contain a codepoint that is
+    /// not part of the set of "Allowed" codepoints as described by [Unicode®
+    /// Technical Standard #39 Unicode Security Mechanisms Section 3.1 General
+    /// Security Profile for Identifiers][TR39Allowed].
+    ///
+    /// Note that the set of uncommon codepoints may change over time. Beware
+    /// that if you "forbid" this lint that existing code may fail in the
+    /// future.
+    ///
+    /// [TR39Allowed]: https://www.unicode.org/reports/tr39/#General_Security_Profile
+    pub UNCOMMON_CODEPOINTS,
+    Warn,
+    "detects uncommon Unicode codepoints in identifiers",
+    crate_level_only
+}
+
+declare_lint! {
+    /// The `confusable_idents` lint detects visually confusable pairs between
+    /// identifiers.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// // Latin Capital Letter E With Caron
+    /// pub const Ě: i32 = 1;
+    /// // Latin Capital Letter E With Breve
+    /// pub const Ĕ: i32 = 2;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint warns when different identifiers may appear visually similar,
+    /// which can cause confusion.
+    ///
+    /// The confusable detection algorithm is based on [Unicode® Technical
+    /// Standard #39 Unicode Security Mechanisms Section 4 Confusable
+    /// Detection][TR39Confusable]. For every distinct identifier X execute
+    /// the function `skeleton(X)`. If there exist two distinct identifiers X
+    /// and Y in the same crate where `skeleton(X) = skeleton(Y)` report it.
+    /// The compiler uses the same mechanism to check if an identifier is too
+    /// similar to a keyword.
+    ///
+    /// Note that the set of confusable characters may change over time.
+    /// Beware that if you "forbid" this lint that existing code may fail in
+    /// the future.
+    ///
+    /// [TR39Confusable]: https://www.unicode.org/reports/tr39/#Confusable_Detection
+    pub CONFUSABLE_IDENTS,
+    Warn,
+    "detects visually confusable pairs between identifiers",
+    crate_level_only
+}
+
+declare_lint! {
+    /// The `mixed_script_confusables` lint detects visually confusable
+    /// characters in identifiers between different [scripts].
+    ///
+    /// [scripts]: https://en.wikipedia.org/wiki/Script_(Unicode)
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// // The Japanese katakana character エ can be confused with the Han character 工.
+    /// const エ: &'static str = "アイウ";
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This lint warns when characters between different scripts may appear
+    /// visually similar, which can cause confusion.
+    ///
+    /// If the crate contains other identifiers in the same script that have
+    /// non-confusable characters, then this lint will *not* be issued. For
+    /// example, if the example given above has another identifier with
+    /// katakana characters (such as `let カタカナ = 123;`), then this indicates
+    /// that you are intentionally using katakana, and it will not warn about
+    /// it.
+    ///
+    /// Note that the set of confusable characters may change over time.
+    /// Beware that if you "forbid" this lint that existing code may fail in
+    /// the future.
+    pub MIXED_SCRIPT_CONFUSABLES,
+    Warn,
+    "detects Unicode scripts whose mixed script confusables codepoints are solely used",
+    crate_level_only
+}
+
+declare_lint_pass!(NonAsciiIdents => [NON_ASCII_IDENTS, UNCOMMON_CODEPOINTS, CONFUSABLE_IDENTS, MIXED_SCRIPT_CONFUSABLES]);
+
+impl EarlyLintPass for NonAsciiIdents {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
+        use rustc_session::lint::Level;
+        use rustc_span::Span;
+        use std::collections::BTreeMap;
+        use unicode_security::GeneralSecurityProfile;
+
+        let check_non_ascii_idents = cx.builder.lint_level(NON_ASCII_IDENTS).0 != Level::Allow;
+        let check_uncommon_codepoints =
+            cx.builder.lint_level(UNCOMMON_CODEPOINTS).0 != Level::Allow;
+        let check_confusable_idents = cx.builder.lint_level(CONFUSABLE_IDENTS).0 != Level::Allow;
+        let check_mixed_script_confusables =
+            cx.builder.lint_level(MIXED_SCRIPT_CONFUSABLES).0 != Level::Allow;
+
+        if !check_non_ascii_idents
+            && !check_uncommon_codepoints
+            && !check_confusable_idents
+            && !check_mixed_script_confusables
+        {
+            return;
+        }
+
+        let mut has_non_ascii_idents = false;
+        let symbols = cx.sess().parse_sess.symbol_gallery.symbols.lock();
+
+        // Sort by `Span` so that error messages make sense with respect to the
+        // order of identifier locations in the code.
+        let mut symbols: Vec<_> = symbols.iter().collect();
+        symbols.sort_by_key(|k| k.1);
+
+        for (symbol, &sp) in symbols.iter() {
+            let symbol_str = symbol.as_str();
+            if symbol_str.is_ascii() {
+                continue;
+            }
+            has_non_ascii_idents = true;
+            cx.struct_span_lint(NON_ASCII_IDENTS, sp, |lint| {
+                lint.build(fluent::lint::identifier_non_ascii_char).emit();
+            });
+            if check_uncommon_codepoints
+                && !symbol_str.chars().all(GeneralSecurityProfile::identifier_allowed)
+            {
+                cx.struct_span_lint(UNCOMMON_CODEPOINTS, sp, |lint| {
+                    lint.build(fluent::lint::identifier_uncommon_codepoints).emit();
+                })
+            }
+        }
+
+        if has_non_ascii_idents && check_confusable_idents {
+            let mut skeleton_map: FxHashMap<Symbol, (Symbol, Span, bool)> =
+                FxHashMap::with_capacity_and_hasher(symbols.len(), Default::default());
+            let mut skeleton_buf = String::new();
+
+            for (&symbol, &sp) in symbols.iter() {
+                use unicode_security::confusable_detection::skeleton;
+
+                let symbol_str = symbol.as_str();
+                let is_ascii = symbol_str.is_ascii();
+
+                // Get the skeleton as a `Symbol`.
+                skeleton_buf.clear();
+                skeleton_buf.extend(skeleton(&symbol_str));
+                let skeleton_sym = if *symbol_str == *skeleton_buf {
+                    symbol
+                } else {
+                    Symbol::intern(&skeleton_buf)
+                };
+
+                skeleton_map
+                    .entry(skeleton_sym)
+                    .and_modify(|(existing_symbol, existing_span, existing_is_ascii)| {
+                        if !*existing_is_ascii || !is_ascii {
+                            cx.struct_span_lint(CONFUSABLE_IDENTS, sp, |lint| {
+                                lint.build(fluent::lint::confusable_identifier_pair)
+                                    .set_arg("existing_sym", *existing_symbol)
+                                    .set_arg("sym", symbol)
+                                    .span_label(*existing_span, fluent::lint::label)
+                                    .emit();
+                            });
+                        }
+                        if *existing_is_ascii && !is_ascii {
+                            *existing_symbol = symbol;
+                            *existing_span = sp;
+                            *existing_is_ascii = is_ascii;
+                        }
+                    })
+                    .or_insert((symbol, sp, is_ascii));
+            }
+        }
+
+        if has_non_ascii_idents && check_mixed_script_confusables {
+            use unicode_security::is_potential_mixed_script_confusable_char;
+            use unicode_security::mixed_script::AugmentedScriptSet;
+
+            #[derive(Clone)]
+            enum ScriptSetUsage {
+                Suspicious(Vec<char>, Span),
+                Verified,
+            }
+
+            let mut script_states: FxHashMap<AugmentedScriptSet, ScriptSetUsage> =
+                FxHashMap::default();
+            let latin_augmented_script_set = AugmentedScriptSet::for_char('A');
+            script_states.insert(latin_augmented_script_set, ScriptSetUsage::Verified);
+
+            let mut has_suspicous = false;
+            for (symbol, &sp) in symbols.iter() {
+                let symbol_str = symbol.as_str();
+                for ch in symbol_str.chars() {
+                    if ch.is_ascii() {
+                        // all ascii characters are covered by exception.
+                        continue;
+                    }
+                    if !GeneralSecurityProfile::identifier_allowed(ch) {
+                        // this character is covered by `uncommon_codepoints` lint.
+                        continue;
+                    }
+                    let augmented_script_set = AugmentedScriptSet::for_char(ch);
+                    script_states
+                        .entry(augmented_script_set)
+                        .and_modify(|existing_state| {
+                            if let ScriptSetUsage::Suspicious(ch_list, _) = existing_state {
+                                if is_potential_mixed_script_confusable_char(ch) {
+                                    ch_list.push(ch);
+                                } else {
+                                    *existing_state = ScriptSetUsage::Verified;
+                                }
+                            }
+                        })
+                        .or_insert_with(|| {
+                            if !is_potential_mixed_script_confusable_char(ch) {
+                                ScriptSetUsage::Verified
+                            } else {
+                                has_suspicous = true;
+                                ScriptSetUsage::Suspicious(vec![ch], sp)
+                            }
+                        });
+                }
+            }
+
+            if has_suspicous {
+                let verified_augmented_script_sets = script_states
+                    .iter()
+                    .flat_map(|(k, v)| match v {
+                        ScriptSetUsage::Verified => Some(*k),
+                        _ => None,
+                    })
+                    .collect::<Vec<_>>();
+
+                // we're sorting the output here.
+                let mut lint_reports: BTreeMap<(Span, Vec<char>), AugmentedScriptSet> =
+                    BTreeMap::new();
+
+                'outerloop: for (augment_script_set, usage) in script_states {
+                    let ScriptSetUsage::Suspicious(mut ch_list, sp) = usage else { continue };
+
+                    if augment_script_set.is_all() {
+                        continue;
+                    }
+
+                    for existing in verified_augmented_script_sets.iter() {
+                        if existing.is_all() {
+                            continue;
+                        }
+                        let mut intersect = *existing;
+                        intersect.intersect_with(augment_script_set);
+                        if !intersect.is_empty() && !intersect.is_all() {
+                            continue 'outerloop;
+                        }
+                    }
+
+                    // We sort primitive chars here and can use unstable sort
+                    ch_list.sort_unstable();
+                    ch_list.dedup();
+                    lint_reports.insert((sp, ch_list), augment_script_set);
+                }
+
+                for ((sp, ch_list), script_set) in lint_reports {
+                    cx.struct_span_lint(MIXED_SCRIPT_CONFUSABLES, sp, |lint| {
+                        let mut includes = String::new();
+                        for (idx, ch) in ch_list.into_iter().enumerate() {
+                            if idx != 0 {
+                                includes += ", ";
+                            }
+                            let char_info = format!("'{}' (U+{:04X})", ch, ch as u32);
+                            includes += &char_info;
+                        }
+                        lint.build(fluent::lint::mixed_script_confusables)
+                            .set_arg("set", script_set.to_string())
+                            .set_arg("includes", includes)
+                            .note(fluent::lint::includes_note)
+                            .note(fluent::lint::note)
+                            .emit();
+                    });
+                }
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
new file mode 100644
index 000000000..cdad2d2e8
--- /dev/null
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -0,0 +1,357 @@
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_errors::{fluent, Applicability};
+use rustc_hir as hir;
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_middle::lint::in_external_macro;
+use rustc_middle::ty;
+use rustc_middle::ty::subst::InternalSubsts;
+use rustc_parse_format::{ParseMode, Parser, Piece};
+use rustc_session::lint::FutureIncompatibilityReason;
+use rustc_span::edition::Edition;
+use rustc_span::{hygiene, sym, symbol::kw, InnerSpan, Span, Symbol};
+use rustc_trait_selection::infer::InferCtxtExt;
+
+declare_lint! {
+    /// The `non_fmt_panics` lint detects `panic!(..)` invocations where the first
+    /// argument is not a formatting string.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,no_run,edition2018
+    /// panic!("{}");
+    /// panic!(123);
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In Rust 2018 and earlier, `panic!(x)` directly uses `x` as the message.
+    /// That means that `panic!("{}")` panics with the message `"{}"` instead
+    /// of using it as a formatting string, and `panic!(123)` will panic with
+    /// an `i32` as message.
+    ///
+    /// Rust 2021 always interprets the first argument as format string.
+    NON_FMT_PANICS,
+    Warn,
+    "detect single-argument panic!() invocations in which the argument is not a format string",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
+        explain_reason: false,
+    };
+    report_in_external_macro
+}
+
+declare_lint_pass!(NonPanicFmt => [NON_FMT_PANICS]);
+
+impl<'tcx> LateLintPass<'tcx> for NonPanicFmt {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+        if let hir::ExprKind::Call(f, [arg]) = &expr.kind {
+            if let &ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(f).kind() {
+                let f_diagnostic_name = cx.tcx.get_diagnostic_name(def_id);
+
+                if Some(def_id) == cx.tcx.lang_items().begin_panic_fn()
+                    || Some(def_id) == cx.tcx.lang_items().panic_fn()
+                    || f_diagnostic_name == Some(sym::panic_str)
+                {
+                    if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
+                        if matches!(
+                            cx.tcx.get_diagnostic_name(id),
+                            Some(sym::core_panic_2015_macro | sym::std_panic_2015_macro)
+                        ) {
+                            check_panic(cx, f, arg);
+                        }
+                    }
+                } else if f_diagnostic_name == Some(sym::unreachable_display) {
+                    if let Some(id) = f.span.ctxt().outer_expn_data().macro_def_id {
+                        if cx.tcx.is_diagnostic_item(sym::unreachable_2015_macro, id) {
+                            check_panic(
+                                cx,
+                                f,
+                                // This is safe because we checked above that the callee is indeed
+                                // unreachable_display
+                                match &arg.kind {
+                                    // Get the borrowed arg not the borrow
+                                    hir::ExprKind::AddrOf(ast::BorrowKind::Ref, _, arg) => arg,
+                                    _ => bug!("call to unreachable_display without borrow"),
+                                },
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tcx hir::Expr<'tcx>) {
+    if let hir::ExprKind::Lit(lit) = &arg.kind {
+        if let ast::LitKind::Str(sym, _) = lit.node {
+            // The argument is a string literal.
+            check_panic_str(cx, f, arg, sym.as_str());
+            return;
+        }
+    }
+
+    // The argument is *not* a string literal.
+
+    let (span, panic, symbol) = panic_call(cx, f);
+
+    if in_external_macro(cx.sess(), span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
+    // Find the span of the argument to `panic!()` or `unreachable!`, before expansion in the
+    // case of `panic!(some_macro!())` or `unreachable!(some_macro!())`.
+    // We don't use source_callsite(), because this `panic!(..)` might itself
+    // be expanded from another macro, in which case we want to stop at that
+    // expansion.
+    let mut arg_span = arg.span;
+    let mut arg_macro = None;
+    while !span.contains(arg_span) {
+        let expn = arg_span.ctxt().outer_expn_data();
+        if expn.is_root() {
+            break;
+        }
+        arg_macro = expn.macro_def_id;
+        arg_span = expn.call_site;
+    }
+
+    cx.struct_span_lint(NON_FMT_PANICS, arg_span, |lint| {
+        let mut l = lint.build(fluent::lint::non_fmt_panic);
+        l.set_arg("name", symbol);
+        l.note(fluent::lint::note);
+        l.note(fluent::lint::more_info_note);
+        if !is_arg_inside_call(arg_span, span) {
+            // No clue where this argument is coming from.
+            l.emit();
+            return;
+        }
+        if arg_macro.map_or(false, |id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
+            // A case of `panic!(format!(..))`.
+            l.note(fluent::lint::supports_fmt_note);
+            if let Some((open, close, _)) = find_delimiters(cx, arg_span) {
+                l.multipart_suggestion(
+                    fluent::lint::supports_fmt_suggestion,
+                    vec![
+                        (arg_span.until(open.shrink_to_hi()), "".into()),
+                        (close.until(arg_span.shrink_to_hi()), "".into()),
+                    ],
+                    Applicability::MachineApplicable,
+                );
+            }
+        } else {
+            let ty = cx.typeck_results().expr_ty(arg);
+            // If this is a &str or String, we can confidently give the `"{}", ` suggestion.
+            let is_str = matches!(
+                ty.kind(),
+                ty::Ref(_, r, _) if *r.kind() == ty::Str,
+            ) || matches!(
+                ty.ty_adt_def(),
+                Some(ty_def) if cx.tcx.is_diagnostic_item(sym::String, ty_def.did()),
+            );
+
+            let (suggest_display, suggest_debug) = cx.tcx.infer_ctxt().enter(|infcx| {
+                let display = is_str
+                    || cx.tcx.get_diagnostic_item(sym::Display).map(|t| {
+                        infcx
+                            .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
+                            .may_apply()
+                    }) == Some(true);
+                let debug = !display
+                    && cx.tcx.get_diagnostic_item(sym::Debug).map(|t| {
+                        infcx
+                            .type_implements_trait(t, ty, InternalSubsts::empty(), cx.param_env)
+                            .may_apply()
+                    }) == Some(true);
+                (display, debug)
+            });
+
+            let suggest_panic_any = !is_str && panic == sym::std_panic_macro;
+
+            let fmt_applicability = if suggest_panic_any {
+                // If we can use panic_any, use that as the MachineApplicable suggestion.
+                Applicability::MaybeIncorrect
+            } else {
+                // If we don't suggest panic_any, using a format string is our best bet.
+                Applicability::MachineApplicable
+            };
+
+            if suggest_display {
+                l.span_suggestion_verbose(
+                    arg_span.shrink_to_lo(),
+                    fluent::lint::display_suggestion,
+                    "\"{}\", ",
+                    fmt_applicability,
+                );
+            } else if suggest_debug {
+                l.set_arg("ty", ty);
+                l.span_suggestion_verbose(
+                    arg_span.shrink_to_lo(),
+                    fluent::lint::debug_suggestion,
+                    "\"{:?}\", ",
+                    fmt_applicability,
+                );
+            }
+
+            if suggest_panic_any {
+                if let Some((open, close, del)) = find_delimiters(cx, span) {
+                    l.set_arg("already_suggested", suggest_display || suggest_debug);
+                    l.multipart_suggestion(
+                        fluent::lint::panic_suggestion,
+                        if del == '(' {
+                            vec![(span.until(open), "std::panic::panic_any".into())]
+                        } else {
+                            vec![
+                                (span.until(open.shrink_to_hi()), "std::panic::panic_any(".into()),
+                                (close, ")".into()),
+                            ]
+                        },
+                        Applicability::MachineApplicable,
+                    );
+                }
+            }
+        }
+        l.emit();
+    });
+}
+
+fn check_panic_str<'tcx>(
+    cx: &LateContext<'tcx>,
+    f: &'tcx hir::Expr<'tcx>,
+    arg: &'tcx hir::Expr<'tcx>,
+    fmt: &str,
+) {
+    if !fmt.contains(&['{', '}']) {
+        // No brace, no problem.
+        return;
+    }
+
+    let (span, _, _) = panic_call(cx, f);
+
+    if in_external_macro(cx.sess(), span) && in_external_macro(cx.sess(), arg.span) {
+        // Nothing that can be done about it in the current crate.
+        return;
+    }
+
+    let fmt_span = arg.span.source_callsite();
+
+    let (snippet, style) = match cx.sess().parse_sess.source_map().span_to_snippet(fmt_span) {
+        Ok(snippet) => {
+            // Count the number of `#`s between the `r` and `"`.
+            let style = snippet.strip_prefix('r').and_then(|s| s.find('"'));
+            (Some(snippet), style)
+        }
+        Err(_) => (None, None),
+    };
+
+    let mut fmt_parser = Parser::new(fmt, style, snippet.clone(), false, ParseMode::Format);
+    let n_arguments = (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
+
+    if n_arguments > 0 && fmt_parser.errors.is_empty() {
+        let arg_spans: Vec<_> = match &fmt_parser.arg_places[..] {
+            [] => vec![fmt_span],
+            v => v
+                .iter()
+                .map(|span| fmt_span.from_inner(InnerSpan::new(span.start, span.end)))
+                .collect(),
+        };
+        cx.struct_span_lint(NON_FMT_PANICS, arg_spans, |lint| {
+            let mut l = lint.build(fluent::lint::non_fmt_panic_unused);
+            l.set_arg("count", n_arguments);
+            l.note(fluent::lint::note);
+            if is_arg_inside_call(arg.span, span) {
+                l.span_suggestion(
+                    arg.span.shrink_to_hi(),
+                    fluent::lint::add_args_suggestion,
+                    ", ...",
+                    Applicability::HasPlaceholders,
+                );
+                l.span_suggestion(
+                    arg.span.shrink_to_lo(),
+                    fluent::lint::add_fmt_suggestion,
+                    "\"{}\", ",
+                    Applicability::MachineApplicable,
+                );
+            }
+            l.emit();
+        });
+    } else {
+        let brace_spans: Option<Vec<_>> =
+            snippet.filter(|s| s.starts_with('"') || s.starts_with("r#")).map(|s| {
+                s.char_indices()
+                    .filter(|&(_, c)| c == '{' || c == '}')
+                    .map(|(i, _)| fmt_span.from_inner(InnerSpan { start: i, end: i + 1 }))
+                    .collect()
+            });
+        let count = brace_spans.as_ref().map(|v| v.len()).unwrap_or(/* any number >1 */ 2);
+        cx.struct_span_lint(NON_FMT_PANICS, brace_spans.unwrap_or_else(|| vec![span]), |lint| {
+            let mut l = lint.build(fluent::lint::non_fmt_panic_braces);
+            l.set_arg("count", count);
+            l.note(fluent::lint::note);
+            if is_arg_inside_call(arg.span, span) {
+                l.span_suggestion(
+                    arg.span.shrink_to_lo(),
+                    fluent::lint::suggestion,
+                    "\"{}\", ",
+                    Applicability::MachineApplicable,
+                );
+            }
+            l.emit();
+        });
+    }
+}
+
+/// Given the span of `some_macro!(args);`, gives the span of `(` and `)`,
+/// and the type of (opening) delimiter used.
+fn find_delimiters<'tcx>(cx: &LateContext<'tcx>, span: Span) -> Option<(Span, Span, char)> {
+    let snippet = cx.sess().parse_sess.source_map().span_to_snippet(span).ok()?;
+    let (open, open_ch) = snippet.char_indices().find(|&(_, c)| "([{".contains(c))?;
+    let close = snippet.rfind(|c| ")]}".contains(c))?;
+    Some((
+        span.from_inner(InnerSpan { start: open, end: open + 1 }),
+        span.from_inner(InnerSpan { start: close, end: close + 1 }),
+        open_ch,
+    ))
+}
+
+fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span, Symbol, Symbol) {
+    let mut expn = f.span.ctxt().outer_expn_data();
+
+    let mut panic_macro = kw::Empty;
+
+    // Unwrap more levels of macro expansion, as panic_2015!()
+    // was likely expanded from panic!() and possibly from
+    // [debug_]assert!().
+    loop {
+        let parent = expn.call_site.ctxt().outer_expn_data();
+        let Some(id) = parent.macro_def_id else { break };
+        let Some(name) = cx.tcx.get_diagnostic_name(id) else { break };
+        if !matches!(
+            name,
+            sym::core_panic_macro
+                | sym::std_panic_macro
+                | sym::assert_macro
+                | sym::debug_assert_macro
+                | sym::unreachable_macro
+        ) {
+            break;
+        }
+        expn = parent;
+        panic_macro = name;
+    }
+
+    let macro_symbol =
+        if let hygiene::ExpnKind::Macro(_, symbol) = expn.kind { symbol } else { sym::panic };
+    (expn.call_site, panic_macro, macro_symbol)
+}
+
+fn is_arg_inside_call(arg: Span, call: Span) -> bool {
+    // We only add suggestions if the argument we're looking at appears inside the
+    // panic call in the source file, to avoid invalid suggestions when macros are involved.
+    // We specifically check for the spans to not be identical, as that happens sometimes when
+    // proc_macros lie about spans and apply the same span to all the tokens they produce.
+    call.contains(arg) && !call.source_equal(arg)
+}
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
new file mode 100644
index 000000000..8d04d68bf
--- /dev/null
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -0,0 +1,565 @@
+use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_attr as attr;
+use rustc_errors::{fluent, Applicability};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{GenericParamKind, PatKind};
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+use rustc_span::{symbol::Ident, BytePos, Span};
+use rustc_target::spec::abi::Abi;
+
+#[derive(PartialEq)]
+pub enum MethodLateContext {
+    TraitAutoImpl,
+    TraitImpl,
+    PlainImpl,
+}
+
+pub fn method_context(cx: &LateContext<'_>, id: hir::HirId) -> MethodLateContext {
+    let def_id = cx.tcx.hir().local_def_id(id);
+    let item = cx.tcx.associated_item(def_id);
+    match item.container {
+        ty::TraitContainer => MethodLateContext::TraitAutoImpl,
+        ty::ImplContainer => match cx.tcx.impl_trait_ref(item.container_id(cx.tcx)) {
+            Some(_) => MethodLateContext::TraitImpl,
+            None => MethodLateContext::PlainImpl,
+        },
+    }
+}
+
+declare_lint! {
+    /// The `non_camel_case_types` lint detects types, variants, traits and
+    /// type parameters that don't have camel case names.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// struct my_struct;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The preferred style for these identifiers is to use "camel case", such
+    /// as `MyStruct`, where the first letter should not be lowercase, and
+    /// should not use underscores between letters. Underscores are allowed at
+    /// the beginning and end of the identifier, as well as between
+    /// non-letters (such as `X86_64`).
+    pub NON_CAMEL_CASE_TYPES,
+    Warn,
+    "types, variants, traits and type parameters should have camel case names"
+}
+
+declare_lint_pass!(NonCamelCaseTypes => [NON_CAMEL_CASE_TYPES]);
+
+/// Some unicode characters *have* case, are considered upper case or lower case, but they *can't*
+/// be upper cased or lower cased. For the purposes of the lint suggestion, we care about being able
+/// to change the char's case.
+fn char_has_case(c: char) -> bool {
+    let mut l = c.to_lowercase();
+    let mut u = c.to_uppercase();
+    while let Some(l) = l.next() {
+        match u.next() {
+            Some(u) if l != u => return true,
+            _ => {}
+        }
+    }
+    u.next().is_some()
+}
+
+fn is_camel_case(name: &str) -> bool {
+    let name = name.trim_matches('_');
+    if name.is_empty() {
+        return true;
+    }
+
+    // start with a non-lowercase letter rather than non-uppercase
+    // ones (some scripts don't have a concept of upper/lowercase)
+    !name.chars().next().unwrap().is_lowercase()
+        && !name.contains("__")
+        && !name.chars().collect::<Vec<_>>().array_windows().any(|&[fst, snd]| {
+            // contains a capitalisable character followed by, or preceded by, an underscore
+            char_has_case(fst) && snd == '_' || char_has_case(snd) && fst == '_'
+        })
+}
+
+fn to_camel_case(s: &str) -> String {
+    s.trim_matches('_')
+        .split('_')
+        .filter(|component| !component.is_empty())
+        .map(|component| {
+            let mut camel_cased_component = String::new();
+
+            let mut new_word = true;
+            let mut prev_is_lower_case = true;
+
+            for c in component.chars() {
+                // Preserve the case if an uppercase letter follows a lowercase letter, so that
+                // `camelCase` is converted to `CamelCase`.
+                if prev_is_lower_case && c.is_uppercase() {
+                    new_word = true;
+                }
+
+                if new_word {
+                    camel_cased_component.extend(c.to_uppercase());
+                } else {
+                    camel_cased_component.extend(c.to_lowercase());
+                }
+
+                prev_is_lower_case = c.is_lowercase();
+                new_word = false;
+            }
+
+            camel_cased_component
+        })
+        .fold((String::new(), None), |(acc, prev): (String, Option<String>), next| {
+            // separate two components with an underscore if their boundary cannot
+            // be distinguished using an uppercase/lowercase case distinction
+            let join = if let Some(prev) = prev {
+                let l = prev.chars().last().unwrap();
+                let f = next.chars().next().unwrap();
+                !char_has_case(l) && !char_has_case(f)
+            } else {
+                false
+            };
+            (acc + if join { "_" } else { "" } + &next, Some(next))
+        })
+        .0
+}
+
+impl NonCamelCaseTypes {
+    fn check_case(&self, cx: &EarlyContext<'_>, sort: &str, ident: &Ident) {
+        let name = ident.name.as_str();
+
+        if !is_camel_case(name) {
+            cx.struct_span_lint(NON_CAMEL_CASE_TYPES, ident.span, |lint| {
+                let mut err = lint.build(fluent::lint::non_camel_case_type);
+                let cc = to_camel_case(name);
+                // We cannot provide meaningful suggestions
+                // if the characters are in the category of "Lowercase Letter".
+                if *name != cc {
+                    err.span_suggestion(
+                        ident.span,
+                        fluent::lint::suggestion,
+                        to_camel_case(name),
+                        Applicability::MaybeIncorrect,
+                    );
+                } else {
+                    err.span_label(ident.span, fluent::lint::label);
+                }
+
+                err.set_arg("sort", sort);
+                err.set_arg("name", name);
+                err.emit();
+            })
+        }
+    }
+}
+
+impl EarlyLintPass for NonCamelCaseTypes {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, it: &ast::Item) {
+        let has_repr_c = it
+            .attrs
+            .iter()
+            .any(|attr| attr::find_repr_attrs(cx.sess(), attr).contains(&attr::ReprC));
+
+        if has_repr_c {
+            return;
+        }
+
+        match it.kind {
+            ast::ItemKind::TyAlias(..)
+            | ast::ItemKind::Enum(..)
+            | ast::ItemKind::Struct(..)
+            | ast::ItemKind::Union(..) => self.check_case(cx, "type", &it.ident),
+            ast::ItemKind::Trait(..) => self.check_case(cx, "trait", &it.ident),
+            ast::ItemKind::TraitAlias(..) => self.check_case(cx, "trait alias", &it.ident),
+            _ => (),
+        }
+    }
+
+    fn check_trait_item(&mut self, cx: &EarlyContext<'_>, it: &ast::AssocItem) {
+        if let ast::AssocItemKind::TyAlias(..) = it.kind {
+            self.check_case(cx, "associated type", &it.ident);
+        }
+    }
+
+    fn check_variant(&mut self, cx: &EarlyContext<'_>, v: &ast::Variant) {
+        self.check_case(cx, "variant", &v.ident);
+    }
+
+    fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
+        if let ast::GenericParamKind::Type { .. } = param.kind {
+            self.check_case(cx, "type parameter", &param.ident);
+        }
+    }
+}
+
+declare_lint! {
+    /// The `non_snake_case` lint detects variables, methods, functions,
+    /// lifetime parameters and modules that don't have snake case names.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// let MY_VALUE = 5;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The preferred style for these identifiers is to use "snake case",
+    /// where all the characters are in lowercase, with words separated with a
+    /// single underscore, such as `my_value`.
+    pub NON_SNAKE_CASE,
+    Warn,
+    "variables, methods, functions, lifetime parameters and modules should have snake case names"
+}
+
+declare_lint_pass!(NonSnakeCase => [NON_SNAKE_CASE]);
+
+impl NonSnakeCase {
+    fn to_snake_case(mut str: &str) -> String {
+        let mut words = vec![];
+        // Preserve leading underscores
+        str = str.trim_start_matches(|c: char| {
+            if c == '_' {
+                words.push(String::new());
+                true
+            } else {
+                false
+            }
+        });
+        for s in str.split('_') {
+            let mut last_upper = false;
+            let mut buf = String::new();
+            if s.is_empty() {
+                continue;
+            }
+            for ch in s.chars() {
+                if !buf.is_empty() && buf != "'" && ch.is_uppercase() && !last_upper {
+                    words.push(buf);
+                    buf = String::new();
+                }
+                last_upper = ch.is_uppercase();
+                buf.extend(ch.to_lowercase());
+            }
+            words.push(buf);
+        }
+        words.join("_")
+    }
+
+    /// Checks if a given identifier is snake case, and reports a diagnostic if not.
+    fn check_snake_case(&self, cx: &LateContext<'_>, sort: &str, ident: &Ident) {
+        fn is_snake_case(ident: &str) -> bool {
+            if ident.is_empty() {
+                return true;
+            }
+            let ident = ident.trim_start_matches('\'');
+            let ident = ident.trim_matches('_');
+
+            let mut allow_underscore = true;
+            ident.chars().all(|c| {
+                allow_underscore = match c {
+                    '_' if !allow_underscore => return false,
+                    '_' => false,
+                    // It would be more obvious to use `c.is_lowercase()`,
+                    // but some characters do not have a lowercase form
+                    c if !c.is_uppercase() => true,
+                    _ => return false,
+                };
+                true
+            })
+        }
+
+        let name = ident.name.as_str();
+
+        if !is_snake_case(name) {
+            cx.struct_span_lint(NON_SNAKE_CASE, ident.span, |lint| {
+                let sc = NonSnakeCase::to_snake_case(name);
+                let mut err = lint.build(fluent::lint::non_snake_case);
+                // We cannot provide meaningful suggestions
+                // if the characters are in the category of "Uppercase Letter".
+                if name != sc {
+                    // We have a valid span in almost all cases, but we don't have one when linting a crate
+                    // name provided via the command line.
+                    if !ident.span.is_dummy() {
+                        let sc_ident = Ident::from_str_and_span(&sc, ident.span);
+                        let (message, suggestion) = if sc_ident.is_reserved() {
+                            // We shouldn't suggest a reserved identifier to fix non-snake-case identifiers.
+                            // Instead, recommend renaming the identifier entirely or, if permitted,
+                            // escaping it to create a raw identifier.
+                            if sc_ident.name.can_be_raw() {
+                                (fluent::lint::rename_or_convert_suggestion, sc_ident.to_string())
+                            } else {
+                                err.note(fluent::lint::cannot_convert_note);
+                                (fluent::lint::rename_suggestion, String::new())
+                            }
+                        } else {
+                            (fluent::lint::convert_suggestion, sc.clone())
+                        };
+
+                        err.span_suggestion(
+                            ident.span,
+                            message,
+                            suggestion,
+                            Applicability::MaybeIncorrect,
+                        );
+                    } else {
+                        err.help(fluent::lint::help);
+                    }
+                } else {
+                    err.span_label(ident.span, fluent::lint::label);
+                }
+
+                err.set_arg("sort", sort);
+                err.set_arg("name", name);
+                err.set_arg("sc", sc);
+                err.emit();
+            });
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
+    fn check_mod(
+        &mut self,
+        cx: &LateContext<'_>,
+        _: &'tcx hir::Mod<'tcx>,
+        _: Span,
+        id: hir::HirId,
+    ) {
+        if id != hir::CRATE_HIR_ID {
+            return;
+        }
+
+        let crate_ident = if let Some(name) = &cx.tcx.sess.opts.crate_name {
+            Some(Ident::from_str(name))
+        } else {
+            cx.sess()
+                .find_by_name(&cx.tcx.hir().attrs(hir::CRATE_HIR_ID), sym::crate_name)
+                .and_then(|attr| attr.meta())
+                .and_then(|meta| {
+                    meta.name_value_literal().and_then(|lit| {
+                        if let ast::LitKind::Str(name, ..) = lit.kind {
+                            // Discard the double quotes surrounding the literal.
+                            let sp = cx
+                                .sess()
+                                .source_map()
+                                .span_to_snippet(lit.span)
+                                .ok()
+                                .and_then(|snippet| {
+                                    let left = snippet.find('"')?;
+                                    let right =
+                                        snippet.rfind('"').map(|pos| snippet.len() - pos)?;
+
+                                    Some(
+                                        lit.span
+                                            .with_lo(lit.span.lo() + BytePos(left as u32 + 1))
+                                            .with_hi(lit.span.hi() - BytePos(right as u32)),
+                                    )
+                                })
+                                .unwrap_or(lit.span);
+
+                            Some(Ident::new(name, sp))
+                        } else {
+                            None
+                        }
+                    })
+                })
+        };
+
+        if let Some(ident) = &crate_ident {
+            self.check_snake_case(cx, "crate", ident);
+        }
+    }
+
+    fn check_generic_param(&mut self, cx: &LateContext<'_>, param: &hir::GenericParam<'_>) {
+        if let GenericParamKind::Lifetime { .. } = param.kind {
+            self.check_snake_case(cx, "lifetime", &param.name.ident());
+        }
+    }
+
+    fn check_fn(
+        &mut self,
+        cx: &LateContext<'_>,
+        fk: FnKind<'_>,
+        _: &hir::FnDecl<'_>,
+        _: &hir::Body<'_>,
+        _: Span,
+        id: hir::HirId,
+    ) {
+        let attrs = cx.tcx.hir().attrs(id);
+        match &fk {
+            FnKind::Method(ident, sig, ..) => match method_context(cx, id) {
+                MethodLateContext::PlainImpl => {
+                    if sig.header.abi != Abi::Rust && cx.sess().contains_name(attrs, sym::no_mangle)
+                    {
+                        return;
+                    }
+                    self.check_snake_case(cx, "method", ident);
+                }
+                MethodLateContext::TraitAutoImpl => {
+                    self.check_snake_case(cx, "trait method", ident);
+                }
+                _ => (),
+            },
+            FnKind::ItemFn(ident, _, header) => {
+                // Skip foreign-ABI #[no_mangle] functions (Issue #31924)
+                if header.abi != Abi::Rust && cx.sess().contains_name(attrs, sym::no_mangle) {
+                    return;
+                }
+                self.check_snake_case(cx, "function", ident);
+            }
+            FnKind::Closure => (),
+        }
+    }
+
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        if let hir::ItemKind::Mod(_) = it.kind {
+            self.check_snake_case(cx, "module", &it.ident);
+        }
+    }
+
+    fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &hir::TraitItem<'_>) {
+        if let hir::TraitItemKind::Fn(_, hir::TraitFn::Required(pnames)) = item.kind {
+            self.check_snake_case(cx, "trait method", &item.ident);
+            for param_name in pnames {
+                self.check_snake_case(cx, "variable", param_name);
+            }
+        }
+    }
+
+    fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
+        if let PatKind::Binding(_, hid, ident, _) = p.kind {
+            if let hir::Node::Pat(parent_pat) = cx.tcx.hir().get(cx.tcx.hir().get_parent_node(hid))
+            {
+                if let PatKind::Struct(_, field_pats, _) = &parent_pat.kind {
+                    if field_pats
+                        .iter()
+                        .any(|field| !field.is_shorthand && field.pat.hir_id == p.hir_id)
+                    {
+                        // Only check if a new name has been introduced, to avoid warning
+                        // on both the struct definition and this pattern.
+                        self.check_snake_case(cx, "variable", &ident);
+                    }
+                    return;
+                }
+            }
+            self.check_snake_case(cx, "variable", &ident);
+        }
+    }
+
+    fn check_struct_def(&mut self, cx: &LateContext<'_>, s: &hir::VariantData<'_>) {
+        for sf in s.fields() {
+            self.check_snake_case(cx, "structure field", &sf.ident);
+        }
+    }
+}
+
+declare_lint! {
+    /// The `non_upper_case_globals` lint detects static items that don't have
+    /// uppercase identifiers.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// static max_points: i32 = 5;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The preferred style is for static item names to use all uppercase
+    /// letters such as `MAX_POINTS`.
+    pub NON_UPPER_CASE_GLOBALS,
+    Warn,
+    "static constants should have uppercase identifiers"
+}
+
+declare_lint_pass!(NonUpperCaseGlobals => [NON_UPPER_CASE_GLOBALS]);
+
+impl NonUpperCaseGlobals {
+    fn check_upper_case(cx: &LateContext<'_>, sort: &str, ident: &Ident) {
+        let name = ident.name.as_str();
+        if name.chars().any(|c| c.is_lowercase()) {
+            cx.struct_span_lint(NON_UPPER_CASE_GLOBALS, ident.span, |lint| {
+                let uc = NonSnakeCase::to_snake_case(&name).to_uppercase();
+                let mut err = lint.build(fluent::lint::non_upper_case_global);
+                // We cannot provide meaningful suggestions
+                // if the characters are in the category of "Lowercase Letter".
+                if *name != uc {
+                    err.span_suggestion(
+                        ident.span,
+                        fluent::lint::suggestion,
+                        uc,
+                        Applicability::MaybeIncorrect,
+                    );
+                } else {
+                    err.span_label(ident.span, fluent::lint::label);
+                }
+
+                err.set_arg("sort", sort);
+                err.set_arg("name", name);
+                err.emit();
+            })
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        let attrs = cx.tcx.hir().attrs(it.hir_id());
+        match it.kind {
+            hir::ItemKind::Static(..) if !cx.sess().contains_name(attrs, sym::no_mangle) => {
+                NonUpperCaseGlobals::check_upper_case(cx, "static variable", &it.ident);
+            }
+            hir::ItemKind::Const(..) => {
+                NonUpperCaseGlobals::check_upper_case(cx, "constant", &it.ident);
+            }
+            _ => {}
+        }
+    }
+
+    fn check_trait_item(&mut self, cx: &LateContext<'_>, ti: &hir::TraitItem<'_>) {
+        if let hir::TraitItemKind::Const(..) = ti.kind {
+            NonUpperCaseGlobals::check_upper_case(cx, "associated constant", &ti.ident);
+        }
+    }
+
+    fn check_impl_item(&mut self, cx: &LateContext<'_>, ii: &hir::ImplItem<'_>) {
+        if let hir::ImplItemKind::Const(..) = ii.kind {
+            NonUpperCaseGlobals::check_upper_case(cx, "associated constant", &ii.ident);
+        }
+    }
+
+    fn check_pat(&mut self, cx: &LateContext<'_>, p: &hir::Pat<'_>) {
+        // Lint for constants that look like binding identifiers (#7526)
+        if let PatKind::Path(hir::QPath::Resolved(None, ref path)) = p.kind {
+            if let Res::Def(DefKind::Const, _) = path.res {
+                if path.segments.len() == 1 {
+                    NonUpperCaseGlobals::check_upper_case(
+                        cx,
+                        "constant in pattern",
+                        &path.segments[0].ident,
+                    );
+                }
+            }
+        }
+    }
+
+    fn check_generic_param(&mut self, cx: &LateContext<'_>, param: &hir::GenericParam<'_>) {
+        if let GenericParamKind::Const { .. } = param.kind {
+            NonUpperCaseGlobals::check_upper_case(cx, "const parameter", &param.name.ident());
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;
diff --git a/compiler/rustc_lint/src/nonstandard_style/tests.rs b/compiler/rustc_lint/src/nonstandard_style/tests.rs
new file mode 100644
index 000000000..39c525b86
--- /dev/null
+++ b/compiler/rustc_lint/src/nonstandard_style/tests.rs
@@ -0,0 +1,21 @@
+use super::{is_camel_case, to_camel_case};
+
+#[test]
+fn camel_case() {
+    assert!(!is_camel_case("userData"));
+    assert_eq!(to_camel_case("userData"), "UserData");
+
+    assert!(is_camel_case("X86_64"));
+
+    assert!(!is_camel_case("X86__64"));
+    assert_eq!(to_camel_case("X86__64"), "X86_64");
+
+    assert!(!is_camel_case("Abc_123"));
+    assert_eq!(to_camel_case("Abc_123"), "Abc123");
+
+    assert!(!is_camel_case("A1_b2_c3"));
+    assert_eq!(to_camel_case("A1_b2_c3"), "A1B2C3");
+
+    assert!(!is_camel_case("ONE_TWO_THREE"));
+    assert_eq!(to_camel_case("ONE_TWO_THREE"), "OneTwoThree");
+}
diff --git a/compiler/rustc_lint/src/noop_method_call.rs b/compiler/rustc_lint/src/noop_method_call.rs
new file mode 100644
index 000000000..11a752ff0
--- /dev/null
+++ b/compiler/rustc_lint/src/noop_method_call.rs
@@ -0,0 +1,103 @@
+use crate::context::LintContext;
+use crate::rustc_middle::ty::TypeVisitable;
+use crate::LateContext;
+use crate::LateLintPass;
+use rustc_errors::fluent;
+use rustc_hir::def::DefKind;
+use rustc_hir::{Expr, ExprKind};
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+
+declare_lint! {
+    /// The `noop_method_call` lint detects specific calls to noop methods
+    /// such as a calling `<&T as Clone>::clone` where `T: !Clone`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// #![warn(noop_method_call)]
+    /// struct Foo;
+    /// let foo = &Foo;
+    /// let clone: &Foo = foo.clone();
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Some method calls are noops meaning that they do nothing. Usually such methods
+    /// are the result of blanket implementations that happen to create some method invocations
+    /// that end up not doing anything. For instance, `Clone` is implemented on all `&T`, but
+    /// calling `clone` on a `&T` where `T` does not implement clone, actually doesn't do anything
+    /// as references are copy. This lint detects these calls and warns the user about them.
+    pub NOOP_METHOD_CALL,
+    Allow,
+    "detects the use of well-known noop methods"
+}
+
+declare_lint_pass!(NoopMethodCall => [NOOP_METHOD_CALL]);
+
+impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        // We only care about method calls.
+        let ExprKind::MethodCall(call, elements, _) = &expr.kind else {
+            return
+        };
+        // We only care about method calls corresponding to the `Clone`, `Deref` and `Borrow`
+        // traits and ignore any other method call.
+        let (trait_id, did) = match cx.typeck_results().type_dependent_def(expr.hir_id) {
+            // Verify we are dealing with a method/associated function.
+            Some((DefKind::AssocFn, did)) => match cx.tcx.trait_of_item(did) {
+                // Check that we're dealing with a trait method for one of the traits we care about.
+                Some(trait_id)
+                    if matches!(
+                        cx.tcx.get_diagnostic_name(trait_id),
+                        Some(sym::Borrow | sym::Clone | sym::Deref)
+                    ) =>
+                {
+                    (trait_id, did)
+                }
+                _ => return,
+            },
+            _ => return,
+        };
+        let substs = cx.typeck_results().node_substs(expr.hir_id);
+        if substs.needs_subst() {
+            // We can't resolve on types that require monomorphization, so we don't handle them if
+            // we need to perform substitution.
+            return;
+        }
+        let param_env = cx.tcx.param_env(trait_id);
+        // Resolve the trait method instance.
+        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, param_env, did, substs) else {
+            return
+        };
+        // (Re)check that it implements the noop diagnostic.
+        let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
+        if !matches!(
+            name,
+            sym::noop_method_borrow | sym::noop_method_clone | sym::noop_method_deref
+        ) {
+            return;
+        }
+        let receiver = &elements[0];
+        let receiver_ty = cx.typeck_results().expr_ty(receiver);
+        let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
+        if receiver_ty != expr_ty {
+            // This lint will only trigger if the receiver type and resulting expression \
+            // type are the same, implying that the method call is unnecessary.
+            return;
+        }
+        let expr_span = expr.span;
+        let span = expr_span.with_lo(receiver.span.hi());
+        cx.struct_span_lint(NOOP_METHOD_CALL, span, |lint| {
+            lint.build(fluent::lint::noop_method_call)
+                .set_arg("method", call.ident.name)
+                .set_arg("receiver_ty", receiver_ty)
+                .span_label(span, fluent::lint::label)
+                .note(fluent::lint::note)
+                .emit();
+        });
+    }
+}
diff --git a/compiler/rustc_lint/src/pass_by_value.rs b/compiler/rustc_lint/src/pass_by_value.rs
new file mode 100644
index 000000000..af5e5faf1
--- /dev/null
+++ b/compiler/rustc_lint/src/pass_by_value.rs
@@ -0,0 +1,96 @@
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_errors::{fluent, Applicability};
+use rustc_hir as hir;
+use rustc_hir::def::Res;
+use rustc_hir::{GenericArg, PathSegment, QPath, TyKind};
+use rustc_middle::ty;
+use rustc_span::symbol::sym;
+
+declare_tool_lint! {
+    /// The `rustc_pass_by_value` lint marks a type with `#[rustc_pass_by_value]` requiring it to
+    /// always be passed by value. This is usually used for types that are thin wrappers around
+    /// references, so there is no benefit to an extra layer of indirection. (Example: `Ty` which
+    /// is a reference to an `Interned<TyS>`)
+    pub rustc::PASS_BY_VALUE,
+    Warn,
+    "pass by reference of a type flagged as `#[rustc_pass_by_value]`",
+    report_in_external_macro: true
+}
+
+declare_lint_pass!(PassByValue => [PASS_BY_VALUE]);
+
+impl<'tcx> LateLintPass<'tcx> for PassByValue {
+    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx hir::Ty<'tcx>) {
+        match &ty.kind {
+            TyKind::Rptr(_, hir::MutTy { ty: inner_ty, mutbl: hir::Mutability::Not }) => {
+                if let Some(impl_did) = cx.tcx.impl_of_method(ty.hir_id.owner.to_def_id()) {
+                    if cx.tcx.impl_trait_ref(impl_did).is_some() {
+                        return;
+                    }
+                }
+                if let Some(t) = path_for_pass_by_value(cx, &inner_ty) {
+                    cx.struct_span_lint(PASS_BY_VALUE, ty.span, |lint| {
+                        lint.build(fluent::lint::pass_by_value)
+                            .set_arg("ty", t.clone())
+                            .span_suggestion(
+                                ty.span,
+                                fluent::lint::suggestion,
+                                t,
+                                // Changing type of function argument
+                                Applicability::MaybeIncorrect,
+                            )
+                            .emit();
+                    })
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+fn path_for_pass_by_value(cx: &LateContext<'_>, ty: &hir::Ty<'_>) -> Option<String> {
+    if let TyKind::Path(QPath::Resolved(_, path)) = &ty.kind {
+        match path.res {
+            Res::Def(_, def_id) if cx.tcx.has_attr(def_id, sym::rustc_pass_by_value) => {
+                let name = cx.tcx.item_name(def_id).to_ident_string();
+                let path_segment = path.segments.last().unwrap();
+                return Some(format!("{}{}", name, gen_args(cx, path_segment)));
+            }
+            Res::SelfTy { trait_: None, alias_to: Some((did, _)) } => {
+                if let ty::Adt(adt, substs) = cx.tcx.type_of(did).kind() {
+                    if cx.tcx.has_attr(adt.did(), sym::rustc_pass_by_value) {
+                        return Some(cx.tcx.def_path_str_with_substs(adt.did(), substs));
+                    }
+                }
+            }
+            _ => (),
+        }
+    }
+
+    None
+}
+
+fn gen_args(cx: &LateContext<'_>, segment: &PathSegment<'_>) -> String {
+    if let Some(args) = &segment.args {
+        let params = args
+            .args
+            .iter()
+            .map(|arg| match arg {
+                GenericArg::Lifetime(lt) => lt.name.ident().to_string(),
+                GenericArg::Type(ty) => {
+                    cx.tcx.sess.source_map().span_to_snippet(ty.span).unwrap_or_else(|_| "_".into())
+                }
+                GenericArg::Const(c) => {
+                    cx.tcx.sess.source_map().span_to_snippet(c.span).unwrap_or_else(|_| "_".into())
+                }
+                GenericArg::Infer(_) => String::from("_"),
+            })
+            .collect::<Vec<_>>();
+
+        if !params.is_empty() {
+            return format!("<{}>", params.join(", "));
+        }
+    }
+
+    String::new()
+}
diff --git a/compiler/rustc_lint/src/passes.rs b/compiler/rustc_lint/src/passes.rs
new file mode 100644
index 000000000..cb7bd407e
--- /dev/null
+++ b/compiler/rustc_lint/src/passes.rs
@@ -0,0 +1,249 @@
+use crate::context::{EarlyContext, LateContext};
+
+use rustc_ast as ast;
+use rustc_data_structures::sync;
+use rustc_hir as hir;
+use rustc_session::lint::builtin::HardwiredLints;
+use rustc_session::lint::LintPass;
+use rustc_span::symbol::Ident;
+use rustc_span::Span;
+
+#[macro_export]
+macro_rules! late_lint_methods {
+    ($macro:path, $args:tt, [$hir:tt]) => (
+        $macro!($args, [$hir], [
+            fn check_body(a: &$hir hir::Body<$hir>);
+            fn check_body_post(a: &$hir hir::Body<$hir>);
+            fn check_crate();
+            fn check_crate_post();
+            fn check_mod(a: &$hir hir::Mod<$hir>, b: Span, c: hir::HirId);
+            fn check_foreign_item(a: &$hir hir::ForeignItem<$hir>);
+            fn check_item(a: &$hir hir::Item<$hir>);
+            fn check_item_post(a: &$hir hir::Item<$hir>);
+            fn check_local(a: &$hir hir::Local<$hir>);
+            fn check_block(a: &$hir hir::Block<$hir>);
+            fn check_block_post(a: &$hir hir::Block<$hir>);
+            fn check_stmt(a: &$hir hir::Stmt<$hir>);
+            fn check_arm(a: &$hir hir::Arm<$hir>);
+            fn check_pat(a: &$hir hir::Pat<$hir>);
+            fn check_expr(a: &$hir hir::Expr<$hir>);
+            fn check_expr_post(a: &$hir hir::Expr<$hir>);
+            fn check_ty(a: &$hir hir::Ty<$hir>);
+            fn check_generic_param(a: &$hir hir::GenericParam<$hir>);
+            fn check_generics(a: &$hir hir::Generics<$hir>);
+            fn check_poly_trait_ref(a: &$hir hir::PolyTraitRef<$hir>, b: hir::TraitBoundModifier);
+            fn check_fn(
+                a: rustc_hir::intravisit::FnKind<$hir>,
+                b: &$hir hir::FnDecl<$hir>,
+                c: &$hir hir::Body<$hir>,
+                d: Span,
+                e: hir::HirId);
+            fn check_trait_item(a: &$hir hir::TraitItem<$hir>);
+            fn check_impl_item(a: &$hir hir::ImplItem<$hir>);
+            fn check_impl_item_post(a: &$hir hir::ImplItem<$hir>);
+            fn check_struct_def(a: &$hir hir::VariantData<$hir>);
+            fn check_field_def(a: &$hir hir::FieldDef<$hir>);
+            fn check_variant(a: &$hir hir::Variant<$hir>);
+            fn check_path(a: &$hir hir::Path<$hir>, b: hir::HirId);
+            fn check_attribute(a: &$hir ast::Attribute);
+
+            /// Called when entering a syntax node that can have lint attributes such
+            /// as `#[allow(...)]`. Called with *all* the attributes of that node.
+            fn enter_lint_attrs(a: &$hir [ast::Attribute]);
+
+            /// Counterpart to `enter_lint_attrs`.
+            fn exit_lint_attrs(a: &$hir [ast::Attribute]);
+        ]);
+    )
+}
+
+/// Trait for types providing lint checks.
+///
+/// Each `check` method checks a single syntax node, and should not
+/// invoke methods recursively (unlike `Visitor`). By default they
+/// do nothing.
+//
+// FIXME: eliminate the duplication with `Visitor`. But this also
+// contains a few lint-specific methods with no equivalent in `Visitor`.
+
+macro_rules! expand_lint_pass_methods {
+    ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
+    )
+}
+
+macro_rules! declare_late_lint_pass {
+    ([], [$hir:tt], [$($methods:tt)*]) => (
+        pub trait LateLintPass<$hir>: LintPass {
+            expand_lint_pass_methods!(&LateContext<$hir>, [$($methods)*]);
+        }
+    )
+}
+
+late_lint_methods!(declare_late_lint_pass, [], ['tcx]);
+
+impl LateLintPass<'_> for HardwiredLints {}
+
+#[macro_export]
+macro_rules! expand_combined_late_lint_pass_method {
+    ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
+        $($self.$passes.$name $params;)*
+    })
+}
+
+#[macro_export]
+macro_rules! expand_combined_late_lint_pass_methods {
+    ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &LateContext<'tcx>, $($param: $arg),*) {
+            expand_combined_late_lint_pass_method!($passes, self, $name, (context, $($param),*));
+        })*
+    )
+}
+
+#[macro_export]
+macro_rules! declare_combined_late_lint_pass {
+    ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], [$hir:tt], $methods:tt) => (
+        #[allow(non_snake_case)]
+        $v struct $name {
+            $($passes: $passes,)*
+        }
+
+        impl $name {
+            $v fn new() -> Self {
+                Self {
+                    $($passes: $constructor,)*
+                }
+            }
+
+            $v fn get_lints() -> LintArray {
+                let mut lints = Vec::new();
+                $(lints.extend_from_slice(&$passes::get_lints());)*
+                lints
+            }
+        }
+
+        impl<'tcx> LateLintPass<'tcx> for $name {
+            expand_combined_late_lint_pass_methods!([$($passes),*], $methods);
+        }
+
+        #[allow(rustc::lint_pass_impl_without_macro)]
+        impl LintPass for $name {
+            fn name(&self) -> &'static str {
+                panic!()
+            }
+        }
+    )
+}
+
+#[macro_export]
+macro_rules! early_lint_methods {
+    ($macro:path, $args:tt) => (
+        $macro!($args, [
+            fn check_param(a: &ast::Param);
+            fn check_ident(a: Ident);
+            fn check_crate(a: &ast::Crate);
+            fn check_crate_post(a: &ast::Crate);
+            fn check_item(a: &ast::Item);
+            fn check_item_post(a: &ast::Item);
+            fn check_local(a: &ast::Local);
+            fn check_block(a: &ast::Block);
+            fn check_stmt(a: &ast::Stmt);
+            fn check_arm(a: &ast::Arm);
+            fn check_pat(a: &ast::Pat);
+            fn check_pat_post(a: &ast::Pat);
+            fn check_expr(a: &ast::Expr);
+            fn check_ty(a: &ast::Ty);
+            fn check_generic_arg(a: &ast::GenericArg);
+            fn check_generic_param(a: &ast::GenericParam);
+            fn check_generics(a: &ast::Generics);
+            fn check_poly_trait_ref(a: &ast::PolyTraitRef,
+                                    b: &ast::TraitBoundModifier);
+            fn check_fn(a: rustc_ast::visit::FnKind<'_>, c: Span, d_: ast::NodeId);
+            fn check_trait_item(a: &ast::AssocItem);
+            fn check_impl_item(a: &ast::AssocItem);
+            fn check_variant(a: &ast::Variant);
+            fn check_attribute(a: &ast::Attribute);
+            fn check_mac_def(a: &ast::MacroDef, b: ast::NodeId);
+            fn check_mac(a: &ast::MacCall);
+
+            /// Called when entering a syntax node that can have lint attributes such
+            /// as `#[allow(...)]`. Called with *all* the attributes of that node.
+            fn enter_lint_attrs(a: &[ast::Attribute]);
+
+            /// Counterpart to `enter_lint_attrs`.
+            fn exit_lint_attrs(a: &[ast::Attribute]);
+        ]);
+    )
+}
+
+macro_rules! expand_early_lint_pass_methods {
+    ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
+    )
+}
+
+macro_rules! declare_early_lint_pass {
+    ([], [$($methods:tt)*]) => (
+        pub trait EarlyLintPass: LintPass {
+            expand_early_lint_pass_methods!(&EarlyContext<'_>, [$($methods)*]);
+        }
+    )
+}
+
+early_lint_methods!(declare_early_lint_pass, []);
+
+#[macro_export]
+macro_rules! expand_combined_early_lint_pass_method {
+    ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
+        $($self.$passes.$name $params;)*
+    })
+}
+
+#[macro_export]
+macro_rules! expand_combined_early_lint_pass_methods {
+    ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
+        $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
+            expand_combined_early_lint_pass_method!($passes, self, $name, (context, $($param),*));
+        })*
+    )
+}
+
+#[macro_export]
+macro_rules! declare_combined_early_lint_pass {
+    ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], $methods:tt) => (
+        #[allow(non_snake_case)]
+        $v struct $name {
+            $($passes: $passes,)*
+        }
+
+        impl $name {
+            $v fn new() -> Self {
+                Self {
+                    $($passes: $constructor,)*
+                }
+            }
+
+            $v fn get_lints() -> LintArray {
+                let mut lints = Vec::new();
+                $(lints.extend_from_slice(&$passes::get_lints());)*
+                lints
+            }
+        }
+
+        impl EarlyLintPass for $name {
+            expand_combined_early_lint_pass_methods!([$($passes),*], $methods);
+        }
+
+        #[allow(rustc::lint_pass_impl_without_macro)]
+        impl LintPass for $name {
+            fn name(&self) -> &'static str {
+                panic!()
+            }
+        }
+    )
+}
+
+/// A lint pass boxed up as a trait object.
+pub type EarlyLintPassObject = Box<dyn EarlyLintPass + sync::Send + sync::Sync + 'static>;
+pub type LateLintPassObject =
+    Box<dyn for<'tcx> LateLintPass<'tcx> + sync::Send + sync::Sync + 'static>;
diff --git a/compiler/rustc_lint/src/redundant_semicolon.rs b/compiler/rustc_lint/src/redundant_semicolon.rs
new file mode 100644
index 000000000..26f413453
--- /dev/null
+++ b/compiler/rustc_lint/src/redundant_semicolon.rs
@@ -0,0 +1,58 @@
+use crate::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_ast::{Block, StmtKind};
+use rustc_errors::{fluent, Applicability};
+use rustc_span::Span;
+
+declare_lint! {
+    /// The `redundant_semicolons` lint detects unnecessary trailing
+    /// semicolons.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// let _ = 123;;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Extra semicolons are not needed, and may be removed to avoid confusion
+    /// and visual clutter.
+    pub REDUNDANT_SEMICOLONS,
+    Warn,
+    "detects unnecessary trailing semicolons"
+}
+
+declare_lint_pass!(RedundantSemicolons => [REDUNDANT_SEMICOLONS]);
+
+impl EarlyLintPass for RedundantSemicolons {
+    fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
+        let mut seq = None;
+        for stmt in block.stmts.iter() {
+            match (&stmt.kind, &mut seq) {
+                (StmtKind::Empty, None) => seq = Some((stmt.span, false)),
+                (StmtKind::Empty, Some(seq)) => *seq = (seq.0.to(stmt.span), true),
+                (_, seq) => maybe_lint_redundant_semis(cx, seq),
+            }
+        }
+        maybe_lint_redundant_semis(cx, &mut seq);
+    }
+}
+
+fn maybe_lint_redundant_semis(cx: &EarlyContext<'_>, seq: &mut Option<(Span, bool)>) {
+    if let Some((span, multiple)) = seq.take() {
+        // FIXME: Find a better way of ignoring the trailing
+        // semicolon from macro expansion
+        if span == rustc_span::DUMMY_SP {
+            return;
+        }
+
+        cx.struct_span_lint(REDUNDANT_SEMICOLONS, span, |lint| {
+            lint.build(fluent::lint::redundant_semicolons)
+                .set_arg("multiple", multiple)
+                .span_suggestion(span, fluent::lint::suggestion, "", Applicability::MaybeIncorrect)
+                .emit();
+        });
+    }
+}
diff --git a/compiler/rustc_lint/src/tests.rs b/compiler/rustc_lint/src/tests.rs
new file mode 100644
index 000000000..fc9d6f636
--- /dev/null
+++ b/compiler/rustc_lint/src/tests.rs
@@ -0,0 +1,26 @@
+use crate::context::parse_lint_and_tool_name;
+use rustc_span::{create_default_session_globals_then, Symbol};
+
+#[test]
+fn parse_lint_no_tool() {
+    create_default_session_globals_then(|| {
+        assert_eq!(parse_lint_and_tool_name("foo"), (None, "foo"))
+    });
+}
+
+#[test]
+fn parse_lint_with_tool() {
+    create_default_session_globals_then(|| {
+        assert_eq!(parse_lint_and_tool_name("clippy::foo"), (Some(Symbol::intern("clippy")), "foo"))
+    });
+}
+
+#[test]
+fn parse_lint_multiple_path() {
+    create_default_session_globals_then(|| {
+        assert_eq!(
+            parse_lint_and_tool_name("clippy::foo::bar"),
+            (Some(Symbol::intern("clippy")), "foo::bar")
+        )
+    });
+}
diff --git a/compiler/rustc_lint/src/traits.rs b/compiler/rustc_lint/src/traits.rs
new file mode 100644
index 000000000..df1587c59
--- /dev/null
+++ b/compiler/rustc_lint/src/traits.rs
@@ -0,0 +1,134 @@
+use crate::LateContext;
+use crate::LateLintPass;
+use crate::LintContext;
+use rustc_errors::fluent;
+use rustc_hir as hir;
+use rustc_span::symbol::sym;
+
+declare_lint! {
+    /// The `drop_bounds` lint checks for generics with `std::ops::Drop` as
+    /// bounds.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo<T: Drop>() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// A generic trait bound of the form `T: Drop` is most likely misleading
+    /// and not what the programmer intended (they probably should have used
+    /// `std::mem::needs_drop` instead).
+    ///
+    /// `Drop` bounds do not actually indicate whether a type can be trivially
+    /// dropped or not, because a composite type containing `Drop` types does
+    /// not necessarily implement `Drop` itself. Naïvely, one might be tempted
+    /// to write an implementation that assumes that a type can be trivially
+    /// dropped while also supplying a specialization for `T: Drop` that
+    /// actually calls the destructor. However, this breaks down e.g. when `T`
+    /// is `String`, which does not implement `Drop` itself but contains a
+    /// `Vec`, which does implement `Drop`, so assuming `T` can be trivially
+    /// dropped would lead to a memory leak here.
+    ///
+    /// Furthermore, the `Drop` trait only contains one method, `Drop::drop`,
+    /// which may not be called explicitly in user code (`E0040`), so there is
+    /// really no use case for using `Drop` in trait bounds, save perhaps for
+    /// some obscure corner cases, which can use `#[allow(drop_bounds)]`.
+    pub DROP_BOUNDS,
+    Warn,
+    "bounds of the form `T: Drop` are most likely incorrect"
+}
+
+declare_lint! {
+    /// The `dyn_drop` lint checks for trait objects with `std::ops::Drop`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo(_x: Box<dyn Drop>) {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// A trait object bound of the form `dyn Drop` is most likely misleading
+    /// and not what the programmer intended.
+    ///
+    /// `Drop` bounds do not actually indicate whether a type can be trivially
+    /// dropped or not, because a composite type containing `Drop` types does
+    /// not necessarily implement `Drop` itself. Naïvely, one might be tempted
+    /// to write a deferred drop system, to pull cleaning up memory out of a
+    /// latency-sensitive code path, using `dyn Drop` trait objects. However,
+    /// this breaks down e.g. when `T` is `String`, which does not implement
+    /// `Drop`, but should probably be accepted.
+    ///
+    /// To write a trait object bound that accepts anything, use a placeholder
+    /// trait with a blanket implementation.
+    ///
+    /// ```rust
+    /// trait Placeholder {}
+    /// impl<T> Placeholder for T {}
+    /// fn foo(_x: Box<dyn Placeholder>) {}
+    /// ```
+    pub DYN_DROP,
+    Warn,
+    "trait objects of the form `dyn Drop` are useless"
+}
+
+declare_lint_pass!(
+    /// Lint for bounds of the form `T: Drop`, which usually
+    /// indicate an attempt to emulate `std::mem::needs_drop`.
+    DropTraitConstraints => [DROP_BOUNDS, DYN_DROP]
+);
+
+impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
+        use rustc_middle::ty::PredicateKind::*;
+
+        let predicates = cx.tcx.explicit_predicates_of(item.def_id);
+        for &(predicate, span) in predicates.predicates {
+            let Trait(trait_predicate) = predicate.kind().skip_binder() else {
+                continue
+            };
+            let def_id = trait_predicate.trait_ref.def_id;
+            if cx.tcx.lang_items().drop_trait() == Some(def_id) {
+                // Explicitly allow `impl Drop`, a drop-guards-as-Voldemort-type pattern.
+                if trait_predicate.trait_ref.self_ty().is_impl_trait() {
+                    continue;
+                }
+                cx.struct_span_lint(DROP_BOUNDS, span, |lint| {
+                    let Some(needs_drop) = cx.tcx.get_diagnostic_item(sym::needs_drop) else {
+                        return
+                    };
+                    lint.build(fluent::lint::drop_trait_constraints)
+                        .set_arg("predicate", predicate)
+                        .set_arg("needs_drop", cx.tcx.def_path_str(needs_drop))
+                        .emit();
+                });
+            }
+        }
+    }
+
+    fn check_ty(&mut self, cx: &LateContext<'_>, ty: &'tcx hir::Ty<'tcx>) {
+        let hir::TyKind::TraitObject(bounds, _lifetime, _syntax) = &ty.kind else {
+            return
+        };
+        for bound in &bounds[..] {
+            let def_id = bound.trait_ref.trait_def_id();
+            if cx.tcx.lang_items().drop_trait() == def_id {
+                cx.struct_span_lint(DYN_DROP, bound.span, |lint| {
+                    let Some(needs_drop) = cx.tcx.get_diagnostic_item(sym::needs_drop) else {
+                        return
+                    };
+                    lint.build(fluent::lint::drop_glue)
+                        .set_arg("needs_drop", cx.tcx.def_path_str(needs_drop))
+                        .emit();
+                });
+            }
+        }
+    }
+}
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
new file mode 100644
index 000000000..5c07afeb7
--- /dev/null
+++ b/compiler/rustc_lint/src/types.rs
@@ -0,0 +1,1576 @@
+use crate::{LateContext, LateLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_attr as attr;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{fluent, Applicability, DiagnosticMessage};
+use rustc_hir as hir;
+use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
+use rustc_macros::LintDiagnostic;
+use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
+use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable};
+use rustc_span::source_map;
+use rustc_span::symbol::sym;
+use rustc_span::{Span, Symbol, DUMMY_SP};
+use rustc_target::abi::{Abi, WrappingRange};
+use rustc_target::abi::{Integer, TagEncoding, Variants};
+use rustc_target::spec::abi::Abi as SpecAbi;
+
+use std::cmp;
+use std::iter;
+use std::ops::ControlFlow;
+use tracing::debug;
+
+declare_lint! {
+    /// The `unused_comparisons` lint detects comparisons made useless by
+    /// limits of the types involved.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn foo(x: u8) {
+    ///     x >= 0;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// A useless comparison may indicate a mistake, and should be fixed or
+    /// removed.
+    UNUSED_COMPARISONS,
+    Warn,
+    "comparisons made useless by limits of the types involved"
+}
+
+declare_lint! {
+    /// The `overflowing_literals` lint detects literal out of range for its
+    /// type.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// let x: u8 = 1000;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// It is usually a mistake to use a literal that overflows the type where
+    /// it is used. Either use a literal that is within range, or change the
+    /// type to be within the range of the literal.
+    OVERFLOWING_LITERALS,
+    Deny,
+    "literal out of range for its type"
+}
+
+declare_lint! {
+    /// The `variant_size_differences` lint detects enums with widely varying
+    /// variant sizes.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(variant_size_differences)]
+    /// enum En {
+    ///     V0(u8),
+    ///     VBig([u8; 1024]),
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// It can be a mistake to add a variant to an enum that is much larger
+    /// than the other variants, bloating the overall size required for all
+    /// variants. This can impact performance and memory usage. This is
+    /// triggered if one variant is more than 3 times larger than the
+    /// second-largest variant.
+    ///
+    /// Consider placing the large variant's contents on the heap (for example
+    /// via [`Box`]) to keep the overall size of the enum itself down.
+    ///
+    /// This lint is "allow" by default because it can be noisy, and may not be
+    /// an actual problem. Decisions about this should be guided with
+    /// profiling and benchmarking.
+    ///
+    /// [`Box`]: https://doc.rust-lang.org/std/boxed/index.html
+    VARIANT_SIZE_DIFFERENCES,
+    Allow,
+    "detects enums with widely varying variant sizes"
+}
+
+#[derive(Copy, Clone)]
+pub struct TypeLimits {
+    /// Id of the last visited negated expression
+    negated_expr_id: Option<hir::HirId>,
+}
+
+impl_lint_pass!(TypeLimits => [UNUSED_COMPARISONS, OVERFLOWING_LITERALS]);
+
+impl TypeLimits {
+    pub fn new() -> TypeLimits {
+        TypeLimits { negated_expr_id: None }
+    }
+}
+
+/// Attempts to special-case the overflowing literal lint when it occurs as a range endpoint.
+/// Returns `true` iff the lint was overridden.
+fn lint_overflowing_range_endpoint<'tcx>(
+    cx: &LateContext<'tcx>,
+    lit: &hir::Lit,
+    lit_val: u128,
+    max: u128,
+    expr: &'tcx hir::Expr<'tcx>,
+    parent_expr: &'tcx hir::Expr<'tcx>,
+    ty: &str,
+) -> bool {
+    // We only want to handle exclusive (`..`) ranges,
+    // which are represented as `ExprKind::Struct`.
+    let mut overwritten = false;
+    if let ExprKind::Struct(_, eps, _) = &parent_expr.kind {
+        if eps.len() != 2 {
+            return false;
+        }
+        // We can suggest using an inclusive range
+        // (`..=`) instead only if it is the `end` that is
+        // overflowing and only by 1.
+        if eps[1].expr.hir_id == expr.hir_id && lit_val - 1 == max {
+            cx.struct_span_lint(OVERFLOWING_LITERALS, parent_expr.span, |lint| {
+                let mut err = lint.build(fluent::lint::range_endpoint_out_of_range);
+                err.set_arg("ty", ty);
+                if let Ok(start) = cx.sess().source_map().span_to_snippet(eps[0].span) {
+                    use ast::{LitIntType, LitKind};
+                    // We need to preserve the literal's suffix,
+                    // as it may determine typing information.
+                    let suffix = match lit.node {
+                        LitKind::Int(_, LitIntType::Signed(s)) => s.name_str(),
+                        LitKind::Int(_, LitIntType::Unsigned(s)) => s.name_str(),
+                        LitKind::Int(_, LitIntType::Unsuffixed) => "",
+                        _ => bug!(),
+                    };
+                    let suggestion = format!("{}..={}{}", start, lit_val - 1, suffix);
+                    err.span_suggestion(
+                        parent_expr.span,
+                        fluent::lint::suggestion,
+                        suggestion,
+                        Applicability::MachineApplicable,
+                    );
+                    err.emit();
+                    overwritten = true;
+                }
+            });
+        }
+    }
+    overwritten
+}
+
+// For `isize` & `usize`, be conservative with the warnings, so that the
+// warnings are consistent between 32- and 64-bit platforms.
+fn int_ty_range(int_ty: ty::IntTy) -> (i128, i128) {
+    match int_ty {
+        ty::IntTy::Isize => (i64::MIN.into(), i64::MAX.into()),
+        ty::IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
+        ty::IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
+        ty::IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
+        ty::IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
+        ty::IntTy::I128 => (i128::MIN, i128::MAX),
+    }
+}
+
+fn uint_ty_range(uint_ty: ty::UintTy) -> (u128, u128) {
+    let max = match uint_ty {
+        ty::UintTy::Usize => u64::MAX.into(),
+        ty::UintTy::U8 => u8::MAX.into(),
+        ty::UintTy::U16 => u16::MAX.into(),
+        ty::UintTy::U32 => u32::MAX.into(),
+        ty::UintTy::U64 => u64::MAX.into(),
+        ty::UintTy::U128 => u128::MAX,
+    };
+    (0, max)
+}
+
+fn get_bin_hex_repr(cx: &LateContext<'_>, lit: &hir::Lit) -> Option<String> {
+    let src = cx.sess().source_map().span_to_snippet(lit.span).ok()?;
+    let firstch = src.chars().next()?;
+
+    if firstch == '0' {
+        match src.chars().nth(1) {
+            Some('x' | 'b') => return Some(src),
+            _ => return None,
+        }
+    }
+
+    None
+}
+
+fn report_bin_hex_error(
+    cx: &LateContext<'_>,
+    expr: &hir::Expr<'_>,
+    ty: attr::IntType,
+    repr_str: String,
+    val: u128,
+    negative: bool,
+) {
+    let size = Integer::from_attr(&cx.tcx, ty).size();
+    cx.struct_span_lint(OVERFLOWING_LITERALS, expr.span, |lint| {
+        let (t, actually) = match ty {
+            attr::IntType::SignedInt(t) => {
+                let actually = if negative {
+                    -(size.sign_extend(val) as i128)
+                } else {
+                    size.sign_extend(val) as i128
+                };
+                (t.name_str(), actually.to_string())
+            }
+            attr::IntType::UnsignedInt(t) => {
+                let actually = size.truncate(val);
+                (t.name_str(), actually.to_string())
+            }
+        };
+        let mut err = lint.build(fluent::lint::overflowing_bin_hex);
+        if negative {
+            // If the value is negative,
+            // emits a note about the value itself, apart from the literal.
+            err.note(fluent::lint::negative_note);
+            err.note(fluent::lint::negative_becomes_note);
+        } else {
+            err.note(fluent::lint::positive_note);
+        }
+        if let Some(sugg_ty) =
+            get_type_suggestion(cx.typeck_results().node_type(expr.hir_id), val, negative)
+        {
+            err.set_arg("suggestion_ty", sugg_ty);
+            if let Some(pos) = repr_str.chars().position(|c| c == 'i' || c == 'u') {
+                let (sans_suffix, _) = repr_str.split_at(pos);
+                err.span_suggestion(
+                    expr.span,
+                    fluent::lint::suggestion,
+                    format!("{}{}", sans_suffix, sugg_ty),
+                    Applicability::MachineApplicable,
+                );
+            } else {
+                err.help(fluent::lint::help);
+            }
+        }
+        err.set_arg("ty", t);
+        err.set_arg("lit", repr_str);
+        err.set_arg("dec", val);
+        err.set_arg("actually", actually);
+        err.emit();
+    });
+}
+
+// This function finds the next fitting type and generates a suggestion string.
+// It searches for fitting types in the following way (`X < Y`):
+//  - `iX`: if literal fits in `uX` => `uX`, else => `iY`
+//  - `-iX` => `iY`
+//  - `uX` => `uY`
+//
+// No suggestion for: `isize`, `usize`.
+fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static str> {
+    use ty::IntTy::*;
+    use ty::UintTy::*;
+    macro_rules! find_fit {
+        ($ty:expr, $val:expr, $negative:expr,
+         $($type:ident => [$($utypes:expr),*] => [$($itypes:expr),*]),+) => {
+            {
+                let _neg = if negative { 1 } else { 0 };
+                match $ty {
+                    $($type => {
+                        $(if !negative && val <= uint_ty_range($utypes).1 {
+                            return Some($utypes.name_str())
+                        })*
+                        $(if val <= int_ty_range($itypes).1 as u128 + _neg {
+                            return Some($itypes.name_str())
+                        })*
+                        None
+                    },)+
+                    _ => None
+                }
+            }
+        }
+    }
+    match t.kind() {
+        ty::Int(i) => find_fit!(i, val, negative,
+                      I8 => [U8] => [I16, I32, I64, I128],
+                      I16 => [U16] => [I32, I64, I128],
+                      I32 => [U32] => [I64, I128],
+                      I64 => [U64] => [I128],
+                      I128 => [U128] => []),
+        ty::Uint(u) => find_fit!(u, val, negative,
+                      U8 => [U8, U16, U32, U64, U128] => [],
+                      U16 => [U16, U32, U64, U128] => [],
+                      U32 => [U32, U64, U128] => [],
+                      U64 => [U64, U128] => [],
+                      U128 => [U128] => []),
+        _ => None,
+    }
+}
+
+fn lint_int_literal<'tcx>(
+    cx: &LateContext<'tcx>,
+    type_limits: &TypeLimits,
+    e: &'tcx hir::Expr<'tcx>,
+    lit: &hir::Lit,
+    t: ty::IntTy,
+    v: u128,
+) {
+    let int_type = t.normalize(cx.sess().target.pointer_width);
+    let (min, max) = int_ty_range(int_type);
+    let max = max as u128;
+    let negative = type_limits.negated_expr_id == Some(e.hir_id);
+
+    // Detect literal value out of range [min, max] inclusive
+    // avoiding use of -min to prevent overflow/panic
+    if (negative && v > max + 1) || (!negative && v > max) {
+        if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
+            report_bin_hex_error(
+                cx,
+                e,
+                attr::IntType::SignedInt(ty::ast_int_ty(t)),
+                repr_str,
+                v,
+                negative,
+            );
+            return;
+        }
+
+        let par_id = cx.tcx.hir().get_parent_node(e.hir_id);
+        if let Node::Expr(par_e) = cx.tcx.hir().get(par_id) {
+            if let hir::ExprKind::Struct(..) = par_e.kind {
+                if is_range_literal(par_e)
+                    && lint_overflowing_range_endpoint(cx, lit, v, max, e, par_e, t.name_str())
+                {
+                    // The overflowing literal lint was overridden.
+                    return;
+                }
+            }
+        }
+
+        cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
+            let mut err = lint.build(fluent::lint::overflowing_int);
+            err.set_arg("ty", t.name_str());
+            err.set_arg(
+                "lit",
+                cx.sess()
+                    .source_map()
+                    .span_to_snippet(lit.span)
+                    .expect("must get snippet from literal"),
+            );
+            err.set_arg("min", min);
+            err.set_arg("max", max);
+            err.note(fluent::lint::note);
+            if let Some(sugg_ty) =
+                get_type_suggestion(cx.typeck_results().node_type(e.hir_id), v, negative)
+            {
+                err.set_arg("suggestion_ty", sugg_ty);
+                err.help(fluent::lint::help);
+            }
+            err.emit();
+        });
+    }
+}
+
+fn lint_uint_literal<'tcx>(
+    cx: &LateContext<'tcx>,
+    e: &'tcx hir::Expr<'tcx>,
+    lit: &hir::Lit,
+    t: ty::UintTy,
+) {
+    let uint_type = t.normalize(cx.sess().target.pointer_width);
+    let (min, max) = uint_ty_range(uint_type);
+    let lit_val: u128 = match lit.node {
+        // _v is u8, within range by definition
+        ast::LitKind::Byte(_v) => return,
+        ast::LitKind::Int(v, _) => v,
+        _ => bug!(),
+    };
+    if lit_val < min || lit_val > max {
+        let parent_id = cx.tcx.hir().get_parent_node(e.hir_id);
+        if let Node::Expr(par_e) = cx.tcx.hir().get(parent_id) {
+            match par_e.kind {
+                hir::ExprKind::Cast(..) => {
+                    if let ty::Char = cx.typeck_results().expr_ty(par_e).kind() {
+                        cx.struct_span_lint(OVERFLOWING_LITERALS, par_e.span, |lint| {
+                            lint.build(fluent::lint::only_cast_u8_to_char)
+                                .span_suggestion(
+                                    par_e.span,
+                                    fluent::lint::suggestion,
+                                    format!("'\\u{{{:X}}}'", lit_val),
+                                    Applicability::MachineApplicable,
+                                )
+                                .emit();
+                        });
+                        return;
+                    }
+                }
+                hir::ExprKind::Struct(..) if is_range_literal(par_e) => {
+                    let t = t.name_str();
+                    if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, par_e, t) {
+                        // The overflowing literal lint was overridden.
+                        return;
+                    }
+                }
+                _ => {}
+            }
+        }
+        if let Some(repr_str) = get_bin_hex_repr(cx, lit) {
+            report_bin_hex_error(
+                cx,
+                e,
+                attr::IntType::UnsignedInt(ty::ast_uint_ty(t)),
+                repr_str,
+                lit_val,
+                false,
+            );
+            return;
+        }
+        cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
+            lint.build(fluent::lint::overflowing_uint)
+                .set_arg("ty", t.name_str())
+                .set_arg(
+                    "lit",
+                    cx.sess()
+                        .source_map()
+                        .span_to_snippet(lit.span)
+                        .expect("must get snippet from literal"),
+                )
+                .set_arg("min", min)
+                .set_arg("max", max)
+                .note(fluent::lint::note)
+                .emit();
+        });
+    }
+}
+
+fn lint_literal<'tcx>(
+    cx: &LateContext<'tcx>,
+    type_limits: &TypeLimits,
+    e: &'tcx hir::Expr<'tcx>,
+    lit: &hir::Lit,
+) {
+    match *cx.typeck_results().node_type(e.hir_id).kind() {
+        ty::Int(t) => {
+            match lit.node {
+                ast::LitKind::Int(v, ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed) => {
+                    lint_int_literal(cx, type_limits, e, lit, t, v)
+                }
+                _ => bug!(),
+            };
+        }
+        ty::Uint(t) => lint_uint_literal(cx, e, lit, t),
+        ty::Float(t) => {
+            let is_infinite = match lit.node {
+                ast::LitKind::Float(v, _) => match t {
+                    ty::FloatTy::F32 => v.as_str().parse().map(f32::is_infinite),
+                    ty::FloatTy::F64 => v.as_str().parse().map(f64::is_infinite),
+                },
+                _ => bug!(),
+            };
+            if is_infinite == Ok(true) {
+                cx.struct_span_lint(OVERFLOWING_LITERALS, e.span, |lint| {
+                    lint.build(fluent::lint::overflowing_literal)
+                        .set_arg("ty", t.name_str())
+                        .set_arg(
+                            "lit",
+                            cx.sess()
+                                .source_map()
+                                .span_to_snippet(lit.span)
+                                .expect("must get snippet from literal"),
+                        )
+                        .note(fluent::lint::note)
+                        .emit();
+                });
+            }
+        }
+        _ => {}
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for TypeLimits {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx hir::Expr<'tcx>) {
+        match e.kind {
+            hir::ExprKind::Unary(hir::UnOp::Neg, ref expr) => {
+                // propagate negation, if the negation itself isn't negated
+                if self.negated_expr_id != Some(e.hir_id) {
+                    self.negated_expr_id = Some(expr.hir_id);
+                }
+            }
+            hir::ExprKind::Binary(binop, ref l, ref r) => {
+                if is_comparison(binop) && !check_limits(cx, binop, &l, &r) {
+                    cx.struct_span_lint(UNUSED_COMPARISONS, e.span, |lint| {
+                        lint.build(fluent::lint::unused_comparisons).emit();
+                    });
+                }
+            }
+            hir::ExprKind::Lit(ref lit) => lint_literal(cx, self, e, lit),
+            _ => {}
+        };
+
+        fn is_valid<T: cmp::PartialOrd>(binop: hir::BinOp, v: T, min: T, max: T) -> bool {
+            match binop.node {
+                hir::BinOpKind::Lt => v > min && v <= max,
+                hir::BinOpKind::Le => v >= min && v < max,
+                hir::BinOpKind::Gt => v >= min && v < max,
+                hir::BinOpKind::Ge => v > min && v <= max,
+                hir::BinOpKind::Eq | hir::BinOpKind::Ne => v >= min && v <= max,
+                _ => bug!(),
+            }
+        }
+
+        fn rev_binop(binop: hir::BinOp) -> hir::BinOp {
+            source_map::respan(
+                binop.span,
+                match binop.node {
+                    hir::BinOpKind::Lt => hir::BinOpKind::Gt,
+                    hir::BinOpKind::Le => hir::BinOpKind::Ge,
+                    hir::BinOpKind::Gt => hir::BinOpKind::Lt,
+                    hir::BinOpKind::Ge => hir::BinOpKind::Le,
+                    _ => return binop,
+                },
+            )
+        }
+
+        fn check_limits(
+            cx: &LateContext<'_>,
+            binop: hir::BinOp,
+            l: &hir::Expr<'_>,
+            r: &hir::Expr<'_>,
+        ) -> bool {
+            let (lit, expr, swap) = match (&l.kind, &r.kind) {
+                (&hir::ExprKind::Lit(_), _) => (l, r, true),
+                (_, &hir::ExprKind::Lit(_)) => (r, l, false),
+                _ => return true,
+            };
+            // Normalize the binop so that the literal is always on the RHS in
+            // the comparison
+            let norm_binop = if swap { rev_binop(binop) } else { binop };
+            match *cx.typeck_results().node_type(expr.hir_id).kind() {
+                ty::Int(int_ty) => {
+                    let (min, max) = int_ty_range(int_ty);
+                    let lit_val: i128 = match lit.kind {
+                        hir::ExprKind::Lit(ref li) => match li.node {
+                            ast::LitKind::Int(
+                                v,
+                                ast::LitIntType::Signed(_) | ast::LitIntType::Unsuffixed,
+                            ) => v as i128,
+                            _ => return true,
+                        },
+                        _ => bug!(),
+                    };
+                    is_valid(norm_binop, lit_val, min, max)
+                }
+                ty::Uint(uint_ty) => {
+                    let (min, max): (u128, u128) = uint_ty_range(uint_ty);
+                    let lit_val: u128 = match lit.kind {
+                        hir::ExprKind::Lit(ref li) => match li.node {
+                            ast::LitKind::Int(v, _) => v,
+                            _ => return true,
+                        },
+                        _ => bug!(),
+                    };
+                    is_valid(norm_binop, lit_val, min, max)
+                }
+                _ => true,
+            }
+        }
+
+        fn is_comparison(binop: hir::BinOp) -> bool {
+            matches!(
+                binop.node,
+                hir::BinOpKind::Eq
+                    | hir::BinOpKind::Lt
+                    | hir::BinOpKind::Le
+                    | hir::BinOpKind::Ne
+                    | hir::BinOpKind::Ge
+                    | hir::BinOpKind::Gt
+            )
+        }
+    }
+}
+
+declare_lint! {
+    /// The `improper_ctypes` lint detects incorrect use of types in foreign
+    /// modules.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// extern "C" {
+    ///     static STATIC: String;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The compiler has several checks to verify that types used in `extern`
+    /// blocks are safe and follow certain rules to ensure proper
+    /// compatibility with the foreign interfaces. This lint is issued when it
+    /// detects a probable mistake in a definition. The lint usually should
+    /// provide a description of the issue, along with possibly a hint on how
+    /// to resolve it.
+    IMPROPER_CTYPES,
+    Warn,
+    "proper use of libc types in foreign modules"
+}
+
+declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
+
+declare_lint! {
+    /// The `improper_ctypes_definitions` lint detects incorrect use of
+    /// [`extern` function] definitions.
+    ///
+    /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// pub extern "C" fn str_type(p: &str) { }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// There are many parameter and return types that may be specified in an
+    /// `extern` function that are not compatible with the given ABI. This
+    /// lint is an alert that these types should not be used. The lint usually
+    /// should provide a description of the issue, along with possibly a hint
+    /// on how to resolve it.
+    IMPROPER_CTYPES_DEFINITIONS,
+    Warn,
+    "proper use of libc types in foreign item definitions"
+}
+
+declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS]);
+
+#[derive(Clone, Copy)]
+pub(crate) enum CItemKind {
+    Declaration,
+    Definition,
+}
+
+struct ImproperCTypesVisitor<'a, 'tcx> {
+    cx: &'a LateContext<'tcx>,
+    mode: CItemKind,
+}
+
+enum FfiResult<'tcx> {
+    FfiSafe,
+    FfiPhantom(Ty<'tcx>),
+    FfiUnsafe { ty: Ty<'tcx>, reason: DiagnosticMessage, help: Option<DiagnosticMessage> },
+}
+
+pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    def: ty::AdtDef<'tcx>,
+) -> bool {
+    tcx.has_attr(def.did(), sym::rustc_nonnull_optimization_guaranteed)
+}
+
+/// `repr(transparent)` structs can have a single non-ZST field, this function returns that
+/// field.
+pub fn transparent_newtype_field<'a, 'tcx>(
+    tcx: TyCtxt<'tcx>,
+    variant: &'a ty::VariantDef,
+) -> Option<&'a ty::FieldDef> {
+    let param_env = tcx.param_env(variant.def_id);
+    variant.fields.iter().find(|field| {
+        let field_ty = tcx.type_of(field.did);
+        let is_zst = tcx.layout_of(param_env.and(field_ty)).map_or(false, |layout| layout.is_zst());
+        !is_zst
+    })
+}
+
+/// Is type known to be non-null?
+fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKind) -> bool {
+    let tcx = cx.tcx;
+    match ty.kind() {
+        ty::FnPtr(_) => true,
+        ty::Ref(..) => true,
+        ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
+        ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
+            let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
+
+            if marked_non_null {
+                return true;
+            }
+
+            // `UnsafeCell` has its niche hidden.
+            if def.is_unsafe_cell() {
+                return false;
+            }
+
+            def.variants()
+                .iter()
+                .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
+                .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
+        }
+        _ => false,
+    }
+}
+
+/// Given a non-null scalar (or transparent) type `ty`, return the nullable version of that type.
+/// If the type passed in was not scalar, returns None.
+fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
+    let tcx = cx.tcx;
+    Some(match *ty.kind() {
+        ty::Adt(field_def, field_substs) => {
+            let inner_field_ty = {
+                let first_non_zst_ty = field_def
+                    .variants()
+                    .iter()
+                    .filter_map(|v| transparent_newtype_field(cx.tcx, v));
+                debug_assert_eq!(
+                    first_non_zst_ty.clone().count(),
+                    1,
+                    "Wrong number of fields for transparent type"
+                );
+                first_non_zst_ty
+                    .last()
+                    .expect("No non-zst fields in transparent type.")
+                    .ty(tcx, field_substs)
+            };
+            return get_nullable_type(cx, inner_field_ty);
+        }
+        ty::Int(ty) => tcx.mk_mach_int(ty),
+        ty::Uint(ty) => tcx.mk_mach_uint(ty),
+        ty::RawPtr(ty_mut) => tcx.mk_ptr(ty_mut),
+        // As these types are always non-null, the nullable equivalent of
+        // Option<T> of these types are their raw pointer counterparts.
+        ty::Ref(_region, ty, mutbl) => tcx.mk_ptr(ty::TypeAndMut { ty, mutbl }),
+        ty::FnPtr(..) => {
+            // There is no nullable equivalent for Rust's function pointers -- you
+            // must use an Option<fn(..) -> _> to represent it.
+            ty
+        }
+
+        // We should only ever reach this case if ty_is_known_nonnull is extended
+        // to other types.
+        ref unhandled => {
+            debug!(
+                "get_nullable_type: Unhandled scalar kind: {:?} while checking {:?}",
+                unhandled, ty
+            );
+            return None;
+        }
+    })
+}
+
+/// Check if this enum can be safely exported based on the "nullable pointer optimization". If it
+/// can, return the type that `ty` can be safely converted to, otherwise return `None`.
+/// Currently restricted to function pointers, boxes, references, `core::num::NonZero*`,
+/// `core::ptr::NonNull`, and `#[repr(transparent)]` newtypes.
+/// FIXME: This duplicates code in codegen.
+pub(crate) fn repr_nullable_ptr<'tcx>(
+    cx: &LateContext<'tcx>,
+    ty: Ty<'tcx>,
+    ckind: CItemKind,
+) -> Option<Ty<'tcx>> {
+    debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
+    if let ty::Adt(ty_def, substs) = ty.kind() {
+        let field_ty = match &ty_def.variants().raw[..] {
+            [var_one, var_two] => match (&var_one.fields[..], &var_two.fields[..]) {
+                ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
+                _ => return None,
+            },
+            _ => return None,
+        };
+
+        if !ty_is_known_nonnull(cx, field_ty, ckind) {
+            return None;
+        }
+
+        // At this point, the field's type is known to be nonnull and the parent enum is Option-like.
+        // If the computed size for the field and the enum are different, the nonnull optimization isn't
+        // being applied (and we've got a problem somewhere).
+        let compute_size_skeleton = |t| SizeSkeleton::compute(t, cx.tcx, cx.param_env).unwrap();
+        if !compute_size_skeleton(ty).same_size(compute_size_skeleton(field_ty)) {
+            bug!("improper_ctypes: Option nonnull optimization not applied?");
+        }
+
+        // Return the nullable type this Option-like enum can be safely represented with.
+        let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
+        if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
+            match field_ty_scalar.valid_range(cx) {
+                WrappingRange { start: 0, end }
+                    if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
+                {
+                    return Some(get_nullable_type(cx, field_ty).unwrap());
+                }
+                WrappingRange { start: 1, .. } => {
+                    return Some(get_nullable_type(cx, field_ty).unwrap());
+                }
+                WrappingRange { start, end } => {
+                    unreachable!("Unhandled start and end range: ({}, {})", start, end)
+                }
+            };
+        }
+    }
+    None
+}
+
+impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
+    /// Check if the type is array and emit an unsafe type lint.
+    fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
+        if let ty::Array(..) = ty.kind() {
+            self.emit_ffi_unsafe_type_lint(
+                ty,
+                sp,
+                fluent::lint::improper_ctypes_array_reason,
+                Some(fluent::lint::improper_ctypes_array_help),
+            );
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Checks if the given field's type is "ffi-safe".
+    fn check_field_type_for_ffi(
+        &self,
+        cache: &mut FxHashSet<Ty<'tcx>>,
+        field: &ty::FieldDef,
+        substs: SubstsRef<'tcx>,
+    ) -> FfiResult<'tcx> {
+        let field_ty = field.ty(self.cx.tcx, substs);
+        if field_ty.has_opaque_types() {
+            self.check_type_for_ffi(cache, field_ty)
+        } else {
+            let field_ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, field_ty);
+            self.check_type_for_ffi(cache, field_ty)
+        }
+    }
+
+    /// Checks if the given `VariantDef`'s field types are "ffi-safe".
+    fn check_variant_for_ffi(
+        &self,
+        cache: &mut FxHashSet<Ty<'tcx>>,
+        ty: Ty<'tcx>,
+        def: ty::AdtDef<'tcx>,
+        variant: &ty::VariantDef,
+        substs: SubstsRef<'tcx>,
+    ) -> FfiResult<'tcx> {
+        use FfiResult::*;
+
+        if def.repr().transparent() {
+            // Can assume that at most one field is not a ZST, so only check
+            // that field's type for FFI-safety.
+            if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
+                self.check_field_type_for_ffi(cache, field, substs)
+            } else {
+                // All fields are ZSTs; this means that the type should behave
+                // like (), which is FFI-unsafe
+                FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_struct_zst, help: None }
+            }
+        } else {
+            // We can't completely trust repr(C) markings; make sure the fields are
+            // actually safe.
+            let mut all_phantom = !variant.fields.is_empty();
+            for field in &variant.fields {
+                match self.check_field_type_for_ffi(cache, &field, substs) {
+                    FfiSafe => {
+                        all_phantom = false;
+                    }
+                    FfiPhantom(..) if def.is_enum() => {
+                        return FfiUnsafe {
+                            ty,
+                            reason: fluent::lint::improper_ctypes_enum_phantomdata,
+                            help: None,
+                        };
+                    }
+                    FfiPhantom(..) => {}
+                    r => return r,
+                }
+            }
+
+            if all_phantom { FfiPhantom(ty) } else { FfiSafe }
+        }
+    }
+
+    /// Checks if the given type is "ffi-safe" (has a stable, well-defined
+    /// representation which can be exported to C code).
+    fn check_type_for_ffi(&self, cache: &mut FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>) -> FfiResult<'tcx> {
+        use FfiResult::*;
+
+        let tcx = self.cx.tcx;
+
+        // Protect against infinite recursion, for example
+        // `struct S(*mut S);`.
+        // FIXME: A recursion limit is necessary as well, for irregular
+        // recursive types.
+        if !cache.insert(ty) {
+            return FfiSafe;
+        }
+
+        match *ty.kind() {
+            ty::Adt(def, substs) => {
+                if def.is_box() && matches!(self.mode, CItemKind::Definition) {
+                    if ty.boxed_ty().is_sized(tcx.at(DUMMY_SP), self.cx.param_env) {
+                        return FfiSafe;
+                    } else {
+                        return FfiUnsafe {
+                            ty,
+                            reason: fluent::lint::improper_ctypes_box,
+                            help: None,
+                        };
+                    }
+                }
+                if def.is_phantom_data() {
+                    return FfiPhantom(ty);
+                }
+                match def.adt_kind() {
+                    AdtKind::Struct | AdtKind::Union => {
+                        if !def.repr().c() && !def.repr().transparent() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint::improper_ctypes_struct_layout_reason
+                                } else {
+                                    fluent::lint::improper_ctypes_union_layout_reason
+                                },
+                                help: if def.is_struct() {
+                                    Some(fluent::lint::improper_ctypes_struct_layout_help)
+                                } else {
+                                    Some(fluent::lint::improper_ctypes_union_layout_help)
+                                },
+                            };
+                        }
+
+                        let is_non_exhaustive =
+                            def.non_enum_variant().is_field_list_non_exhaustive();
+                        if is_non_exhaustive && !def.did().is_local() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint::improper_ctypes_struct_non_exhaustive
+                                } else {
+                                    fluent::lint::improper_ctypes_union_non_exhaustive
+                                },
+                                help: None,
+                            };
+                        }
+
+                        if def.non_enum_variant().fields.is_empty() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint::improper_ctypes_struct_fieldless_reason
+                                } else {
+                                    fluent::lint::improper_ctypes_union_fieldless_reason
+                                },
+                                help: if def.is_struct() {
+                                    Some(fluent::lint::improper_ctypes_struct_fieldless_help)
+                                } else {
+                                    Some(fluent::lint::improper_ctypes_union_fieldless_help)
+                                },
+                            };
+                        }
+
+                        self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
+                    }
+                    AdtKind::Enum => {
+                        if def.variants().is_empty() {
+                            // Empty enums are okay... although sort of useless.
+                            return FfiSafe;
+                        }
+
+                        // Check for a repr() attribute to specify the size of the
+                        // discriminant.
+                        if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
+                        {
+                            // Special-case types like `Option<extern fn()>`.
+                            if repr_nullable_ptr(self.cx, ty, self.mode).is_none() {
+                                return FfiUnsafe {
+                                    ty,
+                                    reason: fluent::lint::improper_ctypes_enum_repr_reason,
+                                    help: Some(fluent::lint::improper_ctypes_enum_repr_help),
+                                };
+                            }
+                        }
+
+                        if def.is_variant_list_non_exhaustive() && !def.did().is_local() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: fluent::lint::improper_ctypes_non_exhaustive,
+                                help: None,
+                            };
+                        }
+
+                        // Check the contained variants.
+                        for variant in def.variants() {
+                            let is_non_exhaustive = variant.is_field_list_non_exhaustive();
+                            if is_non_exhaustive && !variant.def_id.is_local() {
+                                return FfiUnsafe {
+                                    ty,
+                                    reason: fluent::lint::improper_ctypes_non_exhaustive_variant,
+                                    help: None,
+                                };
+                            }
+
+                            match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
+                                FfiSafe => (),
+                                r => return r,
+                            }
+                        }
+
+                        FfiSafe
+                    }
+                }
+            }
+
+            ty::Char => FfiUnsafe {
+                ty,
+                reason: fluent::lint::improper_ctypes_char_reason,
+                help: Some(fluent::lint::improper_ctypes_char_help),
+            },
+
+            ty::Int(ty::IntTy::I128) | ty::Uint(ty::UintTy::U128) => {
+                FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_128bit, help: None }
+            }
+
+            // Primitive types with a stable representation.
+            ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
+
+            ty::Slice(_) => FfiUnsafe {
+                ty,
+                reason: fluent::lint::improper_ctypes_slice_reason,
+                help: Some(fluent::lint::improper_ctypes_slice_help),
+            },
+
+            ty::Dynamic(..) => {
+                FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_dyn, help: None }
+            }
+
+            ty::Str => FfiUnsafe {
+                ty,
+                reason: fluent::lint::improper_ctypes_str_reason,
+                help: Some(fluent::lint::improper_ctypes_str_help),
+            },
+
+            ty::Tuple(..) => FfiUnsafe {
+                ty,
+                reason: fluent::lint::improper_ctypes_tuple_reason,
+                help: Some(fluent::lint::improper_ctypes_tuple_help),
+            },
+
+            ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _)
+                if {
+                    matches!(self.mode, CItemKind::Definition)
+                        && ty.is_sized(self.cx.tcx.at(DUMMY_SP), self.cx.param_env)
+                } =>
+            {
+                FfiSafe
+            }
+
+            ty::RawPtr(ty::TypeAndMut { ty, .. })
+                if match ty.kind() {
+                    ty::Tuple(tuple) => tuple.is_empty(),
+                    _ => false,
+                } =>
+            {
+                FfiSafe
+            }
+
+            ty::RawPtr(ty::TypeAndMut { ty, .. }) | ty::Ref(_, ty, _) => {
+                self.check_type_for_ffi(cache, ty)
+            }
+
+            ty::Array(inner_ty, _) => self.check_type_for_ffi(cache, inner_ty),
+
+            ty::FnPtr(sig) => {
+                if self.is_internal_abi(sig.abi()) {
+                    return FfiUnsafe {
+                        ty,
+                        reason: fluent::lint::improper_ctypes_fnptr_reason,
+                        help: Some(fluent::lint::improper_ctypes_fnptr_help),
+                    };
+                }
+
+                let sig = tcx.erase_late_bound_regions(sig);
+                if !sig.output().is_unit() {
+                    let r = self.check_type_for_ffi(cache, sig.output());
+                    match r {
+                        FfiSafe => {}
+                        _ => {
+                            return r;
+                        }
+                    }
+                }
+                for arg in sig.inputs() {
+                    let r = self.check_type_for_ffi(cache, *arg);
+                    match r {
+                        FfiSafe => {}
+                        _ => {
+                            return r;
+                        }
+                    }
+                }
+                FfiSafe
+            }
+
+            ty::Foreign(..) => FfiSafe,
+
+            // While opaque types are checked for earlier, if a projection in a struct field
+            // normalizes to an opaque type, then it will reach this branch.
+            ty::Opaque(..) => {
+                FfiUnsafe { ty, reason: fluent::lint::improper_ctypes_opaque, help: None }
+            }
+
+            // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
+            //  so they are currently ignored for the purposes of this lint.
+            ty::Param(..) | ty::Projection(..) if matches!(self.mode, CItemKind::Definition) => {
+                FfiSafe
+            }
+
+            ty::Param(..)
+            | ty::Projection(..)
+            | ty::Infer(..)
+            | ty::Bound(..)
+            | ty::Error(_)
+            | ty::Closure(..)
+            | ty::Generator(..)
+            | ty::GeneratorWitness(..)
+            | ty::Placeholder(..)
+            | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
+        }
+    }
+
+    fn emit_ffi_unsafe_type_lint(
+        &mut self,
+        ty: Ty<'tcx>,
+        sp: Span,
+        note: DiagnosticMessage,
+        help: Option<DiagnosticMessage>,
+    ) {
+        let lint = match self.mode {
+            CItemKind::Declaration => IMPROPER_CTYPES,
+            CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
+        };
+
+        self.cx.struct_span_lint(lint, sp, |lint| {
+            let item_description = match self.mode {
+                CItemKind::Declaration => "block",
+                CItemKind::Definition => "fn",
+            };
+            let mut diag = lint.build(fluent::lint::improper_ctypes);
+            diag.set_arg("ty", ty);
+            diag.set_arg("desc", item_description);
+            diag.span_label(sp, fluent::lint::label);
+            if let Some(help) = help {
+                diag.help(help);
+            }
+            diag.note(note);
+            if let ty::Adt(def, _) = ty.kind() {
+                if let Some(sp) = self.cx.tcx.hir().span_if_local(def.did()) {
+                    diag.span_note(sp, fluent::lint::note);
+                }
+            }
+            diag.emit();
+        });
+    }
+
+    fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
+        struct ProhibitOpaqueTypes<'a, 'tcx> {
+            cx: &'a LateContext<'tcx>,
+        }
+
+        impl<'a, 'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueTypes<'a, 'tcx> {
+            type BreakTy = Ty<'tcx>;
+
+            fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
+                match ty.kind() {
+                    ty::Opaque(..) => ControlFlow::Break(ty),
+                    // Consider opaque types within projections FFI-safe if they do not normalize
+                    // to more opaque types.
+                    ty::Projection(..) => {
+                        let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
+
+                        // If `ty` is an opaque type directly then `super_visit_with` won't invoke
+                        // this function again.
+                        if ty.has_opaque_types() {
+                            self.visit_ty(ty)
+                        } else {
+                            ControlFlow::CONTINUE
+                        }
+                    }
+                    _ => ty.super_visit_with(self),
+                }
+            }
+        }
+
+        if let Some(ty) = ty.visit_with(&mut ProhibitOpaqueTypes { cx: self.cx }).break_value() {
+            self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint::improper_ctypes_opaque, None);
+            true
+        } else {
+            false
+        }
+    }
+
+    fn check_type_for_ffi_and_report_errors(
+        &mut self,
+        sp: Span,
+        ty: Ty<'tcx>,
+        is_static: bool,
+        is_return_type: bool,
+    ) {
+        // We have to check for opaque types before `normalize_erasing_regions`,
+        // which will replace opaque types with their underlying concrete type.
+        if self.check_for_opaque_ty(sp, ty) {
+            // We've already emitted an error due to an opaque type.
+            return;
+        }
+
+        // it is only OK to use this function because extern fns cannot have
+        // any generic types right now:
+        let ty = self.cx.tcx.normalize_erasing_regions(self.cx.param_env, ty);
+
+        // C doesn't really support passing arrays by value - the only way to pass an array by value
+        // is through a struct. So, first test that the top level isn't an array, and then
+        // recursively check the types inside.
+        if !is_static && self.check_for_array_ty(sp, ty) {
+            return;
+        }
+
+        // Don't report FFI errors for unit return types. This check exists here, and not in
+        // `check_foreign_fn` (where it would make more sense) so that normalization has definitely
+        // happened.
+        if is_return_type && ty.is_unit() {
+            return;
+        }
+
+        match self.check_type_for_ffi(&mut FxHashSet::default(), ty) {
+            FfiResult::FfiSafe => {}
+            FfiResult::FfiPhantom(ty) => {
+                self.emit_ffi_unsafe_type_lint(
+                    ty,
+                    sp,
+                    fluent::lint::improper_ctypes_only_phantomdata,
+                    None,
+                );
+            }
+            // If `ty` is a `repr(transparent)` newtype, and the non-zero-sized type is a generic
+            // argument, which after substitution, is `()`, then this branch can be hit.
+            FfiResult::FfiUnsafe { ty, .. } if is_return_type && ty.is_unit() => {}
+            FfiResult::FfiUnsafe { ty, reason, help } => {
+                self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
+            }
+        }
+    }
+
+    fn check_foreign_fn(&mut self, id: hir::HirId, decl: &hir::FnDecl<'_>) {
+        let def_id = self.cx.tcx.hir().local_def_id(id);
+        let sig = self.cx.tcx.fn_sig(def_id);
+        let sig = self.cx.tcx.erase_late_bound_regions(sig);
+
+        for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
+            self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
+        }
+
+        if let hir::FnRetTy::Return(ref ret_hir) = decl.output {
+            let ret_ty = sig.output();
+            self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty, false, true);
+        }
+    }
+
+    fn check_foreign_static(&mut self, id: hir::HirId, span: Span) {
+        let def_id = self.cx.tcx.hir().local_def_id(id);
+        let ty = self.cx.tcx.type_of(def_id);
+        self.check_type_for_ffi_and_report_errors(span, ty, true, false);
+    }
+
+    fn is_internal_abi(&self, abi: SpecAbi) -> bool {
+        matches!(
+            abi,
+            SpecAbi::Rust | SpecAbi::RustCall | SpecAbi::RustIntrinsic | SpecAbi::PlatformIntrinsic
+        )
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
+    fn check_foreign_item(&mut self, cx: &LateContext<'_>, it: &hir::ForeignItem<'_>) {
+        let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
+        let abi = cx.tcx.hir().get_foreign_abi(it.hir_id());
+
+        if !vis.is_internal_abi(abi) {
+            match it.kind {
+                hir::ForeignItemKind::Fn(ref decl, _, _) => {
+                    vis.check_foreign_fn(it.hir_id(), decl);
+                }
+                hir::ForeignItemKind::Static(ref ty, _) => {
+                    vis.check_foreign_static(it.hir_id(), ty.span);
+                }
+                hir::ForeignItemKind::Type => (),
+            }
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
+    fn check_fn(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        kind: hir::intravisit::FnKind<'tcx>,
+        decl: &'tcx hir::FnDecl<'_>,
+        _: &'tcx hir::Body<'_>,
+        _: Span,
+        hir_id: hir::HirId,
+    ) {
+        use hir::intravisit::FnKind;
+
+        let abi = match kind {
+            FnKind::ItemFn(_, _, header, ..) => header.abi,
+            FnKind::Method(_, sig, ..) => sig.header.abi,
+            _ => return,
+        };
+
+        let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
+        if !vis.is_internal_abi(abi) {
+            vis.check_foreign_fn(hir_id, decl);
+        }
+    }
+}
+
+declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
+
+impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
+    fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
+        if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
+            let t = cx.tcx.type_of(it.def_id);
+            let ty = cx.tcx.erase_regions(t);
+            let Ok(layout) = cx.layout_of(ty) else { return };
+            let Variants::Multiple {
+                    tag_encoding: TagEncoding::Direct, tag, ref variants, ..
+                } = &layout.variants else {
+                return
+            };
+
+            let tag_size = tag.size(&cx.tcx).bytes();
+
+            debug!(
+                "enum `{}` is {} bytes large with layout:\n{:#?}",
+                t,
+                layout.size.bytes(),
+                layout
+            );
+
+            let (largest, slargest, largest_index) = iter::zip(enum_definition.variants, variants)
+                .map(|(variant, variant_layout)| {
+                    // Subtract the size of the enum tag.
+                    let bytes = variant_layout.size().bytes().saturating_sub(tag_size);
+
+                    debug!("- variant `{}` is {} bytes large", variant.ident, bytes);
+                    bytes
+                })
+                .enumerate()
+                .fold((0, 0, 0), |(l, s, li), (idx, size)| {
+                    if size > l {
+                        (size, l, idx)
+                    } else if size > s {
+                        (l, size, li)
+                    } else {
+                        (l, s, li)
+                    }
+                });
+
+            // We only warn if the largest variant is at least thrice as large as
+            // the second-largest.
+            if largest > slargest * 3 && slargest > 0 {
+                cx.struct_span_lint(
+                    VARIANT_SIZE_DIFFERENCES,
+                    enum_definition.variants[largest_index].span,
+                    |lint| {
+                        lint.build(fluent::lint::variant_size_differences)
+                            .set_arg("largest", largest)
+                            .emit();
+                    },
+                );
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `invalid_atomic_ordering` lint detects passing an `Ordering`
+    /// to an atomic operation that does not support that ordering.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// # use core::sync::atomic::{AtomicU8, Ordering};
+    /// let atom = AtomicU8::new(0);
+    /// let value = atom.load(Ordering::Release);
+    /// # let _ = value;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Some atomic operations are only supported for a subset of the
+    /// `atomic::Ordering` variants. Passing an unsupported variant will cause
+    /// an unconditional panic at runtime, which is detected by this lint.
+    ///
+    /// This lint will trigger in the following cases: (where `AtomicType` is an
+    /// atomic type from `core::sync::atomic`, such as `AtomicBool`,
+    /// `AtomicPtr`, `AtomicUsize`, or any of the other integer atomics).
+    ///
+    /// - Passing `Ordering::Acquire` or `Ordering::AcqRel` to
+    ///   `AtomicType::store`.
+    ///
+    /// - Passing `Ordering::Release` or `Ordering::AcqRel` to
+    ///   `AtomicType::load`.
+    ///
+    /// - Passing `Ordering::Relaxed` to `core::sync::atomic::fence` or
+    ///   `core::sync::atomic::compiler_fence`.
+    ///
+    /// - Passing `Ordering::Release` or `Ordering::AcqRel` as the failure
+    ///   ordering for any of `AtomicType::compare_exchange`,
+    ///   `AtomicType::compare_exchange_weak`, or `AtomicType::fetch_update`.
+    INVALID_ATOMIC_ORDERING,
+    Deny,
+    "usage of invalid atomic ordering in atomic operations and memory fences"
+}
+
+declare_lint_pass!(InvalidAtomicOrdering => [INVALID_ATOMIC_ORDERING]);
+
+impl InvalidAtomicOrdering {
+    fn inherent_atomic_method_call<'hir>(
+        cx: &LateContext<'_>,
+        expr: &Expr<'hir>,
+        recognized_names: &[Symbol], // used for fast path calculation
+    ) -> Option<(Symbol, &'hir [Expr<'hir>])> {
+        const ATOMIC_TYPES: &[Symbol] = &[
+            sym::AtomicBool,
+            sym::AtomicPtr,
+            sym::AtomicUsize,
+            sym::AtomicU8,
+            sym::AtomicU16,
+            sym::AtomicU32,
+            sym::AtomicU64,
+            sym::AtomicU128,
+            sym::AtomicIsize,
+            sym::AtomicI8,
+            sym::AtomicI16,
+            sym::AtomicI32,
+            sym::AtomicI64,
+            sym::AtomicI128,
+        ];
+        if let ExprKind::MethodCall(ref method_path, args, _) = &expr.kind
+            && recognized_names.contains(&method_path.ident.name)
+            && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
+            && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
+            && let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def()
+            // skip extension traits, only lint functions from the standard library
+            && cx.tcx.trait_id_of_impl(impl_did).is_none()
+            && let parent = cx.tcx.parent(adt.did())
+            && cx.tcx.is_diagnostic_item(sym::atomic_mod, parent)
+            && ATOMIC_TYPES.contains(&cx.tcx.item_name(adt.did()))
+        {
+            return Some((method_path.ident.name, args));
+        }
+        None
+    }
+
+    fn match_ordering(cx: &LateContext<'_>, ord_arg: &Expr<'_>) -> Option<Symbol> {
+        let ExprKind::Path(ref ord_qpath) = ord_arg.kind else { return None };
+        let did = cx.qpath_res(ord_qpath, ord_arg.hir_id).opt_def_id()?;
+        let tcx = cx.tcx;
+        let atomic_ordering = tcx.get_diagnostic_item(sym::Ordering);
+        let name = tcx.item_name(did);
+        let parent = tcx.parent(did);
+        [sym::Relaxed, sym::Release, sym::Acquire, sym::AcqRel, sym::SeqCst].into_iter().find(
+            |&ordering| {
+                name == ordering
+                    && (Some(parent) == atomic_ordering
+                            // needed in case this is a ctor, not a variant
+                            || tcx.opt_parent(parent) == atomic_ordering)
+            },
+        )
+    }
+
+    fn check_atomic_load_store(cx: &LateContext<'_>, expr: &Expr<'_>) {
+        if let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::load, sym::store])
+            && let Some((ordering_arg, invalid_ordering)) = match method {
+                sym::load => Some((&args[1], sym::Release)),
+                sym::store => Some((&args[2], sym::Acquire)),
+                _ => None,
+            }
+            && let Some(ordering) = Self::match_ordering(cx, ordering_arg)
+            && (ordering == invalid_ordering || ordering == sym::AcqRel)
+        {
+            cx.struct_span_lint(INVALID_ATOMIC_ORDERING, ordering_arg.span, |diag| {
+                if method == sym::load {
+                    diag.build(fluent::lint::atomic_ordering_load)
+                        .help(fluent::lint::help)
+                        .emit()
+                } else {
+                    debug_assert_eq!(method, sym::store);
+                    diag.build(fluent::lint::atomic_ordering_store)
+                        .help(fluent::lint::help)
+                        .emit();
+                }
+            });
+        }
+    }
+
+    fn check_memory_fence(cx: &LateContext<'_>, expr: &Expr<'_>) {
+        if let ExprKind::Call(ref func, ref args) = expr.kind
+            && let ExprKind::Path(ref func_qpath) = func.kind
+            && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
+            && matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::fence | sym::compiler_fence))
+            && Self::match_ordering(cx, &args[0]) == Some(sym::Relaxed)
+        {
+            cx.struct_span_lint(INVALID_ATOMIC_ORDERING, args[0].span, |diag| {
+                diag.build(fluent::lint::atomic_ordering_fence)
+                    .help(fluent::lint::help)
+                    .emit();
+            });
+        }
+    }
+
+    fn check_atomic_compare_exchange(cx: &LateContext<'_>, expr: &Expr<'_>) {
+        let Some((method, args)) = Self::inherent_atomic_method_call(cx, expr, &[sym::fetch_update, sym::compare_exchange, sym::compare_exchange_weak])
+            else {return };
+
+        let fail_order_arg = match method {
+            sym::fetch_update => &args[2],
+            sym::compare_exchange | sym::compare_exchange_weak => &args[4],
+            _ => return,
+        };
+
+        let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return };
+
+        if matches!(fail_ordering, sym::Release | sym::AcqRel) {
+            #[derive(LintDiagnostic)]
+            #[lint(lint::atomic_ordering_invalid)]
+            #[help]
+            struct InvalidAtomicOrderingDiag {
+                method: Symbol,
+                #[label]
+                fail_order_arg_span: Span,
+            }
+
+            cx.emit_spanned_lint(
+                INVALID_ATOMIC_ORDERING,
+                fail_order_arg.span,
+                InvalidAtomicOrderingDiag { method, fail_order_arg_span: fail_order_arg.span },
+            );
+        }
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for InvalidAtomicOrdering {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        Self::check_atomic_load_store(cx, expr);
+        Self::check_memory_fence(cx, expr);
+        Self::check_atomic_compare_exchange(cx, expr);
+    }
+}
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
new file mode 100644
index 000000000..b6cf18291
--- /dev/null
+++ b/compiler/rustc_lint/src/unused.rs
@@ -0,0 +1,1197 @@
+use crate::Lint;
+use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
+use rustc_ast as ast;
+use rustc_ast::util::{classify, parser};
+use rustc_ast::{ExprKind, StmtKind};
+use rustc_errors::{fluent, pluralize, Applicability, MultiSpan};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::adjustment;
+use rustc_middle::ty::{self, Ty};
+use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{kw, sym};
+use rustc_span::{BytePos, Span, DUMMY_SP};
+
+declare_lint! {
+    /// The `unused_must_use` lint detects unused result of a type flagged as
+    /// `#[must_use]`.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// fn returns_result() -> Result<(), ()> {
+    ///     Ok(())
+    /// }
+    ///
+    /// fn main() {
+    ///     returns_result();
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The `#[must_use]` attribute is an indicator that it is a mistake to
+    /// ignore the value. See [the reference] for more details.
+    ///
+    /// [the reference]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
+    pub UNUSED_MUST_USE,
+    Warn,
+    "unused result of a type flagged as `#[must_use]`",
+    report_in_external_macro
+}
+
+declare_lint! {
+    /// The `unused_results` lint checks for the unused result of an
+    /// expression in a statement.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(unused_results)]
+    /// fn foo<T>() -> T { panic!() }
+    ///
+    /// fn main() {
+    ///     foo::<usize>();
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Ignoring the return value of a function may indicate a mistake. In
+    /// cases were it is almost certain that the result should be used, it is
+    /// recommended to annotate the function with the [`must_use` attribute].
+    /// Failure to use such a return value will trigger the [`unused_must_use`
+    /// lint] which is warn-by-default. The `unused_results` lint is
+    /// essentially the same, but triggers for *all* return values.
+    ///
+    /// This lint is "allow" by default because it can be noisy, and may not be
+    /// an actual problem. For example, calling the `remove` method of a `Vec`
+    /// or `HashMap` returns the previous value, which you may not care about.
+    /// Using this lint would require explicitly ignoring or discarding such
+    /// values.
+    ///
+    /// [`must_use` attribute]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
+    /// [`unused_must_use` lint]: warn-by-default.html#unused-must-use
+    pub UNUSED_RESULTS,
+    Allow,
+    "unused result of an expression in a statement"
+}
+
+declare_lint_pass!(UnusedResults => [UNUSED_MUST_USE, UNUSED_RESULTS]);
+
+impl<'tcx> LateLintPass<'tcx> for UnusedResults {
+    fn check_stmt(&mut self, cx: &LateContext<'_>, s: &hir::Stmt<'_>) {
+        let expr = match s.kind {
+            hir::StmtKind::Semi(ref expr) => &**expr,
+            _ => return,
+        };
+
+        if let hir::ExprKind::Ret(..) = expr.kind {
+            return;
+        }
+
+        let ty = cx.typeck_results().expr_ty(&expr);
+        let type_permits_lack_of_use = check_must_use_ty(cx, ty, &expr, s.span, "", "", 1);
+
+        let mut fn_warned = false;
+        let mut op_warned = false;
+        let maybe_def_id = match expr.kind {
+            hir::ExprKind::Call(ref callee, _) => {
+                match callee.kind {
+                    hir::ExprKind::Path(ref qpath) => {
+                        match cx.qpath_res(qpath, callee.hir_id) {
+                            Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => Some(def_id),
+                            // `Res::Local` if it was a closure, for which we
+                            // do not currently support must-use linting
+                            _ => None,
+                        }
+                    }
+                    _ => None,
+                }
+            }
+            hir::ExprKind::MethodCall(..) => cx.typeck_results().type_dependent_def_id(expr.hir_id),
+            _ => None,
+        };
+        if let Some(def_id) = maybe_def_id {
+            fn_warned = check_must_use_def(cx, def_id, s.span, "return value of ", "");
+        } else if type_permits_lack_of_use {
+            // We don't warn about unused unit or uninhabited types.
+            // (See https://github.com/rust-lang/rust/issues/43806 for details.)
+            return;
+        }
+
+        let must_use_op = match expr.kind {
+            // Hardcoding operators here seemed more expedient than the
+            // refactoring that would be needed to look up the `#[must_use]`
+            // attribute which does exist on the comparison trait methods
+            hir::ExprKind::Binary(bin_op, ..) => match bin_op.node {
+                hir::BinOpKind::Eq
+                | hir::BinOpKind::Lt
+                | hir::BinOpKind::Le
+                | hir::BinOpKind::Ne
+                | hir::BinOpKind::Ge
+                | hir::BinOpKind::Gt => Some("comparison"),
+                hir::BinOpKind::Add
+                | hir::BinOpKind::Sub
+                | hir::BinOpKind::Div
+                | hir::BinOpKind::Mul
+                | hir::BinOpKind::Rem => Some("arithmetic operation"),
+                hir::BinOpKind::And | hir::BinOpKind::Or => Some("logical operation"),
+                hir::BinOpKind::BitXor
+                | hir::BinOpKind::BitAnd
+                | hir::BinOpKind::BitOr
+                | hir::BinOpKind::Shl
+                | hir::BinOpKind::Shr => Some("bitwise operation"),
+            },
+            hir::ExprKind::AddrOf(..) => Some("borrow"),
+            hir::ExprKind::Unary(..) => Some("unary operation"),
+            _ => None,
+        };
+
+        if let Some(must_use_op) = must_use_op {
+            cx.struct_span_lint(UNUSED_MUST_USE, expr.span, |lint| {
+                lint.build(fluent::lint::unused_op)
+                    .set_arg("op", must_use_op)
+                    .span_label(expr.span, fluent::lint::label)
+                    .span_suggestion_verbose(
+                        expr.span.shrink_to_lo(),
+                        fluent::lint::suggestion,
+                        "let _ = ",
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+            });
+            op_warned = true;
+        }
+
+        if !(type_permits_lack_of_use || fn_warned || op_warned) {
+            cx.struct_span_lint(UNUSED_RESULTS, s.span, |lint| {
+                lint.build(fluent::lint::unused_result).set_arg("ty", ty).emit();
+            });
+        }
+
+        // Returns whether an error has been emitted (and thus another does not need to be later).
+        fn check_must_use_ty<'tcx>(
+            cx: &LateContext<'tcx>,
+            ty: Ty<'tcx>,
+            expr: &hir::Expr<'_>,
+            span: Span,
+            descr_pre: &str,
+            descr_post: &str,
+            plural_len: usize,
+        ) -> bool {
+            if ty.is_unit()
+                || cx.tcx.is_ty_uninhabited_from(
+                    cx.tcx.parent_module(expr.hir_id).to_def_id(),
+                    ty,
+                    cx.param_env,
+                )
+            {
+                return true;
+            }
+
+            let plural_suffix = pluralize!(plural_len);
+
+            match *ty.kind() {
+                ty::Adt(..) if ty.is_box() => {
+                    let boxed_ty = ty.boxed_ty();
+                    let descr_pre = &format!("{}boxed ", descr_pre);
+                    check_must_use_ty(cx, boxed_ty, expr, span, descr_pre, descr_post, plural_len)
+                }
+                ty::Adt(def, _) => check_must_use_def(cx, def.did(), span, descr_pre, descr_post),
+                ty::Opaque(def, _) => {
+                    let mut has_emitted = false;
+                    for &(predicate, _) in cx.tcx.explicit_item_bounds(def) {
+                        // We only look at the `DefId`, so it is safe to skip the binder here.
+                        if let ty::PredicateKind::Trait(ref poly_trait_predicate) =
+                            predicate.kind().skip_binder()
+                        {
+                            let def_id = poly_trait_predicate.trait_ref.def_id;
+                            let descr_pre =
+                                &format!("{}implementer{} of ", descr_pre, plural_suffix,);
+                            if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
+                                has_emitted = true;
+                                break;
+                            }
+                        }
+                    }
+                    has_emitted
+                }
+                ty::Dynamic(binder, _) => {
+                    let mut has_emitted = false;
+                    for predicate in binder.iter() {
+                        if let ty::ExistentialPredicate::Trait(ref trait_ref) =
+                            predicate.skip_binder()
+                        {
+                            let def_id = trait_ref.def_id;
+                            let descr_post =
+                                &format!(" trait object{}{}", plural_suffix, descr_post,);
+                            if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
+                                has_emitted = true;
+                                break;
+                            }
+                        }
+                    }
+                    has_emitted
+                }
+                ty::Tuple(ref tys) => {
+                    let mut has_emitted = false;
+                    let comps = if let hir::ExprKind::Tup(comps) = expr.kind {
+                        debug_assert_eq!(comps.len(), tys.len());
+                        comps
+                    } else {
+                        &[]
+                    };
+                    for (i, ty) in tys.iter().enumerate() {
+                        let descr_post = &format!(" in tuple element {}", i);
+                        let e = comps.get(i).unwrap_or(expr);
+                        let span = e.span;
+                        if check_must_use_ty(cx, ty, e, span, descr_pre, descr_post, plural_len) {
+                            has_emitted = true;
+                        }
+                    }
+                    has_emitted
+                }
+                ty::Array(ty, len) => match len.try_eval_usize(cx.tcx, cx.param_env) {
+                    // If the array is empty we don't lint, to avoid false positives
+                    Some(0) | None => false,
+                    // If the array is definitely non-empty, we can do `#[must_use]` checking.
+                    Some(n) => {
+                        let descr_pre = &format!("{}array{} of ", descr_pre, plural_suffix,);
+                        check_must_use_ty(cx, ty, expr, span, descr_pre, descr_post, n as usize + 1)
+                    }
+                },
+                ty::Closure(..) => {
+                    cx.struct_span_lint(UNUSED_MUST_USE, span, |lint| {
+                        // FIXME(davidtwco): this isn't properly translatable becauses of the
+                        // pre/post strings
+                        lint.build(fluent::lint::unused_closure)
+                            .set_arg("count", plural_len)
+                            .set_arg("pre", descr_pre)
+                            .set_arg("post", descr_post)
+                            .note(fluent::lint::note)
+                            .emit();
+                    });
+                    true
+                }
+                ty::Generator(..) => {
+                    cx.struct_span_lint(UNUSED_MUST_USE, span, |lint| {
+                        // FIXME(davidtwco): this isn't properly translatable becauses of the
+                        // pre/post strings
+                        lint.build(fluent::lint::unused_generator)
+                            .set_arg("count", plural_len)
+                            .set_arg("pre", descr_pre)
+                            .set_arg("post", descr_post)
+                            .note(fluent::lint::note)
+                            .emit();
+                    });
+                    true
+                }
+                _ => false,
+            }
+        }
+
+        // Returns whether an error has been emitted (and thus another does not need to be later).
+        // FIXME: Args desc_{pre,post}_path could be made lazy by taking Fn() -> &str, but this
+        // would make calling it a big awkward. Could also take String (so args are moved), but
+        // this would still require a copy into the format string, which would only be executed
+        // when needed.
+        fn check_must_use_def(
+            cx: &LateContext<'_>,
+            def_id: DefId,
+            span: Span,
+            descr_pre_path: &str,
+            descr_post_path: &str,
+        ) -> bool {
+            if let Some(attr) = cx.tcx.get_attr(def_id, sym::must_use) {
+                cx.struct_span_lint(UNUSED_MUST_USE, span, |lint| {
+                    // FIXME(davidtwco): this isn't properly translatable becauses of the pre/post
+                    // strings
+                    let mut err = lint.build(fluent::lint::unused_def);
+                    err.set_arg("pre", descr_pre_path);
+                    err.set_arg("post", descr_post_path);
+                    err.set_arg("def", cx.tcx.def_path_str(def_id));
+                    // check for #[must_use = "..."]
+                    if let Some(note) = attr.value_str() {
+                        err.note(note.as_str());
+                    }
+                    err.emit();
+                });
+                true
+            } else {
+                false
+            }
+        }
+    }
+}
+
+declare_lint! {
+    /// The `path_statements` lint detects path statements with no effect.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// let x = 42;
+    ///
+    /// x;
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// It is usually a mistake to have a statement that has no effect.
+    pub PATH_STATEMENTS,
+    Warn,
+    "path statements with no effect"
+}
+
+declare_lint_pass!(PathStatements => [PATH_STATEMENTS]);
+
+impl<'tcx> LateLintPass<'tcx> for PathStatements {
+    fn check_stmt(&mut self, cx: &LateContext<'_>, s: &hir::Stmt<'_>) {
+        if let hir::StmtKind::Semi(expr) = s.kind {
+            if let hir::ExprKind::Path(_) = expr.kind {
+                cx.struct_span_lint(PATH_STATEMENTS, s.span, |lint| {
+                    let ty = cx.typeck_results().expr_ty(expr);
+                    if ty.needs_drop(cx.tcx, cx.param_env) {
+                        let mut lint = lint.build(fluent::lint::path_statement_drop);
+                        if let Ok(snippet) = cx.sess().source_map().span_to_snippet(expr.span) {
+                            lint.span_suggestion(
+                                s.span,
+                                fluent::lint::suggestion,
+                                format!("drop({});", snippet),
+                                Applicability::MachineApplicable,
+                            );
+                        } else {
+                            lint.span_help(s.span, fluent::lint::suggestion);
+                        }
+                        lint.emit();
+                    } else {
+                        lint.build(fluent::lint::path_statement_no_effect).emit();
+                    }
+                });
+            }
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum UnusedDelimsCtx {
+    FunctionArg,
+    MethodArg,
+    AssignedValue,
+    AssignedValueLetElse,
+    IfCond,
+    WhileCond,
+    ForIterExpr,
+    MatchScrutineeExpr,
+    ReturnValue,
+    BlockRetValue,
+    LetScrutineeExpr,
+    ArrayLenExpr,
+    AnonConst,
+    MatchArmExpr,
+}
+
+impl From<UnusedDelimsCtx> for &'static str {
+    fn from(ctx: UnusedDelimsCtx) -> &'static str {
+        match ctx {
+            UnusedDelimsCtx::FunctionArg => "function argument",
+            UnusedDelimsCtx::MethodArg => "method argument",
+            UnusedDelimsCtx::AssignedValue | UnusedDelimsCtx::AssignedValueLetElse => {
+                "assigned value"
+            }
+            UnusedDelimsCtx::IfCond => "`if` condition",
+            UnusedDelimsCtx::WhileCond => "`while` condition",
+            UnusedDelimsCtx::ForIterExpr => "`for` iterator expression",
+            UnusedDelimsCtx::MatchScrutineeExpr => "`match` scrutinee expression",
+            UnusedDelimsCtx::ReturnValue => "`return` value",
+            UnusedDelimsCtx::BlockRetValue => "block return value",
+            UnusedDelimsCtx::LetScrutineeExpr => "`let` scrutinee expression",
+            UnusedDelimsCtx::ArrayLenExpr | UnusedDelimsCtx::AnonConst => "const expression",
+            UnusedDelimsCtx::MatchArmExpr => "match arm expression",
+        }
+    }
+}
+
+/// Used by both `UnusedParens` and `UnusedBraces` to prevent code duplication.
+trait UnusedDelimLint {
+    const DELIM_STR: &'static str;
+
+    /// Due to `ref` pattern, there can be a difference between using
+    /// `{ expr }` and `expr` in pattern-matching contexts. This means
+    /// that we should only lint `unused_parens` and not `unused_braces`
+    /// in this case.
+    ///
+    /// ```rust
+    /// let mut a = 7;
+    /// let ref b = { a }; // We actually borrow a copy of `a` here.
+    /// a += 1; // By mutating `a` we invalidate any borrows of `a`.
+    /// assert_eq!(b + 1, a); // `b` does not borrow `a`, so we can still use it here.
+    /// ```
+    const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool;
+
+    // this cannot be a constant is it refers to a static.
+    fn lint(&self) -> &'static Lint;
+
+    fn check_unused_delims_expr(
+        &self,
+        cx: &EarlyContext<'_>,
+        value: &ast::Expr,
+        ctx: UnusedDelimsCtx,
+        followed_by_block: bool,
+        left_pos: Option<BytePos>,
+        right_pos: Option<BytePos>,
+    );
+
+    fn is_expr_delims_necessary(
+        inner: &ast::Expr,
+        followed_by_block: bool,
+        followed_by_else: bool,
+    ) -> bool {
+        if followed_by_else {
+            match inner.kind {
+                ast::ExprKind::Binary(op, ..) if op.node.lazy() => return true,
+                _ if classify::expr_trailing_brace(inner).is_some() => return true,
+                _ => {}
+            }
+        }
+
+        // Prevent false-positives in cases like `fn x() -> u8 { ({ 0 } + 1) }`
+        let lhs_needs_parens = {
+            let mut innermost = inner;
+            loop {
+                innermost = match &innermost.kind {
+                    ExprKind::Binary(_, lhs, _rhs) => lhs,
+                    ExprKind::Call(fn_, _params) => fn_,
+                    ExprKind::Cast(expr, _ty) => expr,
+                    ExprKind::Type(expr, _ty) => expr,
+                    ExprKind::Index(base, _subscript) => base,
+                    _ => break false,
+                };
+                if !classify::expr_requires_semi_to_be_stmt(innermost) {
+                    break true;
+                }
+            }
+        };
+
+        lhs_needs_parens
+            || (followed_by_block
+                && match &inner.kind {
+                    ExprKind::Ret(_) | ExprKind::Break(..) | ExprKind::Yield(..) => true,
+                    ExprKind::Range(_lhs, Some(rhs), _limits) => {
+                        matches!(rhs.kind, ExprKind::Block(..))
+                    }
+                    _ => parser::contains_exterior_struct_lit(&inner),
+                })
+    }
+
+    fn emit_unused_delims_expr(
+        &self,
+        cx: &EarlyContext<'_>,
+        value: &ast::Expr,
+        ctx: UnusedDelimsCtx,
+        left_pos: Option<BytePos>,
+        right_pos: Option<BytePos>,
+    ) {
+        let spans = match value.kind {
+            ast::ExprKind::Block(ref block, None) if block.stmts.len() > 0 => {
+                let start = block.stmts[0].span;
+                let end = block.stmts[block.stmts.len() - 1].span;
+                if value.span.from_expansion() || start.from_expansion() || end.from_expansion() {
+                    (
+                        value.span.with_hi(value.span.lo() + BytePos(1)),
+                        value.span.with_lo(value.span.hi() - BytePos(1)),
+                    )
+                } else {
+                    (value.span.with_hi(start.lo()), value.span.with_lo(end.hi()))
+                }
+            }
+            ast::ExprKind::Paren(ref expr) => {
+                if value.span.from_expansion() || expr.span.from_expansion() {
+                    (
+                        value.span.with_hi(value.span.lo() + BytePos(1)),
+                        value.span.with_lo(value.span.hi() - BytePos(1)),
+                    )
+                } else {
+                    (value.span.with_hi(expr.span.lo()), value.span.with_lo(expr.span.hi()))
+                }
+            }
+            _ => return,
+        };
+        let keep_space = (
+            left_pos.map_or(false, |s| s >= value.span.lo()),
+            right_pos.map_or(false, |s| s <= value.span.hi()),
+        );
+        self.emit_unused_delims(cx, spans, ctx.into(), keep_space);
+    }
+
+    fn emit_unused_delims(
+        &self,
+        cx: &EarlyContext<'_>,
+        spans: (Span, Span),
+        msg: &str,
+        keep_space: (bool, bool),
+    ) {
+        // FIXME(flip1995): Quick and dirty fix for #70814. This should be fixed in rustdoc
+        // properly.
+        if spans.0 == DUMMY_SP || spans.1 == DUMMY_SP {
+            return;
+        }
+
+        cx.struct_span_lint(self.lint(), MultiSpan::from(vec![spans.0, spans.1]), |lint| {
+            let replacement = vec![
+                (spans.0, if keep_space.0 { " ".into() } else { "".into() }),
+                (spans.1, if keep_space.1 { " ".into() } else { "".into() }),
+            ];
+            lint.build(fluent::lint::unused_delim)
+                .set_arg("delim", Self::DELIM_STR)
+                .set_arg("item", msg)
+                .multipart_suggestion(
+                    fluent::lint::suggestion,
+                    replacement,
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        });
+    }
+
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+        use rustc_ast::ExprKind::*;
+        let (value, ctx, followed_by_block, left_pos, right_pos) = match e.kind {
+            // Do not lint `unused_braces` in `if let` expressions.
+            If(ref cond, ref block, _)
+                if !matches!(cond.kind, Let(_, _, _))
+                    || Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX =>
+            {
+                let left = e.span.lo() + rustc_span::BytePos(2);
+                let right = block.span.lo();
+                (cond, UnusedDelimsCtx::IfCond, true, Some(left), Some(right))
+            }
+
+            // Do not lint `unused_braces` in `while let` expressions.
+            While(ref cond, ref block, ..)
+                if !matches!(cond.kind, Let(_, _, _))
+                    || Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX =>
+            {
+                let left = e.span.lo() + rustc_span::BytePos(5);
+                let right = block.span.lo();
+                (cond, UnusedDelimsCtx::WhileCond, true, Some(left), Some(right))
+            }
+
+            ForLoop(_, ref cond, ref block, ..) => {
+                (cond, UnusedDelimsCtx::ForIterExpr, true, None, Some(block.span.lo()))
+            }
+
+            Match(ref head, _) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
+                let left = e.span.lo() + rustc_span::BytePos(5);
+                (head, UnusedDelimsCtx::MatchScrutineeExpr, true, Some(left), None)
+            }
+
+            Ret(Some(ref value)) => {
+                let left = e.span.lo() + rustc_span::BytePos(3);
+                (value, UnusedDelimsCtx::ReturnValue, false, Some(left), None)
+            }
+
+            Assign(_, ref value, _) | AssignOp(.., ref value) => {
+                (value, UnusedDelimsCtx::AssignedValue, false, None, None)
+            }
+            // either function/method call, or something this lint doesn't care about
+            ref call_or_other => {
+                let (args_to_check, ctx) = match *call_or_other {
+                    Call(_, ref args) => (&args[..], UnusedDelimsCtx::FunctionArg),
+                    // first "argument" is self (which sometimes needs delims)
+                    MethodCall(_, ref args, _) => (&args[1..], UnusedDelimsCtx::MethodArg),
+                    // actual catch-all arm
+                    _ => {
+                        return;
+                    }
+                };
+                // Don't lint if this is a nested macro expansion: otherwise, the lint could
+                // trigger in situations that macro authors shouldn't have to care about, e.g.,
+                // when a parenthesized token tree matched in one macro expansion is matched as
+                // an expression in another and used as a fn/method argument (Issue #47775)
+                if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
+                    return;
+                }
+                for arg in args_to_check {
+                    self.check_unused_delims_expr(cx, arg, ctx, false, None, None);
+                }
+                return;
+            }
+        };
+        self.check_unused_delims_expr(cx, &value, ctx, followed_by_block, left_pos, right_pos);
+    }
+
+    fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+        match s.kind {
+            StmtKind::Local(ref local) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
+                if let Some((init, els)) = local.kind.init_else_opt() {
+                    let ctx = match els {
+                        None => UnusedDelimsCtx::AssignedValue,
+                        Some(_) => UnusedDelimsCtx::AssignedValueLetElse,
+                    };
+                    self.check_unused_delims_expr(cx, init, ctx, false, None, None);
+                }
+            }
+            StmtKind::Expr(ref expr) => {
+                self.check_unused_delims_expr(
+                    cx,
+                    &expr,
+                    UnusedDelimsCtx::BlockRetValue,
+                    false,
+                    None,
+                    None,
+                );
+            }
+            _ => {}
+        }
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        use ast::ItemKind::*;
+
+        if let Const(.., Some(expr)) | Static(.., Some(expr)) = &item.kind {
+            self.check_unused_delims_expr(
+                cx,
+                expr,
+                UnusedDelimsCtx::AssignedValue,
+                false,
+                None,
+                None,
+            );
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unused_parens` lint detects `if`, `match`, `while` and `return`
+    /// with parentheses; they do not need them.
+    ///
+    /// ### Examples
+    ///
+    /// ```rust
+    /// if(true) {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The parentheses are not needed, and should be removed. This is the
+    /// preferred style for writing these expressions.
+    pub(super) UNUSED_PARENS,
+    Warn,
+    "`if`, `match`, `while` and `return` do not need parentheses"
+}
+
+declare_lint_pass!(UnusedParens => [UNUSED_PARENS]);
+
+impl UnusedDelimLint for UnusedParens {
+    const DELIM_STR: &'static str = "parentheses";
+
+    const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool = true;
+
+    fn lint(&self) -> &'static Lint {
+        UNUSED_PARENS
+    }
+
+    fn check_unused_delims_expr(
+        &self,
+        cx: &EarlyContext<'_>,
+        value: &ast::Expr,
+        ctx: UnusedDelimsCtx,
+        followed_by_block: bool,
+        left_pos: Option<BytePos>,
+        right_pos: Option<BytePos>,
+    ) {
+        match value.kind {
+            ast::ExprKind::Paren(ref inner) => {
+                let followed_by_else = ctx == UnusedDelimsCtx::AssignedValueLetElse;
+                if !Self::is_expr_delims_necessary(inner, followed_by_block, followed_by_else)
+                    && value.attrs.is_empty()
+                    && !value.span.from_expansion()
+                    && (ctx != UnusedDelimsCtx::LetScrutineeExpr
+                        || !matches!(inner.kind, ast::ExprKind::Binary(
+                                rustc_span::source_map::Spanned { node, .. },
+                                _,
+                                _,
+                            ) if node.lazy()))
+                {
+                    self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
+                }
+            }
+            ast::ExprKind::Let(_, ref expr, _) => {
+                self.check_unused_delims_expr(
+                    cx,
+                    expr,
+                    UnusedDelimsCtx::LetScrutineeExpr,
+                    followed_by_block,
+                    None,
+                    None,
+                );
+            }
+            _ => {}
+        }
+    }
+}
+
+impl UnusedParens {
+    fn check_unused_parens_pat(
+        &self,
+        cx: &EarlyContext<'_>,
+        value: &ast::Pat,
+        avoid_or: bool,
+        avoid_mut: bool,
+    ) {
+        use ast::{BindingMode, Mutability, PatKind};
+
+        if let PatKind::Paren(inner) = &value.kind {
+            match inner.kind {
+                // The lint visitor will visit each subpattern of `p`. We do not want to lint
+                // any range pattern no matter where it occurs in the pattern. For something like
+                // `&(a..=b)`, there is a recursive `check_pat` on `a` and `b`, but we will assume
+                // that if there are unnecessary parens they serve a purpose of readability.
+                PatKind::Range(..) => return,
+                // Avoid `p0 | .. | pn` if we should.
+                PatKind::Or(..) if avoid_or => return,
+                // Avoid `mut x` and `mut x @ p` if we should:
+                PatKind::Ident(BindingMode::ByValue(Mutability::Mut), ..) if avoid_mut => return,
+                // Otherwise proceed with linting.
+                _ => {}
+            }
+            let spans = if value.span.from_expansion() || inner.span.from_expansion() {
+                (
+                    value.span.with_hi(value.span.lo() + BytePos(1)),
+                    value.span.with_lo(value.span.hi() - BytePos(1)),
+                )
+            } else {
+                (value.span.with_hi(inner.span.lo()), value.span.with_lo(inner.span.hi()))
+            };
+            self.emit_unused_delims(cx, spans, "pattern", (false, false));
+        }
+    }
+}
+
+impl EarlyLintPass for UnusedParens {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+        match e.kind {
+            ExprKind::Let(ref pat, _, _) | ExprKind::ForLoop(ref pat, ..) => {
+                self.check_unused_parens_pat(cx, pat, false, false);
+            }
+            // We ignore parens in cases like `if (((let Some(0) = Some(1))))` because we already
+            // handle a hard error for them during AST lowering in `lower_expr_mut`, but we still
+            // want to complain about things like `if let 42 = (42)`.
+            ExprKind::If(ref cond, ref block, ref else_)
+                if matches!(cond.peel_parens().kind, ExprKind::Let(..)) =>
+            {
+                self.check_unused_delims_expr(
+                    cx,
+                    cond.peel_parens(),
+                    UnusedDelimsCtx::LetScrutineeExpr,
+                    true,
+                    None,
+                    None,
+                );
+                for stmt in &block.stmts {
+                    <Self as UnusedDelimLint>::check_stmt(self, cx, stmt);
+                }
+                if let Some(e) = else_ {
+                    <Self as UnusedDelimLint>::check_expr(self, cx, e);
+                }
+                return;
+            }
+            ExprKind::Match(ref _expr, ref arm) => {
+                for a in arm {
+                    self.check_unused_delims_expr(
+                        cx,
+                        &a.body,
+                        UnusedDelimsCtx::MatchArmExpr,
+                        false,
+                        None,
+                        None,
+                    );
+                }
+            }
+            _ => {}
+        }
+
+        <Self as UnusedDelimLint>::check_expr(self, cx, e)
+    }
+
+    fn check_pat(&mut self, cx: &EarlyContext<'_>, p: &ast::Pat) {
+        use ast::{Mutability, PatKind::*};
+        match &p.kind {
+            // Do not lint on `(..)` as that will result in the other arms being useless.
+            Paren(_)
+            // The other cases do not contain sub-patterns.
+            | Wild | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
+            // These are list-like patterns; parens can always be removed.
+            TupleStruct(_, _, ps) | Tuple(ps) | Slice(ps) | Or(ps) => for p in ps {
+                self.check_unused_parens_pat(cx, p, false, false);
+            },
+            Struct(_, _, fps, _) => for f in fps {
+                self.check_unused_parens_pat(cx, &f.pat, false, false);
+            },
+            // Avoid linting on `i @ (p0 | .. | pn)` and `box (p0 | .. | pn)`, #64106.
+            Ident(.., Some(p)) | Box(p) => self.check_unused_parens_pat(cx, p, true, false),
+            // Avoid linting on `&(mut x)` as `&mut x` has a different meaning, #55342.
+            // Also avoid linting on `& mut? (p0 | .. | pn)`, #64106.
+            Ref(p, m) => self.check_unused_parens_pat(cx, p, true, *m == Mutability::Not),
+        }
+    }
+
+    fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+        if let StmtKind::Local(ref local) = s.kind {
+            self.check_unused_parens_pat(cx, &local.pat, true, false);
+        }
+
+        <Self as UnusedDelimLint>::check_stmt(self, cx, s)
+    }
+
+    fn check_param(&mut self, cx: &EarlyContext<'_>, param: &ast::Param) {
+        self.check_unused_parens_pat(cx, &param.pat, true, false);
+    }
+
+    fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
+        self.check_unused_parens_pat(cx, &arm.pat, false, false);
+    }
+
+    fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
+        if let ast::TyKind::Paren(r) = &ty.kind {
+            match &r.kind {
+                ast::TyKind::TraitObject(..) => {}
+                ast::TyKind::ImplTrait(_, bounds) if bounds.len() > 1 => {}
+                ast::TyKind::Array(_, len) => {
+                    self.check_unused_delims_expr(
+                        cx,
+                        &len.value,
+                        UnusedDelimsCtx::ArrayLenExpr,
+                        false,
+                        None,
+                        None,
+                    );
+                }
+                _ => {
+                    let spans = if ty.span.from_expansion() || r.span.from_expansion() {
+                        (
+                            ty.span.with_hi(ty.span.lo() + BytePos(1)),
+                            ty.span.with_lo(ty.span.hi() - BytePos(1)),
+                        )
+                    } else {
+                        (ty.span.with_hi(r.span.lo()), ty.span.with_lo(r.span.hi()))
+                    };
+                    self.emit_unused_delims(cx, spans, "type", (false, false));
+                }
+            }
+        }
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        <Self as UnusedDelimLint>::check_item(self, cx, item)
+    }
+}
+
+declare_lint! {
+    /// The `unused_braces` lint detects unnecessary braces around an
+    /// expression.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// if { true } {
+    ///     // ...
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The braces are not needed, and should be removed. This is the
+    /// preferred style for writing these expressions.
+    pub(super) UNUSED_BRACES,
+    Warn,
+    "unnecessary braces around an expression"
+}
+
+declare_lint_pass!(UnusedBraces => [UNUSED_BRACES]);
+
+impl UnusedDelimLint for UnusedBraces {
+    const DELIM_STR: &'static str = "braces";
+
+    const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool = false;
+
+    fn lint(&self) -> &'static Lint {
+        UNUSED_BRACES
+    }
+
+    fn check_unused_delims_expr(
+        &self,
+        cx: &EarlyContext<'_>,
+        value: &ast::Expr,
+        ctx: UnusedDelimsCtx,
+        followed_by_block: bool,
+        left_pos: Option<BytePos>,
+        right_pos: Option<BytePos>,
+    ) {
+        match value.kind {
+            ast::ExprKind::Block(ref inner, None)
+                if inner.rules == ast::BlockCheckMode::Default =>
+            {
+                // emit a warning under the following conditions:
+                //
+                // - the block does not have a label
+                // - the block is not `unsafe`
+                // - the block contains exactly one expression (do not lint `{ expr; }`)
+                // - `followed_by_block` is true and the internal expr may contain a `{`
+                // - the block is not multiline (do not lint multiline match arms)
+                //      ```
+                //      match expr {
+                //          Pattern => {
+                //              somewhat_long_expression
+                //          }
+                //          // ...
+                //      }
+                //      ```
+                // - the block has no attribute and was not created inside a macro
+                // - if the block is an `anon_const`, the inner expr must be a literal
+                //      (do not lint `struct A<const N: usize>; let _: A<{ 2 + 3 }>;`)
+                //
+                // FIXME(const_generics): handle paths when #67075 is fixed.
+                if let [stmt] = inner.stmts.as_slice() {
+                    if let ast::StmtKind::Expr(ref expr) = stmt.kind {
+                        if !Self::is_expr_delims_necessary(expr, followed_by_block, false)
+                            && (ctx != UnusedDelimsCtx::AnonConst
+                                || matches!(expr.kind, ast::ExprKind::Lit(_)))
+                            && !cx.sess().source_map().is_multiline(value.span)
+                            && value.attrs.is_empty()
+                            && !value.span.from_expansion()
+                        {
+                            self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
+                        }
+                    }
+                }
+            }
+            ast::ExprKind::Let(_, ref expr, _) => {
+                self.check_unused_delims_expr(
+                    cx,
+                    expr,
+                    UnusedDelimsCtx::LetScrutineeExpr,
+                    followed_by_block,
+                    None,
+                    None,
+                );
+            }
+            _ => {}
+        }
+    }
+}
+
+impl EarlyLintPass for UnusedBraces {
+    fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+        <Self as UnusedDelimLint>::check_stmt(self, cx, s)
+    }
+
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+        <Self as UnusedDelimLint>::check_expr(self, cx, e);
+
+        if let ExprKind::Repeat(_, ref anon_const) = e.kind {
+            self.check_unused_delims_expr(
+                cx,
+                &anon_const.value,
+                UnusedDelimsCtx::AnonConst,
+                false,
+                None,
+                None,
+            );
+        }
+    }
+
+    fn check_generic_arg(&mut self, cx: &EarlyContext<'_>, arg: &ast::GenericArg) {
+        if let ast::GenericArg::Const(ct) = arg {
+            self.check_unused_delims_expr(
+                cx,
+                &ct.value,
+                UnusedDelimsCtx::AnonConst,
+                false,
+                None,
+                None,
+            );
+        }
+    }
+
+    fn check_variant(&mut self, cx: &EarlyContext<'_>, v: &ast::Variant) {
+        if let Some(anon_const) = &v.disr_expr {
+            self.check_unused_delims_expr(
+                cx,
+                &anon_const.value,
+                UnusedDelimsCtx::AnonConst,
+                false,
+                None,
+                None,
+            );
+        }
+    }
+
+    fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
+        match ty.kind {
+            ast::TyKind::Array(_, ref len) => {
+                self.check_unused_delims_expr(
+                    cx,
+                    &len.value,
+                    UnusedDelimsCtx::ArrayLenExpr,
+                    false,
+                    None,
+                    None,
+                );
+            }
+
+            ast::TyKind::Typeof(ref anon_const) => {
+                self.check_unused_delims_expr(
+                    cx,
+                    &anon_const.value,
+                    UnusedDelimsCtx::AnonConst,
+                    false,
+                    None,
+                    None,
+                );
+            }
+
+            _ => {}
+        }
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        <Self as UnusedDelimLint>::check_item(self, cx, item)
+    }
+}
+
+declare_lint! {
+    /// The `unused_import_braces` lint catches unnecessary braces around an
+    /// imported item.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(unused_import_braces)]
+    /// use test::{A};
+    ///
+    /// pub mod test {
+    ///     pub struct A;
+    /// }
+    /// # fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// If there is only a single item, then remove the braces (`use test::A;`
+    /// for example).
+    ///
+    /// This lint is "allow" by default because it is only enforcing a
+    /// stylistic choice.
+    UNUSED_IMPORT_BRACES,
+    Allow,
+    "unnecessary braces around an imported item"
+}
+
+declare_lint_pass!(UnusedImportBraces => [UNUSED_IMPORT_BRACES]);
+
+impl UnusedImportBraces {
+    fn check_use_tree(&self, cx: &EarlyContext<'_>, use_tree: &ast::UseTree, item: &ast::Item) {
+        if let ast::UseTreeKind::Nested(ref items) = use_tree.kind {
+            // Recursively check nested UseTrees
+            for &(ref tree, _) in items {
+                self.check_use_tree(cx, tree, item);
+            }
+
+            // Trigger the lint only if there is one nested item
+            if items.len() != 1 {
+                return;
+            }
+
+            // Trigger the lint if the nested item is a non-self single item
+            let node_name = match items[0].0.kind {
+                ast::UseTreeKind::Simple(rename, ..) => {
+                    let orig_ident = items[0].0.prefix.segments.last().unwrap().ident;
+                    if orig_ident.name == kw::SelfLower {
+                        return;
+                    }
+                    rename.unwrap_or(orig_ident).name
+                }
+                ast::UseTreeKind::Glob => Symbol::intern("*"),
+                ast::UseTreeKind::Nested(_) => return,
+            };
+
+            cx.struct_span_lint(UNUSED_IMPORT_BRACES, item.span, |lint| {
+                lint.build(fluent::lint::unused_import_braces).set_arg("node", node_name).emit();
+            });
+        }
+    }
+}
+
+impl EarlyLintPass for UnusedImportBraces {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        if let ast::ItemKind::Use(ref use_tree) = item.kind {
+            self.check_use_tree(cx, use_tree, item);
+        }
+    }
+}
+
+declare_lint! {
+    /// The `unused_allocation` lint detects unnecessary allocations that can
+    /// be eliminated.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// #![feature(box_syntax)]
+    /// fn main() {
+    ///     let a = (box [1, 2, 3]).len();
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// When a `box` expression is immediately coerced to a reference, then
+    /// the allocation is unnecessary, and a reference (using `&` or `&mut`)
+    /// should be used instead to avoid the allocation.
+    pub(super) UNUSED_ALLOCATION,
+    Warn,
+    "detects unnecessary allocations that can be eliminated"
+}
+
+declare_lint_pass!(UnusedAllocation => [UNUSED_ALLOCATION]);
+
+impl<'tcx> LateLintPass<'tcx> for UnusedAllocation {
+    fn check_expr(&mut self, cx: &LateContext<'_>, e: &hir::Expr<'_>) {
+        match e.kind {
+            hir::ExprKind::Box(_) => {}
+            _ => return,
+        }
+
+        for adj in cx.typeck_results().expr_adjustments(e) {
+            if let adjustment::Adjust::Borrow(adjustment::AutoBorrow::Ref(_, m)) = adj.kind {
+                cx.struct_span_lint(UNUSED_ALLOCATION, e.span, |lint| {
+                    lint.build(match m {
+                        adjustment::AutoBorrowMutability::Not => fluent::lint::unused_allocation,
+                        adjustment::AutoBorrowMutability::Mut { .. } => {
+                            fluent::lint::unused_allocation_mut
+                        }
+                    })
+                    .emit();
+                });
+            }
+        }
+    }
+}