Merging upstream version 1.66.0+dfsg1.

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

4 files changed, 136 insertions, 410 deletions

diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index b1d10e07a..036643244 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -14,6 +14,7 @@ use rustc_ast::*;
 use rustc_ast_pretty::pprust::{self, State};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{error_code, fluent, pluralize, struct_span_err, Applicability};
+use rustc_macros::Subdiagnostic;
 use rustc_parse::validate_attr;
 use rustc_session::lint::builtin::{
     DEPRECATED_WHERE_CLAUSE_LOCATION, MISSING_ABI, PATTERNS_IN_FNS_WITHOUT_BODY,
@@ -38,6 +39,13 @@ enum SelfSemantic {
     No,
 }
 
+/// What is the context that prevents using `~const`?
+enum DisallowTildeConstContext<'a> {
+    TraitObject,
+    ImplTrait,
+    Fn(FnKind<'a>),
+}
+
 struct AstValidator<'a> {
     session: &'a Session,
 
@@ -56,7 +64,7 @@ struct AstValidator<'a> {
     /// e.g., `impl Iterator<Item = impl Debug>`.
     outer_impl_trait: Option<Span>,
 
-    is_tilde_const_allowed: bool,
+    disallow_tilde_const: Option<DisallowTildeConstContext<'a>>,
 
     /// Used to ban `impl Trait` in path projections like `<impl Iterator>::Item`
     /// or `Foo::Bar<impl Trait>`
@@ -93,18 +101,26 @@ impl<'a> AstValidator<'a> {
         self.is_impl_trait_banned = old;
     }
 
-    fn with_tilde_const(&mut self, allowed: bool, f: impl FnOnce(&mut Self)) {
-        let old = mem::replace(&mut self.is_tilde_const_allowed, allowed);
+    fn with_tilde_const(
+        &mut self,
+        disallowed: Option<DisallowTildeConstContext<'a>>,
+        f: impl FnOnce(&mut Self),
+    ) {
+        let old = mem::replace(&mut self.disallow_tilde_const, disallowed);
         f(self);
-        self.is_tilde_const_allowed = old;
+        self.disallow_tilde_const = old;
     }
 
     fn with_tilde_const_allowed(&mut self, f: impl FnOnce(&mut Self)) {
-        self.with_tilde_const(true, f)
+        self.with_tilde_const(None, f)
     }
 
-    fn with_banned_tilde_const(&mut self, f: impl FnOnce(&mut Self)) {
-        self.with_tilde_const(false, f)
+    fn with_banned_tilde_const(
+        &mut self,
+        ctx: DisallowTildeConstContext<'a>,
+        f: impl FnOnce(&mut Self),
+    ) {
+        self.with_tilde_const(Some(ctx), f)
     }
 
     fn with_let_management(
@@ -154,7 +170,7 @@ impl<'a> AstValidator<'a> {
                 DEPRECATED_WHERE_CLAUSE_LOCATION,
                 id,
                 where_clauses.0.1,
-                fluent::ast_passes::deprecated_where_clause_location,
+                fluent::ast_passes_deprecated_where_clause_location,
                 BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(
                     where_clauses.1.1.shrink_to_hi(),
                     suggestion,
@@ -172,7 +188,7 @@ impl<'a> AstValidator<'a> {
     fn with_impl_trait(&mut self, outer: Option<Span>, f: impl FnOnce(&mut Self)) {
         let old = mem::replace(&mut self.outer_impl_trait, outer);
         if outer.is_some() {
-            self.with_banned_tilde_const(f);
+            self.with_banned_tilde_const(DisallowTildeConstContext::ImplTrait, f);
         } else {
             f(self);
         }
@@ -197,7 +213,10 @@ impl<'a> AstValidator<'a> {
             TyKind::ImplTrait(..) => {
                 self.with_impl_trait(Some(t.span), |this| visit::walk_ty(this, t))
             }
-            TyKind::TraitObject(..) => self.with_banned_tilde_const(|this| visit::walk_ty(this, t)),
+            TyKind::TraitObject(..) => self
+                .with_banned_tilde_const(DisallowTildeConstContext::TraitObject, |this| {
+                    visit::walk_ty(this, t)
+                }),
             TyKind::Path(ref qself, ref path) => {
                 // We allow these:
                 //  - `Option<impl Trait>`
@@ -233,20 +252,6 @@ impl<'a> AstValidator<'a> {
         }
     }
 
-    fn visit_struct_field_def(&mut self, field: &'a FieldDef) {
-        if let Some(ident) = field.ident {
-            if ident.name == kw::Underscore {
-                self.visit_vis(&field.vis);
-                self.visit_ident(ident);
-                self.visit_ty_common(&field.ty);
-                self.walk_ty(&field.ty);
-                walk_list!(self, visit_attribute, &field.attrs);
-                return;
-            }
-        }
-        self.visit_field_def(field);
-    }
-
     fn err_handler(&self) -> &rustc_errors::Handler {
         &self.session.diagnostic()
     }
@@ -987,8 +992,8 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         visit::walk_lifetime(self, lifetime);
     }
 
-    fn visit_field_def(&mut self, s: &'a FieldDef) {
-        visit::walk_field_def(self, s)
+    fn visit_field_def(&mut self, field: &'a FieldDef) {
+        visit::walk_field_def(self, field)
     }
 
     fn visit_item(&mut self, item: &'a Item) {
@@ -1176,42 +1181,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     self.check_mod_file_item_asciionly(item.ident);
                 }
             }
-            ItemKind::Struct(ref vdata, ref generics) => match vdata {
-                // Duplicating the `Visitor` logic allows catching all cases
-                // of `Anonymous(Struct, Union)` outside of a field struct or union.
-                //
-                // Inside `visit_ty` the validator catches every `Anonymous(Struct, Union)` it
-                // encounters, and only on `ItemKind::Struct` and `ItemKind::Union`
-                // it uses `visit_ty_common`, which doesn't contain that specific check.
-                VariantData::Struct(ref fields, ..) => {
-                    self.visit_vis(&item.vis);
-                    self.visit_ident(item.ident);
-                    self.visit_generics(generics);
-                    self.with_banned_assoc_ty_bound(|this| {
-                        walk_list!(this, visit_struct_field_def, fields);
-                    });
-                    walk_list!(self, visit_attribute, &item.attrs);
-                    return;
-                }
-                _ => {}
-            },
-            ItemKind::Union(ref vdata, ref generics) => {
+            ItemKind::Union(ref vdata, ..) => {
                 if vdata.fields().is_empty() {
                     self.err_handler().span_err(item.span, "unions cannot have zero fields");
                 }
-                match vdata {
-                    VariantData::Struct(ref fields, ..) => {
-                        self.visit_vis(&item.vis);
-                        self.visit_ident(item.ident);
-                        self.visit_generics(generics);
-                        self.with_banned_assoc_ty_bound(|this| {
-                            walk_list!(this, visit_struct_field_def, fields);
-                        });
-                        walk_list!(self, visit_attribute, &item.attrs);
-                        return;
-                    }
-                    _ => {}
-                }
             }
             ItemKind::Const(def, .., None) => {
                 self.check_defaultness(item.span, def);
@@ -1411,13 +1384,15 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                     );
                     err.emit();
                 }
-                (_, TraitBoundModifier::MaybeConst) => {
-                    if !self.is_tilde_const_allowed {
-                        self.err_handler()
-                            .struct_span_err(bound.span(), "`~const` is not allowed here")
-                            .note("only allowed on bounds on traits' associated types and functions, const fns, const impls and its associated functions")
-                            .emit();
-                    }
+                (_, TraitBoundModifier::MaybeConst) if let Some(reason) = &self.disallow_tilde_const => {
+                    let mut err = self.err_handler().struct_span_err(bound.span(), "`~const` is not allowed here");
+                    match reason {
+                        DisallowTildeConstContext::TraitObject => err.note("trait objects cannot have `~const` trait bounds"),
+                        DisallowTildeConstContext::ImplTrait => err.note("`impl Trait`s cannot have `~const` trait bounds"),
+                        DisallowTildeConstContext::Fn(FnKind::Closure(..)) => err.note("closures cannot have `~const` trait bounds"),
+                        DisallowTildeConstContext::Fn(FnKind::Fn(_, ident, ..)) => err.span_note(ident.span, "this function is not `const`, so it cannot have `~const` trait bounds"),
+                    };
+                    err.emit();
                 }
                 (_, TraitBoundModifier::MaybeConstMaybe) => {
                     self.err_handler()
@@ -1524,10 +1499,12 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         let tilde_const_allowed =
-            matches!(fk.header(), Some(FnHeader { constness: Const::Yes(_), .. }))
+            matches!(fk.header(), Some(FnHeader { constness: ast::Const::Yes(_), .. }))
                 || matches!(fk.ctxt(), Some(FnCtxt::Assoc(_)));
 
-        self.with_tilde_const(tilde_const_allowed, |this| visit::walk_fn(this, fk));
+        let disallowed = (!tilde_const_allowed).then(|| DisallowTildeConstContext::Fn(fk));
+
+        self.with_tilde_const(disallowed, |this| visit::walk_fn(this, fk));
     }
 
     fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
@@ -1557,7 +1534,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         });
                     }
                 }
-                AssocItemKind::TyAlias(box TyAlias {
+                AssocItemKind::Type(box TyAlias {
                     generics,
                     where_clauses,
                     where_predicates_split,
@@ -1596,7 +1573,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
         }
 
         match item.kind {
-            AssocItemKind::TyAlias(box TyAlias { ref generics, ref bounds, ref ty, .. })
+            AssocItemKind::Type(box TyAlias { ref generics, ref bounds, ref ty, .. })
                 if ctxt == AssocCtxt::Trait =>
             {
                 self.visit_vis(&item.vis);
@@ -1771,7 +1748,7 @@ pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) ->
         in_const_trait_impl: false,
         has_proc_macro_decls: false,
         outer_impl_trait: None,
-        is_tilde_const_allowed: false,
+        disallow_tilde_const: None,
         is_impl_trait_banned: false,
         is_assoc_ty_bound_banned: false,
         forbidden_let_reason: Some(ForbiddenLetReason::GenericForbidden),
@@ -1783,15 +1760,17 @@ pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) ->
 }
 
 /// Used to forbid `let` expressions in certain syntactic locations.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Subdiagnostic)]
 pub(crate) enum ForbiddenLetReason {
     /// `let` is not valid and the source environment is not important
     GenericForbidden,
     /// A let chain with the `||` operator
-    NotSupportedOr(Span),
+    #[note(not_supported_or)]
+    NotSupportedOr(#[primary_span] Span),
     /// A let chain with invalid parentheses
     ///
     /// For example, `let 1 = 1 && (expr && expr)` is allowed
     /// but `(let 1 = 1 && (let 1 = 1 && (let 1 = 1))) && let a = 1` is not
-    NotSupportedParentheses(Span),
+    #[note(not_supported_parentheses)]
+    NotSupportedParentheses(#[primary_span] Span),
 }
diff --git a/compiler/rustc_ast_passes/src/errors.rs b/compiler/rustc_ast_passes/src/errors.rs
index 4f3b09c58..59f582f10 100644
--- a/compiler/rustc_ast_passes/src/errors.rs
+++ b/compiler/rustc_ast_passes/src/errors.rs
@@ -1,13 +1,13 @@
 //! Errors emitted by ast_passes.
 
-use rustc_errors::{fluent, AddSubdiagnostic, Applicability, Diagnostic};
-use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
+use rustc_errors::{fluent, AddToDiagnostic, Applicability, Diagnostic, SubdiagnosticMessage};
+use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
 use crate::ast_validation::ForbiddenLetReason;
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_let)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_let)]
 #[note]
 pub struct ForbiddenLet {
     #[primary_span]
@@ -16,130 +16,116 @@ pub struct ForbiddenLet {
     pub(crate) reason: ForbiddenLetReason,
 }
 
-impl AddSubdiagnostic for ForbiddenLetReason {
-    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
-        match self {
-            Self::GenericForbidden => {}
-            Self::NotSupportedOr(span) => {
-                diag.span_note(span, fluent::ast_passes::not_supported_or);
-            }
-            Self::NotSupportedParentheses(span) => {
-                diag.span_note(span, fluent::ast_passes::not_supported_parentheses);
-            }
-        }
-    }
-}
-
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_let_stable)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_let_stable)]
 #[note]
 pub struct ForbiddenLetStable {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_assoc_constraint)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_assoc_constraint)]
 pub struct ForbiddenAssocConstraint {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::keyword_lifetime)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_keyword_lifetime)]
 pub struct KeywordLifetime {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::invalid_label)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_invalid_label)]
 pub struct InvalidLabel {
     #[primary_span]
     pub span: Span,
     pub name: Symbol,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::invalid_visibility, code = "E0449")]
+#[derive(Diagnostic)]
+#[diag(ast_passes_invalid_visibility, code = "E0449")]
 pub struct InvalidVisibility {
     #[primary_span]
     pub span: Span,
-    #[label(ast_passes::implied)]
+    #[label(implied)]
     pub implied: Option<Span>,
     #[subdiagnostic]
     pub note: Option<InvalidVisibilityNote>,
 }
 
-#[derive(SessionSubdiagnostic)]
+#[derive(Subdiagnostic)]
 pub enum InvalidVisibilityNote {
-    #[note(ast_passes::individual_impl_items)]
+    #[note(individual_impl_items)]
     IndividualImplItems,
-    #[note(ast_passes::individual_foreign_items)]
+    #[note(individual_foreign_items)]
     IndividualForeignItems,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::trait_fn_const, code = "E0379")]
+#[derive(Diagnostic)]
+#[diag(ast_passes_trait_fn_const, code = "E0379")]
 pub struct TraitFnConst {
     #[primary_span]
     #[label]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_lifetime_bound)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_lifetime_bound)]
 pub struct ForbiddenLifetimeBound {
     #[primary_span]
     pub spans: Vec<Span>,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_non_lifetime_param)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_non_lifetime_param)]
 pub struct ForbiddenNonLifetimeParam {
     #[primary_span]
     pub spans: Vec<Span>,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_too_many)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_too_many)]
 pub struct FnParamTooMany {
     #[primary_span]
     pub span: Span,
     pub max_num_args: usize,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_c_var_args_only)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_c_var_args_only)]
 pub struct FnParamCVarArgsOnly {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_c_var_args_not_last)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_c_var_args_not_last)]
 pub struct FnParamCVarArgsNotLast {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_doc_comment)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_doc_comment)]
 pub struct FnParamDocComment {
     #[primary_span]
     #[label]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_forbidden_attr)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_forbidden_attr)]
 pub struct FnParamForbiddenAttr {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_param_forbidden_self)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_param_forbidden_self)]
 #[note]
 pub struct FnParamForbiddenSelf {
     #[primary_span]
@@ -147,8 +133,8 @@ pub struct FnParamForbiddenSelf {
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::forbidden_default)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_forbidden_default)]
 pub struct ForbiddenDefault {
     #[primary_span]
     pub span: Span,
@@ -156,8 +142,8 @@ pub struct ForbiddenDefault {
     pub def_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::assoc_const_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_assoc_const_without_body)]
 pub struct AssocConstWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -165,8 +151,8 @@ pub struct AssocConstWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::assoc_fn_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_assoc_fn_without_body)]
 pub struct AssocFnWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -174,8 +160,8 @@ pub struct AssocFnWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::assoc_type_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_assoc_type_without_body)]
 pub struct AssocTypeWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -183,8 +169,8 @@ pub struct AssocTypeWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::const_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_const_without_body)]
 pub struct ConstWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -192,8 +178,8 @@ pub struct ConstWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::static_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_static_without_body)]
 pub struct StaticWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -201,8 +187,8 @@ pub struct StaticWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::ty_alias_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_ty_alias_without_body)]
 pub struct TyAliasWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -210,8 +196,8 @@ pub struct TyAliasWithoutBody {
     pub replace_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
-#[diag(ast_passes::fn_without_body)]
+#[derive(Diagnostic)]
+#[diag(ast_passes_fn_without_body)]
 pub struct FnWithoutBody {
     #[primary_span]
     pub span: Span,
@@ -227,8 +213,11 @@ pub struct ExternBlockSuggestion {
     pub abi: Option<Symbol>,
 }
 
-impl AddSubdiagnostic for ExternBlockSuggestion {
-    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+impl AddToDiagnostic for ExternBlockSuggestion {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
         let start_suggestion = if let Some(abi) = self.abi {
             format!("extern \"{}\" {{", abi)
         } else {
@@ -237,7 +226,7 @@ impl AddSubdiagnostic for ExternBlockSuggestion {
         let end_suggestion = " }".to_owned();
 
         diag.multipart_suggestion(
-            fluent::ast_passes::extern_block_suggestion,
+            fluent::extern_block_suggestion,
             vec![(self.start_span, start_suggestion), (self.end_span, end_suggestion)],
             Applicability::MaybeIncorrect,
         );
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index aeff73c5b..546010135 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -1,15 +1,15 @@
 use rustc_ast as ast;
 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
 use rustc_ast::{AssocConstraint, AssocConstraintKind, NodeId};
-use rustc_ast::{PatKind, RangeEnd, VariantData};
+use rustc_ast::{PatKind, RangeEnd};
 use rustc_errors::{struct_span_err, Applicability, StashKey};
-use rustc_feature::Features;
-use rustc_feature::{AttributeGate, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
-use rustc_session::parse::{feature_err, feature_warn};
+use rustc_feature::{AttributeGate, BuiltinAttribute, Features, GateIssue, BUILTIN_ATTRIBUTE_MAP};
+use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::sym;
 use rustc_span::Span;
+use rustc_target::spec::abi;
 
 macro_rules! gate_feature_fn {
     ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $help: expr) => {{
@@ -84,210 +84,26 @@ impl<'a> PostExpansionVisitor<'a> {
             }
         }
 
-        match symbol_unescaped.as_str() {
-            // Stable
-            "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
-            | "system" => {}
-            "rust-intrinsic" => {
-                gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
-            }
-            "platform-intrinsic" => {
-                gate_feature_post!(
-                    &self,
-                    platform_intrinsics,
-                    span,
-                    "platform intrinsics are experimental and possibly buggy"
-                );
-            }
-            "vectorcall" => {
-                gate_feature_post!(
-                    &self,
-                    abi_vectorcall,
-                    span,
-                    "vectorcall is experimental and subject to change"
-                );
-            }
-            "thiscall" => {
-                gate_feature_post!(
-                    &self,
-                    abi_thiscall,
-                    span,
-                    "thiscall is experimental and subject to change"
-                );
-            }
-            "rust-call" => {
-                gate_feature_post!(
-                    &self,
-                    unboxed_closures,
-                    span,
-                    "rust-call ABI is subject to change"
-                );
-            }
-            "rust-cold" => {
-                gate_feature_post!(
-                    &self,
-                    rust_cold_cc,
-                    span,
-                    "rust-cold is experimental and subject to change"
-                );
-            }
-            "ptx-kernel" => {
-                gate_feature_post!(
-                    &self,
-                    abi_ptx,
-                    span,
-                    "PTX ABIs are experimental and subject to change"
-                );
-            }
-            "unadjusted" => {
-                gate_feature_post!(
-                    &self,
-                    abi_unadjusted,
-                    span,
-                    "unadjusted ABI is an implementation detail and perma-unstable"
-                );
-            }
-            "msp430-interrupt" => {
-                gate_feature_post!(
-                    &self,
-                    abi_msp430_interrupt,
-                    span,
-                    "msp430-interrupt ABI is experimental and subject to change"
-                );
-            }
-            "x86-interrupt" => {
-                gate_feature_post!(
-                    &self,
-                    abi_x86_interrupt,
-                    span,
-                    "x86-interrupt ABI is experimental and subject to change"
-                );
-            }
-            "amdgpu-kernel" => {
-                gate_feature_post!(
-                    &self,
-                    abi_amdgpu_kernel,
-                    span,
-                    "amdgpu-kernel ABI is experimental and subject to change"
-                );
-            }
-            "avr-interrupt" | "avr-non-blocking-interrupt" => {
-                gate_feature_post!(
-                    &self,
-                    abi_avr_interrupt,
-                    span,
-                    "avr-interrupt and avr-non-blocking-interrupt ABIs are experimental and subject to change"
-                );
-            }
-            "efiapi" => {
-                gate_feature_post!(
-                    &self,
-                    abi_efiapi,
-                    span,
-                    "efiapi ABI is experimental and subject to change"
-                );
-            }
-            "C-cmse-nonsecure-call" => {
-                gate_feature_post!(
-                    &self,
-                    abi_c_cmse_nonsecure_call,
+        match abi::is_enabled(&self.features, span, symbol_unescaped.as_str()) {
+            Ok(()) => (),
+            Err(abi::AbiDisabled::Unstable { feature, explain }) => {
+                feature_err_issue(
+                    &self.sess.parse_sess,
+                    feature,
                     span,
-                    "C-cmse-nonsecure-call ABI is experimental and subject to change"
-                );
-            }
-            "C-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "C-unwind ABI is experimental and subject to change"
-                );
-            }
-            "stdcall-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "stdcall-unwind ABI is experimental and subject to change"
-                );
-            }
-            "system-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "system-unwind ABI is experimental and subject to change"
-                );
-            }
-            "thiscall-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "thiscall-unwind ABI is experimental and subject to change"
-                );
-            }
-            "cdecl-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "cdecl-unwind ABI is experimental and subject to change"
-                );
-            }
-            "fastcall-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "fastcall-unwind ABI is experimental and subject to change"
-                );
-            }
-            "vectorcall-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "vectorcall-unwind ABI is experimental and subject to change"
-                );
-            }
-            "aapcs-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "aapcs-unwind ABI is experimental and subject to change"
-                );
-            }
-            "win64-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "win64-unwind ABI is experimental and subject to change"
-                );
-            }
-            "sysv64-unwind" => {
-                gate_feature_post!(
-                    &self,
-                    c_unwind,
-                    span,
-                    "sysv64-unwind ABI is experimental and subject to change"
-                );
-            }
-            "wasm" => {
-                gate_feature_post!(
-                    &self,
-                    wasm_abi,
-                    span,
-                    "wasm ABI is experimental and subject to change"
-                );
+                    GateIssue::Language,
+                    explain,
+                )
+                .emit();
             }
-            abi => {
+            Err(abi::AbiDisabled::Unrecognized) => {
                 if self.sess.opts.pretty.map_or(true, |ppm| ppm.needs_hir()) {
                     self.sess.parse_sess.span_diagnostic.delay_span_bug(
                         span,
-                        &format!("unrecognized ABI not caught in lowering: {}", abi),
+                        &format!(
+                            "unrecognized ABI not caught in lowering: {}",
+                            symbol_unescaped.as_str()
+                        ),
                     );
                 }
             }
@@ -300,46 +116,6 @@ impl<'a> PostExpansionVisitor<'a> {
         }
     }
 
-    fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
-        let has_fields = variants.iter().any(|variant| match variant.data {
-            VariantData::Tuple(..) | VariantData::Struct(..) => true,
-            VariantData::Unit(..) => false,
-        });
-
-        let discriminant_spans = variants
-            .iter()
-            .filter(|variant| match variant.data {
-                VariantData::Tuple(..) | VariantData::Struct(..) => false,
-                VariantData::Unit(..) => true,
-            })
-            .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
-            .collect::<Vec<_>>();
-
-        if !discriminant_spans.is_empty() && has_fields {
-            let mut err = feature_err(
-                &self.sess.parse_sess,
-                sym::arbitrary_enum_discriminant,
-                discriminant_spans.clone(),
-                "custom discriminant values are not allowed in enums with tuple or struct variants",
-            );
-            for sp in discriminant_spans {
-                err.span_label(sp, "disallowed custom discriminant");
-            }
-            for variant in variants.iter() {
-                match &variant.data {
-                    VariantData::Struct(..) => {
-                        err.span_label(variant.span, "struct variant defined here");
-                    }
-                    VariantData::Tuple(..) => {
-                        err.span_label(variant.span, "tuple variant defined here");
-                    }
-                    VariantData::Unit(..) => {}
-                }
-            }
-            err.emit();
-        }
-    }
-
     /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
     fn check_impl_trait(&self, ty: &ast::Ty) {
         struct ImplTraitVisitor<'a> {
@@ -457,26 +233,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 }
             }
 
-            ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
-                for variant in variants {
-                    match (&variant.data, &variant.disr_expr) {
-                        (ast::VariantData::Unit(..), _) => {}
-                        (_, Some(disr_expr)) => gate_feature_post!(
-                            &self,
-                            arbitrary_enum_discriminant,
-                            disr_expr.value.span,
-                            "discriminants on non-unit variants are experimental"
-                        ),
-                        _ => {}
-                    }
-                }
-
-                let has_feature = self.features.arbitrary_enum_discriminant;
-                if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
-                    self.maybe_report_invalid_custom_discriminants(&variants);
-                }
-            }
-
             ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
                 if let ast::ImplPolarity::Negative(span) = polarity {
                     gate_feature_post!(
@@ -645,7 +401,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     if let PatKind::Range(Some(_), None, Spanned { .. }) = inner_pat.kind {
                         gate_feature_post!(
                             &self,
-                            half_open_range_patterns,
+                            half_open_range_patterns_in_slices,
                             pat.span,
                             "`X..` patterns in slices are experimental"
                         );
@@ -701,7 +457,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
     fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
         let is_fn = match i.kind {
             ast::AssocItemKind::Fn(_) => true,
-            ast::AssocItemKind::TyAlias(box ast::TyAlias { ref ty, .. }) => {
+            ast::AssocItemKind::Type(box ast::TyAlias { ref ty, .. }) => {
                 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
                     gate_feature_post!(
                         &self,
@@ -773,7 +529,10 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(generators, "yield syntax is experimental");
     gate_all!(raw_ref_op, "raw address of syntax is experimental");
     gate_all!(const_trait_impl, "const trait impls are experimental");
-    gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
+    gate_all!(
+        half_open_range_patterns_in_slices,
+        "half-open range patterns in slices are unstable"
+    );
     gate_all!(inline_const, "inline-const is experimental");
     gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
     gate_all!(associated_const_equality, "associated const equality is incomplete");
diff --git a/compiler/rustc_ast_passes/src/lib.rs b/compiler/rustc_ast_passes/src/lib.rs
index 8aa9d57f0..f58fffc91 100644
--- a/compiler/rustc_ast_passes/src/lib.rs
+++ b/compiler/rustc_ast_passes/src/lib.rs
@@ -9,7 +9,6 @@
 #![feature(if_let_guard)]
 #![feature(iter_is_partitioned)]
 #![feature(let_chains)]
-#![cfg_attr(bootstrap, feature(let_else))]
 #![recursion_limit = "256"]
 
 #[macro_use]