Merging upstream version 1.71.1+dfsg1.

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

6 files changed, 195 insertions, 144 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index f736f7a96..557950338 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -1,10 +1,11 @@
 use crate::callee::{self, DeferredCallResolution};
+use crate::errors::CtorIsPrivate;
 use crate::method::{self, MethodCallee, SelfSource};
 use crate::rvalue_scopes;
 use crate::{BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy, RawTy};
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed, MultiSpan, StashKey};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::DefId;
@@ -35,7 +36,9 @@ use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Span;
 use rustc_target::abi::FieldIdx;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
-use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCauseCode, ObligationCtxt};
+use rustc_trait_selection::traits::{
+    self, NormalizeExt, ObligationCauseCode, ObligationCtxt, StructurallyNormalizeExt,
+};
 
 use std::collections::hash_map::Entry;
 use std::slice;
@@ -63,9 +66,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     lint::builtin::UNREACHABLE_CODE,
                     id,
                     span,
-                    &msg,
+                    msg.clone(),
                     |lint| {
-                        lint.span_label(span, &msg).span_label(
+                        lint.span_label(span, msg).span_label(
                             orig_span,
                             custom_note
                                 .unwrap_or("any code following this expression is unreachable"),
@@ -275,7 +278,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     _ => {
                         self.tcx.sess.delay_span_bug(
                             expr.span,
-                            &format!(
+                            format!(
                                 "while adjusting {:?}, can't compose {:?} and {:?}",
                                 expr,
                                 entry.get(),
@@ -420,9 +423,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ast_c: &hir::AnonConst,
         param_def_id: DefId,
     ) -> ty::Const<'tcx> {
-        let const_def =
-            ty::WithOptConstParam { did: ast_c.def_id, const_param_did: Some(param_def_id) };
-        let c = ty::Const::from_opt_const_arg_anon_const(self.tcx, const_def);
+        let did = ast_c.def_id;
+        self.tcx.feed_anon_const_type(did, self.tcx.type_of(param_def_id));
+        let c = ty::Const::from_anon_const(self.tcx, did);
         self.register_wf_obligation(
             c.into(),
             self.tcx.hir().span(ast_c.hir_id),
@@ -827,7 +830,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             QPath::TypeRelative(ref qself, ref segment) => {
                 // Don't use `self.to_ty`, since this will register a WF obligation.
-                // If we're trying to call a non-existent method on a trait
+                // If we're trying to call a nonexistent method on a trait
                 // (e.g. `MyTrait::missing_method`), then resolution will
                 // give us a `QPath::TypeRelative` with a trait object as
                 // `qself`. In that case, we want to avoid registering a WF obligation
@@ -853,23 +856,47 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let item_name = item_segment.ident;
         let result = self
             .resolve_fully_qualified_call(span, item_name, ty.normalized, qself.span, hir_id)
+            .and_then(|r| {
+                // lint bare trait if the method is found in the trait
+                if span.edition().rust_2021() && let Some(mut diag) = self.tcx.sess.diagnostic().steal_diagnostic(qself.span, StashKey::TraitMissingMethod) {
+                    diag.emit();
+                }
+                Ok(r)
+            })
             .or_else(|error| {
+                let guar = self
+                    .tcx
+                    .sess
+                    .delay_span_bug(span, "method resolution should've emitted an error");
                 let result = match error {
                     method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
-                    _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
+                    _ => Err(guar),
                 };
 
+                let trait_missing_method =
+                    matches!(error, method::MethodError::NoMatch(_)) && ty.normalized.is_trait();
                 // If we have a path like `MyTrait::missing_method`, then don't register
                 // a WF obligation for `dyn MyTrait` when method lookup fails. Otherwise,
                 // register a WF obligation so that we can detect any additional
                 // errors in the self type.
-                if !(matches!(error, method::MethodError::NoMatch(_)) && ty.normalized.is_trait()) {
+                if !trait_missing_method {
                     self.register_wf_obligation(
                         ty.raw.into(),
                         qself.span,
                         traits::WellFormed(None),
                     );
                 }
+
+                // emit or cancel the diagnostic for bare traits
+                if span.edition().rust_2021() && let Some(mut diag) = self.tcx.sess.diagnostic().steal_diagnostic(qself.span, StashKey::TraitMissingMethod) {
+                    if trait_missing_method {
+                        // cancel the diag for bare traits when meeting `MyTrait::missing_method`
+                        diag.cancel();
+                    } else {
+                        diag.emit();
+                    }
+                }
+
                 if item_name.name != kw::Empty {
                     if let Some(mut e) = self.report_method_error(
                         span,
@@ -879,10 +906,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         error,
                         None,
                         Expectation::NoExpectation,
+                        trait_missing_method && span.edition().rust_2021(), // emits missing method for trait only after edition 2021
                     ) {
                         e.emit();
                     }
                 }
+
                 result
             });
 
@@ -989,8 +1018,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .typeck_results
             .borrow()
             .expr_ty_adjusted_opt(rcvr)
-            .and_then(|ty| expected.map(|expected_ty| expected_ty.peel_refs() == ty.peel_refs()))
-            .unwrap_or(false);
+            .zip(expected)
+            .is_some_and(|(ty, expected_ty)| expected_ty.peel_refs() == ty.peel_refs());
 
         let prev_call_mutates_and_returns_unit = || {
             self.typeck_results
@@ -998,14 +1027,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .type_dependent_def_id(expr.hir_id)
                 .map(|def_id| self.tcx.fn_sig(def_id).skip_binder().skip_binder())
                 .and_then(|sig| sig.inputs_and_output.split_last())
-                .map(|(output, inputs)| {
+                .is_some_and(|(output, inputs)| {
                     output.is_unit()
                         && inputs
                             .get(0)
                             .and_then(|self_ty| self_ty.ref_mutability())
-                            .map_or(false, rustc_ast::Mutability::is_mut)
+                            .is_some_and(rustc_ast::Mutability::is_mut)
                 })
-                .unwrap_or(false)
         };
 
         if !(rcvr_has_the_expected_type || prev_call_mutates_and_returns_unit()) {
@@ -1034,15 +1062,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 rcvr.span,
                 "you probably want to use this value after calling the method...",
             );
-            err.span_note(sp, &modifies_rcvr_note);
-            err.note(&format!("...instead of the `()` output of method `{}`", path_segment.ident));
+            err.span_note(sp, modifies_rcvr_note);
+            err.note(format!("...instead of the `()` output of method `{}`", path_segment.ident));
         } else if let ExprKind::MethodCall(..) = rcvr.kind {
             err.span_note(
                 sp,
                 modifies_rcvr_note.clone() + ", it is not meant to be used in method chains.",
             );
         } else {
-            err.span_note(sp, &modifies_rcvr_note);
+            err.span_note(sp, modifies_rcvr_note);
         }
     }
 
@@ -1172,16 +1200,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        let has_self = path_segs
-            .last()
-            .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
-            .unwrap_or(false);
+        let has_self =
+            path_segs.last().is_some_and(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self);
 
         let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
             let ty = self.handle_raw_ty(span, tcx.at(span).type_of(impl_def_id).subst_identity());
             match ty.normalized.ty_adt_def() {
                 Some(adt_def) if adt_def.has_ctor() => {
                     let (ctor_kind, ctor_def_id) = adt_def.non_enum_variant().ctor.unwrap();
+                    // Check the visibility of the ctor.
+                    let vis = tcx.visibility(ctor_def_id);
+                    if !vis.is_accessible_from(tcx.parent_module(hir_id).to_def_id(), tcx) {
+                        tcx.sess
+                            .emit_err(CtorIsPrivate { span, def: tcx.def_path_str(adt_def.did()) });
+                    }
                     let new_res = Res::Def(DefKind::Ctor(CtorOf::Struct, ctor_kind), ctor_def_id);
                     let user_substs = Self::user_substs_for_adt(ty);
                     user_self_ty = user_substs.user_self_ty;
@@ -1374,7 +1406,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Err(_) => {
                     self.tcx.sess.delay_span_bug(
                         span,
-                        &format!(
+                        format!(
                         "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
                         self_ty,
                         impl_ty,
@@ -1434,10 +1466,33 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// Resolves `typ` by a single level if `typ` is a type variable.
+    ///
+    /// When the new solver is enabled, this will also attempt to normalize
+    /// the type if it's a projection (note that it will not deeply normalize
+    /// projections within the type, just the outermost layer of the type).
+    ///
     /// If no resolution is possible, then an error is reported.
     /// Numeric inference variables may be left unresolved.
     pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
-        let ty = self.resolve_vars_with_obligations(ty);
+        let mut ty = self.resolve_vars_with_obligations(ty);
+
+        if self.tcx.trait_solver_next()
+            && let ty::Alias(ty::Projection, _) = ty.kind()
+        {
+            match self
+                .at(&self.misc(sp), self.param_env)
+                .structurally_normalize(ty, &mut **self.fulfillment_cx.borrow_mut())
+            {
+                Ok(normalized_ty) => {
+                    ty = normalized_ty;
+                },
+                Err(errors) => {
+                    let guar = self.err_ctxt().report_fulfillment_errors(&errors);
+                    return self.tcx.ty_error(guar);
+                }
+            }
+        }
+
         if !ty.is_ty_var() {
             ty
         } else {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index f879ccbb3..3efdab534 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -164,24 +164,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 {
                     for param in
                         [param_to_point_at, fallback_param_to_point_at, self_param_to_point_at]
+                            .into_iter()
+                            .flatten()
                     {
-                        if let Some(param) = param {
-                            let refined_expr = self.point_at_field_if_possible(
-                                def_id,
-                                param,
-                                variant_def_id,
-                                fields,
-                            );
-
-                            match refined_expr {
-                                None => {}
-                                Some((refined_expr, _)) => {
-                                    error.obligation.cause.span = refined_expr
-                                        .span
-                                        .find_ancestor_in_same_ctxt(error.obligation.cause.span)
-                                        .unwrap_or(refined_expr.span);
-                                    return true;
-                                }
+                        let refined_expr =
+                            self.point_at_field_if_possible(def_id, param, variant_def_id, fields);
+
+                        match refined_expr {
+                            None => {}
+                            Some((refined_expr, _)) => {
+                                error.obligation.cause.span = refined_expr
+                                    .span
+                                    .find_ancestor_in_same_ctxt(error.obligation.cause.span)
+                                    .unwrap_or(refined_expr.span);
+                                return true;
                             }
                         }
                     }
@@ -282,9 +278,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
     ) -> bool {
         if let traits::FulfillmentErrorCode::CodeSelectionError(
-            traits::SelectionError::OutputTypeParameterMismatch(_, expected, _),
+            traits::SelectionError::OutputTypeParameterMismatch(box traits::SelectionOutputTypeParameterMismatch{
+                expected_trait_ref, ..
+            }),
         ) = error.code
-            && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected.skip_binder().self_ty().kind()
+            && let ty::Closure(def_id, _) | ty::Generator(def_id, ..) = expected_trait_ref.skip_binder().self_ty().kind()
             && span.overlaps(self.tcx.def_span(*def_id))
         {
             true
@@ -334,7 +332,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// expression mentioned.
     ///
     /// `blame_specific_arg_if_possible` will find the most-specific expression anywhere inside
-    /// the provided function call expression, and mark it as responsible for the fullfillment
+    /// the provided function call expression, and mark it as responsible for the fulfillment
     /// error.
     fn blame_specific_arg_if_possible(
         &self,
@@ -485,7 +483,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // For the purposes of this function, we hope that it is a `struct` type, and that our current `expr` is a literal of
         // that struct type.
         let impl_trait_self_ref = if self.tcx.is_trait_alias(obligation.impl_or_alias_def_id) {
-            self.tcx.mk_trait_ref(
+            ty::TraitRef::new(
+                self.tcx,
                 obligation.impl_or_alias_def_id,
                 ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_or_alias_def_id),
             )
@@ -846,7 +845,7 @@ fn find_param_in_ty<'tcx>(
             return true;
         }
         if let ty::GenericArgKind::Type(ty) = arg.unpack()
-                && let ty::Alias(ty::Projection, ..) = ty.kind()
+                && let ty::Alias(ty::Projection | ty::Inherent, ..) = ty.kind()
             {
                 // This logic may seem a bit strange, but typically when
                 // we have a projection type in a function signature, the
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs
index 6f26afcaf..d45e3d395 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs
@@ -1,6 +1,6 @@
 use std::cmp;
 
-use rustc_index::vec::IndexVec;
+use rustc_index::IndexVec;
 use rustc_middle::ty::error::TypeError;
 
 rustc_index::newtype_index! {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index ea1b52daa..eba5c829e 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -2,8 +2,8 @@ use crate::coercion::CoerceMany;
 use crate::fn_ctxt::arg_matrix::{ArgMatrix, Compatibility, Error, ExpectedIdx, ProvidedIdx};
 use crate::gather_locals::Declaration;
 use crate::method::MethodCallee;
-use crate::Expectation::*;
 use crate::TupleArgumentsFlag::*;
+use crate::{errors, Expectation::*};
 use crate::{
     struct_span_err, BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy, Needs, RawTy,
     TupleArgumentsFlag,
@@ -21,7 +21,7 @@ use rustc_hir_analysis::astconv::AstConv;
 use rustc_hir_analysis::check::intrinsicck::InlineAsmCtxt;
 use rustc_hir_analysis::check::potentially_plural_count;
 use rustc_hir_analysis::structured_errors::StructuredDiagnostic;
-use rustc_index::vec::IndexVec;
+use rustc_index::IndexVec;
 use rustc_infer::infer::error_reporting::{FailureCode, ObligationCauseExt};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::TypeTrace;
@@ -283,19 +283,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if idx == 1 && !self.tcx.is_const_fn_raw(*def_id) {
                         self.tcx
                             .sess
-                            .struct_span_err(provided_arg.span, "this argument must be a `const fn`")
-                            .help("consult the documentation on `const_eval_select` for more information")
-                            .emit();
+                            .emit_err(errors::ConstSelectMustBeConst { span: provided_arg.span });
                     }
                 } else {
-                    self.tcx
-                        .sess
-                        .struct_span_err(provided_arg.span, "this argument must be a function item")
-                        .note(format!("expected a function item, found {checked_ty}"))
-                        .help(
-                            "consult the documentation on `const_eval_select` for more information",
-                        )
-                        .emit();
+                    self.tcx.sess.emit_err(errors::ConstSelectMustBeFn {
+                        span: provided_arg.span,
+                        ty: checked_ty,
+                    });
                 }
             }
 
@@ -368,7 +362,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     continue;
                 }
 
-                let is_closure = matches!(arg.kind, ExprKind::Closure { .. });
+                // For this check, we do *not* want to treat async generator closures (async blocks)
+                // as proper closures. Doing so would regress type inference when feeding
+                // the return value of an argument-position async block to an argument-position
+                // closure wrapped in a block.
+                // See <https://github.com/rust-lang/rust/issues/112225>.
+                let is_closure = if let ExprKind::Closure(closure) = arg.kind {
+                    !tcx.generator_is_async(closure.def_id.to_def_id())
+                } else {
+                    false
+                };
                 if is_closure != check_closures {
                     continue;
                 }
@@ -691,7 +694,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     } else {
                         err = tcx.sess.struct_span_err_with_code(
                             full_call_span,
-                            &format!(
+                            format!(
                                 "{call_name} takes {}{} but {} {} supplied",
                                 if c_variadic { "at least " } else { "" },
                                 potentially_plural_count(
@@ -744,17 +747,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if cfg!(debug_assertions) {
                 span_bug!(error_span, "expected errors from argument matrix");
             } else {
-                tcx.sess
-                    .struct_span_err(
-                        error_span,
-                        "argument type mismatch was detected, \
-                        but rustc had trouble determining where",
-                    )
-                    .note(
-                        "we would appreciate a bug report: \
-                        https://github.com/rust-lang/rust/issues/new",
-                    )
-                    .emit();
+                tcx.sess.emit_err(errors::ArgMismatchIndeterminate { span: error_span });
             }
             return;
         }
@@ -844,7 +837,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             tcx.sess.struct_span_err_with_code(
                 full_call_span,
-                &format!(
+                format!(
                     "this {} takes {}{} but {} {} supplied",
                     call_name,
                     if c_variadic { "at least " } else { "" },
@@ -892,7 +885,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut errors = errors.into_iter().peekable();
         let mut only_extras_so_far = errors
             .peek()
-            .map_or(false, |first| matches!(first, Error::Extra(arg_idx) if arg_idx.index() == 0));
+            .is_some_and(|first| matches!(first, Error::Extra(arg_idx) if arg_idx.index() == 0));
         let mut suggestions = vec![];
         while let Some(error) = errors.next() {
             only_extras_so_far &= matches!(error, Error::Extra(_));
@@ -1219,7 +1212,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             SuggestionText::Remove(plural) => {
                 err.multipart_suggestion(
-                    &format!("remove the extra argument{}", if plural { "s" } else { "" }),
+                    format!("remove the extra argument{}", if plural { "s" } else { "" }),
                     suggestions,
                     Applicability::HasPlaceholders,
                 );
@@ -1269,7 +1262,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             suggestion += ")";
             err.span_suggestion_verbose(
                 suggestion_span,
-                &suggestion_text,
+                suggestion_text,
                 suggestion,
                 Applicability::HasPlaceholders,
             );
@@ -1316,6 +1309,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 opt_ty.unwrap_or_else(|| self.next_float_var())
             }
             ast::LitKind::Bool(_) => tcx.types.bool,
+            ast::LitKind::CStr(_, _) => tcx.mk_imm_ref(
+                tcx.lifetimes.re_static,
+                tcx.type_of(tcx.require_lang_item(hir::LangItem::CStr, Some(lit.span)))
+                    .skip_binder(),
+            ),
             ast::LitKind::Err => tcx.ty_error_misc(),
         }
     }
@@ -1530,7 +1528,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // case we can ignore the tail expression (e.g., `'a: {
         // break 'a 22; }` would not force the type of the block
         // to be `()`).
-        let tail_expr = blk.expr.as_ref();
         let coerce_to_ty = expected.coercion_target_type(self, blk.span);
         let coerce = if blk.targeted_by_break {
             CoerceMany::new(coerce_to_ty)
@@ -1548,13 +1545,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // check the tail expression **without** holding the
             // `enclosing_breakables` lock below.
-            let tail_expr_ty = tail_expr.map(|t| self.check_expr_with_expectation(t, expected));
+            let tail_expr_ty =
+                blk.expr.map(|expr| (expr, self.check_expr_with_expectation(expr, expected)));
 
             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
             let ctxt = enclosing_breakables.find_breakable(blk.hir_id);
             let coerce = ctxt.coerce.as_mut().unwrap();
-            if let Some(tail_expr_ty) = tail_expr_ty {
-                let tail_expr = tail_expr.unwrap();
+            if let Some((tail_expr, tail_expr_ty)) = tail_expr_ty {
                 let span = self.get_expr_coercion_span(tail_expr);
                 let cause = self.cause(span, ObligationCauseCode::BlockTailExpression(blk.hir_id));
                 let ty_for_diagnostic = coerce.merged_ty();
@@ -1607,6 +1604,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         &self.misc(sp),
                         &mut |err| {
                             if let Some(expected_ty) = expected.only_has_type(self) {
+                                if blk.stmts.is_empty() && blk.expr.is_none() {
+                                    self.suggest_boxing_when_appropriate(
+                                        err,
+                                        blk.span,
+                                        blk.hir_id,
+                                        expected_ty,
+                                        self.tcx.mk_unit(),
+                                    );
+                                }
                                 if !self.consider_removing_semicolon(blk, expected_ty, err) {
                                     self.err_ctxt().consider_returning_binding(
                                         blk,
@@ -1619,7 +1625,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     // silence this redundant error, as we already emit E0070.
 
                                     // Our block must be a `assign desugar local; assignment`
-                                    if let Some(hir::Node::Block(hir::Block {
+                                    if let hir::Block {
                                         stmts:
                                             [
                                                 hir::Stmt {
@@ -1641,7 +1647,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                                 },
                                             ],
                                         ..
-                                    })) = self.tcx.hir().find(blk.hir_id)
+                                    } = blk
                                     {
                                         self.comes_from_while_condition(blk.hir_id, |_| {
                                             err.downgrade_to_delayed_bug();
@@ -1911,7 +1917,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 _ => {
                     // Look for a user-provided impl of a `Fn` trait, and point to it.
                     let new_def_id = self.probe(|_| {
-                        let trait_ref = self.tcx.mk_trait_ref(
+                        let trait_ref = ty::TraitRef::new(self.tcx,
                             call_kind.to_def_id(self.tcx),
                             [
                                 callee_ty,
@@ -1963,7 +1969,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 spans.push_span_label(param.span, "");
             }
 
-            err.span_note(spans, &format!("{} defined here", self.tcx.def_descr(def_id)));
+            err.span_note(spans, format!("{} defined here", self.tcx.def_descr(def_id)));
         } else if let Some(hir::Node::Expr(e)) = self.tcx.hir().get_if_local(def_id)
             && let hir::ExprKind::Closure(hir::Closure { body, .. }) = &e.kind
         {
@@ -1974,11 +1980,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             } else {
                 ("closure", self.tcx.def_span(def_id))
             };
-            err.span_note(span, &format!("{} defined here", kind));
+            err.span_note(span, format!("{} defined here", kind));
         } else {
             err.span_note(
                 self.tcx.def_span(def_id),
-                &format!("{} defined here", self.tcx.def_descr(def_id)),
+                format!("{} defined here", self.tcx.def_descr(def_id)),
             );
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index c6fd0b610..67f45f9aa 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -17,7 +17,6 @@ use rustc_infer::infer;
 use rustc_infer::infer::error_reporting::TypeErrCtxt;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
-use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::symbol::Ident;
@@ -169,7 +168,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         ocx.normalize(&ObligationCause::dummy(), self.param_env, fn_sig);
                     if ocx.select_all_or_error().is_empty() {
                         let normalized_fn_sig = self.resolve_vars_if_possible(normalized_fn_sig);
-                        if !normalized_fn_sig.needs_infer() {
+                        if !normalized_fn_sig.has_infer() {
                             return normalized_fn_sig;
                         }
                     }
@@ -250,16 +249,12 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
     }
 
     fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
-        if let Some(param) = param {
-            if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
-                return ty;
-            }
-            unreachable!()
-        } else {
-            self.next_ty_var(TypeVariableOrigin {
+        match param {
+            Some(param) => self.var_for_def(span, param).as_type().unwrap(),
+            None => self.next_ty_var(TypeVariableOrigin {
                 kind: TypeVariableOriginKind::TypeInference,
                 span,
-            })
+            }),
         }
     }
 
@@ -269,16 +264,12 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
         param: Option<&ty::GenericParamDef>,
         span: Span,
     ) -> Const<'tcx> {
-        if let Some(param) = param {
-            if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
-                return ct;
-            }
-            unreachable!()
-        } else {
-            self.next_const_var(
+        match param {
+            Some(param) => self.var_for_def(span, param).as_const().unwrap(),
+            None => self.next_const_var(
                 ty,
                 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
-            )
+            ),
         }
     }
 
@@ -309,7 +300,7 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
         match ty.kind() {
             ty::Adt(adt_def, _) => Some(*adt_def),
             // FIXME(#104767): Should we handle bound regions here?
-            ty::Alias(ty::Projection, _) if !ty.has_escaping_bound_vars() => {
+            ty::Alias(ty::Projection | ty::Inherent, _) if !ty.has_escaping_bound_vars() => {
                 self.normalize(span, ty).ty_adt_def()
             }
             _ => None,
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 5fda4e191..c4add4dbd 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -1,6 +1,6 @@
 use super::FnCtxt;
 
-use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel};
+use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel, SuggestBoxing};
 use crate::fluent_generated as fluent;
 use crate::method::probe::{IsSuggestion, Mode, ProbeScope};
 use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX};
@@ -9,7 +9,8 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{
-    Expr, ExprKind, GenericBound, Node, Path, QPath, Stmt, StmtKind, TyKind, WherePredicate,
+    AsyncGeneratorKind, Expr, ExprKind, GeneratorKind, GenericBound, HirId, Node, Path, QPath,
+    Stmt, StmtKind, TyKind, WherePredicate,
 };
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::traits::{self, StatementAsExpression};
@@ -274,13 +275,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
     ) -> bool {
         let expr = expr.peel_blocks();
-        if let Some((sp, msg, suggestion, applicability, verbose, annotation)) =
-            self.check_ref(expr, found, expected)
+        if let Some((suggestion, msg, applicability, verbose, annotation)) =
+            self.suggest_deref_or_ref(expr, found, expected)
         {
             if verbose {
-                err.span_suggestion_verbose(sp, &msg, suggestion, applicability);
+                err.multipart_suggestion_verbose(msg, suggestion, applicability);
             } else {
-                err.span_suggestion(sp, &msg, suggestion, applicability);
+                err.multipart_suggestion(msg, suggestion, applicability);
             }
             if annotation {
                 let suggest_annotation = match expr.peel_drop_temps().kind {
@@ -342,7 +343,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 err.span_label(sp, format!("{descr} `{name}` defined here"));
             }
             return true;
-        } else if self.check_for_cast(err, expr, found, expected, expected_ty_expr) {
+        } else if self.suggest_cast(err, expr, found, expected, expected_ty_expr) {
             return true;
         } else {
             let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id);
@@ -438,33 +439,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(in super::super) fn suggest_boxing_when_appropriate(
         &self,
         err: &mut Diagnostic,
-        expr: &hir::Expr<'_>,
+        span: Span,
+        hir_id: HirId,
         expected: Ty<'tcx>,
         found: Ty<'tcx>,
     ) -> bool {
-        if self.tcx.hir().is_inside_const_context(expr.hir_id) {
-            // Do not suggest `Box::new` in const context.
-            return false;
-        }
-        if !expected.is_box() || found.is_box() {
+        // Do not suggest `Box::new` in const context.
+        if self.tcx.hir().is_inside_const_context(hir_id) || !expected.is_box() || found.is_box() {
             return false;
         }
-        let boxed_found = self.tcx.mk_box(found);
-        if self.can_coerce(boxed_found, expected) {
-            err.multipart_suggestion(
-                "store this in the heap by calling `Box::new`",
-                vec![
-                    (expr.span.shrink_to_lo(), "Box::new(".to_string()),
-                    (expr.span.shrink_to_hi(), ")".to_string()),
-                ],
-                Applicability::MachineApplicable,
-            );
-            err.note(
-                "for more on the distinction between the stack and the heap, read \
-                 https://doc.rust-lang.org/book/ch15-01-box.html, \
-                 https://doc.rust-lang.org/rust-by-example/std/box.html, and \
-                 https://doc.rust-lang.org/std/boxed/index.html",
-            );
+        if self.can_coerce(self.tcx.mk_box(found), expected) {
+            let suggest_boxing = match found.kind() {
+                ty::Tuple(tuple) if tuple.is_empty() => {
+                    SuggestBoxing::Unit { start: span.shrink_to_lo(), end: span }
+                }
+                ty::Generator(def_id, ..)
+                    if matches!(
+                        self.tcx.generator_kind(def_id),
+                        Some(GeneratorKind::Async(AsyncGeneratorKind::Closure))
+                    ) =>
+                {
+                    SuggestBoxing::AsyncBody
+                }
+                _ => SuggestBoxing::Other { start: span.shrink_to_lo(), end: span.shrink_to_hi() },
+            };
+            err.subdiagnostic(suggest_boxing);
+
             true
         } else {
             false
@@ -794,7 +794,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return;
         };
 
-        // get all where BoundPredicates here, because they are used in to cases below
+        // get all where BoundPredicates here, because they are used in two cases below
         let where_predicates = predicates
             .iter()
             .filter_map(|p| match p {
@@ -1096,10 +1096,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.tcx,
                 self.misc(expr.span),
                 self.param_env,
-                ty::Binder::dummy(self.tcx.mk_trait_ref(
+                ty::TraitRef::new(self.tcx,
                     into_def_id,
                     [expr_ty, expected_ty]
-                )),
+                ),
             ))
         {
             let sugg = if expr.precedence().order() >= PREC_POSTFIX {
@@ -1252,7 +1252,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 node: rustc_ast::LitKind::Int(lit, rustc_ast::LitIntType::Unsuffixed),
                 span,
             }) => {
-                let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) else { return false; };
+                let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(*span) else { return false; };
                 if !(snippet.starts_with("0x") || snippet.starts_with("0X")) {
                     return false;
                 }
@@ -1311,7 +1311,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // We have satisfied all requirements to provide a suggestion. Emit it.
         err.span_suggestion(
-            span,
+            *span,
             format!("if you meant to create a null pointer, use `{null_path_str}()`"),
             null_path_str + "()",
             Applicability::MachineApplicable,
@@ -1384,7 +1384,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
         let item_ty = self.tcx.type_of(item.def_id).subst_identity();
         // FIXME(compiler-errors): This check is *so* rudimentary
-        if item_ty.needs_subst() {
+        if item_ty.has_param() {
             return false;
         }
         if self.can_coerce(item_ty, expected_ty) {
@@ -1438,7 +1438,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             && !results.expr_adjustments(callee_expr).iter().any(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(..)))
             // Check that we're in fact trying to clone into the expected type
             && self.can_coerce(*pointee_ty, expected_ty)
-            && let trait_ref = ty::Binder::dummy(self.tcx.mk_trait_ref(clone_trait_did, [expected_ty]))
+            && let trait_ref = ty::TraitRef::new(self.tcx, clone_trait_did, [expected_ty])
             // And the expected type doesn't implement `Clone`
             && !self.predicate_must_hold_considering_regions(&traits::Obligation::new(
                 self.tcx,
@@ -1449,7 +1449,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             diag.span_note(
                 callee_expr.span,
-                &format!(
+                format!(
                     "`{expected_ty}` does not implement `Clone`, so `{found_ty}` was cloned instead"
                 ),
             );