Merging upstream version 1.70.0+dfsg1.

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

27 files changed, 1033 insertions, 909 deletions

diff --git a/compiler/rustc_hir_typeck/locales/en-US.ftl b/compiler/rustc_hir_typeck/messages.ftl
index adfcbc36a..2c537bf40 100644
--- a/compiler/rustc_hir_typeck/locales/en-US.ftl
+++ b/compiler/rustc_hir_typeck/messages.ftl
@@ -4,14 +4,14 @@ hir_typeck_field_multiply_specified_in_initializer =
     .previous_use_label = first use of `{$ident}`
 
 hir_typeck_copy_impl_on_type_with_dtor =
-    the trait `Copy` may not be implemented for this type; the type has a destructor
+    the trait `Copy` cannot be implemented for this type; the type has a destructor
     .label = `Copy` not allowed on types with destructors
 
 hir_typeck_multiple_relaxed_default_bounds =
     type parameter has more than one relaxed default bound, only one is supported
 
 hir_typeck_copy_impl_on_non_adt =
-    the trait `Copy` may not be implemented for this type
+    the trait `Copy` cannot be implemented for this type
     .label = type is not a structure or enumeration
 
 hir_typeck_trait_object_declared_with_no_traits =
diff --git a/compiler/rustc_hir_typeck/src/_match.rs b/compiler/rustc_hir_typeck/src/_match.rs
index e19ef2ff3..6c2ce6272 100644
--- a/compiler/rustc_hir_typeck/src/_match.rs
+++ b/compiler/rustc_hir_typeck/src/_match.rs
@@ -299,7 +299,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             {
                 // check that the `if` expr without `else` is the fn body's expr
                 if expr.span == sp {
-                    return self.get_fn_decl(hir_id).and_then(|(fn_decl, _)| {
+                    return self.get_fn_decl(hir_id).and_then(|(_, fn_decl, _)| {
                         let span = fn_decl.output.span();
                         let snippet = self.tcx.sess.source_map().span_to_snippet(span).ok()?;
                         Some((span, format!("expected `{snippet}` because of this return type")))
@@ -538,8 +538,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 // FIXME(rpitit): This will need to be fixed when we move to associated types
                                 assert!(matches!(
                                     *trait_pred.trait_ref.self_ty().kind(),
-                                    ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                                    if def_id == rpit_def_id && substs == substs
+                                    ty::Alias(_, ty::AliasTy { def_id, substs: alias_substs, .. })
+                                    if def_id == rpit_def_id && substs == alias_substs
                                 ));
                                 ty::PredicateKind::Clause(ty::Clause::Trait(
                                     trait_pred.with_self_ty(self.tcx, ty),
@@ -548,8 +548,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             ty::PredicateKind::Clause(ty::Clause::Projection(mut proj_pred)) => {
                                 assert!(matches!(
                                     *proj_pred.projection_ty.self_ty().kind(),
-                                    ty::Alias(_, ty::AliasTy { def_id, substs, .. })
-                                    if def_id == rpit_def_id && substs == substs
+                                    ty::Alias(_, ty::AliasTy { def_id, substs: alias_substs, .. })
+                                    if def_id == rpit_def_id && substs == alias_substs
                                 ));
                                 proj_pred = proj_pred.with_self_ty(self.tcx, ty);
                                 ty::PredicateKind::Clause(ty::Clause::Projection(proj_pred))
diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index 6a0d5c011..5235710a2 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -311,9 +311,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let fn_decl_span = if hir.body(body).generator_kind
                 == Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure))
             {
-                // Actually need to unwrap a few more layers of HIR to get to
+                // Actually need to unwrap one more layer of HIR to get to
                 // the _real_ closure...
-                let async_closure = hir.parent_id(hir.parent_id(parent_hir_id));
+                let async_closure = hir.parent_id(parent_hir_id);
                 if let hir::Node::Expr(hir::Expr {
                     kind: hir::ExprKind::Closure(&hir::Closure { fn_decl_span, .. }),
                     ..
@@ -668,7 +668,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         if !self.maybe_suggest_bad_array_definition(&mut err, call_expr, callee_expr) {
             if let Some((maybe_def, output_ty, _)) = self.extract_callable_info(callee_ty)
-                && !self.type_is_sized_modulo_regions(self.param_env, output_ty, callee_expr.span)
+                && !self.type_is_sized_modulo_regions(self.param_env, output_ty)
             {
                 let descr = match maybe_def {
                     DefIdOrName::DefId(def_id) => self.tcx.def_descr(def_id),
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 316c2a7ee..1481c038c 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -96,20 +96,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let t = self.resolve_vars_if_possible(t);
         t.error_reported()?;
 
-        if self.type_is_sized_modulo_regions(self.param_env, t, span) {
+        if self.type_is_sized_modulo_regions(self.param_env, t) {
             return Ok(Some(PointerKind::Thin));
         }
 
         Ok(match *t.kind() {
             ty::Slice(_) | ty::Str => Some(PointerKind::Length),
             ty::Dynamic(ref tty, _, ty::Dyn) => Some(PointerKind::VTable(tty.principal_def_id())),
-            ty::Adt(def, substs) if def.is_struct() => match def.non_enum_variant().fields.last() {
-                None => Some(PointerKind::Thin),
-                Some(f) => {
-                    let field_ty = self.field_ty(span, f, substs);
-                    self.pointer_kind(field_ty, span)?
+            ty::Adt(def, substs) if def.is_struct() => {
+                match def.non_enum_variant().fields.raw.last() {
+                    None => Some(PointerKind::Thin),
+                    Some(f) => {
+                        let field_ty = self.field_ty(span, f, substs);
+                        self.pointer_kind(field_ty, span)?
+                    }
                 }
-            },
+            }
             ty::Tuple(fields) => match fields.last() {
                 None => Some(PointerKind::Thin),
                 Some(&f) => self.pointer_kind(f, span)?,
@@ -722,7 +724,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
 
         debug!("check_cast({}, {:?} as {:?})", self.expr.hir_id, self.expr_ty, self.cast_ty);
 
-        if !fcx.type_is_sized_modulo_regions(fcx.param_env, self.cast_ty, self.span)
+        if !fcx.type_is_sized_modulo_regions(fcx.param_env, self.cast_ty)
             && !self.cast_ty.has_infer_types()
         {
             self.report_cast_to_unsized_type(fcx);
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index d84fabb78..8c2495e1d 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -2,13 +2,12 @@
 
 use super::{check_fn, Expectation, FnCtxt, GeneratorTypes};
 
-use hir::def::DefKind;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::LateBoundRegionConversionTime;
+use rustc_infer::infer::{DefineOpaqueTypes, LateBoundRegionConversionTime};
 use rustc_infer::infer::{InferOk, InferResult};
 use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::ty::subst::InternalSubsts;
@@ -205,15 +204,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut expected_sig = None;
         let mut expected_kind = None;
 
-        for obligation in traits::elaborate_predicates_with_span(
+        for (pred, span) in traits::elaborate(
             self.tcx,
             // Reverse the obligations here, since `elaborate_*` uses a stack,
             // and we want to keep inference generally in the same order of
             // the registered obligations.
             predicates.rev(),
-        ) {
-            debug!(?obligation.predicate);
-            let bound_predicate = obligation.predicate.kind();
+        )
+        // We only care about self bounds
+        .filter_only_self()
+        {
+            debug!(?pred);
+            let bound_predicate = pred.kind();
 
             // Given a Projection predicate, we can potentially infer
             // the complete signature.
@@ -221,9 +223,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let ty::PredicateKind::Clause(ty::Clause::Projection(proj_predicate)) = bound_predicate.skip_binder()
             {
                 let inferred_sig = self.normalize(
-                    obligation.cause.span,
+                    span,
                     self.deduce_sig_from_projection(
-                    Some(obligation.cause.span),
+                    Some(span),
                         bound_predicate.rebind(proj_predicate),
                     ),
                 );
@@ -398,7 +400,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ///
     /// Here:
     /// - E would be `fn(&u32) -> &u32`.
-    /// - S would be `fn(&u32) ->
+    /// - S would be `fn(&u32) -> ?T`
     /// - E' is `&'!0 u32 -> &'!0 u32`
     /// - S' is `&'?0 u32 -> ?T`
     ///
@@ -563,10 +565,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ) {
                 // Check that E' = S'.
                 let cause = self.misc(hir_ty.span);
-                let InferOk { value: (), obligations } = self
-                    .at(&cause, self.param_env)
-                    .define_opaque_types(true)
-                    .eq(*expected_ty, supplied_ty)?;
+                let InferOk { value: (), obligations } = self.at(&cause, self.param_env).eq(
+                    DefineOpaqueTypes::Yes,
+                    *expected_ty,
+                    supplied_ty,
+                )?;
                 all_obligations.extend(obligations);
             }
 
@@ -576,10 +579,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 supplied_sig.output(),
             );
             let cause = &self.misc(decl.output.span());
-            let InferOk { value: (), obligations } = self
-                .at(cause, self.param_env)
-                .define_opaque_types(true)
-                .eq(expected_sigs.liberated_sig.output(), supplied_output_ty)?;
+            let InferOk { value: (), obligations } = self.at(cause, self.param_env).eq(
+                DefineOpaqueTypes::Yes,
+                expected_sigs.liberated_sig.output(),
+                supplied_output_ty,
+            )?;
             all_obligations.extend(obligations);
 
             let inputs = inputs.into_iter().map(|ty| self.resolve_vars_if_possible(ty));
@@ -713,14 +717,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .subst_iter_copied(self.tcx, substs)
                 .find_map(|(p, s)| get_future_output(p, s))?,
             ty::Error(_) => return None,
-            ty::Alias(ty::Projection, proj)
-                if self.tcx.def_kind(proj.def_id) == DefKind::ImplTraitPlaceholder =>
-            {
-                self.tcx
-                    .bound_explicit_item_bounds(proj.def_id)
-                    .subst_iter_copied(self.tcx, proj.substs)
-                    .find_map(|(p, s)| get_future_output(p, s))?
-            }
+            ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => self
+                .tcx
+                .bound_explicit_item_bounds(proj.def_id)
+                .subst_iter_copied(self.tcx, proj.substs)
+                .find_map(|(p, s)| get_future_output(p, s))?,
             _ => span_bug!(
                 self.tcx.def_span(expr_def_id),
                 "async fn generator return type not an inference variable: {ret_ty}"
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 00b86890b..8fa3bcd68 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -45,8 +45,8 @@ use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::Expr;
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::{Coercion, InferOk, InferResult};
-use rustc_infer::traits::Obligation;
+use rustc_infer::infer::{Coercion, DefineOpaqueTypes, InferOk, InferResult};
+use rustc_infer::traits::{Obligation, PredicateObligation};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast,
@@ -143,11 +143,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
     fn unify(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> InferResult<'tcx, Ty<'tcx>> {
         debug!("unify(a: {:?}, b: {:?}, use_lub: {})", a, b, self.use_lub);
         self.commit_if_ok(|_| {
-            let at = self.at(&self.cause, self.fcx.param_env).define_opaque_types(true);
+            let at = self.at(&self.cause, self.fcx.param_env);
             if self.use_lub {
-                at.lub(b, a)
+                at.lub(DefineOpaqueTypes::Yes, b, a)
             } else {
-                at.sup(b, a)
+                at.sup(DefineOpaqueTypes::Yes, b, a)
                     .map(|InferOk { value: (), obligations }| InferOk { value: a, obligations })
             }
         })
@@ -175,7 +175,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             // so this will have the side-effect of making sure we have no ambiguities
             // due to `[type error]` and `_` not coercing together.
             let _ = self.commit_if_ok(|_| {
-                self.at(&self.cause, self.param_env).define_opaque_types(true).eq(a, b)
+                self.at(&self.cause, self.param_env).eq(DefineOpaqueTypes::Yes, a, b)
             });
             return success(vec![], self.fcx.tcx.ty_error(guar), vec![]);
         }
@@ -597,13 +597,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         // and almost never more than 3. By using a SmallVec we avoid an
         // allocation, at the (very small) cost of (occasionally) having to
         // shift subsequent elements down when removing the front element.
-        let mut queue: SmallVec<[_; 4]> = smallvec![traits::predicate_for_trait_def(
+        let mut queue: SmallVec<[PredicateObligation<'tcx>; 4]> = smallvec![Obligation::new(
             self.tcx,
-            self.fcx.param_env,
             cause,
-            coerce_unsized_did,
-            0,
-            [coerce_source, coerce_target]
+            self.fcx.param_env,
+            self.tcx.mk_trait_ref(coerce_unsized_did, [coerce_source, coerce_target])
         )];
 
         let mut has_unsized_tuple_coercion = false;
@@ -651,9 +649,9 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                         let self_ty = trait_pred.skip_binder().self_ty();
                         let unsize_ty = trait_pred.skip_binder().trait_ref.substs[1].expect_ty();
                         debug!("coerce_unsized: ambiguous unsize case for {:?}", trait_pred);
-                        match (&self_ty.kind(), &unsize_ty.kind()) {
-                            (ty::Infer(ty::TyVar(v)), ty::Dynamic(..))
-                                if self.type_var_is_sized(*v) =>
+                        match (self_ty.kind(), unsize_ty.kind()) {
+                            (&ty::Infer(ty::TyVar(v)), ty::Dynamic(..))
+                                if self.type_var_is_sized(v) =>
                             {
                                 debug!("coerce_unsized: have sized infer {:?}", v);
                                 coercion.obligations.push(obligation);
@@ -1101,9 +1099,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     (ty::FnDef(..), ty::FnDef(..)) => {
                         // Don't reify if the function types have a LUB, i.e., they
                         // are the same function and their parameters have a LUB.
-                        match self
-                            .commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
-                        {
+                        match self.commit_if_ok(|_| {
+                            self.at(cause, self.param_env).lub(
+                                DefineOpaqueTypes::No,
+                                prev_ty,
+                                new_ty,
+                            )
+                        }) {
                             // We have a LUB of prev_ty and new_ty, just return it.
                             Ok(ok) => return Ok(self.register_infer_ok_obligations(ok)),
                             Err(_) => {
@@ -1153,7 +1155,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let sig = self
                 .at(cause, self.param_env)
                 .trace(prev_ty, new_ty)
-                .lub(a_sig, b_sig)
+                .lub(DefineOpaqueTypes::No, a_sig, b_sig)
                 .map(|ok| self.register_infer_ok_obligations(ok))?;
 
             // Reify both sides and return the reified fn pointer type.
@@ -1237,7 +1239,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
 
                 return self
-                    .commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
+                    .commit_if_ok(|_| {
+                        self.at(cause, self.param_env).lub(DefineOpaqueTypes::No, prev_ty, new_ty)
+                    })
                     .map(|ok| self.register_infer_ok_obligations(ok));
             }
         }
@@ -1248,8 +1252,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if let Some(e) = first_error {
                     Err(e)
                 } else {
-                    self.commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
-                        .map(|ok| self.register_infer_ok_obligations(ok))
+                    self.commit_if_ok(|_| {
+                        self.at(cause, self.param_env).lub(DefineOpaqueTypes::No, prev_ty, new_ty)
+                    })
+                    .map(|ok| self.register_infer_ok_obligations(ok))
                 }
             }
             Ok(ok) => {
@@ -1487,8 +1493,12 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
             assert!(expression_ty.is_unit(), "if let hack without unit type");
             fcx.at(cause, fcx.param_env)
                 // needed for tests/ui/type-alias-impl-trait/issue-65679-inst-opaque-ty-from-val-twice.rs
-                .define_opaque_types(true)
-                .eq_exp(label_expression_as_expected, expression_ty, self.merged_ty())
+                .eq_exp(
+                    DefineOpaqueTypes::Yes,
+                    label_expression_as_expected,
+                    expression_ty,
+                    self.merged_ty(),
+                )
                 .map(|infer_ok| {
                     fcx.register_infer_ok_obligations(infer_ok);
                     expression_ty
@@ -1710,12 +1720,13 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                     fcx.suggest_semicolon_at_end(cond_expr.span, &mut err);
                 }
             }
-            fcx.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
+            fcx.get_node_fn_decl(parent)
+                .map(|(fn_id, fn_decl, _, is_main)| (fn_id, fn_decl, is_main))
         } else {
             fcx.get_fn_decl(parent_id)
         };
 
-        if let Some((fn_decl, can_suggest)) = fn_decl {
+        if let Some((fn_id, fn_decl, can_suggest)) = fn_decl {
             if blk_id.is_none() {
                 pointing_at_return_type |= fcx.suggest_missing_return_type(
                     &mut err,
@@ -1723,7 +1734,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                     expected,
                     found,
                     can_suggest,
-                    fcx.tcx.hir().get_parent_item(id).into(),
+                    fn_id,
                 );
             }
             if !pointing_at_return_type {
@@ -1734,17 +1745,11 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
         let parent_id = fcx.tcx.hir().get_parent_item(id);
         let parent_item = fcx.tcx.hir().get_by_def_id(parent_id.def_id);
 
-        if let (Some(expr), Some(_), Some((fn_decl, _, _))) =
+        if let (Some(expr), Some(_), Some((fn_id, fn_decl, _, _))) =
             (expression, blk_id, fcx.get_node_fn_decl(parent_item))
         {
             fcx.suggest_missing_break_or_return_expr(
-                &mut err,
-                expr,
-                fn_decl,
-                expected,
-                found,
-                id,
-                parent_id.into(),
+                &mut err, expr, fn_decl, expected, found, id, fn_id,
             );
         }
 
@@ -1870,7 +1875,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
     }
 
     fn is_return_ty_unsized<'a>(&self, fcx: &FnCtxt<'a, 'tcx>, blk_id: hir::HirId) -> bool {
-        if let Some((fn_decl, _)) = fcx.get_fn_decl(blk_id)
+        if let Some((_, fn_decl, _)) = fcx.get_fn_decl(blk_id)
             && let hir::FnRetTy::Return(ty) = fn_decl.output
             && let ty = fcx.astconv().ast_ty_to_ty( ty)
             && let ty::Dynamic(..) = ty.kind()
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 7ba57b3b7..13442c316 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -1,6 +1,5 @@
 use crate::FnCtxt;
 use rustc_ast::util::parser::PREC_POSTFIX;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::MultiSpan;
 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
 use rustc_hir as hir;
@@ -8,19 +7,18 @@ use rustc_hir::def::CtorKind;
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{is_range_literal, Node};
-use rustc_infer::infer::InferOk;
+use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::fold::{BottomUpFolder, TypeFolder};
-use rustc_middle::ty::print::{with_forced_trimmed_paths, with_no_trimmed_paths};
-use rustc_middle::ty::relate::TypeRelation;
-use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut, TypeVisitableExt};
+use rustc_middle::ty::fold::BottomUpFolder;
+use rustc_middle::ty::print::with_no_trimmed_paths;
+use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut, TypeFoldable};
 use rustc_span::symbol::{sym, Symbol};
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Span, DUMMY_SP};
+use rustc_target::abi::FieldIdx;
 use rustc_trait_selection::infer::InferCtxtExt as _;
-use rustc_trait_selection::traits::error_reporting::method_chain::CollectAllMismatches;
 use rustc_trait_selection::traits::ObligationCause;
 
 use super::method::probe;
@@ -61,9 +59,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             || self.suggest_into(err, expr, expr_ty, expected)
             || self.suggest_floating_point_literal(err, expr, expected)
             || self.suggest_null_ptr_for_literal_zero_given_to_ptr_arg(err, expr, expected)
-            || self.note_result_coercion(err, expr, expected, expr_ty);
+            || self.suggest_coercing_result_via_try_operator(err, expr, expected, expr_ty);
+
         if !suggested {
-            self.point_at_expr_source_of_inferred_type(err, expr, expr_ty, expected, expr.span);
+            self.note_source_of_type_mismatch_constraint(
+                err,
+                expr,
+                TypeMismatchSource::Ty(expected),
+            );
         }
     }
 
@@ -83,7 +86,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.annotate_expected_due_to_let_ty(err, expr, error);
         self.emit_type_mismatch_suggestions(err, expr, expr_ty, expected, expected_ty_expr, error);
         self.note_type_is_not_clone(err, expected, expr_ty, expr);
-        self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
+        self.note_internal_mutation_in_method(err, expr, Some(expected), expr_ty);
         self.check_for_range_as_method_call(err, expr, expr_ty, expected);
         self.check_for_binding_assigned_block_without_tail_expression(err, expr, expr_ty, expected);
         self.check_wrong_return_type_due_to_generic_arg(err, expr, expr_ty);
@@ -113,7 +116,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        match self.at(cause, self.param_env).define_opaque_types(true).sup(expected, actual) {
+        match self.at(cause, self.param_env).sup(DefineOpaqueTypes::Yes, expected, actual) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
                 None
@@ -143,7 +146,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         actual: Ty<'tcx>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        match self.at(cause, self.param_env).define_opaque_types(true).eq(expected, actual) {
+        match self.at(cause, self.param_env).eq(DefineOpaqueTypes::Yes, expected, actual) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
                 None
@@ -217,37 +220,34 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         (expected, Some(err))
     }
 
-    pub fn point_at_expr_source_of_inferred_type(
+    /// Notes the point at which a variable is constrained to some type incompatible
+    /// with some expectation given by `source`.
+    pub fn note_source_of_type_mismatch_constraint(
         &self,
         err: &mut Diagnostic,
         expr: &hir::Expr<'_>,
-        found: Ty<'tcx>,
-        expected: Ty<'tcx>,
-        mismatch_span: Span,
+        source: TypeMismatchSource<'tcx>,
     ) -> bool {
-        let map = self.tcx.hir();
+        let hir = self.tcx.hir();
 
         let hir::ExprKind::Path(hir::QPath::Resolved(None, p)) = expr.kind else { return false; };
         let [hir::PathSegment { ident, args: None, .. }] = p.segments else { return false; };
-        let hir::def::Res::Local(hir_id) = p.res else { return false; };
-        let Some(hir::Node::Pat(pat)) = map.find(hir_id) else { return false; };
-        let Some(hir::Node::Local(hir::Local {
-            ty: None,
-            init: Some(init),
-            ..
-        })) = map.find_parent(pat.hir_id) else { return false; };
-        let Some(ty) = self.node_ty_opt(init.hir_id) else { return false; };
-        if ty.is_closure() || init.span.overlaps(expr.span) || pat.span.from_expansion() {
-            return false;
-        }
+        let hir::def::Res::Local(local_hir_id) = p.res else { return false; };
+        let hir::Node::Pat(pat) = hir.get(local_hir_id) else { return false; };
+        let (init_ty_hir_id, init) = match hir.get_parent(pat.hir_id) {
+            hir::Node::Local(hir::Local { ty: Some(ty), init, .. }) => (ty.hir_id, *init),
+            hir::Node::Local(hir::Local { init: Some(init), .. }) => (init.hir_id, Some(*init)),
+            _ => return false,
+        };
+        let Some(init_ty) = self.node_ty_opt(init_ty_hir_id) else { return false; };
 
         // Locate all the usages of the relevant binding.
-        struct FindExprs<'hir> {
+        struct FindExprs<'tcx> {
             hir_id: hir::HirId,
-            uses: Vec<&'hir hir::Expr<'hir>>,
+            uses: Vec<&'tcx hir::Expr<'tcx>>,
         }
-        impl<'v> Visitor<'v> for FindExprs<'v> {
-            fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
+        impl<'tcx> Visitor<'tcx> for FindExprs<'tcx> {
+            fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
                 if let hir::ExprKind::Path(hir::QPath::Resolved(None, path)) = ex.kind
                     && let hir::def::Res::Local(hir_id) = path.res
                     && hir_id == self.hir_id
@@ -258,180 +258,205 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        let mut expr_finder = FindExprs { hir_id, uses: vec![] };
-        let id = map.get_parent_item(hir_id);
-        let hir_id: hir::HirId = id.into();
-
-        let Some(node) = map.find(hir_id) else { return false; };
-        let Some(body_id) = node.body_id() else { return false; };
-        let body = map.body(body_id);
+        let mut expr_finder = FindExprs { hir_id: local_hir_id, uses: init.into_iter().collect() };
+        let body =
+            hir.body(hir.maybe_body_owned_by(self.body_id).expect("expected item to have body"));
         expr_finder.visit_expr(body.value);
-        // Hack to make equality checks on types with inference variables and regions useful.
-        let mut eraser = BottomUpFolder {
+
+        use rustc_infer::infer::type_variable::*;
+        use rustc_middle::infer::unify_key::*;
+        // Replaces all of the variables in the given type with a fresh inference variable.
+        let mut fudger = BottomUpFolder {
             tcx: self.tcx,
+            ty_op: |ty| {
+                if let ty::Infer(infer) = ty.kind() {
+                    match infer {
+                        ty::InferTy::TyVar(_) => self.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::MiscVariable,
+                            span: DUMMY_SP,
+                        }),
+                        ty::InferTy::IntVar(_) => self.next_int_var(),
+                        ty::InferTy::FloatVar(_) => self.next_float_var(),
+                        _ => bug!(),
+                    }
+                } else {
+                    ty
+                }
+            },
             lt_op: |_| self.tcx.lifetimes.re_erased,
-            ct_op: |c| c,
-            ty_op: |t| match *t.kind() {
-                ty::Infer(ty::TyVar(_)) => self.tcx.mk_ty_var(ty::TyVid::from_u32(0)),
-                ty::Infer(ty::IntVar(_)) => self.tcx.mk_int_var(ty::IntVid { index: 0 }),
-                ty::Infer(ty::FloatVar(_)) => self.tcx.mk_float_var(ty::FloatVid { index: 0 }),
-                _ => t,
+            ct_op: |ct| {
+                if let ty::ConstKind::Infer(_) = ct.kind() {
+                    self.next_const_var(
+                        ct.ty(),
+                        ConstVariableOrigin {
+                            kind: ConstVariableOriginKind::MiscVariable,
+                            span: DUMMY_SP,
+                        },
+                    )
+                } else {
+                    ct
+                }
             },
         };
-        let mut prev = eraser.fold_ty(ty);
-        let mut prev_span: Option<Span> = None;
-
-        for binding in expr_finder.uses {
-            // In every expression where the binding is referenced, we will look at that
-            // expression's type and see if it is where the incorrect found type was fully
-            // "materialized" and point at it. We will also try to provide a suggestion there.
-            if let Some(hir::Node::Expr(expr)
-            | hir::Node::Stmt(hir::Stmt {
-                kind: hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr),
-                ..
-            })) = &map.find_parent(binding.hir_id)
-                && let hir::ExprKind::MethodCall(segment, rcvr, args, _span) = expr.kind
-                && rcvr.hir_id == binding.hir_id
-                && let Some(def_id) = self.typeck_results.borrow().type_dependent_def_id(expr.hir_id)
-            {
-                // We special case methods, because they can influence inference through the
-                // call's arguments and we can provide a more explicit span.
-                let sig = self.tcx.fn_sig(def_id).subst_identity();
-                let def_self_ty = sig.input(0).skip_binder();
-                let param_tys = sig.inputs().skip_binder().iter().skip(1);
-                // If there's an arity mismatch, pointing out the call as the source of an inference
-                // can be misleading, so we skip it.
-                if param_tys.len() != args.len() {
-                    continue;
-                }
-                let rcvr_ty = self.node_ty(rcvr.hir_id);
-                // Get the evaluated type *after* calling the method call, so that the influence
-                // of the arguments can be reflected in the receiver type. The receiver
-                // expression has the type *before* theis analysis is done.
-                let ty = match self.lookup_probe_for_diagnostic(
-                    segment.ident,
-                    rcvr_ty,
-                    expr,
-                    probe::ProbeScope::TraitsInScope,
-                    None,
-                ) {
-                    Ok(pick) => eraser.fold_ty(pick.self_ty),
-                    Err(_) => rcvr_ty,
+
+        let expected_ty = match source {
+            TypeMismatchSource::Ty(expected_ty) => expected_ty,
+            // Try to deduce what the possible value of `expr` would be if the
+            // incompatible arg were compatible. For example, given `Vec<i32>`
+            // and `vec.push(1u32)`, we ideally want to deduce that the type of
+            // `vec` *should* have been `Vec<u32>`. This will allow us to then
+            // run the subsequent code with this expectation, finding out exactly
+            // when this type diverged from our expectation.
+            TypeMismatchSource::Arg { call_expr, incompatible_arg: idx } => {
+                let hir::ExprKind::MethodCall(segment, _, args, _) = call_expr.kind else {
+                    return false;
                 };
-                // Remove one layer of references to account for `&mut self` and
-                // `&self`, so that we can compare it against the binding.
-                let (ty, def_self_ty) = match (ty.kind(), def_self_ty.kind()) {
-                    (ty::Ref(_, ty, a), ty::Ref(_, self_ty, b)) if a == b => (*ty, *self_ty),
-                    _ => (ty, def_self_ty),
+                let Some(arg_ty) = self.node_ty_opt(args[idx].hir_id) else {
+                    return false;
                 };
-                let mut param_args = FxHashMap::default();
-                let mut param_expected = FxHashMap::default();
-                let mut param_found = FxHashMap::default();
-                if self.can_eq(self.param_env, ty, found) {
-                    // We only point at the first place where the found type was inferred.
-                    for (param_ty, arg) in param_tys.zip(args) {
-                        if def_self_ty.contains(*param_ty) && let ty::Param(_) = param_ty.kind() {
-                            // We found an argument that references a type parameter in `Self`,
-                            // so we assume that this is the argument that caused the found
-                            // type, which we know already because of `can_eq` above was first
-                            // inferred in this method call.
-                            let arg_ty = self.node_ty(arg.hir_id);
-                            if !arg.span.overlaps(mismatch_span) {
-                                err.span_label(
-                                    arg.span,
-                                    &format!(
-                                        "this is of type `{arg_ty}`, which causes `{ident}` to be \
-                                        inferred as `{ty}`",
-                                    ),
-                                );
-                            }
-                            param_args.insert(param_ty, (arg, arg_ty));
-                        }
-                    }
+                let possible_rcvr_ty = expr_finder.uses.iter().find_map(|binding| {
+                    let possible_rcvr_ty = self.node_ty_opt(binding.hir_id)?;
+                    // Fudge the receiver, so we can do new inference on it.
+                    let possible_rcvr_ty = possible_rcvr_ty.fold_with(&mut fudger);
+                    let method = self
+                        .lookup_method(
+                            possible_rcvr_ty,
+                            segment,
+                            DUMMY_SP,
+                            call_expr,
+                            binding,
+                            args,
+                        )
+                        .ok()?;
+                    // Unify the method signature with our incompatible arg, to
+                    // do inference in the *opposite* direction and to find out
+                    // what our ideal rcvr ty would look like.
+                    let _ = self
+                        .at(&ObligationCause::dummy(), self.param_env)
+                        .eq(DefineOpaqueTypes::No, method.sig.inputs()[idx + 1], arg_ty)
+                        .ok()?;
+                    self.select_obligations_where_possible(|errs| {
+                        // Yeet the errors, we're already reporting errors.
+                        errs.clear();
+                    });
+                    Some(self.resolve_vars_if_possible(possible_rcvr_ty))
+                });
+                if let Some(rcvr_ty) = possible_rcvr_ty {
+                    rcvr_ty
+                } else {
+                    return false;
                 }
+            }
+        };
 
-                // Here we find, for a type param `T`, the type that `T` is in the current
-                // method call *and* in the original expected type. That way, we can see if we
-                // can give any structured suggestion for the function argument.
-                let mut c = CollectAllMismatches {
-                    infcx: &self.infcx,
-                    param_env: self.param_env,
-                    errors: vec![],
+        // If our expected_ty does not equal init_ty, then it *began* as incompatible.
+        // No need to note in this case...
+        if !self.can_eq(self.param_env, expected_ty, init_ty.fold_with(&mut fudger)) {
+            return false;
+        }
+
+        for window in expr_finder.uses.windows(2) {
+            // Bindings always update their recorded type after the fact, so we
+            // need to look at the *following* usage's type to see when the
+            // binding became incompatible.
+            let [binding, next_usage] = *window else { continue; };
+
+            // Don't go past the binding (always gonna be a nonsense label if so)
+            if binding.hir_id == expr.hir_id {
+                break;
+            }
+
+            let Some(next_use_ty) = self.node_ty_opt(next_usage.hir_id) else { continue; };
+
+            // If the type is not constrained in a way making it not possible to
+            // equate with `expected_ty` by this point, skip.
+            if self.can_eq(self.param_env, expected_ty, next_use_ty.fold_with(&mut fudger)) {
+                continue;
+            }
+
+            if let hir::Node::Expr(parent_expr) = hir.get_parent(binding.hir_id)
+                && let hir::ExprKind::MethodCall(segment, rcvr, args, _) = parent_expr.kind
+                && rcvr.hir_id == binding.hir_id
+            {
+                // If our binding became incompatible while it was a receiver
+                // to a method call, we may be able to make a better guess to
+                // the source of a type mismatch.
+                let Some(rcvr_ty) = self.node_ty_opt(rcvr.hir_id) else { continue; };
+                let rcvr_ty = rcvr_ty.fold_with(&mut fudger);
+                let Ok(method) =
+                    self.lookup_method(rcvr_ty, segment, DUMMY_SP, parent_expr, rcvr, args)
+                else {
+                    continue;
                 };
-                let _ = c.relate(def_self_ty, ty);
-                for error in c.errors {
-                    if let TypeError::Sorts(error) = error {
-                        param_found.insert(error.expected, error.found);
-                    }
-                }
-                c.errors = vec![];
-                let _ = c.relate(def_self_ty, expected);
-                for error in c.errors {
-                    if let TypeError::Sorts(error) = error {
-                        param_expected.insert(error.expected, error.found);
-                    }
-                }
-                for (param, (arg, arg_ty)) in param_args.iter() {
-                    let Some(expected) = param_expected.get(param) else { continue; };
-                    let Some(found) = param_found.get(param) else { continue; };
-                    if !self.can_eq(self.param_env, *arg_ty, *found) { continue; }
-                    self.emit_coerce_suggestions(err, arg, *found, *expected, None, None);
-                }
 
-                let ty = eraser.fold_ty(ty);
-                if ty.references_error() {
-                    break;
-                }
-                if ty != prev
-                    && param_args.is_empty()
-                    && self.can_eq(self.param_env, ty, found)
+                let ideal_rcvr_ty = rcvr_ty.fold_with(&mut fudger);
+                let ideal_method = self
+                    .lookup_method(ideal_rcvr_ty, segment, DUMMY_SP, parent_expr, rcvr, args)
+                    .ok()
+                    .and_then(|method| {
+                        let _ = self.at(&ObligationCause::dummy(), self.param_env)
+                            .eq(DefineOpaqueTypes::No, ideal_rcvr_ty, expected_ty)
+                            .ok()?;
+                        Some(method)
+                    });
+
+                // Find what argument caused our rcvr to become incompatible
+                // with the expected ty.
+                for (idx, (expected_arg_ty, arg_expr)) in
+                    std::iter::zip(&method.sig.inputs()[1..], args).enumerate()
                 {
-                    // We only point at the first place where the found type was inferred.
-                    if !segment.ident.span.overlaps(mismatch_span) {
+                    let Some(arg_ty) = self.node_ty_opt(arg_expr.hir_id) else { continue; };
+                    let arg_ty = arg_ty.fold_with(&mut fudger);
+                    let _ = self.try_coerce(
+                        arg_expr,
+                        arg_ty,
+                        *expected_arg_ty,
+                        AllowTwoPhase::No,
+                        None,
+                    );
+                    self.select_obligations_where_possible(|errs| {
+                        // Yeet the errors, we're already reporting errors.
+                        errs.clear();
+                    });
+                    // If our rcvr, after inference due to unifying the signature
+                    // with the expected argument type, is still compatible with
+                    // the rcvr, then it must've not been the source of blame.
+                    if self.can_eq(self.param_env, rcvr_ty, expected_ty) {
+                        continue;
+                    }
+                    err.span_label(arg_expr.span, format!("this argument has type `{arg_ty}`..."));
                     err.span_label(
-                        segment.ident.span,
-                        with_forced_trimmed_paths!(format!(
-                            "here the type of `{ident}` is inferred to be `{ty}`",
-                        )),
-                    );}
-                    break;
-                } else if !param_args.is_empty() {
-                    break;
-                }
-                prev = ty;
-            } else {
-                let ty = eraser.fold_ty(self.node_ty(binding.hir_id));
-                if ty.references_error() {
-                    break;
-                }
-                if ty != prev
-                    && let Some(span) = prev_span
-                    && self.can_eq(self.param_env, ty, found)
-                {
-                    // We only point at the first place where the found type was inferred.
-                    // We use the *previous* span because if the type is known *here* it means
-                    // it was *evaluated earlier*. We don't do this for method calls because we
-                    // evaluate the method's self type eagerly, but not in any other case.
-                    if !span.overlaps(mismatch_span) {
-                        err.span_label(
-                            span,
-                            with_forced_trimmed_paths!(format!(
-                                "here the type of `{ident}` is inferred to be `{ty}`",
-                            )),
+                        binding.span,
+                        format!("... which causes `{ident}` to have type `{next_use_ty}`"),
+                    );
+                    // Using our "ideal" method signature, suggest a fix to this
+                    // blame arg, if possible. Don't do this if we're coming from
+                    // arg mismatch code, because we'll possibly suggest a mutually
+                    // incompatible fix at the original mismatch site.
+                    if matches!(source, TypeMismatchSource::Ty(_))
+                        && let Some(ideal_method) = ideal_method
+                    {
+                        self.emit_type_mismatch_suggestions(
+                            err,
+                            arg_expr,
+                            arg_ty,
+                            self.resolve_vars_if_possible(ideal_method.sig.inputs()[idx + 1]),
+                            None,
+                            None,
                         );
                     }
-                    break;
+                    return true;
                 }
-                prev = ty;
-            }
-            if binding.hir_id == expr.hir_id {
-                // Do not look at expressions that come after the expression we were originally
-                // evaluating and had a type error.
-                break;
             }
-            prev_span = Some(binding.span);
+            err.span_label(
+                binding.span,
+                format!("here the type of `{ident}` is inferred to be `{next_use_ty}`"),
+            );
+            return true;
         }
-        true
+
+        // We must've not found something that constrained the expr.
+        false
     }
 
     fn annotate_expected_due_to_let_ty(
@@ -707,7 +732,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
     }
 
-    pub(crate) fn note_result_coercion(
+    pub(crate) fn suggest_coercing_result_via_try_operator(
         &self,
         err: &mut Diagnostic,
         expr: &hir::Expr<'tcx>,
@@ -850,7 +875,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     variant.fields.len() == 1
                 })
                 .filter_map(|variant| {
-                    let sole_field = &variant.fields[0];
+                    let sole_field = &variant.fields[FieldIdx::from_u32(0)];
 
                     let field_is_local = sole_field.did.is_local();
                     let field_is_accessible =
@@ -1480,14 +1505,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                     // For this suggestion to make sense, the type would need to be `Copy`,
                     // or we have to be moving out of a `Box<T>`
-                    if self.type_is_copy_modulo_regions(self.param_env, expected, sp)
+                    if self.type_is_copy_modulo_regions(self.param_env, expected)
                         // FIXME(compiler-errors): We can actually do this if the checked_ty is
                         // `steps` layers of boxes, not just one, but this is easier and most likely.
                         || (checked_ty.is_box() && steps == 1)
                     {
                         let deref_kind = if checked_ty.is_box() {
                             "unboxing the value"
-                        } else if checked_ty.is_region_ptr() {
+                        } else if checked_ty.is_ref() {
                             "dereferencing the borrow"
                         } else {
                             "dereferencing the type"
@@ -2093,3 +2118,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 }
+
+pub enum TypeMismatchSource<'tcx> {
+    /// Expected the binding to have the given type, but it was found to have
+    /// a different type. Find out when that type first became incompatible.
+    Ty(Ty<'tcx>),
+    /// When we fail during method argument checking, try to find out if a previous
+    /// expression has constrained the method's receiver in a way that makes the
+    /// argument's type incompatible.
+    Arg { call_expr: &'tcx hir::Expr<'tcx>, incompatible_arg: usize },
+}
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 7fc4ccb04..6ffa0134f 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -36,6 +36,7 @@ use rustc_hir_analysis::astconv::AstConv as _;
 use rustc_hir_analysis::check::ty_kind_suggestion;
 use rustc_infer::infer;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::infer::InferOk;
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability;
@@ -49,6 +50,7 @@ use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::source_map::{Span, Spanned};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
+use rustc_target::abi::FieldIdx;
 use rustc_target::spec::abi::Abi::RustIntrinsic;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::{self, ObligationCauseCode};
@@ -118,7 +120,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ty
     }
 
-    pub(super) fn check_expr_coercable_to_type(
+    pub(super) fn check_expr_coercible_to_type(
         &self,
         expr: &'tcx hir::Expr<'tcx>,
         expected: Ty<'tcx>,
@@ -230,7 +232,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ty = ensure_sufficient_stack(|| match &expr.kind {
             hir::ExprKind::Path(
-                qpath @ hir::QPath::Resolved(..) | qpath @ hir::QPath::TypeRelative(..),
+                qpath @ (hir::QPath::Resolved(..) | hir::QPath::TypeRelative(..)),
             ) => self.check_expr_path(qpath, expr, args),
             _ => self.check_expr_kind(expr, expected),
         });
@@ -283,7 +285,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let tcx = self.tcx;
         match expr.kind {
-            ExprKind::Box(subexpr) => self.check_expr_box(subexpr, expected),
             ExprKind::Lit(ref lit) => self.check_lit(&lit, expected),
             ExprKind::Binary(op, lhs, rhs) => self.check_binop(expr, op, lhs, rhs, expected),
             ExprKind::Assign(lhs, rhs, span) => {
@@ -358,16 +359,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    fn check_expr_box(&self, expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>) -> Ty<'tcx> {
-        let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| match ty.kind() {
-            ty::Adt(def, _) if def.is_box() => Expectation::rvalue_hint(self, ty.boxed_ty()),
-            _ => NoExpectation,
-        });
-        let referent_ty = self.check_expr_with_expectation(expr, expected_inner);
-        self.require_type_is_sized(referent_ty, expr.span, traits::SizedBoxType);
-        self.tcx.mk_box(referent_ty)
-    }
-
     fn check_expr_unary(
         &self,
         unop: hir::UnOp,
@@ -798,7 +789,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.ret_coercion_span.set(Some(expr.span));
             }
             let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
-            if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
+            if let Some((_, fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
                 coercion.coerce_forced_unit(
                     self,
                     &cause,
@@ -1137,7 +1128,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         };
 
-        // This is (basically) inlined `check_expr_coercable_to_type`, but we want
+        // This is (basically) inlined `check_expr_coercible_to_type`, but we want
         // to suggest an additional fixup here in `suggest_deref_binop`.
         let rhs_ty = self.check_expr_with_hint(&rhs, lhs_ty);
         if let (_, Some(mut diag)) =
@@ -1410,7 +1401,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let (element_ty, t) = match uty {
             Some(uty) => {
-                self.check_expr_coercable_to_type(&element, uty, None);
+                self.check_expr_coercible_to_type(&element, uty, None);
                 (uty, uty)
             }
             None => {
@@ -1487,7 +1478,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
             Some(fs) if i < fs.len() => {
                 let ety = fs[i];
-                self.check_expr_coercable_to_type(&e, ety, None);
+                self.check_expr_coercible_to_type(&e, ety, None);
                 ety
             }
             _ => self.check_expr_with_expectation(&e, NoExpectation),
@@ -1571,8 +1562,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let mut remaining_fields = variant
             .fields
-            .iter()
-            .enumerate()
+            .iter_enumerated()
             .map(|(i, field)| (field.ident(tcx).normalize_to_macros_2_0(), (i, field)))
             .collect::<FxHashMap<_, _>>();
 
@@ -1683,7 +1673,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             if let Some(_) = remaining_fields.remove(&ident) {
                                 let target_ty = self.field_ty(base_expr.span, f, substs);
                                 let cause = self.misc(base_expr.span);
-                                match self.at(&cause, self.param_env).sup(target_ty, fru_ty) {
+                                match self.at(&cause, self.param_env).sup(
+                                    DefineOpaqueTypes::No,
+                                    target_ty,
+                                    fru_ty,
+                                ) {
                                     Ok(InferOk { obligations, value: () }) => {
                                         self.register_predicates(obligations)
                                     }
@@ -1821,7 +1815,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         adt_ty: Ty<'tcx>,
         span: Span,
-        remaining_fields: FxHashMap<Ident, (usize, &ty::FieldDef)>,
+        remaining_fields: FxHashMap<Ident, (FieldIdx, &ty::FieldDef)>,
         variant: &'tcx ty::VariantDef,
         ast_fields: &'tcx [hir::ExprField<'tcx>],
         substs: SubstsRef<'tcx>,
@@ -2215,11 +2209,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let (ident, def_scope) =
                         self.tcx.adjust_ident_and_get_scope(field, base_def.did(), body_hir_id);
                     let fields = &base_def.non_enum_variant().fields;
-                    if let Some(index) = fields
-                        .iter()
-                        .position(|f| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
+                    if let Some((index, field)) = fields
+                        .iter_enumerated()
+                        .find(|(_, f)| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
                     {
-                        let field = &fields[index];
                         let field_ty = self.field_ty(expr.span, field, substs);
                         // Save the index of all fields regardless of their visibility in case
                         // of error recovery.
@@ -2236,15 +2229,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }
                 ty::Tuple(tys) => {
-                    let fstr = field.as_str();
-                    if let Ok(index) = fstr.parse::<usize>() {
-                        if fstr == index.to_string() {
+                    if let Ok(index) = field.as_str().parse::<usize>() {
+                        if field.name == sym::integer(index) {
                             if let Some(&field_ty) = tys.get(index) {
                                 let adjustments = self.adjust_steps(&autoderef);
                                 self.apply_adjustments(base, adjustments);
                                 self.register_predicates(autoderef.into_obligations());
 
-                                self.write_field_index(expr.hir_id, index);
+                                self.write_field_index(expr.hir_id, FieldIdx::from_usize(index));
                                 return field_ty;
                             }
                         }
@@ -2818,23 +2810,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         "cannot index into a value of type `{base_t}`",
                     );
                     // Try to give some advice about indexing tuples.
-                    if let ty::Tuple(..) = base_t.kind() {
+                    if let ty::Tuple(types) = base_t.kind() {
                         let mut needs_note = true;
                         // If the index is an integer, we can show the actual
                         // fixed expression:
-                        if let ExprKind::Lit(ref lit) = idx.kind {
-                            if let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node {
-                                let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
-                                if let Ok(snip) = snip {
-                                    err.span_suggestion(
-                                        expr.span,
-                                        "to access tuple elements, use",
-                                        format!("{snip}.{i}"),
-                                        Applicability::MachineApplicable,
-                                    );
-                                    needs_note = false;
-                                }
+                        if let ExprKind::Lit(ref lit) = idx.kind
+                            && let ast::LitKind::Int(i, ast::LitIntType::Unsuffixed) = lit.node
+                            && i < types.len().try_into().expect("expected tuple index to be < usize length")
+                        {
+                            let snip = self.tcx.sess.source_map().span_to_snippet(base.span);
+                            if let Ok(snip) = snip {
+                                err.span_suggestion(
+                                    expr.span,
+                                    "to access tuple elements, use",
+                                    format!("{snip}.{i}"),
+                                    Applicability::MachineApplicable,
+                                );
+                                needs_note = false;
                             }
+                        } else if let ExprKind::Path(..) = idx.peel_borrows().kind {
+                            err.span_label(idx.span, "cannot access tuple elements at a variable index");
                         }
                         if needs_note {
                             err.help(
@@ -2874,7 +2869,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         match self.resume_yield_tys {
             Some((resume_ty, yield_ty)) => {
-                self.check_expr_coercable_to_type(&value, yield_ty, None);
+                self.check_expr_coercible_to_type(&value, yield_ty, None);
 
                 resume_ty
             }
@@ -2883,7 +2878,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // information. Hence, we check the source of the yield expression here and check its
             // value's type against `()` (this check should always hold).
             None if src.is_await() => {
-                self.check_expr_coercable_to_type(&value, self.tcx.mk_unit(), None);
+                self.check_expr_coercible_to_type(&value, self.tcx.mk_unit(), None);
                 self.tcx.mk_unit()
             }
             _ => {
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
index b9a058d6b..ee1c6fbfd 100644
--- a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -14,12 +14,11 @@ use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::PatKind;
-use rustc_index::vec::Idx;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::hir::place::ProjectionKind;
 use rustc_middle::mir::FakeReadCause;
 use rustc_middle::ty::{self, adjustment, AdtKind, Ty, TyCtxt};
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::FIRST_VARIANT;
 use ty::BorrowKind::ImmBorrow;
 
 use crate::mem_categorization as mc;
@@ -356,10 +355,6 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 self.walk_captures(closure);
             }
 
-            hir::ExprKind::Box(ref base) => {
-                self.consume_expr(base);
-            }
-
             hir::ExprKind::Yield(value, _) => {
                 self.consume_expr(value);
             }
@@ -544,7 +539,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
         match with_place.place.ty().kind() {
             ty::Adt(adt, substs) if adt.is_struct() => {
                 // Consume those fields of the with expression that are needed.
-                for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
+                for (f_index, with_field) in adt.non_enum_variant().fields.iter_enumerated() {
                     let is_mentioned = fields
                         .iter()
                         .any(|f| self.mc.typeck_results.opt_field_index(f.hir_id) == Some(f_index));
@@ -553,7 +548,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                             &*with_expr,
                             with_place.clone(),
                             with_field.ty(self.tcx(), substs),
-                            ProjectionKind::Field(f_index as u32, VariantIdx::new(0)),
+                            ProjectionKind::Field(f_index, FIRST_VARIANT),
                         );
                         self.delegate_consume(&field_place, field_place.hir_id);
                     }
@@ -564,7 +559,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 // struct; however, when EUV is run during typeck, it
                 // may not. This will generate an error earlier in typeck,
                 // so we can just ignore it.
-                if !self.tcx().sess.has_errors().is_some() {
+                if self.tcx().sess.has_errors().is_none() {
                     span_bug!(with_expr.span, "with expression doesn't evaluate to a struct");
                 }
             }
@@ -871,10 +866,7 @@ fn copy_or_move<'a, 'tcx>(
     mc: &mc::MemCategorizationContext<'a, 'tcx>,
     place_with_id: &PlaceWithHirId<'tcx>,
 ) -> ConsumeMode {
-    if !mc.type_is_copy_modulo_regions(
-        place_with_id.place.ty(),
-        mc.tcx().hir().span(place_with_id.hir_id),
-    ) {
+    if !mc.type_is_copy_modulo_regions(place_with_id.place.ty()) {
         ConsumeMode::Move
     } else {
         ConsumeMode::Copy
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 60e55c7b0..f736f7a96 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -19,13 +19,13 @@ use rustc_hir_analysis::astconv::{
 };
 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
-use rustc_infer::infer::InferResult;
+use rustc_infer::infer::{DefineOpaqueTypes, InferResult};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{
-    self, AdtKind, CanonicalUserType, DefIdTree, GenericParamDefKind, Ty, TyCtxt, UserType,
+    self, AdtKind, CanonicalUserType, GenericParamDefKind, Ty, TyCtxt, UserType,
 };
 use rustc_middle::ty::{GenericArgKind, SubstsRef, UserSelfTy, UserSubsts};
 use rustc_session::lint;
@@ -33,6 +33,7 @@ use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::DesugaringKind;
 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};
 
@@ -147,7 +148,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
+    pub fn write_field_index(&self, hir_id: hir::HirId, index: FieldIdx) {
         self.typeck_results.borrow_mut().field_indices_mut().insert(hir_id, index);
     }
 
@@ -301,16 +302,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         def_id: DefId,
         substs: SubstsRef<'tcx>,
-    ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
+    ) -> ty::InstantiatedPredicates<'tcx> {
         let bounds = self.tcx.predicates_of(def_id);
-        let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
         let result = bounds.instantiate(self.tcx, substs);
         let result = self.normalize(span, result);
-        debug!(
-            "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
-            bounds, substs, result, spans,
-        );
-        (result, spans)
+        debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}", bounds, substs, result);
+        result
     }
 
     pub(in super::super) fn normalize<T>(&self, span: Span, value: T) -> T
@@ -562,7 +559,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let span = self.tcx.hir().body(body_id).value.span;
             let ok = self
                 .at(&self.misc(span), self.param_env)
-                .eq(interior, witness)
+                .eq(DefineOpaqueTypes::No, interior, witness)
                 .expect("Failed to unify generator interior type");
             let mut obligations = ok.obligations;
 
@@ -581,11 +578,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     #[instrument(skip(self), level = "debug")]
     pub(in super::super) fn report_ambiguity_errors(&self) {
-        let mut errors = self.fulfillment_cx.borrow_mut().collect_remaining_errors();
+        let mut errors = self.fulfillment_cx.borrow_mut().collect_remaining_errors(self);
 
         if !errors.is_empty() {
             self.adjust_fulfillment_errors_for_expr_obligation(&mut errors);
-            self.err_ctxt().report_fulfillment_errors(&errors, self.inh.body_id);
+            self.err_ctxt().report_fulfillment_errors(&errors);
         }
     }
 
@@ -598,7 +595,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if !result.is_empty() {
             mutate_fulfillment_errors(&mut result);
             self.adjust_fulfillment_errors_for_expr_obligation(&mut result);
-            self.err_ctxt().report_fulfillment_errors(&result, self.inh.body_id);
+            self.err_ctxt().report_fulfillment_errors(&result);
         }
     }
 
@@ -670,7 +667,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 | ty::PredicateKind::Clause(ty::Clause::TypeOutlives(..))
                 | ty::PredicateKind::WellFormed(..)
                 | ty::PredicateKind::ObjectSafe(..)
-                | ty::PredicateKind::AliasEq(..)
+                | ty::PredicateKind::AliasRelate(..)
                 | ty::PredicateKind::ConstEvaluatable(..)
                 | ty::PredicateKind::ConstEquate(..)
                 // N.B., this predicate is created by breaking down a
@@ -902,56 +899,74 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
-    /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
+    /// Given a function `Node`, return its  `HirId` and `FnDecl` if it exists. Given a closure
+    /// that is the child of a function, return that function's `HirId` and `FnDecl` instead.
+    /// This may seem confusing at first, but this is used in diagnostics for `async fn`,
+    /// for example, where most of the type checking actually happens within a nested closure,
+    /// but we often want access to the parent function's signature.
+    ///
+    /// Otherwise, return false.
     pub(in super::super) fn get_node_fn_decl(
         &self,
         node: Node<'tcx>,
-    ) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident, bool)> {
+    ) -> Option<(hir::HirId, &'tcx hir::FnDecl<'tcx>, Ident, bool)> {
         match node {
-            Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
+            Node::Item(&hir::Item {
+                ident,
+                kind: hir::ItemKind::Fn(ref sig, ..),
+                owner_id,
+                ..
+            }) => {
                 // This is less than ideal, it will not suggest a return type span on any
                 // method called `main`, regardless of whether it is actually the entry point,
                 // but it will still present it as the reason for the expected type.
-                Some((&sig.decl, ident, ident.name != sym::main))
+                Some((
+                    hir::HirId::make_owner(owner_id.def_id),
+                    &sig.decl,
+                    ident,
+                    ident.name != sym::main,
+                ))
             }
             Node::TraitItem(&hir::TraitItem {
                 ident,
                 kind: hir::TraitItemKind::Fn(ref sig, ..),
+                owner_id,
                 ..
-            }) => Some((&sig.decl, ident, true)),
+            }) => Some((hir::HirId::make_owner(owner_id.def_id), &sig.decl, ident, true)),
             Node::ImplItem(&hir::ImplItem {
                 ident,
                 kind: hir::ImplItemKind::Fn(ref sig, ..),
+                owner_id,
                 ..
-            }) => Some((&sig.decl, ident, false)),
-            Node::Expr(&hir::Expr {
-                hir_id,
-                kind: hir::ExprKind::Closure(..),
-                ..
-            }) if let Some(Node::Expr(&hir::Expr {
-                hir_id,
-                kind: hir::ExprKind::Call(..),
-                ..
-            })) = self.tcx.hir().find_parent(hir_id) &&
-            let Some(Node::Item(&hir::Item {
+            }) => Some((hir::HirId::make_owner(owner_id.def_id), &sig.decl, ident, false)),
+            Node::Expr(&hir::Expr { hir_id, kind: hir::ExprKind::Closure(..), .. })
+                if let Some(Node::Item(&hir::Item {
+                    ident,
+                    kind: hir::ItemKind::Fn(ref sig, ..),
+                    owner_id,
+                    ..
+                })) = self.tcx.hir().find_parent(hir_id) => Some((
+                hir::HirId::make_owner(owner_id.def_id),
+                &sig.decl,
                 ident,
-                kind: hir::ItemKind::Fn(ref sig, ..),
-                ..
-            })) = self.tcx.hir().find_parent(hir_id) => {
-                Some((&sig.decl, ident, ident.name != sym::main))
-            },
+                ident.name != sym::main,
+            )),
             _ => None,
         }
     }
 
-    /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
+    /// Given a `HirId`, return the `HirId` of the enclosing function, its `FnDecl`, and whether a
     /// suggestion can be made, `None` otherwise.
-    pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
+    pub fn get_fn_decl(
+        &self,
+        blk_id: hir::HirId,
+    ) -> Option<(hir::HirId, &'tcx hir::FnDecl<'tcx>, bool)> {
         // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
         // `while` before reaching it, as block tail returns are not available in them.
         self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
             let parent = self.tcx.hir().get(blk_id);
-            self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
+            self.get_node_fn_decl(parent)
+                .map(|(fn_id, fn_decl, _, is_main)| (fn_id, fn_decl, is_main))
         })
     }
 
@@ -959,44 +974,75 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         err: &mut Diagnostic,
         expr: &hir::Expr<'_>,
-        expected: Ty<'tcx>,
+        expected: Option<Ty<'tcx>>,
         found: Ty<'tcx>,
     ) {
         if found != self.tcx.types.unit {
             return;
         }
-        if let ExprKind::MethodCall(path_segment, rcvr, ..) = expr.kind {
-            if self
-                .typeck_results
+
+        let ExprKind::MethodCall(path_segment, rcvr, ..) = expr.kind else {
+            return;
+        };
+
+        let rcvr_has_the_expected_type = self
+            .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);
+
+        let prev_call_mutates_and_returns_unit = || {
+            self.typeck_results
                 .borrow()
-                .expr_ty_adjusted_opt(rcvr)
-                .map_or(true, |ty| expected.peel_refs() != ty.peel_refs())
-            {
-                return;
-            }
-            let mut sp = MultiSpan::from_span(path_segment.ident.span);
-            sp.push_span_label(
-                path_segment.ident.span,
-                format!(
-                    "this call modifies {} in-place",
-                    match rcvr.kind {
-                        ExprKind::Path(QPath::Resolved(
-                            None,
-                            hir::Path { segments: [segment], .. },
-                        )) => format!("`{}`", segment.ident),
-                        _ => "its receiver".to_string(),
-                    }
-                ),
-            );
+                .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)| {
+                    output.is_unit()
+                        && inputs
+                            .get(0)
+                            .and_then(|self_ty| self_ty.ref_mutability())
+                            .map_or(false, rustc_ast::Mutability::is_mut)
+                })
+                .unwrap_or(false)
+        };
+
+        if !(rcvr_has_the_expected_type || prev_call_mutates_and_returns_unit()) {
+            return;
+        }
+
+        let mut sp = MultiSpan::from_span(path_segment.ident.span);
+        sp.push_span_label(
+            path_segment.ident.span,
+            format!(
+                "this call modifies {} in-place",
+                match rcvr.kind {
+                    ExprKind::Path(QPath::Resolved(
+                        None,
+                        hir::Path { segments: [segment], .. },
+                    )) => format!("`{}`", segment.ident),
+                    _ => "its receiver".to_string(),
+                }
+            ),
+        );
+
+        let modifies_rcvr_note =
+            format!("method `{}` modifies its receiver in-place", path_segment.ident);
+        if rcvr_has_the_expected_type {
             sp.push_span_label(
                 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));
+        } else if let ExprKind::MethodCall(..) = rcvr.kind {
             err.span_note(
                 sp,
-                &format!("method `{}` modifies its receiver in-place", path_segment.ident),
+                modifies_rcvr_note.clone() + ", it is not meant to be used in method chains.",
             );
-            err.note(&format!("...instead of the `()` output of method `{}`", path_segment.ident));
+        } else {
+            err.span_note(sp, &modifies_rcvr_note);
         }
     }
 
@@ -1319,7 +1365,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // This also occurs for an enum variant on a type alias.
             let impl_ty = self.normalize(span, tcx.type_of(impl_def_id).subst(tcx, substs));
             let self_ty = self.normalize(span, self_ty);
-            match self.at(&self.misc(span), self.param_env).eq(impl_ty, self_ty) {
+            match self.at(&self.misc(span), self.param_env).eq(
+                DefineOpaqueTypes::No,
+                impl_ty,
+                self_ty,
+            ) {
                 Ok(ok) => self.register_infer_ok_obligations(ok),
                 Err(_) => {
                     self.tcx.sess.delay_span_bug(
@@ -1367,41 +1417,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         let param_env = self.param_env;
 
-        let remap = match self.tcx.def_kind(def_id) {
-            // Associated consts have `Self: ~const Trait` bounds that should be satisfiable when
-            // `Self: Trait` is satisfied because it does not matter whether the impl is `const`.
-            // Therefore we have to remap the param env here to be non-const.
-            hir::def::DefKind::AssocConst => true,
-            hir::def::DefKind::AssocFn
-                if self.tcx.def_kind(self.tcx.parent(def_id)) == hir::def::DefKind::Trait =>
-            {
-                // N.B.: All callsites to this function involve checking a path expression.
-                //
-                // When instantiating a trait method as a function item, it does not actually matter whether
-                // the trait is `const` or not, or whether `where T: ~const Tr` needs to be satisfied as
-                // `const`. If we were to introduce instantiating trait methods as `const fn`s, we would
-                // check that after this, either via a bound `where F: ~const FnOnce` or when coercing to a
-                // `const fn` pointer.
-                //
-                // FIXME(fee1-dead) FIXME(const_trait_impl): update this doc when trait methods can satisfy
-                // `~const FnOnce` or can be coerced to `const fn` pointer.
-                true
-            }
-            _ => false,
-        };
-        let (bounds, _) = self.instantiate_bounds(span, def_id, &substs);
+        let bounds = self.instantiate_bounds(span, def_id, &substs);
 
-        for mut obligation in traits::predicates_for_generics(
+        for obligation in traits::predicates_for_generics(
             |idx, predicate_span| {
                 traits::ObligationCause::new(span, self.body_id, code(idx, predicate_span))
             },
             param_env,
             bounds,
         ) {
-            if remap {
-                obligation = obligation.without_const(self.tcx);
-            }
-            self.register_predicate(obligation);
+            // N.B. We are remapping all predicates to non-const since we don't know if we just
+            // want them as function pointers or we are calling them from a const-context. The
+            // actual checking will occur in `rustc_const_eval::transform::check_consts`.
+            self.register_predicate(obligation.without_const(self.tcx));
         }
     }
 
@@ -1415,7 +1443,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             let e = self.tainted_by_errors().unwrap_or_else(|| {
                 self.err_ctxt()
-                    .emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282, true)
+                    .emit_inference_failure_err(self.body_id, sp, ty.into(), E0282, true)
                     .emit()
             });
             let err = self.tcx.ty_error(e);
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 b09886fe3..f879ccbb3 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
@@ -3,10 +3,8 @@ use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
 use rustc_infer::traits::ObligationCauseCode;
-use rustc_middle::ty::{
-    self, DefIdTree, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
-};
-use rustc_span::{self, Span};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
+use rustc_span::{self, symbol::kw, Span};
 use rustc_trait_selection::traits;
 
 use std::ops::ControlFlow;
@@ -27,17 +25,28 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let generics = self.tcx.generics_of(def_id);
         let predicate_substs = match unsubstituted_pred.kind().skip_binder() {
-            ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs,
-            ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => pred.projection_ty.substs,
-            _ => ty::List::empty(),
+            ty::PredicateKind::Clause(ty::Clause::Trait(pred)) => pred.trait_ref.substs.to_vec(),
+            ty::PredicateKind::Clause(ty::Clause::Projection(pred)) => {
+                pred.projection_ty.substs.to_vec()
+            }
+            ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(arg, ty)) => {
+                vec![ty.into(), arg.into()]
+            }
+            ty::PredicateKind::ConstEvaluatable(e) => vec![e.into()],
+            _ => return false,
         };
 
-        let find_param_matching = |matches: &dyn Fn(&ty::ParamTy) -> bool| {
-            predicate_substs.types().find_map(|ty| {
-                ty.walk().find_map(|arg| {
+        let find_param_matching = |matches: &dyn Fn(ty::ParamTerm) -> bool| {
+            predicate_substs.iter().find_map(|arg| {
+                arg.walk().find_map(|arg| {
                     if let ty::GenericArgKind::Type(ty) = arg.unpack()
-                        && let ty::Param(param_ty) = ty.kind()
-                        && matches(param_ty)
+                        && let ty::Param(param_ty) = *ty.kind()
+                        && matches(ty::ParamTerm::Ty(param_ty))
+                    {
+                        Some(arg)
+                    } else if let ty::GenericArgKind::Const(ct) = arg.unpack()
+                        && let ty::ConstKind::Param(param_ct) = ct.kind()
+                        && matches(ty::ParamTerm::Const(param_ct))
                     {
                         Some(arg)
                     } else {
@@ -49,26 +58,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Prefer generics that are local to the fn item, since these are likely
         // to be the cause of the unsatisfied predicate.
-        let mut param_to_point_at = find_param_matching(&|param_ty| {
-            self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) == def_id
+        let mut param_to_point_at = find_param_matching(&|param_term| {
+            self.tcx.parent(generics.param_at(param_term.index(), self.tcx).def_id) == def_id
         });
         // Fall back to generic that isn't local to the fn item. This will come
         // from a trait or impl, for example.
-        let mut fallback_param_to_point_at = find_param_matching(&|param_ty| {
-            self.tcx.parent(generics.type_param(param_ty, self.tcx).def_id) != def_id
-                && param_ty.name != rustc_span::symbol::kw::SelfUpper
+        let mut fallback_param_to_point_at = find_param_matching(&|param_term| {
+            self.tcx.parent(generics.param_at(param_term.index(), self.tcx).def_id) != def_id
+                && !matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper)
         });
         // Finally, the `Self` parameter is possibly the reason that the predicate
         // is unsatisfied. This is less likely to be true for methods, because
         // method probe means that we already kinda check that the predicates due
         // to the `Self` type are true.
-        let mut self_param_to_point_at =
-            find_param_matching(&|param_ty| param_ty.name == rustc_span::symbol::kw::SelfUpper);
+        let mut self_param_to_point_at = find_param_matching(
+            &|param_term| matches!(param_term, ty::ParamTerm::Ty(ty) if ty.name == kw::SelfUpper),
+        );
 
         // Finally, for ambiguity-related errors, we actually want to look
         // for a parameter that is the source of the inference type left
         // over in this predicate.
-        if let traits::FulfillmentErrorCode::CodeAmbiguity = error.code {
+        if let traits::FulfillmentErrorCode::CodeAmbiguity { .. } = error.code {
             fallback_param_to_point_at = None;
             self_param_to_point_at = None;
             param_to_point_at =
@@ -227,15 +237,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id));
         let Some((index, _)) = own_substs
             .iter()
-            .filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
             .enumerate()
             .find(|(_, arg)| **arg == param_to_point_at) else { return false };
         let Some(arg) = segment
             .args()
             .args
-            .iter()
-            .filter(|arg| matches!(arg, hir::GenericArg::Type(_)))
-            .nth(index) else { return false; };
+            .get(index) else { return false; };
         error.obligation.cause.span = arg
             .span()
             .find_ancestor_in_same_ctxt(error.obligation.cause.span)
@@ -302,7 +309,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .iter()
             .filter(|field| {
                 let field_ty = field.ty(self.tcx, identity_substs);
-                Self::find_param_in_ty(field_ty.into(), param_to_point_at)
+                find_param_in_ty(field_ty.into(), param_to_point_at)
             })
             .collect();
 
@@ -348,7 +355,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .inputs()
             .iter()
             .enumerate()
-            .filter(|(_, ty)| Self::find_param_in_ty((**ty).into(), param_to_point_at))
+            .filter(|(_, ty)| find_param_in_ty((**ty).into(), param_to_point_at))
             .collect();
         // If there's one field that references the given generic, great!
         if let [(idx, _)] = args_referencing_param.as_slice()
@@ -459,7 +466,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// obligation. Hence we refine the `expr` "outwards-in" and bail at the first kind of expression/impl we don't recognize.
     ///
     /// This function returns a `Result<&Expr, &Expr>` - either way, it returns the `Expr` whose span should be
-    /// reported as an error. If it is `Ok`, then it means it refined successfull. If it is `Err`, then it may be
+    /// reported as an error. If it is `Ok`, then it means it refined successful. If it is `Err`, then it may be
     /// only a partial success - but it cannot be refined even further.
     fn blame_specific_expr_if_possible_for_derived_predicate_obligation(
         &self,
@@ -527,7 +534,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// - in_ty: `(Option<Vec<T>, bool)`
     /// we would drill until we arrive at `vec![1, 2, 3]`.
     ///
-    /// If successful, we return `Ok(refined_expr)`. If unsuccesful, we return `Err(partially_refined_expr`),
+    /// If successful, we return `Ok(refined_expr)`. If unsuccessful, we return `Err(partially_refined_expr`),
     /// which will go as far as possible. For example, given `(foo(), false)` instead, we would drill to
     /// `foo()` and then return `Err("foo()")`.
     ///
@@ -571,8 +578,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Find out which of `in_ty_elements` refer to `param`.
             // FIXME: It may be better to take the first if there are multiple,
             // just so that the error points to a smaller expression.
-            let Some((drill_expr, drill_ty)) = Self::is_iterator_singleton(expr_elements.iter().zip( in_ty_elements.iter()).filter(|(_expr_elem, in_ty_elem)| {
-                Self::find_param_in_ty((*in_ty_elem).into(), param)
+            let Some((drill_expr, drill_ty)) = is_iterator_singleton(expr_elements.iter().zip( in_ty_elements.iter()).filter(|(_expr_elem, in_ty_elem)| {
+                find_param_in_ty((*in_ty_elem).into(), param)
             })) else {
                 // The param is not mentioned, or it is mentioned in multiple indexes.
                 return Err(expr);
@@ -620,10 +627,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // We need to know which of the generic parameters mentions our target param.
             // We expect that at least one of them does, since it is expected to be mentioned.
             let Some((drill_generic_index, generic_argument_type)) =
-                Self::is_iterator_singleton(
+                is_iterator_singleton(
                     in_ty_adt_generic_args.iter().enumerate().filter(
                         |(_index, in_ty_generic)| {
-                            Self::find_param_in_ty(*in_ty_generic, param)
+                            find_param_in_ty(*in_ty_generic, param)
                         },
                     ),
                 ) else {
@@ -743,10 +750,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // We need to know which of the generic parameters mentions our target param.
             // We expect that at least one of them does, since it is expected to be mentioned.
             let Some((drill_generic_index, generic_argument_type)) =
-                Self::is_iterator_singleton(
+                is_iterator_singleton(
                     in_ty_adt_generic_args.iter().enumerate().filter(
                         |(_index, in_ty_generic)| {
-                            Self::find_param_in_ty(*in_ty_generic, param)
+                            find_param_in_ty(*in_ty_generic, param)
                         },
                     ),
                 ) else {
@@ -785,14 +792,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             //     outer contextual information.
 
             // (1) Find the (unique) field index which mentions the type in our constraint:
-            let Some((field_index, field_type)) = Self::is_iterator_singleton(
+            let Some((field_index, field_type)) = is_iterator_singleton(
                 in_ty_adt
                     .variant_with_id(variant_def_id)
                     .fields
                     .iter()
                     .map(|field| field.ty(self.tcx, *in_ty_adt_generic_args))
                     .enumerate()
-                    .filter(|(_index, field_type)| Self::find_param_in_ty((*field_type).into(), param))
+                    .filter(|(_index, field_type)| find_param_in_ty((*field_type).into(), param))
             ) else {
                 return Err(expr);
             };
@@ -825,20 +832,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         Err(expr)
     }
+}
 
-    // FIXME: This can be made into a private, non-impl function later.
-    /// Traverses the given ty (either a `ty::Ty` or a `ty::GenericArg`) and searches for references
-    /// to the given `param_to_point_at`. Returns `true` if it finds any use of the param.
-    pub fn find_param_in_ty(
-        ty: ty::GenericArg<'tcx>,
-        param_to_point_at: ty::GenericArg<'tcx>,
-    ) -> bool {
-        let mut walk = ty.walk();
-        while let Some(arg) = walk.next() {
-            if arg == param_to_point_at {
-                return true;
-            }
-            if let ty::GenericArgKind::Type(ty) = arg.unpack()
+/// Traverses the given ty (either a `ty::Ty` or a `ty::GenericArg`) and searches for references
+/// to the given `param_to_point_at`. Returns `true` if it finds any use of the param.
+fn find_param_in_ty<'tcx>(
+    ty: ty::GenericArg<'tcx>,
+    param_to_point_at: ty::GenericArg<'tcx>,
+) -> bool {
+    let mut walk = ty.walk();
+    while let Some(arg) = walk.next() {
+        if arg == param_to_point_at {
+            return true;
+        }
+        if let ty::GenericArgKind::Type(ty) = arg.unpack()
                 && let ty::Alias(ty::Projection, ..) = ty.kind()
             {
                 // This logic may seem a bit strange, but typically when
@@ -849,16 +856,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // in some UI tests.
                 walk.skip_current_subtree();
             }
-        }
-        false
     }
+    false
+}
 
-    // FIXME: This can be made into a private, non-impl function later.
-    /// Returns `Some(iterator.next())` if it has exactly one item, and `None` otherwise.
-    pub fn is_iterator_singleton<T>(mut iterator: impl Iterator<Item = T>) -> Option<T> {
-        match (iterator.next(), iterator.next()) {
-            (_, Some(_)) => None,
-            (first, _) => first,
-        }
+/// Returns `Some(iterator.next())` if it has exactly one item, and `None` otherwise.
+fn is_iterator_singleton<T>(mut iterator: impl Iterator<Item = T>) -> Option<T> {
+    match (iterator.next(), iterator.next()) {
+        (_, Some(_)) => None,
+        (first, _) => first,
     }
 }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index a46bdeb41..ea1b52daa 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -24,14 +24,14 @@ use rustc_hir_analysis::structured_errors::StructuredDiagnostic;
 use rustc_index::vec::IndexVec;
 use rustc_infer::infer::error_reporting::{FailureCode, ObligationCauseExt};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::InferOk;
 use rustc_infer::infer::TypeTrace;
+use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::{self, DefIdTree, IsSuggestable, Ty};
+use rustc_middle::ty::{self, IsSuggestable, Ty};
 use rustc_session::Session;
 use rustc_span::symbol::{kw, Ident};
-use rustc_span::{self, sym, Span};
+use rustc_span::{self, sym, BytePos, Span};
 use rustc_trait_selection::traits::{self, ObligationCauseCode, SelectionContext};
 
 use std::iter;
@@ -301,9 +301,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // 3. Check if the formal type is a supertype of the checked one
             //    and register any such obligations for future type checks
-            let supertype_error = self
-                .at(&self.misc(provided_arg.span), self.param_env)
-                .sup(formal_input_ty, coerced_ty);
+            let supertype_error = self.at(&self.misc(provided_arg.span), self.param_env).sup(
+                DefineOpaqueTypes::No,
+                formal_input_ty,
+                coerced_ty,
+            );
             let subtyping_error = match supertype_error {
                 Ok(InferOk { obligations, value: () }) => {
                     self.register_predicates(obligations);
@@ -470,7 +472,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err_code: &str,
         fn_def_id: Option<DefId>,
         call_span: Span,
-        call_expr: &hir::Expr<'tcx>,
+        call_expr: &'tcx hir::Expr<'tcx>,
     ) {
         // Next, let's construct the error
         let (error_span, full_call_span, call_name, is_method) = match &call_expr.kind {
@@ -585,7 +587,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // Using probe here, since we don't want this subtyping to affect inference.
             let subtyping_error = self.probe(|_| {
-                self.at(&self.misc(arg_span), self.param_env).sup(formal_input_ty, coerced_ty).err()
+                self.at(&self.misc(arg_span), self.param_env)
+                    .sup(DefineOpaqueTypes::No, formal_input_ty, coerced_ty)
+                    .err()
             });
 
             // Same as above: if either the coerce type or the checked type is an error type,
@@ -764,7 +768,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let (provided_ty, provided_span) = provided_arg_tys[*provided_idx];
             let trace =
                 mk_trace(provided_span, formal_and_expected_inputs[*expected_idx], provided_ty);
-            if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308(_)) {
+            if !matches!(trace.cause.as_failure_code(*e), FailureCode::Error0308) {
                 self.err_ctxt().report_and_explain_type_error(trace, *e).emit();
                 return true;
             }
@@ -803,24 +807,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 full_call_span,
                 format!("arguments to this {} are incorrect", call_name),
             );
-            if let (Some(callee_ty), hir::ExprKind::MethodCall(_, rcvr, _, _)) =
-                (callee_ty, &call_expr.kind)
+
+            if let hir::ExprKind::MethodCall(_, rcvr, _, _) = call_expr.kind
+                && provided_idx.as_usize() == expected_idx.as_usize()
             {
-                // Type that would have accepted this argument if it hadn't been inferred earlier.
-                // FIXME: We leave an inference variable for now, but it'd be nice to get a more
-                // specific type to increase the accuracy of the diagnostic.
-                let expected = self.infcx.next_ty_var(TypeVariableOrigin {
-                    kind: TypeVariableOriginKind::MiscVariable,
-                    span: full_call_span,
-                });
-                self.point_at_expr_source_of_inferred_type(
+                self.note_source_of_type_mismatch_constraint(
                     &mut err,
                     rcvr,
-                    expected,
-                    callee_ty,
-                    provided_arg_span,
+                    crate::demand::TypeMismatchSource::Arg {
+                        call_expr,
+                        incompatible_arg: provided_idx.as_usize(),
+                    },
                 );
             }
+
             // Call out where the function is defined
             self.label_fn_like(
                 &mut err,
@@ -890,8 +890,13 @@ 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));
         let mut suggestions = vec![];
         while let Some(error) = errors.next() {
+            only_extras_so_far &= matches!(error, Error::Extra(_));
+
             match error {
                 Error::Invalid(provided_idx, expected_idx, compatibility) => {
                     let (formal_ty, expected_ty) = formal_and_expected_inputs[expected_idx];
@@ -937,10 +942,34 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         if arg_idx.index() > 0
                         && let Some((_, prev)) = provided_arg_tys
                             .get(ProvidedIdx::from_usize(arg_idx.index() - 1)
-                    ) {
-                        // Include previous comma
-                        span = prev.shrink_to_hi().to(span);
-                    }
+                        ) {
+                            // Include previous comma
+                            span = prev.shrink_to_hi().to(span);
+                        }
+
+                        // Is last argument for deletion in a row starting from the 0-th argument?
+                        // Then delete the next comma, so we are not left with `f(, ...)`
+                        //
+                        //     fn f() {}
+                        //   - f(0, 1,)
+                        //   + f()
+                        if only_extras_so_far
+                            && errors
+                                .peek()
+                                .map_or(true, |next_error| !matches!(next_error, Error::Extra(_)))
+                        {
+                            let next = provided_arg_tys
+                                .get(arg_idx + 1)
+                                .map(|&(_, sp)| sp)
+                                .unwrap_or_else(|| {
+                                    // Subtract one to move before `)`
+                                    call_expr.span.with_lo(call_expr.span.hi() - BytePos(1))
+                                });
+
+                            // Include next comma
+                            span = span.until(next);
+                        }
+
                         suggestions.push((span, String::new()));
 
                         suggestion_text = match suggestion_text {
@@ -1158,11 +1187,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // index position where it *should have been*, which is *after* the previous one.
             if let Some(provided_idx) = provided_idx {
                 prev = provided_idx.index() as i64;
+                continue;
             }
             let idx = ProvidedIdx::from_usize((prev + 1) as usize);
-            if let None = provided_idx
-                && let Some((_, arg_span)) = provided_arg_tys.get(idx)
-            {
+            if let Some((_, arg_span)) = provided_arg_tys.get(idx) {
+                prev += 1;
                 // There is a type that was *not* found anywhere, so it isn't a move, but a
                 // replacement and we look at what type it should have been. This will allow us
                 // To suggest a multipart suggestion when encountering `foo(1, "")` where the def
@@ -1380,7 +1409,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.demand_eqtype(init.span, local_ty, init_ty);
             init_ty
         } else {
-            self.check_expr_coercable_to_type(init, local_ty, None)
+            self.check_expr_coercible_to_type(init, local_ty, None)
         }
     }
 
@@ -1665,7 +1694,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Given a function block's `HirId`, returns its `FnDecl` if it exists, or `None` otherwise.
     fn get_parent_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident)> {
         let parent = self.tcx.hir().get_by_def_id(self.tcx.hir().get_parent_item(blk_id).def_id);
-        self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
+        self.get_node_fn_decl(parent).map(|(_, fn_decl, ident, _)| (fn_decl, ident))
     }
 
     /// If `expr` is a `match` expression that has only one non-`!` arm, use that arm's tail
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index 1dea3e6f9..c6fd0b610 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -211,13 +211,13 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
     fn get_type_parameter_bounds(
         &self,
         _: Span,
-        def_id: DefId,
+        def_id: LocalDefId,
         _: Ident,
     ) -> ty::GenericPredicates<'tcx> {
         let tcx = self.tcx;
-        let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
+        let item_def_id = tcx.hir().ty_param_owner(def_id);
         let generics = tcx.generics_of(item_def_id);
-        let index = generics.param_def_id_to_index[&def_id];
+        let index = generics.param_def_id_to_index[&def_id.to_def_id()];
         ty::GenericPredicates {
             parent: None,
             predicates: tcx.arena.alloc_from_iter(
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index c49621b7c..5fda4e191 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -16,7 +16,7 @@ use rustc_infer::traits::{self, StatementAsExpression};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
-    self, suggest_constraining_type_params, Binder, DefIdTree, IsSuggestable, ToPredicate, Ty,
+    self, suggest_constraining_type_params, Binder, IsSuggestable, ToPredicate, Ty,
     TypeVisitableExt,
 };
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -64,8 +64,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let expr = expr.peel_drop_temps();
         self.suggest_missing_semicolon(err, expr, expected, false);
         let mut pointing_at_return_type = false;
-        if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
-            let fn_id = self.tcx.hir().get_return_block(blk_id).unwrap();
+        if let Some((fn_id, fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
             pointing_at_return_type = self.suggest_missing_return_type(
                 err,
                 &fn_decl,
@@ -166,8 +165,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         ty: Ty<'tcx>,
     ) -> Option<(DefIdOrName, Ty<'tcx>, Vec<Ty<'tcx>>)> {
-        let body_hir_id = self.tcx.hir().local_def_id_to_hir_id(self.body_id);
-        self.err_ctxt().extract_callable_info(body_hir_id, self.param_env, ty)
+        self.err_ctxt().extract_callable_info(self.body_id, self.param_env, ty)
     }
 
     pub fn suggest_two_fn_call(
@@ -669,6 +667,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// This routine checks if the return type is left as default, the method is not part of an
     /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return
     /// type.
+    #[instrument(level = "trace", skip(self, err))]
     pub(in super::super) fn suggest_missing_return_type(
         &self,
         err: &mut Diagnostic,
@@ -705,28 +704,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     return true
                 }
             }
-            hir::FnRetTy::Return(ty) => {
-                let span = ty.span;
-
-                if let hir::TyKind::OpaqueDef(item_id, ..) = ty.kind
-                && let hir::Node::Item(hir::Item {
-                    kind: hir::ItemKind::OpaqueTy(op_ty),
-                    ..
-                }) = self.tcx.hir().get(item_id.hir_id())
-                && let hir::OpaqueTy {
-                    bounds: [bound], ..
-                } = op_ty
-                && let hir::GenericBound::LangItemTrait(
-                    hir::LangItem::Future, _, _, generic_args) = bound
-                && let hir::GenericArgs { bindings: [ty_binding], .. } = generic_args
-                && let hir::TypeBinding { kind, .. } = ty_binding
-                && let hir::TypeBindingKind::Equality { term } = kind
-                && let hir::Term::Ty(term_ty) = term {
+            hir::FnRetTy::Return(hir_ty) => {
+                let span = hir_ty.span;
+
+                if let hir::TyKind::OpaqueDef(item_id, ..) = hir_ty.kind
+                    && let hir::Node::Item(hir::Item {
+                        kind: hir::ItemKind::OpaqueTy(op_ty),
+                        ..
+                    }) = self.tcx.hir().get(item_id.hir_id())
+                    && let [hir::GenericBound::LangItemTrait(
+                        hir::LangItem::Future, _, _, generic_args)] = op_ty.bounds
+                    && let hir::GenericArgs { bindings: [ty_binding], .. } = generic_args
+                    && let hir::TypeBindingKind::Equality { term: hir::Term::Ty(term) } = ty_binding.kind
+                {
                     // Check if async function's return type was omitted.
                     // Don't emit suggestions if the found type is `impl Future<...>`.
-                    debug!("suggest_missing_return_type: found = {:?}", found);
+                    debug!(?found);
                     if found.is_suggestable(self.tcx, false) {
-                        if term_ty.span.is_empty() {
+                        if term.span.is_empty() {
                             err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: found.to_string() });
                             return true;
                         } else {
@@ -737,11 +732,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 // Only point to return type if the expected type is the return type, as if they
                 // are not, the expectation must have been caused by something else.
-                debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind);
-                let ty = self.astconv().ast_ty_to_ty(ty);
-                debug!("suggest_missing_return_type: return type {:?}", ty);
-                debug!("suggest_missing_return_type: expected type {:?}", ty);
-                let bound_vars = self.tcx.late_bound_vars(fn_id);
+                debug!("return type {:?}", hir_ty);
+                let ty = self.astconv().ast_ty_to_ty(hir_ty);
+                debug!("return type {:?}", ty);
+                debug!("expected type {:?}", expected);
+                let bound_vars = self.tcx.late_bound_vars(hir_ty.hir_id.owner.into());
                 let ty = Binder::bind_with_vars(ty, bound_vars);
                 let ty = self.normalize(span, ty);
                 let ty = self.tcx.erase_late_bound_regions(ty);
@@ -988,13 +983,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 )
                 .must_apply_modulo_regions()
           {
-              diag.span_suggestion_verbose(
-                  expr.span.shrink_to_hi(),
-                  "consider using clone here",
-                  ".clone()",
-                  Applicability::MachineApplicable,
-              );
-              return true;
+            let suggestion = match self.maybe_get_struct_pattern_shorthand_field(expr) {
+                Some(ident) => format!(": {}.clone()", ident),
+                None => ".clone()".to_string()
+            };
+
+            diag.span_suggestion_verbose(
+                expr.span.shrink_to_hi(),
+                "consider using clone here",
+                suggestion,
+                Applicability::MachineApplicable,
+            );
+            return true;
           }
         false
     }
@@ -1015,11 +1015,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut suggest_copied_or_cloned = || {
             let expr_inner_ty = substs.type_at(0);
             let expected_inner_ty = expected_substs.type_at(0);
-            if let ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
-                && self.can_eq(self.param_env, *ty, expected_inner_ty)
+            if let &ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
+                && self.can_eq(self.param_env, ty, expected_inner_ty)
             {
                 let def_path = self.tcx.def_path_str(adt_def.did());
-                if self.type_is_copy_modulo_regions(self.param_env, *ty, expr.span) {
+                if self.type_is_copy_modulo_regions(self.param_env, ty) {
                     diag.span_suggestion_verbose(
                         expr.span.shrink_to_hi(),
                         format!(
@@ -1033,9 +1033,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     && rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions(
                         self,
                         self.param_env,
-                        *ty,
+                        ty,
                         clone_did,
-                        expr.span
                     )
                 {
                     diag.span_suggestion_verbose(
@@ -1156,13 +1155,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return false;
         }
 
-        diag.span_suggestion(
+        let suggestion = match self.maybe_get_struct_pattern_shorthand_field(expr) {
+            Some(ident) => format!(": {}.is_some()", ident),
+            None => ".is_some()".to_string(),
+        };
+
+        diag.span_suggestion_verbose(
             expr.span.shrink_to_hi(),
             "use `Option::is_some` to test if the `Option` has a value",
-            ".is_some()",
+            suggestion,
             Applicability::MachineApplicable,
         );
-
         true
     }
 
diff --git a/compiler/rustc_hir_typeck/src/generator_interior/drop_ranges/cfg_build.rs b/compiler/rustc_hir_typeck/src/generator_interior/drop_ranges/cfg_build.rs
index 7c0402b1c..3e9a9ce1b 100644
--- a/compiler/rustc_hir_typeck/src/generator_interior/drop_ranges/cfg_build.rs
+++ b/compiler/rustc_hir_typeck/src/generator_interior/drop_ranges/cfg_build.rs
@@ -190,7 +190,6 @@ impl<'a, 'tcx> DropRangeVisitor<'a, 'tcx> {
             //
             // Some of these may be interesting in the future
             ExprKind::Path(..)
-            | ExprKind::Box(..)
             | ExprKind::ConstBlock(..)
             | ExprKind::Array(..)
             | ExprKind::Call(..)
@@ -478,7 +477,6 @@ impl<'a, 'tcx> Visitor<'tcx> for DropRangeVisitor<'a, 'tcx> {
             | ExprKind::AssignOp(..)
             | ExprKind::Binary(..)
             | ExprKind::Block(..)
-            | ExprKind::Box(..)
             | ExprKind::Cast(..)
             | ExprKind::Closure { .. }
             | ExprKind::ConstBlock(..)
@@ -528,8 +526,9 @@ impl DropRangesBuilder {
         let mut next = <_>::from(0u32);
         for value in tracked_values {
             for_each_consumable(hir, value, |value| {
-                if !tracked_value_map.contains_key(&value) {
-                    tracked_value_map.insert(value, next);
+                if let std::collections::hash_map::Entry::Vacant(e) = tracked_value_map.entry(value)
+                {
+                    e.insert(next);
                     next = next + 1;
                 }
             });
diff --git a/compiler/rustc_hir_typeck/src/generator_interior/mod.rs b/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
index 2e41c2041..f39710804 100644
--- a/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
+++ b/compiler/rustc_hir_typeck/src/generator_interior/mod.rs
@@ -13,7 +13,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::HirIdSet;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{Arm, Expr, ExprKind, Guard, HirId, Pat, PatKind};
-use rustc_infer::infer::RegionVariableOrigin;
+use rustc_infer::infer::{DefineOpaqueTypes, RegionVariableOrigin};
 use rustc_middle::middle::region::{self, Scope, ScopeData, YieldData};
 use rustc_middle::ty::fold::FnMutDelegate;
 use rustc_middle::ty::{self, BoundVariableKind, RvalueScopes, Ty, TyCtxt, TypeVisitableExt};
@@ -239,8 +239,7 @@ pub fn resolve_interior<'a, 'tcx>(
             // typeck had previously found constraints that would cause them to be related.
 
             let mut counter = 0;
-            let mut mk_bound_region = |span| {
-                let kind = ty::BrAnon(counter, span);
+            let mut mk_bound_region = |kind| {
                 let var = ty::BoundVar::from_u32(counter);
                 counter += 1;
                 ty::BoundRegion { var, kind }
@@ -252,24 +251,23 @@ pub fn resolve_interior<'a, 'tcx>(
                         let origin = fcx.region_var_origin(vid);
                         match origin {
                             RegionVariableOrigin::EarlyBoundRegion(span, _) => {
-                                mk_bound_region(Some(span))
+                                mk_bound_region(ty::BrAnon(Some(span)))
                             }
-                            _ => mk_bound_region(None),
+                            _ => mk_bound_region(ty::BrAnon(None)),
                         }
                     }
-                    // FIXME: these should use `BrNamed`
                     ty::ReEarlyBound(region) => {
-                        mk_bound_region(Some(fcx.tcx.def_span(region.def_id)))
+                        mk_bound_region(ty::BrNamed(region.def_id, region.name))
                     }
                     ty::ReLateBound(_, ty::BoundRegion { kind, .. })
                     | ty::ReFree(ty::FreeRegion { bound_region: kind, .. }) => match kind {
-                        ty::BoundRegionKind::BrAnon(_, span) => mk_bound_region(span),
-                        ty::BoundRegionKind::BrNamed(def_id, _) => {
-                            mk_bound_region(Some(fcx.tcx.def_span(def_id)))
+                        ty::BoundRegionKind::BrAnon(span) => mk_bound_region(ty::BrAnon(span)),
+                        ty::BoundRegionKind::BrNamed(def_id, sym) => {
+                            mk_bound_region(ty::BrNamed(def_id, sym))
                         }
-                        ty::BoundRegionKind::BrEnv => mk_bound_region(None),
+                        ty::BoundRegionKind::BrEnv => mk_bound_region(ty::BrAnon(None)),
                     },
-                    _ => mk_bound_region(None),
+                    _ => mk_bound_region(ty::BrAnon(None)),
                 };
                 let r = fcx.tcx.mk_re_late_bound(current_depth, br);
                 r
@@ -293,10 +291,7 @@ pub fn resolve_interior<'a, 'tcx>(
             type_causes,
             FnMutDelegate {
                 regions: &mut |br| {
-                    let kind = match br.kind {
-                        ty::BrAnon(_, span) => ty::BrAnon(counter, span),
-                        _ => br.kind,
-                    };
+                    let kind = br.kind;
                     let var = ty::BoundVar::from_usize(bound_vars.len());
                     bound_vars.push(ty::BoundVariableKind::Region(kind));
                     counter += 1;
@@ -313,8 +308,7 @@ pub fn resolve_interior<'a, 'tcx>(
     // Extract type components to build the witness type.
     let type_list = fcx.tcx.mk_type_list_from_iter(type_causes.iter().map(|cause| cause.ty));
     let bound_vars = fcx.tcx.mk_bound_variable_kinds(&bound_vars);
-    let witness =
-        fcx.tcx.mk_generator_witness(ty::Binder::bind_with_vars(type_list, bound_vars.clone()));
+    let witness = fcx.tcx.mk_generator_witness(ty::Binder::bind_with_vars(type_list, bound_vars));
 
     drop(typeck_results);
     // Store the generator types and spans into the typeck results for this generator.
@@ -327,7 +321,11 @@ pub fn resolve_interior<'a, 'tcx>(
     );
 
     // Unify the type variable inside the generator with the new witness
-    match fcx.at(&fcx.misc(body.value.span), fcx.param_env).eq(interior, witness) {
+    match fcx.at(&fcx.misc(body.value.span), fcx.param_env).eq(
+        DefineOpaqueTypes::No,
+        interior,
+        witness,
+    ) {
         Ok(ok) => fcx.register_infer_ok_obligations(ok),
         _ => bug!("failed to relate {interior} and {witness}"),
     }
diff --git a/compiler/rustc_hir_typeck/src/inherited.rs b/compiler/rustc_hir_typeck/src/inherited.rs
index 26020382d..4110b176b 100644
--- a/compiler/rustc_hir_typeck/src/inherited.rs
+++ b/compiler/rustc_hir_typeck/src/inherited.rs
@@ -4,7 +4,6 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::HirIdMap;
-use rustc_infer::infer;
 use rustc_infer::infer::{DefiningAnchor, InferCtxt, InferOk, TyCtxtInferExt};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -58,8 +57,6 @@ pub struct Inherited<'tcx> {
     pub(super) deferred_generator_interiors:
         RefCell<Vec<(LocalDefId, hir::BodyId, Ty<'tcx>, hir::GeneratorKind)>>,
 
-    pub(super) body_id: Option<hir::BodyId>,
-
     /// Whenever we introduce an adjustment from `!` into a type variable,
     /// we record that type variable here. This is later used to inform
     /// fallback. See the `fallback` module for details.
@@ -75,48 +72,16 @@ impl<'tcx> Deref for Inherited<'tcx> {
     }
 }
 
-/// A temporary returned by `Inherited::build(...)`. This is necessary
-/// for multiple `InferCtxt` to share the same `typeck_results`
-/// without using `Rc` or something similar.
-pub struct InheritedBuilder<'tcx> {
-    infcx: infer::InferCtxtBuilder<'tcx>,
-    def_id: LocalDefId,
-    typeck_results: RefCell<ty::TypeckResults<'tcx>>,
-}
-
 impl<'tcx> Inherited<'tcx> {
-    pub fn build(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> InheritedBuilder<'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self {
         let hir_owner = tcx.hir().local_def_id_to_hir_id(def_id).owner;
 
-        InheritedBuilder {
-            infcx: tcx
-                .infer_ctxt()
-                .ignoring_regions()
-                .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id)),
-            def_id,
-            typeck_results: RefCell::new(ty::TypeckResults::new(hir_owner)),
-        }
-    }
-}
-
-impl<'tcx> InheritedBuilder<'tcx> {
-    pub fn enter<F, R>(mut self, f: F) -> R
-    where
-        F: FnOnce(&Inherited<'tcx>) -> R,
-    {
-        let def_id = self.def_id;
-        f(&Inherited::new(self.infcx.build(), def_id, self.typeck_results))
-    }
-}
-
-impl<'tcx> Inherited<'tcx> {
-    fn new(
-        infcx: InferCtxt<'tcx>,
-        def_id: LocalDefId,
-        typeck_results: RefCell<ty::TypeckResults<'tcx>>,
-    ) -> Self {
-        let tcx = infcx.tcx;
-        let body_id = tcx.hir().maybe_body_owned_by(def_id);
+        let infcx = tcx
+            .infer_ctxt()
+            .ignoring_regions()
+            .with_opaque_type_inference(DefiningAnchor::Bind(hir_owner.def_id))
+            .build();
+        let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner));
 
         Inherited {
             typeck_results,
@@ -130,7 +95,6 @@ impl<'tcx> Inherited<'tcx> {
             deferred_asm_checks: RefCell::new(Vec::new()),
             deferred_generator_interiors: RefCell::new(Vec::new()),
             diverging_type_vars: RefCell::new(Default::default()),
-            body_id,
             infer_var_info: RefCell::new(Default::default()),
         }
     }
diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs
index 19d2befc4..106f5bcd7 100644
--- a/compiler/rustc_hir_typeck/src/intrinsicck.rs
+++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs
@@ -4,7 +4,7 @@ use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
-use rustc_target::abi::{Pointer, VariantIdx};
+use rustc_target::abi::{FieldIdx, Pointer, VariantIdx};
 
 use super::FnCtxt;
 
@@ -28,7 +28,7 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
         }
 
         if def.variant(data_idx).fields.len() == 1 {
-            return def.variant(data_idx).fields[0].ty(tcx, substs);
+            return def.variant(data_idx).fields[FieldIdx::from_u32(0)].ty(tcx, substs);
         }
     }
 
@@ -84,6 +84,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let skeleton_string = |ty: Ty<'tcx>, sk| match sk {
             Ok(SizeSkeleton::Known(size)) => format!("{} bits", size.bits()),
             Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
+            Ok(SizeSkeleton::Generic(size)) => {
+                if let Some(size) = size.try_eval_target_usize(tcx, self.param_env) {
+                    format!("{size} bytes")
+                } else {
+                    format!("generic size {size}")
+                }
+            }
             Err(LayoutError::Unknown(bad)) => {
                 if bad == ty {
                     "this type does not have a fixed size".to_owned()
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index e397dfd45..45890abad 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -45,13 +45,14 @@ mod rvalue_scopes;
 mod upvar;
 mod writeback;
 
-pub use diverges::Diverges;
-pub use expectation::Expectation;
-pub use fn_ctxt::*;
-pub use inherited::{Inherited, InheritedBuilder};
+pub use fn_ctxt::FnCtxt;
+pub use inherited::Inherited;
 
 use crate::check::check_fn;
 use crate::coercion::DynamicCoerceMany;
+use crate::diverges::Diverges;
+use crate::expectation::Expectation;
+use crate::fn_ctxt::RawTy;
 use crate::gather_locals::GatherLocalsVisitor;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::{
@@ -74,7 +75,7 @@ use rustc_session::Session;
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::{sym, Span};
 
-fluent_messages! { "../locales/en-US.ftl" }
+fluent_messages! { "../messages.ftl" }
 
 #[macro_export]
 macro_rules! type_error_struct {
@@ -105,10 +106,9 @@ pub struct LocalTy<'tcx> {
 /// (notably closures), `typeck_results(def_id)` would wind up
 /// redirecting to the owning function.
 fn primary_body_of(
-    tcx: TyCtxt<'_>,
-    id: hir::HirId,
+    node: Node<'_>,
 ) -> Option<(hir::BodyId, Option<&hir::Ty<'_>>, Option<&hir::FnSig<'_>>)> {
-    match tcx.hir().get(id) {
+    match node {
         Node::Item(item) => match item.kind {
             hir::ItemKind::Const(ty, body) | hir::ItemKind::Static(ty, _, body) => {
                 Some((body, Some(ty), None))
@@ -142,8 +142,7 @@ fn has_typeck_results(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
     }
 
     if let Some(def_id) = def_id.as_local() {
-        let id = tcx.hir().local_def_id_to_hir_id(def_id);
-        primary_body_of(tcx, id).is_some()
+        primary_body_of(tcx.hir().get_by_def_id(def_id)).is_some()
     } else {
         false
     }
@@ -198,143 +197,140 @@ fn typeck_with_fallback<'tcx>(
     }
 
     let id = tcx.hir().local_def_id_to_hir_id(def_id);
+    let node = tcx.hir().get(id);
     let span = tcx.hir().span(id);
 
     // Figure out what primary body this item has.
-    let (body_id, body_ty, fn_sig) = primary_body_of(tcx, id).unwrap_or_else(|| {
+    let (body_id, body_ty, fn_sig) = primary_body_of(node).unwrap_or_else(|| {
         span_bug!(span, "can't type-check body of {:?}", def_id);
     });
     let body = tcx.hir().body(body_id);
 
-    let typeck_results = Inherited::build(tcx, def_id).enter(|inh| {
-        let param_env = tcx.param_env(def_id);
-        let param_env = if tcx.has_attr(def_id.to_def_id(), sym::rustc_do_not_const_check) {
-            param_env.without_const()
+    let param_env = tcx.param_env(def_id);
+    let param_env = if tcx.has_attr(def_id, sym::rustc_do_not_const_check) {
+        param_env.without_const()
+    } else {
+        param_env
+    };
+    let inh = Inherited::new(tcx, def_id);
+    let mut fcx = FnCtxt::new(&inh, param_env, def_id);
+
+    if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
+        let fn_sig = if rustc_hir_analysis::collect::get_infer_ret_ty(&decl.output).is_some() {
+            fcx.astconv().ty_of_fn(id, header.unsafety, header.abi, decl, None, None)
         } else {
-            param_env
+            tcx.fn_sig(def_id).subst_identity()
         };
-        let mut fcx = FnCtxt::new(&inh, param_env, def_id);
-
-        if let Some(hir::FnSig { header, decl, .. }) = fn_sig {
-            let fn_sig = if rustc_hir_analysis::collect::get_infer_ret_ty(&decl.output).is_some() {
-                fcx.astconv().ty_of_fn(id, header.unsafety, header.abi, decl, None, None)
-            } else {
-                tcx.fn_sig(def_id).subst_identity()
-            };
 
-            check_abi(tcx, id, span, fn_sig.abi());
+        check_abi(tcx, id, span, fn_sig.abi());
 
-            // Compute the function signature from point of view of inside the fn.
-            let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
-            let fn_sig = fcx.normalize(body.value.span, fn_sig);
+        // Compute the function signature from point of view of inside the fn.
+        let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);
+        let fn_sig = fcx.normalize(body.value.span, fn_sig);
 
-            check_fn(&mut fcx, fn_sig, decl, def_id, body, None);
-        } else {
-            let expected_type = body_ty
-                .and_then(|ty| match ty.kind {
-                    hir::TyKind::Infer => Some(fcx.astconv().ast_ty_to_ty(ty)),
-                    _ => None,
-                })
-                .unwrap_or_else(|| match tcx.hir().get(id) {
-                    Node::AnonConst(_) => match tcx.hir().get(tcx.hir().parent_id(id)) {
-                        Node::Expr(&hir::Expr {
-                            kind: hir::ExprKind::ConstBlock(ref anon_const),
-                            ..
-                        }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
-                            kind: TypeVariableOriginKind::TypeInference,
-                            span,
-                        }),
-                        Node::Ty(&hir::Ty {
-                            kind: hir::TyKind::Typeof(ref anon_const), ..
-                        }) if anon_const.hir_id == id => fcx.next_ty_var(TypeVariableOrigin {
-                            kind: TypeVariableOriginKind::TypeInference,
-                            span,
-                        }),
-                        Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
-                        | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. }) => {
-                            let operand_ty =
-                                asm.operands.iter().find_map(|(op, _op_sp)| match op {
-                                    hir::InlineAsmOperand::Const { anon_const }
-                                        if anon_const.hir_id == id =>
-                                    {
-                                        // Inline assembly constants must be integers.
-                                        Some(fcx.next_int_var())
-                                    }
-                                    hir::InlineAsmOperand::SymFn { anon_const }
-                                        if anon_const.hir_id == id =>
-                                    {
-                                        Some(fcx.next_ty_var(TypeVariableOrigin {
-                                            kind: TypeVariableOriginKind::MiscVariable,
-                                            span,
-                                        }))
-                                    }
-                                    _ => None,
-                                });
-                            operand_ty.unwrap_or_else(fallback)
+        check_fn(&mut fcx, fn_sig, decl, def_id, body, None);
+    } else {
+        let expected_type = if let Some(&hir::Ty { kind: hir::TyKind::Infer, span, .. }) = body_ty {
+            Some(fcx.next_ty_var(TypeVariableOrigin {
+                kind: TypeVariableOriginKind::TypeInference,
+                span,
+            }))
+        } else if let Node::AnonConst(_) = node {
+            match tcx.hir().get(tcx.hir().parent_id(id)) {
+                Node::Expr(&hir::Expr {
+                    kind: hir::ExprKind::ConstBlock(ref anon_const), ..
+                }) if anon_const.hir_id == id => Some(fcx.next_ty_var(TypeVariableOrigin {
+                    kind: TypeVariableOriginKind::TypeInference,
+                    span,
+                })),
+                Node::Ty(&hir::Ty { kind: hir::TyKind::Typeof(ref anon_const), .. })
+                    if anon_const.hir_id == id =>
+                {
+                    Some(fcx.next_ty_var(TypeVariableOrigin {
+                        kind: TypeVariableOriginKind::TypeInference,
+                        span,
+                    }))
+                }
+                Node::Expr(&hir::Expr { kind: hir::ExprKind::InlineAsm(asm), .. })
+                | Node::Item(&hir::Item { kind: hir::ItemKind::GlobalAsm(asm), .. }) => {
+                    asm.operands.iter().find_map(|(op, _op_sp)| match op {
+                        hir::InlineAsmOperand::Const { anon_const } if anon_const.hir_id == id => {
+                            // Inline assembly constants must be integers.
+                            Some(fcx.next_int_var())
+                        }
+                        hir::InlineAsmOperand::SymFn { anon_const } if anon_const.hir_id == id => {
+                            Some(fcx.next_ty_var(TypeVariableOrigin {
+                                kind: TypeVariableOriginKind::MiscVariable,
+                                span,
+                            }))
                         }
-                        _ => fallback(),
-                    },
-                    _ => fallback(),
-                });
+                        _ => None,
+                    })
+                }
+                _ => None,
+            }
+        } else {
+            None
+        };
+        let expected_type = expected_type.unwrap_or_else(fallback);
 
-            let expected_type = fcx.normalize(body.value.span, expected_type);
-            fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
+        let expected_type = fcx.normalize(body.value.span, expected_type);
+        fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
 
-            // Gather locals in statics (because of block expressions).
-            GatherLocalsVisitor::new(&fcx).visit_body(body);
+        // Gather locals in statics (because of block expressions).
+        GatherLocalsVisitor::new(&fcx).visit_body(body);
 
-            fcx.check_expr_coercable_to_type(&body.value, expected_type, None);
+        fcx.check_expr_coercible_to_type(&body.value, expected_type, None);
 
-            fcx.write_ty(id, expected_type);
-        };
+        fcx.write_ty(id, expected_type);
+    };
 
-        fcx.type_inference_fallback();
-
-        // Even though coercion casts provide type hints, we check casts after fallback for
-        // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
-        fcx.check_casts();
-        fcx.select_obligations_where_possible(|_| {});
-
-        // Closure and generator analysis may run after fallback
-        // because they don't constrain other type variables.
-        // Closure analysis only runs on closures. Therefore they only need to fulfill non-const predicates (as of now)
-        let prev_constness = fcx.param_env.constness();
-        fcx.param_env = fcx.param_env.without_const();
-        fcx.closure_analyze(body);
-        fcx.param_env = fcx.param_env.with_constness(prev_constness);
-        assert!(fcx.deferred_call_resolutions.borrow().is_empty());
-        // Before the generator analysis, temporary scopes shall be marked to provide more
-        // precise information on types to be captured.
-        fcx.resolve_rvalue_scopes(def_id.to_def_id());
-
-        for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
-            let ty = fcx.normalize(span, ty);
-            fcx.require_type_is_sized(ty, span, code);
-        }
+    fcx.type_inference_fallback();
+
+    // Even though coercion casts provide type hints, we check casts after fallback for
+    // backwards compatibility. This makes fallback a stronger type hint than a cast coercion.
+    fcx.check_casts();
+    fcx.select_obligations_where_possible(|_| {});
+
+    // Closure and generator analysis may run after fallback
+    // because they don't constrain other type variables.
+    // Closure analysis only runs on closures. Therefore they only need to fulfill non-const predicates (as of now)
+    let prev_constness = fcx.param_env.constness();
+    fcx.param_env = fcx.param_env.without_const();
+    fcx.closure_analyze(body);
+    fcx.param_env = fcx.param_env.with_constness(prev_constness);
+    assert!(fcx.deferred_call_resolutions.borrow().is_empty());
+    // Before the generator analysis, temporary scopes shall be marked to provide more
+    // precise information on types to be captured.
+    fcx.resolve_rvalue_scopes(def_id.to_def_id());
+
+    for (ty, span, code) in fcx.deferred_sized_obligations.borrow_mut().drain(..) {
+        let ty = fcx.normalize(span, ty);
+        fcx.require_type_is_sized(ty, span, code);
+    }
 
-        fcx.select_obligations_where_possible(|_| {});
+    fcx.select_obligations_where_possible(|_| {});
 
-        debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
+    debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
 
-        // This must be the last thing before `report_ambiguity_errors`.
-        fcx.resolve_generator_interiors(def_id.to_def_id());
+    // This must be the last thing before `report_ambiguity_errors`.
+    fcx.resolve_generator_interiors(def_id.to_def_id());
 
-        debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
+    debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
 
-        if let None = fcx.infcx.tainted_by_errors() {
-            fcx.report_ambiguity_errors();
-        }
+    if let None = fcx.infcx.tainted_by_errors() {
+        fcx.report_ambiguity_errors();
+    }
 
-        if let None = fcx.infcx.tainted_by_errors() {
-            fcx.check_transmutes();
-        }
+    if let None = fcx.infcx.tainted_by_errors() {
+        fcx.check_transmutes();
+    }
 
-        fcx.check_asms();
+    fcx.check_asms();
 
-        fcx.infcx.skip_region_resolution();
+    fcx.infcx.skip_region_resolution();
 
-        fcx.resolve_type_vars_in_body(body)
-    });
+    let typeck_results = fcx.resolve_type_vars_in_body(body);
 
     // Consistency check our TypeckResults instance can hold all ItemLocalIds
     // it will need to hold.
diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
index 4d3969d28..6c861b593 100644
--- a/compiler/rustc_hir_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -59,10 +59,9 @@ use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::pat_util::EnumerateAndAdjustIterator;
 use rustc_hir::PatKind;
-use rustc_index::vec::Idx;
 use rustc_infer::infer::InferCtxt;
 use rustc_span::Span;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 use rustc_trait_selection::infer::InferCtxtExt;
 
 pub(crate) trait HirNode {
@@ -120,8 +119,8 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         self.infcx.tcx
     }
 
-    pub(crate) fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>, span: Span) -> bool {
-        self.infcx.type_is_copy_modulo_regions(self.param_env, ty, span)
+    pub(crate) fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>) -> bool {
+        self.infcx.type_is_copy_modulo_regions(self.param_env, ty)
     }
 
     fn resolve_vars_if_possible<T>(&self, value: T) -> T
@@ -331,7 +330,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                     expr,
                     base,
                     expr_ty,
-                    ProjectionKind::Field(field_idx as u32, VariantIdx::new(0)),
+                    ProjectionKind::Field(field_idx, FIRST_VARIANT),
                 ))
             }
 
@@ -382,7 +381,6 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             | hir::ExprKind::Struct(..)
             | hir::ExprKind::Repeat(..)
             | hir::ExprKind::InlineAsm(..)
-            | hir::ExprKind::Box(..)
             | hir::ExprKind::Err(_) => Ok(self.cat_rvalue(expr.hir_id, expr.span, expr_ty)),
         }
     }
@@ -562,7 +560,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             | Res::SelfTyParam { .. }
             | Res::SelfTyAlias { .. } => {
                 // Structs and Unions have only have one variant.
-                Ok(VariantIdx::new(0))
+                Ok(FIRST_VARIANT)
             }
             _ => bug!("expected ADT path, found={:?}", res),
         }
@@ -676,7 +674,8 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
 
                 for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
                     let subpat_ty = self.pat_ty_adjusted(subpat)?;
-                    let projection_kind = ProjectionKind::Field(i as u32, VariantIdx::new(0));
+                    let projection_kind =
+                        ProjectionKind::Field(FieldIdx::from_usize(i), FIRST_VARIANT);
                     let sub_place =
                         self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
                     self.cat_pattern_(sub_place, subpat, op)?;
@@ -691,7 +690,8 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
 
                 for (i, subpat) in subpats.iter().enumerate_and_adjust(total_fields, dots_pos) {
                     let subpat_ty = self.pat_ty_adjusted(subpat)?;
-                    let projection_kind = ProjectionKind::Field(i as u32, variant_index);
+                    let projection_kind =
+                        ProjectionKind::Field(FieldIdx::from_usize(i), variant_index);
                     let sub_place =
                         self.cat_projection(pat, place_with_id.clone(), subpat_ty, projection_kind);
                     self.cat_pattern_(sub_place, subpat, op)?;
@@ -716,7 +716,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
                         pat,
                         place_with_id.clone(),
                         field_ty,
-                        ProjectionKind::Field(field_index as u32, variant_index),
+                        ProjectionKind::Field(field_index, variant_index),
                     );
                     self.cat_pattern_(field_place, fp.pat, op)?;
                 }
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 169f128e0..9155a3d8d 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -8,7 +8,7 @@ use rustc_hir_analysis::astconv::generics::{
     check_generic_arg_count_for_call, create_substs_for_generic_args,
 };
 use rustc_hir_analysis::astconv::{AstConv, CreateSubstsForGenericArgsCtxt, IsMethodCall};
-use rustc_infer::infer::{self, InferOk};
+use rustc_infer::infer::{self, DefineOpaqueTypes, InferOk};
 use rustc_middle::traits::{ObligationCauseCode, UnifyReceiverContext};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
@@ -478,7 +478,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                 substs,
             })),
         );
-        match self.at(&cause, self.param_env).sup(method_self_ty, self_ty) {
+        match self.at(&cause, self.param_env).sup(DefineOpaqueTypes::No, method_self_ty, self_ty) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
             }
@@ -574,19 +574,15 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
     ) -> Option<Span> {
         let sized_def_id = self.tcx.lang_items().sized_trait()?;
 
-        traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied())
+        traits::elaborate(self.tcx, predicates.predicates.iter().copied())
             // We don't care about regions here.
-            .filter_map(|obligation| match obligation.predicate.kind().skip_binder() {
+            .filter_map(|pred| match pred.kind().skip_binder() {
                 ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred))
                     if trait_pred.def_id() == sized_def_id =>
                 {
                     let span = predicates
                         .iter()
-                        .find_map(
-                            |(p, span)| {
-                                if p == obligation.predicate { Some(span) } else { None }
-                            },
-                        )
+                        .find_map(|(p, span)| if p == pred { Some(span) } else { None })
                         .unwrap_or(rustc_span::DUMMY_SP);
                     Some((trait_pred, span))
                 }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 3bef5cfcd..4fd778910 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -13,6 +13,7 @@ use rustc_hir_analysis::astconv::InferCtxtExt as _;
 use rustc_hir_analysis::autoderef::{self, Autoderef};
 use rustc_infer::infer::canonical::OriginalQueryValues;
 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
+use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::infer::{self, InferOk, TyCtxtInferExt};
 use rustc_middle::middle::stability;
 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
@@ -699,7 +700,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     }
 
     fn assemble_inherent_candidates_for_incoherent_ty(&mut self, self_ty: Ty<'tcx>) {
-        let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsInfer) else {
+        let Some(simp) = simplify_type(self.tcx, self_ty, TreatParams::AsCandidateKey) else {
             bug!("unexpected incoherent type: {:?}", self_ty)
         };
         for &impl_def_id in self.tcx.incoherent_impls(simp) {
@@ -792,6 +793,14 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         // a `&self` method will wind up with an argument type like `&dyn Trait`.
         let trait_ref = principal.with_self_ty(self.tcx, self_ty);
         self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| {
+            if new_trait_ref.has_non_region_late_bound() {
+                this.tcx.sess.delay_span_bug(
+                    this.span,
+                    "tried to select method from HRTB with non-lifetime bound vars",
+                );
+                return;
+            }
+
             let new_trait_ref = this.erase_late_bound_regions(new_trait_ref);
 
             let (xform_self_ty, xform_ret_ty) =
@@ -836,24 +845,21 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 | ty::PredicateKind::ConstEvaluatable(..)
                 | ty::PredicateKind::ConstEquate(..)
                 | ty::PredicateKind::Ambiguous
-                | ty::PredicateKind::AliasEq(..)
+                | ty::PredicateKind::AliasRelate(..)
                 | ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
             }
         });
 
         self.elaborate_bounds(bounds, |this, poly_trait_ref, item| {
-            let trait_ref = this.erase_late_bound_regions(poly_trait_ref);
+            let trait_ref = this.instantiate_binder_with_fresh_vars(
+                this.span,
+                infer::LateBoundRegionConversionTime::FnCall,
+                poly_trait_ref,
+            );
 
             let (xform_self_ty, xform_ret_ty) =
                 this.xform_self_ty(item, trait_ref.self_ty(), trait_ref.substs);
 
-            // Because this trait derives from a where-clause, it
-            // should not contain any inference variables or other
-            // artifacts. This means it is safe to put into the
-            // `WhereClauseCandidate` and (eventually) into the
-            // `WhereClausePick`.
-            assert!(!trait_ref.substs.needs_infer());
-
             this.push_candidate(
                 Candidate {
                     xform_self_ty,
@@ -929,7 +935,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 if let Some(self_ty) = self_ty {
                     if self
                         .at(&ObligationCause::dummy(), self.param_env)
-                        .sup(fty.inputs()[0], self_ty)
+                        .sup(DefineOpaqueTypes::No, fty.inputs()[0], self_ty)
                         .is_err()
                     {
                         return false;
@@ -963,7 +969,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                             bound_trait_ref.def_id(),
                         ));
                     } else {
-                        let new_trait_ref = self.erase_late_bound_regions(bound_trait_ref);
+                        let new_trait_ref = self.instantiate_binder_with_fresh_vars(
+                            self.span,
+                            infer::LateBoundRegionConversionTime::FnCall,
+                            bound_trait_ref,
+                        );
 
                         let (xform_self_ty, xform_ret_ty) =
                             self.xform_self_ty(item, new_trait_ref.self_ty(), new_trait_ref.substs);
@@ -1026,12 +1036,21 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     true
                 }
             })
+            // ensure that we don't suggest unstable methods
+            .filter(|candidate| {
+                // note that `DUMMY_SP` is ok here because it is only used for
+                // suggestions and macro stuff which isn't applicable here.
+                !matches!(
+                    self.tcx.eval_stability(candidate.item.def_id, None, DUMMY_SP, None),
+                    stability::EvalResult::Deny { .. }
+                )
+            })
             .map(|candidate| candidate.item.ident(self.tcx))
             .filter(|&name| set.insert(name))
             .collect();
 
         // Sort them by the name so we have a stable result.
-        names.sort_by(|a, b| a.as_str().partial_cmp(b.as_str()).unwrap());
+        names.sort_by(|a, b| a.as_str().cmp(b.as_str()));
         names
     }
 
@@ -1338,6 +1357,7 @@ impl<'tcx> Pick<'tcx> {
                     container: _,
                     trait_item_def_id: _,
                     fn_has_self_parameter: _,
+                    opt_rpitit_info: _,
                 },
             kind: _,
             import_ids: _,
@@ -1434,9 +1454,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 CandidateSource::Trait(candidate.item.container_id(self.tcx))
             }
             TraitCandidate(trait_ref) => self.probe(|_| {
-                let _ = self
-                    .at(&ObligationCause::dummy(), self.param_env)
-                    .sup(candidate.xform_self_ty, self_ty);
+                let _ = self.at(&ObligationCause::dummy(), self.param_env).sup(
+                    DefineOpaqueTypes::No,
+                    candidate.xform_self_ty,
+                    self_ty,
+                );
                 match self.select_trait_candidate(trait_ref) {
                     Ok(Some(traits::ImplSource::UserDefined(ref impl_data))) => {
                         // If only a single impl matches, make the error message point
@@ -1463,10 +1485,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
         self.probe(|_| {
             // First check that the self type can be related.
-            let sub_obligations = match self
-                .at(&ObligationCause::dummy(), self.param_env)
-                .sup(probe.xform_self_ty, self_ty)
-            {
+            let sub_obligations = match self.at(&ObligationCause::dummy(), self.param_env).sup(
+                DefineOpaqueTypes::No,
+                probe.xform_self_ty,
+                self_ty,
+            ) {
                 Ok(InferOk { obligations, value: () }) => obligations,
                 Err(err) => {
                     debug!("--> cannot relate self-types {:?}", err);
@@ -1508,23 +1531,18 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
                     // Convert the bounds into obligations.
                     let impl_obligations = traits::predicates_for_generics(
-                        |_idx, span| {
-                            let misc = traits::ObligationCause::misc(span, self.body_id);
-                            let parent_trait_pred = ty::Binder::dummy(ty::TraitPredicate {
-                                trait_ref: ty::TraitRef::from_method(self.tcx, impl_def_id, substs),
-                                constness: ty::BoundConstness::NotConst,
-                                polarity: ty::ImplPolarity::Positive,
-                            });
-                            misc.derived_cause(parent_trait_pred, |derived| {
-                                traits::ImplDerivedObligation(Box::new(
-                                    traits::ImplDerivedObligationCause {
-                                        derived,
-                                        impl_or_alias_def_id: impl_def_id,
-                                        impl_def_predicate_index: None,
-                                        span,
-                                    },
-                                ))
-                            })
+                        |idx, span| {
+                            let code = if span.is_dummy() {
+                                traits::ExprItemObligation(impl_def_id, self.scope_expr_id, idx)
+                            } else {
+                                traits::ExprBindingObligation(
+                                    impl_def_id,
+                                    span,
+                                    self.scope_expr_id,
+                                    idx,
+                                )
+                            };
+                            ObligationCause::new(self.span, self.body_id, code)
                         },
                         self.param_env,
                         impl_bounds,
@@ -1541,8 +1559,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         if !self.predicate_may_hold(&o) {
                             result = ProbeResult::NoMatch;
                             let parent_o = o.clone();
-                            let implied_obligations =
-                                traits::elaborate_obligations(self.tcx, vec![o]);
+                            let implied_obligations = traits::elaborate(self.tcx, vec![o]);
                             for o in implied_obligations {
                                 let parent = if o == parent_o {
                                     None
@@ -1681,7 +1698,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 if let ProbeResult::Match = result
                     && self
                     .at(&ObligationCause::dummy(), self.param_env)
-                    .sup(return_ty, xform_ret_ty)
+                    .sup(DefineOpaqueTypes::No, return_ty, xform_ret_ty)
                     .is_err()
                 {
                     result = ProbeResult::BadReturnType;
@@ -1742,7 +1759,6 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     fn probe_for_similar_candidate(&mut self) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> {
         debug!("probing for method names similar to {:?}", self.method_name);
 
-        let steps = self.steps.clone();
         self.probe(|_| {
             let mut pcx = ProbeContext::new(
                 self.fcx,
@@ -1750,8 +1766,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 self.mode,
                 self.method_name,
                 self.return_type,
-                &self.orig_steps_var_values,
-                steps,
+                self.orig_steps_var_values,
+                self.steps,
                 self.scope_expr_id,
             );
             pcx.allow_similar_names = true;
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 60d56263d..900a6fa0d 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -27,7 +27,7 @@ use rustc_middle::traits::util::supertraits;
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
 use rustc_middle::ty::print::{with_crate_prefix, with_forced_trimmed_paths};
-use rustc_middle::ty::{self, DefIdTree, GenericArgKind, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, GenericArgKind, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::ty::{IsSuggestable, ToPolyTraitRef};
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Symbol;
@@ -42,7 +42,7 @@ use rustc_trait_selection::traits::{
 use super::probe::{AutorefOrPtrAdjustment, IsSuggestion, Mode, ProbeScope};
 use super::{CandidateSource, MethodError, NoMatchData};
 use rustc_hir::intravisit::Visitor;
-use std::cmp::Ordering;
+use std::cmp::{self, Ordering};
 use std::iter;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@@ -245,6 +245,28 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         None
     }
 
+    fn suggest_missing_writer(
+        &self,
+        rcvr_ty: Ty<'tcx>,
+        args: (&'tcx hir::Expr<'tcx>, &'tcx [hir::Expr<'tcx>]),
+    ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
+        let (ty_str, _ty_file) = self.tcx.short_ty_string(rcvr_ty);
+        let mut err =
+            struct_span_err!(self.tcx.sess, args.0.span, E0599, "cannot write into `{}`", ty_str);
+        err.span_note(
+            args.0.span,
+            "must implement `io::Write`, `fmt::Write`, or have a `write_fmt` method",
+        );
+        if let ExprKind::Lit(_) = args.0.kind {
+            err.span_help(
+                args.0.span.shrink_to_lo(),
+                "a writer is needed before this format string",
+            );
+        };
+
+        err
+    }
+
     pub fn report_no_match_method_error(
         &self,
         mut span: Span,
@@ -278,7 +300,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // We could pass the file for long types into these two, but it isn't strictly necessary
-        // given how targetted they are.
+        // given how targeted they are.
         if self.suggest_wrapping_range_with_parens(
             tcx,
             rcvr_ty,
@@ -323,16 +345,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        let mut err = struct_span_err!(
-            tcx.sess,
-            span,
-            E0599,
-            "no {} named `{}` found for {} `{}` in the current scope",
-            item_kind,
-            item_name,
-            rcvr_ty.prefix_string(self.tcx),
-            ty_str_reported,
-        );
+        let is_write = sugg_span.ctxt().outer_expn_data().macro_def_id.map_or(false, |def_id| {
+            tcx.is_diagnostic_item(sym::write_macro, def_id)
+                || tcx.is_diagnostic_item(sym::writeln_macro, def_id)
+        }) && item_name.name == Symbol::intern("write_fmt");
+        let mut err = if is_write
+            && let Some(args) = args
+        {
+            self.suggest_missing_writer(rcvr_ty, args)
+        } else {
+            struct_span_err!(
+                tcx.sess,
+                span,
+                E0599,
+                "no {} named `{}` found for {} `{}` in the current scope",
+                item_kind,
+                item_name,
+                rcvr_ty.prefix_string(self.tcx),
+                ty_str_reported,
+            )
+        };
         if tcx.sess.source_map().is_multiline(sugg_span) {
             err.span_label(sugg_span.with_hi(span.lo()), "");
         }
@@ -348,6 +380,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             err.downgrade_to_delayed_bug();
         }
 
+        if tcx.ty_is_opaque_future(rcvr_ty) && item_name.name == sym::poll {
+            err.help(&format!(
+                "method `poll` found on `Pin<&mut {ty_str}>`, \
+                see documentation for `std::pin::Pin`"
+            ));
+            err.help("self type must be pinned to call `Future::poll`, \
+                see https://rust-lang.github.io/async-book/04_pinning/01_chapter.html#pinning-in-practice"
+            );
+        }
+
         if let Mode::MethodCall = mode && let SelfSource::MethodCall(cal) = source {
             self.suggest_await_before_method(
                 &mut err, item_name, rcvr_ty, cal, span, expected.only_has_type(self),
@@ -405,6 +447,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
                 probe.is_ok()
             });
+
+            self.note_internal_mutation_in_method(
+                &mut err,
+                rcvr_expr,
+                expected.to_option(&self),
+                rcvr_ty,
+            );
         }
 
         let mut custom_span_label = false;
@@ -612,19 +661,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Find all the requirements that come from a local `impl` block.
             let mut skip_list: FxHashSet<_> = Default::default();
             let mut spanned_predicates = FxHashMap::default();
-            for (p, parent_p, impl_def_id, cause) in unsatisfied_predicates
-                .iter()
-                .filter_map(|(p, parent, c)| c.as_ref().map(|c| (p, parent, c)))
-                .filter_map(|(p, parent, c)| match c.code() {
-                    ObligationCauseCode::ImplDerivedObligation(data)
-                        if matches!(p.kind().skip_binder(), ty::PredicateKind::Clause(_)) =>
-                    {
-                        Some((p, parent, data.impl_or_alias_def_id, data))
+            for (p, parent_p, cause) in unsatisfied_predicates {
+                // Extract the predicate span and parent def id of the cause,
+                // if we have one.
+                let (item_def_id, cause_span) = match cause.as_ref().map(|cause| cause.code()) {
+                    Some(ObligationCauseCode::ImplDerivedObligation(data)) => {
+                        (data.impl_or_alias_def_id, data.span)
                     }
-                    _ => None,
-                })
-            {
-                match self.tcx.hir().get_if_local(impl_def_id) {
+                    Some(
+                        ObligationCauseCode::ExprBindingObligation(def_id, span, _, _)
+                        | ObligationCauseCode::BindingObligation(def_id, span),
+                    ) => (*def_id, *span),
+                    _ => continue,
+                };
+
+                // Don't point out the span of `WellFormed` predicates.
+                if !matches!(p.kind().skip_binder(), ty::PredicateKind::Clause(_)) {
+                    continue;
+                };
+
+                match self.tcx.hir().get_if_local(item_def_id) {
                     // Unmet obligation comes from a `derive` macro, point at it once to
                     // avoid multiple span labels pointing at the same place.
                     Some(Node::Item(hir::Item {
@@ -669,7 +725,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 }
                             });
                         for param in generics.params {
-                            if param.span == cause.span && sized_pred {
+                            if param.span == cause_span && sized_pred {
                                 let (sp, sugg) = match param.colon_span {
                                     Some(sp) => (sp.shrink_to_hi(), " ?Sized +"),
                                     None => (param.span.shrink_to_hi(), ": ?Sized"),
@@ -692,9 +748,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             (FxHashSet::default(), FxHashSet::default(), Vec::new())
                         });
                         entry.2.push(p);
-                        if cause.span != *item_span {
-                            entry.0.insert(cause.span);
-                            entry.1.insert((cause.span, "unsatisfied trait bound introduced here"));
+                        if cause_span != *item_span {
+                            entry.0.insert(cause_span);
+                            entry.1.insert((cause_span, "unsatisfied trait bound introduced here"));
                         } else {
                             if let Some(trait_ref) = of_trait {
                                 entry.0.insert(trait_ref.path.span);
@@ -726,9 +782,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let entry = entry.or_insert_with(|| {
                             (FxHashSet::default(), FxHashSet::default(), Vec::new())
                         });
-                        entry.0.insert(cause.span);
+                        entry.0.insert(cause_span);
                         entry.1.insert((ident.span, ""));
-                        entry.1.insert((cause.span, "unsatisfied trait bound introduced here"));
+                        entry.1.insert((cause_span, "unsatisfied trait bound introduced here"));
                         entry.2.push(p);
                     }
                     Some(node) => unreachable!("encountered `{node:?}`"),
@@ -1164,7 +1220,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 .inputs()
                                 .skip_binder()
                                 .get(0)
-                                .filter(|ty| ty.is_region_ptr() && !rcvr_ty.is_region_ptr())
+                                .filter(|ty| ty.is_ref() && !rcvr_ty.is_ref())
                                 .copied()
                                 .unwrap_or(rcvr_ty),
                         };
@@ -1247,7 +1303,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let target_ty = self
                 .autoderef(sugg_span, rcvr_ty)
                 .find(|(rcvr_ty, _)| {
-                    DeepRejectCtxt { treat_obligation_params: TreatParams::AsInfer }
+                    DeepRejectCtxt { treat_obligation_params: TreatParams::AsCandidateKey }
                         .types_may_unify(*rcvr_ty, impl_ty)
                 })
                 .map_or(impl_ty, |(ty, _)| ty)
@@ -1506,7 +1562,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .into_iter()
             .any(|info| self.associated_value(info.def_id, item_name).is_some());
         let found_assoc = |ty: Ty<'tcx>| {
-            simplify_type(tcx, ty, TreatParams::AsInfer)
+            simplify_type(tcx, ty, TreatParams::AsCandidateKey)
                 .and_then(|simp| {
                     tcx.incoherent_impls(simp)
                         .iter()
@@ -1766,7 +1822,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .variants()
                     .iter()
                     .flat_map(|variant| {
-                        let [field] = &variant.fields[..] else { return None; };
+                        let [field] = &variant.fields.raw[..] else { return None; };
                         let field_ty = field.ty(tcx, substs);
 
                         // Skip `_`, since that'll just lead to ambiguity.
@@ -2517,7 +2573,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         if !candidates.is_empty() {
             // Sort from most relevant to least relevant.
-            candidates.sort_by(|a, b| a.cmp(b).reverse());
+            candidates.sort_by_key(|&info| cmp::Reverse(info));
             candidates.dedup();
 
             let param_type = match rcvr_ty.kind() {
@@ -2636,7 +2692,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // cases where a positive bound implies a negative impl.
                 (candidates, Vec::new())
             } else if let Some(simp_rcvr_ty) =
-                simplify_type(self.tcx, rcvr_ty, TreatParams::AsPlaceholder)
+                simplify_type(self.tcx, rcvr_ty, TreatParams::ForLookup)
             {
                 let mut potential_candidates = Vec::new();
                 let mut explicitly_negative = Vec::new();
@@ -2651,7 +2707,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .any(|imp_did| {
                             let imp = self.tcx.impl_trait_ref(imp_did).unwrap().subst_identity();
                             let imp_simp =
-                                simplify_type(self.tcx, imp.self_ty(), TreatParams::AsPlaceholder);
+                                simplify_type(self.tcx, imp.self_ty(), TreatParams::ForLookup);
                             imp_simp.map_or(false, |s| s == simp_rcvr_ty)
                         })
                     {
diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index 80279ed96..a52c94cb0 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -12,16 +12,14 @@ use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
 };
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{
-    self, DefIdTree, IsSuggestable, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
-};
+use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt as _;
-use rustc_trait_selection::traits::{self, FulfillmentError};
+use rustc_trait_selection::traits::{self, FulfillmentError, ObligationCtxt};
 use rustc_type_ir::sty::TyKind::*;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@@ -103,9 +101,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match BinOpCategory::from(op) {
             BinOpCategory::Shortcircuit => {
                 // && and || are a simple case.
-                self.check_expr_coercable_to_type(lhs_expr, tcx.types.bool, None);
+                self.check_expr_coercible_to_type(lhs_expr, tcx.types.bool, None);
                 let lhs_diverges = self.diverges.get();
-                self.check_expr_coercable_to_type(rhs_expr, tcx.types.bool, None);
+                self.check_expr_coercible_to_type(rhs_expr, tcx.types.bool, None);
 
                 // Depending on the LHS' value, the RHS can never execute.
                 self.diverges.set(lhs_diverges);
@@ -148,10 +146,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         rhs_ty,
                         op,
                     );
-                    self.demand_suptype(expr.span, builtin_return_ty, return_ty);
+                    self.demand_eqtype(expr.span, builtin_return_ty, return_ty);
+                    builtin_return_ty
+                } else {
+                    return_ty
                 }
-
-                return_ty
             }
         }
     }
@@ -254,7 +253,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         );
 
         // see `NB` above
-        let rhs_ty = self.check_expr_coercable_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
+        let rhs_ty = self.check_expr_coercible_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
         let rhs_ty = self.resolve_vars_with_obligations(rhs_ty);
 
         let return_ty = match result {
@@ -433,7 +432,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if self.type_is_copy_modulo_regions(
                         self.param_env,
                         *lhs_deref_ty,
-                        lhs_expr.span,
                     ) {
                         suggest_deref_binop(*lhs_deref_ty);
                     }
@@ -775,7 +773,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             (None, Some(trait_did)) => {
                 let (obligation, _) =
                     self.obligation_for_method(cause, trait_did, lhs_ty, Some(input_types));
-                Err(rustc_trait_selection::traits::fully_solve_obligation(self, obligation))
+                // FIXME: This should potentially just add the obligation to the `FnCtxt`
+                let ocx = ObligationCtxt::new(&self.infcx);
+                ocx.register_obligation(obligation);
+                Err(ocx.select_all_or_error())
             }
         }
     }
@@ -962,21 +963,3 @@ fn is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool
         }
     }
 }
-
-struct TypeParamEraser<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, Span);
-
-impl<'tcx> TypeFolder<TyCtxt<'tcx>> for TypeParamEraser<'_, 'tcx> {
-    fn interner(&self) -> TyCtxt<'tcx> {
-        self.0.tcx
-    }
-
-    fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        match ty.kind() {
-            ty::Param(_) => self.0.next_ty_var(TypeVariableOrigin {
-                kind: TypeVariableOriginKind::MiscVariable,
-                span: self.1,
-            }),
-            _ => ty.super_fold_with(self),
-        }
-    }
-}
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index c36c75e44..af0bd26de 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -19,6 +19,7 @@ use rustc_span::hygiene::DesugaringKind;
 use rustc_span::source_map::{Span, Spanned};
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, DUMMY_SP};
+use rustc_target::abi::FieldIdx;
 use rustc_trait_selection::traits::{ObligationCause, Pattern};
 use ty::VariantDef;
 
@@ -36,6 +37,10 @@ pointers. If you encounter this error you should try to avoid dereferencing the
 You can read more about trait objects in the Trait Objects section of the Reference: \
 https://doc.rust-lang.org/reference/types.html#trait-objects";
 
+fn is_number(text: &str) -> bool {
+    text.chars().all(|c: char| c.is_digit(10))
+}
+
 /// Information about the expected type at the top level of type checking a pattern.
 ///
 /// **NOTE:** This is only for use by diagnostics. Do NOT use for type checking logic!
@@ -238,15 +243,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Note that there are two tests to check that this remains true
         // (`regions-reassign-{match,let}-bound-pointer.rs`).
         //
-        // 2. Things go horribly wrong if we use subtype. The reason for
-        // THIS is a fairly subtle case involving bound regions. See the
-        // `givens` field in `region_constraints`, as well as the test
+        // 2. An outdated issue related to the old HIR borrowck. See the test
         // `regions-relate-bound-regions-on-closures-to-inference-variables.rs`,
-        // for details. Short version is that we must sometimes detect
-        // relationships between specific region variables and regions
-        // bound in a closure signature, and that detection gets thrown
-        // off when we substitute fresh region variables here to enable
-        // subtyping.
     }
 
     /// Compute the new expected type and default binding mode from the old ones
@@ -1098,11 +1096,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 bug!("unexpected pattern type {:?}", pat_ty);
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(variant.fields.len(), ddpos) {
-                let field_ty = self.field_ty(subpat.span, &variant.fields[i], substs);
+                let field = &variant.fields[FieldIdx::from_usize(i)];
+                let field_ty = self.field_ty(subpat.span, field, substs);
                 self.check_pat(subpat, field_ty, def_bm, ti);
 
                 self.tcx.check_stability(
-                    variant.fields[i].did,
+                    variant.fields[FieldIdx::from_usize(i)].did,
                     Some(pat.hir_id),
                     subpat.span,
                     None,
@@ -1110,7 +1109,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         } else {
             // Pattern has wrong number of fields.
-            let e = self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err);
+            let e =
+                self.e0023(pat.span, res, qpath, subpats, &variant.fields.raw, expected, had_err);
             on_error(e);
             return tcx.ty_error(e);
         }
@@ -1340,8 +1340,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Index the struct fields' types.
         let field_map = variant
             .fields
-            .iter()
-            .enumerate()
+            .iter_enumerated()
             .map(|(i, field)| (field.ident(self.tcx).normalize_to_macros_2_0(), (i, field)))
             .collect::<FxHashMap<_, _>>();
 
@@ -1678,7 +1677,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         fields: &'tcx [hir::PatField<'tcx>],
         variant: &ty::VariantDef,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        if let (Some(CtorKind::Fn), PatKind::Struct(qpath, ..)) = (variant.ctor_kind(), &pat.kind) {
+        if let (Some(CtorKind::Fn), PatKind::Struct(qpath, pattern_fields, ..)) =
+            (variant.ctor_kind(), &pat.kind)
+        {
+            let is_tuple_struct_match = !pattern_fields.is_empty()
+                && pattern_fields.iter().map(|field| field.ident.name.as_str()).all(is_number);
+            if is_tuple_struct_match {
+                return None;
+            }
+
             let path = rustc_hir_pretty::to_string(rustc_hir_pretty::NO_ANN, |s| {
                 s.print_qpath(qpath, false)
             });
@@ -1900,7 +1907,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 prefix,
                 unmentioned_fields
                     .iter()
-                    .map(|(_, name)| name.to_string())
+                    .map(|(_, name)| {
+                        let field_name = name.to_string();
+                        if is_number(&field_name) {
+                            format!("{}: _", field_name)
+                        } else {
+                            field_name
+                        }
+                    })
                     .collect::<Vec<_>>()
                     .join(", "),
                 if have_inaccessible_fields { ", .." } else { "" },
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index 4a432328c..41a6ad80b 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -49,8 +49,7 @@ use rustc_span::{BytePos, Pos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_index::vec::Idx;
-use rustc_target::abi::VariantIdx;
+use rustc_target::abi::FIRST_VARIANT;
 
 use std::iter;
 
@@ -424,7 +423,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // closures. We want to make sure any adjustment that might make us move the place into
                 // the closure gets handled.
                 let (place, capture_kind) =
-                    restrict_precision_for_drop_types(self, place, capture_kind, usage_span);
+                    restrict_precision_for_drop_types(self, place, capture_kind);
 
                 capture_info.capture_kind = capture_kind;
                 (place, capture_info)
@@ -712,10 +711,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }
 
-                unreachable!(
-                    "we captured two identical projections: capture1 = {:?}, capture2 = {:?}",
-                    capture1, capture2
+                self.tcx.sess.delay_span_bug(
+                    closure_span,
+                    &format!(
+                        "two identical projections: ({:?}, {:?})",
+                        capture1.place.projections, capture2.place.projections
+                    ),
                 );
+                std::cmp::Ordering::Equal
             });
         }
 
@@ -1402,7 +1405,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         ProjectionKind::Field(..)
                     ))
                 );
-                def.variants().get(VariantIdx::new(0)).unwrap().fields.iter().enumerate().any(
+                def.variants().get(FIRST_VARIANT).unwrap().fields.iter_enumerated().any(
                     |(i, field)| {
                         let paths_using_field = captured_by_move_projs
                             .iter()
@@ -1410,7 +1413,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 if let ProjectionKind::Field(field_idx, _) =
                                     projs.first().unwrap().kind
                                 {
-                                    if (field_idx as usize) == i { Some(&projs[1..]) } else { None }
+                                    if field_idx == i { Some(&projs[1..]) } else { None }
                                 } else {
                                     unreachable!();
                                 }
@@ -1443,7 +1446,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .filter_map(|projs| {
                             if let ProjectionKind::Field(field_idx, _) = projs.first().unwrap().kind
                             {
-                                if (field_idx as usize) == i { Some(&projs[1..]) } else { None }
+                                if field_idx.index() == i { Some(&projs[1..]) } else { None }
                             } else {
                                 unreachable!();
                             }
@@ -1498,7 +1501,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     fn should_log_capture_analysis(&self, closure_def_id: LocalDefId) -> bool {
-        self.tcx.has_attr(closure_def_id.to_def_id(), sym::rustc_capture_analysis)
+        self.tcx.has_attr(closure_def_id, sym::rustc_capture_analysis)
     }
 
     fn log_capture_analysis_first_pass(
@@ -1822,9 +1825,8 @@ fn restrict_precision_for_drop_types<'a, 'tcx>(
     fcx: &'a FnCtxt<'a, 'tcx>,
     mut place: Place<'tcx>,
     mut curr_mode: ty::UpvarCapture,
-    span: Span,
 ) -> (Place<'tcx>, ty::UpvarCapture) {
-    let is_copy_type = fcx.infcx.type_is_copy_modulo_regions(fcx.param_env, place.ty(), span);
+    let is_copy_type = fcx.infcx.type_is_copy_modulo_regions(fcx.param_env, place.ty());
 
     if let (false, UpvarCapture::ByValue) = (is_copy_type, curr_mode) {
         for i in 0..place.projections.len() {
@@ -1891,14 +1893,13 @@ fn restrict_capture_precision(
 
     for (i, proj) in place.projections.iter().enumerate() {
         match proj.kind {
-            ProjectionKind::Index => {
-                // Arrays are completely captured, so we drop Index projections
+            ProjectionKind::Index | ProjectionKind::Subslice => {
+                // Arrays are completely captured, so we drop Index and Subslice projections
                 truncate_place_to_len_and_update_capture_kind(&mut place, &mut curr_mode, i);
                 return (place, curr_mode);
             }
             ProjectionKind::Deref => {}
             ProjectionKind::Field(..) => {} // ignore
-            ProjectionKind::Subslice => {}  // We never capture this
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index 00348f3af..e876fa275 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -44,8 +44,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // This attribute causes us to dump some writeback information
         // in the form of errors, which is used for unit tests.
-        let rustc_dump_user_substs =
-            self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs);
+        let rustc_dump_user_substs = self.tcx.has_attr(item_def_id, sym::rustc_dump_user_substs);
 
         let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
         for param in body.params {
@@ -748,7 +747,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
                 .infcx
                 .err_ctxt()
                 .emit_inference_failure_err(
-                    Some(self.body.id()),
+                    self.tcx.hir().body_owner_def_id(self.body.id()),
                     self.span.to_span(self.tcx),
                     p.into(),
                     E0282,