Auto merge of #111358 - compiler-errors:rollup-yv27vrp, r=compiler-errors

Rollup of 6 pull requests

Successful merges:

 - #104070 (Prevent aborting guard from aborting the process in a forced unwind)
 - #109410 (Introduce `AliasKind::Inherent` for inherent associated types)
 - #111004 (Migrate `mir_transform` to translatable diagnostics)
 - #111118 (Suggest struct when we get colon in fileds in enum)
 - #111170 (Diagnostic args are still args if they're documented)
 - #111354 (Fix miscompilation when calling default methods on `Future`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Cargo.lock

@@ -3353,6 +3353,7 @@ dependencies = [
  "rustc_middle",
  "rustc_mir_build",
  "rustc_mir_dataflow",
+ "rustc_mir_transform",
  "rustc_monomorphize",
  "rustc_parse",
  "rustc_passes",
@@ -3861,8 +3862,10 @@ dependencies = [
  "rustc_const_eval",
  "rustc_data_structures",
  "rustc_errors",
+ "rustc_fluent_macro",
  "rustc_hir",
  "rustc_index",
+ "rustc_macros",
  "rustc_middle",
  "rustc_mir_dataflow",
  "rustc_serialize",

compiler/rustc_codegen_gcc/src/builder.rs

@@ -1227,6 +1227,11 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
         (value1, value2)
     }
 
+    fn filter_landing_pad(&mut self, pers_fn: RValue<'gcc>) -> (RValue<'gcc>, RValue<'gcc>) {
+        // TODO(antoyo): generate the correct landing pad
+        self.cleanup_landing_pad(pers_fn)
+    }
+
     #[cfg(feature="master")]
     fn resume(&mut self, exn0: RValue<'gcc>, _exn1: RValue<'gcc>) {
         let exn_type = exn0.get_type();

compiler/rustc_codegen_llvm/src/builder.rs

@@ -985,13 +985,20 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
 
     fn cleanup_landing_pad(&mut self, pers_fn: &'ll Value) -> (&'ll Value, &'ll Value) {
         let ty = self.type_struct(&[self.type_i8p(), self.type_i32()], false);
-        let landing_pad = self.landing_pad(ty, pers_fn, 1 /* FIXME should this be 0? */);
+        let landing_pad = self.landing_pad(ty, pers_fn, 0);
         unsafe {
             llvm::LLVMSetCleanup(landing_pad, llvm::True);
         }
         (self.extract_value(landing_pad, 0), self.extract_value(landing_pad, 1))
     }
 
+    fn filter_landing_pad(&mut self, pers_fn: &'ll Value) -> (&'ll Value, &'ll Value) {
+        let ty = self.type_struct(&[self.type_i8p(), self.type_i32()], false);
+        let landing_pad = self.landing_pad(ty, pers_fn, 1);
+        self.add_clause(landing_pad, self.const_array(self.type_i8p(), &[]));
+        (self.extract_value(landing_pad, 0), self.extract_value(landing_pad, 1))
+    }
+
     fn resume(&mut self, exn0: &'ll Value, exn1: &'ll Value) {
         let ty = self.type_struct(&[self.type_i8p(), self.type_i32()], false);
         let mut exn = self.const_poison(ty);

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1600,7 +1600,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 bx = Bx::build(self.cx, llbb);
 
                 let llpersonality = self.cx.eh_personality();
-                bx.cleanup_landing_pad(llpersonality);
+                bx.filter_landing_pad(llpersonality);
 
                 funclet = None;
             }

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -274,6 +274,7 @@ pub trait BuilderMethods<'a, 'tcx>:
 
     // These are used by everyone except msvc
     fn cleanup_landing_pad(&mut self, pers_fn: Self::Value) -> (Self::Value, Self::Value);
+    fn filter_landing_pad(&mut self, pers_fn: Self::Value) -> (Self::Value, Self::Value);
     fn resume(&mut self, exn0: Self::Value, exn1: Self::Value);
 
     // These are used only by msvc

compiler/rustc_driver_impl/Cargo.toml

@@ -51,6 +51,7 @@ rustc_interface = { path = "../rustc_interface" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_span = { path = "../rustc_span" }
 rustc_hir_analysis = { path = "../rustc_hir_analysis" }
+rustc_mir_transform = { path = "../rustc_mir_transform" }
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
@@ -64,5 +65,8 @@ features = [
 [features]
 llvm = ['rustc_interface/llvm']
 max_level_info = ['rustc_log/max_level_info']
-rustc_use_parallel_compiler = ['rustc_data_structures/rustc_use_parallel_compiler', 'rustc_interface/rustc_use_parallel_compiler',
-    'rustc_middle/rustc_use_parallel_compiler']
+rustc_use_parallel_compiler = [
+    'rustc_data_structures/rustc_use_parallel_compiler',
+    'rustc_interface/rustc_use_parallel_compiler',
+    'rustc_middle/rustc_use_parallel_compiler'
+]

compiler/rustc_driver_impl/src/lib.rs

@@ -99,6 +99,7 @@ pub static DEFAULT_LOCALE_RESOURCES: &[&str] = &[
     rustc_middle::DEFAULT_LOCALE_RESOURCE,
     rustc_mir_build::DEFAULT_LOCALE_RESOURCE,
     rustc_mir_dataflow::DEFAULT_LOCALE_RESOURCE,
+    rustc_mir_transform::DEFAULT_LOCALE_RESOURCE,
     rustc_monomorphize::DEFAULT_LOCALE_RESOURCE,
     rustc_parse::DEFAULT_LOCALE_RESOURCE,
     rustc_passes::DEFAULT_LOCALE_RESOURCE,

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -571,6 +571,14 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         Some((diagnostic, handler))
     }
 
+    /// Retrieves the [`Handler`] if available
+    pub fn handler(&self) -> Option<&Handler> {
+        match self.inner.state {
+            DiagnosticBuilderState::Emittable(handler) => Some(handler),
+            DiagnosticBuilderState::AlreadyEmittedOrDuringCancellation => None,
+        }
+    }
+
     /// Buffers the diagnostic for later emission,
     /// unless handler has disabled such buffering.
     pub fn buffer(self, buffered_diagnostics: &mut Vec<Diagnostic>) {

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2419,6 +2419,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             return Ok(None);
         }
 
+        //
+        // Select applicable inherent associated type candidates modulo regions.
+        //
+
         // In contexts that have no inference context, just make a new one.
         // We do need a local variable to store it, though.
         let infcx_;
@@ -2431,7 +2435,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
         };
 
-        let param_env = tcx.param_env(block.owner.to_def_id());
+        // FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
+        // when inside of an ADT (#108491) or where clause.
+        let param_env = tcx.param_env(block.owner);
         let cause = ObligationCause::misc(span, block.owner.def_id);
 
         let mut fulfillment_errors = Vec::new();
@@ -2439,6 +2445,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let universe = infcx.create_next_universe();
 
             // Regions are not considered during selection.
+            // FIXME(non_lifetime_binders): Here we are "truncating" or "flattening" the universes
+            // of type and const binders. Is that correct in the selection phase? See also #109505.
             let self_ty = tcx.replace_escaping_bound_vars_uncached(
                 self_ty,
                 FnMutDelegate {
@@ -2454,41 +2462,40 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
             candidates
                 .iter()
-                .filter_map(|&(impl_, (assoc_item, def_scope))| {
+                .copied()
+                .filter(|&(impl_, _)| {
                     infcx.probe(|_| {
                         let ocx = ObligationCtxt::new_in_snapshot(&infcx);
 
-                        let impl_ty = tcx.type_of(impl_);
                         let impl_substs = infcx.fresh_item_substs(impl_);
-                        let impl_ty = impl_ty.subst(tcx, impl_substs);
+                        let impl_ty = tcx.type_of(impl_).subst(tcx, impl_substs);
                         let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
 
-                        // Check that the Self-types can be related.
-                        // FIXME(fmease): Should we use `eq` here?
-                        ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).ok()?;
+                        // Check that the self types can be related.
+                        // FIXME(inherent_associated_types): Should we use `eq` here? Method probing uses
+                        // `sup` for this situtation, too. What for? To constrain inference variables?
+                        if ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err()
+                        {
+                            return false;
+                        }
 
                         // Check whether the impl imposes obligations we have to worry about.
-                        let impl_bounds = tcx.predicates_of(impl_);
-                        let impl_bounds = impl_bounds.instantiate(tcx, impl_substs);
-
+                        let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_substs);
                         let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
-
                         let impl_obligations = traits::predicates_for_generics(
                             |_, _| cause.clone(),
                             param_env,
                             impl_bounds,
                         );
-
                         ocx.register_obligations(impl_obligations);
 
                         let mut errors = ocx.select_where_possible();
                         if !errors.is_empty() {
                             fulfillment_errors.append(&mut errors);
-                            return None;
+                            return false;
                         }
 
-                        // FIXME(fmease): Unsolved vars can escape this InferCtxt snapshot.
-                        Some((assoc_item, def_scope, infcx.resolve_vars_if_possible(impl_substs)))
+                        true
                     })
                 })
                 .collect()
@@ -2497,24 +2504,26 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         if applicable_candidates.len() > 1 {
             return Err(self.complain_about_ambiguous_inherent_assoc_type(
                 name,
-                applicable_candidates.into_iter().map(|(candidate, ..)| candidate).collect(),
+                applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(),
                 span,
             ));
         }
 
-        if let Some((assoc_item, def_scope, impl_substs)) = applicable_candidates.pop() {
+        if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
             self.check_assoc_ty(assoc_item, name, def_scope, block, span);
 
-            // FIXME(inherent_associated_types): To fully *confirm* the *probed* candidate, we still
-            // need to relate the Self-type with fresh item substs & register region obligations for
-            // regionck to prove/disprove.
+            // FIXME(fmease): Currently creating throwaway `parent_substs` to please
+            // `create_substs_for_associated_item`. Modify the latter instead (or sth. similar) to
+            // not require the parent substs logic.
+            let parent_substs = InternalSubsts::identity_for_item(tcx, impl_);
+            let substs =
+                self.create_substs_for_associated_item(span, assoc_item, segment, parent_substs);
+            let substs = tcx.mk_substs_from_iter(
+                std::iter::once(ty::GenericArg::from(self_ty))
+                    .chain(substs.into_iter().skip(parent_substs.len())),
+            );
 
-            let item_substs =
-                self.create_substs_for_associated_item(span, assoc_item, segment, impl_substs);
-
-            // FIXME(fmease, #106722): Check if the bounds on the parameters of the
-            // associated type hold, if any.
-            let ty = tcx.type_of(assoc_item).subst(tcx, item_substs);
+            let ty = tcx.mk_alias(ty::Inherent, tcx.mk_alias_ty(assoc_item, substs));
 
             return Ok(Some((ty, assoc_item)));
         }

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -210,6 +210,19 @@ fn do_orphan_check_impl<'tcx>(
                 NonlocalImpl::DisallowOther,
             ),
 
+            // ```
+            // struct S<T>(T);
+            // impl<T: ?Sized> S<T> {
+            //     type This = T;
+            // }
+            // impl<T: ?Sized> AutoTrait for S<T>::This {}
+            // ```
+            // FIXME(inherent_associated_types): The example code above currently leads to a cycle
+            ty::Alias(AliasKind::Inherent, _) => (
+                LocalImpl::Disallow { problematic_kind: "associated type" },
+                NonlocalImpl::DisallowOther,
+            ),
+
             // type Opaque = impl Trait;
             // impl AutoTrait for Opaque {}
             ty::Alias(AliasKind::Opaque, _) => (

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -1948,7 +1948,7 @@ fn is_late_bound_map(
                 ty::Param(param_ty) => {
                     self.arg_is_constrained[param_ty.index as usize] = true;
                 }
-                ty::Alias(ty::Projection, _) => return ControlFlow::Continue(()),
+                ty::Alias(ty::Projection | ty::Inherent, _) => return ControlFlow::Continue(()),
                 _ => (),
             }
             t.super_visit_with(self)

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -127,7 +127,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             // the def_id that this query was called with. We filter to only type and const args here
             // as a precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't
             // but it can't hurt to be safe ^^
-            if let ty::Alias(ty::Projection, projection) = ty.kind() {
+            if let ty::Alias(ty::Projection | ty::Inherent, projection) = ty.kind() {
                 let generics = tcx.generics_of(projection.def_id);
 
                 let arg_index = segment

compiler/rustc_hir_analysis/src/constrained_generic_params.rs

@@ -59,7 +59,7 @@ struct ParameterCollector {
 impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match *t.kind() {
-            ty::Alias(ty::Projection, ..) if !self.include_nonconstraining => {
+            ty::Alias(ty::Projection | ty::Inherent, ..) if !self.include_nonconstraining => {
                 // projections are not injective
                 return ControlFlow::Continue(());
             }

compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs

@@ -210,6 +210,9 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                 );
             }
 
+            // FIXME(inherent_associated_types): Handle this case properly.
+            ty::Alias(ty::Inherent, _) => {}
+
             _ => {}
         }
     }

compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs

@@ -843,7 +843,7 @@ fn find_param_in_ty<'tcx>(
             return true;
         }
         if let ty::GenericArgKind::Type(ty) = arg.unpack()
-                && let ty::Alias(ty::Projection, ..) = ty.kind()
+                && let ty::Alias(ty::Projection | ty::Inherent, ..) = ty.kind()
             {
                 // This logic may seem a bit strange, but typically when
                 // we have a projection type in a function signature, the

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -300,7 +300,7 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
         match ty.kind() {
             ty::Adt(adt_def, _) => Some(*adt_def),
             // FIXME(#104767): Should we handle bound regions here?
-            ty::Alias(ty::Projection, _) if !ty.has_escaping_bound_vars() => {
+            ty::Alias(ty::Projection | ty::Inherent, _) if !ty.has_escaping_bound_vars() => {
                 self.normalize(span, ty).ty_adt_def()
             }
             _ => None,

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2211,7 +2211,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         | ty::Float(_)
                         | ty::Adt(_, _)
                         | ty::Str
-                        | ty::Alias(ty::Projection, _)
+                        | ty::Alias(ty::Projection | ty::Inherent, _)
                         | ty::Param(_) => format!("{deref_ty}"),
                         // we need to test something like  <&[_]>::len or <(&[u32])>::len
                         // and Vec::function();

compiler/rustc_infer/src/infer/combine.rs

@@ -127,7 +127,8 @@ impl<'tcx> InferCtxt<'tcx> {
                 bug!()
             }
 
-            (_, ty::Alias(AliasKind::Projection, _)) | (ty::Alias(AliasKind::Projection, _), _)
+            (_, ty::Alias(AliasKind::Projection | AliasKind::Inherent, _))
+            | (ty::Alias(AliasKind::Projection | AliasKind::Inherent, _), _)
                 if self.tcx.trait_solver_next() =>
             {
                 relation.register_type_relate_obligation(a, b);

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2354,7 +2354,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let labeled_user_string = match bound_kind {
             GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
             GenericKind::Alias(ref p) => match p.kind(self.tcx) {
-                ty::AliasKind::Projection => format!("the associated type `{}`", p),
+                ty::AliasKind::Projection | ty::AliasKind::Inherent => {
+                    format!("the associated type `{}`", p)
+                }
                 ty::AliasKind::Opaque => format!("the opaque type `{}`", p),
             },
         };

compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs

@@ -71,9 +71,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                              #traits-as-parameters",
                         );
                     }
-                    (ty::Alias(ty::Projection, _), ty::Alias(ty::Projection, _)) => {
+                    (ty::Alias(ty::Projection | ty::Inherent, _), ty::Alias(ty::Projection | ty::Inherent, _)) => {
                         diag.note("an associated type was expected, but a different one was found");
                     }
+                    // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too.
                     (ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p))
                         if !tcx.is_impl_trait_in_trait(proj.def_id) =>
                     {
@@ -222,7 +223,7 @@ impl<T> Trait<T> for X {
                             diag.span_label(p_span, "this type parameter");
                         }
                     }
-                    (ty::Alias(ty::Projection, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
+                    (ty::Alias(ty::Projection | ty::Inherent, proj_ty), _) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
                         self.expected_projection(
                             diag,
                             proj_ty,
@@ -231,7 +232,7 @@ impl<T> Trait<T> for X {
                             cause.code(),
                         );
                     }
-                    (_, ty::Alias(ty::Projection, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
+                    (_, ty::Alias(ty::Projection | ty::Inherent, proj_ty)) if !tcx.is_impl_trait_in_trait(proj_ty.def_id) => {
                         let msg = format!(
                             "consider constraining the associated type `{}` to `{}`",
                             values.found, values.expected,

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -549,6 +549,7 @@ impl<'tcx> InferCtxt<'tcx> {
                     // We can't normalize associated types from `rustc_infer`,
                     // but we can eagerly register inference variables for them.
                     // FIXME(RPITIT): Don't replace RPITITs with inference vars.
+                    // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too.
                     ty::Alias(ty::Projection, projection_ty)
                         if !projection_ty.has_escaping_bound_vars()
                             && !tcx.is_impl_trait_in_trait(projection_ty.def_id) =>
@@ -569,6 +570,7 @@ impl<'tcx> InferCtxt<'tcx> {
                         hidden_ty
                     }
                     // FIXME(RPITIT): This can go away when we move to associated types
+                    // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too.
                     ty::Alias(
                         ty::Projection,
                         ty::AliasTy { def_id: def_id2, substs: substs2, .. },

compiler/rustc_lint/src/builtin.rs

@@ -62,6 +62,7 @@ use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
 use rustc_session::config::ExpectedValues;
 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
@@ -1442,6 +1443,10 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
             // Bounds are respected for `type X = impl Trait`
             return;
         }
+        if cx.tcx.type_of(item.owner_id).skip_binder().has_inherent_projections() {
+            // Bounds are respected for `type X = … Type::Inherent …`
+            return;
+        }
         // There must not be a where clause
         if type_alias_generics.predicates.is_empty() {
             return;
@@ -1561,7 +1566,6 @@ declare_lint_pass!(
 
 impl<'tcx> LateLintPass<'tcx> for TrivialConstraints {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
-        use rustc_middle::ty::visit::TypeVisitableExt;
         use rustc_middle::ty::Clause;
         use rustc_middle::ty::PredicateKind::*;
 
@@ -2898,6 +2902,7 @@ impl ClashingExternDeclarations {
                         | (Generator(..), Generator(..))
                         | (GeneratorWitness(..), GeneratorWitness(..))
                         | (Alias(ty::Projection, ..), Alias(ty::Projection, ..))
+                        | (Alias(ty::Inherent, ..), Alias(ty::Inherent, ..))
                         | (Alias(ty::Opaque, ..), Alias(ty::Opaque, ..)) => false,
 
                         // These definitely should have been caught above.

compiler/rustc_lint/src/types.rs

@@ -1119,14 +1119,14 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
             // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
             //  so they are currently ignored for the purposes of this lint.
-            ty::Param(..) | ty::Alias(ty::Projection, ..)
+            ty::Param(..) | ty::Alias(ty::Projection | ty::Inherent, ..)
                 if matches!(self.mode, CItemKind::Definition) =>
             {
                 FfiSafe
             }
 
             ty::Param(..)
-            | ty::Alias(ty::Projection, ..)
+            | ty::Alias(ty::Projection | ty::Inherent, ..)
             | ty::Infer(..)
             | ty::Bound(..)
             | ty::Error(_)

compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs

@@ -9,7 +9,7 @@ use crate::diagnostics::utils::{
     FieldInnerTy, FieldMap, HasFieldMap, SetOnce, SpannedOption, SubdiagnosticKind,
 };
 use proc_macro2::{Ident, Span, TokenStream};
-use quote::{format_ident, quote};
+use quote::{format_ident, quote, quote_spanned};
 use syn::Token;
 use syn::{parse_quote, spanned::Spanned, Attribute, Meta, Path, Type};
 use synstructure::{BindingInfo, Structure, VariantInfo};
@@ -251,7 +251,8 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
         let diag = &self.parent.diag;
 
         let field = binding_info.ast();
-        let field_binding = &binding_info.binding;
+        let mut field_binding = binding_info.binding.clone();
+        field_binding.set_span(field.ty.span());
 
         let ident = field.ident.as_ref().unwrap();
         let ident = format_ident!("{}", ident); // strip `r#` prefix, if present
@@ -284,9 +285,9 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                     name == "primary_span" && matches!(inner_ty, FieldInnerTy::Vec(_));
                 let (binding, needs_destructure) = if needs_clone {
                     // `primary_span` can accept a `Vec<Span>` so don't destructure that.
-                    (quote! { #field_binding.clone() }, false)
+                    (quote_spanned! {inner_ty.span()=> #field_binding.clone() }, false)
                 } else {
-                    (quote! { #field_binding }, true)
+                    (quote_spanned! {inner_ty.span()=> #field_binding }, true)
                 };
 
                 let generated_code = self

compiler/rustc_macros/src/diagnostics/subdiagnostic.rs

@@ -4,17 +4,16 @@ use crate::diagnostics::error::{
     invalid_attr, span_err, throw_invalid_attr, throw_span_err, DiagnosticDeriveError,
 };
 use crate::diagnostics::utils::{
-    build_field_mapping, is_doc_comment, new_code_ident,
-    report_error_if_not_applied_to_applicability, report_error_if_not_applied_to_span, FieldInfo,
-    FieldInnerTy, FieldMap, HasFieldMap, SetOnce, SpannedOption, SubdiagnosticKind,
+    build_field_mapping, build_suggestion_code, is_doc_comment, new_code_ident,
+    report_error_if_not_applied_to_applicability, report_error_if_not_applied_to_span,
+    should_generate_set_arg, AllowMultipleAlternatives, FieldInfo, FieldInnerTy, FieldMap,
+    HasFieldMap, SetOnce, SpannedOption, SubdiagnosticKind,
 };
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 use syn::{spanned::Spanned, Attribute, Meta, MetaList, Path};
 use synstructure::{BindingInfo, Structure, VariantInfo};
 
-use super::utils::{build_suggestion_code, AllowMultipleAlternatives};
-
 /// The central struct for constructing the `add_to_diagnostic` method from an annotated struct.
 pub(crate) struct SubdiagnosticDeriveBuilder {
     diag: syn::Ident,
@@ -210,19 +209,20 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
     }
 
     /// Generates the code for a field with no attributes.
-    fn generate_field_set_arg(&mut self, binding: &BindingInfo<'_>) -> TokenStream {
-        let ast = binding.ast();
-        assert_eq!(ast.attrs.len(), 0, "field with attribute used as diagnostic arg");
-
+    fn generate_field_set_arg(&mut self, binding_info: &BindingInfo<'_>) -> TokenStream {
         let diag = &self.parent.diag;
-        let ident = ast.ident.as_ref().unwrap();
-        // strip `r#` prefix, if present
-        let ident = format_ident!("{}", ident);
+
+        let field = binding_info.ast();
+        let mut field_binding = binding_info.binding.clone();
+        field_binding.set_span(field.ty.span());
+
+        let ident = field.ident.as_ref().unwrap();
+        let ident = format_ident!("{}", ident); // strip `r#` prefix, if present
 
         quote! {
             #diag.set_arg(
                 stringify!(#ident),
-                #binding
+                #field_binding
             );
         }
     }
@@ -399,7 +399,8 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
         clone_suggestion_code: bool,
     ) -> Result<TokenStream, DiagnosticDeriveError> {
         let span = attr.span().unwrap();
-        let ident = &list.path.segments.last().unwrap().ident;
+        let mut ident = list.path.segments.last().unwrap().ident.clone();
+        ident.set_span(info.ty.span());
         let name = ident.to_string();
         let name = name.as_str();
 
@@ -498,7 +499,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
             .variant
             .bindings()
             .iter()
-            .filter(|binding| !binding.ast().attrs.is_empty())
+            .filter(|binding| !should_generate_set_arg(binding.ast()))
             .map(|binding| self.generate_field_attr_code(binding, kind_stats))
             .collect();
 
@@ -580,7 +581,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
             .variant
             .bindings()
             .iter()
-            .filter(|binding| binding.ast().attrs.is_empty())
+            .filter(|binding| should_generate_set_arg(binding.ast()))
             .map(|binding| self.generate_field_set_arg(binding))
             .collect();
 

compiler/rustc_macros/src/diagnostics/utils.rs

@@ -207,6 +207,12 @@ impl<'ty> FieldInnerTy<'ty> {
             FieldInnerTy::Plain(..) => quote! { #inner },
         }
     }
+
+    pub fn span(&self) -> proc_macro2::Span {
+        match self {
+            FieldInnerTy::Option(ty) | FieldInnerTy::Vec(ty) | FieldInnerTy::Plain(ty) => ty.span(),
+        }
+    }
 }
 
 /// Field information passed to the builder. Deliberately omits attrs to discourage the
@@ -851,7 +857,8 @@ impl quote::IdentFragment for SubdiagnosticKind {
 /// Returns `true` if `field` should generate a `set_arg` call rather than any other diagnostic
 /// call (like `span_label`).
 pub(super) fn should_generate_set_arg(field: &Field) -> bool {
-    field.attrs.is_empty()
+    // Perhaps this should be an exhaustive list...
+    field.attrs.iter().all(|attr| is_doc_comment(attr))
 }
 
 pub(super) fn is_doc_comment(attr: &Attribute) -> bool {

compiler/rustc_middle/src/query/mod.rs

@@ -1821,6 +1821,16 @@ rustc_queries! {
         desc { "normalizing `{}`", goal.value.value }
     }
 
+    /// Do not call this query directly: invoke `normalize` instead.
+    query normalize_inherent_projection_ty(
+        goal: CanonicalProjectionGoal<'tcx>
+    ) -> Result<
+        &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
+        NoSolution,
+    > {
+        desc { "normalizing `{}`", goal.value.value }
+    }
+
     /// Do not call this query directly: invoke `try_normalize_erasing_regions` instead.
     query try_normalize_generic_arg_after_erasing_regions(
         goal: ParamEnvAnd<'tcx, GenericArg<'tcx>>

compiler/rustc_middle/src/ty/context.rs

@@ -1848,7 +1848,17 @@ impl<'tcx> TyCtxt<'tcx> {
         let substs = substs.into_iter().map(Into::into);
         #[cfg(debug_assertions)]
         {
-            let n = self.generics_of(_def_id).count();
+            let generics = self.generics_of(_def_id);
+
+            let n = if let DefKind::AssocTy = self.def_kind(_def_id)
+                && let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(_def_id))
+            {
+                // If this is an inherent projection.
+
+                generics.params.len() + 1
+            } else {
+                generics.count()
+            };
             assert_eq!(
                 (n, Some(n)),
                 substs.size_hint(),
@@ -2009,7 +2019,7 @@ impl<'tcx> TyCtxt<'tcx> {
         debug_assert_matches!(
             (kind, self.def_kind(alias_ty.def_id)),
             (ty::Opaque, DefKind::OpaqueTy)
-                | (ty::Projection, DefKind::AssocTy)
+                | (ty::Projection | ty::Inherent, DefKind::AssocTy)
                 | (ty::Opaque | ty::Projection, DefKind::ImplTraitPlaceholder)
         );
         self.mk_ty_from_kind(Alias(kind, alias_ty))

compiler/rustc_middle/src/ty/error.rs

@@ -265,7 +265,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
-            ty::Alias(ty::Projection, _) => "associated type".into(),
+            ty::Alias(ty::Projection | ty::Inherent, _) => "associated type".into(),
             ty::Param(p) => format!("type parameter `{p}`").into(),
             ty::Alias(ty::Opaque, ..) => if tcx.ty_is_opaque_future(self) { "future".into() } else { "opaque type".into() },
             ty::Error(_) => "type error".into(),
@@ -312,7 +312,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Tuple(..) => "tuple".into(),
             ty::Placeholder(..) => "higher-ranked type".into(),
             ty::Bound(..) => "bound type variable".into(),
-            ty::Alias(ty::Projection, _) => "associated type".into(),
+            ty::Alias(ty::Projection | ty::Inherent, _) => "associated type".into(),
             ty::Param(_) => "type parameter".into(),
             ty::Alias(ty::Opaque, ..) => "opaque type".into(),
         }

compiler/rustc_middle/src/ty/flags.rs

@@ -176,14 +176,14 @@ impl FlagComputation {
                 self.add_substs(substs);
             }
 
-            &ty::Alias(ty::Projection, data) => {
-                self.add_flags(TypeFlags::HAS_TY_PROJECTION);
-                self.add_alias_ty(data);
-            }
+            &ty::Alias(kind, data) => {
+                self.add_flags(match kind {
+                    ty::Projection => TypeFlags::HAS_TY_PROJECTION,
+                    ty::Inherent => TypeFlags::HAS_TY_INHERENT,
+                    ty::Opaque => TypeFlags::HAS_TY_OPAQUE,
+                });
 
-            &ty::Alias(ty::Opaque, ty::AliasTy { substs, .. }) => {
-                self.add_flags(TypeFlags::HAS_TY_OPAQUE);
-                self.add_substs(substs);
+                self.add_alias_ty(data);
             }
 
             &ty::Dynamic(obj, r, _) => {

compiler/rustc_middle/src/ty/inhabitedness/mod.rs

@@ -113,6 +113,12 @@ impl<'tcx> Ty<'tcx> {
             }
             Never => InhabitedPredicate::False,
             Param(_) | Alias(ty::Projection, _) => InhabitedPredicate::GenericType(self),
+            // FIXME(inherent_associated_types): Most likely we can just map to `GenericType` like above.
+            // However it's unclear if the substs passed to `InhabitedPredicate::subst` are of the correct
+            // format, i.e. don't contain parent substs. If you hit this case, please verify this beforehand.
+            Alias(ty::Inherent, _) => {
+                bug!("unimplemented: inhabitedness checking for inherent projections")
+            }
             Tuple(tys) if tys.is_empty() => InhabitedPredicate::True,
             // use a query for more complex cases
             Adt(..) | Array(..) | Tuple(_) => tcx.inhabited_predicate_type(self),

compiler/rustc_middle/src/ty/layout.rs

@@ -324,7 +324,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 let non_zero = !ty.is_unsafe_ptr();
                 let tail = tcx.struct_tail_erasing_lifetimes(pointee, param_env);
                 match tail.kind() {
-                    ty::Param(_) | ty::Alias(ty::Projection, _) => {
+                    ty::Param(_) | ty::Alias(ty::Projection | ty::Inherent, _) => {
                         debug_assert!(tail.has_non_region_param());
                         Ok(SizeSkeleton::Pointer { non_zero, tail: tcx.erase_regions(tail) })
                     }

compiler/rustc_middle/src/ty/mod.rs

@@ -1004,7 +1004,7 @@ impl<'tcx> Term<'tcx> {
         match self.unpack() {
             TermKind::Ty(ty) => match ty.kind() {
                 ty::Alias(kind, alias_ty) => match kind {
-                    AliasKind::Projection => Some(*alias_ty),
+                    AliasKind::Projection | AliasKind::Inherent => Some(*alias_ty),
                     AliasKind::Opaque => None,
                 },
                 _ => None,

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -729,7 +729,7 @@ pub trait PrettyPrinter<'tcx>:
             ty::Foreign(def_id) => {
                 p!(print_def_path(def_id, &[]));
             }
-            ty::Alias(ty::Projection, ref data) => {
+            ty::Alias(ty::Projection | ty::Inherent, ref data) => {
                 if !(self.should_print_verbose() || NO_QUERIES.with(|q| q.get()))
                     && self.tcx().is_impl_trait_in_trait(data.def_id)
                 {

compiler/rustc_middle/src/ty/relate.rs

@@ -550,6 +550,11 @@ pub fn super_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(tcx.mk_projection(projection_ty.def_id, projection_ty.substs))
         }
 
+        (&ty::Alias(ty::Inherent, a_data), &ty::Alias(ty::Inherent, b_data)) => {
+            let alias_ty = relation.relate(a_data, b_data)?;
+            Ok(tcx.mk_alias(ty::Inherent, tcx.mk_alias_ty(alias_ty.def_id, alias_ty.substs)))
+        }
+
         (
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, substs: a_substs, .. }),
             &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, substs: b_substs, .. }),

compiler/rustc_middle/src/ty/sty.rs

@@ -1190,9 +1190,9 @@ where
 
 /// Represents the projection of an associated type.
 ///
-/// For a projection, this would be `<Ty as Trait<...>>::N`.
-///
-/// For an opaque type, there is no explicit syntax.
+/// * For a projection, this would be `<Ty as Trait<...>>::N<...>`.
+/// * For an inherent projection, this would be `Ty::N<...>`.
+/// * For an opaque type, there is no explicit syntax.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct AliasTy<'tcx> {
@@ -1201,12 +1201,16 @@ pub struct AliasTy<'tcx> {
     /// For a projection, these are the substitutions for the trait and the
     /// GAT substitutions, if there are any.
     ///
+    /// For an inherent projection, they consist of the self type and the GAT substitutions,
+    /// if there are any.
+    ///
     /// For RPIT the substitutions are for the generics of the function,
     /// while for TAIT it is used for the generic parameters of the alias.
     pub substs: SubstsRef<'tcx>,
 
-    /// The `DefId` of the `TraitItem` for the associated type `N` if this is a projection,
-    /// or the `OpaqueType` item if this is an opaque.
+    /// The `DefId` of the `TraitItem` or `ImplItem` for the associated type `N` depending on whether
+    /// this is a projection or an inherent projection or the `DefId` of the `OpaqueType` item if
+    /// this is an opaque.
     ///
     /// During codegen, `tcx.type_of(def_id)` can be used to get the type of the
     /// underlying type if the type is an opaque.
@@ -1224,6 +1228,7 @@ pub struct AliasTy<'tcx> {
 impl<'tcx> AliasTy<'tcx> {
     pub fn kind(self, tcx: TyCtxt<'tcx>) -> ty::AliasKind {
         match tcx.def_kind(self.def_id) {
+            DefKind::AssocTy if let DefKind::Impl { of_trait: false } = tcx.def_kind(tcx.parent(self.def_id)) => ty::Inherent,
             DefKind::AssocTy | DefKind::ImplTraitPlaceholder => ty::Projection,
             DefKind::OpaqueTy => ty::Opaque,
             kind => bug!("unexpected DefKind in AliasTy: {kind:?}"),
@@ -1236,6 +1241,17 @@ impl<'tcx> AliasTy<'tcx> {
 }
 
 /// The following methods work only with associated type projections.
+impl<'tcx> AliasTy<'tcx> {
+    pub fn self_ty(self) -> Ty<'tcx> {
+        self.substs.type_at(0)
+    }
+
+    pub fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
+        tcx.mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.substs.iter().skip(1)))
+    }
+}
+
+/// The following methods work only with trait associated type projections.
 impl<'tcx> AliasTy<'tcx> {
     pub fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId {
         match tcx.def_kind(self.def_id) {
@@ -1274,13 +1290,28 @@ impl<'tcx> AliasTy<'tcx> {
         let def_id = self.trait_def_id(tcx);
         ty::TraitRef::new(tcx, def_id, self.substs.truncate_to(tcx, tcx.generics_of(def_id)))
     }
+}
 
-    pub fn self_ty(self) -> Ty<'tcx> {
-        self.substs.type_at(0)
-    }
+/// The following methods work only with inherent associated type projections.
+impl<'tcx> AliasTy<'tcx> {
+    /// Transform the substitutions to have the given `impl` substs as the base and the GAT substs on top of that.
+    ///
+    /// Does the following transformation:
+    ///
+    /// ```text
+    /// [Self, P_0...P_m] -> [I_0...I_n, P_0...P_m]
+    ///
+    ///     I_i impl subst
+    ///     P_j GAT subst
+    /// ```
+    pub fn rebase_substs_onto_impl(
+        self,
+        impl_substs: ty::SubstsRef<'tcx>,
+        tcx: TyCtxt<'tcx>,
+    ) -> ty::SubstsRef<'tcx> {
+        debug_assert_eq!(self.kind(tcx), ty::Inherent);
 
-    pub fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
-        tcx.mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.substs.iter().skip(1)))
+        tcx.mk_substs_from_iter(impl_substs.into_iter().chain(self.substs.into_iter().skip(1)))
     }
 }
 

compiler/rustc_middle/src/ty/visit.rs

@@ -49,6 +49,9 @@ pub trait TypeVisitableExt<'tcx>: TypeVisitable<TyCtxt<'tcx>> {
     fn has_projections(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_PROJECTION)
     }
+    fn has_inherent_projections(&self) -> bool {
+        self.has_type_flags(TypeFlags::HAS_TY_INHERENT)
+    }
     fn has_opaque_types(&self) -> bool {
         self.has_type_flags(TypeFlags::HAS_TY_OPAQUE)
     }

compiler/rustc_mir_transform/Cargo.toml

@@ -24,6 +24,8 @@ rustc_session = { path = "../rustc_session" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_span = { path = "../rustc_span" }
+rustc_fluent_macro = { path = "../rustc_fluent_macro" }
+rustc_macros = { path = "../rustc_macros" }
 
 [dev-dependencies]
 coverage_test_macros = { path = "src/coverage/test_macros" }

compiler/rustc_mir_transform/messages.ftl

@@ -0,0 +1,66 @@
+mir_transform_const_modify = attempting to modify a `const` item
+    .note = each usage of a `const` item creates a new temporary; the original `const` item will not be modified
+
+mir_transform_const_mut_borrow = taking a mutable reference to a `const` item
+    .note = each usage of a `const` item creates a new temporary
+    .note2 = the mutable reference will refer to this temporary, not the original `const` item
+    .note3 = mutable reference created due to call to this method
+
+mir_transform_const_defined_here = `const` item defined here
+
+mir_transform_unaligned_packed_ref = reference to packed field is unaligned
+    .note = packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
+    .note_ub = creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+    .help = copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+mir_transform_unused_unsafe = unnecessary `unsafe` block
+    .label = because it's nested under this `unsafe` block
+
+mir_transform_requires_unsafe = {$details} is unsafe and requires unsafe {$op_in_unsafe_fn_allowed ->
+    [true] function or block
+    *[false] block
+    }
+    .not_inherited = items do not inherit unsafety from separate enclosing items
+
+mir_transform_call_to_unsafe_label = call to unsafe function
+mir_transform_call_to_unsafe_note = consult the function's documentation for information on how to avoid undefined behavior
+mir_transform_use_of_asm_label = use of inline assembly
+mir_transform_use_of_asm_note = inline assembly is entirely unchecked and can cause undefined behavior
+mir_transform_initializing_valid_range_label = initializing type with `rustc_layout_scalar_valid_range` attr
+mir_transform_initializing_valid_range_note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
+mir_transform_const_ptr2int_label = cast of pointer to int
+mir_transform_const_ptr2int_note = casting pointers to integers in constants
+mir_transform_use_of_static_mut_label = use of mutable static
+mir_transform_use_of_static_mut_note = mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
+mir_transform_use_of_extern_static_label = use of extern static
+mir_transform_use_of_extern_static_note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+mir_transform_deref_ptr_label = dereference of raw pointer
+mir_transform_deref_ptr_note = raw pointers may be null, dangling or unaligned; they can violate aliasing rules and cause data races: all of these are undefined behavior
+mir_transform_union_access_label = access to union field
+mir_transform_union_access_note = the field may not be properly initialized: using uninitialized data will cause undefined behavior
+mir_transform_mutation_layout_constrained_label = mutation of layout constrained field
+mir_transform_mutation_layout_constrained_note = mutating layout constrained fields cannot statically be checked for valid values
+mir_transform_mutation_layout_constrained_borrow_label = borrow of layout constrained field with interior mutability
+mir_transform_mutation_layout_constrained_borrow_note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values
+mir_transform_target_feature_call_label = call to function with `#[target_feature]`
+mir_transform_target_feature_call_note = can only be called if the required target features are available
+
+mir_transform_unsafe_op_in_unsafe_fn = {$details} is unsafe and requires unsafe block (error E0133)
+
+mir_transform_arithmetic_overflow = this arithmetic operation will overflow
+mir_transform_operation_will_panic = this operation will panic at runtime
+
+mir_transform_ffi_unwind_call = call to {$foreign ->
+    [true] foreign function
+    *[false] function pointer
+    } with FFI-unwind ABI
+
+mir_transform_fn_item_ref = taking a reference to a function item does not give a function pointer
+    .suggestion = cast `{$ident}` to obtain a function pointer
+
+mir_transform_must_not_suspend = {$pre}`{$def_path}`{$post} held across a suspend point, but should not be
+    .label = the value is held across this suspend point
+    .note = {$reason}
+    .help = consider using a block (`{"{ ... }"}`) to shrink the value's scope, ending before the suspend point
+
+mir_transform_simd_shuffle_last_const = last argument of `simd_shuffle` is required to be a `const` item

compiler/rustc_mir_transform/src/check_const_item_mutation.rs

@@ -1,11 +1,12 @@
-use rustc_errors::{DiagnosticBuilder, DiagnosticMessage};
+use rustc_hir::HirId;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint::builtin::CONST_ITEM_MUTATION;
 use rustc_span::def_id::DefId;
+use rustc_span::Span;
 
-use crate::MirLint;
+use crate::{errors, MirLint};
 
 pub struct CheckConstItemMutation;
 
@@ -58,16 +59,14 @@ impl<'tcx> ConstMutationChecker<'_, 'tcx> {
         }
     }
 
-    fn lint_const_item_usage(
+    /// If we should lint on this usage, return the [`HirId`], source [`Span`]
+    /// and [`Span`] of the const item to use in the lint.
+    fn should_lint_const_item_usage(
         &self,
         place: &Place<'tcx>,
         const_item: DefId,
         location: Location,
-        msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'a mut DiagnosticBuilder<'b, ()>,
-        ) -> &'a mut DiagnosticBuilder<'b, ()>,
-    ) {
+    ) -> Option<(HirId, Span, Span)> {
         // Don't lint on borrowing/assigning when a dereference is involved.
         // If we 'leave' the temporary via a dereference, we must
         // be modifying something else
@@ -83,16 +82,9 @@ impl<'tcx> ConstMutationChecker<'_, 'tcx> {
                 .assert_crate_local()
                 .lint_root;
 
-            self.tcx.struct_span_lint_hir(
-                CONST_ITEM_MUTATION,
-                lint_root,
-                source_info.span,
-                msg,
-                |lint| {
-                    decorate(lint)
-                        .span_note(self.tcx.def_span(const_item), "`const` item defined here")
-                },
-            );
+            Some((lint_root, source_info.span, self.tcx.def_span(const_item)))
+        } else {
+            None
         }
     }
 }
@@ -104,10 +96,14 @@ impl<'tcx> Visitor<'tcx> for ConstMutationChecker<'_, 'tcx> {
             // Assigning directly to a constant (e.g. `FOO = true;`) is a hard error,
             // so emitting a lint would be redundant.
             if !lhs.projection.is_empty() {
-                if let Some(def_id) = self.is_const_item_without_destructor(lhs.local) {
-                    self.lint_const_item_usage(&lhs, def_id, loc, "attempting to modify a `const` item",|lint| {
-                        lint.note("each usage of a `const` item creates a new temporary; the original `const` item will not be modified")
-                    })
+                if let Some(def_id) = self.is_const_item_without_destructor(lhs.local)
+                    && let Some((lint_root, span, item)) = self.should_lint_const_item_usage(&lhs, def_id, loc) {
+                        self.tcx.emit_spanned_lint(
+                            CONST_ITEM_MUTATION,
+                            lint_root,
+                            span,
+                            errors::ConstMutate::Modify { konst: item }
+                        );
                 }
             }
             // We are looking for MIR of the form:
@@ -143,17 +139,22 @@ impl<'tcx> Visitor<'tcx> for ConstMutationChecker<'_, 'tcx> {
                 });
                 let lint_loc =
                     if method_did.is_some() { self.body.terminator_loc(loc.block) } else { loc };
-                self.lint_const_item_usage(place, def_id, lint_loc, "taking a mutable reference to a `const` item", |lint| {
-                    lint
-                        .note("each usage of a `const` item creates a new temporary")
-                        .note("the mutable reference will refer to this temporary, not the original `const` item");
 
-                    if let Some((method_did, _substs)) = method_did {
-                        lint.span_note(self.tcx.def_span(method_did), "mutable reference created due to call to this method");
-                    }
-
-                    lint
-                });
+                let method_call = if let Some((method_did, _)) = method_did {
+                    Some(self.tcx.def_span(method_did))
+                } else {
+                    None
+                };
+                if let Some((lint_root, span, item)) =
+                    self.should_lint_const_item_usage(place, def_id, lint_loc)
+                {
+                    self.tcx.emit_spanned_lint(
+                        CONST_ITEM_MUTATION,
+                        lint_root,
+                        span,
+                        errors::ConstMutate::MutBorrow { method_call, konst: item },
+                    );
+                }
             }
         }
         self.super_rvalue(rvalue, loc);

compiler/rustc_mir_transform/src/check_packed_ref.rs

@@ -1,10 +1,9 @@
-use rustc_errors::struct_span_err;
 use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, TyCtxt};
 
-use crate::util;
 use crate::MirLint;
+use crate::{errors, util};
 
 pub struct CheckPackedRef;
 
@@ -49,25 +48,7 @@ impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> {
                     // shouldn't do.
                     span_bug!(self.source_info.span, "builtin derive created an unaligned reference");
                 } else {
-                    struct_span_err!(
-                        self.tcx.sess,
-                        self.source_info.span,
-                        E0793,
-                        "reference to packed field is unaligned"
-                    )
-                    .note(
-                        "packed structs are only aligned by one byte, and many modern architectures \
-                        penalize unaligned field accesses"
-                    )
-                    .note(
-                        "creating a misaligned reference is undefined behavior (even if that \
-                        reference is never dereferenced)",
-                    ).help(
-                        "copy the field contents to a local variable, or replace the \
-                        reference with a raw pointer and use `read_unaligned`/`write_unaligned` \
-                        (loads and stores via `*p` must be properly aligned even when using raw pointers)"
-                    )
-                    .emit();
+                    self.tcx.sess.emit_err(errors::UnalignedPackedRef { span: self.source_info.span });
                 }
             }
         }

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -1,5 +1,4 @@
 use rustc_data_structures::unord::{UnordItems, UnordSet};
-use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -15,6 +14,8 @@ use rustc_session::lint::Level;
 
 use std::ops::Bound;
 
+use crate::errors;
+
 pub struct UnsafetyChecker<'a, 'tcx> {
     body: &'a Body<'tcx>,
     body_did: LocalDefId,
@@ -509,21 +510,12 @@ fn unsafety_check_result(tcx: TyCtxt<'_>, def: LocalDefId) -> &UnsafetyCheckResu
 
 fn report_unused_unsafe(tcx: TyCtxt<'_>, kind: UnusedUnsafe, id: HirId) {
     let span = tcx.sess.source_map().guess_head_span(tcx.hir().span(id));
-    let msg = "unnecessary `unsafe` block";
-    tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, msg, |lint| {
-        lint.span_label(span, msg);
-        match kind {
-            UnusedUnsafe::Unused => {}
-            UnusedUnsafe::InUnsafeBlock(id) => {
-                lint.span_label(
-                    tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
-                    "because it's nested under this `unsafe` block",
-                );
-            }
-        }
-
-        lint
-    });
+    let nested_parent = if let UnusedUnsafe::InUnsafeBlock(id) = kind {
+        Some(tcx.sess.source_map().guess_head_span(tcx.hir().span(id)))
+    } else {
+        None
+    };
+    tcx.emit_spanned_lint(UNUSED_UNSAFE, id, span, errors::UnusedUnsafe { span, nested_parent });
 }
 
 pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
@@ -537,26 +529,11 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let UnsafetyCheckResult { violations, unused_unsafes, .. } = tcx.unsafety_check_result(def_id);
 
     for &UnsafetyViolation { source_info, lint_root, kind, details } in violations.iter() {
-        let (description, note) = details.description_and_note();
+        let details = errors::RequiresUnsafeDetail { violation: details, span: source_info.span };
 
         match kind {
             UnsafetyViolationKind::General => {
-                // once
-                let unsafe_fn_msg = if unsafe_op_in_unsafe_fn_allowed(tcx, lint_root) {
-                    " function or"
-                } else {
-                    ""
-                };
-
-                let mut err = struct_span_err!(
-                    tcx.sess,
-                    source_info.span,
-                    E0133,
-                    "{} is unsafe and requires unsafe{} block",
-                    description,
-                    unsafe_fn_msg,
-                );
-                err.span_label(source_info.span, description).note(note);
+                let op_in_unsafe_fn_allowed = unsafe_op_in_unsafe_fn_allowed(tcx, lint_root);
                 let note_non_inherited = tcx.hir().parent_iter(lint_root).find(|(id, node)| {
                     if let Node::Expr(block) = node
                         && let ExprKind::Block(block, _) = block.kind
@@ -572,22 +549,23 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
                         false
                     }
                 });
-                if let Some((id, _)) = note_non_inherited {
-                    let span = tcx.hir().span(id);
-                    err.span_label(
-                        tcx.sess.source_map().guess_head_span(span),
-                        "items do not inherit unsafety from separate enclosing items",
-                    );
-                }
-
-                err.emit();
+                let enclosing = if let Some((id, _)) = note_non_inherited {
+                    Some(tcx.sess.source_map().guess_head_span(tcx.hir().span(id)))
+                } else {
+                    None
+                };
+                tcx.sess.emit_err(errors::RequiresUnsafe {
+                    span: source_info.span,
+                    enclosing,
+                    details,
+                    op_in_unsafe_fn_allowed,
+                });
             }
-            UnsafetyViolationKind::UnsafeFn => tcx.struct_span_lint_hir(
+            UnsafetyViolationKind::UnsafeFn => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 lint_root,
                 source_info.span,
-                format!("{} is unsafe and requires unsafe block (error E0133)", description,),
-                |lint| lint.span_label(source_info.span, description).note(note),
+                errors::UnsafeOpInUnsafeFn { details },
             ),
         }
     }

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -1,6 +1,8 @@
 //! Propagates constants for early reporting of statically known
 //! assertion failures
 
+use std::fmt::Debug;
+
 use either::Left;
 
 use rustc_const_eval::interpret::Immediate;
@@ -17,7 +19,6 @@ use rustc_middle::ty::InternalSubsts;
 use rustc_middle::ty::{
     self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt,
 };
-use rustc_session::lint;
 use rustc_span::Span;
 use rustc_target::abi::{HasDataLayout, Size, TargetDataLayout};
 use rustc_trait_selection::traits;
@@ -25,6 +26,7 @@ use rustc_trait_selection::traits;
 use crate::const_prop::CanConstProp;
 use crate::const_prop::ConstPropMachine;
 use crate::const_prop::ConstPropMode;
+use crate::errors::AssertLint;
 use crate::MirLint;
 
 /// The maximum number of bytes that we'll allocate space for a local or the return value.
@@ -311,18 +313,9 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         }
     }
 
-    fn report_assert_as_lint(
-        &self,
-        lint: &'static lint::Lint,
-        location: Location,
-        message: &'static str,
-        panic: AssertKind<impl std::fmt::Debug>,
-    ) {
-        let source_info = self.body().source_info(location);
+    fn report_assert_as_lint(&self, source_info: &SourceInfo, lint: AssertLint<impl Debug>) {
         if let Some(lint_root) = self.lint_root(*source_info) {
-            self.tcx.struct_span_lint_hir(lint, lint_root, source_info.span, message, |lint| {
-                lint.span_label(source_info.span, format!("{:?}", panic))
-            });
+            self.tcx.emit_spanned_lint(lint.lint(), lint_root, source_info.span, lint);
         }
     }
 
@@ -335,11 +328,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             // `AssertKind` only has an `OverflowNeg` variant, so make sure that is
             // appropriate to use.
             assert_eq!(op, UnOp::Neg, "Neg is the only UnOp that can overflow");
+            let source_info = self.body().source_info(location);
             self.report_assert_as_lint(
-                lint::builtin::ARITHMETIC_OVERFLOW,
-                location,
-                "this arithmetic operation will overflow",
-                AssertKind::OverflowNeg(val.to_const_int()),
+                source_info,
+                AssertLint::ArithmeticOverflow(
+                    source_info.span,
+                    AssertKind::OverflowNeg(val.to_const_int()),
+                ),
             );
             return None;
         }
@@ -370,23 +365,23 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             let r_bits = r.to_scalar().to_bits(right_size).ok();
             if r_bits.map_or(false, |b| b >= left_size.bits() as u128) {
                 debug!("check_binary_op: reporting assert for {:?}", location);
+                let source_info = self.body().source_info(location);
+                let panic = AssertKind::Overflow(
+                    op,
+                    match l {
+                        Some(l) => l.to_const_int(),
+                        // Invent a dummy value, the diagnostic ignores it anyway
+                        None => ConstInt::new(
+                            ScalarInt::try_from_uint(1_u8, left_size).unwrap(),
+                            left_ty.is_signed(),
+                            left_ty.is_ptr_sized_integral(),
+                        ),
+                    },
+                    r.to_const_int(),
+                );
                 self.report_assert_as_lint(
-                    lint::builtin::ARITHMETIC_OVERFLOW,
-                    location,
-                    "this arithmetic operation will overflow",
-                    AssertKind::Overflow(
-                        op,
-                        match l {
-                            Some(l) => l.to_const_int(),
-                            // Invent a dummy value, the diagnostic ignores it anyway
-                            None => ConstInt::new(
-                                ScalarInt::try_from_uint(1_u8, left_size).unwrap(),
-                                left_ty.is_signed(),
-                                left_ty.is_ptr_sized_integral(),
-                            ),
-                        },
-                        r.to_const_int(),
-                    ),
+                    source_info,
+                    AssertLint::ArithmeticOverflow(source_info.span, panic),
                 );
                 return None;
             }
@@ -398,11 +393,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 let (_res, overflow, _ty) = this.ecx.overflowing_binary_op(op, &l, &r)?;
                 Ok(overflow)
             })? {
+                let source_info = self.body().source_info(location);
                 self.report_assert_as_lint(
-                    lint::builtin::ARITHMETIC_OVERFLOW,
-                    location,
-                    "this arithmetic operation will overflow",
-                    AssertKind::Overflow(op, l.to_const_int(), r.to_const_int()),
+                    source_info,
+                    AssertLint::ArithmeticOverflow(
+                        source_info.span,
+                        AssertKind::Overflow(op, l.to_const_int(), r.to_const_int()),
+                    ),
                 );
                 return None;
             }
@@ -543,11 +540,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 // Need proper const propagator for these.
                 _ => return None,
             };
+            let source_info = self.body().source_info(location);
             self.report_assert_as_lint(
-                lint::builtin::UNCONDITIONAL_PANIC,
-                location,
-                "this operation will panic at runtime",
-                msg,
+                source_info,
+                AssertLint::UnconditionalPanic(source_info.span, msg),
             );
         }
 

compiler/rustc_mir_transform/src/errors.rs

@@ -0,0 +1,245 @@
+use rustc_errors::{
+    DecorateLint, DiagnosticBuilder, DiagnosticMessage, EmissionGuarantee, Handler, IntoDiagnostic,
+};
+use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
+use rustc_middle::mir::{AssertKind, UnsafetyViolationDetails};
+use rustc_session::lint::{self, Lint};
+use rustc_span::Span;
+
+#[derive(LintDiagnostic)]
+pub(crate) enum ConstMutate {
+    #[diag(mir_transform_const_modify)]
+    #[note]
+    Modify {
+        #[note(mir_transform_const_defined_here)]
+        konst: Span,
+    },
+    #[diag(mir_transform_const_mut_borrow)]
+    #[note]
+    #[note(mir_transform_note2)]
+    MutBorrow {
+        #[note(mir_transform_note3)]
+        method_call: Option<Span>,
+        #[note(mir_transform_const_defined_here)]
+        konst: Span,
+    },
+}
+
+#[derive(Diagnostic)]
+#[diag(mir_transform_unaligned_packed_ref, code = "E0793")]
+#[note]
+#[note(mir_transform_note_ub)]
+#[help]
+pub(crate) struct UnalignedPackedRef {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_unused_unsafe)]
+pub(crate) struct UnusedUnsafe {
+    #[label(mir_transform_unused_unsafe)]
+    pub span: Span,
+    #[label]
+    pub nested_parent: Option<Span>,
+}
+
+pub(crate) struct RequiresUnsafe {
+    pub span: Span,
+    pub details: RequiresUnsafeDetail,
+    pub enclosing: Option<Span>,
+    pub op_in_unsafe_fn_allowed: bool,
+}
+
+// The primary message for this diagnostic should be '{$label} is unsafe and...',
+// so we need to eagerly translate the label here, which isn't supported by the derive API
+// We could also exhaustively list out the primary messages for all unsafe violations,
+// but this would result in a lot of duplication.
+impl<'sess, G: EmissionGuarantee> IntoDiagnostic<'sess, G> for RequiresUnsafe {
+    #[track_caller]
+    fn into_diagnostic(self, handler: &'sess Handler) -> DiagnosticBuilder<'sess, G> {
+        let mut diag =
+            handler.struct_diagnostic(crate::fluent_generated::mir_transform_requires_unsafe);
+        diag.code(rustc_errors::DiagnosticId::Error("E0133".to_string()));
+        diag.set_span(self.span);
+        diag.span_label(self.span, self.details.label());
+        diag.note(self.details.note());
+        let desc = handler.eagerly_translate_to_string(self.details.label(), [].into_iter());
+        diag.set_arg("details", desc);
+        diag.set_arg("op_in_unsafe_fn_allowed", self.op_in_unsafe_fn_allowed);
+        if let Some(sp) = self.enclosing {
+            diag.span_label(sp, crate::fluent_generated::mir_transform_not_inherited);
+        }
+        diag
+    }
+}
+
+#[derive(Copy, Clone)]
+pub(crate) struct RequiresUnsafeDetail {
+    pub span: Span,
+    pub violation: UnsafetyViolationDetails,
+}
+
+impl RequiresUnsafeDetail {
+    fn note(self) -> DiagnosticMessage {
+        use UnsafetyViolationDetails::*;
+        match self.violation {
+            CallToUnsafeFunction => crate::fluent_generated::mir_transform_call_to_unsafe_note,
+            UseOfInlineAssembly => crate::fluent_generated::mir_transform_use_of_asm_note,
+            InitializingTypeWith => {
+                crate::fluent_generated::mir_transform_initializing_valid_range_note
+            }
+            CastOfPointerToInt => crate::fluent_generated::mir_transform_const_ptr2int_note,
+            UseOfMutableStatic => crate::fluent_generated::mir_transform_use_of_static_mut_note,
+            UseOfExternStatic => crate::fluent_generated::mir_transform_use_of_extern_static_note,
+            DerefOfRawPointer => crate::fluent_generated::mir_transform_deref_ptr_note,
+            AccessToUnionField => crate::fluent_generated::mir_transform_union_access_note,
+            MutationOfLayoutConstrainedField => {
+                crate::fluent_generated::mir_transform_mutation_layout_constrained_note
+            }
+            BorrowOfLayoutConstrainedField => {
+                crate::fluent_generated::mir_transform_mutation_layout_constrained_borrow_note
+            }
+            CallToFunctionWith => crate::fluent_generated::mir_transform_target_feature_call_note,
+        }
+    }
+
+    fn label(self) -> DiagnosticMessage {
+        use UnsafetyViolationDetails::*;
+        match self.violation {
+            CallToUnsafeFunction => crate::fluent_generated::mir_transform_call_to_unsafe_label,
+            UseOfInlineAssembly => crate::fluent_generated::mir_transform_use_of_asm_label,
+            InitializingTypeWith => {
+                crate::fluent_generated::mir_transform_initializing_valid_range_label
+            }
+            CastOfPointerToInt => crate::fluent_generated::mir_transform_const_ptr2int_label,
+            UseOfMutableStatic => crate::fluent_generated::mir_transform_use_of_static_mut_label,
+            UseOfExternStatic => crate::fluent_generated::mir_transform_use_of_extern_static_label,
+            DerefOfRawPointer => crate::fluent_generated::mir_transform_deref_ptr_label,
+            AccessToUnionField => crate::fluent_generated::mir_transform_union_access_label,
+            MutationOfLayoutConstrainedField => {
+                crate::fluent_generated::mir_transform_mutation_layout_constrained_label
+            }
+            BorrowOfLayoutConstrainedField => {
+                crate::fluent_generated::mir_transform_mutation_layout_constrained_borrow_label
+            }
+            CallToFunctionWith => crate::fluent_generated::mir_transform_target_feature_call_label,
+        }
+    }
+}
+
+pub(crate) struct UnsafeOpInUnsafeFn {
+    pub details: RequiresUnsafeDetail,
+}
+
+impl<'a> DecorateLint<'a, ()> for UnsafeOpInUnsafeFn {
+    #[track_caller]
+    fn decorate_lint<'b>(
+        self,
+        diag: &'b mut DiagnosticBuilder<'a, ()>,
+    ) -> &'b mut DiagnosticBuilder<'a, ()> {
+        let desc = diag
+            .handler()
+            .expect("lint should not yet be emitted")
+            .eagerly_translate_to_string(self.details.label(), [].into_iter());
+        diag.set_arg("details", desc);
+        diag.span_label(self.details.span, self.details.label());
+        diag.note(self.details.note());
+        diag
+    }
+
+    fn msg(&self) -> DiagnosticMessage {
+        crate::fluent_generated::mir_transform_unsafe_op_in_unsafe_fn
+    }
+}
+
+pub(crate) enum AssertLint<P> {
+    ArithmeticOverflow(Span, AssertKind<P>),
+    UnconditionalPanic(Span, AssertKind<P>),
+}
+
+impl<'a, P: std::fmt::Debug> DecorateLint<'a, ()> for AssertLint<P> {
+    fn decorate_lint<'b>(
+        self,
+        diag: &'b mut DiagnosticBuilder<'a, ()>,
+    ) -> &'b mut DiagnosticBuilder<'a, ()> {
+        diag.span_label(self.span(), format!("{:?}", self.panic()));
+        diag
+    }
+
+    fn msg(&self) -> DiagnosticMessage {
+        match self {
+            AssertLint::ArithmeticOverflow(..) => {
+                crate::fluent_generated::mir_transform_arithmetic_overflow
+            }
+            AssertLint::UnconditionalPanic(..) => {
+                crate::fluent_generated::mir_transform_operation_will_panic
+            }
+        }
+    }
+}
+
+impl<P> AssertLint<P> {
+    pub fn lint(&self) -> &'static Lint {
+        match self {
+            AssertLint::ArithmeticOverflow(..) => lint::builtin::ARITHMETIC_OVERFLOW,
+            AssertLint::UnconditionalPanic(..) => lint::builtin::UNCONDITIONAL_PANIC,
+        }
+    }
+    pub fn span(&self) -> Span {
+        match self {
+            AssertLint::ArithmeticOverflow(sp, _) | AssertLint::UnconditionalPanic(sp, _) => *sp,
+        }
+    }
+    pub fn panic(&self) -> &AssertKind<P> {
+        match self {
+            AssertLint::ArithmeticOverflow(_, p) | AssertLint::UnconditionalPanic(_, p) => p,
+        }
+    }
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_ffi_unwind_call)]
+pub(crate) struct FfiUnwindCall {
+    #[label(mir_transform_ffi_unwind_call)]
+    pub span: Span,
+    pub foreign: bool,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_fn_item_ref)]
+pub(crate) struct FnItemRef {
+    #[suggestion(code = "{sugg}", applicability = "unspecified")]
+    pub span: Span,
+    pub sugg: String,
+    pub ident: String,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(mir_transform_must_not_suspend)]
+pub(crate) struct MustNotSupend<'a> {
+    #[label]
+    pub yield_sp: Span,
+    #[subdiagnostic]
+    pub reason: Option<MustNotSuspendReason>,
+    #[help]
+    pub src_sp: Span,
+    pub pre: &'a str,
+    pub def_path: String,
+    pub post: &'a str,
+}
+
+#[derive(Subdiagnostic)]
+#[note(mir_transform_note)]
+pub(crate) struct MustNotSuspendReason {
+    #[primary_span]
+    pub span: Span,
+    pub reason: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(mir_transform_simd_shuffle_last_const)]
+pub(crate) struct SimdShuffleLastConst {
+    #[primary_span]
+    pub span: Span,
+}

compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -8,6 +8,8 @@ use rustc_session::lint::builtin::FFI_UNWIND_CALLS;
 use rustc_target::spec::abi::Abi;
 use rustc_target::spec::PanicStrategy;
 
+use crate::errors;
+
 fn abi_can_unwind(abi: Abi) -> bool {
     use Abi::*;
     match abi {
@@ -107,13 +109,13 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
                 .lint_root;
             let span = terminator.source_info.span;
 
-            let msg = match fn_def_id {
-                Some(_) => "call to foreign function with FFI-unwind ABI",
-                None => "call to function pointer with FFI-unwind ABI",
-            };
-            tcx.struct_span_lint_hir(FFI_UNWIND_CALLS, lint_root, span, msg, |lint| {
-                lint.span_label(span, msg)
-            });
+            let foreign = fn_def_id.is_some();
+            tcx.emit_spanned_lint(
+                FFI_UNWIND_CALLS,
+                lint_root,
+                span,
+                errors::FfiUnwindCall { span, foreign },
+            );
 
             tainted = true;
         }

compiler/rustc_mir_transform/src/function_item_references.rs

@@ -1,5 +1,4 @@
 use itertools::Itertools;
-use rustc_errors::Applicability;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
@@ -8,7 +7,7 @@ use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
 use rustc_span::{symbol::sym, Span};
 use rustc_target::spec::abi::Abi;
 
-use crate::MirLint;
+use crate::{errors, MirLint};
 
 pub struct FunctionItemReferences;
 
@@ -174,27 +173,21 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
         let num_args = fn_sig.inputs().map_bound(|inputs| inputs.len()).skip_binder();
         let variadic = if fn_sig.c_variadic() { ", ..." } else { "" };
         let ret = if fn_sig.output().skip_binder().is_unit() { "" } else { " -> _" };
-        self.tcx.struct_span_lint_hir(
+        let sugg = format!(
+            "{} as {}{}fn({}{}){}",
+            if params.is_empty() { ident.clone() } else { format!("{}::<{}>", ident, params) },
+            unsafety,
+            abi,
+            vec!["_"; num_args].join(", "),
+            variadic,
+            ret,
+        );
+
+        self.tcx.emit_spanned_lint(
             FUNCTION_ITEM_REFERENCES,
             lint_root,
             span,
-            "taking a reference to a function item does not give a function pointer",
-            |lint| {
-                lint.span_suggestion(
-                    span,
-                    format!("cast `{}` to obtain a function pointer", ident),
-                    format!(
-                        "{} as {}{}fn({}{}){}",
-                        if params.is_empty() { ident } else { format!("{}::<{}>", ident, params) },
-                        unsafety,
-                        abi,
-                        vec!["_"; num_args].join(", "),
-                        variadic,
-                        ret,
-                    ),
-                    Applicability::Unspecified,
-                )
-            },
+            errors::FnItemRef { span, sugg, ident },
         );
     }
 }

compiler/rustc_mir_transform/src/generator.rs

@@ -51,6 +51,7 @@
 //! Otherwise it drops all the values in scope at the last suspension point.
 
 use crate::deref_separator::deref_finder;
+use crate::errors;
 use crate::simplify;
 use crate::MirPass;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -1891,36 +1892,21 @@ fn check_must_not_suspend_def(
     data: SuspendCheckData<'_>,
 ) -> bool {
     if let Some(attr) = tcx.get_attr(def_id, sym::must_not_suspend) {
-        let msg = rustc_errors::DelayDm(|| {
-            format!(
-                "{}`{}`{} held across a suspend point, but should not be",
-                data.descr_pre,
-                tcx.def_path_str(def_id),
-                data.descr_post,
-            )
+        let reason = attr.value_str().map(|s| errors::MustNotSuspendReason {
+            span: data.source_span,
+            reason: s.as_str().to_string(),
         });
-        tcx.struct_span_lint_hir(
+        tcx.emit_spanned_lint(
             rustc_session::lint::builtin::MUST_NOT_SUSPEND,
             hir_id,
             data.source_span,
-            msg,
-            |lint| {
-                // add span pointing to the offending yield/await
-                lint.span_label(data.yield_span, "the value is held across this suspend point");
-
-                // Add optional reason note
-                if let Some(note) = attr.value_str() {
-                    // FIXME(guswynn): consider formatting this better
-                    lint.span_note(data.source_span, note.as_str());
-                }
-
-                // Add some quick suggestions on what to do
-                // FIXME: can `drop` work as a suggestion here as well?
-                lint.span_help(
-                    data.source_span,
-                    "consider using a block (`{ ... }`) \
-                    to shrink the value's scope, ending before the suspend point",
-                )
+            errors::MustNotSupend {
+                yield_sp: data.yield_span,
+                reason,
+                src_sp: data.source_span,
+                pre: data.descr_pre,
+                def_path: tcx.def_path_str(def_id),
+                post: data.descr_post,
             },
         );
 

compiler/rustc_mir_transform/src/lib.rs

@@ -1,4 +1,6 @@
 #![allow(rustc::potential_query_instability)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 #![feature(box_patterns)]
 #![feature(drain_filter)]
 #![feature(let_chains)]
@@ -69,6 +71,7 @@ pub mod dump_mir;
 mod early_otherwise_branch;
 mod elaborate_box_derefs;
 mod elaborate_drops;
+mod errors;
 mod ffi_unwind_calls;
 mod function_item_references;
 mod generator;
@@ -105,6 +108,11 @@ use rustc_const_eval::transform::promote_consts;
 use rustc_const_eval::transform::validate;
 use rustc_mir_dataflow::rustc_peek;
 
+use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
+use rustc_fluent_macro::fluent_messages;
+
+fluent_messages! { "../messages.ftl" }
+
 pub fn provide(providers: &mut Providers) {
     check_unsafety::provide(providers);
     coverage::query::provide(providers);

compiler/rustc_mir_transform/src/lower_intrinsics.rs

@@ -1,6 +1,6 @@
 //! Lowers intrinsic calls
 
-use crate::MirPass;
+use crate::{errors, MirPass};
 use rustc_middle::mir::*;
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -310,11 +310,7 @@ fn resolve_rust_intrinsic<'tcx>(
 }
 
 fn validate_simd_shuffle<'tcx>(tcx: TyCtxt<'tcx>, args: &[Operand<'tcx>], span: Span) {
-    match &args[2] {
-        Operand::Constant(_) => {} // all good
-        _ => {
-            let msg = "last argument of `simd_shuffle` is required to be a `const` item";
-            tcx.sess.span_err(span, msg);
-        }
+    if !matches!(args[2], Operand::Constant(_)) {
+        tcx.sess.emit_err(errors::SimdShuffleLastConst { span });
     }
 }

compiler/rustc_parse/src/parser/item.rs

@@ -1262,6 +1262,7 @@ impl<'a> Parser<'a> {
             }
         }
 
+        let prev_span = self.prev_token.span;
         let id = self.parse_ident()?;
         let mut generics = self.parse_generics()?;
         generics.where_clause = self.parse_where_clause()?;
@@ -1273,10 +1274,28 @@ impl<'a> Parser<'a> {
             (thin_vec![], false)
         } else {
             self.parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant()).map_err(
-                |mut e| {
-                    e.span_label(id.span, "while parsing this enum");
+                |mut err| {
+                    err.span_label(id.span, "while parsing this enum");
+                    if self.token == token::Colon {
+                        let snapshot = self.create_snapshot_for_diagnostic();
+                        self.bump();
+                        match self.parse_ty() {
+                            Ok(_) => {
+                                err.span_suggestion_verbose(
+                                    prev_span,
+                                    "perhaps you meant to use `struct` here",
+                                    "struct".to_string(),
+                                    Applicability::MaybeIncorrect,
+                                );
+                            }
+                            Err(e) => {
+                                e.cancel();
+                            }
+                        }
+                        self.restore_snapshot(snapshot);
+                    }
                     self.recover_stmt();
-                    e
+                    err
                 },
             )?
         };

compiler/rustc_privacy/src/lib.rs

@@ -243,6 +243,39 @@ where
                 // This will also visit substs if necessary, so we don't need to recurse.
                 return self.visit_projection_ty(proj);
             }
+            ty::Alias(ty::Inherent, data) => {
+                if self.def_id_visitor.skip_assoc_tys() {
+                    // Visitors searching for minimal visibility/reachability want to
+                    // conservatively approximate associated types like `Type::Alias`
+                    // as visible/reachable even if `Type` is private.
+                    // Ideally, associated types should be substituted in the same way as
+                    // free type aliases, but this isn't done yet.
+                    return ControlFlow::Continue(());
+                }
+
+                self.def_id_visitor.visit_def_id(
+                    data.def_id,
+                    "associated type",
+                    &LazyDefPathStr { def_id: data.def_id, tcx },
+                )?;
+
+                struct LazyDefPathStr<'tcx> {
+                    def_id: DefId,
+                    tcx: TyCtxt<'tcx>,
+                }
+                impl<'tcx> fmt::Display for LazyDefPathStr<'tcx> {
+                    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                        write!(f, "{}", self.tcx.def_path_str(self.def_id))
+                    }
+                }
+
+                // This will also visit substs if necessary, so we don't need to recurse.
+                return if self.def_id_visitor.shallow() {
+                    ControlFlow::Continue(())
+                } else {
+                    data.substs.iter().try_for_each(|subst| subst.visit_with(self))
+                };
+            }
             ty::Dynamic(predicates, ..) => {
                 // All traits in the list are considered the "primary" part of the type
                 // and are visited by shallow visitors.

compiler/rustc_trait_selection/messages.ftl

@@ -20,3 +20,5 @@ trait_selection_negative_positive_conflict = found both positive and negative im
     .negative_implementation_in_crate = negative implementation in crate `{$negative_impl_cname}`
     .positive_implementation_here = positive implementation here
     .positive_implementation_in_crate = positive implementation in crate `{$positive_impl_cname}`
+
+trait_selection_inherent_projection_normalization_overflow = overflow evaluating associated type `{$ty}`

compiler/rustc_trait_selection/src/errors.rs

@@ -89,3 +89,11 @@ impl IntoDiagnostic<'_> for NegativePositiveConflict<'_> {
         diag
     }
 }
+
+#[derive(Diagnostic)]
+#[diag(trait_selection_inherent_projection_normalization_overflow)]
+pub struct InherentProjectionNormalizationOverflow {
+    #[primary_span]
+    pub span: Span,
+    pub ty: String,
+}

compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs

@@ -33,7 +33,7 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_auto_trait<'tcx>(
         ty::Dynamic(..)
         | ty::Param(..)
         | ty::Foreign(..)
-        | ty::Alias(ty::Projection, ..)
+        | ty::Alias(ty::Projection | ty::Inherent, ..)
         | ty::Placeholder(..)
         | ty::Bound(..)
         | ty::Infer(_) => {

compiler/rustc_trait_selection/src/solve/trait_goals.rs

@@ -655,7 +655,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             ty::Dynamic(..)
             | ty::Param(..)
             | ty::Foreign(..)
-            | ty::Alias(ty::Projection, ..)
+            | ty::Alias(ty::Projection | ty::Inherent, ..)
             | ty::Placeholder(..) => Some(Err(NoSolution)),
 
             ty::Infer(_) | ty::Bound(_, _) => bug!("unexpected type `{self_ty}`"),

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -673,7 +673,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OrphanChecker<'tcx> {
             | ty::RawPtr(..)
             | ty::Never
             | ty::Tuple(..)
-            | ty::Alias(ty::Projection, ..) => self.found_non_local_ty(ty),
+            | ty::Alias(ty::Projection | ty::Inherent, ..) => self.found_non_local_ty(ty),
 
             ty::Param(..) => self.found_param_ty(ty),
 

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -1687,13 +1687,14 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 ty::Tuple(..) => Some(10),
                 ty::Param(..) => Some(11),
                 ty::Alias(ty::Projection, ..) => Some(12),
-                ty::Alias(ty::Opaque, ..) => Some(13),
-                ty::Never => Some(14),
-                ty::Adt(..) => Some(15),
-                ty::Generator(..) => Some(16),
-                ty::Foreign(..) => Some(17),
-                ty::GeneratorWitness(..) => Some(18),
-                ty::GeneratorWitnessMIR(..) => Some(19),
+                ty::Alias(ty::Inherent, ..) => Some(13),
+                ty::Alias(ty::Opaque, ..) => Some(14),
+                ty::Never => Some(15),
+                ty::Adt(..) => Some(16),
+                ty::Generator(..) => Some(17),
+                ty::Foreign(..) => Some(18),
+                ty::GeneratorWitness(..) => Some(19),
+                ty::GeneratorWitnessMIR(..) => Some(20),
                 ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error(_) => None,
             }
         }

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -49,7 +49,8 @@ pub use self::object_safety::astconv_object_safety_violations;
 pub use self::object_safety::is_vtable_safe_method;
 pub use self::object_safety::MethodViolationCode;
 pub use self::object_safety::ObjectSafetyViolation;
-pub use self::project::{normalize_projection_type, NormalizeExt};
+pub use self::project::NormalizeExt;
+pub use self::project::{normalize_inherent_projection, normalize_projection_type};
 pub use self::select::{EvaluationCache, SelectionCache, SelectionContext};
 pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
 pub use self::specialize::specialization_graph::FutureCompatOverlapError;

compiler/rustc_trait_selection/src/traits/project.rs

@@ -16,6 +16,7 @@ use super::{
 };
 use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
 
+use crate::errors::InherentProjectionNormalizationOverflow;
 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime};
 use crate::traits::error_reporting::TypeErrCtxtExt as _;
@@ -370,10 +371,14 @@ pub(crate) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>(
     reveal: Reveal,
 ) -> bool {
     match reveal {
-        Reveal::UserFacing => value
-            .has_type_flags(ty::TypeFlags::HAS_TY_PROJECTION | ty::TypeFlags::HAS_CT_PROJECTION),
+        Reveal::UserFacing => value.has_type_flags(
+            ty::TypeFlags::HAS_TY_PROJECTION
+                | ty::TypeFlags::HAS_TY_INHERENT
+                | ty::TypeFlags::HAS_CT_PROJECTION,
+        ),
         Reveal::All => value.has_type_flags(
             ty::TypeFlags::HAS_TY_PROJECTION
+                | ty::TypeFlags::HAS_TY_INHERENT
                 | ty::TypeFlags::HAS_TY_OPAQUE
                 | ty::TypeFlags::HAS_CT_PROJECTION,
         ),
@@ -616,6 +621,51 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                 );
                 normalized_ty
             }
+
+            ty::Inherent if !data.has_escaping_bound_vars() => {
+                // This branch is *mostly* just an optimization: when we don't
+                // have escaping bound vars, we don't need to replace them with
+                // placeholders (see branch below). *Also*, we know that we can
+                // register an obligation to *later* project, since we know
+                // there won't be bound vars there.
+
+                let data = data.fold_with(self);
+
+                // FIXME(inherent_associated_types): Do we need to honor `self.eager_inference_replacement`
+                // here like `ty::Projection`?
+                normalize_inherent_projection(
+                    self.selcx,
+                    self.param_env,
+                    data,
+                    self.cause.clone(),
+                    self.depth,
+                    &mut self.obligations,
+                )
+            }
+
+            ty::Inherent => {
+                let infcx = self.selcx.infcx;
+                let (data, mapped_regions, mapped_types, mapped_consts) =
+                    BoundVarReplacer::replace_bound_vars(infcx, &mut self.universes, data);
+                let data = data.fold_with(self);
+                let ty = normalize_inherent_projection(
+                    self.selcx,
+                    self.param_env,
+                    data,
+                    self.cause.clone(),
+                    self.depth,
+                    &mut self.obligations,
+                );
+
+                PlaceholderReplacer::replace_placeholders(
+                    infcx,
+                    mapped_regions,
+                    mapped_types,
+                    mapped_consts,
+                    &self.universes,
+                    ty,
+                )
+            }
         }
     }
 
@@ -1204,6 +1254,115 @@ fn normalize_to_error<'a, 'tcx>(
     Normalized { value: new_value, obligations: vec![trait_obligation] }
 }
 
+/// Confirm and normalize the given inherent projection.
+#[instrument(level = "debug", skip(selcx, param_env, cause, obligations))]
+pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
+    selcx: &'a mut SelectionContext<'b, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    alias_ty: ty::AliasTy<'tcx>,
+    cause: ObligationCause<'tcx>,
+    depth: usize,
+    obligations: &mut Vec<PredicateObligation<'tcx>>,
+) -> Ty<'tcx> {
+    let tcx = selcx.tcx();
+
+    if !tcx.recursion_limit().value_within_limit(depth) {
+        // Halt compilation because it is important that overflows never be masked.
+        tcx.sess.emit_fatal(InherentProjectionNormalizationOverflow {
+            span: cause.span,
+            ty: alias_ty.to_string(),
+        });
+    }
+
+    let substs = compute_inherent_assoc_ty_substs(
+        selcx,
+        param_env,
+        alias_ty,
+        cause.clone(),
+        depth,
+        obligations,
+    );
+
+    // Register the obligations arising from the impl and from the associated type itself.
+    let predicates = tcx.predicates_of(alias_ty.def_id).instantiate(tcx, substs);
+    for (predicate, span) in predicates {
+        let predicate = normalize_with_depth_to(
+            selcx,
+            param_env,
+            cause.clone(),
+            depth + 1,
+            predicate,
+            obligations,
+        );
+
+        let nested_cause = ObligationCause::new(
+            cause.span,
+            cause.body_id,
+            // FIXME(inherent_associated_types): Since we can't pass along the self type to the
+            // cause code, inherent projections will be printed with identity substitutions in
+            // diagnostics which is not ideal.
+            // Consider creating separate cause codes for this specific situation.
+            if span.is_dummy() {
+                super::ItemObligation(alias_ty.def_id)
+            } else {
+                super::BindingObligation(alias_ty.def_id, span)
+            },
+        );
+
+        obligations.push(Obligation::with_depth(
+            tcx,
+            nested_cause,
+            depth + 1,
+            param_env,
+            predicate,
+        ));
+    }
+
+    let ty = tcx.type_of(alias_ty.def_id).subst(tcx, substs);
+
+    let mut ty = selcx.infcx.resolve_vars_if_possible(ty);
+    if ty.has_projections() {
+        ty = normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, ty, obligations);
+    }
+
+    ty
+}
+
+pub fn compute_inherent_assoc_ty_substs<'a, 'b, 'tcx>(
+    selcx: &'a mut SelectionContext<'b, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    alias_ty: ty::AliasTy<'tcx>,
+    cause: ObligationCause<'tcx>,
+    depth: usize,
+    obligations: &mut Vec<PredicateObligation<'tcx>>,
+) -> ty::SubstsRef<'tcx> {
+    let tcx = selcx.tcx();
+
+    let impl_def_id = tcx.parent(alias_ty.def_id);
+    let impl_substs = selcx.infcx.fresh_substs_for_item(cause.span, impl_def_id);
+
+    let impl_ty = tcx.type_of(impl_def_id).subst(tcx, impl_substs);
+    let impl_ty =
+        normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, impl_ty, obligations);
+
+    // Infer the generic parameters of the impl by unifying the
+    // impl type with the self type of the projection.
+    let self_ty = alias_ty.self_ty();
+    match selcx.infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, impl_ty, self_ty) {
+        Ok(mut ok) => obligations.append(&mut ok.obligations),
+        Err(_) => {
+            tcx.sess.delay_span_bug(
+                cause.span,
+                format!(
+                    "{self_ty:?} was a subtype of {impl_ty:?} during selection but now it is not"
+                ),
+            );
+        }
+    }
+
+    alias_ty.rebase_substs_onto_impl(impl_substs, tcx)
+}
+
 enum Projected<'tcx> {
     Progress(Progress<'tcx>),
     NoProgress(ty::Term<'tcx>),

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -257,11 +257,11 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
 
             ty::Opaque => ty.try_super_fold_with(self)?,
 
-            ty::Projection => {
+            ty::Projection | ty::Inherent => {
                 // See note in `rustc_trait_selection::traits::project`
 
-                let tcx = self.infcx.tcx;
                 let infcx = self.infcx;
+                let tcx = infcx.tcx;
                 // Just an optimization: When we don't have escaping bound vars,
                 // we don't need to replace them with placeholders.
                 let (data, maps) = if data.has_escaping_bound_vars() {
@@ -276,12 +276,15 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
                 let mut orig_values = OriginalQueryValues::default();
                 // HACK(matthewjasper) `'static` is special-cased in selection,
                 // so we cannot canonicalize it.
-                let c_data = self
-                    .infcx
+                let c_data = infcx
                     .canonicalize_query_keep_static(self.param_env.and(data), &mut orig_values);
                 debug!("QueryNormalizer: c_data = {:#?}", c_data);
                 debug!("QueryNormalizer: orig_values = {:#?}", orig_values);
-                let result = tcx.normalize_projection_ty(c_data)?;
+                let result = match kind {
+                    ty::Projection => tcx.normalize_projection_ty(c_data),
+                    ty::Inherent => tcx.normalize_inherent_projection_ty(c_data),
+                    _ => unreachable!(),
+                }?;
                 // We don't expect ambiguity.
                 if result.is_ambiguous() {
                     // Rustdoc normalizes possibly not well-formed types, so only
@@ -294,8 +297,8 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
                     }
                     return Err(NoSolution);
                 }
-                let InferOk { value: result, obligations } =
-                    self.infcx.instantiate_query_response_and_region_obligations(
+                let InferOk { value: result, obligations } = infcx
+                    .instantiate_query_response_and_region_obligations(
                         self.cause,
                         self.param_env,
                         &orig_values,

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -498,7 +498,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     // this trait and type.
                 }
                 ty::Param(..)
-                | ty::Alias(ty::Projection, ..)
+                | ty::Alias(ty::Projection | ty::Inherent, ..)
                 | ty::Placeholder(..)
                 | ty::Bound(..) => {
                     // In these cases, we don't know what the actual

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -1268,7 +1268,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
                 // If we have a projection type, make sure to normalize it so we replace it
                 // with a fresh infer variable
-                ty::Alias(ty::Projection, ..) => {
+                ty::Alias(ty::Projection | ty::Inherent, ..) => {
                     let predicate = normalize_with_depth_to(
                         self,
                         obligation.param_env,

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2315,7 +2315,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             | ty::Dynamic(..)
             | ty::Param(..)
             | ty::Foreign(..)
-            | ty::Alias(ty::Projection, ..)
+            | ty::Alias(ty::Projection | ty::Inherent, ..)
             | ty::Bound(..)
             | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
                 bug!("asked to assemble constituent types of unexpected type: {:?}", t);

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -58,15 +58,8 @@ pub fn obligations<'tcx>(
         GenericArgKind::Lifetime(..) => return Some(Vec::new()),
     };
 
-    let mut wf = WfPredicates {
-        tcx: infcx.tcx,
-        param_env,
-        body_id,
-        span,
-        out: vec![],
-        recursion_depth,
-        item: None,
-    };
+    let mut wf =
+        WfPredicates { infcx, param_env, body_id, span, out: vec![], recursion_depth, item: None };
     wf.compute(arg);
     debug!("wf::obligations({:?}, body_id={:?}) = {:?}", arg, body_id, wf.out);
 
@@ -91,7 +84,7 @@ pub fn unnormalized_obligations<'tcx>(
     debug_assert_eq!(arg, infcx.resolve_vars_if_possible(arg));
 
     let mut wf = WfPredicates {
-        tcx: infcx.tcx,
+        infcx,
         param_env,
         body_id: CRATE_DEF_ID,
         span: DUMMY_SP,
@@ -116,7 +109,7 @@ pub fn trait_obligations<'tcx>(
     item: &'tcx hir::Item<'tcx>,
 ) -> Vec<traits::PredicateObligation<'tcx>> {
     let mut wf = WfPredicates {
-        tcx: infcx.tcx,
+        infcx,
         param_env,
         body_id,
         span,
@@ -138,7 +131,7 @@ pub fn predicate_obligations<'tcx>(
     span: Span,
 ) -> Vec<traits::PredicateObligation<'tcx>> {
     let mut wf = WfPredicates {
-        tcx: infcx.tcx,
+        infcx,
         param_env,
         body_id,
         span,
@@ -190,8 +183,8 @@ pub fn predicate_obligations<'tcx>(
     wf.normalize(infcx)
 }
 
-struct WfPredicates<'tcx> {
-    tcx: TyCtxt<'tcx>,
+struct WfPredicates<'a, 'tcx> {
+    infcx: &'a InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     body_id: LocalDefId,
     span: Span,
@@ -290,9 +283,9 @@ fn extend_cause_with_original_assoc_item_obligation<'tcx>(
     }
 }
 
-impl<'tcx> WfPredicates<'tcx> {
+impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx> {
-        self.tcx
+        self.infcx.tcx
     }
 
     fn cause(&self, code: traits::ObligationCauseCode<'tcx>) -> traits::ObligationCause<'tcx> {
@@ -325,7 +318,7 @@ impl<'tcx> WfPredicates<'tcx> {
 
     /// Pushes the obligations required for `trait_ref` to be WF into `self.out`.
     fn compute_trait_pred(&mut self, trait_pred: &ty::TraitPredicate<'tcx>, elaborate: Elaborate) {
-        let tcx = self.tcx;
+        let tcx = self.tcx();
         let trait_ref = &trait_pred.trait_ref;
 
         // Negative trait predicates don't require supertraits to hold, just
@@ -369,7 +362,6 @@ impl<'tcx> WfPredicates<'tcx> {
             self.out.extend(obligations);
         }
 
-        let tcx = self.tcx();
         self.out.extend(
             trait_ref
                 .substs
@@ -436,13 +428,45 @@ impl<'tcx> WfPredicates<'tcx> {
         let obligations = self.nominal_obligations_without_const(data.def_id, data.substs);
         self.out.extend(obligations);
 
+        self.compute_projection_substs(data.substs);
+    }
+
+    fn compute_inherent_projection(&mut self, data: ty::AliasTy<'tcx>) {
+        // An inherent projection is well-formed if
+        //
+        // (a) its predicates hold (*)
+        // (b) its substs are wf
+        //
+        // (*) The predicates of an inherent associated type include the
+        //     predicates of the impl that it's contained in.
+
+        if !data.self_ty().has_escaping_bound_vars() {
+            // FIXME(inherent_associated_types): Should this happen inside of a snapshot?
+            // FIXME(inherent_associated_types): This is incompatible with the new solver and lazy norm!
+            let substs = traits::project::compute_inherent_assoc_ty_substs(
+                &mut traits::SelectionContext::new(self.infcx),
+                self.param_env,
+                data,
+                self.cause(traits::WellFormed(None)),
+                self.recursion_depth,
+                &mut self.out,
+            );
+            // Inherent projection types do not require const predicates.
+            let obligations = self.nominal_obligations_without_const(data.def_id, substs);
+            self.out.extend(obligations);
+        }
+
+        self.compute_projection_substs(data.substs);
+    }
+
+    fn compute_projection_substs(&mut self, substs: SubstsRef<'tcx>) {
         let tcx = self.tcx();
         let cause = self.cause(traits::WellFormed(None));
         let param_env = self.param_env;
         let depth = self.recursion_depth;
 
         self.out.extend(
-            data.substs
+            substs
                 .iter()
                 .filter(|arg| {
                     matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
@@ -464,9 +488,9 @@ impl<'tcx> WfPredicates<'tcx> {
         if !subty.has_escaping_bound_vars() {
             let cause = self.cause(cause);
             let trait_ref =
-                ty::TraitRef::from_lang_item(self.tcx, LangItem::Sized, cause.span, [subty]);
+                ty::TraitRef::from_lang_item(self.tcx(), LangItem::Sized, cause.span, [subty]);
             self.out.push(traits::Obligation::with_depth(
-                self.tcx,
+                self.tcx(),
                 cause,
                 self.recursion_depth,
                 self.param_env,
@@ -605,6 +629,10 @@ impl<'tcx> WfPredicates<'tcx> {
                     walker.skip_current_subtree(); // Subtree handled by compute_projection.
                     self.compute_projection(data);
                 }
+                ty::Alias(ty::Inherent, data) => {
+                    walker.skip_current_subtree(); // Subtree handled by compute_inherent_projection.
+                    self.compute_inherent_projection(data);
+                }
 
                 ty::Adt(def, substs) => {
                     // WfNominalType
@@ -697,7 +725,7 @@ impl<'tcx> WfPredicates<'tcx> {
                     // All of the requirements on type parameters
                     // have already been checked for `impl Trait` in
                     // return position. We do need to check type-alias-impl-trait though.
-                    if self.tcx.is_type_alias_impl_trait(def_id) {
+                    if self.tcx().is_type_alias_impl_trait(def_id) {
                         let obligations = self.nominal_obligations(def_id, substs);
                         self.out.extend(obligations);
                     }
@@ -767,15 +795,15 @@ impl<'tcx> WfPredicates<'tcx> {
         substs: SubstsRef<'tcx>,
         remap_constness: bool,
     ) -> Vec<traits::PredicateObligation<'tcx>> {
-        let predicates = self.tcx.predicates_of(def_id);
+        let predicates = self.tcx().predicates_of(def_id);
         let mut origins = vec![def_id; predicates.predicates.len()];
         let mut head = predicates;
         while let Some(parent) = head.parent {
-            head = self.tcx.predicates_of(parent);
+            head = self.tcx().predicates_of(parent);
             origins.extend(iter::repeat(parent).take(head.predicates.len()));
         }
 
-        let predicates = predicates.instantiate(self.tcx, substs);
+        let predicates = predicates.instantiate(self.tcx(), substs);
         trace!("{:#?}", predicates);
         debug_assert_eq!(predicates.predicates.len(), origins.len());
 
@@ -788,10 +816,10 @@ impl<'tcx> WfPredicates<'tcx> {
                 };
                 let cause = self.cause(code);
                 if remap_constness {
-                    pred = pred.without_const(self.tcx);
+                    pred = pred.without_const(self.tcx());
                 }
                 traits::Obligation::with_depth(
-                    self.tcx,
+                    self.tcx(),
                     cause,
                     self.recursion_depth,
                     self.param_env,
@@ -856,7 +884,7 @@ impl<'tcx> WfPredicates<'tcx> {
         // Note: in fact we only permit builtin traits, not `Bar<'d>`, I
         // am looking forward to the future here.
         if !data.has_escaping_bound_vars() && !region.has_escaping_bound_vars() {
-            let implicit_bounds = object_region_bounds(self.tcx, data);
+            let implicit_bounds = object_region_bounds(self.tcx(), data);
 
             let explicit_bound = region;
 
@@ -866,7 +894,7 @@ impl<'tcx> WfPredicates<'tcx> {
                 let outlives =
                     ty::Binder::dummy(ty::OutlivesPredicate(explicit_bound, implicit_bound));
                 self.out.push(traits::Obligation::with_depth(
-                    self.tcx,
+                    self.tcx(),
                     cause,
                     self.recursion_depth,
                     self.param_env,

compiler/rustc_traits/src/chalk/lowering.rs

@@ -372,6 +372,7 @@ impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
                     substitution: substs.lower_into(interner),
                 }))
             }
+            ty::Alias(ty::Inherent, _) => unimplemented!(),
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
                 chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy {
                     opaque_ty_id: chalk_ir::OpaqueTyId(def_id),

compiler/rustc_traits/src/normalize_projection_ty.rs

@@ -10,7 +10,7 @@ use rustc_trait_selection::traits::{self, ObligationCause, SelectionContext};
 use std::sync::atomic::Ordering;
 
 pub(crate) fn provide(p: &mut Providers) {
-    *p = Providers { normalize_projection_ty, ..*p };
+    *p = Providers { normalize_projection_ty, normalize_inherent_projection_ty, ..*p };
 }
 
 fn normalize_projection_ty<'tcx>(
@@ -42,3 +42,30 @@ fn normalize_projection_ty<'tcx>(
         },
     )
 }
+
+fn normalize_inherent_projection_ty<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    goal: CanonicalProjectionGoal<'tcx>,
+) -> Result<&'tcx Canonical<'tcx, QueryResponse<'tcx, NormalizationResult<'tcx>>>, NoSolution> {
+    debug!("normalize_provider(goal={:#?})", goal);
+
+    tcx.infer_ctxt().enter_canonical_trait_query(
+        &goal,
+        |ocx, ParamEnvAnd { param_env, value: goal }| {
+            let selcx = &mut SelectionContext::new(ocx.infcx);
+            let cause = ObligationCause::dummy();
+            let mut obligations = vec![];
+            let answer = traits::normalize_inherent_projection(
+                selcx,
+                param_env,
+                goal,
+                cause,
+                0,
+                &mut obligations,
+            );
+            ocx.register_obligations(obligations);
+
+            Ok(NormalizationResult { normalized_ty: answer })
+        },
+    )
+}

compiler/rustc_ty_utils/src/instance.rs

@@ -194,21 +194,18 @@ fn resolve_associated_item<'tcx>(
             })
         }
         traits::ImplSource::Future(future_data) => {
-            if cfg!(debug_assertions) && tcx.item_name(trait_item_id) != sym::poll {
-                // For compiler developers who'd like to add new items to `Future`,
-                // you either need to generate a shim body, or perhaps return
-                // `InstanceDef::Item` pointing to a trait default method body if
-                // it is given a default implementation by the trait.
-                span_bug!(
-                    tcx.def_span(future_data.generator_def_id),
-                    "no definition for `{trait_ref}::{}` for built-in async generator type",
-                    tcx.item_name(trait_item_id)
-                )
+            if Some(trait_item_id) == tcx.lang_items().future_poll_fn() {
+                // `Future::poll` is generated by the compiler.
+                Some(Instance {
+                    def: ty::InstanceDef::Item(future_data.generator_def_id),
+                    substs: future_data.substs,
+                })
+            } else {
+                // All other methods are default methods of the `Future` trait.
+                // (this assumes that `ImplSource::Future` is only used for methods on `Future`)
+                debug_assert!(tcx.impl_defaultness(trait_item_id).has_value());
+                Some(Instance::new(trait_item_id, rcvr_substs))
             }
-            Some(Instance {
-                def: ty::InstanceDef::Item(future_data.generator_def_id),
-                substs: future_data.substs,
-            })
         }
         traits::ImplSource::Closure(closure_data) => {
             if cfg!(debug_assertions)

compiler/rustc_type_ir/src/lib.rs

@@ -229,29 +229,32 @@ bitflags! {
 
         /// Does this have `Projection`?
         const HAS_TY_PROJECTION           = 1 << 10;
+        /// Does this have `Inherent`?
+        const HAS_TY_INHERENT             = 1 << 11;
         /// Does this have `Opaque`?
-        const HAS_TY_OPAQUE               = 1 << 11;
+        const HAS_TY_OPAQUE               = 1 << 12;
         /// Does this have `ConstKind::Unevaluated`?
-        const HAS_CT_PROJECTION           = 1 << 12;
+        const HAS_CT_PROJECTION           = 1 << 13;
 
         /// Could this type be normalized further?
         const HAS_PROJECTION              = TypeFlags::HAS_TY_PROJECTION.bits
                                           | TypeFlags::HAS_TY_OPAQUE.bits
+                                          | TypeFlags::HAS_TY_INHERENT.bits
                                           | TypeFlags::HAS_CT_PROJECTION.bits;
 
         /// Is an error type/const reachable?
-        const HAS_ERROR                   = 1 << 13;
+        const HAS_ERROR                   = 1 << 14;
 
         /// Does this have any region that "appears free" in the type?
         /// Basically anything but `ReLateBound` and `ReErased`.
-        const HAS_FREE_REGIONS            = 1 << 14;
+        const HAS_FREE_REGIONS            = 1 << 15;
 
         /// Does this have any `ReLateBound` regions?
-        const HAS_RE_LATE_BOUND           = 1 << 15;
+        const HAS_RE_LATE_BOUND           = 1 << 16;
         /// Does this have any `Bound` types?
-        const HAS_TY_LATE_BOUND           = 1 << 16;
+        const HAS_TY_LATE_BOUND           = 1 << 17;
         /// Does this have any `ConstKind::Bound` consts?
-        const HAS_CT_LATE_BOUND           = 1 << 17;
+        const HAS_CT_LATE_BOUND           = 1 << 18;
         /// Does this have any bound variables?
         /// Used to check if a global bound is safe to evaluate.
         const HAS_LATE_BOUND              = TypeFlags::HAS_RE_LATE_BOUND.bits
@@ -259,20 +262,20 @@ bitflags! {
                                           | TypeFlags::HAS_CT_LATE_BOUND.bits;
 
         /// Does this have any `ReErased` regions?
-        const HAS_RE_ERASED               = 1 << 18;
+        const HAS_RE_ERASED               = 1 << 19;
 
         /// Does this value have parameters/placeholders/inference variables which could be
         /// replaced later, in a way that would change the results of `impl` specialization?
-        const STILL_FURTHER_SPECIALIZABLE = 1 << 19;
+        const STILL_FURTHER_SPECIALIZABLE = 1 << 20;
 
         /// Does this value have `InferTy::FreshTy/FreshIntTy/FreshFloatTy`?
-        const HAS_TY_FRESH                = 1 << 20;
+        const HAS_TY_FRESH                = 1 << 21;
 
         /// Does this value have `InferConst::Fresh`?
-        const HAS_CT_FRESH                = 1 << 21;
+        const HAS_CT_FRESH                = 1 << 22;
 
         /// Does this have `Generator` or `GeneratorWitness`?
-        const HAS_TY_GENERATOR            = 1 << 22;
+        const HAS_TY_GENERATOR            = 1 << 23;
     }
 }
 

compiler/rustc_type_ir/src/sty.rs

@@ -37,6 +37,7 @@ pub enum DynKind {
 #[derive(Encodable, Decodable, HashStable_Generic)]
 pub enum AliasKind {
     Projection,
+    Inherent,
     Opaque,
 }
 

library/std/src/personality/dwarf/eh.rs

@@ -47,6 +47,7 @@ pub enum EHAction {
     None,
     Cleanup(usize),
     Catch(usize),
+    Filter(usize),
     Terminate,
 }
 
@@ -142,9 +143,11 @@ unsafe fn interpret_cs_action(
         let ttype_index = action_reader.read_sleb128();
         if ttype_index == 0 {
             EHAction::Cleanup(lpad)
-        } else {
+        } else if ttype_index > 0 {
             // Stop unwinding Rust panics at catch_unwind.
             EHAction::Catch(lpad)
+        } else {
+            EHAction::Filter(lpad)
         }
     }
 }

library/std/src/personality/gcc.rs

@@ -135,7 +135,7 @@ cfg_if::cfg_if! {
                     EHAction::None | EHAction::Cleanup(_) => {
                         return continue_unwind(exception_object, context);
                     }
-                    EHAction::Catch(_) => {
+                    EHAction::Catch(_) | EHAction::Filter(_) => {
                         // EHABI requires the personality routine to update the
                         // SP value in the barrier cache of the exception object.
                         (*exception_object).private[5] =
@@ -147,7 +147,8 @@ cfg_if::cfg_if! {
             } else {
                 match eh_action {
                     EHAction::None => return continue_unwind(exception_object, context),
-                    EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
+                    EHAction::Filter(_) if state & uw::_US_FORCE_UNWIND as c_int != 0 => return continue_unwind(exception_object, context),
+                    EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
                         uw::_Unwind_SetGR(
                             context,
                             UNWIND_DATA_REG.0,
@@ -201,13 +202,15 @@ cfg_if::cfg_if! {
             if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
                 match eh_action {
                     EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
-                    EHAction::Catch(_) => uw::_URC_HANDLER_FOUND,
+                    EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
                     EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
                 }
             } else {
                 match eh_action {
                     EHAction::None => uw::_URC_CONTINUE_UNWIND,
-                    EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
+                    // Forced unwinding hits a terminate action.
+                    EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND,
+                    EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
                         uw::_Unwind_SetGR(
                             context,
                             UNWIND_DATA_REG.0,

src/librustdoc/clean/auto_trait.rs

@@ -556,7 +556,10 @@ where
                 WherePredicate::EqPredicate { lhs, rhs, bound_params } => {
                     match *lhs {
                         Type::QPath(box QPathData {
-                            ref assoc, ref self_type, ref trait_, ..
+                            ref assoc,
+                            ref self_type,
+                            trait_: Some(ref trait_),
+                            ..
                         }) => {
                             let ty = &*self_type;
                             let mut new_trait = trait_.clone();

src/librustdoc/clean/inline.rs

@@ -706,7 +706,12 @@ fn filter_non_trait_generics(trait_did: DefId, mut g: clean::Generics) -> clean:
 
     g.where_predicates.retain(|pred| match pred {
         clean::WherePredicate::BoundPredicate {
-            ty: clean::QPath(box clean::QPathData { self_type: clean::Generic(ref s), trait_, .. }),
+            ty:
+                clean::QPath(box clean::QPathData {
+                    self_type: clean::Generic(ref s),
+                    trait_: Some(trait_),
+                    ..
+                }),
             bounds,
             ..
         } => !(bounds.is_empty() || *s == kw::SelfUpper && trait_.def_id() == trait_did),

src/librustdoc/clean/mod.rs

@@ -441,7 +441,7 @@ fn clean_projection<'tcx>(
         assoc: projection_to_path_segment(ty, cx),
         should_show_cast,
         self_type,
-        trait_,
+        trait_: Some(trait_),
     }))
 }
 
@@ -1330,7 +1330,13 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                 let mut bounds: Vec<GenericBound> = Vec::new();
                 generics.where_predicates.retain_mut(|pred| match *pred {
                     WherePredicate::BoundPredicate {
-                        ty: QPath(box QPathData { ref assoc, ref self_type, ref trait_, .. }),
+                        ty:
+                            QPath(box QPathData {
+                                ref assoc,
+                                ref self_type,
+                                trait_: Some(ref trait_),
+                                ..
+                            }),
                         bounds: ref mut pred_bounds,
                         ..
                     } => {
@@ -1492,25 +1498,30 @@ fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type
                 assoc: clean_path_segment(p.segments.last().expect("segments were empty"), cx),
                 should_show_cast,
                 self_type,
-                trait_,
+                trait_: Some(trait_),
             }))
         }
         hir::QPath::TypeRelative(qself, segment) => {
             let ty = hir_ty_to_ty(cx.tcx, hir_ty);
-            let res = match ty.kind() {
+            let self_type = clean_ty(qself, cx);
+
+            let (trait_, should_show_cast) = match ty.kind() {
                 ty::Alias(ty::Projection, proj) => {
-                    Res::Def(DefKind::Trait, proj.trait_ref(cx.tcx).def_id)
+                    let res = Res::Def(DefKind::Trait, proj.trait_ref(cx.tcx).def_id);
+                    let trait_ = clean_path(&hir::Path { span, res, segments: &[] }, cx);
+                    register_res(cx, trait_.res);
+                    let self_def_id = res.opt_def_id();
+                    let should_show_cast =
+                        compute_should_show_cast(self_def_id, &trait_, &self_type);
+
+                    (Some(trait_), should_show_cast)
                 }
+                ty::Alias(ty::Inherent, _) => (None, false),
                 // Rustdoc handles `ty::Error`s by turning them into `Type::Infer`s.
                 ty::Error(_) => return Type::Infer,
-                // Otherwise, this is an inherent associated type.
-                _ => return clean_middle_ty(ty::Binder::dummy(ty), cx, None),
+                _ => bug!("clean: expected associated type, found `{ty:?}`"),
             };
-            let trait_ = clean_path(&hir::Path { span, res, segments: &[] }, cx);
-            register_res(cx, trait_.res);
-            let self_def_id = res.opt_def_id();
-            let self_type = clean_ty(qself, cx);
-            let should_show_cast = compute_should_show_cast(self_def_id, &trait_, &self_type);
+
             Type::QPath(Box::new(QPathData {
                 assoc: clean_path_segment(segment, cx),
                 should_show_cast,
@@ -1836,6 +1847,29 @@ pub(crate) fn clean_middle_ty<'tcx>(
             clean_projection(bound_ty.rebind(*data), cx, parent_def_id)
         }
 
+        ty::Alias(ty::Inherent, alias_ty) => {
+            let alias_ty = bound_ty.rebind(alias_ty);
+            let self_type = clean_middle_ty(alias_ty.map_bound(|ty| ty.self_ty()), cx, None);
+
+            Type::QPath(Box::new(QPathData {
+                assoc: PathSegment {
+                    name: cx.tcx.associated_item(alias_ty.skip_binder().def_id).name,
+                    args: GenericArgs::AngleBracketed {
+                        args: substs_to_args(
+                            cx,
+                            alias_ty.map_bound(|ty| ty.substs.as_slice()),
+                            true,
+                        )
+                        .into(),
+                        bindings: Default::default(),
+                    },
+                },
+                should_show_cast: false,
+                self_type,
+                trait_: None,
+            }))
+        }
+
         ty::Param(ref p) => {
             if let Some(bounds) = cx.impl_trait_bounds.remove(&p.index.into()) {
                 ImplTrait(bounds)

src/librustdoc/clean/types.rs

@@ -1660,7 +1660,7 @@ impl Type {
 
     pub(crate) fn projection(&self) -> Option<(&Type, DefId, PathSegment)> {
         if let QPath(box QPathData { self_type, trait_, assoc, .. }) = self {
-            Some((self_type, trait_.def_id(), assoc.clone()))
+            Some((self_type, trait_.as_ref()?.def_id(), assoc.clone()))
         } else {
             None
         }
@@ -1704,7 +1704,7 @@ pub(crate) struct QPathData {
     pub self_type: Type,
     /// FIXME: compute this field on demand.
     pub should_show_cast: bool,
-    pub trait_: Path,
+    pub trait_: Option<Path>,
 }
 
 /// A primitive (aka, builtin) type.

src/librustdoc/html/format.rs

@@ -1116,14 +1116,17 @@ fn fmt_type<'cx>(
             ref trait_,
             should_show_cast,
         }) => {
+            // FIXME(inherent_associated_types): Once we support non-ADT self-types (#106719),
+            // we need to surround them with angle brackets in some cases (e.g. `<dyn …>::P`).
+
             if f.alternate() {
-                if should_show_cast {
+                if let Some(trait_) = trait_ && should_show_cast {
                     write!(f, "<{:#} as {:#}>::", self_type.print(cx), trait_.print(cx))?
                 } else {
                     write!(f, "{:#}::", self_type.print(cx))?
                 }
             } else {
-                if should_show_cast {
+                if let Some(trait_) = trait_ && should_show_cast {
                     write!(f, "&lt;{} as {}&gt;::", self_type.print(cx), trait_.print(cx))?
                 } else {
                     write!(f, "{}::", self_type.print(cx))?
@@ -1139,15 +1142,36 @@ fn fmt_type<'cx>(
             //        the ugliness comes from inlining across crates where
             //        everything comes in as a fully resolved QPath (hard to
             //        look at).
-            if !f.alternate() && let Ok((url, _, path)) = href(trait_.def_id(), cx) {
-                write!(
-                    f,
-                    "<a class=\"associatedtype\" href=\"{url}#{shortty}.{name}\" \
-                                title=\"type {path}::{name}\">{name}</a>",
-                    shortty = ItemType::AssocType,
-                    name = assoc.name,
-                    path = join_with_double_colon(&path),
-                )
+            if !f.alternate() {
+                // FIXME(inherent_associated_types): We always link to the very first associated
+                // type (in respect to source order) that bears the given name (`assoc.name`) and that is
+                // affiliated with the computed `DefId`. This is obviously incorrect when we have
+                // multiple impl blocks. Ideally, we would thread the `DefId` of the assoc ty itself
+                // through here and map it to the corresponding HTML ID that was generated by
+                // `render::Context::derive_id` when the impl blocks were rendered.
+                // There is no such mapping unfortunately.
+                // As a hack, we could badly imitate `derive_id` here by keeping *count* when looking
+                // for the assoc ty `DefId` in `tcx.associated_items(self_ty_did).in_definition_order()`
+                // considering privacy, `doc(hidden)`, etc.
+                // I don't feel like that right now :cold_sweat:.
+
+                let parent_href = match trait_ {
+                    Some(trait_) => href(trait_.def_id(), cx).ok(),
+                    None => self_type.def_id(cx.cache()).and_then(|did| href(did, cx).ok()),
+                };
+
+                if let Some((url, _, path)) = parent_href {
+                    write!(
+                        f,
+                        "<a class=\"associatedtype\" href=\"{url}#{shortty}.{name}\" \
+                                    title=\"type {path}::{name}\">{name}</a>",
+                        shortty = ItemType::AssocType,
+                        name = assoc.name,
+                        path = join_with_double_colon(&path),
+                    )
+                } else {
+                    write!(f, "{}", assoc.name)
+                }
             } else {
                 write!(f, "{}", assoc.name)
             }?;

src/librustdoc/html/render/mod.rs

@@ -2202,7 +2202,9 @@ fn collect_paths_for_type(first_ty: clean::Type, cache: &Cache) -> Vec<String> {
             }
             clean::Type::QPath(box clean::QPathData { self_type, trait_, .. }) => {
                 work.push_back(self_type);
-                process_path(trait_.def_id());
+                if let Some(trait_) = trait_ {
+                    process_path(trait_.def_id());
+                }
             }
             _ => {}
         }

src/librustdoc/json/conversions.rs

@@ -574,7 +574,7 @@ impl FromWithTcx<clean::Type> for Type {
                 name: assoc.name.to_string(),
                 args: Box::new(assoc.args.into_tcx(tcx)),
                 self_type: Box::new(self_type.into_tcx(tcx)),
-                trait_: trait_.into_tcx(tcx),
+                trait_: trait_.map(|trait_| trait_.into_tcx(tcx)),
             },
         }
     }

src/rustdoc-json-types/lib.rs

@@ -8,7 +8,7 @@ use serde::{Deserialize, Serialize};
 use std::path::PathBuf;
 
 /// rustdoc format-version.
-pub const FORMAT_VERSION: u32 = 24;
+pub const FORMAT_VERSION: u32 = 25;
 
 /// A `Crate` is the root of the emitted JSON blob. It contains all type/documentation information
 /// about the language items in the local crate, as well as info about external items to allow
@@ -581,13 +581,15 @@ pub enum Type {
         #[serde(rename = "type")]
         type_: Box<Type>,
     },
-    /// `<Type as Trait>::Name` or associated types like `T::Item` where `T: Iterator`
+    /// Associated types like `<Type as Trait>::Name` and `T::Item` where
+    /// `T: Iterator` or inherent associated types like `Struct::Name`.
     QualifiedPath {
         name: String,
         args: Box<GenericArgs>,
         self_type: Box<Type>,
+        /// `None` iff this is an *inherent* associated type.
         #[serde(rename = "trait")]
-        trait_: Path,
+        trait_: Option<Path>,
     },
 }
 

src/tools/clippy/clippy_lints/src/dereference.rs

@@ -1424,6 +1424,7 @@ fn ty_auto_deref_stability<'tcx>(
                 continue;
             },
             ty::Param(_) => TyPosition::new_deref_stable_for_result(precedence, ty),
+            ty::Alias(ty::Inherent, _) => unreachable!("inherent projection should have been normalized away above"),
             ty::Alias(ty::Projection, _) if ty.has_non_region_param() => {
                 TyPosition::new_deref_stable_for_result(precedence, ty)
             },

src/tools/jsondoclint/src/validator.rs

@@ -273,7 +273,9 @@ impl<'a> Validator<'a> {
             Type::QualifiedPath { name: _, args, self_type, trait_ } => {
                 self.check_generic_args(&**args);
                 self.check_type(&**self_type);
-                self.check_path(trait_, PathKind::Trait);
+                if let Some(trait_) = trait_ {
+                    self.check_path(trait_, PathKind::Trait);
+                }
             }
         }
     }

tests/codegen/vec-shrink-panik.rs

@@ -25,7 +25,7 @@ pub fn issue71861(vec: Vec<u32>) -> Box<[u32]> {
 
     // Call to panic_cannot_unwind in case of double-panic is expected
     // on LLVM 16 and older, but other panics are not.
-    // CHECK: cleanup
+    // CHECK: filter
     // old-NEXT: ; call core::panicking::panic_cannot_unwind
     // old-NEXT: panic_cannot_unwind
 
@@ -40,7 +40,7 @@ pub fn issue75636<'a>(iter: &[&'a str]) -> Box<[&'a str]> {
 
     // Call to panic_cannot_unwind in case of double-panic is expected,
     // on LLVM 16 and older, but other panics are not.
-    // CHECK: cleanup
+    // CHECK: filter
     // old-NEXT: ; call core::panicking::panic_cannot_unwind
     // old-NEXT: panic_cannot_unwind
 

tests/run-make/forced-unwind-terminate-pof/Makefile

@@ -0,0 +1,9 @@
+# ignore-cross-compile
+# only-linux
+include ../tools.mk
+
+all: foo
+	$(call RUN,foo) | $(CGREP) -v "cannot unwind"
+
+foo: foo.rs
+	$(RUSTC) $<

tests/run-make/forced-unwind-terminate-pof/foo.rs

@@ -0,0 +1,17 @@
+// Tests that forced unwind through POF Rust frames wouldn't trigger our terminating guards.
+
+#![feature(c_unwind)]
+#![no_main]
+
+extern "C-unwind" {
+    fn pthread_exit(v: *mut core::ffi::c_void) -> !;
+}
+
+unsafe extern "C" fn call_pthread_exit() {
+    pthread_exit(core::ptr::null_mut());
+}
+
+#[no_mangle]
+unsafe extern "C-unwind" fn main(_argc: core::ffi::c_int, _argv: *mut *mut core::ffi::c_char) {
+    call_pthread_exit();
+}

tests/rustdoc/inherent-projections.rs

@@ -0,0 +1,44 @@
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+// @has 'inherent_projections/fn.create.html'
+// @has - '//pre[@class="rust item-decl"]' "create() -> Owner::Metadata"
+// @has - '//pre[@class="rust item-decl"]//a[@class="associatedtype"]/@href' 'struct.Owner.html#associatedtype.Metadata'
+pub fn create() -> Owner::Metadata {}
+
+pub struct Owner;
+
+impl Owner {
+    pub type Metadata = ();
+}
+
+// Make sure we handle bound vars correctly.
+// @has 'inherent_projections/type.User.html' '//pre[@class="rust item-decl"]' "for<'a> fn(_: Carrier<'a>::Focus)"
+pub type User = for<'a> fn(Carrier<'a>::Focus);
+
+pub struct Carrier<'a>(&'a ());
+
+impl<'a> Carrier<'a> {
+    pub type Focus = &'a mut i32;
+}
+
+////////////////////////////////////////
+
+// FIXME(inherent_associated_types): Below we link to `Proj` but we should link to `Proj-1`.
+// The current test checks for the buggy behavior for demonstration purposes.
+
+// @has 'inherent_projections/type.Test.html'
+// @has - '//pre[@class="rust item-decl"]' "Parametrized<i32>"
+// @has - '//pre[@class="rust item-decl"]//a[@class="associatedtype"]/@href' 'struct.Parametrized.html#associatedtype.Proj'
+// @!has - '//pre[@class="rust item-decl"]//a[@class="associatedtype"]/@href' 'struct.Parametrized.html#associatedtype.Proj-1'
+pub type Test = Parametrized<i32>::Proj;
+
+pub struct Parametrized<T>(T);
+
+impl Parametrized<bool> {
+    pub type Proj = ();
+}
+
+impl Parametrized<i32> {
+    pub type Proj = String;
+}

tests/rustdoc/intra-doc/inherent-associated-types.rs

@@ -0,0 +1,45 @@
+#![feature(inherent_associated_types)]
+
+#![allow(incomplete_features)]
+#![deny(rustdoc::broken_intra_doc_links)]
+
+// @has inherent_associated_types/index.html
+
+// @has - '//a/@href' 'enum.Simple.html#associatedtype.Type'
+//! [`Simple::Type`]
+
+pub enum Simple {}
+
+impl Simple {
+    pub type Type = ();
+}
+
+////////////////////////////////////////
+
+// @has 'inherent_associated_types/type.Test0.html' '//a/@href' \
+//          'struct.Parametrized.html#associatedtype.Proj'
+/// [`Parametrized<bool>::Proj`]
+pub type Test0 = ();
+
+// FIXME(inherent_associated_types): The intra-doc link below should point to `Proj-1` not `Proj`.
+// The current test checks for the buggy behavior for demonstration purposes.
+// The same bug happens for inherent associated functions and constants (see #85960, #93398).
+//
+// Further, at some point we should reject the intra-doc link `Parametrized::Proj`.
+// It currently links to `Parametrized<bool>::Proj`.
+
+// @has 'inherent_associated_types/type.Test1.html'
+// @has - '//a/@href' 'struct.Parametrized.html#associatedtype.Proj'
+// @!has - '//a/@href' 'struct.Parametrized.html#associatedtype.Proj-1'
+/// [`Parametrized<i32>::Proj`]
+pub type Test1 = ();
+
+pub struct Parametrized<T>(T);
+
+impl Parametrized<bool> {
+    pub type Proj = ();
+}
+
+impl Parametrized<i32> {
+    pub type Proj = String;
+}

tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.rs

@@ -0,0 +1,49 @@
+// check-fail
+// Tests that a doc comment will not preclude a field from being considered a diagnostic argument
+// normalize-stderr-test "the following other types implement trait `IntoDiagnosticArg`:(?:.*\n){0,9}\s+and \d+ others" -> "normalized in stderr"
+// normalize-stderr-test "diagnostic_builder\.rs:[0-9]+:[0-9]+" -> "diagnostic_builder.rs:LL:CC"
+
+// The proc_macro2 crate handles spans differently when on beta/stable release rather than nightly,
+// changing the output of this test. Since Subdiagnostic is strictly internal to the compiler
+// the test is just ignored on stable and beta:
+// ignore-stage1
+// ignore-beta
+// ignore-stable
+
+#![feature(rustc_private)]
+#![crate_type = "lib"]
+
+extern crate rustc_errors;
+extern crate rustc_fluent_macro;
+extern crate rustc_macros;
+extern crate rustc_session;
+extern crate rustc_span;
+
+use rustc_errors::{Applicability, DiagnosticMessage, SubdiagnosticMessage};
+use rustc_fluent_macro::fluent_messages;
+use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_span::Span;
+
+fluent_messages! { "./example.ftl" }
+
+struct NotIntoDiagnosticArg;
+
+#[derive(Diagnostic)]
+#[diag(no_crate_example)]
+struct Test {
+    #[primary_span]
+    span: Span,
+    /// A doc comment
+    arg: NotIntoDiagnosticArg,
+    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+}
+
+#[derive(Subdiagnostic)]
+#[label(no_crate_example)]
+struct SubTest {
+    #[primary_span]
+    span: Span,
+    /// A doc comment
+    arg: NotIntoDiagnosticArg,
+    //~^ ERROR the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+}

tests/ui-fulldeps/session-diagnostic/diagnostic-derive-doc-comment-field.stderr

@@ -0,0 +1,30 @@
+error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+  --> $DIR/diagnostic-derive-doc-comment-field.rs:37:10
+   |
+LL | #[derive(Diagnostic)]
+   |          ---------- required by a bound introduced by this call
+...
+LL |     arg: NotIntoDiagnosticArg,
+   |          ^^^^^^^^^^^^^^^^^^^^ the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
+   |
+   = help: normalized in stderr
+note: required by a bound in `DiagnosticBuilder::<'a, G>::set_arg`
+  --> $COMPILER_DIR/rustc_errors/src/diagnostic_builder.rs:LL:CC
+   = note: this error originates in the macro `forward` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `NotIntoDiagnosticArg: IntoDiagnosticArg` is not satisfied
+  --> $DIR/diagnostic-derive-doc-comment-field.rs:47:10
+   |
+LL | #[derive(Subdiagnostic)]
+   |          ------------- required by a bound introduced by this call
+...
+LL |     arg: NotIntoDiagnosticArg,
+   |          ^^^^^^^^^^^^^^^^^^^^ the trait `IntoDiagnosticArg` is not implemented for `NotIntoDiagnosticArg`
+   |
+   = help: normalized in stderr
+note: required by a bound in `Diagnostic::set_arg`
+  --> $COMPILER_DIR/rustc_errors/src/diagnostic.rs:964:5
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.rs

@@ -339,12 +339,12 @@ struct ErrorWithDefaultLabelAttr<'a> {
 }
 
 #[derive(Diagnostic)]
-//~^ ERROR the trait bound `Hello: IntoDiagnosticArg` is not satisfied
 #[diag(no_crate_example, code = "E0123")]
 struct ArgFieldWithoutSkip {
     #[primary_span]
     span: Span,
     other: Hello,
+    //~^ ERROR the trait bound `Hello: IntoDiagnosticArg` is not satisfied
 }
 
 #[derive(Diagnostic)]

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr

@@ -641,15 +641,18 @@ LL | #[derive(Diagnostic)]
    = note: this error originates in the derive macro `Diagnostic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `Hello: IntoDiagnosticArg` is not satisfied
-  --> $DIR/diagnostic-derive.rs:341:10
+  --> $DIR/diagnostic-derive.rs:346:12
    |
 LL | #[derive(Diagnostic)]
-   |          ^^^^^^^^^^ the trait `IntoDiagnosticArg` is not implemented for `Hello`
+   |          ---------- required by a bound introduced by this call
+...
+LL |     other: Hello,
+   |            ^^^^^ the trait `IntoDiagnosticArg` is not implemented for `Hello`
    |
    = help: normalized in stderr
 note: required by a bound in `DiagnosticBuilder::<'a, G>::set_arg`
   --> $COMPILER_DIR/rustc_errors/src/diagnostic_builder.rs:LL:CC
-   = note: this error originates in the derive macro `Diagnostic` which comes from the expansion of the macro `forward` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `forward` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 84 previous errors
 

tests/ui/associated-inherent-types/bugs/cycle-iat-inside-of-adt.rs

@@ -0,0 +1,10 @@
+// known-bug: #108491
+
+// FIXME(inherent_associated_types): This should pass.
+
+struct Foo {
+    bar: Self::Bar,
+}
+impl Foo {
+    pub type Bar = usize;
+}

tests/ui/associated-inherent-types/bugs/cycle-iat-inside-of-adt.stderr

@@ -0,0 +1,49 @@
+error[E0601]: `main` function not found in crate `cycle_iat_inside_of_adt`
+  --> $DIR/cycle-iat-inside-of-adt.rs:10:2
+   |
+LL | }
+   |  ^ consider adding a `main` function to `$DIR/cycle-iat-inside-of-adt.rs`
+
+error[E0391]: cycle detected when computing predicates of `Foo`
+  --> $DIR/cycle-iat-inside-of-adt.rs:5:1
+   |
+LL | struct Foo {
+   | ^^^^^^^^^^
+   |
+note: ...which requires computing predicates of `Foo`...
+  --> $DIR/cycle-iat-inside-of-adt.rs:5:1
+   |
+LL | struct Foo {
+   | ^^^^^^^^^^
+note: ...which requires computing inferred outlives predicates of `Foo`...
+  --> $DIR/cycle-iat-inside-of-adt.rs:5:1
+   |
+LL | struct Foo {
+   | ^^^^^^^^^^
+   = note: ...which requires computing the inferred outlives predicates for items in this crate...
+note: ...which requires computing type of `Foo::bar`...
+  --> $DIR/cycle-iat-inside-of-adt.rs:6:5
+   |
+LL |     bar: Self::Bar,
+   |     ^^^^^^^^^^^^^^
+note: ...which requires computing normalized predicates of `Foo`...
+  --> $DIR/cycle-iat-inside-of-adt.rs:5:1
+   |
+LL | struct Foo {
+   | ^^^^^^^^^^
+   = note: ...which again requires computing predicates of `Foo`, completing the cycle
+note: cycle used when collecting item types in top-level module
+  --> $DIR/cycle-iat-inside-of-adt.rs:5:1
+   |
+LL | / struct Foo {
+LL | |     bar: Self::Bar,
+LL | | }
+LL | | impl Foo {
+LL | |     pub type Bar = usize;
+LL | | }
+   | |_^
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0391, E0601.
+For more information about an error, try `rustc --explain E0391`.

tests/ui/associated-inherent-types/bugs/cycle-iat-inside-of-where-predicate.rs

@@ -0,0 +1,16 @@
+// known-bug: unknown
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+// FIXME(inherent_associated_types): This shouldn't lead to a cycle error.
+
+fn user<T>() where S<T>::P: std::fmt::Debug {}
+
+struct S<T>;
+
+impl<T: Copy> S<T> {
+    type P = ();
+}
+
+fn main() {}

tests/ui/associated-inherent-types/bugs/cycle-iat-inside-of-where-predicate.stderr

@@ -0,0 +1,37 @@
+error[E0391]: cycle detected when computing predicates of `user`
+  --> $DIR/cycle-iat-inside-of-where-predicate.rs:8:1
+   |
+LL | fn user<T>() where S<T>::P: std::fmt::Debug {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: ...which requires computing predicates of `user`...
+  --> $DIR/cycle-iat-inside-of-where-predicate.rs:8:1
+   |
+LL | fn user<T>() where S<T>::P: std::fmt::Debug {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires computing explicit predicates of `user`...
+  --> $DIR/cycle-iat-inside-of-where-predicate.rs:8:1
+   |
+LL | fn user<T>() where S<T>::P: std::fmt::Debug {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires computing normalized predicates of `user`...
+  --> $DIR/cycle-iat-inside-of-where-predicate.rs:8:1
+   |
+LL | fn user<T>() where S<T>::P: std::fmt::Debug {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: ...which again requires computing predicates of `user`, completing the cycle
+note: cycle used when collecting item types in top-level module
+  --> $DIR/cycle-iat-inside-of-where-predicate.rs:3:1
+   |
+LL | / #![feature(inherent_associated_types)]
+LL | | #![allow(incomplete_features)]
+LL | |
+LL | | // FIXME(inherent_associated_types): This shouldn't lead to a cycle error.
+...  |
+LL | |
+LL | | fn main() {}
+   | |____________^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0391`.

tests/ui/associated-inherent-types/bugs/ice-substitution.rs

@@ -1,23 +0,0 @@
-// known-bug: unknown
-// failure-status: 101
-// normalize-stderr-test "note: .*\n\n" -> ""
-// normalize-stderr-test "thread 'rustc' panicked.*\n" -> ""
-// rustc-env:RUST_BACKTRACE=0
-
-// FIXME: I presume a type variable that couldn't be solved by `resolve_vars_if_possible`
-//        escapes the InferCtxt snapshot.
-
-#![feature(inherent_associated_types)]
-#![allow(incomplete_features)]
-
-struct Cont<T>(T);
-
-impl<T: Copy> Cont<T> {
-    type Out = Vec<T>;
-}
-
-pub fn weird<T: Copy>(x: T) {
-    let _: Cont<_>::Out = vec![true];
-}
-
-fn main() {}

tests/ui/associated-inherent-types/bugs/ice-substitution.stderr

@@ -1,6 +0,0 @@
-error: the compiler unexpectedly panicked. this is a bug.
-
-query stack during panic:
-#0 [typeck] type-checking `weird`
-#1 [used_trait_imports] finding used_trait_imports `weird`
-end of query stack

tests/ui/associated-inherent-types/bugs/inference-fail.rs

@@ -1,15 +0,0 @@
-// known-bug: unknown
-
-#![feature(inherent_associated_types)]
-#![allow(incomplete_features)]
-
-struct S<T>(T);
-
-impl S<()> {
-    type P = i128;
-}
-
-fn main() {
-    // We fail to infer `_ == ()` here.
-    let _: S<_>::P;
-}

tests/ui/associated-inherent-types/bugs/lack-of-regionck.rs

@@ -1,19 +0,0 @@
-// known-bug: unknown
-// check-pass
-
-// We currently don't region-check inherent associated type projections at all.
-
-#![feature(inherent_associated_types)]
-#![allow(incomplete_features, dead_code)]
-
-struct S<T>(T);
-
-impl S<&'static ()> {
-    type T = ();
-}
-
-fn usr<'a>() {
-    let _: S::<&'a ()>::T; // this should *fail* but it doesn't!
-}
-
-fn main() {}

tests/ui/associated-inherent-types/bugs/wf-check-skipped.rs

@@ -0,0 +1,15 @@
+// known-bug: #100041
+// check-pass
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+
+// FIXME(inherent_associated_types): This should fail.
+
+struct Foo;
+
+impl Foo {
+    type Bar<T> = ();
+}
+
+fn main() -> Foo::Bar::<Vec<[u32]>> {}

tests/ui/associated-inherent-types/dispatch-on-self-type-0.rs

@@ -31,7 +31,7 @@ fn main() {
     let _: Select<u8>::Projection = ();
 
     let _: Choose<NonCopy>::Result = ();
-    let _: Choose<bool>::Result = vec![true];
+    let _: Choose<&str>::Result = vec!["…"]; // regression test for issue #108957
 }
 
 // Test if we use the correct `ParamEnv` when proving obligations.