Auto merge of #116193 - matthiaskrgr:rollup-wpt7m5t, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - #115934 (Split out the stable part of smir into its own crate to prevent accidental usage of forever unstable things)
 - #116149 (Anonymize binders for `refining_impl_trait` check)
 - #116178 (Add test for `const async fn`)
 - #116187 (Add context to `let: Ty = loop { break };`)

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

28 files changed, 272 insertions, 235 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e67fe08feec..014e14e5399 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3245,6 +3245,7 @@ dependencies = [
  "rustc_driver",
  "rustc_driver_impl",
  "rustc_smir",
+ "stable_mir",
 ]
 
 [[package]]
@@ -4409,7 +4410,7 @@ dependencies = [
  "rustc_session",
  "rustc_span",
  "rustc_target",
- "scoped-tls",
+ "stable_mir",
  "tracing",
 ]
 
@@ -4947,6 +4948,14 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
 [[package]]
+name = "stable_mir"
+version = "0.1.0-preview"
+dependencies = [
+ "scoped-tls",
+ "tracing",
+]
+
+[[package]]
 name = "stacker"
 version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/compiler/rustc/Cargo.toml b/compiler/rustc/Cargo.toml
index 41003ad83f3..dcb165f9fdb 100644
--- a/compiler/rustc/Cargo.toml
+++ b/compiler/rustc/Cargo.toml
@@ -13,6 +13,7 @@ rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
 # Make sure rustc_smir ends up in the sysroot, because this
 # crate is intended to be used by stable MIR consumers, which are not in-tree
 rustc_smir = { path = "../rustc_smir" }
+stable_mir = { path = "../stable_mir" }
 
 [dependencies.jemalloc-sys]
 version = "0.5.0"
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
index a8149b634ef..d9e0e87eb47 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item/refine.rs
@@ -5,7 +5,7 @@ use rustc_infer::infer::{outlives::env::OutlivesEnvironment, TyCtxtInferExt};
 use rustc_lint_defs::builtin::REFINING_IMPL_TRAIT;
 use rustc_middle::traits::{ObligationCause, Reveal};
 use rustc_middle::ty::{
-    self, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitor,
+    self, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
 use rustc_span::{Span, DUMMY_SP};
 use rustc_trait_selection::traits::{
@@ -176,9 +176,13 @@ pub(super) fn check_refining_return_position_impl_trait_in_trait<'tcx>(
         return;
     };
 
-    // For quicker lookup, use an `IndexSet`
-    // (we don't use one earlier because it's not foldable..)
-    let trait_bounds = FxIndexSet::from_iter(trait_bounds);
+    // For quicker lookup, use an `IndexSet` (we don't use one earlier because
+    // it's not foldable..).
+    // Also, We have to anonymize binders in these types because they may contain
+    // `BrNamed` bound vars, which contain unique `DefId`s which correspond to syntax
+    // locations that we don't care about when checking bound equality.
+    let trait_bounds = FxIndexSet::from_iter(trait_bounds.fold_with(&mut Anonymize { tcx }));
+    let impl_bounds = impl_bounds.fold_with(&mut Anonymize { tcx });
 
     // Find any clauses that are present in the impl's RPITITs that are not
     // present in the trait's RPITITs. This will trigger on trivial predicates,
@@ -309,3 +313,20 @@ fn type_visibility<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Option<ty::Visibili
         _ => None,
     }
 }
+
+struct Anonymize<'tcx> {
+    tcx: TyCtxt<'tcx>,
+}
+
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Anonymize<'tcx> {
+    fn interner(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_binder<T>(&mut self, t: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
+    where
+        T: TypeFoldable<TyCtxt<'tcx>>,
+    {
+        self.tcx.anonymize_bound_vars(t)
+    }
+}
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 31e773585d1..256a4bf9449 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -545,6 +545,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Climb the HIR tree to see if the current `Expr` is part of a `break;` statement.
             let Some(
                 hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Semi(&ref p), .. })
+                | hir::Node::Block(hir::Block { expr: Some(&ref p), .. })
                 | hir::Node::Expr(&ref p),
             ) = self.tcx.hir().find(parent_id)
             else {
diff --git a/compiler/rustc_smir/Cargo.toml b/compiler/rustc_smir/Cargo.toml
index 21ec904e43c..4c29f743708 100644
--- a/compiler/rustc_smir/Cargo.toml
+++ b/compiler/rustc_smir/Cargo.toml
@@ -4,24 +4,14 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
-# Use optional dependencies for rustc_* in order to support building this crate separately.
-rustc_hir = { path = "../rustc_hir", optional = true }
-rustc_middle = { path = "../rustc_middle", optional = true }
-rustc_span = { path = "../rustc_span", optional = true }
-rustc_target = { path = "../rustc_target", optional = true }
-rustc_driver = { path = "../rustc_driver", optional = true }
-rustc_interface = { path = "../rustc_interface", optional = true}
-rustc_session = {path = "../rustc_session", optional = true}
+rustc_hir = { path = "../rustc_hir" }
+rustc_middle = { path = "../rustc_middle" }
+rustc_span = { path = "../rustc_span" }
+rustc_target = { path = "../rustc_target" }
+rustc_driver = { path = "../rustc_driver" }
+rustc_interface = { path = "../rustc_interface" }
+rustc_session = {path = "../rustc_session" }
 tracing = "0.1"
-scoped-tls = "1.0"
+stable_mir = {path = "../stable_mir" }
 
 [features]
-default = [
-    "rustc_hir",
-    "rustc_middle",
-    "rustc_span",
-    "rustc_target",
-    "rustc_driver",
-    "rustc_interface",
-    "rustc_session",
-]
diff --git a/compiler/rustc_smir/src/lib.rs b/compiler/rustc_smir/src/lib.rs
index 8cb533c8d67..b6c36678db5 100644
--- a/compiler/rustc_smir/src/lib.rs
+++ b/compiler/rustc_smir/src/lib.rs
@@ -10,26 +10,12 @@
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
     test(attr(allow(unused_variables), deny(warnings)))
 )]
-#![cfg_attr(not(feature = "default"), feature(rustc_private))]
+#![feature(rustc_private)]
 #![feature(ptr_metadata)]
 #![feature(type_alias_impl_trait)] // Used to define opaque types.
 #![feature(intra_doc_pointers)]
 
-// Declare extern rustc_* crates to enable building this crate separately from the compiler.
-#[cfg(not(feature = "default"))]
-extern crate rustc_hir;
-#[cfg(not(feature = "default"))]
-extern crate rustc_middle;
-#[cfg(not(feature = "default"))]
-extern crate rustc_span;
-#[cfg(not(feature = "default"))]
-extern crate rustc_target;
-
 pub mod rustc_internal;
-pub mod stable_mir;
 
 // Make this module private for now since external users should not call these directly.
 mod rustc_smir;
-
-#[macro_use]
-extern crate scoped_tls;
diff --git a/compiler/rustc_smir/src/rustc_internal/mod.rs b/compiler/rustc_smir/src/rustc_internal/mod.rs
index 10ee5af86c6..441aafd1257 100644
--- a/compiler/rustc_smir/src/rustc_internal/mod.rs
+++ b/compiler/rustc_smir/src/rustc_internal/mod.rs
@@ -3,75 +3,17 @@
 //! For that, we define APIs that will temporarily be public to 3P that exposes rustc internal APIs
 //! until stable MIR is complete.
 
-use std::fmt::Debug;
 use std::ops::{ControlFlow, Index};
 
 use crate::rustc_internal;
-use crate::stable_mir::CompilerError;
-use crate::{
-    rustc_smir::Tables,
-    stable_mir::{self, with},
-};
+use crate::rustc_smir::Tables;
 use rustc_driver::{Callbacks, Compilation, RunCompiler};
 use rustc_interface::{interface, Queries};
 use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::ty::TyCtxt;
 pub use rustc_span::def_id::{CrateNum, DefId};
 use rustc_span::Span;
-
-fn with_tables<R>(mut f: impl FnMut(&mut Tables<'_>) -> R) -> R {
-    let mut ret = None;
-    with(|tables| tables.rustc_tables(&mut |t| ret = Some(f(t))));
-    ret.unwrap()
-}
-
-pub fn item_def_id(item: &stable_mir::CrateItem) -> DefId {
-    with_tables(|t| t[item.0])
-}
-
-pub fn crate_item(did: DefId) -> stable_mir::CrateItem {
-    with_tables(|t| t.crate_item(did))
-}
-
-pub fn adt_def(did: DefId) -> stable_mir::ty::AdtDef {
-    with_tables(|t| t.adt_def(did))
-}
-
-pub fn foreign_def(did: DefId) -> stable_mir::ty::ForeignDef {
-    with_tables(|t| t.foreign_def(did))
-}
-
-pub fn fn_def(did: DefId) -> stable_mir::ty::FnDef {
-    with_tables(|t| t.fn_def(did))
-}
-
-pub fn closure_def(did: DefId) -> stable_mir::ty::ClosureDef {
-    with_tables(|t| t.closure_def(did))
-}
-
-pub fn generator_def(did: DefId) -> stable_mir::ty::GeneratorDef {
-    with_tables(|t| t.generator_def(did))
-}
-
-pub fn alias_def(did: DefId) -> stable_mir::ty::AliasDef {
-    with_tables(|t| t.alias_def(did))
-}
-
-pub fn param_def(did: DefId) -> stable_mir::ty::ParamDef {
-    with_tables(|t| t.param_def(did))
-}
-
-pub fn br_named_def(did: DefId) -> stable_mir::ty::BrNamedDef {
-    with_tables(|t| t.br_named_def(did))
-}
-
-pub fn trait_def(did: DefId) -> stable_mir::ty::TraitDef {
-    with_tables(|t| t.trait_def(did))
-}
-
-pub fn impl_def(did: DefId) -> stable_mir::ty::ImplDef {
-    with_tables(|t| t.impl_def(did))
-}
+use stable_mir::CompilerError;
 
 impl<'tcx> Index<stable_mir::DefId> for Tables<'tcx> {
     type Output = DefId;
@@ -82,6 +24,15 @@ impl<'tcx> Index<stable_mir::DefId> for Tables<'tcx> {
     }
 }
 
+impl<'tcx> Index<stable_mir::ty::Span> for Tables<'tcx> {
+    type Output = Span;
+
+    #[inline(always)]
+    fn index(&self, index: stable_mir::ty::Span) -> &Self::Output {
+        &self.spans[index.0]
+    }
+}
+
 impl<'tcx> Tables<'tcx> {
     pub fn crate_item(&mut self, did: DefId) -> stable_mir::CrateItem {
         stable_mir::CrateItem(self.create_def_id(did))
@@ -178,32 +129,12 @@ pub fn crate_num(item: &stable_mir::Crate) -> CrateNum {
 }
 
 pub fn run(tcx: TyCtxt<'_>, f: impl FnOnce()) {
-    crate::stable_mir::run(
+    stable_mir::run(
         Tables { tcx, def_ids: vec![], alloc_ids: vec![], spans: vec![], types: vec![] },
         f,
     );
 }
 
-/// A type that provides internal information but that can still be used for debug purpose.
-#[derive(Clone)]
-pub struct Opaque(String);
-
-impl std::fmt::Display for Opaque {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.0)
-    }
-}
-
-impl std::fmt::Debug for Opaque {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:?}", self.0)
-    }
-}
-
-pub(crate) fn opaque<T: Debug>(value: &T) -> Opaque {
-    Opaque(format!("{value:?}"))
-}
-
 pub struct StableMir<B = (), C = ()>
 where
     B: Send,
diff --git a/compiler/rustc_smir/src/rustc_smir/alloc.rs b/compiler/rustc_smir/src/rustc_smir/alloc.rs
index d8766cf8ce2..63a2a145069 100644
--- a/compiler/rustc_smir/src/rustc_smir/alloc.rs
+++ b/compiler/rustc_smir/src/rustc_smir/alloc.rs
@@ -3,11 +3,9 @@ use rustc_middle::mir::{
     ConstValue,
 };
 
-use crate::{
-    rustc_smir::{Stable, Tables},
-    stable_mir::mir::Mutability,
-    stable_mir::ty::{Allocation, ProvenanceMap},
-};
+use crate::rustc_smir::{Stable, Tables};
+use stable_mir::mir::Mutability;
+use stable_mir::ty::{Allocation, ProvenanceMap};
 
 /// Creates new empty `Allocation` from given `Align`.
 fn new_empty_allocation(align: rustc_target::abi::Align) -> Allocation {
diff --git a/compiler/rustc_smir/src/rustc_smir/mod.rs b/compiler/rustc_smir/src/rustc_smir/mod.rs
index b575445c4d5..5ff17613b4e 100644
--- a/compiler/rustc_smir/src/rustc_smir/mod.rs
+++ b/compiler/rustc_smir/src/rustc_smir/mod.rs
@@ -7,19 +7,16 @@
 //!
 //! For now, we are developing everything inside `rustc`, thus, we keep this module private.
 
-use crate::rustc_internal::{self, opaque};
-use crate::stable_mir::mir::{CopyNonOverlapping, UserTypeProjection, VariantIdx};
-use crate::stable_mir::ty::{
-    FloatTy, GenericParamDef, IntTy, Movability, RigidTy, Span, TyKind, UintTy,
-};
-use crate::stable_mir::{self, CompilerError, Context};
+use hir::def::DefKind;
 use rustc_hir as hir;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::{alloc_range, AllocId};
 use rustc_middle::ty::{self, Ty, TyCtxt, Variance};
 use rustc_span::def_id::{CrateNum, DefId, LOCAL_CRATE};
-use rustc_span::ErrorGuaranteed;
 use rustc_target::abi::FieldIdx;
+use stable_mir::mir::{CopyNonOverlapping, UserTypeProjection, VariantIdx};
+use stable_mir::ty::{FloatTy, GenericParamDef, IntTy, Movability, RigidTy, Span, TyKind, UintTy};
+use stable_mir::{self, opaque, Context};
 use tracing::debug;
 
 mod alloc;
@@ -44,6 +41,14 @@ impl<'tcx> Context for Tables<'tcx> {
         self.tcx.def_path_str(self[def_id])
     }
 
+    fn print_span(&self, span: stable_mir::ty::Span) -> String {
+        self.tcx.sess.source_map().span_to_diagnostic_string(self[span])
+    }
+
+    fn def_kind(&mut self, def_id: stable_mir::DefId) -> stable_mir::DefKind {
+        self.tcx.def_kind(self[def_id]).stable(self)
+    }
+
     fn span_of_an_item(&mut self, def_id: stable_mir::DefId) -> Span {
         self.tcx.def_span(self[def_id]).stable(self)
     }
@@ -104,11 +109,7 @@ impl<'tcx> Context for Tables<'tcx> {
         }
     }
 
-    fn rustc_tables(&mut self, f: &mut dyn FnMut(&mut Tables<'_>)) {
-        f(self)
-    }
-
-    fn ty_kind(&mut self, ty: crate::stable_mir::ty::Ty) -> TyKind {
+    fn ty_kind(&mut self, ty: stable_mir::ty::Ty) -> TyKind {
         self.types[ty.0].clone().stable(self)
     }
 
@@ -276,7 +277,7 @@ impl<'tcx> Stable<'tcx> for mir::Rvalue<'tcx> {
                 place.stable(tables),
             ),
             ThreadLocalRef(def_id) => {
-                stable_mir::mir::Rvalue::ThreadLocalRef(rustc_internal::crate_item(*def_id))
+                stable_mir::mir::Rvalue::ThreadLocalRef(tables.crate_item(*def_id))
             }
             AddressOf(mutability, place) => {
                 stable_mir::mir::Rvalue::AddressOf(mutability.stable(tables), place.stable(tables))
@@ -739,7 +740,7 @@ impl<'tcx> Stable<'tcx> for mir::AggregateKind<'tcx> {
             mir::AggregateKind::Tuple => stable_mir::mir::AggregateKind::Tuple,
             mir::AggregateKind::Adt(def_id, var_idx, generic_arg, user_ty_index, field_idx) => {
                 stable_mir::mir::AggregateKind::Adt(
-                    rustc_internal::adt_def(*def_id),
+                    tables.adt_def(*def_id),
                     var_idx.index(),
                     generic_arg.stable(tables),
                     user_ty_index.map(|idx| idx.index()),
@@ -748,13 +749,13 @@ impl<'tcx> Stable<'tcx> for mir::AggregateKind<'tcx> {
             }
             mir::AggregateKind::Closure(def_id, generic_arg) => {
                 stable_mir::mir::AggregateKind::Closure(
-                    rustc_internal::closure_def(*def_id),
+                    tables.closure_def(*def_id),
                     generic_arg.stable(tables),
                 )
             }
             mir::AggregateKind::Generator(def_id, generic_arg, movability) => {
                 stable_mir::mir::AggregateKind::Generator(
-                    rustc_internal::generator_def(*def_id),
+                    tables.generator_def(*def_id),
                     generic_arg.stable(tables),
                     movability.stable(tables),
                 )
@@ -964,13 +965,13 @@ impl<'tcx> Stable<'tcx> for ty::FnSig<'tcx> {
 impl<'tcx> Stable<'tcx> for ty::BoundTyKind {
     type T = stable_mir::ty::BoundTyKind;
 
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
         use stable_mir::ty::BoundTyKind;
 
         match self {
             ty::BoundTyKind::Anon => BoundTyKind::Anon,
             ty::BoundTyKind::Param(def_id, symbol) => {
-                BoundTyKind::Param(rustc_internal::param_def(*def_id), symbol.to_string())
+                BoundTyKind::Param(tables.param_def(*def_id), symbol.to_string())
             }
         }
     }
@@ -979,13 +980,13 @@ impl<'tcx> Stable<'tcx> for ty::BoundTyKind {
 impl<'tcx> Stable<'tcx> for ty::BoundRegionKind {
     type T = stable_mir::ty::BoundRegionKind;
 
-    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
+    fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
         use stable_mir::ty::BoundRegionKind;
 
         match self {
             ty::BoundRegionKind::BrAnon => BoundRegionKind::BrAnon,
             ty::BoundRegionKind::BrNamed(def_id, symbol) => {
-                BoundRegionKind::BrNamed(rustc_internal::br_named_def(*def_id), symbol.to_string())
+                BoundRegionKind::BrNamed(tables.br_named_def(*def_id), symbol.to_string())
             }
             ty::BoundRegionKind::BrEnv => BoundRegionKind::BrEnv,
         }
@@ -1072,12 +1073,10 @@ impl<'tcx> Stable<'tcx> for Ty<'tcx> {
             ty::Uint(uint_ty) => TyKind::RigidTy(RigidTy::Uint(uint_ty.stable(tables))),
             ty::Float(float_ty) => TyKind::RigidTy(RigidTy::Float(float_ty.stable(tables))),
             ty::Adt(adt_def, generic_args) => TyKind::RigidTy(RigidTy::Adt(
-                rustc_internal::adt_def(adt_def.did()),
+                tables.adt_def(adt_def.did()),
                 generic_args.stable(tables),
             )),
-            ty::Foreign(def_id) => {
-                TyKind::RigidTy(RigidTy::Foreign(rustc_internal::foreign_def(*def_id)))
-            }
+            ty::Foreign(def_id) => TyKind::RigidTy(RigidTy::Foreign(tables.foreign_def(*def_id))),
             ty::Str => TyKind::RigidTy(RigidTy::Str),
             ty::Array(ty, constant) => {
                 TyKind::RigidTy(RigidTy::Array(tables.intern_ty(*ty), constant.stable(tables)))
@@ -1091,10 +1090,9 @@ impl<'tcx> Stable<'tcx> for Ty<'tcx> {
                 tables.intern_ty(*ty),
                 mutbl.stable(tables),
             )),
-            ty::FnDef(def_id, generic_args) => TyKind::RigidTy(RigidTy::FnDef(
-                rustc_internal::fn_def(*def_id),
-                generic_args.stable(tables),
-            )),
+            ty::FnDef(def_id, generic_args) => {
+                TyKind::RigidTy(RigidTy::FnDef(tables.fn_def(*def_id), generic_args.stable(tables)))
+            }
             ty::FnPtr(poly_fn_sig) => TyKind::RigidTy(RigidTy::FnPtr(poly_fn_sig.stable(tables))),
             ty::Dynamic(existential_predicates, region, dyn_kind) => {
                 TyKind::RigidTy(RigidTy::Dynamic(
@@ -1107,11 +1105,11 @@ impl<'tcx> Stable<'tcx> for Ty<'tcx> {
                 ))
             }
             ty::Closure(def_id, generic_args) => TyKind::RigidTy(RigidTy::Closure(
-                rustc_internal::closure_def(*def_id),
+                tables.closure_def(*def_id),
                 generic_args.stable(tables),
             )),
             ty::Generator(def_id, generic_args, movability) => TyKind::RigidTy(RigidTy::Generator(
-                rustc_internal::generator_def(*def_id),
+                tables.generator_def(*def_id),
                 generic_args.stable(tables),
                 movability.stable(tables),
             )),
@@ -1223,7 +1221,7 @@ impl<'tcx> Stable<'tcx> for ty::TraitDef {
         use stable_mir::ty::TraitDecl;
 
         TraitDecl {
-            def_id: rustc_internal::trait_def(self.def_id),
+            def_id: tables.trait_def(self.def_id),
             unsafety: self.unsafety.stable(tables),
             paren_sugar: self.paren_sugar,
             has_auto_impl: self.has_auto_impl,
@@ -1272,7 +1270,7 @@ impl<'tcx> Stable<'tcx> for ty::TraitRef<'tcx> {
     fn stable(&self, tables: &mut Tables<'tcx>) -> Self::T {
         use stable_mir::ty::TraitRef;
 
-        TraitRef { def_id: rustc_internal::trait_def(self.def_id), args: self.args.stable(tables) }
+        TraitRef { def_id: tables.trait_def(self.def_id), args: self.args.stable(tables) }
     }
 }
 
@@ -1516,8 +1514,11 @@ impl<'tcx> Stable<'tcx> for rustc_span::Span {
     }
 }
 
-impl<T> From<ErrorGuaranteed> for CompilerError<T> {
-    fn from(_error: ErrorGuaranteed) -> Self {
-        CompilerError::CompilationFailed
+impl<'tcx> Stable<'tcx> for DefKind {
+    type T = stable_mir::DefKind;
+
+    fn stable(&self, _: &mut Tables<'tcx>) -> Self::T {
+        // FIXME: add a real implementation of stable DefKind
+        opaque(self)
     }
 }
diff --git a/compiler/stable_mir/Cargo.toml b/compiler/stable_mir/Cargo.toml
new file mode 100644
index 00000000000..c61e217bf9f
--- /dev/null
+++ b/compiler/stable_mir/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "stable_mir"
+version = "0.1.0-preview"
+edition = "2021"
+
+[dependencies]
+tracing = "0.1"
+scoped-tls = "1.0"
diff --git a/compiler/rustc_smir/README.md b/compiler/stable_mir/README.md
index 31dee955f49..31dee955f49 100644
--- a/compiler/rustc_smir/README.md
+++ b/compiler/stable_mir/README.md
diff --git a/compiler/rustc_smir/rust-toolchain.toml b/compiler/stable_mir/rust-toolchain.toml
index d75e8e33b1c..d75e8e33b1c 100644
--- a/compiler/rustc_smir/rust-toolchain.toml
+++ b/compiler/stable_mir/rust-toolchain.toml
diff --git a/compiler/rustc_smir/src/stable_mir/fold.rs b/compiler/stable_mir/src/fold.rs
index 831cfb40a15..16ae62311aa 100644
--- a/compiler/rustc_smir/src/stable_mir/fold.rs
+++ b/compiler/stable_mir/src/fold.rs
@@ -1,6 +1,6 @@
 use std::ops::ControlFlow;
 
-use crate::rustc_internal::Opaque;
+use crate::Opaque;
 
 use super::ty::{
     Allocation, Binder, Const, ConstDef, ConstantKind, ExistentialPredicate, FnSig, GenericArgKind,
diff --git a/compiler/rustc_smir/src/stable_mir/mod.rs b/compiler/stable_mir/src/lib.rs
index 3c86cb4038a..104985493ef 100644
--- a/compiler/rustc_smir/src/stable_mir/mod.rs
+++ b/compiler/stable_mir/src/lib.rs
@@ -1,15 +1,21 @@
-//! Module that implements the public interface to the Stable MIR.
+//! The WIP stable interface to rustc internals.
 //!
-//! This module shall contain all type definitions and APIs that we expect third-party tools to invoke to
-//! interact with the compiler.
+//! For more information see <https://github.com/rust-lang/project-stable-mir>
 //!
-//! The goal is to eventually move this module to its own crate which shall be published on
-//! [crates.io](https://crates.io).
+//! # Note
+//!
+//! This API is still completely unstable and subject to change.
+
+#![doc(
+    html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
+    test(attr(allow(unused_variables), deny(warnings)))
+)]
 //!
-//! ## Note:
+//! This crate shall contain all type definitions and APIs that we expect third-party tools to invoke to
+//! interact with the compiler.
 //!
-//! There shouldn't be any direct references to internal compiler constructs in this module.
-//! If you need an internal construct, consider using `rustc_internal` or `rustc_smir`.
+//! The goal is to eventually be published on
+//! [crates.io](https://crates.io).
 
 use std::cell::Cell;
 use std::fmt;
@@ -18,7 +24,9 @@ use std::fmt::Debug;
 use self::ty::{
     GenericPredicates, Generics, ImplDef, ImplTrait, Span, TraitDecl, TraitDef, Ty, TyKind,
 };
-use crate::rustc_smir::Tables;
+
+#[macro_use]
+extern crate scoped_tls;
 
 pub mod fold;
 pub mod mir;
@@ -33,11 +41,11 @@ pub type CrateNum = usize;
 
 /// A unique identification number for each item accessible for the current compilation unit.
 #[derive(Clone, Copy, PartialEq, Eq)]
-pub struct DefId(pub(crate) usize);
+pub struct DefId(pub usize);
 
 impl Debug for DefId {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("DefId:")
+        f.debug_struct("DefId")
             .field("id", &self.0)
             .field("name", &with(|cx| cx.name_of_def_id(*self)))
             .finish()
@@ -46,7 +54,7 @@ impl Debug for DefId {
 
 /// A unique identification number for each provenance
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct AllocId(pub(crate) usize);
+pub struct AllocId(pub usize);
 
 /// A list of crate items.
 pub type CrateItems = Vec<CrateItem>;
@@ -74,16 +82,18 @@ pub enum CompilerError<T> {
 /// Holds information about a crate.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct Crate {
-    pub(crate) id: CrateNum,
+    pub id: CrateNum,
     pub name: Symbol,
     pub is_local: bool,
 }
 
+pub type DefKind = Opaque;
+
 /// Holds information about an item in the crate.
 /// For now, it only stores the item DefId. Use functions inside `rustc_internal` module to
 /// use this item.
 #[derive(Clone, PartialEq, Eq, Debug)]
-pub struct CrateItem(pub(crate) DefId);
+pub struct CrateItem(pub DefId);
 
 impl CrateItem {
     pub fn body(&self) -> mir::Body {
@@ -93,6 +103,14 @@ impl CrateItem {
     pub fn span(&self) -> Span {
         with(|cx| cx.span_of_an_item(self.0))
     }
+
+    pub fn name(&self) -> String {
+        with(|cx| cx.name_of_def_id(self.0))
+    }
+
+    pub fn kind(&self) -> DefKind {
+        with(|cx| cx.def_kind(self.0))
+    }
 }
 
 /// Return the function where execution starts if the current
@@ -161,6 +179,12 @@ pub trait Context {
     /// Prints the name of given `DefId`
     fn name_of_def_id(&self, def_id: DefId) -> String;
 
+    /// Prints a human readable form of `Span`
+    fn print_span(&self, span: Span) -> String;
+
+    /// Prints the kind of given `DefId`
+    fn def_kind(&mut self, def_id: DefId) -> DefKind;
+
     /// `Span` of an item
     fn span_of_an_item(&mut self, def_id: DefId) -> Span;
 
@@ -169,10 +193,6 @@ pub trait Context {
 
     /// Create a new `Ty` from scratch without information from rustc.
     fn mk_ty(&mut self, kind: TyKind) -> Ty;
-
-    /// HACK: Until we have fully stable consumers, we need an escape hatch
-    /// to get `DefId`s out of `CrateItem`s.
-    fn rustc_tables(&mut self, f: &mut dyn FnMut(&mut Tables<'_>));
 }
 
 // A thread local variable that stores a pointer to the tables mapping between TyCtxt
@@ -192,7 +212,7 @@ pub fn run(mut context: impl Context, f: impl FnOnce()) {
 
 /// Loads the current context and calls a function with it.
 /// Do not nest these, as that will ICE.
-pub(crate) fn with<R>(f: impl FnOnce(&mut dyn Context) -> R) -> R {
+pub fn with<R>(f: impl FnOnce(&mut dyn Context) -> R) -> R {
     assert!(TLV.is_set());
     TLV.with(|tlv| {
         let ptr = tlv.get();
@@ -200,3 +220,23 @@ pub(crate) fn with<R>(f: impl FnOnce(&mut dyn Context) -> R) -> R {
         f(unsafe { *(ptr as *mut &mut dyn Context) })
     })
 }
+
+/// A type that provides internal information but that can still be used for debug purpose.
+#[derive(Clone)]
+pub struct Opaque(String);
+
+impl std::fmt::Display for Opaque {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+impl std::fmt::Debug for Opaque {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self.0)
+    }
+}
+
+pub fn opaque<T: Debug>(value: &T) -> Opaque {
+    Opaque(format!("{value:?}"))
+}
diff --git a/compiler/rustc_smir/src/stable_mir/mir.rs b/compiler/stable_mir/src/mir.rs
index a9dbc3463f8..a9dbc3463f8 100644
--- a/compiler/rustc_smir/src/stable_mir/mir.rs
+++ b/compiler/stable_mir/src/mir.rs
diff --git a/compiler/rustc_smir/src/stable_mir/mir/body.rs b/compiler/stable_mir/src/mir/body.rs
index 449ca4b8145..6f8f7b06fa3 100644
--- a/compiler/rustc_smir/src/stable_mir/mir/body.rs
+++ b/compiler/stable_mir/src/mir/body.rs
@@ -1,8 +1,6 @@
-use crate::rustc_internal::Opaque;
-use crate::stable_mir::ty::{
-    AdtDef, ClosureDef, Const, GeneratorDef, GenericArgs, Movability, Region,
-};
-use crate::stable_mir::{self, ty::Ty, Span};
+use crate::ty::{AdtDef, ClosureDef, Const, GeneratorDef, GenericArgs, Movability, Region};
+use crate::Opaque;
+use crate::{ty::Ty, Span};
 
 #[derive(Clone, Debug)]
 pub struct Body {
@@ -135,7 +133,7 @@ pub enum AsyncGeneratorKind {
 }
 
 pub(crate) type LocalDefId = Opaque;
-/// [`rustc_middle::mir::Coverage`] is heavily tied to internal details of the
+/// The rustc coverage data structures are heavily tied to internal details of the
 /// coverage implementation that are likely to change, and are unlikely to be
 /// useful to third-party tools for the foreseeable future.
 pub(crate) type Coverage = Opaque;
@@ -215,7 +213,7 @@ pub enum Rvalue {
     /// generator lowering, `Generator` aggregate kinds are disallowed too.
     Aggregate(AggregateKind, Vec<Operand>),
 
-    /// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
+    /// * `Offset` has the same semantics as `<*const T>::offset`, except that the second
     ///   parameter may be a `usize` as well.
     /// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
     ///   raw pointers, or function pointers and return a `bool`. The types of the operands must be
@@ -245,16 +243,14 @@ pub enum Rvalue {
     /// deref operation, immediately followed by one or more projections.
     CopyForDeref(Place),
 
-    /// Computes the discriminant of the place, returning it as an integer of type
-    /// [`discriminant_ty`]. Returns zero for types without discriminant.
+    /// Computes the discriminant of the place, returning it as an integer.
+    /// Returns zero for types without discriminant.
     ///
     /// The validity requirements for the underlying value are undecided for this rvalue, see
     /// [#91095]. Note too that the value of the discriminant is not the same thing as the
-    /// variant index; use [`discriminant_for_variant`] to convert.
+    /// variant index;
     ///
-    /// [`discriminant_ty`]: rustc_middle::ty::Ty::discriminant_ty
     /// [#91095]: https://github.com/rust-lang/rust/issues/91095
-    /// [`discriminant_for_variant`]: rustc_middle::ty::Ty::discriminant_for_variant
     Discriminant(Place),
 
     /// Yields the length of the place, as a `usize`.
@@ -295,7 +291,7 @@ pub enum Rvalue {
     ///
     /// **Needs clarification**: Are there weird additional semantics here related to the runtime
     /// nature of this operation?
-    ThreadLocalRef(stable_mir::CrateItem),
+    ThreadLocalRef(crate::CrateItem),
 
     /// Computes a value as described by the operation.
     NullaryOp(NullOp, Ty),
diff --git a/compiler/rustc_smir/src/stable_mir/ty.rs b/compiler/stable_mir/src/ty.rs
index eb9967b3888..82007e30683 100644
--- a/compiler/rustc_smir/src/stable_mir/ty.rs
+++ b/compiler/stable_mir/src/ty.rs
@@ -3,7 +3,7 @@ use super::{
     mir::{Body, Mutability},
     with, AllocId, DefId,
 };
-use crate::rustc_internal::Opaque;
+use crate::Opaque;
 use std::fmt::{self, Debug, Formatter};
 
 #[derive(Copy, Clone)]
@@ -34,15 +34,16 @@ pub struct Const {
 }
 
 type Ident = Opaque;
-pub(crate) type Region = Opaque;
+pub type Region = Opaque;
 #[derive(Clone, Copy, PartialEq, Eq)]
-pub struct Span(pub(crate) usize);
+pub struct Span(pub usize);
 
 impl Debug for Span {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
-        let mut span = None;
-        with(|context| context.rustc_tables(&mut |tables| span = Some(tables.spans[self.0])));
-        f.write_fmt(format_args!("{:?}", &span.unwrap()))
+        f.debug_struct("Span")
+            .field("id", &self.0)
+            .field("repr", &with(|cx| cx.print_span(*self)))
+            .finish()
     }
 }
 
@@ -110,10 +111,10 @@ pub enum Movability {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct ForeignDef(pub(crate) DefId);
+pub struct ForeignDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct FnDef(pub(crate) DefId);
+pub struct FnDef(pub DefId);
 
 impl FnDef {
     pub fn body(&self) -> Body {
@@ -122,34 +123,34 @@ impl FnDef {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct ClosureDef(pub(crate) DefId);
+pub struct ClosureDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct GeneratorDef(pub(crate) DefId);
+pub struct GeneratorDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct ParamDef(pub(crate) DefId);
+pub struct ParamDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct BrNamedDef(pub(crate) DefId);
+pub struct BrNamedDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct AdtDef(pub(crate) DefId);
+pub struct AdtDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct AliasDef(pub(crate) DefId);
+pub struct AliasDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct TraitDef(pub(crate) DefId);
+pub struct TraitDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct GenericDef(pub(crate) DefId);
+pub struct GenericDef(pub DefId);
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct ConstDef(pub(crate) DefId);
+pub struct ConstDef(pub DefId);
 
 #[derive(Clone, PartialEq, Eq, Debug)]
-pub struct ImplDef(pub(crate) DefId);
+pub struct ImplDef(pub DefId);
 
 #[derive(Clone, Debug)]
 pub struct GenericArgs(pub Vec<GenericArgKind>);
@@ -333,7 +334,7 @@ pub type Bytes = Vec<Option<u8>>;
 pub type Size = usize;
 
 #[derive(Clone, Copy, PartialEq, Eq, Debug)]
-pub struct Prov(pub(crate) AllocId);
+pub struct Prov(pub AllocId);
 pub type Align = u64;
 pub type Promoted = u32;
 pub type InitMaskMaterialized = Vec<u64>;
diff --git a/compiler/rustc_smir/src/stable_mir/visitor.rs b/compiler/stable_mir/src/visitor.rs
index c86063d2ed6..9c3b4cd994a 100644
--- a/compiler/rustc_smir/src/stable_mir/visitor.rs
+++ b/compiler/stable_mir/src/visitor.rs
@@ -1,6 +1,6 @@
 use std::ops::ControlFlow;
 
-use crate::rustc_internal::Opaque;
+use crate::Opaque;
 
 use super::ty::{
     Allocation, Binder, Const, ConstDef, ExistentialPredicate, FnSig, GenericArgKind, GenericArgs,
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 4f19ffa83db..292ccc5780f 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -1789,7 +1789,10 @@ pub fn run_cargo(
                 // During check builds we need to keep crate metadata
                 keep = true;
             } else if rlib_only_metadata {
-                if filename.contains("jemalloc_sys") || filename.contains("rustc_smir") {
+                if filename.contains("jemalloc_sys")
+                    || filename.contains("rustc_smir")
+                    || filename.contains("stable_mir")
+                {
                     // jemalloc_sys and rustc_smir are not linked into librustc_driver.so,
                     // so we need to distribute them as rlib to be able to use them.
                     keep |= filename.ends_with(".rlib");
diff --git a/tests/ui-fulldeps/stable-mir/compilation-result.rs b/tests/ui-fulldeps/stable-mir/compilation-result.rs
index 23a9e2a064c..3ec1519fb13 100644
--- a/tests/ui-fulldeps/stable-mir/compilation-result.rs
+++ b/tests/ui-fulldeps/stable-mir/compilation-result.rs
@@ -11,9 +11,10 @@
 
 extern crate rustc_middle;
 extern crate rustc_smir;
+extern crate stable_mir;
 
 use rustc_middle::ty::TyCtxt;
-use rustc_smir::{rustc_internal, stable_mir};
+use rustc_smir::rustc_internal;
 use std::io::Write;
 use std::ops::ControlFlow;
 
diff --git a/tests/ui-fulldeps/stable-mir/crate-info.rs b/tests/ui-fulldeps/stable-mir/crate-info.rs
index a11720c4b55..ce4ee3c2463 100644
--- a/tests/ui-fulldeps/stable-mir/crate-info.rs
+++ b/tests/ui-fulldeps/stable-mir/crate-info.rs
@@ -13,13 +13,13 @@
 extern crate rustc_hir;
 extern crate rustc_middle;
 extern crate rustc_smir;
+extern crate stable_mir;
 
 use rustc_hir::def::DefKind;
 use rustc_middle::ty::TyCtxt;
-use rustc_smir::{
-    rustc_internal,
-    stable_mir::{self, fold::Foldable},
-};
+use rustc_smir::rustc_internal;
+
+use stable_mir::fold::Foldable;
 use std::assert_matches::assert_matches;
 use std::io::Write;
 use std::ops::ControlFlow;
@@ -27,7 +27,7 @@ use std::ops::ControlFlow;
 const CRATE_NAME: &str = "input";
 
 /// This function uses the Stable MIR APIs to get information about the test crate.
-fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
+fn test_stable_mir(_tcx: TyCtxt<'_>) -> ControlFlow<()> {
     // Get the local crate using stable_mir API.
     let local = stable_mir::local_crate();
     assert_eq!(&local.name, CRATE_NAME);
@@ -36,12 +36,12 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
 
     // Find items in the local crate.
     let items = stable_mir::all_local_items();
-    assert!(get_item(tcx, &items, (DefKind::Fn, "foo::bar")).is_some());
+    assert!(get_item(&items, (DefKind::Fn, "foo::bar")).is_some());
 
     // Find the `std` crate.
     assert!(stable_mir::find_crate("std").is_some());
 
-    let bar = get_item(tcx, &items, (DefKind::Fn, "bar")).unwrap();
+    let bar = get_item(&items, (DefKind::Fn, "bar")).unwrap();
     let body = bar.body();
     assert_eq!(body.locals.len(), 2);
     assert_eq!(body.blocks.len(), 1);
@@ -56,7 +56,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         other => panic!("{other:?}"),
     }
 
-    let foo_bar = get_item(tcx, &items, (DefKind::Fn, "foo_bar")).unwrap();
+    let foo_bar = get_item(&items, (DefKind::Fn, "foo_bar")).unwrap();
     let body = foo_bar.body();
     assert_eq!(body.locals.len(), 7);
     assert_eq!(body.blocks.len(), 4);
@@ -66,7 +66,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         other => panic!("{other:?}"),
     }
 
-    let types = get_item(tcx, &items, (DefKind::Fn, "types")).unwrap();
+    let types = get_item(&items, (DefKind::Fn, "types")).unwrap();
     let body = types.body();
     assert_eq!(body.locals.len(), 6);
     assert_matches!(
@@ -96,7 +96,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         ))
     );
 
-    let drop = get_item(tcx, &items, (DefKind::Fn, "drop")).unwrap();
+    let drop = get_item(&items, (DefKind::Fn, "drop")).unwrap();
     let body = drop.body();
     assert_eq!(body.blocks.len(), 2);
     let block = &body.blocks[0];
@@ -105,7 +105,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         other => panic!("{other:?}"),
     }
 
-    let assert = get_item(tcx, &items, (DefKind::Fn, "assert")).unwrap();
+    let assert = get_item(&items, (DefKind::Fn, "assert")).unwrap();
     let body = assert.body();
     assert_eq!(body.blocks.len(), 2);
     let block = &body.blocks[0];
@@ -114,7 +114,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         other => panic!("{other:?}"),
     }
 
-    let monomorphic = get_item(tcx, &items, (DefKind::Fn, "monomorphic")).unwrap();
+    let monomorphic = get_item(&items, (DefKind::Fn, "monomorphic")).unwrap();
     for block in monomorphic.body().blocks {
         match &block.terminator {
             stable_mir::mir::Terminator::Call { func, .. } => match func {
@@ -154,7 +154,7 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
         }
     }
 
-    let foo_const = get_item(tcx, &items, (DefKind::Const, "FOO")).unwrap();
+    let foo_const = get_item(&items, (DefKind::Const, "FOO")).unwrap();
     // Ensure we don't panic trying to get the body of a constant.
     foo_const.body();
 
@@ -163,13 +163,11 @@ fn test_stable_mir(tcx: TyCtxt<'_>) -> ControlFlow<()> {
 
 // Use internal API to find a function in a crate.
 fn get_item<'a>(
-    tcx: TyCtxt,
     items: &'a stable_mir::CrateItems,
     item: (DefKind, &str),
 ) -> Option<&'a stable_mir::CrateItem> {
     items.iter().find(|crate_item| {
-        let def_id = rustc_internal::item_def_id(crate_item);
-        tcx.def_kind(def_id) == item.0 && tcx.def_path_str(def_id) == item.1
+        crate_item.kind().to_string() == format!("{:?}", item.0) && crate_item.name() == item.1
     })
 }
 
diff --git a/tests/ui/async-await/const-async-fn-in-main.rs b/tests/ui/async-await/const-async-fn-in-main.rs
new file mode 100644
index 00000000000..5d1aa4d83f3
--- /dev/null
+++ b/tests/ui/async-await/const-async-fn-in-main.rs
@@ -0,0 +1,7 @@
+// edition:2021
+// Check what happens when a const async fn is in the main function (#102796)
+
+fn main() {
+    const async fn a() {}
+//~^ ERROR functions cannot be both `const` and `async`
+}
diff --git a/tests/ui/async-await/const-async-fn-in-main.stderr b/tests/ui/async-await/const-async-fn-in-main.stderr
new file mode 100644
index 00000000000..10b15170922
--- /dev/null
+++ b/tests/ui/async-await/const-async-fn-in-main.stderr
@@ -0,0 +1,11 @@
+error: functions cannot be both `const` and `async`
+  --> $DIR/const-async-fn-in-main.rs:5:5
+   |
+LL |     const async fn a() {}
+   |     ^^^^^-^^^^^----------
+   |     |     |
+   |     |     `async` because of this
+   |     `const` because of this
+
+error: aborting due to previous error
+
diff --git a/tests/ui/impl-trait/in-trait/anonymize-binders-for-refine.rs b/tests/ui/impl-trait/in-trait/anonymize-binders-for-refine.rs
new file mode 100644
index 00000000000..e62662f2f07
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/anonymize-binders-for-refine.rs
@@ -0,0 +1,13 @@
+// compile-flags: --crate-type=lib
+// check-pass
+
+#![feature(return_position_impl_trait_in_trait)]
+#![deny(refining_impl_trait)]
+
+pub trait Tr<T> {
+    fn foo() -> impl for<'a> Tr<&'a Self>;
+}
+
+impl<T> Tr<T> for () {
+    fn foo() -> impl for<'a> Tr<&'a Self> {}
+}
diff --git a/tests/ui/issues/issue-27042.stderr b/tests/ui/issues/issue-27042.stderr
index 69eedeb8025..01532de999e 100644
--- a/tests/ui/issues/issue-27042.stderr
+++ b/tests/ui/issues/issue-27042.stderr
@@ -11,8 +11,13 @@ LL | |         while true { break }; // but here we cite the whole loop
 error[E0308]: mismatched types
   --> $DIR/issue-27042.rs:6:16
    |
+LL |     let _: i32 =
+   |         - expected because of this assignment
+LL |         'a: // in this case, the citation is just the `break`:
 LL |         loop { break };
-   |                ^^^^^ expected `i32`, found `()`
+   |         ----   ^^^^^ expected `i32`, found `()`
+   |         |
+   |         this loop is expected to be of type `i32`
    |
 help: give it a value of the expected type
    |
diff --git a/tests/ui/loops/loop-labeled-break-value.stderr b/tests/ui/loops/loop-labeled-break-value.stderr
index f233670e8c4..694d6c306f6 100644
--- a/tests/ui/loops/loop-labeled-break-value.stderr
+++ b/tests/ui/loops/loop-labeled-break-value.stderr
@@ -2,7 +2,10 @@ error[E0308]: mismatched types
   --> $DIR/loop-labeled-break-value.rs:3:29
    |
 LL |         let _: i32 = loop { break };
-   |                             ^^^^^ expected `i32`, found `()`
+   |             -        ----   ^^^^^ expected `i32`, found `()`
+   |             |        |
+   |             |        this loop is expected to be of type `i32`
+   |             expected because of this assignment
    |
 help: give it a value of the expected type
    |
@@ -13,7 +16,10 @@ error[E0308]: mismatched types
   --> $DIR/loop-labeled-break-value.rs:6:37
    |
 LL |         let _: i32 = 'inner: loop { break 'inner };
-   |                                     ^^^^^^^^^^^^ expected `i32`, found `()`
+   |             -                ----   ^^^^^^^^^^^^ expected `i32`, found `()`
+   |             |                |
+   |             |                this loop is expected to be of type `i32`
+   |             expected because of this assignment
    |
 help: give it a value of the expected type
    |
@@ -24,7 +30,10 @@ error[E0308]: mismatched types
   --> $DIR/loop-labeled-break-value.rs:9:45
    |
 LL |         let _: i32 = 'inner2: loop { loop { break 'inner2 } };
-   |                                             ^^^^^^^^^^^^^ expected `i32`, found `()`
+   |             -                 ----          ^^^^^^^^^^^^^ expected `i32`, found `()`
+   |             |                 |
+   |             |                 this loop is expected to be of type `i32`
+   |             expected because of this assignment
    |
 help: give it a value of the expected type
    |
diff --git a/tests/ui/loops/loop-properly-diverging-2.stderr b/tests/ui/loops/loop-properly-diverging-2.stderr
index dc60657ee14..1d1ae60cda1 100644
--- a/tests/ui/loops/loop-properly-diverging-2.stderr
+++ b/tests/ui/loops/loop-properly-diverging-2.stderr
@@ -2,7 +2,10 @@ error[E0308]: mismatched types
   --> $DIR/loop-properly-diverging-2.rs:2:23
    |
 LL |   let x: i32 = loop { break };
-   |                       ^^^^^ expected `i32`, found `()`
+   |       -        ----   ^^^^^ expected `i32`, found `()`
+   |       |        |
+   |       |        this loop is expected to be of type `i32`
+   |       expected because of this assignment
    |
 help: give it a value of the expected type
    |
diff --git a/triagebot.toml b/triagebot.toml
index dbced481993..648997ad6f0 100644
--- a/triagebot.toml
+++ b/triagebot.toml
@@ -542,6 +542,10 @@ cc = ["@davidtwco", "@compiler-errors", "@JohnTitor", "@TaKO8Ki"]
 message = "This PR changes Stable MIR"
 cc = ["@oli-obk", "@celinval", "@spastorino"]
 
+[mentions."compiler/stable_mir"]
+message = "This PR changes Stable MIR"
+cc = ["@oli-obk", "@celinval", "@spastorino"]
+
 [mentions."compiler/rustc_target/src/spec"]
 message = """
 These commits modify **compiler targets**.