Auto merge of #114130 - GuillaumeGomez:rollup-69ihuaj, r=GuillaumeGomez

Rollup of 7 pull requests

Successful merges:

 - #114032 (typos)
 - #114059 (rustdoc: fix cross-crate `impl Sized` & `impl ?Sized`)
 - #114088 (Bump syn dependency)
 - #114091 (docs: fmt::Debug*: Fix comments for finish method.)
 - #114109 (Docs: Fix URL for `rmatches`)
 - #114117 (Restore region uniquification in the new solver 🎉  )
 - #114123 (Turns out opaque types can have hidden types registered during mir validation)

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

4 files changed, 25 insertions, 20 deletions

diff --git a/compiler/rustc_const_eval/src/util/compare_types.rs b/compiler/rustc_const_eval/src/util/compare_types.rs
index 88d4f5e715c..83376c8e992 100644
--- a/compiler/rustc_const_eval/src/util/compare_types.rs
+++ b/compiler/rustc_const_eval/src/util/compare_types.rs
@@ -57,12 +57,15 @@ pub fn is_subtype<'tcx>(
     // we would get unification errors because we're unable to look into opaque types,
     // even if they're constrained in our current function.
     for (key, ty) in infcx.take_opaque_types() {
-        span_bug!(
-            ty.hidden_type.span,
-            "{}, {}",
-            tcx.type_of(key.def_id).instantiate(tcx, key.args),
-            ty.hidden_type.ty
-        );
+        let hidden_ty = tcx.type_of(key.def_id).instantiate(tcx, key.args);
+        if hidden_ty != ty.hidden_type.ty {
+            span_bug!(
+                ty.hidden_type.span,
+                "{}, {}",
+                tcx.type_of(key.def_id).instantiate(tcx, key.args),
+                ty.hidden_type.ty
+            );
+        }
     }
     errors.is_empty()
 }
diff --git a/compiler/rustc_macros/Cargo.toml b/compiler/rustc_macros/Cargo.toml
index 16c4a850012..17651ce9598 100644
--- a/compiler/rustc_macros/Cargo.toml
+++ b/compiler/rustc_macros/Cargo.toml
@@ -8,7 +8,6 @@ proc-macro = true
 
 [dependencies]
 synstructure = "0.13.0"
-# FIXME(Nilstrieb): Updating this causes changes in the diagnostics output.
-syn = { version = "=2.0.8", features = ["full"] }
+syn = { version = "2.0.9", features = ["full"] }
 proc-macro2 = "1"
 quote = "1"
diff --git a/compiler/rustc_trait_selection/src/solve/canonicalize.rs b/compiler/rustc_trait_selection/src/solve/canonicalize.rs
index 255620489ff..88771f90756 100644
--- a/compiler/rustc_trait_selection/src/solve/canonicalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/canonicalize.rs
@@ -125,9 +125,8 @@ impl<'a, 'tcx> Canonicalizer<'a, 'tcx> {
         // - var_infos: [E0, U1, E1, U1, E1, E6, U6], curr_compressed_uv: 1, next_orig_uv: 6
         // - var_infos: [E0, U1, E1, U1, E1, E2, U2], curr_compressed_uv: 2, next_orig_uv: -
         //
-        // This algorithm runs in `O(nm)` where `n` is the number of different universe
-        // indices in the input and `m` is the number of canonical variables.
-        // This should be fine as both `n` and `m` are expected to be small.
+        // This algorithm runs in `O(n²)` where `n` is the number of different universe
+        // indices in the input. This should be fine as `n` is expected to be small.
         let mut curr_compressed_uv = ty::UniverseIndex::ROOT;
         let mut existential_in_new_uv = false;
         let mut next_orig_uv = Some(ty::UniverseIndex::ROOT);
@@ -263,14 +262,18 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'_, 'tcx> {
             ty::ReError(_) => return r,
         };
 
-        let var = ty::BoundVar::from(
-            self.variables.iter().position(|&v| v == r.into()).unwrap_or_else(|| {
-                let var = self.variables.len();
-                self.variables.push(r.into());
-                self.primitive_var_infos.push(CanonicalVarInfo { kind });
-                var
-            }),
-        );
+        let existing_bound_var = match self.canonicalize_mode {
+            CanonicalizeMode::Input => None,
+            CanonicalizeMode::Response { .. } => {
+                self.variables.iter().position(|&v| v == r.into()).map(ty::BoundVar::from)
+            }
+        };
+        let var = existing_bound_var.unwrap_or_else(|| {
+            let var = ty::BoundVar::from(self.variables.len());
+            self.variables.push(r.into());
+            self.primitive_var_infos.push(CanonicalVarInfo { kind });
+            var
+        });
         let br = ty::BoundRegion { var, kind: BrAnon(None) };
         ty::Region::new_late_bound(self.interner(), self.binder_index, br)
     }
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
index f48a992d327..9e3b0bbc4fb 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
@@ -344,7 +344,7 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
             Ok(response) => response,
         };
 
-        let has_changed = !canonical_response.value.var_values.is_identity()
+        let has_changed = !canonical_response.value.var_values.is_identity_modulo_regions()
             || !canonical_response.value.external_constraints.opaque_types.is_empty();
         let (certainty, nested_goals) = match self.instantiate_and_apply_query_response(
             goal.param_env,