small rustc_borrowck cleanup

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -253,8 +253,10 @@ impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> {
         let constraint_sets: Vec<_> = unnormalized_input_output_tys
             .flat_map(|ty| {
                 debug!("build: input_or_output={:?}", ty);
-                // We add implied bounds from both the unnormalized and normalized ty
-                // See issue #87748
+                // We only add implied bounds for the normalized type as the unnormalized
+                // type may not actually get checked by the caller.
+                //
+                // Can otherwise be unsound, see #91068.
                 let TypeOpOutput { output: norm_ty, constraints: constraints1, .. } = self
                     .param_env
                     .and(type_op::normalize::Normalize::new(ty))

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1899,7 +1899,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                     ObligationCause::new(
                                         span,
                                         self.tcx().hir().local_def_id_to_hir_id(def_id),
-                                        traits::ObligationCauseCode::RepeatVec(is_const_fn),
+                                        traits::ObligationCauseCode::RepeatElementCopy {
+                                            is_const_fn,
+                                        },
                                     ),
                                     self.param_env,
                                     ty::Binder::dummy(ty::TraitRef::new(

compiler/rustc_middle/src/traits/mod.rs

@@ -236,11 +236,12 @@ pub enum ObligationCauseCode<'tcx> {
     SizedBoxType,
     /// Inline asm operand type must be `Sized`.
     InlineAsmSized,
-    /// `[T, ..n]` implies that `T` must be `Copy`.
-    /// If the function in the array repeat expression is a `const fn`,
-    /// display a help message suggesting to move the function call to a
-    /// new `const` item while saying that `T` doesn't implement `Copy`.
-    RepeatVec(bool),
+    /// `[expr; N]` requires `type_of(expr): Copy`.
+    RepeatElementCopy {
+        /// If element is a `const fn` we display a help message suggesting to move the
+        /// function call to a new `const` item while saying that `T` doesn't implement `Copy`.
+        is_const_fn: bool,
+    },
 
     /// Types of fields (other than the last, except for packed structs) in a struct must be sized.
     FieldSized {

compiler/rustc_mir_build/src/thir/pattern/mod.rs

@@ -198,7 +198,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         let kind = match pat.kind {
             hir::PatKind::Wild => PatKind::Wild,
 
-            hir::PatKind::Lit(ref value) => self.lower_lit(value),
+            hir::PatKind::Lit(value) => self.lower_lit(value),
 
             hir::PatKind::Range(ref lo_expr, ref hi_expr, end) => {
                 let (lo_expr, hi_expr) = (lo_expr.as_deref(), hi_expr.as_deref());

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

@@ -1988,7 +1988,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             ObligationCauseCode::Coercion { source: _, target } => {
                 err.note(&format!("required by cast to type `{}`", self.ty_to_string(target)));
             }
-            ObligationCauseCode::RepeatVec(is_const_fn) => {
+            ObligationCauseCode::RepeatElementCopy { is_const_fn } => {
                 err.note(
                     "the `Copy` trait is required because the repeated element will be copied",
                 );