Point out expectation even if we have RegionsInsufficientlyPolymorphic

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1645,10 +1645,7 @@ pub(crate) fn coerce_inner<'a>(
 
                 augment_error(&mut err);
 
-                let is_insufficiently_polymorphic =
+                if let Some(expr) = expression {
-                    matches!(coercion_error, TypeError::RegionsInsufficientlyPolymorphic(..));
-
-                if !is_insufficiently_polymorphic && let Some(expr) = expression {
                     fcx.emit_coerce_suggestions(
                         &mut err,
                         expr,

compiler/rustc_hir_typeck/src/demand.rs

@@ -84,6 +84,13 @@ pub fn emit_coerce_suggestions(
 
         self.annotate_expected_due_to_let_ty(err, expr, error);
 
+        // FIXME(#73154): For now, we do leak check when coercing function
+        // pointers in typeck, instead of only during borrowck. This can lead
+        // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
+        if matches!(error, Some(TypeError::RegionsInsufficientlyPolymorphic(..))) {
+            return;
+        }
+
         if self.is_destruct_assignment_desugaring(expr) {
             return;
         }
@@ -263,22 +270,7 @@ pub fn demand_coerce_diag(
         let expr_ty = self.resolve_vars_with_obligations(checked_ty);
         let mut err = self.err_ctxt().report_mismatched_types(&cause, expected, expr_ty, e);
 
-        let is_insufficiently_polymorphic =
+        self.emit_coerce_suggestions(&mut err, expr, expr_ty, expected, expected_ty_expr, Some(e));
-            matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..));
-
-        // FIXME(#73154): For now, we do leak check when coercing function
-        // pointers in typeck, instead of only during borrowck. This can lead
-        // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
-        if !is_insufficiently_polymorphic {
-            self.emit_coerce_suggestions(
-                &mut err,
-                expr,
-                expr_ty,
-                expected,
-                expected_ty_expr,
-                Some(e),
-            );
-        }
 
         (expected, Some(err))
     }

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

@@ -1927,7 +1927,12 @@ enum Similar<'tcx> {
                     true
                 };
 
-            if should_suggest_fixes {
+            // FIXME(#73154): For now, we do leak check when coercing function
+            // pointers in typeck, instead of only during borrowck. This can lead
+            // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful.
+            if should_suggest_fixes
+                && !matches!(terr, TypeError::RegionsInsufficientlyPolymorphic(..))
+            {
                 self.suggest_tuple_pattern(cause, &exp_found, diag);
                 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
                 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);

tests/ui/higher-ranked/subtype/placeholder-pattern-fail.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/placeholder-pattern-fail.rs:9:47
    |
 LL |     let _: for<'a, 'b> fn(Inv<'a>, Inv<'b>) = sub;
-   |                                               ^^^ one type is more general than the other
+   |            --------------------------------   ^^^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b> fn(Inv<'a>, Inv<'b>)`
               found fn pointer `for<'a> fn(Inv<'a>, Inv<'a>)`

tests/ui/higher-ranked/trait-bounds/hrtb-exists-forall-fn.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/hrtb-exists-forall-fn.rs:17:34
    |
 LL |     let _: for<'b> fn(&'b u32) = foo();
-   |                                  ^^^^^ one type is more general than the other
+   |            -------------------   ^^^^^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'b> fn(&'b u32)`
               found fn pointer `fn(&u32)`

tests/ui/regions/higher-ranked-implied.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/higher-ranked-implied.rs:12:16
    |
 LL |     let y: B = x;
-   |                ^ one type is more general than the other
+   |            -   ^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b> fn(Inv<&'a &'b ()>, Inv<&'b &'a ()>, Inv<&'b ()>)`
               found fn pointer `for<'a, 'b> fn(Inv<&'a &'b ()>, Inv<&'b &'a ()>, Inv<&'a ()>)`
@@ -11,7 +13,9 @@ error[E0308]: mismatched types
   --> $DIR/higher-ranked-implied.rs:13:16
    |
 LL |     let _: A = y;
-   |                ^ one type is more general than the other
+   |            -   ^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b> fn(Inv<&'a &'b ()>, Inv<&'b &'a ()>, Inv<&'a ()>)`
               found fn pointer `for<'a, 'b> fn(Inv<&'a &'b ()>, Inv<&'b &'a ()>, Inv<&'b ()>)`

tests/ui/regions/region-lifetime-bounds-on-fns-where-clause.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/region-lifetime-bounds-on-fns-where-clause.rs:20:43
    |
 LL |     let _: fn(&mut &isize, &mut &isize) = a;
-   |                                           ^ one type is more general than the other
+   |            ----------------------------   ^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b, 'c, 'd> fn(&'a mut &'b isize, &'c mut &'d isize)`
                  found fn item `for<'a, 'b> fn(&'a mut &isize, &'b mut &isize) {a::<'_, '_>}`

tests/ui/regions/region-multiple-lifetime-bounds-on-fns-where-clause.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/region-multiple-lifetime-bounds-on-fns-where-clause.rs:22:56
    |
 LL |     let _: fn(&mut &isize, &mut &isize, &mut &isize) = a;
-   |                                                        ^ one type is more general than the other
+   |            -----------------------------------------   ^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b, 'c, 'd, 'e, 'f> fn(&'a mut &'b isize, &'c mut &'d isize, &'e mut &'f isize)`
                  found fn item `for<'a, 'b, 'c> fn(&'a mut &isize, &'b mut &isize, &'c mut &isize) {a::<'_, '_, '_>}`

tests/ui/regions/regions-lifetime-bounds-on-fns.stderr

@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/regions-lifetime-bounds-on-fns.rs:20:43
    |
 LL |     let _: fn(&mut &isize, &mut &isize) = a;
-   |                                           ^ one type is more general than the other
+   |            ----------------------------   ^ one type is more general than the other
+   |            |
+   |            expected due to this
    |
    = note: expected fn pointer `for<'a, 'b, 'c, 'd> fn(&'a mut &'b isize, &'c mut &'d isize)`
                  found fn item `for<'a, 'b> fn(&'a mut &isize, &'b mut &isize) {a::<'_, '_>}`