Rollup merge of rust-lang#124808 - compiler-errors:super, r=lcnr

Use `super_fold` in `RegionsToStatic` visitor

so as to avoid an infinite stack cycle

fixes rust-lang#124805
r? lcnr

Author: matthiaskrgr

compiler/rustc_next_trait_solver/src/canonicalizer.rs

@@ -455,7 +455,7 @@ impl<I: Interner> TypeFolder<I> for RegionsToStatic<I> {
         I::Binder<T>: TypeSuperFoldable<I>,
     {
         self.binder.shift_in(1);
-        let t = t.fold_with(self);
+        let t = t.super_fold_with(self);
         self.binder.shift_out(1);
         t
     }

tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.rs

@@ -0,0 +1,8 @@
+//@ compile-flags: -Znext-solver=coherence
+
+#[derive(Debug)]
+struct X<const FN: fn() = { || {} }>;
+//~^ ERROR using function pointers as const generic parameters is forbidden
+//~| ERROR using function pointers as const generic parameters is forbidden
+
+fn main() {}

tests/ui/traits/next-solver/canonical/const-region-infer-to-static-in-binder.stderr

@@ -0,0 +1,19 @@
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/const-region-infer-to-static-in-binder.rs:4:20
+   |
+LL | struct X<const FN: fn() = { || {} }>;
+   |                    ^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/const-region-infer-to-static-in-binder.rs:4:20
+   |
+LL | struct X<const FN: fn() = { || {} }>;
+   |                    ^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
+