Rollup merge of rust-lang#63379 - jackh726:issue-53096, r=Centril,oli-obk

Add test for issue 53096

Closes rust-lang#53096

r? @oli-obk

Author: Centril

src/test/ui/type-alias-impl-trait/issue-53096.rs

@@ -0,0 +1,9 @@
+// check-pass
+#![feature(const_fn)]
+#![feature(type_alias_impl_trait)]
+
+type Foo = impl Fn() -> usize;
+const fn bar() -> Foo { || 0usize }
+const BAZR: Foo = bar();
+
+fn main() {}