revert #75443 update mir validator

src/test/ui/type-alias-impl-trait/issue-72793.rs

@@ -1,27 +0,0 @@
-// build-pass
-
-// Regression test for #72793.
-// FIXME: This still shows ICE with `-Zmir-opt-level=2`.
-
-#![feature(type_alias_impl_trait)]
-
-trait T { type Item; }
-
-type Alias<'a> = impl T<Item = &'a ()>;
-
-struct S;
-impl<'a> T for &'a S {
-    type Item = &'a ();
-}
-
-fn filter_positive<'a>() -> Alias<'a> {
-    &S
-}
-
-fn with_positive(fun: impl Fn(Alias<'_>)) {
-    fun(filter_positive());
-}
-
-fn main() {
-    with_positive(|_| ());
-}