Add minimal reproducer for ICE in rust-lang#6179

Author: Y-Nak

tests/ui/crashes/ice-6179.rs

@@ -0,0 +1,21 @@
+//! This is a minimal reproducer for the ICE in https://github.com/rust-lang/rust-clippy/pull/6179.
+//! The ICE is mainly caused by using `hir_ty_to_ty`. See the discussion in the PR for details.
+
+#![warn(clippy::use_self)]
+#![allow(dead_code)]
+
+struct Foo {}
+
+impl Foo {
+    fn foo() -> Self {
+        impl Foo {
+            fn bar() {}
+        }
+
+        let _: _ = 1;
+
+        Self {}
+    }
+}
+
+fn main() {}