Add test for ICE 6793

tests/ui/crashes/ice-6793.rs

@@ -0,0 +1,23 @@
+//! This is a reproducer for the ICE 6793: https://github.com/rust-lang/rust-clippy/issues/6793.
+//! The ICE is caused by using `TyCtxt::type_of(assoc_type_id)`, which is the same as the ICE 6792.
+
+trait Trait {
+    type Ty: 'static + Clone;
+
+    fn broken() -> Self::Ty;
+}
+
+#[derive(Clone)]
+struct MyType {
+    x: i32,
+}
+
+impl Trait for MyType {
+    type Ty = MyType;
+
+    fn broken() -> Self::Ty {
+        Self::Ty { x: 1 }
+    }
+}
+
+fn main() {}