Add regression test

src/test/ui/suggestions/issue-85347.rs

@@ -0,0 +1,10 @@
+#![allow(incomplete_features)]
+#![feature(generic_associated_types)]
+use std::ops::Deref;
+trait Foo {
+    type Bar<'a>: Deref<Target = <Self>::Bar<Target = Self>>;
+    //~^ ERROR this associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
+    //~| HELP add missing
+}
+
+fn main() {}

src/test/ui/suggestions/issue-85347.stderr

@@ -0,0 +1,19 @@
+error[E0107]: this associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
+  --> $DIR/issue-85347.rs:5:42
+   |
+LL |     type Bar<'a>: Deref<Target = <Self>::Bar<Target = Self>>;
+   |                                          ^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-85347.rs:5:10
+   |
+LL |     type Bar<'a>: Deref<Target = <Self>::Bar<Target = Self>>;
+   |          ^^^ --
+help: add missing lifetime argument
+   |
+LL |     type Bar<'a>: Deref<Target = <Self>::Bar<'a, Target = Self>>;
+   |                                              ^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.