Make the test actually show the problematic case

Author: oli-obk

src/test/ui/type-alias-impl-trait/implied_lifetime_wf_check.rs

@@ -1,18 +1,27 @@
-trait Mirror<'a> {
-    type Item;
-}
+#![feature(type_alias_impl_trait)]
+
+// known-bug: #99840
+// this should not compile
+// check-pass
+
+type Alias = impl Sized;
 
-impl<'a, T> Mirror<'a> for T {
-    type Item = T;
+fn constrain() -> Alias {
+    1i32
 }
 
-trait AnotherTrait {
-    type Blah;
+trait HideIt {
+    type Assoc;
 }
 
-impl<'a> AnotherTrait for <u32 as Mirror<'a>>::Item {
-    //~^ ERROR: the lifetime parameter `'a` is not constrained
-    type Blah = &'a u32;
+impl HideIt for () {
+    type Assoc = Alias;
 }
 
+pub trait Yay {}
+
+impl Yay for <() as HideIt>::Assoc {}
+// impl Yay for i32 {} // this already errors
+// impl Yay for u32 {} // this also already errors
+
 fn main() {}