nit treat different opaque types

Author: oli-obk

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

@@ -30,5 +30,4 @@ impl Bop for Barr {}
 impl Bop for i32 {}
 //~^ ERROR conflicting implementations
 
-fn main() {
-}
+fn main() {}