src/test/ui/impl-trait/auto-trait.rs

   1 // Tests that type alias impls traits do not leak auto-traits for
   2 // the purposes of coherence checking
   3 #![feature(type_alias_impl_trait)]
   4
   5 trait OpaqueTrait { }
   6 impl<T> OpaqueTrait for T { }
   7 type OpaqueType = impl OpaqueTrait;
   8 fn mk_opaque() -> OpaqueType { () }
   9
  10 #[derive(Debug)]
  11 struct D<T>(T);
  12
  13 trait AnotherTrait { }
  14 impl<T: Send> AnotherTrait for T { }
  15
  16 // This is in error, because we cannot assume that `OpaqueType: !Send`.
  17 // (We treat opaque types as "foreign types" that could grow more impls
  18 // in the future.)
  19 impl AnotherTrait for D<OpaqueType> {
  20     //~^ ERROR conflicting implementations of trait `AnotherTrait` for type `D<OpaqueType>`
  21 }
  22
  23 fn main() {}