tests/ui/type-alias-impl-trait/impl_trait_for_same_tait.rs

   1 #![feature(type_alias_impl_trait)]
   2
   3 trait Foo {}
   4 impl Foo for () {}
   5 impl Foo for i32 {}
   6
   7 type Bar<T: Foo> = impl std::fmt::Debug;
   8 fn defining_use<T: Foo>() -> Bar<T> {
   9     42
  10 }
  11
  12 trait Bop {}
  13
  14 impl Bop for Bar<()> {}
  15
  16 // If the hidden type is the same, this is effectively a second impl for the same type.
  17 impl Bop for Bar<i32> {}
  18 //~^ ERROR conflicting implementations
  19
  20 type Barr = impl std::fmt::Debug;
  21 fn defining_use2() -> Barr {
  22     42
  23 }
  24
  25 // Even completely different opaque types must conflict.
  26 impl Bop for Barr {}
  27 //~^ ERROR conflicting implementations
  28
  29 // And obviously the hidden type must conflict, too.
  30 impl Bop for i32 {}
  31 //~^ ERROR conflicting implementations
  32
  33 fn main() {}