src/test/ui/run-pass/coherence/coherence-rfc447-constrained.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // run-pass
  12 // check that trait matching can handle impls whose types are only
  13 // constrained by a projection.
  14
  15 trait IsU32 {}
  16 impl IsU32 for u32 {}
  17
  18 trait Mirror { type Image: ?Sized; }
  19 impl<T: ?Sized> Mirror for T { type Image = T; }
  20
  21 trait Bar {}
  22 impl<U: Mirror, V: Mirror<Image=L>, L: Mirror<Image=U>> Bar for V
  23     where U::Image: IsU32 {}
  24
  25 trait Foo { fn name() -> &'static str; }
  26 impl Foo for u64 { fn name() -> &'static str { "u64" } }
  27 impl<T: Bar> Foo for T { fn name() -> &'static str { "Bar" }}
  28
  29 fn main() {
  30     assert_eq!(<u64 as Foo>::name(), "u64");
  31     assert_eq!(<u32 as Foo>::name(), "Bar");
  32 }