src/test/compile-fail/typeck-default-trait-impl-precedence.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 // Test that declaring that `&T` is `Defaulted` if `T:Signed` implies
  12 // that other `&T` is NOT `Defaulted` if `T:Signed` does not hold. In
  13 // other words, the `..` impl only applies if there are no existing
  14 // impls whose types unify.
  15
  16 #![feature(optin_builtin_traits)]
  17
  18 trait Defaulted { }
  19 #[allow(auto_impl)]
  20 impl Defaulted for .. { }
  21 impl<'a,T:Signed> Defaulted for &'a T { }
  22 impl<'a,T:Signed> Defaulted for &'a mut T { }
  23 fn is_defaulted<T:Defaulted>() { }
  24
  25 trait Signed { }
  26 impl Signed for i32 { }
  27
  28 fn main() {
  29     is_defaulted::<&'static i32>();
  30     is_defaulted::<&'static u32>();
  31     //~^ ERROR `u32: Signed` is not satisfied
  32 }