src/test/compile-fail/specialization/specialization-default-types.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 // It should not be possible to use the concrete value of a defaulted
  12 // associated type in the impl defining it -- otherwise, what happens
  13 // if it's overridden?
  14
  15 #![feature(specialization)]
  16
  17 trait Example {
  18     type Output;
  19     fn generate(self) -> Self::Output;
  20 }
  21
  22 impl<T> Example for T {
  23     default type Output = Box<T>;
  24     default fn generate(self) -> Self::Output {
  25         Box::new(self) //~ ERROR mismatched types
  26     }
  27 }
  28
  29 impl Example for bool {
  30     type Output = bool;
  31     fn generate(self) -> bool { self }
  32 }
  33
  34 fn trouble<T>(t: T) -> Box<T> {
  35     Example::generate(t) //~ ERROR mismatched types
  36 }
  37
  38 fn weaponize() -> bool {
  39     let b: Box<bool> = trouble(true);
  40     *b
  41 }
  42
  43 fn main() {
  44     weaponize();
  45 }