src/test/run-pass/traits/traits-conditional-dispatch.rs

   1 // Copyright 2014 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 // Test that we are able to resolve conditional dispatch.  Here, the
  13 // blanket impl for T:Copy coexists with an impl for Box<T>, because
  14 // Box does not impl Copy.
  15
  16 #![feature(box_syntax)]
  17
  18 trait Get {
  19     fn get(&self) -> Self;
  20 }
  21
  22 trait MyCopy { fn copy(&self) -> Self; }
  23 impl MyCopy for u16 { fn copy(&self) -> Self { *self } }
  24 impl MyCopy for u32 { fn copy(&self) -> Self { *self } }
  25 impl MyCopy for i32 { fn copy(&self) -> Self { *self } }
  26 impl<T:Copy> MyCopy for Option<T> { fn copy(&self) -> Self { *self } }
  27
  28 impl<T:MyCopy> Get for T {
  29     fn get(&self) -> T { self.copy() }
  30 }
  31
  32 impl Get for Box<i32> {
  33     fn get(&self) -> Box<i32> { box get_it(&**self) }
  34 }
  35
  36 fn get_it<T:Get>(t: &T) -> T {
  37     (*t).get()
  38 }
  39
  40 fn main() {
  41     assert_eq!(get_it(&1_u32), 1_u32);
  42     assert_eq!(get_it(&1_u16), 1_u16);
  43     assert_eq!(get_it(&Some(1_u16)), Some(1_u16));
  44     assert_eq!(get_it(&Box::new(1)), Box::new(1));
  45 }