src/test/run-pass/trait-copy-guessing.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 // "guessing" in trait selection can affect `copy_or_move`. Check that this
  12 // is correctly handled. I am not sure what is the "correct" behaviour,
  13 // but we should at least not ICE.
  14
  15 use std::mem;
  16
  17 struct U([u8; 1337]);
  18
  19 struct S<'a,T:'a>(&'a T);
  20 impl<'a, T> Clone for S<'a, T> { fn clone(&self) -> Self { S(self.0) } }
  21 /// This impl triggers inference "guessing" - S<_>: Copy => _ = U
  22 impl<'a> Copy for S<'a, Option<U>> {}
  23
  24 fn assert_impls_fn<R,T: Fn()->R>(_: &T){}
  25
  26 fn main() {
  27     let n = None;
  28     let e = S(&n);
  29     let f = || {
  30         // S being copy is critical for this to work
  31         drop(e);
  32         mem::size_of_val(e.0)
  33     };
  34     assert_impls_fn(&f);
  35     assert_eq!(f(), 1337+1);
  36
  37     assert_eq!((|| {
  38         // S being Copy is not critical here, but
  39         // we check it anyway.
  40         let n = None;
  41         let e = S(&n);
  42         let ret = mem::size_of_val(e.0);
  43         drop(e);
  44         ret
  45     })(), 1337+1);
  46 }