src/test/compile-fail/associated-types-coherence-failure.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 // Test that coherence detects overlap when some of the types in the
  12 // impls are projections of associated type. Issue #20624.
  13
  14 use std::marker::PhantomData;
  15 use std::ops::Deref;
  16
  17 pub struct Cow<'a, B: ?Sized>(PhantomData<(&'a (),B)>);
  18
  19 /// Trait for moving into a `Cow`
  20 pub trait IntoCow<'a, B: ?Sized> {
  21     /// Moves `self` into `Cow`
  22     fn into_cow(self) -> Cow<'a, B>;
  23 }
  24
  25 impl<'a, B: ?Sized> IntoCow<'a, B> for Cow<'a, B> where B: ToOwned {
  26 //~^ ERROR E0119
  27     fn into_cow(self) -> Cow<'a, B> {
  28         self
  29     }
  30 }
  31
  32 impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
  33 //~^ ERROR E0119
  34     fn into_cow(self) -> Cow<'a, B> {
  35         Cow
  36     }
  37 }
  38
  39 impl<'a, B: ?Sized> IntoCow<'a, B> for &'a B where B: ToOwned {
  40     fn into_cow(self) -> Cow<'a, B> {
  41         Cow
  42     }
  43 }
  44
  45 impl ToOwned for u8 {
  46     type Owned = &'static u8;
  47     fn to_owned(&self) -> &'static u8 { panic!() }
  48 }
  49
  50 /// A generalization of Clone to borrowed data.
  51 pub trait ToOwned {
  52     type Owned;
  53
  54     /// Create owned data from borrowed data, usually by copying.
  55     fn to_owned(&self) -> Self::Owned;
  56 }
  57
  58
  59 fn main() {}