src/test/compile-fail/cross-borrow-trait.rs

   1 // Copyright 2012-2013-2014 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 cross-borrowing (implicitly converting from `Box<T>` to `&T`) is
  12 // forbidden when `T` is a trait.
  13
  14 struct Foo;
  15 trait Trait { fn foo(&self) {} }
  16 impl Trait for Foo {}
  17
  18 pub fn main() {
  19     // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
  20     let x: Box<Trait> = Box::new(Foo);
  21     let _y: &Trait = x; //~  ERROR mismatched types
  22                         //~| expected type `&Trait`
  23                         //~| found type `Box<Trait>`
  24                         //~| expected &Trait, found box
  25 }