| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| // Test a case where you have an impl of `Foo<X>` for all `X` that |
| // is being applied to `for<'a> Foo<&'a mut X>`. Issue #19730. |
| |
| trait Foo<X> { |
| fn foo(&mut self, x: X) { } |
| } |
| |
| trait Bar<X> { |
| fn bar(&mut self, x: X) { } |
| } |
| |
| impl<'a,X,F> Foo<X> for &'a mut F |
| where F : Foo<X> + Bar<X> |
| { |
| } |
| |
| impl<'a,X,F> Bar<X> for &'a mut F |
| where F : Bar<X> |
| { |
| } |
| |
| fn no_hrtb<'b,T>(mut t: T) |
| where T : Bar<&'b isize> |
| { |
| // OK -- `T : Bar<&'b isize>`, and thus the impl above ensures that |
| // `&mut T : Bar<&'b isize>`. |
| no_hrtb(&mut t); |
| } |
| |
| fn bar_hrtb<T>(mut t: T) |
| where T : for<'b> Bar<&'b isize> |
| { |
| // OK -- `T : for<'b> Bar<&'b isize>`, and thus the impl above |
| // ensures that `&mut T : for<'b> Bar<&'b isize>`. This is an |
| // example of a "perfect forwarding" impl. |
| bar_hrtb(&mut t); |
| } |
| |
| fn foo_hrtb_bar_not<'b,T>(mut t: T) |
| where T : for<'a> Foo<&'a isize> + Bar<&'b isize> |
| { |
| // Not OK -- The forwarding impl for `Foo` requires that `Bar` also |
| // be implemented. Thus to satisfy `&mut T : for<'a> Foo<&'a |
| // isize>`, we require `T : for<'a> Bar<&'a isize>`, but the where |
| // clause only specifies `T : Bar<&'b isize>`. |
| foo_hrtb_bar_not(&mut t); //~ ERROR `for<'a> T: Bar<&'a isize>` is not satisfied |
| } |
| |
| fn foo_hrtb_bar_hrtb<T>(mut t: T) |
| where T : for<'a> Foo<&'a isize> + for<'b> Bar<&'b isize> |
| { |
| // OK -- now we have `T : for<'b> Bar&'b isize>`. |
| foo_hrtb_bar_hrtb(&mut t); |
| } |
| |
| fn main() { } |