| // 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. |
| |
| // This is an example where the older inference algorithm failed. The |
| // specifics of why it failed are somewhat, but not entirely, tailed |
| // to the algorithm. Ultimately the problem is that when computing the |
| // mutual supertype of both sides of the `if` it would be faced with a |
| // choice of tightening bounds or unifying variables and it took the |
| // wrong path. The new algorithm avoids this problem and hence this |
| // example typechecks correctly. |
| |
| // pretty-expanded FIXME #23616 |
| |
| enum ScopeChain<'a> { |
| Link(Scope<'a>), |
| End |
| } |
| |
| type Scope<'a> = &'a ScopeChain<'a>; |
| |
| struct OuterContext; |
| |
| struct Context<'a> { |
| foo: &'a OuterContext |
| } |
| |
| impl<'a> Context<'a> { |
| fn foo(&mut self, scope: Scope) { |
| let link = if 1 < 2 { |
| let l = ScopeChain::Link(scope); |
| self.take_scope(&l); |
| l |
| } else { |
| ScopeChain::Link(scope) |
| }; |
| self.take_scope(&link); |
| } |
| |
| fn take_scope(&mut self, x: Scope) { |
| } |
| } |
| |
| fn main() { } |