58 lines
1.8 KiB
Rust
58 lines
1.8 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// This test used to be part of a run-pass test, but revised outlives
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// rule means that it no longer compiles.
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#![allow(unused_variables)]
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trait Trait<'a> {
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fn long(&'a self) -> isize;
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fn short<'b>(&'b self) -> isize;
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}
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fn object_invoke1<'d>(x: &'d Trait<'d>) -> (isize, isize) { loop { } }
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trait MakerTrait {
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fn mk() -> Self;
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}
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fn make_val<T:MakerTrait>() -> T {
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MakerTrait::mk()
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}
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impl<'t> MakerTrait for Box<Trait<'t>+'static> {
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fn mk() -> Box<Trait<'t>+'static> { loop { } }
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}
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pub fn main() {
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let m : Box<Trait+'static> = make_val();
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assert_eq!(object_invoke1(&*m), (4,5));
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//~^ ERROR `*m` does not live long enough
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// the problem here is that the full type of `m` is
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//
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// Box<Trait<'m>+'static>
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//
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// Here `'m` must be exactly the lifetime of the variable `m`.
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// This is because of two requirements:
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// 1. First, the basic type rules require that the
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// type of `m`'s value outlives the lifetime of `m`. This puts a lower
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// bound `'m`.
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//
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// 2. Meanwhile, the signature of `object_invoke1` requires that
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// we create a reference of type `&'d Trait<'d>` for some `'d`.
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// `'d` cannot outlive `'m`, so that forces the lifetime to be `'m`.
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//
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// This then conflicts with the dropck rules, which require that
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// the type of `m` *strictly outlives* `'m`. Hence we get an
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// error.
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}
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