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Diffstat (limited to 'src/test/ui/span/dropck-object-cycle.rs')
| -rw-r--r-- | src/test/ui/span/dropck-object-cycle.rs | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/src/test/ui/span/dropck-object-cycle.rs b/src/test/ui/span/dropck-object-cycle.rs new file mode 100644 index 00000000000..ce9bc17432e --- /dev/null +++ b/src/test/ui/span/dropck-object-cycle.rs @@ -0,0 +1,61 @@ +// 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 test used to be part of a run-pass test, but revised outlives +// rule means that it no longer compiles. + +#![allow(unused_variables)] + +trait Trait<'a> { + fn long(&'a self) -> isize; + fn short<'b>(&'b self) -> isize; +} + +fn object_invoke1<'d>(x: &'d Trait<'d>) -> (isize, isize) { loop { } } + +trait MakerTrait { + fn mk() -> Self; +} + +fn make_val<T:MakerTrait>() -> T { + MakerTrait::mk() +} + +impl<'t> MakerTrait for Box<Trait<'t>+'static> { + fn mk() -> Box<Trait<'t>+'static> { loop { } } +} + +pub fn main() { + let m : Box<Trait+'static> = make_val(); + assert_eq!(object_invoke1(&*m), (4,5)); + //~^ NOTE borrow occurs here + + // the problem here is that the full type of `m` is + // + // Box<Trait<'m>+'static> + // + // Here `'m` must be exactly the lifetime of the variable `m`. + // This is because of two requirements: + // 1. First, the basic type rules require that the + // type of `m`'s value outlives the lifetime of `m`. This puts a lower + // bound `'m`. + // + // 2. Meanwhile, the signature of `object_invoke1` requires that + // we create a reference of type `&'d Trait<'d>` for some `'d`. + // `'d` cannot outlive `'m`, so that forces the lifetime to be `'m`. + // + // This then conflicts with the dropck rules, which require that + // the type of `m` *strictly outlives* `'m`. Hence we get an + // error. +} +//~^ ERROR `*m` does not live long enough +//~| NOTE `*m` dropped here while still borrowed +//~| NOTE values in a scope are dropped in the opposite order they are created + |
