05e3248a79
This can break code that looked like:
impl Foo for Box<Any> {
fn f(&self) { ... }
}
let x: Box<Any + Send> = ...;
x.f();
Change such code to:
impl Foo for Box<Any> {
fn f(&self) { ... }
}
let x: Box<Any> = ...;
x.f();
That is, upcast before calling methods.
This is a conservative solution to #5781. A more proper treatment (see
the xfail'd `trait-contravariant-self.rs`) would take variance into
account. This change fixes the soundness hole.
Some library changes had to be made to make this work. In particular,
`Box<Any>` is no longer showable, and only `Box<Any+Send>` is showable.
Eventually, this restriction can be lifted; for now, it does not prove
too onerous, because `Any` is only used for propagating the result of
task failure.
This patch also adds a test for the variance inference work in #12828,
which accidentally landed as part of DST.
Closes #5781.
[breaking-change]
31 lines
864 B
Rust
31 lines
864 B
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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// Issue #5781. Tests that subtyping is handled properly in trait matching.
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trait Make<'a> {
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fn make(x: &'a mut int) -> Self;
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}
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impl<'a> Make<'a> for &'a mut int {
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fn make(x: &'a mut int) -> &'a mut int {
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x
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}
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}
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fn f() -> &'static mut int {
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let mut x = 1;
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let y: &'static mut int = Make::make(&mut x); //~ ERROR `x` does not live long enough
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y
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}
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fn main() {}
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