6f99a27886
This implements RFC 39. Omitted lifetimes in return values will now be
inferred to more useful defaults, and an error is reported if a lifetime
in a return type is omitted and one of the two lifetime elision rules
does not specify what it should be.
This primarily breaks two uncommon code patterns. The first is this:
unsafe fn get_foo_out_of_thin_air() -> &Foo {
...
}
This should be changed to:
unsafe fn get_foo_out_of_thin_air() -> &'static Foo {
...
}
The second pattern that needs to be changed is this:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed {
Owned(format!("hello world"))
}
Change code like this to:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed<'static> {
Owned(format!("hello world"))
}
Closes #15552.
[breaking-change]
45 lines
1.4 KiB
Rust
45 lines
1.4 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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// Test that the borrow checker prevents pointers to temporaries
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// with statement lifetimes from escaping.
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#![feature(macro_rules)]
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use std::ops::Drop;
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static mut FLAGS: u64 = 0;
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struct Box<T> { f: T }
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struct AddFlags { bits: u64 }
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fn AddFlags(bits: u64) -> AddFlags {
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AddFlags { bits: bits }
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}
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fn arg(x: &AddFlags) -> &AddFlags {
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x
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}
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impl AddFlags {
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fn get(&self) -> &AddFlags {
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self
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}
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}
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pub fn main() {
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let _x = arg(&AddFlags(1)); //~ ERROR value does not live long enough
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let _x = AddFlags(1).get(); //~ ERROR value does not live long enough
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let _x = &*arg(&AddFlags(1)); //~ ERROR value does not live long enough
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let ref _x = *arg(&AddFlags(1)); //~ ERROR value does not live long enough
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let &ref _x = arg(&AddFlags(1)); //~ ERROR value does not live long enough
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let _x = AddFlags(1).get(); //~ ERROR value does not live long enough
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let Box { f: _x } = Box { f: AddFlags(1).get() }; //~ ERROR value does not live long enough
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}
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