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]
51 lines
1.2 KiB
Rust
51 lines
1.2 KiB
Rust
// Copyright 2012-2013 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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// Tests that the scope of the pointer returned from `get()` is
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// limited to the deref operation itself, and does not infect the
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// block as a whole.
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struct Box {
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x: uint
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}
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impl Box {
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fn get(&self) -> &uint {
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&self.x
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}
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fn set(&mut self, x: uint) {
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self.x = x;
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}
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}
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fn fun1() {
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// in the past, borrow checker behaved differently when
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// init and decl of `v` were distinct
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let v;
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let mut a_box = Box {x: 0};
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a_box.set(22);
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v = *a_box.get();
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a_box.set(v+1);
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assert_eq!(23, *a_box.get());
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}
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fn fun2() {
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let mut a_box = Box {x: 0};
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a_box.set(22);
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let v = *a_box.get();
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a_box.set(v+1);
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assert_eq!(23, *a_box.get());
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}
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pub fn main() {
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fun1();
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fun2();
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}
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