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]
123 lines
2.5 KiB
Rust
123 lines
2.5 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 how overloaded deref interacts with borrows when only
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// Deref and not DerefMut is implemented.
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use std::ops::Deref;
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struct Rc<T> {
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value: *const T
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}
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impl<T> Deref<T> for Rc<T> {
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fn deref(&self) -> &T {
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unsafe { &*self.value }
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}
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}
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struct Point {
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x: int,
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y: int
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}
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impl Point {
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fn get(&self) -> (int, int) {
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(self.x, self.y)
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}
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fn set(&mut self, x: int, y: int) {
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self.x = x;
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self.y = y;
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}
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fn x_ref(&self) -> &int {
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&self.x
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}
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fn y_mut(&mut self) -> &mut int {
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&mut self.y
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}
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}
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fn deref_imm_field(x: Rc<Point>) {
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let _i = &x.y;
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}
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fn deref_mut_field1(x: Rc<Point>) {
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let _i = &mut x.y; //~ ERROR cannot borrow
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}
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fn deref_mut_field2(mut x: Rc<Point>) {
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let _i = &mut x.y; //~ ERROR cannot borrow
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}
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fn deref_extend_field(x: &Rc<Point>) -> &int {
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&x.y
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}
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fn deref_extend_mut_field1(x: &Rc<Point>) -> &mut int {
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&mut x.y //~ ERROR cannot borrow
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}
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fn deref_extend_mut_field2(x: &mut Rc<Point>) -> &mut int {
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&mut x.y //~ ERROR cannot borrow
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}
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fn assign_field1<'a>(x: Rc<Point>) {
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x.y = 3; //~ ERROR cannot assign
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}
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fn assign_field2<'a>(x: &'a Rc<Point>) {
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x.y = 3; //~ ERROR cannot assign
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}
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fn assign_field3<'a>(x: &'a mut Rc<Point>) {
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x.y = 3; //~ ERROR cannot assign
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}
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fn deref_imm_method(x: Rc<Point>) {
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let _i = x.get();
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}
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fn deref_mut_method1(x: Rc<Point>) {
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x.set(0, 0); //~ ERROR cannot borrow
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}
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fn deref_mut_method2(mut x: Rc<Point>) {
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x.set(0, 0); //~ ERROR cannot borrow
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}
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fn deref_extend_method(x: &Rc<Point>) -> &int {
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x.x_ref()
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}
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fn deref_extend_mut_method1(x: &Rc<Point>) -> &mut int {
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x.y_mut() //~ ERROR cannot borrow
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}
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fn deref_extend_mut_method2(x: &mut Rc<Point>) -> &mut int {
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x.y_mut() //~ ERROR cannot borrow
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}
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fn assign_method1<'a>(x: Rc<Point>) {
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*x.y_mut() = 3; //~ ERROR cannot borrow
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}
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fn assign_method2<'a>(x: &'a Rc<Point>) {
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*x.y_mut() = 3; //~ ERROR cannot borrow
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}
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fn assign_method3<'a>(x: &'a mut Rc<Point>) {
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*x.y_mut() = 3; //~ ERROR cannot borrow
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}
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pub fn main() {}
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