096a28607f
This change makes the compiler no longer infer whether types (structures
and enumerations) implement the `Copy` trait (and thus are implicitly
copyable). Rather, you must implement `Copy` yourself via `impl Copy for
MyType {}`.
A new warning has been added, `missing_copy_implementations`, to warn
you if a non-generic public type has been added that could have
implemented `Copy` but didn't.
For convenience, you may *temporarily* opt out of this behavior by using
`#![feature(opt_out_copy)]`. Note though that this feature gate will never be
accepted and will be removed by the time that 1.0 is released, so you should
transition your code away from using it.
This breaks code like:
#[deriving(Show)]
struct Point2D {
x: int,
y: int,
}
fn main() {
let mypoint = Point2D {
x: 1,
y: 1,
};
let otherpoint = mypoint;
println!("{}{}", mypoint, otherpoint);
}
Change this code to:
#[deriving(Show)]
struct Point2D {
x: int,
y: int,
}
impl Copy for Point2D {}
fn main() {
let mypoint = Point2D {
x: 1,
y: 1,
};
let otherpoint = mypoint;
println!("{}{}", mypoint, otherpoint);
}
This is the backwards-incompatible part of #13231.
Part of RFC #3.
[breaking-change]
76 lines
1.9 KiB
Rust
76 lines
1.9 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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use std::rc::Rc;
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struct DerefWrapper<X, Y> {
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x: X,
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y: Y
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}
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impl<X:Copy,Y:Copy> Copy for DerefWrapper<X,Y> {}
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impl<X, Y> DerefWrapper<X, Y> {
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fn get_x(self) -> X {
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self.x
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}
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}
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impl<X, Y> Deref<Y> for DerefWrapper<X, Y> {
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fn deref(&self) -> &Y {
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&self.y
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}
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}
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mod priv_test {
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pub struct DerefWrapperHideX<X, Y> {
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x: X,
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pub y: Y
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}
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impl<X:Copy,Y:Copy> Copy for DerefWrapperHideX<X,Y> {}
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impl<X, Y> DerefWrapperHideX<X, Y> {
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pub fn new(x: X, y: Y) -> DerefWrapperHideX<X, Y> {
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DerefWrapperHideX {
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x: x,
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y: y
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}
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}
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}
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impl<X, Y> Deref<Y> for DerefWrapperHideX<X, Y> {
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fn deref(&self) -> &Y {
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&self.y
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}
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}
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}
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pub fn main() {
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let nested = DerefWrapper {x: true, y: DerefWrapper {x: 0i, y: 1i}};
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// Use the first field that you can find.
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assert_eq!(nested.x, true);
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assert_eq!((*nested).x, 0);
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// Same for methods, even though there are multiple
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// candidates (at different nesting levels).
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assert_eq!(nested.get_x(), true);
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assert_eq!((*nested).get_x(), 0);
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// Also go through multiple levels of indirection.
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assert_eq!(Rc::new(nested).x, true);
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let nested_priv = priv_test::DerefWrapperHideX::new(true, DerefWrapper {x: 0i, y: 1i});
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// FIXME(eddyb) #12808 should skip private fields.
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// assert_eq!(nested_priv.x, 0);
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assert_eq!((*nested_priv).x, 0);
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}
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