dropck: Remove Copy from special-cased traits
#24906
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[breaking-change]
What does this break? Basically, code that implements `Drop` and is
using `T:Copy` for one of its type parameters and is relying on the
Drop Check rule not applying to it.
Here is an example:
```rust
#![allow(dead_code,unused_variables,unused_assignments)]
struct D<T:Copy>(T);
impl<T:Copy> Drop for D<T> { fn drop(&mut self) { } }
trait UserT { fn c(&self) { } }
impl<T:Copy> UserT for T { }
struct E<T:UserT>(T);
impl<T:UserT> Drop for E<T> { fn drop(&mut self) { } }
// This one will start breaking.
fn foo() { let (d2, d1); d1 = D(34); d2 = D(&d1); }
#[cfg(this_one_does_and_should_always_break)]
fn bar() { let (e2, e1); e1 = E(34); e2 = E(&e1); }
fn main() {
foo();
}
```
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alexcrichton
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Apr 28, 2015
dropck: Remove `Copy` from special-cased traits Fix #24895. [breaking-change] What does this break? Basically, code that implements `Drop` and is using `T:Copy` for one of its type parameters and is relying on the Drop Check rule not applying to it. Here is an example: ```rust #![allow(dead_code,unused_variables,unused_assignments)] struct D<T:Copy>(T); impl<T:Copy> Drop for D<T> { fn drop(&mut self) { } } trait UserT { fn c(&self) { } } impl<T:Copy> UserT for T { } struct E<T:UserT>(T); impl<T:UserT> Drop for E<T> { fn drop(&mut self) { } } // This one will start breaking. fn foo() { let (d2, d1); d1 = D(34); d2 = D(&d1); } #[cfg(this_one_does_and_should_always_break)] fn bar() { let (e2, e1); e1 = E(34); e2 = E(&e1); } fn main() { foo(); } ```
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Backported. |
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dropck: Remove
Copyfrom special-cased traitsFix #24895.
[breaking-change]
What does this break? Basically, code that implements
Dropand isusing
T:Copyfor one of its type parameters and is relying on theDrop Check rule not applying to it.
Here is an example: