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#[may_dangle] compiles on non-Drop impls #68411

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Ixrec opened this issue Jan 21, 2020 · 4 comments
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#[may_dangle] compiles on non-Drop impls #68411

Ixrec opened this issue Jan 21, 2020 · 4 comments
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@kei519
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A-attributes Area: Attributes (`#[…]`, `#![…]`) C-bug Category: This is a bug. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. F-dropck_eyepatch `#![feature(dropck_eyepatch)]` requires-nightly This issue requires a nightly compiler in some way. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@Ixrec
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Ixrec commented Jan 21, 2020 •
edited by rustbot
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The RFC pretty strongly implies that this attribute is only supposed to be used on Drop, and the semantics of it don't make any sense on other traits. Yet, this compiles:

#![feature(dropck_eyepatch)]

struct Foo<T>(T);

unsafe impl<#[may_dangle] T> std::ops::Deref for Foo<T> {
    type Target = T;
    fn deref(&self) -> &T {
        &self.0
    }
}

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@jonas-schievink jonas-schievink added A-attributes Area: Attributes (`#[…]`, `#![…]`) C-bug Category: This is a bug. requires-nightly This issue requires a nightly compiler in some way. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. F-dropck_eyepatch `#![feature(dropck_eyepatch)]` labels Jan 21, 2020
@oli-obk
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oli-obk commented Aug 1, 2024

see also https://github.com/rust-lang/rust/pull/128444/files for how the attribute just works on anything like functions, imports, ...

@oli-obk oli-obk added the E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. label Aug 1, 2024
@kei519
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kei519 commented Aug 14, 2024

@rustbot claim

@kei519
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kei519 commented Sep 9, 2024 •
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This seems to be fixed with 3a9bf4551374893fdc522572ee569028186e22cc.

@jieyouxu
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Fixed by #129235

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@kei519 kei519

Labels
A-attributes Area: Attributes (`#[…]`, `#![…]`) C-bug Category: This is a bug. E-easy Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue. F-dropck_eyepatch `#![feature(dropck_eyepatch)]` requires-nightly This issue requires a nightly compiler in some way. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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@oli-obk @jonas-schievink @Ixrec @jieyouxu @kei519