Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit57cea32

Browse files
authored
Rollup merge ofrust-lang#120248 - WaffleLapkin:bonk-ptr-object-casts, r=compiler-errors,oli-obk,lnicola
Make casts of pointers to trait objects stricterThis is an attempt to `fix`rust-lang#120222 andrust-lang#120217.This is done by adding restrictions on casting pointers to trait objects.Before this PR the rules were as follows:> When casting `*const X<dyn A>` -> `*const Y<dyn B>`, principal traits in `A` and `B` must refer to the same trait definition (or no trait).With this PR the rules are changed to> When casting `*const X<dyn Src>` -> `*const Y<dyn Dst>`> - if `Dst` has a principal trait `DstP`,> - `Src` must have a principal trait `SrcP`> - `dyn SrcP` and `dyn DstP` must be the same type (modulo the trait object lifetime, `dyn T+'a` -> `dyn T+'b` is allowed)> - Auto traits in `Dst` must be a subset of auto traits in `Src`> - Not adhering to this is currently a FCW (warn-by-default + `FutureReleaseErrorReportInDeps`), instead of an error> - if `Src` has a principal trait `Dst` must as well> - this restriction will be removed in a follow up PRThis ensures that1. Principal trait's generic arguments match (no `*const dyn Tr<A>` -> `*const dyn Tr<B>` casts, which are a problem for [rust-lang#120222](rust-lang#120222))2. Principal trait's lifetime arguments match (no `*const dyn Tr<'a>` -> `*const dyn Tr<'b>` casts, which are a problem for [rust-lang#120217](rust-lang#120217))3. No auto traits can be _added_ (this is a problem for arbitrary self types, see [this comment](rust-lang#120248 (comment)))Some notes: - We only care about the metadata/last field, so you can still cast `*const dyn T` to `*const WithHeader<dyn T>`, etc- The lifetime of the trait object itself (`dyn A + 'lt`) is not checked, so you can still cast `*mut FnOnce() + '_` to `*mut FnOnce() + 'static`, etc - This feels fishy, but I couldn't come up with a reason it must be checkedThe diagnostics are currently not great, to say the least, but as far as I can tell this correctly fixes the issues.cc `@oli-obk` `@compiler-errors` `@lcnr`
2 parentse466bf5 +297850a commit57cea32

File tree

1 file changed

+3
-3
lines changed

1 file changed

+3
-3
lines changed

‎alloc/src/boxed.rs‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2374,7 +2374,7 @@ impl dyn Error + Send {
23742374
let err:Box<dynError> =self;
23752375
<dynError>::downcast(err).map_err(|s|unsafe{
23762376
// Reapply the `Send` marker.
2377-
Box::from_raw(Box::into_raw(s)as*mut(dynError +Send))
2377+
mem::transmute::<Box<dynError>,Box<dynError +Send>>(s)
23782378
})
23792379
}
23802380
}
@@ -2387,8 +2387,8 @@ impl dyn Error + Send + Sync {
23872387
pubfndowncast<T:Error +'static>(self:Box<Self>) ->Result<Box<T>,Box<Self>>{
23882388
let err:Box<dynError> =self;
23892389
<dynError>::downcast(err).map_err(|s|unsafe{
2390-
// Reapply the `Send + Sync`marker.
2391-
Box::from_raw(Box::into_raw(s)as*mut(dynError +Send +Sync))
2390+
// Reapply the `Send + Sync`markers.
2391+
mem::transmute::<Box<dynError>,Box<dynError +Send +Sync>>(s)
23922392
})
23932393
}
23942394
}

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp