Make iter::Empty<T> Send and Sync for any T #68348
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
(rust_highfive has picked a reviewer for you, use r? to override) |
rust-highfive
added
the
S-waiting-on-review
Centril
added
T-libs-api
|
r? @dtolnay |
|
@bors r+ This makes perfect sense and has no future compat concerns, so an obvious r+. FWIW this PR could also be extended to other auto-traits such as |
|
📌 Commit d7a18f8 has been approved by |
bors
added
S-waiting-on-bors
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this pull request
Jan 19, 2020
Make iter::Empty<T> Send and Sync for any T Continuing from rust-lang#57682 It's quite funny, when I initially submitted this pull request, I said "Likely nobody will be using that property of `iter::empty`", but then a year later I got a compilation error because it wasn't `Send` and `Sync`. Unfortunately, `PhantomData<fn() -> T>` still errors out. Oh well. I proposed ` struct PhantomFnWorkaround<T>(fn() -> T);`, but dtolnay did not like it, so using explicit implementations.
bors
added a commit
that referenced
this pull request
Jan 19, 2020
Rollup of 5 pull requests Successful merges: - #67682 ([const-prop] Remove useless typedef) - #68133 (Slimmer syntax) - #68154 (Add more BTreeMap/BTreeSet benchmarks regarding iteration) - #68247 (Clean up err codes) - #68348 (Make iter::Empty<T> Send and Sync for any T) Failed merges: - #68353 (Remove `rustc_error_codes` deps except in `rustc_driver`) r? @ghost
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this pull request
Jan 19, 2020
Make iter::Empty<T> Send and Sync for any T Continuing from rust-lang#57682 It's quite funny, when I initially submitted this pull request, I said "Likely nobody will be using that property of `iter::empty`", but then a year later I got a compilation error because it wasn't `Send` and `Sync`. Unfortunately, `PhantomData<fn() -> T>` still errors out. Oh well. I proposed ` struct PhantomFnWorkaround<T>(fn() -> T);`, but dtolnay did not like it, so using explicit implementations.
netbsd-srcmastr
pushed a commit
to NetBSD/pkgsrc
that referenced
this pull request
Mar 13, 2020
Version 1.42.0 (2020-03-12)
==========================
Language
--------
- [You can now use the slice pattern syntax with subslices.][67712] e.g.
```rust
fn foo(words: &[&str]) {
match words {
["Hello", "World", "!", ..] => println!("Hello World!"),
["Foo", "Bar", ..] => println!("Baz"),
rest => println!("{:?}", rest),
}
}
```
- [You can now use `#[repr(transparent)]` on univariant `enum`s.][68122] Meaning
that you can create an enum that has the exact layout and ABI of the type
it contains.
- [There are some *syntax-only* changes:][67131]
- `default` is syntactically allowed before items in `trait` definitions.
- Items in `impl`s (i.e. `const`s, `type`s, and `fn`s) may syntactically
leave out their bodies in favor of `;`.
- Bounds on associated types in `impl`s are now syntactically allowed
(e.g. `type Foo: Ord;`).
- `...` (the C-variadic type) may occur syntactically directly as the type of
any function parameter.
These are still rejected *semantically*, so you will likely receive an error
but these changes can be seen and parsed by procedural macros and
conditional compilation.
Compiler
--------
- [Added tier 2* support for `armv7a-none-eabi`.][68253]
- [Added tier 2 support for `riscv64gc-unknown-linux-gnu`.][68339]
- [`Option::{expect,unwrap}` and
`Result::{expect, expect_err, unwrap, unwrap_err}` now produce panic messages
pointing to the location where they were called, rather than
`core`'s internals. ][67887]
* Refer to Rust's [platform support page][forge-platform-support] for more
information on Rust's tiered platform support.
Libraries
---------
- [`iter::Empty<T>` now implements `Send` and `Sync` for any `T`.][68348]
- [`Pin::{map_unchecked, map_unchecked_mut}` no longer require the return type
to implement `Sized`.][67935]
- [`io::Cursor` now derives `PartialEq` and `Eq`.][67233]
- [`Layout::new` is now `const`.][66254]
- [Added Standard Library support for `riscv64gc-unknown-linux-gnu`.][66899]
Stabilized APIs
---------------
- [`CondVar::wait_while`]
- [`CondVar::wait_timeout_while`]
- [`DebugMap::key`]
- [`DebugMap::value`]
- [`ManuallyDrop::take`]
- [`matches!`]
- [`ptr::slice_from_raw_parts_mut`]
- [`ptr::slice_from_raw_parts`]
Cargo
-----
- [You no longer need to include `extern crate proc_macro;` to be able to
`use proc_macro;` in the `2018` edition.][cargo/7700]
Compatibility Notes
-------------------
- [`Error::description` has been deprecated, and its use will now produce a
warning.][66919] It's recommended to use `Display`/`to_string` instead.
- [`use $crate;` inside macros is now a hard error.][37390] The compiler
emitted forward compatibility warnings since Rust 1.14.0.
- [As previously announced, this release reduces the level of support for
32-bit Apple targets to tier 3.][apple-32bit-drop]. This means that the
source code is still available to build, but the targets are no longer tested
and no release binary is distributed by the Rust project. Please refer to the
linked blog post for more information.
[37390]: rust-lang/rust#37390
[68253]: rust-lang/rust#68253
[68348]: rust-lang/rust#68348
[67935]: rust-lang/rust#67935
[68339]: rust-lang/rust#68339
[68122]: rust-lang/rust#68122
[67712]: rust-lang/rust#67712
[67887]: rust-lang/rust#67887
[67131]: rust-lang/rust#67131
[67233]: rust-lang/rust#67233
[66899]: rust-lang/rust#66899
[66919]: rust-lang/rust#66919
[66254]: rust-lang/rust#66254
[cargo/7700]: rust-lang/cargo#7700
[`DebugMap::key`]: https://doc.rust-lang.org/stable/std/fmt/struct.DebugMap.html#method.key
[`DebugMap::value`]: https://doc.rust-lang.org/stable/std/fmt/struct.DebugMap.html#method.value
[`ManuallyDrop::take`]: https://doc.rust-lang.org/stable/std/mem/struct.ManuallyDrop.html#method.take
[`matches!`]: https://doc.rust-lang.org/stable/std/macro.matches.html
[`ptr::slice_from_raw_parts_mut`]: https://doc.rust-lang.org/stable/std/ptr/fn.slice_from_raw_parts_mut.html
[`ptr::slice_from_raw_parts`]: https://doc.rust-lang.org/stable/std/ptr/fn.slice_from_raw_parts.html
[`CondVar::wait_while`]: https://doc.rust-lang.org/stable/std/sync/struct.Condvar.html#method.wait_while
[`CondVar::wait_timeout_while`]: https://doc.rust-lang.org/stable/std/sync/struct.Condvar.html#method.wait_timeout_while
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
7 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Continuing from #57682
It's quite funny, when I initially submitted this pull request, I said "Likely nobody will be using that property of
iter::empty", but then a year later I got a compilation error because it wasn'tSendandSync.Unfortunately,
PhantomData<fn() -> T>still errors out. Oh well. I proposedstruct PhantomFnWorkaround<T>(fn() -> T);, but dtolnay did not like it, so using explicit implementations.