c2e8264b34
don't apply temporary lifetime extension rules to non-extended `super let` Reference PR: rust-lang/reference#1980 This changes the semantics for `super let` (and macros implemented in terms of it, such as `pin!`, `format_args!`, `write!`, and `println!`) as suggested by ````@theemathas```` in https://github.com/rust-lang/rust/issues/145784#issuecomment-3218658335, making `super let` initializers only count as [extending expressions](https://doc.rust-lang.org/nightly/reference/destructors.html#extending-based-on-expressions) when the `super let` itself is within an extending block. Since `super let` initializers aren't temporary drop scopes, their temporaries outside of inner temporary scopes are effectively always extended, even when not in extending positions; this only affects two cases as far as I can tell: - Block tail expressions in Rust 2024. This PR makes `f(pin!({ &temp() }))` drop `temp()` at the end of the block in Rust 2024, whereas previously it would live until after the call to `f` because syntactically the `temp()` was in an extending position as a result of `super let` in `pin!`'s expansion. - `super let` nested within a non-extended `super let` is no longer extended. i.e. a normal `let` is required to treat `super let`s as extending (in which case nested `super let`s will also be extending). Closes rust-lang/rust#145784 This is a breaking change. Both static and dynamic semantics are affected. The most likely breakage is for programs to stop compiling, but it's technically possible for drop order to silently change as well (as in rust-lang/rust#145784). Since this affects stable macros, it probably would need a crater run. Nominating for discussion alongside rust-lang/rust#145784: ````@rustbot```` label +I-lang-nominated +I-libs-api-nominated Tracking issue for `super let`: rust-lang/rust#139076
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Why Rust?
-
Performance: Fast and memory-efficient, suitable for critical services, embedded devices, and easily integrated with other languages.
-
Reliability: Our rich type system and ownership model ensure memory and thread safety, reducing bugs at compile-time.
-
Productivity: Comprehensive documentation, a compiler committed to providing great diagnostics, and advanced tooling including package manager and build tool (Cargo), auto-formatter (rustfmt), linter (Clippy) and editor support (rust-analyzer).
Quick Start
Read "Installation" from The Book.
Installing from Source
If you really want to install from source (though this is not recommended), see INSTALL.md.
Getting Help
See https://www.rust-lang.org/community for a list of chat platforms and forums.
Contributing
See CONTRIBUTING.md.
License
Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.
See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.
Trademark
The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the "Rust Trademarks").
If you want to use these names or brands, please read the Rust language trademark policy.
Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.