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Matthias Krüger 6352044269
Rollup merge of #137399 - lukas-code:oopsie-woopsie, r=compiler-errors 
fix ICE in layout computation with unnormalizable const

The first commit reverts half of 7a667d206c, where I removed a case from `layout_of` for handling non-generic unevaluated consts in array length, that I incorrectly assumed to be unreachable. This can actually happen with the combination of `feature(generic_const_exprs)` and `feature(trivial_bounds)`, because GCE makes anon consts inherit their parent's predicates and with an impossible predicate like `u8: A` it's possible to have an array whose length is an associated const like `<u8 as A>::B` that is not generic, but also can't be normalized:

```rust
#![feature(generic_const_exprs)]
#![feature(trivial_bounds)]

trait A {
    const B: usize;
}

// With GCE + trivial bounds this definition is not a compile error.
// Computing the layout of this type shouldn't ICE.
struct S([u8; <u8 as A>::B])
where
    u8: A;
```

---

The first commit also incidentally fixes https://github.com/rust-lang/rust/issues/137308, which also managed to get an unnormalizable assoc const into an array length:

```rust
trait A {
    const B: usize;
}

impl<C: ?Sized> A for u8 { //~ ERROR: the type parameter `C` is not constrained
    const B: usize = 42;
}

// Computing the layout of this type shouldn't ICE, even with the compile error above.
struct S([u8; <u8 as A>::B]);
```

This happens, because we bail out from `codegen_select_candidate` with an error if the selected impl has unconstrained params to avoid leaking infer vars out of a query. `Instance::try_resolve` will then return `Ok(None)`, which for assoc consts roughly means "this const can't be evaluated in a generic context" and is treated as such: 71e06b9c59/compiler/rustc_middle/src/mir/interpret/queries.rs (L84) (and this can ICE if the const isn't generic: https://github.com/rust-lang/rust/issues/135617).

However, here `<u8 as A>::B` is definitely not "too generic" and also not unresolvable due to an unsatisfiable `u8: A` bound, so I've included the second commit to change the result of `Instance::try_resolve` from `Ok(None)` to `Err(ErrorGuaranteed)` when resolving an assoc item to an impl with unconstrained generic params. This has the effect that `<u8 as A>::B` will now be normalized to `ConstKind::Error` in the example above.

This properly fixes https://github.com/rust-lang/rust/issues/137308, by no longer treating `<u8 as A>::B` as unresolvable even though it clearly has a unique impl that it resolves to. It also has the effect of changing the layout error from `Unknown` ("the type may be valid but has no sensible layout") to `ReferencesError` ("a non-layout error is reported elsewhere") which seems more appropriate.

r? ```@compiler-errors```
2025-02-22 01:01:42 +01:00
.github Auto merge of #137023 - Kobzol:bump-sccache, r=marcoieni 2025-02-20 05:59:04 +00:00
compiler Rollup merge of #137399 - lukas-code:oopsie-woopsie, r=compiler-errors 2025-02-22 01:01:42 +01:00
library Rollup merge of #137207 - petertodd:2025-add-track-caller-to-duration-div, r=jhpratt 2025-02-22 01:01:40 +01:00
LICENSES Synchronize Unicode license text from unicode.org 2024-11-20 00:54:12 -08:00
src Rollup merge of #136474 - jieyouxu:src-base, r=clubby789 2025-02-22 01:01:38 +01:00
tests Rollup merge of #137399 - lukas-code:oopsie-woopsie, r=compiler-errors 2025-02-22 01:01:42 +01:00
.clang-format Add .clang-format 2024-06-26 05:56:00 +08:00
.editorconfig Don't apply editorconfig to llvm 2025-02-09 16:21:14 -05:00
.git-blame-ignore-revs Git blame ignore recent formatting commit 2025-02-09 12:00:23 -08:00
.gitattributes Revert "Stop git from merging generated files" 2024-12-12 07:20:11 +01:00
.gitignore ignore vendor directory in git status 2025-02-12 21:16:36 -05:00
.gitmodules Update to LLVM 20 2025-02-14 11:02:28 +01:00
.ignore Add .ignore file to make config.toml searchable in vscode 2024-06-24 10:15:16 +02:00
.mailmap Rollup merge of #134965 - Noratrieb:slightly-late-for-boxing-day-sadly-but-still-almost, r=BoxyUwU 2025-01-03 22:12:42 +01:00
Cargo.lock Stacker now handles miri using a noop impl itself 2025-02-21 13:54:45 +00:00
Cargo.toml Move error_index_generator to the rustbook workspace 2025-02-17 10:58:15 -08:00
CODE_OF_CONDUCT.md Remove the code of conduct; instead link https://www.rust-lang.org/conduct.html 2019-10-05 22:55:19 +02:00
config.example.toml Update references to cc_detect.rs 2025-02-20 10:41:29 +00:00
configure Ensure ./configure works when configure.py path contains spaces 2024-02-16 18:57:22 +00:00
CONTRIBUTING.md docs: update contributing docs for submodule/subtree changes 2025-01-20 21:53:59 +08:00
COPYRIGHT dist: Re-work how we describe the licence of Rust in our distributions 2024-12-09 10:18:55 +00:00
INSTALL.md add clarity for custom path installation 2024-10-06 07:37:00 -05:00
LICENSE-APACHE Remove appendix from LICENCE-APACHE 2019-12-30 14:25:53 +00:00
license-metadata.json Add italic for newly added sans serif fonts 2025-01-29 11:01:14 +01:00
LICENSE-MIT dist: Re-work how we describe the licence of Rust in our distributions 2024-12-09 10:18:55 +00:00
README.md Grammar fixes 2024-12-09 17:17:27 -05:00
RELEASES.md Re-add missing empty lines in the releases notes 2025-02-16 12:15:55 +01:00
REUSE.toml Fix tidy errors 2025-01-29 11:01:14 +01:00
rust-bors.toml Increase timeout for new bors bot 2024-03-13 08:31:07 +01:00
rustfmt.toml Update rustfmt.toml to match the rust repo 2025-02-13 14:54:50 +00:00
triagebot.toml Rollup merge of #137076 - aDotInTheVoid:pingme-pingme-pingme, r=jieyouxu 2025-02-15 20:15:03 +01:00
x fix(x): fix a regex used to find python executable 2024-11-06 16:40:02 +03:00
x.ps1 use & instead of start-process in x.ps1 2023-12-09 09:46:16 -05:00
x.py Reformat Python code with ruff 2024-12-04 23:03:44 +01:00

README.md

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 media guide.

Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.