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Matthias Krüger 67278cd9f4
Rollup merge of #133392 - compiler-errors:object-sup, r=lcnr 
Fix ICE when multiple supertrait substitutions need assoc but only one is provided

Dyn traits must have all of their associated types constrained either by:
1. writing them in the dyn trait itself as an associated type bound, like `dyn Iterator<Item = u32>`,
2. A supertrait bound, like `trait ConstrainedIterator: Iterator<Item = u32> {}`, then you may write `dyn ConstrainedIterator` which doesn't need to mention `Item`.

However, the object type lowering code did not consider the fact that there may be multiple supertraits with different substitutions, so it just used the associated type's *def id* as a key for keeping track of which associated types are missing:

1fc691e6dd/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs (L131)

This means that we can have missing associated types when there are mutliple supertraits with different substitutions and only one of them is constrained, like:

```rust
trait Sup<T> {
    type Assoc: Default;
}

impl<T: Default> Sup<T> for () {
    type Assoc = T;
}
impl<T: Default, U: Default> Dyn<T, U> for () {}

trait Dyn<A, B>: Sup<A, Assoc = A> + Sup<B> {}
```

The above example allows you to name `<dyn Dyn<i32, u32> as Sup<u32>>::Assoc` even though it is not possible to project since it's neither constrained by a manually written projection bound or a supertrait bound. This successfully type-checks, but leads to a codegen ICE since we are not able to project the associated type.

This PR fixes the validation for checking that a dyn trait mentions all of its associated type bounds. This is theoretically a breaking change, since you could technically use that `dyn Dyn<A, B>` type mentionedin the example above without actually *projecting* to the bad associated type, but I don't expect it to ever be relevant to a user since it's almost certainly a bug. This is corroborated with the crater results[^crater], which show no failures[^unknown].

Crater: https://github.com/rust-lang/rust/pull/133392#issuecomment-2508769703

Fixes #133388

[^crater]: I cratered this originally with #133397, which is a PR that is stacked on top, then re-ran crater with just the failures from that PR.
[^unknown]: If you look at the crater results, it shows all of the passes as "unknown". I believe this is a crater bug, since looking at the results manually shows them as passes.
2024-12-14 23:56:30 +01:00
.github Configure renovatebot 2024-12-09 12:07:11 +01:00
compiler Rollup merge of #133392 - compiler-errors:object-sup, r=lcnr 2024-12-14 23:56:30 +01:00
library Auto merge of #134296 - matthiaskrgr:rollup-o0sxozj, r=matthiaskrgr 2024-12-14 13:06:18 +00:00
LICENSES Synchronize Unicode license text from unicode.org 2024-11-20 00:54:12 -08:00
src Rollup merge of #133293 - psumbera:solaris-maintainer, r=workingjubilee,jieyouxu,tgross35 2024-12-14 23:56:29 +01:00
tests Rollup merge of #133392 - compiler-errors:object-sup, r=lcnr 2024-12-14 23:56:30 +01:00
.clang-format Add .clang-format 2024-06-26 05:56:00 +08:00
.editorconfig Only use max_line_length = 100 for *.rs 2023-07-10 15:18:36 -07:00
.git-blame-ignore-revs Add rustfmt 2024 reformatting to git blame ignore 2024-09-23 10:02:04 +02:00
.gitattributes Revert "Stop git from merging generated files" 2024-12-12 07:20:11 +01:00
.gitignore only ignore {flake,default}.nix and {.envrc,.direnv/} in the root 2024-12-10 00:08:26 +01:00
.gitmodules Update LLVM to 19.1.5 2024-12-03 21:12:47 +08:00
.ignore Add .ignore file to make config.toml searchable in vscode 2024-06-24 10:15:16 +02:00
.mailmap Update mailmap 2024-12-01 22:07:51 -05:00
Cargo.lock Remove jobserver from Session 2024-12-13 10:21:22 +00:00
Cargo.toml Bump Clippy version -> 0.1.85 2024-11-28 18:57:52 +01:00
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 build.vendor documentation 2024-12-04 16:02:07 +03:00
configure Ensure ./configure works when configure.py path contains spaces 2024-02-16 18:57:22 +00:00
CONTRIBUTING.md fix: Update CONTRIBUTING.md recommend -> recommended 2023-11-16 23:57:09 +05:30
COPYRIGHT Synchronize Unicode license text from unicode.org 2024-11-20 00:54:12 -08:00
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 collect-license-metadata: move JSON to root, and add a 'check' mode 2024-11-25 14:14:57 +00:00
LICENSE-MIT LICENSE-MIT: Remove inaccurate (misattributed) copyright notice 2017-07-26 16:51:58 -07:00
README.md Grammar fixes 2024-12-09 17:17:27 -05:00
RELEASES.md Removed Unnecessary Spaces From RELEASES.md 2024-12-07 01:01:03 +05:30
REUSE.toml collect-license-metadata: move JSON to root, and add a 'check' mode 2024-11-25 14:14:57 +00:00
rust-bors.toml Increase timeout for new bors bot 2024-03-13 08:31:07 +01:00
rustfmt.toml chore(style): sync submodule exclusion list between tidy and rustfmt 2024-11-02 16:43:10 +03:00
triagebot.toml Rollup merge of #134089 - Urgau:triagebot-exceptions, r=ehuss 2024-12-12 19:00:42 +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.

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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.

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If you want to use these names or brands, please read the media guide.

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