aa5740c715
Implement coherence checks for negative trait impls The main purpose of this PR is to be able to [move Error trait to core](https://github.com/rust-lang/project-error-handling/issues/3). This feature is necessary to handle the following from impl on box. ```rust impl From<&str> for Box<dyn Error> { ... } ``` Without having negative traits affect coherence moving the error trait into `core` and moving that `From` impl to `alloc` will cause the from impl to no longer compiler because of a potential future incompatibility. The compiler indicates that `&str` _could_ introduce an `Error` impl in the future, and thus prevents the `From` impl in `alloc` that would cause overlap with `From<E: Error> for Box<dyn Error>`. Adding `impl !Error for &str {}` with the negative trait coherence feature will disable this error by encoding a stability guarantee that `&str` will never implement `Error`, making the `From` impl compile. We would have this in `alloc`: ```rust impl From<&str> for Box<dyn Error> {} // A impl<E> From<E> for Box<dyn Error> where E: Error {} // B ``` and this in `core`: ```rust trait Error {} impl !Error for &str {} ``` r? `@nikomatsakis` This PR was built on top of `@yaahc` PR #85764. Language team proposal: to https://github.com/rust-lang/lang-team/issues/96 |
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| bootstrap | ||
| build_helper | ||
| ci | ||
| doc | ||
| etc | ||
| librustdoc | ||
| llvm-project@a7348ae0df | ||
| rustdoc-json-types | ||
| test | ||
| tools | ||
| README.md | ||
| stage0.json | ||
| version | ||
This directory contains the source code of the rust project, including:
- The test suite
- The bootstrapping build system
- Various submodules for tools, like rustdoc, rls, etc.
For more information on how various parts of the compiler work, see the rustc dev guide.