df5deaf921
remove `feature(inline_const_pat)` Summarizing https://rust-lang.zulipchat.com/#narrow/channel/144729-t-types/topic/remove.20feature.28inline_const_pat.29.20and.20shared.20borrowck. With https://github.com/rust-lang/types-team/issues/129 we will start to borrowck items together with their typeck parent. This is necessary to correctly support opaque types, blocking the new solver and TAIT/ATPIT stabilization with the old one. This means that we cannot really support `inline_const_pat` as they are implemented right now: - we want to typeck inline consts together with their parent body to allow inference to flow both ways and to allow the const to refer to local regions of its parent.This means we also need to borrowck the inline const together with its parent as that's necessary to properly support opaque types - we want the inline const pattern to participate in exhaustiveness checking - to participate in exhaustiveness checking we need to evaluate it, which requires borrowck, which now relies on borrowck of the typeck root, which ends up checking exhaustiveness again. **This is a query cycle**. There are 4 possible ways to handle this: - stop typechecking inline const patterns together with their parent - causes inline const patterns to be different than inline const exprs - prevents bidirectional inference, we need to either fail to compile `if let const { 1 } = 1u32` or `if let const { 1u32 } = 1` - region inference for inline consts will be harder, it feels non-trivial to support inline consts referencing local regions from the parent fn - inline consts no longer participate in exhaustiveness checking. Treat them like `pat if pat == const { .. }` instead. We then only evaluate them after borrowck - difference between `const { 1 }` and `const FOO: usize = 1; match x { FOO => () }`. This is confusing - do they carry their weight if they are now just equivalent to using an if-guard - delay exhaustiveness checking until after borrowck - should be possible in theory, but is a quite involved change and may have some unexpected challenges - remove this feature for now I believe we should either delay exhaustiveness checking or remove the feature entirely. As moving exhaustiveness checking to after borrow checking is quite complex I think the right course of action is to fully remove the feature for now and to add it again once/if we've got that implementation figured out. `const { .. }`-expressions remain stable. These seem to have been the main motivation for https://github.com/rust-lang/rfcs/issues/2920. r? types cc `@rust-lang/types` `@rust-lang/lang` #76001 |
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| CODE_OF_CONDUCT.md | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
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| book.toml | ||
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README.md
This is a collaborative effort to build a guide that explains how rustc works. The aim of the guide is to help new contributors get oriented to rustc, as well as to help more experienced folks in figuring out some new part of the compiler that they haven't worked on before.
You can read the latest version of the guide here.
You may also find the rustdocs for the compiler itself useful. Note that these are not intended as a guide; it's recommended that you search for the docs you're looking for instead of reading them top to bottom.
For documentation on developing the standard library, see
std-dev-guide.
Contributing to the guide
The guide is useful today, but it has a lot of work still to go.
If you'd like to help improve the guide, we'd love to have you! You can find plenty of issues on the issue tracker. Just post a comment on the issue you would like to work on to make sure that we don't accidentally duplicate work. If you think something is missing, please open an issue about it!
In general, if you don't know how the compiler works, that is not a problem! In that case, what we will do is to schedule a bit of time for you to talk with someone who does know the code, or who wants to pair with you and figure it out. Then you can work on writing up what you learned.
In general, when writing about a particular part of the compiler's code, we recommend that you link to the relevant parts of the rustc rustdocs.
Build Instructions
To build a local static HTML site, install mdbook with:
> cargo install mdbook mdbook-linkcheck2 mdbook-toc mdbook-mermaid
and execute the following command in the root of the repository:
> mdbook build --open
The build files are found in the book/html directory.
Link Validations
We use mdbook-linkcheck2 to validate URLs included in our documentation. Link
checking is not run by default locally, though it is in CI. To enable it
locally, set the environment variable ENABLE_LINKCHECK=1 like in the
following example.
$ ENABLE_LINKCHECK=1 mdbook serve
Table of Contents
We use mdbook-toc to auto-generate TOCs for long sections. You can invoke the preprocessor by
including the <!-- toc --> marker at the place where you want the TOC.
Synchronizing josh subtree with rustc
This repository is linked to rust-lang/rust as a josh subtree. You can use the following commands to synchronize the subtree in both directions.
You'll need to install josh-proxy locally via
cargo +stable install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04
Older versions of josh-proxy may not round trip commits losslessly so it is important to install this exact version.
Pull changes from rust-lang/rust into this repository
- Checkout a new branch that will be used to create a PR into
rust-lang/rustc-dev-guide - Run the pull command
$ cargo run --manifest-path josh-sync/Cargo.toml rustc-pull - Push the branch to your fork and create a PR into
rustc-dev-guide
Push changes from this repository into rust-lang/rust
- Run the push command to create a branch named
<branch-name>in arustcfork under the<gh-username>account$ cargo run --manifest-path josh-sync/Cargo.toml rustc-push <branch-name> <gh-username> - Create a PR from
<branch-name>intorust-lang/rust
Minimal git config
For simplicity (ease of implementation purposes), the josh-sync script simply calls out to system git. This means that the git invocation may be influenced by global (or local) git configuration.
You may observe "Nothing to pull" even if you know rustc-pull has something to pull if your global git config sets fetch.prunetags = true (and possibly other configurations may cause unexpected outcomes).
To minimize the likelihood of this happening, you may wish to keep a separate minimal git config that only has [user] entries from global git config, then repoint system git to use the minimal git config instead. E.g.
$ GIT_CONFIG_GLOBAL=/path/to/minimal/gitconfig GIT_CONFIG_SYSTEM='' cargo +stable run --manifest-path josh-sync/Cargo.toml -- rustc-pull