Commit graph

287473 commits

Author SHA1 Message Date
Nicholas Nethercote
92799b6f89 Separate Analysis and Results.
`Results` contains and `Analysis` and an `EntryStates`. The unfortunate
thing about this is that the analysis needs to be mutable everywhere
(`&mut Analysis`) which forces the `Results` to be mutable everywhere,
even though `EntryStates` is immutable everywhere.

To fix this, this commit renames `Results` as `AnalysisAndResults`,
renames `EntryStates` as `Results`, and separates the analysis and
results as much as possible. (`AnalysisAndResults` doesn't get much use,
it's mostly there to facilitate method chaining of
`iterate_to_fixpoint`.)

`Results` is immutable everywhere, which:
- is a bit clearer on how the data is used,
- avoids an unnecessary clone of entry states in
  `locals_live_across_suspend_points`, and
- moves the results outside the `RefCell` in Formatter.

The commit also reformulates `ResultsHandle` as the generic `CowMut`,
which is simpler than `ResultsHandle` because it doesn't need the
`'tcx` lifetime and the trait bounds. It also which sits nicely
alongside the new use of `Cow` in `ResultsCursor`.
2025-04-24 11:36:07 +10:00
Nicholas Nethercote
4ff55588d3 Pass Analysis to visit_* instead of Results.
Every `Results` contains an `Analysis`, but these methods only need the
`Analysis`. No point passing them more data than they need.
2025-04-24 11:34:06 +10:00
bors
fa58ce343a Auto merge of #138845 - compiler-errors:stall-generators, r=lcnr
Properly stall coroutine witnesses in new solver

TODO: write description

r? lcnr
2025-04-23 21:35:15 +00:00
bors
df35ff6c35 Auto merge of #139983 - flip1995:clippy-subtree-update, r=Manishearth
Clippy subtree update

r? `@Manishearth`

Cargo.lock update due to the Clippy version bump and because Clippy moved from rinja (unmaintained) to askama.

Last sync was skipped due to the askama issue and me not getting to fixing this in time.
2025-04-23 18:23:51 +00:00
bors
553600e0f5 Auto merge of #140180 - ChrisDenton:rollup-5pvs08u, r=ChrisDenton
Rollup of 7 pull requests

Successful merges:

 - #140142 (Some more graphviz tweaks)
 - #140146 (Update `compiler_builtins` to 0.1.156)
 - #140147 (Clean: rename `open_braces` to `open_delimiters` in lexer and move `make_unclosed_delims_error` into `diagnostics.rs`.)
 - #140160 (Use `is_lang_item` and `as_lang_item` instead of handrolling their logic)
 - #140163 (Validate extension in `PathBuf::add_extension`)
 - #140173 (Ping Mara when touching format_args!() internals.)
 - #140175 (`rc""` more clear error message)

r? `@ghost`
`@rustbot` modify labels: rollup
2025-04-23 15:12:33 +00:00
Michael Goulet
f943f73db4 More 2025-04-23 15:09:25 +00:00
bors
be181dd75c Auto merge of #139998 - Zalathar:new-executor, r=onur-ozkan
compiletest: Use the new non-libtest executor by default

The new executor was implemented in #139660, but required a manual opt-in. This PR activates the new executor by default, but leaves the old libtest-based executor in place (temporarily) to make reverting easier if something unexpectedly goes horribly wrong.

Currently the new executor can be explicitly disabled by passing the `-N` flag to compiletest (e.g. `./x test ui -- -N`), but eventually that flag will be removed, alongside the removal of the libtest dependency. The flag is mostly there to make manual comparative testing easier if something does go wrong.

As before, there *should* be no user-visible difference between the old executor and the new executor.

---

I didn't get much of a response to my [call for testing thread on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/122651-general/topic/Call.20for.20testing.3A.20New.20test.20executor.20for.20compiletest/with/512452105), and the reports I did get (along with my own usage) indicate that there aren't any problems. So I think it's reasonable to move forward with making this the default, in the hopes of being able to remove the libtest dependency relatively soon.

When the libtest dependency is removed, it should be reasonable to build compiletest against pre-built stage0 std by default, even after the stage0 redesign. (Though we should probably have at least one CI job using in-tree stage1 std instead, to guard against the possibility of the `#![feature(internal_output_capture)]` API actually changing.)
2025-04-23 12:12:31 +00:00
Philipp Krones
e8737e3530
Clippy: Fix doc issue 2025-04-23 10:51:22 +02:00
bors
645d0ad2a4 Auto merge of #138591 - Kobzol:git-ci, r=Mark-Simulacrum
Refactor git change detection in bootstrap

While working on https://github.com/rust-lang/rust/pull/138395, I finally found the courage to delve into the insides of git path change detection in bootstrap, which is used (amongst other things) to detect if we should rebuilt od download `[llvm|rustc|gcc]`. I found it a bit hard to understand, and given that this code was historically quite fragile, I thought that it would be better to rebuild it from scratch.

The previous approach had a bunch of limitations:
- It separated the computation of "are there local changes?" and "what upstream SHA should we use?" even though these two things are intertwined.
- It used hacks to work around what happens on CI.
- It had special cases for CI scattered throughout the codebase, rather than centralized in one place.
- It wasn't documented enough and didn't have tests for the git behavior.

The current approach should hopefully resolve all of that. I implemented a single entrypoint called `check_path_modifications` (naming bikeshed pending, half of the time I spend on this PR was thinking about names, as it's quite tricky here..) that explicitly receives a mode of operation (in CI or outside CI), and accordingly figures out that upstream SHA that we should use for downloading artifacts and it also figures out if there are any local changes. Users of this function can then use this unified output to implement `download-ci-X` and other functionality. Notably, this change detection no longer uses `git merge-base`, which makes it easier to use and doesn't require setting up remotes.

I also added a bunch of integration tests that literally spawn a git repository on disk and then check that the function can deal with various situations (PR CI, auto/try CI, local builds).

After I built this inner layer, I used it for downloading GCC, LLVM and rustc. The latter two (and especially rustc) were using the `last_modified_commit` function before, but in all cases but one this function was actually only used to check if there are any local changes, which was IMO confusing. The LLVM handling would deserve a bit of refactoring, but that's a larger change that can be done as a follow-up.

I hope that the implementation is now clear and easy to understand, so that in combination with the tests we can have more confidence that it does what we want. I tried to include a lot of documentation in the code, so I won't be repeating the actual implementation details here, if there are any questions, I'll add the answers to the documentation too :)

The new approach explicitly supports three scenarios:
- Running on PR CI, where we have one upstream bors parent commit and one PR merge commit made by GitHub.
- Running on try/auto CI, where we have one upstream bors parent commit and one PR merge commit made by bors.
- Running locally, where we assume that we have at least one upstream bors parent commit in our git history.

I removed the handling of upstreams on CI, as I think that it shouldn't be needed and I considered it to be a hack. However, it's possible that there are other use-cases that I haven't considered, so I want to ask around if people have other situations than the three use-cases described above. If there are other such use-cases, I would like to include them in the new centralized implementation and add them to the git test suite, rather than going back to the old ways :)

In particular, the code before relied on `git merge-base`, but I don't see why we can't just lookup the most recent bors commit and assume that is a merge commit that is also upstream? I might be running into Chesterton's Fence here :)

CC `@pietroalbini` To make sure that this won't break downstream users of Rust's CI.

Best reviewed commit by commit.

Companion PRs:
- For testing beta: https://github.com/rust-lang/rust/pull/138597

r? `@onur-ozkan`

Fixes: https://github.com/rust-lang/rust/issues/101907

try-job: x86_64-gnu-aux
try-job: aarch64-gnu
try-job: dist-x86_64-apple
2025-04-23 03:10:04 +00:00
Zalathar
bf4b2a94f7 compiletest: Use the new non-libtest executor by default
Currently the new executor can be explicitly disabled by passing the `-N` flag
to compiletest (e.g. `./x test ui -- -N`), but eventually that flag will be
removed, alongside the removal of the libtest dependency.
2025-04-23 12:48:05 +10:00
Chris Denton
ecb9775438
Rollup merge of #140175 - Kivooeo:new-fix-one, r=compiler-errors
`rc""` more clear error message

here is small fix that provides better error message when user is trying to use `rc""` the same way it was made for `rb""`

example of it's work

```rust
  |
2 |     rc"\n";
  |     ^^ unknown prefix
  |
  = note: prefixed identifiers and literals are reserved since Rust 2021
help: use `cr` for a raw C-string
  |
2 -     rc"\n";
2 +     cr"\n";
  |
```

**related issue**
fixes #140170

cc `@cyrgani` (issue author)
2025-04-23 00:43:08 +00:00
Chris Denton
45b5d8bb5a
Rollup merge of #140173 - m-ou-se:triagebot-config, r=ChrisDenton
Ping Mara when touching format_args!() internals.
2025-04-23 00:43:08 +00:00
Chris Denton
ed4e167c4a
Rollup merge of #140163 - thaliaarchi:pathbuf-validate-extension, r=ChrisDenton
Validate extension in `PathBuf::add_extension`

The extension is validated in `PathBuf::set_extension`, but not `add_extension`. Fix that. Check for both `/` and `\` path separators on Windows, even when the path is verbatim, since this is logically like `PathBuf::push` which normalizes separators (i.e., keeping the current behavior).

`PathBuf::add_extension` is tracked in #127292.

r? `@ChrisDenton`
2025-04-23 00:43:07 +00:00
Chris Denton
b03267fc11
Rollup merge of #140160 - oli-obk:lang-items, r=jieyouxu
Use `is_lang_item` and `as_lang_item` instead of handrolling their logic

Various cleanups and deduplication. Most notably `if is_lang_item(foo, bar) {} else if is_lang_item...` chains are turned into matches. No behaviour changes intended beyond turning ICEs into fatal "lang item not found" errors
2025-04-23 00:43:07 +00:00
Chris Denton
090f6a9629
Rollup merge of #140147 - xizheyin:issue-138401-1, r=compiler-errors
Clean: rename `open_braces` to `open_delimiters` in lexer and move `make_unclosed_delims_error` into `diagnostics.rs`.

Clean code prepared for resolving #138401. To avoid having too many extraneous changes in one PR, I cleaned up some of the naming and method placement in lexer in this PR.
1. For the make_unclosed_delims_error function defined in mod.rs is only used in lexer, so moved into lexer, which enhances encapsulation.
2. For open_braces in TokenTreeDiagInfo the naming is not canonical, as Brace refers to `{...} ` and this variable can store all kinds of different Delimiters. so I named it open_delimiters.

r? `@chenyukang`
2025-04-23 00:43:06 +00:00
Chris Denton
538ae9979b
Rollup merge of #140146 - tgross35:update-builtins, r=tgross35
Update `compiler_builtins` to 0.1.156

Includes the following changes:

* Provide `abort` on AVR [1]

[1]: https://github.com/rust-lang/compiler-builtins/pull/830
2025-04-23 00:43:05 +00:00
Chris Denton
1b9e11ed3b
Rollup merge of #140142 - nnethercote:some-graphviz-tweaks-2, r=compiler-errors
Some more graphviz tweaks

A follow-up to #132346.

r? `@davidtwco`
2025-04-23 00:43:05 +00:00
Kivooeo
44b19e5fe7 rc and cr more clear error message 2025-04-23 03:15:43 +05:00
bors
1a5bf12f65 Auto merge of #140165 - ChrisDenton:rollup-on2dpr5, r=ChrisDenton
Rollup of 8 pull requests

Successful merges:

 - #139617 (Use posix_spawn on cygwin)
 - #139921 (improve diagnostic for raw pointer field access with ->)
 - #140031 (compiletest: Fix deadline bugs in new executor)
 - #140072 (handle function alignment in miri)
 - #140104 (Fix auto diff failing on inherent impl blocks)
 - #140124 (Update books)
 - #140144 (Handle another negated literal in `eat_token_lit`.)
 - #140149 (test_nan: ensure the NAN contant is quiet)

r? `@ghost`
`@rustbot` modify labels: rollup
2025-04-22 22:09:56 +00:00
Mara Bos
634baf4a46 Ping Mara when touching format_args!() internals. 2025-04-22 23:01:42 +02:00
Michael Goulet
7c1661f945 Consider Copy/Clone too 2025-04-22 17:05:15 +00:00
Michael Goulet
1727badf77 Don't compute query unless in new solver 2025-04-22 17:04:59 +00:00
Michael Goulet
a922983393 Eagerly instantiate coroutine witness in new solver 2025-04-22 16:50:38 +00:00
Michael Goulet
169955f3be Properly drain pending obligations for coroutines 2025-04-22 16:50:38 +00:00
Michael Goulet
67df5b9cfa Collect and resolve ambiguous obligations from normalizing in writeback 2025-04-22 16:50:38 +00:00
Philipp Krones
50a5793766
tidy: Remove rinja deps from proc_macro_deps 2025-04-22 18:24:44 +02:00
Philipp Krones
d98cbeadb4
Update Cargo.lock 2025-04-22 18:24:43 +02:00
Philipp Krones
52bb2bb461
Merge commit '0621446356' into clippy-subtree-update 2025-04-22 18:24:43 +02:00
Chris Denton
2d8264fb08
Rollup merge of #140149 - RalfJung:test_nan, r=tgross35
test_nan: ensure the NAN contant is quiet

Follow-up to https://github.com/rust-lang/rust/pull/139483

r? ``@tgross35``
2025-04-22 15:24:09 +00:00
Chris Denton
15f8847a25
Rollup merge of #140144 - nnethercote:fix-140098, r=petrochenkov
Handle another negated literal in `eat_token_lit`.

Extends the change from #139653, which was on expressions, to literals.

Fixes #140098.

r? ``@petrochenkov``
2025-04-22 15:24:08 +00:00
Chris Denton
9471811e20
Rollup merge of #140124 - rustbot:docs-update, r=ehuss
Update books

## rust-lang/nomicon

1 commits in 0c10c30cc54736c5c194ce98c50e2de84eeb6e79..c76a20f0d987145dcedf05c5c073ce8d91f2e82a
2025-04-15 20:54:57 UTC to 2025-04-15 20:54:57 UTC

- Say that dereferencing a pointer to a ZST is no longer undefined (rust-lang/nomicon#467)

## rust-lang/reference

7 commits in 3340922df189bddcbaad17dc3927d51a76bcd5ed..3bf3402aea982b876eb56c87da17b0685c6461d5
2025-04-18 13:44:45 UTC to 2025-04-17 17:27:01 UTC

- Use `cfg(false)` instead of `cfg(FALSE)` (rust-lang/reference#1763)
-     Add `cfg(true)` and `cfg(false)` to conditional compilation (RFC 3695) (rust-lang/reference#1762)
- Refactor rendering with `RenderCtx` (rust-lang/reference#1796)
- attributes/codegen: update aarch64 features (rust-lang/reference#1791)
- Simplify GenericParams grammar (rust-lang/reference#1795)
- Add rule identifiers for the ABI chapter (rust-lang/reference#1793)
- Remove broken footnote links from grammar summary (rust-lang/reference#1794)
2025-04-22 15:24:08 +00:00
Chris Denton
264249fbe1
Rollup merge of #140104 - Shourya742:2025-04-21-auto-diff-fails-on-impl-block, r=ZuseZ4
Fix auto diff failing on inherent impl blocks

closes: #139557

r? ``@ZuseZ4``
2025-04-22 15:24:07 +00:00
Chris Denton
107f04daa8
Rollup merge of #140072 - folkertdev:miri-fn-align, r=RalfJung
handle function alignment in miri

tracking issue: https://github.com/rust-lang/rust/issues/82232
Fixes https://github.com/rust-lang/miri/issues/4282

The `#[repr(align(N))]` attribute on functions was ignored when using miri. For such a function, its address should be a multiple of `N`.

There is some further discussion in the thread [#t-compiler/const-eval > function address alignment](https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/function.20address.20alignment) on how `dyn Fn` should be handled. The behavior there appears to be consistent between miri and nightly, though both may be incorrect. In any case, that can be resolved separately.
2025-04-22 15:24:06 +00:00
Chris Denton
c046a430d4
Rollup merge of #140031 - Zalathar:deadline, r=jieyouxu
compiletest: Fix deadline bugs in new executor

The experimental new executor for compiletest (#139660) was found to have two major bugs in deadline handling for detecting slow tests:

- The comparison between `now` and test deadlines was reversed, causing no timeouts to ever be recognised.
- After fixing that bug, it was found that the existing code would issue timeouts for any test that had started more than 60 seconds ago, even if the test had finished long before its deadline was reached.

This PR fixes those bugs.

(The new executor is not yet enabled by default, so this PR has no immediate effect on contributors.)

---

I noted in https://github.com/rust-lang/rust/pull/139998#issuecomment-2815127046 that I hoped to have some unit tests to accompany these fixes. Unfortunately that turned out to be infeasible, because `DeadlineQueue` is tightly coupled to concrete `mpsc::Receiver` APIs (in addition to `Instant::now`), and trying to mock all of those would make the code much more complicated.

I did, however, add a few assertions that would have caught the failure to remove tests from the queue after their deadline.

r? jieyouxu
2025-04-22 15:24:06 +00:00
Chris Denton
8089e317b5
Rollup merge of #139921 - Kivooeo:master, r=WaffleLapkin
improve diagnostic for raw pointer field access with ->

This PR enhances the error messages emitted by the Rust compiler when users attempt to use the `->` operator for field access on raw pointers or when dereferencing is needed. The changes aim to provide clearer guidance, by suggesting the correct use of the `.` operator and explicit dereferencing.

**Before:**
```
help: `xs` is a raw pointer; try dereferencing it
   |
LL |         (*xs)->count += 1;
   |         ++  +
```

**Now:**
```
help: use `.` on a dereferenced raw pointer instead
   |
LL -         xs->count += 1;
LL +         (*xs).count += 1;
   |
```

I added extra clarification in the message. Since this error occurs in the parser, we can't be certain that the type is a raw pointer. That's why the message includes only a small note in brackets. (In contrast, the message above is emitted in HIR, where we *can* check whether it's a raw pointer.)

**Before:**
```
  --> main.rs:11:11
   |
11 |         xs->count += 1;
   |           ^^
   |
   = help: the . operator will dereference the value if needed
```
**After:**
```
--> main.rs:11:11
   |
11 |         xs->count += 1;
   |           ^^
   |
   = help: the `.` operator will automatically dereference the value, except if the value is a raw pointer
```
2025-04-22 15:24:05 +00:00
Chris Denton
1586660fb2
Rollup merge of #139617 - Berrysoft:cygwin-posix-spawn, r=joboet
Use posix_spawn on cygwin

r? ``@joboet``

Depends on:
- [x] https://github.com/rust-lang/libc/pull/4387
- [x] https://github.com/rust-lang/rust/pull/140081
2025-04-22 15:24:05 +00:00
Philipp Krones
0621446356
Rustup (#14667)
Out of cycle sync, as the sync to Rust failed again and resolving
conflicts there is awkward.

r? @ghost

changelog: none
2025-04-22 14:01:53 +00:00
Philipp Krones
bdc432759d
Bump nightly version -> 2025-04-22 2025-04-22 15:56:20 +02:00
Philipp Krones
ac477dbde5
Merge remote-tracking branch 'upstream/master' into rustup 2025-04-22 15:55:19 +02:00
Jason Newcomb
c3fb102a41
Consider side effects when rewriting iterator behaviors (#14490)
Closes #9191
Closes #14444
Closes #8055

Adds a new helper to partly check for side effects by recursively
checking if the iterator type contains closures with mutable captures.

changelog: [`double_ended_iterator_last`] fix FP when iter has side
effects
changelog: [`needless_collect`] fix lint not consider side effects
2025-04-22 13:21:54 +00:00
yanglsh
a50e043d32 Expand mutable capture check for is_iter_with_side_effects() 2025-04-22 20:55:07 +08:00
Thalia Archibald
006b7e3a2b Validate extension in PathBuf::add_extension
The extension is validated in `PathBuf::set_extension`, but not
`add_extension`. Fix that. Check for both / and \ path separators on
Windows, even when the path is verbatim, since this is logically like
`PathBuf::push` which normalizes separators (i.e., keeping the current
behavior).
2025-04-22 05:34:25 -07:00
Zalathar
f7b1e035a8 compiletest: Fix deadline bugs in new executor 2025-04-22 22:03:00 +10:00
bors
6bc57c6bf7 Auto merge of #139960 - amandasystems:placeholder-ui-tests, r=lcnr
Add tests for two untested cases of placeholder relations

During work on #130227, I discovered several situations not covered by any previously existing UI test. This commit introudces tests to cover that.

r? lcnr
2025-04-22 11:05:54 +00:00
Oli Scherer
5d2952100f Use is_lang_item and as_lang_item instead of handrolling their logic 2025-04-22 11:02:37 +00:00
Amanda Stjerna
e9d374c657 Add tests for two untested cases of placeholder relations
During work on #130227, I discovered several situations not covered by any
previously existing UI test. This commit introudces tests to cover that.
2025-04-22 12:07:53 +02:00
Ralf Jung
47a1278841
add comment for "Other" case 2025-04-22 11:40:48 +02:00
bors
8bf5a8d12f Auto merge of #132833 - est31:stabilize_let_chains, r=fee1-dead
Stabilize let chains in the 2024 edition

# Stabilization report

This proposes the stabilization of `let_chains` ([tracking issue], [RFC 2497]) in the [2024 edition] of Rust.

[tracking issue]: https://github.com/rust-lang/rust/issues/53667
[RFC 2497]: https://github.com/rust-lang/rfcs/pull/2497
[2024 edition]: https://doc.rust-lang.org/nightly/edition-guide/rust-2024/index.html

## What is being stabilized

The ability to `&&`-chain `let` statements inside `if` and `while` is being stabilized, allowing intermixture with boolean expressions. The patterns inside the `let` sub-expressions can be irrefutable or refutable.

```Rust
struct FnCall<'a> {
    fn_name: &'a str,
    args: Vec<i32>,
}

fn is_legal_ident(s: &str) -> bool {
    s.chars()
        .all(|c| ('a'..='z').contains(&c) || ('A'..='Z').contains(&c))
}

impl<'a> FnCall<'a> {
    fn parse(s: &'a str) -> Option<Self> {
        if let Some((fn_name, after_name)) = s.split_once("(")
            && !fn_name.is_empty()
            && is_legal_ident(fn_name)
            && let Some((args_str, "")) = after_name.rsplit_once(")")
        {
            let args = args_str
                .split(',')
                .map(|arg| arg.parse())
                .collect::<Result<Vec<_>, _>>();
            args.ok().map(|args| FnCall { fn_name, args })
        } else {
            None
        }
    }
    fn exec(&self) -> Option<i32> {
        let iter = self.args.iter().copied();
        match self.fn_name {
            "sum" => Some(iter.sum()),
            "max" => iter.max(),
            "min" => iter.min(),
            _ => None,
        }
    }
}

fn main() {
    println!("{:?}", FnCall::parse("sum(1,2,3)").unwrap().exec());
    println!("{:?}", FnCall::parse("max(4,5)").unwrap().exec());
}
```

The feature will only be stabilized for the 2024 edition and future editions. Users of past editions will get an error with a hint to update the edition.

closes #53667

## Why 2024 edition?

Rust generally tries to ship new features to all editions. So even the oldest editions receive the newest features. However, sometimes a feature requires a breaking change so much that offering the feature without the breaking change makes no sense. This occurs rarely, but has happened in the 2018 edition already with `async` and `await` syntax. It required an edition boundary in order for `async`/`await` to become keywords, and the entire feature foots on those keywords.

In the instance of let chains, the issue is the drop order of `if let` chains. If we want `if let` chains to be compatible with `if let`, drop order makes it hard for us to [generate correct MIR]. It would be strange to have different behaviour for `if let ... {}` and `if true && let ... {}`. So it's better to [stay consistent with `if let`].

In edition 2024, [drop order changes] have been introduced to make `if let` temporaries be lived more shortly. These changes also affected `if let` chains. These changes make sense even if you don't take the `if let` chains MIR generation problem into account. But if we want to use them as the solution to the MIR generation problem, we need to restrict let chains to edition 2024 and beyond: for let chains, it's not just a change towards more sensible behaviour, but one required for correct function.

[generate correct MIR]: https://github.com/rust-lang/rust/issues/104843
[stay consistent with `if let`]: https://github.com/rust-lang/rust/pull/103293#issuecomment-1293408574
[drop order changes]: https://github.com/rust-lang/rust/issues/124085

## Introduction considerations

As edition 2024 is very new, this stabilization PR only makes it possible to use let chains on 2024 without that feature gate, it doesn't mark that feature gate as stable/removed. I would propose to continue offering the `let_chains` feature (behind a feature gate) for a limited time (maybe 3 months after stabilization?) on older editions to allow nightly users to adopt edition 2024 at their own pace. After that, the feature gate shall be marked as *stabilized*, not removed, and replaced by an error on editions 2021 and below.

## Implementation history

* History from before March 14, 2022 can be found in the [original stabilization PR] that was reverted.
* https://github.com/rust-lang/rust/pull/94927
* https://github.com/rust-lang/rust/pull/94951
* https://github.com/rust-lang/rust/pull/94974
* https://github.com/rust-lang/rust/pull/95008
* https://github.com/rust-lang/rust/pull/97295
* https://github.com/rust-lang/rust/pull/98633
* https://github.com/rust-lang/rust/pull/99731
* https://github.com/rust-lang/rust/pull/102394
* https://github.com/rust-lang/rust/pull/100526
* https://github.com/rust-lang/rust/pull/100538
* https://github.com/rust-lang/rust/pull/102998
* https://github.com/rust-lang/rust/pull/103405
* https://github.com/rust-lang/rust/pull/103293
* https://github.com/rust-lang/rust/pull/107251
* https://github.com/rust-lang/rust/pull/110568
* https://github.com/rust-lang/rust/pull/115677
* https://github.com/rust-lang/rust/pull/117743
* https://github.com/rust-lang/rust/pull/117770
* https://github.com/rust-lang/rust/pull/118191
* https://github.com/rust-lang/rust/pull/119554
* https://github.com/rust-lang/rust/pull/129394
* https://github.com/rust-lang/rust/pull/132828
* https://github.com/rust-lang/reference/pull/1179
* https://github.com/rust-lang/reference/pull/1251
* https://github.com/rust-lang/rustfmt/pull/5910

[original stabilization PR]: https://github.com/rust-lang/rust/pull/94927

## Adoption history

### In the compiler

* History before March 14, 2022 can be found in the [original stabilization PR].
* https://github.com/rust-lang/rust/pull/115983
* https://github.com/rust-lang/rust/pull/116549
* https://github.com/rust-lang/rust/pull/116688

### Outside of the compiler

* https://github.com/rust-lang/rust-clippy/pull/11750
* [rspack](https://github.com/web-infra-dev/rspack)
* [risingwave](https://github.com/risingwavelabs/risingwave)
* [dylint](https://github.com/trailofbits/dylint)
* [convex-backend](https://github.com/get-convex/convex-backend)
* [tikv](https://github.com/tikv/tikv)
* [Daft](https://github.com/Eventual-Inc/Daft)
* [greptimedb](https://github.com/GreptimeTeam/greptimedb)

## Tests

<details>

### Intentional restrictions

[`partially-macro-expanded.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/partially-macro-expanded.rs), [`macro-expanded.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/macro-expanded.rs): it is possible to use macros to expand to both the pattern and the expression inside a let chain, but not to the entire `let pat = expr` operand.
[`parens.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/parens.rs): `if (let pat = expr)` is not allowed in chains
[`ensure-that-let-else-does-not-interact-with-let-chains.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/ensure-that-let-else-does-not-interact-with-let-chains.rs): `let...else` doesn't support chaining.

### Overlap with match guards

[`move-guard-if-let-chain.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/move-guard-if-let-chain.rs): test for the `use moved value` error working well in match guards. could maybe be extended with let chains that have more than one `let`
[`shadowing.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/shadowing.rs): shadowing in if let guards works as expected
[`ast-validate-guards.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/ast-validate-guards.rs): let chains in match guards require the match guards feature gate

### Simple cases from the early days

PR #88642 has added some tests with very simple usages of `let else`, mostly as regression tests to early bugs.

[`then-else-blocks.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/then-else-blocks.rs)
[`ast-lowering-does-not-wrap-let-chains.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/ast-lowering-does-not-wrap-let-chains.rs)
[`issue-90722.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/issue-90722.rs)
[`issue-92145.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/issue-92145.rs)

### Drop order/MIR scoping tests

[`issue-100276.rs`](4adafcf40a/tests/ui/drop/issue-100276.rs): let expressions on RHS aren't terminating scopes
[`drop_order.rs`](4adafcf40a/tests/ui/drop/drop_order.rs): exhaustive temporary drop order test for various Rust constructs, including let chains
[`scope.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/scope.rs): match guard scoping test
[`drop-scope.rs`](4adafcf40a/tests/ui/rfcs/rfc-2294-if-let-guard/drop-scope.rs): another match guard scoping test, ensuring that temporaries in if-let guards live for the arm
[`drop_order_if_let_rescope.rs`](4adafcf40a/tests/ui/drop/drop_order_if_let_rescope.rs): if let rescoping on edition 2024, including chains
[`mir_let_chains_drop_order.rs`](4adafcf40a/tests/ui/mir/mir_let_chains_drop_order.rs): comprehensive drop order test for let chains, distinguishes editions 2021 and 2024.
[`issue-99938.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/issue-99938.rs), [`issue-99852.rs`](4adafcf40a/tests/ui/mir/issue-99852.rs) both bad MIR ICEs fixed by #102394

### Linting

[`irrefutable-lets.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/irrefutable-lets.rs): trailing and leading irrefutable let patterns get linted for, others don't. The lint is turned off for `else if`.
[`issue-121070-let-range.rs`](4adafcf40a/tests/ui/lint/issue-121070-let-range.rs): regression test for false positive of the unused parens lint, precedence requires the `()`s here

### Parser: intentional restrictions

[`disallowed-positions.rs`](2128d8df0e/tests/ui/rfcs/rfc-2497-if-let-chains/disallowed-positions.rs): `let` in expression context is rejected everywhere except at the top level
[`invalid-let-in-a-valid-let-context.rs`](4adafcf40a/tests/ui/rfcs/rfc-2497-if-let-chains/invalid-let-in-a-valid-let-context.rs): nested `let` is not allowed (let's are no legal expressions just because they are allowed in `if` and `while`).

### Parser: recovery

[`issue-103381.rs`](4adafcf40a/tests/ui/parser/issues/issue-103381.rs): Graceful recovery of incorrect chaining of `if` and `if let`
[`semi-in-let-chain.rs`](4adafcf40a/tests/ui/parser/semi-in-let-chain.rs): Ensure that stray `;`s in let chains give nice errors (`if_chain!` users might be accustomed to `;`s)
[`deli-ident-issue-1.rs`](4adafcf40a/tests/ui/parser/deli-ident-issue-1.rs), [`brace-in-let-chain.rs`](4adafcf40a/tests/ui/parser/brace-in-let-chain.rs): Ensure that stray unclosed `{`s in let chains give nice errors and hints

### Misc

[`conflicting_bindings.rs`](4adafcf40a/tests/ui/pattern/usefulness/conflicting_bindings.rs): the conflicting bindings check also works in let chains. Personally, I'd extend it to chains with multiple let's as well.
[`let-chains-attr.rs`](4adafcf40a/tests/ui/expr/if/attrs/let-chains-attr.rs): attributes work on let chains

### Tangential tests with `#![feature(let_chains)]`

[`if-let.rs`](4adafcf40a/tests/coverage/branch/if-let.rs): MC/DC coverage tests for let chains
[`logical_or_in_conditional.rs`](4adafcf40a/tests/mir-opt/building/logical_or_in_conditional.rs): not really about let chains, more about dropping/scoping behaviour of `||`
[`stringify.rs`](4adafcf40a/tests/ui/macros/stringify.rs): exhaustive test of the `stringify` macro
[`expanded-interpolation.rs`](4adafcf40a/tests/ui/unpretty/expanded-interpolation.rs), [`expanded-exhaustive.rs`](4adafcf40a/tests/ui/unpretty/expanded-exhaustive.rs): Exhaustive test of `-Zunpretty`
[`diverges-not.rs`](4adafcf40a/tests/ui/rfcs/rfc-0000-never_patterns/diverges-not.rs): Never type, mostly tangential to let chains

</details>

## Possible future work

* There is proposals to allow `if let Pat(bindings) = expr {}` to be written as `if expr is Pat(bindings) {}` ([RFC 3573]). `if let` chains are a natural extension of the already existing `if let` syntax, and I'd argue orthogonal towards `is` syntax.
  * https://github.com/rust-lang/lang-team/issues/297
* One could have similar chaining inside `let ... else` statements. There is no proposed RFC for this however, nor is it implemented on nightly.
* Match guards have the `if` keyword as well, but on stable Rust, they don't support `let`. The functionality is available via an unstable feature ([`if_let_guard` tracking issue]). Stabilization of let chains affects this feature in so far as match guards containing let chains now only need the `if_let_guard` feature gate be present instead of also the `let_chains` feature (NOTE: this PR doesn't implement this simplification, it's left for future work).

[RFC 3573]: https://github.com/rust-lang/rfcs/pull/3573
[`if_let_guard` tracking issue]: https://github.com/rust-lang/rust/issues/51114

## Open questions / blockers

- [ ] bad recovery if you don't put a `let` (I don't think this is a blocker): [#117977](https://github.com/rust-lang/rust/issues/117977)
- [x] An instance where a temporary lives shorter than with nested ifs, breaking compilation: [#103476](https://github.com/rust-lang/rust/issues/103476). Personally I don't think this is a blocker either, as it's an edge case. Edit: turns out to not reproduce in edition 2025 any more, due to let rescoping. regression test added in #133093
- [x] One should probably extend the tests for `move-guard-if-let-chain.rs` and `conflicting_bindings.rs` to have chains with multiple let's: done in 133093
- [x] Parsing rejection tests: addressed by https://github.com/rust-lang/rust/pull/132828
- [x] [Style](https://rust-lang.zulipchat.com/#narrow/channel/346005-t-style/topic/let.20chains.20stabilization.20and.20formatting): https://github.com/rust-lang/rust/pull/139456
- [x] https://github.com/rust-lang/rust/issues/86730 explicitly mentions `let_else`. I think we can live with `let pat = expr` not evaluating as `expr` for macro_rules macros, especially given that `let pat = expr` is not a legal expression anywhere except inside `if` and `while`.
- [x] Documentation in the reference: https://github.com/rust-lang/reference/pull/1740
- [x] Add chapter to the Rust 2024 [edition guide]: https://github.com/rust-lang/edition-guide/pull/337
- [x] Resolve open questions on desired drop order.

[original reference PR]: https://github.com/rust-lang/reference/pull/1179
[edition guide]: https://github.com/rust-lang/edition-guide
2025-04-22 07:54:10 +00:00
Ralf Jung
5717623778 MANTISSA_DIGITS: explain relation to bitwise representation 2025-04-22 09:07:05 +02:00
Ralf Jung
e7a865448a test_nan: ensure the NAN contant is quiet 2025-04-22 09:06:43 +02:00