Document the return keyword
Partial fix of #34601.
This documents the `return` keyword with two short example to explain it is not needed for the last expression in a function and a long example to show its use when interrupting a function execution early.
I did not put a link to the reference since the only link I found was https://doc.rust-lang.org/stable/reference/expressions/return-expr.html#return-expressions.
@rustbot modify labels: T-doc,C-enhancement
Document the mut keyword
Partial fix for #34601.
Documentation for the `mut` keyword. I think it's okay for it to be quite short, this is not the book not the reference, but if you find something is missing, do not hesitate to tell me.
Provide suggestions for some moved value errors
When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix#63988.
When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix#62112.
Emit line info for generator variants
Debuggers should be able to read a generator / async fn state machine and show the line it's suspended at. Eventually, this could grow into an "async stack trace" feature of sorts. While no debugger support this for Rust today, this PR adds the debuginfo necessary for that support to exist.
[This gist](https://gist.github.com/tmandry/6d7004fa008684f76809208847459f9b) shows the resulting debuginfo for a simple example. Here's a snippet:
```
0x00000986: DW_TAG_variant
DW_AT_discr_value (0x03)
0x00000988: DW_TAG_member
DW_AT_name ("3")
DW_AT_type (0x000009bc "Suspend0")
DW_AT_decl_file ("/home/tmandry/code/playground/generator-simple.rs")
DW_AT_decl_line (6)
DW_AT_alignment (8)
DW_AT_data_member_location (0x00)
```
The file and line have been added here. The line currently points to the beginning of the statement containing the yield (or await), because that's what the MIR source info points to for the yield terminator. (We may want to point to the yield or await line specifically, but that can be done independently of this change.)
Debuggers don't know how to use this kind of info yet. However, we're hoping to experiment with adding such support to Fuchsia's debugger. It would be exciting if someone were interested in adding similar to support to gdb/lldb.
r? @oli-obk
cc @eddyb @jonas-schievink
Part of #73524.
Add unstable `core::mem::variant_count` intrinsic
Adds a new `const fn` intrinsic which can be used to determine the number of variants in an `enum`.
I've shown this to a couple of people and they invariably ask 'why on earth?', but there's actually a very neat use case:
At the moment, if you want to create an opaque array type that's indexed by an `enum` with one element for each variant, you either have to hard-code the number of variants, add a `LENGTH` variant or use a `Vec`, none of which are suitable in general (number of variants could change; pattern matching `LENGTH` becomes frustrating; might not have `alloc`). By including this intrinsic, it becomes possible to write the following:
```rust
#[derive(Copy, Clone)]
enum OpaqueIndex {
A = 0,
B,
C,
}
struct OpaqueVec<T>(Box<[T; std::mem::num_variants::<OpaqueIndex>()]>);
impl<T> std::ops::Index<OpaqueIndex> for OpaqueVec<T> {
type Output = T;
fn index(&self, idx: OpaqueIndex) -> &Self::Output {
&self.0[idx as usize]
}
}
```
(We even have a use cases for this in `rustc` and I plan to use it to re-implement the lang-items table.)
Implement mixed script confusable lint.
This implements the mixed script confusable lint defined in RFC 2457.
This is blocked on #72069 and https://github.com/unicode-rs/unicode-security/pull/13, and will need a Cargo.toml version bump after those are resolved.
The lint message warning is sub-optimal for now. We'll need a mechanism to properly output `AugmentScriptSet` to screen, this is to be added in `unicode-security` crate.
r? @Manishearth
Self contained linking option
With objects moved to self-contained directory by https://github.com/rust-lang/rust/pull/72999 we can now add option to control whether to use self-contained on native linkage mode.
Add a fast path for `std:🧵:panicking`.
This is done by adding a global atomic variable (non-TLS) that counts how many threads are panicking. In order to check if the current thread is panicking, this variable is read and, if it is zero, no thread (including the one where `panicking` is being called) is panicking and `panicking` can return `false` immediately without needing to access TLS. If the global counter is not zero, the local counter is accessed from TLS to check if the current thread is panicking.
Print environment variables accessed by rustc as special comments into depinfo files
So cargo (and perhaps others tools) can use them for linting (at least) or for actually rebuilding crates on env var changes.
---
I've recently observed one more forgotten environment variable in a build script 8a77d1ca3f and thought it would be nice to provide the list of accessed variables to cargo automatically as a part of depinfo.
Unsurprisingly, I wasn't the first who had this idea - cc https://github.com/rust-lang/rust/issues/70517https://github.com/rust-lang/rust/issues/40364https://github.com/rust-lang/rust/issues/44074.
Also, there are dozens of uses of `(option_)env!` in rustc repo and, like, half of them are not registered in build scripts.
---
Description:
- depinfo files are extended with special comments containing info about environment variables accessed during compilation.
- Comment format for environment variables with successfully retrieved value: `# env-dep:KEY=VALUE`.
- Comment format for environment variables without successfully retrieved value: `# env-dep:KEY` (can happen with `option_env!`).
- `KEY` and `VALUE` are minimally escaped (`\n`, `\r`, `\\`) so they don't break makefile comments and can be unescaped by anything that can unescape standard `escape_default` and friends.
FCP report: https://github.com/rust-lang/rust/pull/71858#issuecomment-633071488
Closes https://github.com/rust-lang/rust/issues/70517
Closes https://github.com/rust-lang/rust/issues/40364
Closes https://github.com/rust-lang/rust/issues/44074
A new issue in the cargo repo will be needed to track the cargo side of this feature.
r? @ehuss
Add TryFrom<{int}> for NonZero{int}
Adds `TryFrom<{int}> for NonZero{int}`.
It uses the existing `NonZero{int}::new()` and `Option::ok_or()` functions, meaning the checks are not repeated.
I also added tests, I tried to follow the convention I saw in the test file.
I also used `#[stable(feature = "nzint_try_from_int_conv", since = "1.46.0")]`, but I have no idea if the feature/version are correctly named or even correct.
Implement associated lang items
Fixes#70718
This commit allows making associated items (e.g. associated functions
and types) into lang items via the `#[lang]` attribute. This allows such
items to be accessed directly, rather than by iterating over the parent
item's associated items.
I've added `FnOnce::Output` as a lang item, and updated one old usage to
use the new lang item. The remaining uses can be updated separately.
When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix#63988.
When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix#62112.
Add procedure for prioritization notifications on Zulip
This PR was originally opened by @LeSeulArtichaut as #73695, closing that one in favor of this one. Made some slight changes to it but can't push to @LeSeulArtichaut branch.
r? @wesleywiser @rust-lang/wg-prioritization
Add UI test for issue 73592
It happens that #72280 accidentally fixed a bug which is later discovered in #73592. This PR adds a UI test to prevent future regression.
Closes#73592
Allow dynamic linking for iOS/tvOS targets
During the development and testing of the [Crabapple project](https://github.com/Crabapple-iOS/Crabapple), one obstacle was the lack of `cdylib` target support for iOS. Surprisingly, once `dynamic_linking` was enabled for iOS targets, it worked seemingly flawlessly.
I could not find any information on why this was initially or still is disabled.
`improper_ctypes_definitions` lint
Addresses #19834, #66220, and #66373.
This PR takes another attempt at #65134 (reverted in #66378). Instead of modifying the existing `improper_ctypes` lint to consider `extern "C" fn` definitions in addition to `extern "C" {}` declarations, this PR adds a new lint - `improper_ctypes_definitions` - which only applies to `extern "C" fn` definitions.
In addition, the `improper_ctype_definitions` lint differs from `improper_ctypes` by considering `*T` and `&T` (where `T: Sized`) FFI-safe (addressing #66220).
There wasn't a clear consensus in #66220 (where the issues with #65134 were primarily discussed) on the approach to take, but there has [been some discussion in Zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/.2366220.20improper_ctypes.20definitions.20vs.20declarations/near/198903086). I fully expect that we'll want to iterate on this before landing.
cc @varkor + @shepmaster (from #19834) @hanna-kruppe (active in discussing #66220), @SimonSapin (#65134 caused problems for Servo, want to make sure that this PR doesn't)
Verify that the binop trait *is* implemented for the types *if* all the
involved type parameters are replaced with fresh inferred types. When
this is the case, it means that the type parameter was indeed missing a
trait bound. If this is not the case, provide a generic `note` refering
to the type that doesn't implement the expected trait.
Fixes#70718
This commit allows making associated items (e.g. associated functions
and types) into lang items via the `#[lang]` attribute. This allows such
items to be accessed directly, rather than by iterating over the parent
item's associated items.
I've added `FnOnce::Output` as a lang item, and updated one old usage to
use the new lang item. The remaining uses can be updated separately.
