repr(transparent): it's fine if the one non-1-ZST field is a ZST
This code currently gets rejected:
```rust
#[repr(transparent)]
struct MyType([u16; 0])
```
That clearly seems like a bug to me: `repr(transparent)` [got defined ](https://github.com/rust-lang/rust/issues/77841#issuecomment-716575747) as having any number of 1-ZST fields plus optionally one more field; `MyType` clearly satisfies that definition.
This PR changes the `repr(transparent)` logic to actually match that definition.
Make `.rmeta` file in `dep-info` have correct name (`lib` prefix)
Since `filename_for_metadata()` and
`OutputFilenames::path(OutputType::Metadata)` had different logic for the name of the metadata file, the `.d` file contained a file name different from the actual name used. Share the logic to fix the out-of-sync name.
Without this fix, the `.d` file contained
dash-separated_something-extra.rmeta: dash-separated.rs
instead of
libdash_separated_something-extra.rmeta: dash-separated.rs
which is the name of the file that is actually written by the compiler.
Worth noting: It took me several iterations to get all tests to pass, so I am relatively confident that this PR does not break anything.
Closes#68839
`#[diagnostic::on_unimplemented]` without filters
This commit adds support for a `#[diagnostic::on_unimplemented]` attribute with the following options:
* `message` to customize the primary error message
* `note` to add a customized note message to an error message
* `label` to customize the label part of the error message
The relevant behavior is specified in [RFC-3366](https://rust-lang.github.io/rfcs/3366-diagnostic-attribute-namespace.html)
closure field capturing: don't depend on alignment of packed fields
This fixes the closure field capture part of https://github.com/rust-lang/rust/issues/115305: field capturing always stops at projections into packed structs, no matter the alignment of the field. This means changing a private field type from `u8` to `u64` can never change how closures capture fields, which is probably what we want.
Here's an example where, before this PR, changing the type of a private field in a repr(Rust) struct can change the output of a program:
```rust
#![allow(dead_code)]
mod m {
// before patch
#[derive(Default)]
pub struct S1(u8);
// after patch
#[derive(Default)]
pub struct S2(u64);
}
struct NoisyDrop;
impl Drop for NoisyDrop {
fn drop(&mut self) {
eprintln!("dropped!");
}
}
#[repr(packed)]
struct MyType {
field: m::S1, // output changes when this becomes S2
other_field: NoisyDrop,
third_field: Vec<()>,
}
fn test(r: MyType) {
let c = || {
let _val = std::ptr::addr_of!(r.field);
let _val = r.third_field;
};
drop(c);
eprintln!("before dropping");
}
fn main() {
test(MyType {
field: Default::default(),
other_field: NoisyDrop,
third_field: Vec::new(),
});
}
```
Of course this is a breaking change for the same reason that doing field capturing in the first place was a breaking change. Packed fields are relatively rare and depending on drop order is relatively rare, so I don't expect this to have much impact, but it's hard to be sure and even a crater run will only tell us so much.
Also see the [nomination comment](https://github.com/rust-lang/rust/pull/115315#issuecomment-1702807825).
Cc `@rust-lang/wg-rfc-2229` `@ehuss`
Make useless_ptr_null_checks smarter about some std functions
This teaches the `useless_ptr_null_checks` lint that some std functions can't ever return null pointers, because they need to point to valid data, get references as input, etc.
This is achieved by introducing an `#[rustc_never_returns_null_ptr]` attribute and adding it to these std functions (gated behind bootstrap `cfg_attr`).
Later on, the attribute could maybe be used to tell LLVM that the returned pointer is never null. I don't expect much impact of that though, as the functions are pretty shallow and usually the input data is already never null.
Follow-up of PR #113657Fixes#114442
Fallback effects even if types also fallback
`||` is short circuiting, so if we do ty/int var fallback, we *don't* do effect fallback 😸
r? `@fee1-dead` or `@oli-obk`
Fixes#115791Fixes#115842
Improve invalid let expression handling
- Move all of the checks for valid let expression positions to parsing.
- Add a field to ExprKind::Let in AST/HIR to mark whether it's in a valid location.
- Suppress some later errors and MIR construction for invalid let expressions.
- Fix a (drop) scope issue that was also responsible for #104172.
Fixes#104172Fixes#104868
treat host effect params as erased in codegen
This fixes the changes brought to codegen tests when effect params are added to libcore, by not attempting to monomorphize functions that get the host param by being `const fn`.
r? `@oli-obk`
some inspect improvements
split from #114810 because I still want to experiment a bunch with that PR and these changes are self-contained.
r? `@compiler-errors`
Rework `no_coverage` to `coverage(off)`
As discussed at the tail of https://github.com/rust-lang/rust/issues/84605 this replaces the `no_coverage` attribute with a `coverage` attribute that takes sub-parameters (currently `off` and `on`) to control the coverage instrumentation.
Allows future-proofing for things like `coverage(off, reason="Tested live", issue="#12345")` or similar.
Bubble up opaque <eq> opaque operations instead of picking an order
In case we are in `Bubble` mode (meaning every opaque type that is defined in the current crate is treated as if it were in its defining scope), we don't try to register an opaque type as the hidden type of another opaque type, but instead bubble up an obligation to equate them at the query caller site. Usually that means we have a `DefiningAnchor::Bind` and thus can reliably figure out whether an opaque type is in its defining scope. Where we can't, we'll error out, so the default is sound.
With this change we start using `AliasTyEq` predicates in the old solver, too.
fixes https://github.com/rust-lang/rust/issues/108498
But also regresses `tests/ui/impl-trait/anon_scope_creep.rs`. Our use of `Bubble` for `check_opaque_type_well_formed` is going to keep biting us.
r? `@lcnr` `@compiler-errors`
Allow redirecting subprocess stdout to our stderr etc. (redux)
This is the code from #88561, tidied up, including review suggestions, and with the for-testing-only CI commit removed. FCP for the API completed in #88561.
I have made a new MR to facilitate review. The discussion there is very cluttered and the branch is full of changes (in many cases as a result of changes to other Rust stdlib APIs since then). Assuming this MR is approvedl we should close that one.
### Reviewer doing a de novo review
Just code review these four commits.. FCP discussion starts here: https://github.com/rust-lang/rust/pull/88561#issuecomment-1640527595
Portability tests: you can see that this branch works on Windows too by looking at the CI results in #88561, which has the same code changes as this branch but with an additional "DO NOT MERGE" commit to make the Windows tests run.
### Reviewer doing an incremental review from some version of #88561
Review the new commits since your last review. I haven't force pushed the branch there.
git diff the two branches (eg `git diff 176886197d6..0842b69c219`). You'll see that the only difference is in gitlab CI files. You can also see that *this* MR doesn't touch those files.
Implement Step for ascii::Char
This allows iterating over ranges of `ascii::Char`, similarly to ranges of `char`.
Note that `ascii::Char` is still unstable, tracked in #110998.
docs: improve std::fs::read doc
#### What does this PR do
1. Rephrase a confusing sentence in the document of `std::fs::read()`
-----
Closes#114432
cc `@Dexus0` `@saethlin`
Inline functions called from `add_coverage`
This removes quite a bit of indirection and duplicated code related to getting the `FunctionCoverage`.
CC `@Zalathar`
Adapt table sizes to the contents
This is an implementation of https://github.com/rust-lang/compiler-team/issues/666
The objective of this PR is to permit the rmeta format to accommodate larger crates that need offsets larger than a `u32` can store without compromising performance for crates that do not need such range. The second commit is a number of tiny optimization opportunities I noticed while looking at perf recordings of the first commit.
The rmeta tables need to have fixed-size elements to permit lazy random access. But the size only needs to be fixed _per table_, not per element type. This PR adds another `usize` to the table header which indicates the table element size. As each element of a table is set, we keep track of the widest encoded table value, then don't bother encoding all the unused trailing bytes on each value. When decoding table elements, we copy them to a full-width array if they are not already full-width.
`LazyArray` needs some special treatment. Most other values that are encoded in tables are indexes or offsets, and those tend to be small so we get to drop a lot of zero bytes off the end. But `LazyArray` encodes _two_ small values in a fixed-width table element: A position of the table and the length of the table. The treatment described above could trim zero bytes off the table length, but any nonzero length shields the position bytes from the optimization. To improve this, we interleave the bytes of position and length. This change is responsible for about half of the crate metadata win on many crates.
Fixes https://github.com/rust-lang/rust/issues/112934 (probably)
Fixes https://github.com/rust-lang/rust/issues/103607
Always add LC_BUILD_VERSION for metadata object files
As of Xcode 15 Apple's linker has become a bit more strict about the warnings it produces. One of those new warnings requires all valid Mach-O object files in an archive to have a LC_BUILD_VERSION load command:
```
ld: warning: no platform load command found in 'ARCHIVE[arm64][2106](lib.rmeta)', assuming: iOS-simulator
```
This was already being done for Mac Catalyst so this change expands this logic to include it for all Apple platforms. I filed this behavior change as FB12546320 and was told it was the new intentional behavior.
Add note that Vec::as_mut_ptr() does not materialize a reference to the internal buffer
See discussion on https://github.com/thomcc/rust-typed-arena/issues/62 and [t-opsem](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/is.20this.20typed_arena.20code.20sound.20under.20stacked.2Ftree.20borrows.3F)
This method already does the correct thing here, but it is worth guaranteeing that it does so it can be used more freely in unsafe code without having to worry about potential Stacked/Tree Borrows violations. This moves one more unsafe usage pattern from the "very likely sound but technically not fully defined" box into "definitely sound", and currently our surface area of the latter is woefully small.
I'm not sure how best to word this, opening this PR as a way to start discussion.
Avoid duplicate `large_assignments` lints
By checking for overlapping spans.
This PR does the "reduce noisiness" task in #83518.
r? `@oli-obk` who added E-mentor and E-help-wanted and wrote the initial code.
(The fix itself is in dc82736677. The two commits before that are just small refactorings.)
Move a local to the `#if` block where it is used
For other cases (LLVM < 17), this was complaining under `-Wall`:
```
warning: llvm-wrapper/PassWrapper.cpp: In function ‘void LLVMRustPrintTargetCPUs(LLVMTargetMachineRef, const char*)’:
warning: llvm-wrapper/PassWrapper.cpp:311:26: warning: unused variable ‘MCInfo’ [-Wunused-variable]
warning: 311 | const MCSubtargetInfo *MCInfo = Target->getMCSubtargetInfo();
warning: | ^~~~~~
```
Go into more detail about panicking in drop.
This patch was sitting around in my drafts. I don't recall the motivation, but I think it was someone expressing confusion over “will likely abort” (since, in fact, a panicking drop _not_ caused by dropping while panicking will predictably _not_ abort).
I hope that the new text will leave people well-informed about why not to panic and when it is reasonable to panic.
Treat `StatementKind::Coverage` as completely opaque for SMIR purposes
Coverage statements in MIR are heavily tied to internal details of the coverage implementation that are likely to change, and are unlikely to be useful to third-party tools for the foreseeable future.
Allow explicit `#[repr(Rust)]`
This is identical to no `repr()` at all. For `Rust, packed` and `Rust, align(x)`, it should be the same as no `Rust` at all (as, afaik, `#[repr(align(16))]` uses the Rust ABI.)
The main use case for this is being able to explicitly say "I want to use the Rust ABI" in very very rare circumstances where the first obvious choice would be the C ABI yet is undesirable, which is already possible with functions as `extern "Rust"`. This would be useful for silencing https://github.com/rust-lang/rust-clippy/pull/11253. It's also more consistent with `extern`.
The lack of this also tripped me up a bit when I was new to Rust, as I expected this to be possible.
Fix races conditions with `SyntaxContext` decoding
This changes `SyntaxContext` decoding to work with concurrent decoding. The `remapped_ctxts` field now only stores `SyntaxContext` which have completed decoding, while the new `decoding` and `local_in_progress` keeps track of `SyntaxContext`s which are in process of being decoding and on which threads.
This fixes 2 issues with the current implementation. It can return an `SyntaxContext` which contains dummy data if another thread starts decoding before the first one has completely finished. Multiple threads could also allocate multiple `SyntaxContext`s for the same `raw_id`.
Suggest mutable borrow on read only for-loop that should be mutable
```
error[E0596]: cannot borrow `*test` as mutable, as it is behind a `&` reference
--> $DIR/suggest-mut-iterator.rs:22:9
|
LL | for test in &tests {
| ------ this iterator yields `&` references
LL | test.add(2);
| ^^^^ `test` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: use a mutable iterator instead
|
LL | for test in &mut tests {
| +++
```
Fix#114311.
Parse unnamed fields and anonymous structs or unions (no-recovery)
It is part of #114782 which implements #49804. Only parse anonymous structs or unions in struct field definition positions.
r? `@petrochenkov`
