suggest removing `impl` in generic trait bound position
rustc already does this recovery in type param position (`<T: impl Trait>` -> `<T: Trait>`).
This PR also adds that suggestion in trait bound position (e.g. `where T: impl Trait` or `trait Trait { type Assoc: impl Trait; }`)
Make `get_return_block()` return `Some` only for HIR nodes in body
Fixes#114918
The issue occurred while compiling the following input:
```rust
fn uwu() -> [(); { () }] {
loop {}
}
```
It was caused by the code below trying to suggest a missing return type which resulted in a const eval cycle: 1bd043098e/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs (L68-L75)
The root cause was `get_return_block()` returning an `Fn` node for a node in the return type (i.e. the second `()` in the return type `[(); { () }]` of the input) although it is supposed to do so only for nodes that lie in the body of the function and return `None` otherwise (at least as per my understanding).
The PR fixes the issue by fixing this behaviour of `get_return_block()`.
parser: not insert dummy field in struct
Fixes#114636
This PR eliminates the dummy field, initially introduced in #113999, thereby enabling unrestricted use of `ident.unwrap()`. A side effect of this action is that we can only report the error of the first macro invocation field within the struct node.
An alternative solution might be giving a virtual name to the macro, but it appears more complex.(https://github.com/rust-lang/rust/issues/114636#issuecomment-1670228715). Furthermore, if you think https://github.com/rust-lang/rust/issues/114636#issuecomment-1670228715 is a better solution, feel free to close this PR.
Make SIGSEGV handler emit nicer backtraces
This annotates the code heavily with comments to explain what is going on, for the benefit of other compiler contributors. The backtrace also emits appropriate comments to clarify, to a programmer who may not know why a bunch of file paths and hexadecimal blather was just dumped into stderr, what is going on. Finally, it detects cycles and uses their regularity to avoid repeating a bunch of text. The previous backtraces we were emitting was extremely unfriendly, potentially confusing, and often alarming, and this makes things almost "nice".
We can't necessarily make them much nicer than this, because a signal handler must use "signal-safe" functions. This precludes conveniences like dynamic allocations. Fortunately, Rust's stdlib has allocation-free formatting, but it may hinder integrating this error with our localization middleware, as I wasn't able to clearly ascertain, at a glance, whether there was a zero-alloc path through it.
r? `@Nilstrieb`
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
Previously, the test code would emit E0615, thus revealing the existence
of private methods that the programmer probably does not care about.
Now it ignores their existence instead, producing error E0609 (no field).
The motivating example is:
```rust
let x = std::rc::Rc::new(());
x.inner;
```
which would previously mention the private method `Rc::inner()`, even
though `Rc<T>` intentionally has no public methods so that it can be a
transparent smart pointer for any `T`.
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.
Rollup of 6 pull requests
Successful merges:
- #111580 (Don't ICE on layout computation failure)
- #114923 (doc: update lld-flavor ref)
- #115174 (tests: add test for #67992)
- #115187 (Add new interface to smir)
- #115300 (Tweaks and improvements on SMIR around generics_of and predicates_of)
- #115340 (some more is_zst that should be is_1zst)
r? `@ghost`
`@rustbot` modify labels: rollup
Tweaks and improvements on SMIR around generics_of and predicates_of
r? `@oli-obk`
This allows an API like the following ...
```rust
let trait_decls = stable_mir::all_trait_decls().iter().map(|trait_def| {
let trait_decl = stable_mir::trait_decl(trait_def);
let generics = trait_decl.generics_of();
let predicates = trait_decl.predicates_of().predicates;
```
I didn't like that much `trait_def.trait_decl()` which is it possible but adding a method to a def_id that loads up a whole trait definition looks backwards to me.
Update Clippy
r? `@oli-obk` Assigning you, because something broke with ui_test:
```
tests/ui/crashes/ice-7272.rs FAILED:
command: "<unknown>"
A bug in `ui_test` occurred: called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
full stderr:
```
(and that 103 times)
Thought I would ping you, before starting to investigate. Maybe you know what's going on.
Remove conditional use of `Sharded` from query state
`Sharded` is already a zero cost abstraction, so it shouldn't affect the performance of the single thread compiler if LLVM does its job.
r? `@cjgillot`
fix some issues around ZST handling
This fixes two bugs:
- We used to entirely skip enum variants like `B([u16; 0], !)`, even failing to properly align the enum! Honoring the alignment of uninhabited variants is important for the same reason that we must reserve space for their fields -- see [here](https://github.com/rust-lang/rust/issues/49298#issuecomment-380615281) for why.
- ~~We uses to reject `repr(transparent)` on `struct MyType([u16; 0])`, which is weird because a one-field struct should always be allowed to be transparent around that field.~~ (moved to separate PR)
I also found two places in the layout code that did something special for ZST without explaining why, and removing those special cases doesn't seem to have any effect except for reordering some zero-sized fields which shouldn't be an issue... maybe PR CI will explain why those cases were needed, or maybe they became obsolete at some point.
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.
