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situations like module-relative uses, we can do more accurate redundant import checking.
fixes #117448
For example unnecessary imports in std::prelude that can be eliminated:
```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```
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Implement intrinsics with fallback bodies
fixes #93145 (though we can port many more intrinsics)
cc #63585
The way this works is that the backend logic for generating custom code for intrinsics has been made fallible. The only failure path is "this intrinsic is unknown". The `Instance` (that was `InstanceDef::Intrinsic`) then gets converted to `InstanceDef::Item`, which represents the fallback body. A regular function call to that body is then codegenned. This is currently implemented for
* codegen_ssa (so llvm and gcc)
* codegen_cranelift
other backends will need to adjust, but they can just keep doing what they were doing if they prefer (though adding new intrinsics to the compiler will then require them to implement them, instead of getting the fallback body).
cc `@scottmcm` `@WaffleLapkin`
### todo
* [ ] miri support
* [x] default intrinsic name to name of function instead of requiring it to be specified in attribute
* [x] make sure that the bodies are always available (must be collected for metadata)
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Use generic `NonZero` internally.
Tracking issue: https://github.com/rust-lang/rust/issues/120257
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Merge `impl_polarity` and `impl_trait_ref` queries
Hopefully this is perf neutral. I want to finish https://github.com/rust-lang/rust/pull/120835 and stop using the HIR in `coherent_trait`, which should then give us a perf improvement.
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hir: Make sure all `HirId`s have corresponding HIR `Node`s
And then remove `tcx.opt_hir_node(hir_id)` in favor of `tcx.hir_node(hir_id)`.
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resolve: Unload speculatively resolved crates before freezing cstore
Name resolution sometimes loads additional crates to improve diagnostics (e.g. suggest imports).
Not all of these diagnostics result in errors, sometimes they are just warnings, like in #117772.
If additional crates loaded speculatively stay and gets listed by things like `query crates` then they may produce further errors like duplicated lang items, because lang items from speculatively loaded crates are as good as from non-speculatively loaded crates.
They can probably do things like adding unintended impls from speculatively loaded crates to method resolution as well.
The extra crates will also get into the crate's metadata as legitimate dependencies.
In this PR I remove the speculative crates from cstore when name resolution is finished and cstore is frozen.
This is better than e.g. filtering away speculative crates in `query crates` because things like `DefId`s referring to these crates and leaking to later compilation stages can produce ICEs much easier, allowing to detect them.
The unloading could potentially be skipped if any errors were reported (to allow using `DefId`s from speculatively loaded crates for recovery), but I didn't do it in this PR because I haven't seen such cases of recovery. We can reconsider later if any relevant ICEs are reported.
Unblocks https://github.com/rust-lang/rust/pull/117772.
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replace `track_errors` usages with bubbling up `ErrorGuaranteed`
more of the same as https://github.com/rust-lang/rust/pull/117449 (removing `track_errors`)
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This cuts the average bytes/relative span from 3.5 to 3.2 on libcore,
ultimately saving ~400kb of data.
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Avoid specialization in the metadata serialization code
With the exception of a perf-only specialization for byte slices and byte vectors.
This uses the same trick of introducing a new trait and having the Encodable and Decodable derives add a bound to it as used for TyEncoder/TyDecoder. The new code is clearer about which encoder/decoder uses which impl and it reduces the dependency of rustc on specialization, making it easier to remove support for specialization entirely or turn it into a construct that is only allowed for perf optimizations if we decide to do this.
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Rollup of 8 pull requests
Successful merges:
- #119151 (Hide foreign `#[doc(hidden)]` paths in import suggestions)
- #119350 (Imply outlives-bounds on lazy type aliases)
- #119354 (Make `negative_bounds` internal & fix some of its issues)
- #119506 (Use `resolutions(()).effective_visiblities` to avoid cycle errors in `report_object_error`)
- #119554 (Fix scoping for let chains in match guards)
- #119563 (Check yield terminator's resume type in borrowck)
- #119589 (cstore: Remove unnecessary locking from `CrateMetadata`)
- #119622 (never patterns: Document behavior of never patterns with macros-by-example)
r? `@ghost`
`@rustbot` modify labels: rollup
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query stable
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Report I/O errors from rmeta encoding with emit_fatal
https://github.com/rust-lang/rust/issues/119456 reminded me that I never did systematic testing to provoke the out-of-disk ICEs so I grepped through a recent crater run (https://github.com/rust-lang/rust/pull/119440#issuecomment-1873393963) for more out-of-disk ICEs on current master and yep there's 2 in there.
So I finally cooked up a way to provoke for these crashes. I wrote a little `cdylib` crate that has a `#[no_mangle] pub extern "C" fn write` which occasionally reports `ENOSPC`, and prints a backtrace when it does.
<details><summary><strong>code for the dylib</strong></summary>
<p>
```rust
// cargo add libc rand backtrace
use rand::Rng;
#[no_mangle]
pub extern "C" fn write(
fd: libc::c_int,
buf: *const libc::c_void,
count: libc::size_t,
) -> libc::ssize_t {
if fd > 2 && rand::thread_rng().gen::<u8>() == 0 {
let mut count = 0;
backtrace::trace(|frame| {
backtrace::resolve_frame(frame, |symbol| {
if let Some(name) = symbol.name() {
if count > 3 {
eprintln!("{}", name);
}
}
count += 1;
});
true
});
unsafe {
*libc::__errno_location() = libc::ENOSPC;
}
return -1;
} else {
unsafe {
let res =
libc::syscall(libc::SYS_write, fd as usize, buf as usize, count as usize) as isize;
if res < 0 {
*libc::__errno_location() = -res as i32;
-1
} else {
res
}
}
}
}
```
</p>
</details>
Then `LD_PRELOAD` that dylib and repeatedly build a big project until it ICEs, such as with this:
```bash
while true; do
cargo clean
LD_PRELOAD=/home/ben/evil/target/release/libevil.so cargo +stage1 check 2> errors
if grep "thread 'rustc' panicked" errors; then
break
fi
done
```
My "big project" for testing was an otherwise-empty project with `cargo add axum`.
Before this PR, the above procedure finds a crash in between 1 and 15 minutes. With this PR, I have not found a crash in 30 minutes, and I'll be leaving this to run overnight (starting now). (A night has now passed, no crashes were found)
I believe the problem is that even though since https://github.com/rust-lang/rust/pull/117301 we correctly check `FileEncoder` for errors on all paths, we use `emit_err`, so there is a window of time between the call to `emit_err` and the full error reporting where rustc believes it has emitted a valid rmeta file and will permit Cargo to launch a build for a dependent crate. Changing these calls to `emit_fatal` closes that window.
I think there are a number of other cases where `emit_err` has been used instead of the more-correct `emit_fatal` such as https://github.com/rust-lang/rust/blob/e51e98dde6a60637b6a71b8105245b629ac3fe77/compiler/rustc_codegen_ssa/src/back/write.rs#L542 but unlike rmeta encoding I am not aware of those cases of those causing problems.
r? ``@WaffleLapkin``
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Spans are now stored in a more compact form which cuts down on at least
1 byte per span (indirect/direct encoding) and at most 3 bytes per span
(indirect/direct encoding, context byte, length byte). As a result,
libcore metadata shrinks by 1.5MB.
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Only store StableCrateId once in DefPathTable.
https://github.com/rust-lang/rust/pull/119238 made me think of this.
cc `@Mark-Simulacrum`
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Support encoding spans with relative offsets
The relative offset is often smaller than the absolute offset, and with
the LEB128 encoding, this ends up cutting the overall metadata size
considerably (~1.5 megabytes on libcore). We can support both relative
and absolute encodings essentially for free since we already take a full
byte to differentiate between direct and indirect encodings (so an extra
variant is quite cheap).
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The relative offset is often smaller than the absolute offset, and with
the LEB128 encoding, this ends up cutting the overall metadata size
considerably (~1.5 megabytes on libcore). We can support both relative
and absolute encodings essentially for free since we already take a full
byte to differentiate between direct and indirect encodings (so an extra
variant is quite cheap).
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Make closures carry their own ClosureKind
Right now, we use the "`movability`" field of `hir::Closure` to distinguish a closure and a coroutine. This is paired together with the `CoroutineKind`, which is located not in the `hir::Closure`, but the `hir::Body`. This is strange and redundant.
This PR introduces `ClosureKind` with two variants -- `Closure` and `Coroutine`, which is put into `hir::Closure`. The `CoroutineKind` is thus removed from `hir::Body`, and `Option<Movability>` no longer needs to be a stand-in for "is this a closure or a coroutine".
r? eholk
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r=compiler-errors
Remove `DiagCtxt` API duplication
`DiagCtxt` defines the internal API for creating and emitting diagnostics: methods like `struct_err`, `struct_span_warn`, `note`, `create_fatal`, `emit_bug`. There are over 50 methods.
Some of these methods are then duplicated across several other types: `Session`, `ParseSess`, `Parser`, `ExtCtxt`, and `MirBorrowckCtxt`. `Session` duplicates the most, though half the ones it does are unused. Each duplicated method just calls forward to the corresponding method in `DiagCtxt`. So this duplication exists to (in the best case) shorten chains like `ecx.tcx.sess.parse_sess.dcx.emit_err()` to `ecx.emit_err()`.
This API duplication is ugly and has been bugging me for a while. And it's inconsistent: there's no real logic about which methods are duplicated, and the use of `#[rustc_lint_diagnostic]` and `#[track_caller]` attributes vary across the duplicates.
This PR removes the duplicated API methods and makes all diagnostic creation and emission go through `DiagCtxt`. It also adds `dcx` getter methods to several types to shorten chains. This approach scales *much* better than API duplication; indeed, the PR adds `dcx()` to numerous types that didn't have API duplication: `TyCtxt`, `LoweringCtxt`, `ConstCx`, `FnCtxt`, `TypeErrCtxt`, `InferCtxt`, `CrateLoader`, `CheckAttrVisitor`, and `Resolver`. These result in a lot of changes from `foo.tcx.sess.emit_err()` to `foo.dcx().emit_err()`. (You could do this with more types, but it gets into diminishing returns territory for types that don't emit many diagnostics.)
After all these changes, some call sites are more verbose, some are less verbose, and many are the same. The total number of lines is reduced, mostly because of the removed API duplication. And consistency is increased, because calls to `emit_err` and friends are always preceded with `.dcx()` or `.dcx`.
r? `@compiler-errors`
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Improve coding efficiency for RawDefId
This copies the scheme already used for LazyArray, cutting a couple hundred kilobytes from libcore's metadata.
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r=cjgillot
Unify SourceFile::name_hash and StableSourceFileId
This PR adapts the existing `StableSourceFileId` type so that it can be used instead of the `name_hash` field of `SourceFile`. This simplifies a few things that were kind of duplicated before.
The PR should also fix issues https://github.com/rust-lang/rust/issues/112700 and https://github.com/rust-lang/rust/issues/115835, but I was not able to reproduce these issues in a regression test. As far as I can tell, the root cause of these issues is that the id of the originating crate is not hashed in the `HashStable` impl of `Span` and thus cache entries that should have been considered invalidated were loaded. After this PR, the `stable_id` field of `SourceFile` includes information about the originating crate, so that ICE should not occur anymore.
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Remove metadata decoding DefPathHash cache
My expectation is that this cache is largely useless. Decoding a DefPathHash from metadata is essentially a pair of memory loads - there's no heavyweight processing involved. Caching it behind a HashMap just adds extra cost and incurs hashing overheads for the indices.
Based on https://github.com/rust-lang/rust/pull/119238.
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Skip duplicate stable crate ID encoding into metadata
Instead, we store just the local crate hash as a bare u64. On decoding,
we recombine it with the crate's stable crate ID stored separately in
metadata. The end result is that we save ~8 bytes/DefIndex in metadata
size.
One key detail here is that we no longer distinguish in encoded metadata
between present and non-present DefPathHashes. It used to be highly
likely we could distinguish as we used DefPathHash::default(), an
all-zero representation. However in theory even that is fallible as
nothing strictly prevents the StableCrateId from being zero. In review it
was pointed out that we should never have a missing hash for a DefIndex anyway,
so this shouldn't matter.
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