Avoid a branch on key being local for queries that use the same local and extern providers
Currently based on https://github.com/rust-lang/rust/pull/85810 as it slightly conflicts with it. Only the last two commits are new.
Prevent duplicate caller bounds candidates by exposing default substs in Unevaluated
Fixes https://github.com/rust-lang/rust/issues/89334
The changes introduced in https://github.com/rust-lang/rust/pull/87280 allowed for "duplicate" caller bounds candidates to be assembled that only differed in their default substs having been "exposed" or not and resulted in an ambiguity error during trait selection. To fix this we expose the defaults substs during the creation of the ParamEnv.
r? `@lcnr`
Add -Z no-unique-section-names to reduce ELF header bloat.
This change adds a new compiler flag that can help reduce the size of ELF binaries that contain many functions.
By default, when enabling function sections (which is the default for most targets), the LLVM backend will generate different section names for each function. For example, a function `func` would generate a section called `.text.func`. Normally this is fine because the linker will merge all those sections into a single one in the binary. However, starting with [LLVM 12](https://github.com/llvm/llvm-project/commit/ee5d1a04), the backend will also generate unique section names for exception handling, resulting in thousands of `.gcc_except_table.*` sections ending up in the final binary because some linkers like LLD don't currently merge or strip these EH sections (see discussion [here](https://reviews.llvm.org/D83655)). This can bloat the ELF headers and string table significantly in binaries that contain many functions.
The new option is analogous to Clang's `-fno-unique-section-names`, and instructs LLVM to generate the same `.text` and `.gcc_except_table` section for each function, resulting in a smaller final binary.
The motivation to add this new option was because we have a binary that ended up with so many ELF sections (over 65,000) that it broke some existing ELF tools, which couldn't handle so many sections.
Here's our old binary:
```
$ readelf --sections old.elf | head -1
There are 71746 section headers, starting at offset 0x2a246508:
$ readelf --sections old.elf | grep shstrtab
[71742] .shstrtab STRTAB 0000000000000000 2977204c ad44bb 00 0 0 1
```
That's an 11MB+ string table. Here's the new binary using this option:
```
$ readelf --sections new.elf | head -1
There are 43 section headers, starting at offset 0x29143ca8:
$ readelf --sections new.elf | grep shstrtab
[40] .shstrtab STRTAB 0000000000000000 29143acc 0001db 00 0 0 1
```
The whole binary size went down by over 20MB, which is quite significant.
enable `i8mm` target feature on aarch64 and arm
As in https://github.com/rust-lang/stdarch/issues/1233, `i8mm` needs to be turned on to support the implementation of `vmmla` and `vusmmla`neon instructions in stdarch.
r? ``@Amanieu``
Rollup of 4 pull requests
Successful merges:
- #89889 (Use the "nice E0277 errors"[1] for `!Send` `impl Future` from foreign crate)
- #90127 (Do not mention a reexported item if it's private)
- #90143 (tidy: Remove submodules from edition exception list)
- #90238 (Add alias for guillaume.gomez@huawei.com)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Do not mention a reexported item if it's private
Fixes#90113
The _actual_ regression was introduced in #73652, then #88838 made it worse. This fixes the issue by not counting such an import as a candidate.
Use the "nice E0277 errors"[1] for `!Send` `impl Future` from foreign crate
Partly address #78543 by making the error quieter.
We don't have access to the `typeck` tables from foreign crates, so we
used to completely skip the new code when checking foreign crates. Now,
we carry on and don't provide as nice output (we don't clarify *what* is
making the `Future: !Send`), but at least we no longer emit a sea of
derived obligations in the output.
[1]: https://blog.rust-lang.org/inside-rust/2019/10/11/AsyncAwait-Not-Send-Error-Improvements.html
r? `@tmandry`
Cleanup LLVM multi-threading checks
The support for runtime multi-threading was removed from LLVM. Calls to
`LLVMStartMultithreaded` became no-ops equivalent to checking if LLVM
was compiled with support for threads http://reviews.llvm.org/D4216.
Build the query vtable directly.
Continuation of https://github.com/rust-lang/rust/pull/89978.
This shrinks the query interface and attempts to reduce the amount of function pointer calls.
Partly address #78543 by making the error quieter.
We don't have access to the `typeck` tables from foreign crates, so we
used to completely skip the new code when checking foreign crates. Now,
we carry on and don't provide as nice output (we don't clarify *what* is
making the `Future: !Send`), but at least we no longer emit a sea of
derived obligations in the output.
[1]: https://blog.rust-lang.org/inside-rust/2019/10/11/AsyncAwait-Not-Send-Error-Improvements.html
Fix ICE when forgetting to `Box` a parameter to a `Self::func` call
Closes#90213 .
Assuming we can get the `DefId` of the receiver causes an ICE if the receiver is `Self`. We can just avoid doing this though.
Specialize HashStable for [u8] slices
Particularly for ctfe-stress-4, the hashing of byte slices as part of the
MIR Allocation is quite hot. Previously, we were falling back on byte-by-byte
copying of the slice into the SipHash buffer (64 bytes long) before hashing a 64
byte chunk, and then doing that again and again; now we use the dedicated byte-slice write.
Update the minimum external LLVM to 12
With this change, we'll have stable support for LLVM 12 and 13.
For reference, the previous increase to LLVM 10 was #83387,
and this replaces the pending increase to LLVM 11 in #90062.
r? `@nagisa` `@nikic`
Particularly for ctfe-stress-4, the hashing of byte slices as part of the
MIR Allocation is quite hot. Previously, we were falling back on byte-by-byte
copying of the slice into the SipHash buffer (64 bytes long) before hashing a 64
byte chunk, and then doing that again and again.
This should hopefully be an improvement for that code.
Rollup of 5 pull requests
Successful merges:
- #85833 (Scrape code examples from examples/ directory for Rustdoc)
- #88041 (Make all proc-macro back-compat lints deny-by-default)
- #89829 (Consider types appearing in const expressions to be invariant)
- #90168 (Reset qualifs when a storage of a local ends)
- #90198 (Add caveat about changing parallelism and function call overhead)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Reset qualifs when a storage of a local ends
Reset qualifs when a storage of a local ends to ensure that the local qualifs
are affected by the state from previous loop iterations only if the local is
kept alive.
The change should be forward compatible with a stricter handling of indirect
assignments, since storage dead invalidates all existing pointers to the local.
Consider types appearing in const expressions to be invariant
This is an approach to fix#80977.
Currently, a type parameter which is only used in a constant expression is considered bivariant and will trigger error E0392 *"parameter T is never used"*.
Here is a short example:
```rust
pub trait Foo {
const N: usize;
}
struct Bar<T: Foo>([u8; T::N])
where [(); T::N]:;
```
([playgound](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2015&gist=b51a272853f75925e72efc1597478aa5))
While it is possible to silence this error by adding a `PhantomData<T>` field, I think the better solution would be to make `T` invariant.
This would be analogous to the invariance constraints added for associated types.
However, I'm quite new to the compiler and unsure whether this is the right approach.
r? ``@varkor`` (since you authored #60058)
Make all proc-macro back-compat lints deny-by-default
The affected crates have had plenty of time to update.
By keeping these as lints rather than making them hard errors,
we ensure that downstream crates will still be able to compile,
even if they transitive depend on broken versions of the affected
crates.
This should hopefully discourage anyone from writing any
new code which relies on the backwards-compatibility behavior.
Implement coherence checks for negative trait impls
The main purpose of this PR is to be able to [move Error trait to core](https://github.com/rust-lang/project-error-handling/issues/3).
This feature is necessary to handle the following from impl on box.
```rust
impl From<&str> for Box<dyn Error> { ... }
```
Without having negative traits affect coherence moving the error trait into `core` and moving that `From` impl to `alloc` will cause the from impl to no longer compiler because of a potential future incompatibility. The compiler indicates that `&str` _could_ introduce an `Error` impl in the future, and thus prevents the `From` impl in `alloc` that would cause overlap with `From<E: Error> for Box<dyn Error>`. Adding `impl !Error for &str {}` with the negative trait coherence feature will disable this error by encoding a stability guarantee that `&str` will never implement `Error`, making the `From` impl compile.
We would have this in `alloc`:
```rust
impl From<&str> for Box<dyn Error> {} // A
impl<E> From<E> for Box<dyn Error> where E: Error {} // B
```
and this in `core`:
```rust
trait Error {}
impl !Error for &str {}
```
r? `@nikomatsakis`
This PR was built on top of `@yaahc` PR #85764.
Language team proposal: to https://github.com/rust-lang/lang-team/issues/96
Do not depend on the stored value when trying to cache on disk.
Having different criteria for loading and saving of query results can lead to saved results that may never be loaded.
Since the on-disk cache is discarded as soon as a compilation error is issued, there should not be any need for an exclusion mecanism based on errors.
As a result, the possibility to condition the storage on the value itself does not appear useful.
to ensure that the local qualifs are affected by the state from previous
loop iterations only if the local is kept alive.
The change should be forward compatible with a stricter handling of
indirect assignments, since storage dead invalidates all existing
pointers to the local.
Implement -Z location-detail flag
This PR implements the `-Z location-detail` flag as described in https://github.com/rust-lang/rfcs/pull/2091 .
`-Z location-detail=val` controls what location details are tracked when using `caller_location`. This allows users to control what location details are printed as part of panic messages, by allowing them to exclude any combination of filenames, line numbers, and column numbers. This option is intended to provide users with a way to mitigate the size impact of `#[track_caller]`.
Some measurements of the savings of this approach on an embedded binary can be found here: https://github.com/rust-lang/rust/issues/70579#issuecomment-942556822 .
Closes#70580 (unless people want to leave that open as a place for discussion of further improvements).
This is my first real PR to rust, so any help correcting mistakes / understanding side effects / improving my tests is appreciated :)
I have one question: RFC 2091 specified this as a debugging option (I think that is what -Z implies?). Does that mean this can never be stabilized without a separate MCP? If so, do I need to submit an MCP now, or is the initial RFC specifying this option sufficient for this to be merged as is, and then an MCP would be needed for eventual stabilization?
add feature flag for `type_changing_struct_update`
This implements the PR0 part of the mentoring notes within #86618.
overrides the previous inactive #86646 pr.
r? ```@nikomatsakis```
Report fatal lexer errors in `--cfg` command line arguments
Fixes#89358. The erroneous behavior was apparently introduced by `@Mark-Simulacrum` in a678e31911; the idea is to silence individual parser errors and instead emit one catch-all error message after parsing. However, for the example in #89358, a fatal lexer error is created here:
edebf77e00/compiler/rustc_parse/src/lexer/mod.rs (L340-L349)
This fatal error aborts the compilation, and so the call to `new_parser_from_source_str()` never returns and the catch-all error message is never emitted. I have therefore changed the `SilentEmitter` to silence only non-fatal errors; with my changes, for the rustc invocation described in #89358:
```sh
rustc --cfg "abc\""
```
I get the following output:
```
error[E0765]: unterminated double quote string
|
= note: this error occurred on the command line: `--cfg=abc"`
```
This doesn't work properly yet, we would probably need to implement an
`assembly_neg_candidates` and consider things like `T: !AB` as `T: !A`
|| `T: !B`
