Filter global bounds from ParamEnv again.
This PR adds back the filtering of global bounds from ParamEnv as a temporary solution for #50825.
<details>
Long term, the fix seems like it should be changing the priority in `candidate_should_be_dropped_in_favor_of` so that (global) where clauses aren't considered as highly.
a722296b6e/src/librustc/traits/select.rs (L2017-L2022)
</details>
r? @nikomatsakis
stabilize opt-level={s,z}
closes#35784closes#47651
### Rationale
Since the lastest LLVM upgrade rustc / LLVM does more agressive loop unrolling. This results in increased binary size of embedded / no_std programs: a hundreds of bytes increase, or about a 7x increase, in the case of the smallest Cortex-M binary cf. #49260.
As we are shooting for embedded Rust on stable it would be great to also provide a way to optimize for size (which is pretty important for embedded applications that target resource constrained devices) on stable.
Also this has been baking in nightly for a long time.
r? @alexcrichton which team has to sign off this?
rustc: introduce {ast,hir}::AnonConst to consolidate so-called "embedded constants".
Previously, constants in array lengths and enum variant discriminants were "merely an expression", and had no separate ID for, e.g. type-checking or const-eval, instead reusing the expression's.
That complicated code working with bodies, because such constants were the only special case where the "owner" of the body wasn't the HIR parent, but rather the same node as the body itself.
Also, if the body happened to be a closure, we had no way to allocate a `DefId` for both the constant *and* the closure, leading to *several* bugs (mostly ICEs where type errors were expected).
This PR rectifies the situation by adding another (`{ast,hir}::AnonConst`) node around every such constant. Also, const generics are expected to rely on the new `AnonConst` nodes, as well (cc @varkor).
* fixes#48838
* fixes#50600
* fixes#50688
* fixes#50689
* obsoletes #50623
r? @nikomatsakis
Consider this a down payment on #50723. To recap, an `Applicability`
enum was recently (#50204) added, to convey to Rustfix and other tools
whether we think it's OK for them to blindly apply the suggestion, or
whether to prompt a human for guidance (because the suggestion might
contain placeholders that we can't infer, or because we think it has a
sufficiently high probability of being wrong even though it's—
presumably—right often enough to be worth emitting in the first place).
When a suggestion is marked as `MaybeIncorrect`, we try to use comments
to indicate precisely why (although there are a few places where we just
say `// speculative` because the present author's subjective judgement
balked at the idea that the suggestion has no false positives).
The `run-rustfix` directive is opporunistically set on some relevant UI
tests (and a couple tests that were in the `test/ui/suggestions`
directory, even if the suggestions didn't originate in librustc or
libsyntax). This is less trivial than it sounds, because a surprising
number of test files aren't equipped to be tested as fixed even when
they contain successfully fixable errors, because, e.g., there are more,
not-directly-related errors after fixing. Some test files need an
attribute or underscore to avoid unused warnings tripping up the "fixed
code is still producing diagnostics" check despite the fixes being
correct; this is an interesting contrast-to/inconsistency-with the
behavior of UI tests (which secretly pass `-A unused`), a behavior which
we probably ought to resolve one way or the other (filed issue #50926).
A few suggestion labels are reworded (e.g., to avoid phrasing it as a
question, which which is discouraged by the style guidelines listed in
`.span_suggestion`'s doc-comment).
Rollup of 8 pull requests
Successful merges:
- #50531 (Cleanup uses of TypeIdHasher and replace them with StableHasher)
- #50819 (Fix potential divide by zero)
- #50827 (Update LLVM to 56c931901cfb85cd6f7ed44c7d7520a8de1edf97)
- #50829 (CheckLoopVisitor: also visit break expressions)
- #50854 (in which the unused shorthand field pattern debacle/saga continues)
- #50858 (Reorder description for snippets in rustdoc documentation)
- #50883 (Fix warning when building stage0 libcore)
- #50889 (Update clippy)
Failed merges:
in which the unused shorthand field pattern debacle/saga continues
In e4b1a79 (#47922), we corrected erroneous suggestions for unused
shorthand field pattern bindings, suggesting `field: _` where the
previous suggestion of `_field` wouldn't even have compiled
(#47390). Soon, it was revealed that this was insufficient (#50303), and
the fix was extended to references, slices, &c. (#50327) But even this
proved inadequate, as the erroneous suggestions were still being issued
for patterns in local (`let`) bindings (#50804). Here, we yank the
shorthand-detection and variable/node registration code into a new
common function that can be called while visiting both match arms and
`let` bindings.
Resolves#50804.
r? @estebank
Add lint checks for unused loop labels
Previously no warning was generated when a loop label was written out but never used (i.e. in a `break` or `continue` statement):
```rust
fn main() {
'unused_label: loop {}
}
```
would compile without complaint.
This fix introduces `-W unused_loop_label`, which generates the following warning message for the above snippet:
```
warning: unused loop label
--> main.rs:2:5
|
2 | 'unused_label: loop {}
| ^^^^^^^^^^^^^
|
= note: #[warn(unused_loop_label)] on by default
```
Fixes: #50751.
Turn deprecation lint `legacy_imports` into a hard error
Closes https://github.com/rust-lang/rust/issues/38260
The lint was introduced in Dec 2016, then made deny-by-default in Jun 2017 when crater run found 0 regressions caused by it.
This lint requires some not entirely trivial amount of import resolution logic that (surprisingly or not) interacts with `feature(use_extern_macros)` (https://github.com/rust-lang/rust/issues/35896), so it would be desirable to remove it before stabilizing `use_extern_macros`.
In particular, this PR fixes the failing example in https://github.com/rust-lang/rust/issues/50725 (but not the whole issue, `use std::panic::{self}` still can cause other undesirable errors when `use_extern_macros` is enabled).
Emit noalias on &mut parameters by default
This used to be disabled due to LLVM bugs in the handling of
noalias information in conjunction with unwinding. However,
according to #31681 all known LLVM bugs have been fixed by
LLVM 6.0, so it's probably time to reenable this optimization.
-Z no-mutable-noalias is left as an escape-hatch to debug problems
suspected to stem from this change.
Implement [T]::align_to
Note that this PR deviates from what is accepted by RFC slightly by making `align_offset` to return an offset in elements, rather than bytes. This is necessary to sanely support `[T]::align_to` and also simply makes more sense™. The caveat is that trying to align a pointer of ZST is now an equivalent to `is_aligned` check, rather than anything else (as no number of ZST elements will align a misaligned ZST pointer).
It also implements the `align_to` slightly differently than proposed in the RFC to properly handle cases where size of T and U aren’t co-prime.
Furthermore, a promise is made that the slice containing `U`s will be as large as possible (contrary to the RFC) – otherwise the function is quite useless.
The implementation uses quite a few underhanded tricks and takes advantage of the fact that alignment is a power-of-two quite heavily to optimise the machine code down to something that results in as few known-expensive instructions as possible. Currently calling `ptr.align_offset` with an unknown-at-compile-time `align` results in code that has just a single "expensive" modulo operation; the rest is "cheap" arithmetic and bitwise ops.
cc https://github.com/rust-lang/rust/issues/44488 @oli-obk
As mentioned in the commit message for align_offset, many thanks go to Chris McDonald.
Make the `const_err` lint `deny`-by-default
At best these things are runtime panics (debug mode) or overflows (release mode). More likely they are public constants that are unused in the crate declaring them.
This is not a breaking change, as dependencies won't break and root crates can `#![warn(const_err)]`, though I don't know why anyone would do that.
Implement edition hygiene for keywords
Determine "keywordness" of an identifier in its hygienic context.
cc https://github.com/rust-lang/rust/pull/49611
I've resurrected `proc` as an Edition-2015-only keyword for testing purposes, but it should probably be buried again. EDIT: `proc` is removed again.
