Explain compile-time vs run-time difference in env!() error message
This PR is clarifying error message of `env!()` based on this user question: https://users.rust-lang.org/t/environment-variable-out-dir-is-undefined/90067
It makes it clear that `env!()` is for env variables defined at compile-time. There's special-case help text for common Cargo build script variables.
I've also rearranged the code to avoid allocating error message on the happy path when the env var is defined.
Point error span at Some constructor argument when trait resolution fails
This is a follow up to #108254 and #106477 which extends error span refinement to handle a case which I mistakenly believed was handled in #106477. The goal is to refine the error span depicted below:
```rs
trait Fancy {}
impl <T> Fancy for Option<T> where T: Iterator {}
fn want_fancy<F>(f: F) where F: Fancy {}
fn example() {
want_fancy(Some(5));
// (BEFORE) ^^^^^^^ `{integer}` is not an iterator
// (AFTER) ^ `{integer}` is not an iterator
}
```
I had used a (slightly more complex) example as an illustrative example in #108254 , but hadn't actually turned it into a test, because I had (incorrectly) believed at the time it was covered by existing behavior. It turns out that `Some` is slightly "special" in that it resolves differently from the other `enum` constructors I had tried, and therefore this test was actually broken.
I've now updated the tests to include this example, and fixed the code to correctly resolve the `Some` constructor so that the span of the error is reduced.
Revert stabilization of `#![feature(target_feature_11)]`
This reverts #99767 due to the presence of bugs #108645 and #108646.
cc `@joshtriplett`
cc tracking issue #69098
r? `@ghost`
Rollup of 5 pull requests
Successful merges:
- #108516 (Restrict `#[rustc_box]` to `Box::new` calls)
- #108575 (Erase **all** regions when probing for associated types on ambiguity in astconv)
- #108585 (Run compiler test suite in parallel on Fuchsia)
- #108606 (Add test case for mismatched open/close delims)
- #108609 (Highlight whole expression for E0599)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Highlight whole expression for E0599
Fixes#108603
This adds a secondary label to highlight the whole expression leading to the error. It also prevents empty labels being recognised as 'unexpected' by compiletest - otherwise, tests with NOTE annotations would pick up empty labels.
`@rustbot` label +A-diagnostics
Restrict `#[rustc_box]` to `Box::new` calls
Currently, `#[rustc_box]` can be applied to any call expression with a single argument. This PR only allows it to be applied to calls to `Box::new`
Add support for QNX Neutrino to standard library
This change:
- adds standard library support for QNX Neutrino (7.1).
- upgrades `libc` to version `0.2.139` which supports QNX Neutrino
`@gh-tr`
⚠️ Backtraces on QNX require https://github.com/rust-lang/backtrace-rs/pull/507 which is not yet merged! (But everything else works without these changes) ⚠️
Tested mainly with a x86_64 virtual machine (see qnx-nto.md) and partially with an aarch64 hardware (some tests fail due to constrained resources).
Merge two different equality specialization traits in `core`
Arrays and slices each had their own version of this, without a matching set of `impl`s.
Merge them into one (still-`pub(crate)`) `cmp::BytewiseEq` trait, so we can stop doing all these things twice.
And that means that the `[T]::eq` → `memcmp` specialization picks up a bunch of types where that previously only worked for arrays, so examples like <https://rust.godbolt.org/z/KjsG8MGGT> will use it now instead of emitting loops.
r? the8472
Rollup of 7 pull requests
Successful merges:
- #108143 (rustdoc: search by macro when query ends with `!`)
- #108394 (Make `x doc --open` work on every book)
- #108427 (Recover from for-else and while-else)
- #108462 (Fix `VecDeque::append` capacity overflow for ZSTs)
- #108568 (Make associated_item_def_ids for traits use an unstable option to also return associated types for RPITITs)
- #108604 (Add regression test for #107280)
- #108605 (Add regression test for #105821)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Recover from for-else and while-else
This recovers from attempts at writing for-else or while-else loops, which might help users coming from e.g. Python.
```rs
for _ in 0..0 {
// ...
} else {
// ...
}
```
Combined with trying to store it in a let binding, the current diagnostic can be a bit confusing. It mentions let-else and suggests wrapping the loop in parentheses, which the user probably doesn't want. let-else doesn't make sense for `for` and `while` loops, as they are of type `()` (which already is an irrefutable pattern and doesn't need let-else).
<details>
<summary>Current diagnostic</summary>
```rs
error: right curly brace `}` before `else` in a `let...else` statement not allowed
--> src/main.rs:4:5
|
4 | } else {
| ^
|
help: wrap the expression in parentheses
|
2 ~ let _x = (for _ in 0..0 {
3 |
4 ~ }) else {
|
```
</details>
Some questions:
- Can the wording for the error message be improved? Would "for...else loops are not allowed" fit better?
- Should we be more "conservative" in case we want to support this in the future (i.e. say "for...else loops are **currently** not allowed/supported")?
- Is there a better way than storing a `&'static str` for the loop type? It is used for substituting the placeholder in the locale file (since it can emit either `for...else` or `while...else`). Maybe there is an enum I could use that I couldn't find
Name LLVM anonymous constants by a hash of their contents
This makes the names stable between different versions of a crate unlike the `AllocId` naming, making LLVM IR comparisons with `llvm-diff` more practical.
Add `Option::as_`(`mut_`)`slice`
This adds the following functions:
* `Option<T>::as_slice(&self) -> &[T]`
* `Option<T>::as_mut_slice(&mut self) -> &[T]`
The `as_slice` and `as_mut_slice_mut` functions benefit from an optimization that makes them completely branch-free. ~~Unfortunately, this optimization is not available on by-value Options, therefore the `into_slice` implementations use the plain `match` + `slice::from_ref` approach.~~
Note that the optimization's soundness hinges on the fact that either the niche optimization makes the offset of the `Some(_)` contents zero or the mempory layout of `Option<T>` is equal to that of `Option<MaybeUninit<T>>`.
The idea has been discussed on [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Option.3A.3Aas_slice). Notably the idea for the `as_slice_mut` and `into_slice´ methods came from `@cuviper` and `@Sp00ph` hardened the optimization against niche-optimized Options.
The [rust playground](https://play.rust-lang.org/?version=nightly&mode=release&edition=2021&gist=74f8e4239a19f454c183aaf7b4a969e0) shows that the generated assembly of the optimized method is basically only a copy while the naive method generates code containing a `test dx, dx` on x86_64.
---
EDIT from reviewer: ACP is https://github.com/rust-lang/libs-team/issues/150
Only look for param in item's generics if it actually comes from generics
Record whether a `hir::GenericParam` comes from an item's generics, or from a `for<...>` binder. Then, only look for the param in `object_lifetime_default` if it actually comes from the item's generics.
Fixes#108177
This adds the following functions:
* `Option<T>::as_slice(&self) -> &[T]`
* `Option<T>::as_slice_mut(&mut self) -> &[T]`
The `as_slice` and `as_slice_mut` functions benefit from an
optimization that makes them completely branch-free.
Note that the optimization's soundness hinges on the fact that either
the niche optimization makes the offset of the `Some(_)` contents zero
or the mempory layout of `Option<T>` is equal to that of
`Option<MaybeUninit<T>>`.
Stabilize `#![feature(target_feature_11)]`
## Stabilization report
### Summary
Allows for safe functions to be marked with `#[target_feature]` attributes.
Functions marked with `#[target_feature]` are generally considered as unsafe functions: they are unsafe to call, cannot be assigned to safe function pointers, and don't implement the `Fn*` traits.
However, calling them from other `#[target_feature]` functions with a superset of features is safe.
```rust
// Demonstration function
#[target_feature(enable = "avx2")]
fn avx2() {}
fn foo() {
// Calling `avx2` here is unsafe, as we must ensure
// that AVX is available first.
unsafe {
avx2();
}
}
#[target_feature(enable = "avx2")]
fn bar() {
// Calling `avx2` here is safe.
avx2();
}
```
### Test cases
Tests for this feature can be found in [`src/test/ui/rfcs/rfc-2396-target_feature-11/`](b67ba9ba20/src/test/ui/rfcs/rfc-2396-target_feature-11/).
### Edge cases
- https://github.com/rust-lang/rust/issues/73631
Closures defined inside functions marked with `#[target_feature]` inherit the target features of their parent function. They can still be assigned to safe function pointers and implement the appropriate `Fn*` traits.
```rust
#[target_feature(enable = "avx2")]
fn qux() {
let my_closure = || avx2(); // this call to `avx2` is safe
let f: fn() = my_closure;
}
```
This means that in order to call a function with `#[target_feature]`, you must show that the target-feature is available while the function executes *and* for as long as whatever may escape from that function lives.
### Documentation
- Reference: https://github.com/rust-lang/reference/pull/1181
---
cc tracking issue #69098
r? `@ghost`
