Add future incompatibility lint for `array.into_iter()`
This is for #65819. This lint warns when calling `into_iter` on an array directly. That's because today the method call resolves to `<&[T] as IntoIterator>::into_iter` but that would change when adding `IntoIterator` impls for arrays. This problem is discussed in detail in #65819.
We still haven't decided how to proceed exactly, but it seems like adding a lint is a good idea regardless?
Also: this is the first time I implement a lint, so there are probably a lot of things I can improve. I used a different strategy than @scottmcm describes [here](https://github.com/rust-lang/rust/pull/65819#issuecomment-548667847) since I already started implementing this before they commented.
### TODO
- [x] Decide if we want this lint -> apparently [we want](https://github.com/rust-lang/rust/pull/65819#issuecomment-548964818)
- [x] Open a lint-tracking-issue and add the correct issue number in the code -> https://github.com/rust-lang/rust/issues/66145
A scheme for more macro-matcher friendly pre-expansion gating
Pre-expansion gating will now avoid gating macro matchers that did not result in `Success(...)`. That is, the following is now OK despite `box 42` being a valid `expr` and that form being pre-expansion gated:
```rust
macro_rules! m {
($e:expr) => { 0 }; // This fails on the input below due to `, foo`.
(box $e:expr, foo) => { 1 }; // Successful matcher, we should get `2`.
}
fn main() {
assert_eq!(1, m!(box 42, foo));
}
```
Closes https://github.com/rust-lang/rust/issues/65846.
r? @petrochenkov
cc @Mark-Simulacrum
syntax: ABI-oblivious grammar
This PR has the following effects:
1. `extern $lit` is now legal where `$lit:literal` and `$lit` is substituted for a string literal.
2. `extern "abi_that_does_not_exist"` is now *syntactically* legal whereas before, the set of ABI strings was hard-coded into the grammar of the language. With this PR, the set of ABIs are instead validated and translated during lowering. That seems more appropriate.
3. `ast::FloatTy` is now distinct from `rustc_target::abi::FloatTy`. The former is used substantially more and the translation between them is only necessary in a single place.
4. As a result of 2-3, libsyntax no longer depends on librustc_target, which should improve pipe-lining somewhat.
cc @rust-lang/lang -- the points 1-2 slightly change the definition of the language but in a way which seems consistent with our general principles (in particular wrt. the discussions of turning things into semantic errors). I expect this to be uncontroversial but it's worth letting y'all know. :)
r? @varkor
Use structured suggestions for missing associated items
When encountering an `impl` that is missing associated items required by its `trait`, use structured suggestions at an appropriate place in the `impl`.
We also sever syntax's dependency on rustc_target as a result.
This should slightly improve pipe-lining.
Moreover, some cleanup is done in related code.
Miri: Refactor to_scalar_ptr out of existence
`to_scalar_ptr` is somewhat subtle as it just throws away the 2nd component of a `ScalarPair` if there is one -- without any check if this is truly a pointer or so. And indeed we used it wrong on two occasions!
So I fixed those two, and then refactored things such that everyone calls `ref_to_mplace` instead (which they did anyway, I just moved up the calls), which is the only place that should interpret a `ScalarPair` as a wide ptr -- and it checks the type first. Thus we can remove `to_scalar_ptr` and `to_meta`.
r? @oli-obk
Fixed PhantomData markers in Arc and Rc
Include owned internal structs in `PhantomData` markers in `Arc` (`PhantomData<T>` => `PhantomData<ArcInner<T>>`) and `Rc` (`PhantomData<T>` => `PhantomData<RcBox<T>>`).
Improve std:🧵:Result documentation
Thanks to @dtolnay for pointing out the different premise of the contents of the `Err` variant in `std:🧵:Result` WRT normal error handling.
improve from_raw_parts docs
Triggered by https://github.com/rust-lang/rfcs/pull/2806. Hopefully this helps clarify that joining slices across allocations is not possible in Rust currently.
r? @Centril
Do not require extra LLVM backends for `x.py test` to pass
For long time our testing passed with a partially built LLVM
```
[llvm]
targets = "X86;ARM"
```
, a [recent PR](https://github.com/rust-lang/rust/pull/65809) changed that.
Improve uninit/zeroed lint
* Also warn when creating a raw pointer with a NULL vtable.
* Also identify `MaybeUninit::uninit().assume_init()` and `MaybeUninit::zeroed().assume_init()` as dangerous.
Optimize long-linker-command-line test
Replace O(n^3) text matching with inexpensive hash set lookups.
On my machine this reduces the total runtime of complete
run-make-fulldeps suite from roughly 75 seconds to 45 seconds.
gate rustc_on_unimplemented under rustc_attrs
Move `rustc_on_implemented` from the `on_implemented` gate to `rustc_attrs` as it is internal.
Closes#29628
r? @varkor
Cheaper doc comments
This PR implements the idea from #60935: represent doc comments more cheaply, rather than converting them into `#[doc="..."]` attribute form. Unlike #60936 (which is about coalescing doc comments to reduce their number), this approach does not have any backwards compatibility concerns, and it eliminates about 80-90% of the current cost of doc comments (as estimated using the numbers in #60930, which eliminated the cost of doc comments entirely by treating them as normal comments).
r? @petrochenkov
Fix promotion in a `const` when projections are present
Resolves#65727.
This marks the entire local as "needs promotion" when only a projection of that local appears in a promotable context. This should only affect promotion in a `const` or `static`, not in a `fn` or `const fn`, which is handled in `promote_consts.rs`.
r? @eddyb
The old const-checker conservatively reset qualifs when
`IsNotPromotable` was in the return place. Unfortunately, named
variables have `IsNotPromotable`, so this could cause promotion to fail.
This should work now.
The former was cleared from `qualifs_in_return_place`, and the latter
was never checked. `QUALIF_ERROR_BIT` no longer corresponds to a real
`Qualif`, however.
We no longer compare the results of
`promote_consts::validate_candidates` with
`checker.promotion_candidates`, and `promote_consts` becomes the
canonical source for determining promotability.
As we might want to add `IntoIterator` impls for arrays in the future,
and since that introduces a breaking change, this lint warns and
suggests using `iter()` instead (which is shorter and more explicit).
`AttrKind` is a new type with two variants, `Normal` and `DocComment`. It's a
big performance win (over 10% in some cases) because `DocComment` lets doc
comments (which are common) be represented very cheaply.
`Attribute` gets some new helper methods to ease the transition:
- `has_name()`: check if the attribute name matches a single `Symbol`; for
`DocComment` variants it succeeds if the symbol is `sym::doc`.
- `is_doc_comment()`: check if it has a `DocComment` kind.
- `{get,unwrap}_normal_item()`: extract the item from a `Normal` variant;
panic otherwise.
Fixes#60935.
