invalid_value lint: fix help text
Now that we also warn about `MaybUninit::uninit().assume_init()`, just telling people "use `MaybeUninit`" isn't always sufficient. And anyway this seems like an important enough point to mention it here.
Have tidy ensure that we document all `unsafe` blocks in libcore
cc @rust-lang/libs
I documented a few and added ignore flags on the other files. We can incrementally document the files, but won't regress any files this way.
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.
