This check was previously only performed on functions not function pointers.

Co-authored-by: Folkert <[email protected]>

Signed-off-by: onur-ozkan <[email protected]>

These are common pitfalls for beginners, so I think it's worth
making the subtleties more visible.

…eatures

Add missing error annotations and .stderr file

Acknowledge comments

…iler-errors

Check ABI target compatibility for function pointers

Tracking issue: rust-lang#130260
Related tracking issue: rust-lang#87678

Compatibility of an ABI for a target was previously only performed on function definitions and `extern` blocks. This PR adds it also to function pointers to be consistent.

This might have broken some of the `tests/ui/` depending on the platform, so a try run seems like a good idea.

Also this might break existing code, because we now emit extra errors. Does this require a crater run?

# Example
```rust
// build with: --target=x86_64-unknown-linux-gnu

// These raise E0570
extern "thiscall" fn foo() {}
extern "thiscall" { fn bar() }

// This did not raise any error
fn baz(f: extern "thiscall" fn()) { f() }
```

# Open Questions
* [x] Should this report a future incompatibility warning like rust-lang#87678 ?
* [ ] Is this the best place to perform the check?

…c, r=Mark-Simulacrum

make `Step` doc-comments more clear

Aiming to improve complicated `Step` documentation. Once we merge this, I will update [this page](https://rustc-dev-guide.rust-lang.org/building/bootstrapping/how-bootstrap-does-it.html?highlight=Step#synopsis-of--step) too.

…lcnr

Don't assume traits used as type are trait objs in 2021 edition

Fixes rust-lang#127548

When you use a trait as a type, the compiler automatically assumes you meant to use a trait object, which is not always the case.
This PR fixes the bug where you don't need a trait object, so the error message was changed to:
```
error[E0782]: expected a type, found a trait
```
Also fixes some ICEs:
Fixes rust-lang#120241
Fixes rust-lang#120482
Fixes rust-lang#125512

…y-instability-lint-for-clippy, r=xFrednet

Handle `clippy` cases of `rustc::potential_query_instability` lint

This PR removes `#![allow(rustc::potential_query_instability)]` line from [`src/tools/clippy/clippy_lints/src/lib.rs`](https://github.com/rust-lang/rust/blob/master/src/tools/clippy/clippy_lints/src/lib.rs#L30) and converts `FxHash{Map,Set}` types into `FxIndex{Map,Set}` to suppress lint errors.

A somewhat tracking issue: rust-lang#84447

…=Mark-Simulacrum

More clearly document Stdin::read_line

These are common pitfalls for beginners, so I think it's worth making the subtleties more visible.

…ccepted-features, r=jieyouxu

Emit an error for unstable attributes that reference already stable features

Closes rust-lang#129814

merge const_ipv4 / const_ipv6 feature gate into 'ip' feature gate

rust-lang#76205 has been closed a while ago, but there are still some functions that reference it. Those functions are all unstable *and* const-unstable. There's no good reason to use a separate feature gate for their const-stability, so this PR moves their const-stability under the same gate as their regular stability, and therefore removes the remaining references to rust-lang#76205.

…tgross35

remove const_cow_is_borrowed feature gate

The two functions guarded by this are still unstable, and there's no reason to require a separate feature gate for their const-ness -- we can just have `cow_is_borrowed` cover both kinds of stability.

Cc rust-lang#65143