…aren't likely to appear in for head or match arm

When encountering match arm (pat if expr) => {}, recover and suggest removing parentheses. Fix rust-lang#100825.

Use the same approach used for match arm patterns.

…rget features outside an unsafe block

…unction with target features outside an unsafe block

Tweak parsing recovery of enums, for exprs and match arm patterns

Tweak recovery of `for (pat in expr) {}` for more accurate spans.

When encountering `match` arm `(pat if expr) => {}`, recover and suggest removing parentheses. Fix rust-lang#100825.

When encountering malformed enums, try more localized per-variant parse recovery.

Move parser recovery tests to subdirectory.

Name explicit registers in conflict register errors for inline assembly

…r=compiler-errors

Add `never_patterns` feature gate

This PR adds the feature gate and most basic parsing for the experimental `never_patterns` feature. See the tracking issue (rust-lang#118155) for details on the experiment.

`@scottmcm` has agreed to be my lang-team liaison for this experiment.

…cuviper

also add is_empty to const raw slices

We have this on mutable raw slices but not const raw slices, which makes little sense.

Cc rust-lang#71146

…tebank

Pretty print `Fn<(..., ...)>` trait refs with parentheses (almost) always

It's almost always better, at least in diagnostics, to print `Fn(i32, u32)` instead of `Fn<(i32, u32)>`.

Related to but doesn't fix rust-lang#118225. That needs a separate fix.

…tures, r=est31

Print list of missing target features when calling a function with target features outside an unsafe block

Fixes rust-lang#108680

Supersedes rust-lang#109710. I used the same wording for the messages, but the implementation is different.

r? `@est31`