…rget features outside an unsafe block

When encountering a bare assignment in a let-chain, suggest turning the
assignment into a `let` expression or an equality check.

```
error: expected expression, found `let` statement
  --> $DIR/bad-if-let-suggestion.rs:5:8
   |
LL |     if let x = 1 && i = 2 {}
   |        ^^^^^^^^^
   |
   = note: only supported directly in conditions of `if` and `while` expressions
help: you might have meant to continue the let-chain
   |
LL |     if let x = 1 && let i = 2 {}
   |                     +++
help: you might have meant to compare for equality
   |
LL |     if let x = 1 && i == 2 {}
   |                        +
```

…unction with target features outside an unsafe block

They're only used for HTML, so it makes more sense for them to live
their.

x.py does not support specify multiple --target keywords. The targets must be specified comma separated.

…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.

…r-errors

Suggest `let` or `==` on typo'd let-chain

When encountering a bare assignment in a let-chain, suggest turning the
assignment into a `let` expression or an equality check.

```
error: expected expression, found `let` statement
  --> $DIR/bad-if-let-suggestion.rs:5:8
   |
LL |     if let x = 1 && i = 2 {}
   |        ^^^^^^^^^
   |
   = note: only supported directly in conditions of `if` and `while` expressions
help: you might have meant to continue the let-chain
   |
LL |     if let x = 1 && let i = 2 {}
   |                     +++
help: you might have meant to compare for equality
   |
LL |     if let x = 1 && i == 2 {}
   |                        +
```

…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

…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`

…r-errors,cjgillot

ConstProp: Correctly remove const if unknown value assigned to it.

Closes rust-lang#118328

The problematic sequence of MIR is:

```rust
          _1 = const 0_usize;
          _1 = const _; // This is an associated constant we can't know before monomorphization.
          _0 = _1;
```

1. When `ConstProp::visit_assign` happens on `_1 = const 0_usize;`, it records that `0x0usize` is the value for `_1`.
2. Next `visit_assign` happens on `_1 = const _;`. Because the rvalue `.has_param()`, it can't be const evaled.
3. Finaly, `visit_assign` happens on `_0 = _1;`. Here it would think the value of `_1` was `0x0usize` from step 1.

The solution is to remove consts when checking the RValue fails, as they may have contained values that should now be invalidated, as that local was overwritten.

This should probably be back-ported to beta. Stable is more iffy, as it's gone unidentified since 1.70, so I only think it's worthwhile if there's another reason for a 1.74.1 release anyway.

…aumeGomez

rustdoc: Move `AssocItemRender` and `RenderMode` to `html::render`.

They're only used for HTML, so it makes more sense for them to live their.

Update nto-qnx.md

x.py does not support specifying multiple `--target` keywords. The targets must be specified comma separated.

Error:
`error: the argument '--target <TARGET>' cannot be used multiple times`