Fix into() cast paren check precedence

As discussed in #47699 the logic for determining if an expression needs
parenthesis when suggesting an `.into()` cast is incorrect. Two broken
examples from nightly are:

```
error[E0308]: mismatched types
 --> main.rs:4:10
  |
4 |     test(foo as i8);
  |          ^^^^^^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
  |
4 |     test(foo as i8.into());
  |
```

```
error[E0308]: mismatched types
 --> main.rs:4:10
  |
4 |     test(*foo);
  |          ^^^^ expected i32, found i8
help: you can cast an `i8` to `i32`, which will sign-extend the source value
  |
4 |     test(*foo.into());
  |
```

As suggested by @petrochenkov switch the precedence check to
PREC_POSTFIX. This catches both `as` and unary operators. Fixes #47699.

0 files changed, 0 insertions, 0 deletions