…ting spaces

Closes rust-lang#84434. Closes rust-lang#82329.

…is a NOP

refactor StyledBuffer

Refactors StyledBuffer `text` and `styles` fields content into StyledChar and touches some other stuff.

…nt, r=petrochenkov

Handle pretty printing of `else if let` clauses without ICEing

When pretty printing the HIR of `if ... {} else if let ... {}` clauses, this displays it the `else if let` part as `match` it gets desugared to, the same way normal `if let` statements are currently displayed, instead of ICEing.

```rust
pub fn main() {
    if true {
        // 1
    } else if let a = 1 {
        // 2
    } else {
        // 3
    }
}
```

now gets desugared (via `rustc -Zunpretty=hir,typed src/x.rs`) to:

```rust
#[prelude_import]
use ::std::prelude::rust_2015::*;
#[macro_use]
extern crate std;
pub fn main() ({
                   (if (true as bool)
                       ({
                            // 1
                        } as
                           ()) else {match (1 as i32) {
                                         a => {
                                             // 2
                                         }
                                         _ => {
                                             // 3
                                         }
                                     }} as ())
                    } as ())
```

For comparison, this code gets HIR prettyprinted the same way before and after this change:

```rust
pub fn main() {
    if let a = 1 {
        // 2
    } else {
        // 3
    }
}
```
turns into
```rust
#[prelude_import]
use ::std::prelude::rust_2015::*;
#[macro_use]
extern crate std;
pub fn main() ({
                   (match (1 as i32) {
                        a => {
                            // 2
                        }
                        _ => {
                            // 3
                        }
                    } as ())
               } as ())
```

This closes rust-lang#82329. It closes rust-lang#84434 as well, due to having the same root cause.

Tweak trait not `use`d suggestion

Fix rust-lang#84272. Follow up to rust-lang#83667.

Add suggestion to "use break" when attempting to implicit-break a loop

Fixes rust-lang#84114

Inline most raw socket, fd and handle conversions

Now that file descriptor types on Unix have niches, it is advantageous for user libraries which provide file descriptor wrappers (e.g. `Socket` from socket2) to store a `File` internally instead of a `RawFd`, so that the niche can be taken advantage of. However, doing so will currently result in worse performance as `IntoRawFd`, `FromRawFd` and `AsRawFd` are not inlined. This change adds `#[inline]` to those methods on std types that wrap file descriptors, handles or sockets.

…ince, r=m-ou-se

Fix 'const-stable since' of reverse_bits

This fixes the const_stable `since` of `reverse_bits` for the signed and unsigned integer types. The previous value was incorrect, as it pointed to an older version where `reverse_bits` hadn't been stabilized yet.

`reverse_bits` was const-stable from the start, as can be seen from:

https://doc.rust-lang.org/1.37.0/std/primitive.u32.html#method.reverse_bits
https://doc.rust-lang.org/1.37.0/std/primitive.i32.html#method.reverse_bits

Always reject `const fn` in `trait` during parsing.

'const fn' in trait are rejected in the AST:
https://github.com/rust-lang/rust/blob/b78c0d8a4d5af91a4a55d029293e3ecb879ec142/compiler/rustc_ast_passes/src/ast_validation.rs#L1411
So this feature gate check is a NOP and we can just remove it.

The src/test/ui/feature-gates/feature-gate-min_const_fn.rs and src/test/ui/feature-gates/feature-gate-const_fn.rs tests ensure that we still reject `const fn` in `trait`

Cc rust-lang#84510
r? ``@oli-obk``

…n514

Fix typo  in report_unsed_assign

The function was called `report_unsed_assign`, which I assume is a typo, considering the rest of the file.
This replaces `report_unsed_assign` with `report_unused_assign`.