Signed-off-by: chloefeal <188809157+chloefeal@users.noreply.github.com>

… region vids

Fix typos

This PR focuses on correcting typos and improving clarity in documentation files. Thank you.

Some random region tweaks

Remove a redundant function and add an assertion that I think is useful

…r-errors

Skip parenthesis if `.` makes statement boundary unambiguous

There is a rule in the parser that statements and match-arms never end in front of a `.` or `?` token (except when the `.` is really `..` or `..=` or `...`). So some of the leading subexpressions that need parentheses inserted when followed by some other operator like `-` or `+`, do not need parentheses when followed by `.` or `?`.

Example:

```rust
fn main() {
    loop {}.to_string() + "";
    match () {
        _ => loop {}.to_string() + "",
    };
}
```

`-Zunpretty=expanded` before:

```console
#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
fn main() {
    (loop {}).to_string() + "";
    match () { _ => (loop {}).to_string() + "", };
}
```

After:

```console
#![feature(prelude_import)]
#[prelude_import]
use std::prelude::rust_2021::*;
#[macro_use]
extern crate std;
fn main() {
    loop {}.to_string() + "";
    match () { _ => loop {}.to_string() + "", };
}
```

…rors

Skip parenthesis around tuple struct field calls

The pretty-printer previously did not distinguish between named vs unnamed fields when printing a function call containing a struct field. It would print the call as `(self.fun)()` for a named field which is correct, and `(self.0)()` for an unnamed field which is redundant.

This PR changes function calls of tuple struct fields to print without parens.

**Before:**

```rust
struct Tuple(fn());

fn main() {
    let tuple = Tuple(|| {});
    (tuple.0)();
}
```

**After:**

```rust
struct Tuple(fn());

fn main() {
    let tuple = Tuple(|| {});
    tuple.0();
}
```