fix: panic with wrapping/unwrapping result return type assists
With the `wrap_return_type_in_result` assist, the following code results in a panic (note the lack of a semicolon):
```rust
fn foo(num: i32) -> $0i32 {
return num
}
=>
thread 'handlers::wrap_return_type_in_result::tests::wrap_return_in_tail_position' panicked at crates/syntax/src/ted.rs:137:41:
called `Option::unwrap()` on a `None` value
```
I think this is because it first walks the body expression to change any `return` expressions and then walks all tail expressions, resulting in the `return num` being changed twice since it is both a `return` and in tail position. This can also happen when a `match` is in tail position and `return` is used in a branch for example. Not really sure how big of an issue this is in practice though since this seems to be the only case that is impacted and can be reduced to just `num` instead of `return num`.
This also occurs with the `unwrap_result_return_type` assist but panics with the following instead:
```
thread 'handlers::unwrap_result_return_type::tests::wrap_return_in_tail_position' panicked at /rustc/3223b0b5e8dadda3f76c3fd1a8d6c5addc09599e/library/alloc/src/string.rs:1766:29:
assertion failed: self.is_char_boundary(n)
```
minor : Deunwrap convert_comment_block and desugar_doc_comment
Closes subtask 13 of #15398 . I still don't know a more idiomatic way for the for loops I added, any suggestion would make me happy.
Although it doesn't panic now, further changes to how we recover from incomplete syntax
may cause this assist to panic. To mitigate this a test case has been added.
feat: Bool to enum assist
This adds the `bool_to_enum` assist, which converts the type of boolean local variables, fields, constants and statics to a new `enum` type, making it easier to distinguish the meaning of `true` and `false` by renaming the variants.
Closes#14779
Field shorthand overwritten in promote local to const assist
Currently, running `promote_local_to_const` on the following:
```rust
struct Foo {
bar: usize,
}
fn main() {
let $0bar = 0;
let foo = Foo { bar };
}
```
Results in:
```rust
struct Foo {
bar: usize,
}
fn main() {
const BAR: usize = 0;
let foo = Foo { BAR };
}
```
But instead should be something like:
```rust
struct Foo {
bar: usize,
}
fn main() {
const BAR: usize = 0;
let foo = Foo { bar: BAR };
}
```
Bind unused parameter assistant
This PR introduces a new **Bind unused parameter assistant**.
While we do have a QuickFix from `rustc` (prefixing the parameter with an underscore), it's sometimes more convenient to suppress the warning using the following approach:
```rust
fn some_function(unused: i32) {}
```
->
```rust
fn some_function(unused: i32) {
let _ = unused;
}
```
