It is bitset semantically --- many categorical things can be true about
a reference at the same time.
In parciular, a reference can be a "test" and a "write" at the same
time.
# Overview
Extracting a match arm value that has type unit into a function, when a
comma already follows the match arm value, results in an invalid (syntax
error) semicolon added between the newly generated function's generated
call and the comma.
# Example
Running this extraction
```rust
fn main() {
match () {
_ => $0()$0,
};
}
```
would lead to
```rust
fn main() {
match () {
_ => fun_name();,
};
}
fn fun_name() {
}
```
# Issue / Fix details
This happens because when there is no comma, rust-analyzer would simply
add the comma and wouldn't even try to evaluate whether it needs to add
a semicolon. But when the comma is there, it proceeds to evaluate
whether it needs to add a semicolon and it looks like the evaluation
logic erroneously ignores the possibility that we're in a match arm.
IIUC it never makes sense to add a semicolon when we're extracting from
a match arm value, so I've adjusted the logic to always decide against
adding a semicolon when we're in a match arm
Feat: extracted method from trait impl is placed in existing impl
**Before**
https://user-images.githubusercontent.com/1759192/183872883-3b0eafd2-d1dc-440e-9e66-38e3372f8b64.mp4
**After**
https://user-images.githubusercontent.com/1759192/183875769-87f34c7d-52f0-4dfc-9766-f591ee738ebb.mp4
Previously, when triggering a method extraction from within an impl trait block, then this would always create a new impl block for
the struct, even if there already is one. Now, if there is already an existing trait-less impl block, then it'll put the extracted method in there.
**Caveats**:
- It currently requires the target impl block to be non-empty. This limitation is because the current architecture takes a `node_to_insert_after` as reference for where to insert the extracted function. An empty impl block doesn't have such a reference node, since it's empty. It seems that supporting this requires a much larger and more complex change.
- This is my first contribution in rust, so apologies for any beginner mistakes.
Previously, when triggering a method extraction from within a trait
impl block, then this would always create a new impl block for
the struct, even if there already is one. Now, it'll put the extracted
method in the matching existing block if it exists.
