Complete statement command for Rust Analyzer

[gnut-neygun]

IntelliJ Rust has a very useful command called "complete statement". How it works:

• If current line is a well-formed statement, e.g let a = 2 then move cursor to the end of line and add a semicolon.
• If the line is in the middle of a function name, e.g fn func_name then transform it to

  
  fn func_name(){

}

and move cursor to inside function body. Same for struct, enum, trait
- If we are in the middle of a well formed if clause, i.e: `if x > 2`, then transform it to:
```rust
if x > 2 {

}

and move cursor inside the curly brackets. Same for while, for, match, loop (this one is not in IntelliJ Rust but in Typescript and Kotlin on IntelliJ platform.)

• Any other cases, move cursor to the end of line. (or add more smarter behaviors, basically we try to complete the statement if it make senses)

It would be nice if Rust Analyzer can also have that. I normally bind this command to Shift + Enter key. That way I can end statements with one key combination. It's really convenient.

[Veykril]

I guess we could re-use the fixup machinery for this?

[flodiebold]

We could try, but I think they are likely to differ since they serve very different purposes.

[alibektas]

If I am given some instructions, I'd be happy to do it.