fix: Insert spaces when inlining a function defined in a macro.

[zachs18]

(partially) fixes #12860.

This PR (only) addresses the whitespace issue when inlining functions defined in macros.

Additionally, the indentation/spacing is not ideal, but works, e.g.

macro_rules! define_function {
    () => { fn test_function_macro() {
        if let Some(3) = 3i32.checked_add(0) {
            println!("3 + 0 == 3");
        }
    } };
}
define_function!();
fn main() {
    test_function_macro();
}
// previously became
// ...
fn main() {
    ifletSome(3)=3i32.checked_add(0){println!("3 + 0 == 3");};
}
// now becomes
// ...
fn main() {
    if let Some(3) = 3i32.checked_add(0){
        println!("3 + 0 == 3");
        
      };
}

The self -> this problem¹ is (probably?) a separate problem that I am also looking into.

Footnotes

1. As mentioned in my comment on the above issue, inlining a method defined in a macro does not properly replace self with the new local this. ↩

[Veykril]

Thanks! I think the FIXME comment can just go
@bors delegate+

[bors]

✌️ @zachs18 can now approve this pull request

[zachs18]

Okay, I removed the FIXME comment. Thanks!
@bors r+

[bors]

📌 Commit add33b6 has been approved by zachs18

It is now in the queue for this repository.

[bors]

⌛ Testing commit add33b6 with merge c2eebd7...

[bors]

☀️ Test successful - checks-actions
Approved by: zachs18
Pushing c2eebd7 to master...