Nesting of block indented expressions

[topecongiro]

Closes #1422, closes #1449, and closes #1494.

[nrc]

This looks great, thanks for tackling it! I wonder if tuples need covering and if there are any other constructs that need covering. Other than that, this looks good to merge

[nrc]

Should we handle tuples here too?

[topecongiro]

Tuples are not refered in rust-lang/style-team#61, but if we should, do we use "a single expression parameter" rule or allow exception like clousres?

// A single expression tuple
let a = foo(bar((|x| {
    let y = x + 1;
    let z = y + 1;
    z
})));

// Should we allow this?
let a = foo(bar((b, c, |x| {
    let y = x + 1;
    let z = y + 1;
    z
})));

[nrc]

I think we should allow both (note that tuples with a single element must always have a trailing comma).

[topecongiro]

Thanks for clarifying!

[topecongiro]

I would like to make it clear, should we use block indent for tuples when fn_call_style = Block and format like function call? (c.f. rust-lang/style-team#64)

let a = (
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
    yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy,
);

[nrc]

yes, I think so

[topecongiro]

I have added tuple and block. Also added a commit to add a trailing comma to a single arg in multiline.
Now rewriting tuple uses the same function as rewriting function call when fn_call_style = Block.

[nrc]

Awesome, thank you!