Non-multiple of four indentation in closure arg pattern

[dtolnay]

The following unformatted line:

fn f() {
    let y = x.into_iter().map(|AaaaaaAaaaaaaaaaa{bbbbbb_bbbb,ccc_ccccccc}|());
}

currently gets formatted as:

fn f() {
    let y = x.into_iter().map(
        |AaaaaaAaaaaaaaaaa {
             bbbbbb_bbbb,
             ccc_ccccccc,
         }| (),
    );
}

This has some lines with 13 and 9 space indentation, which contradicts the indentation convention in the style guide RFC.

Each level of indentation must be four spaces (that is, all indentation outside of string literals and comments must be a multiple of four).

[topecongiro]

The above example should be indented four spaces. On the other hand, the style guide does not yet specify what we should do when the closure's arguments are too long to fit in a single line. If we want to keep the style consistent with function declaration, then we should format closures like the following:

fn f() {
    // visual indent
    let x = |_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32,
             _yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: u32,
             _zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz: u32|
    {
        println!("foo");
    };
    // block indent
    let y = |
        _xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: u32,
        _yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy: u32,
        _zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz: u32,
    | {
        println!("foo");
    };
}