Formatter loses comments in let statements

[dplassgit]

Similar to #1697 and #1739

To Reproduce
Format:

    let X = // before value
        u32:32;

Expected behavior
Output = input

Actual behavior
Comment is lost:

    let X = u32:32;

It also loses a comment between the value and the semicolon.

[dplassgit]

A similar approach to how const was fixed in 4caeda4 is probably warranted.

[dplassgit]

It won't lose the comment anymore (as of 2398f4b)

But fixing it properly might be warranted.