Empty line after comment is removed

When there is an empty line after a comment in a struct declaration or struct literal, it is removed. This happened to me in a struct where fields are grouped logically, as in this example:

struct MyStruct {
    field1: String,
    field2: usize,
    field3: MyType,
    // This group ends here, and I want this comment to be attached to its end

    field4: f64,
    field5: f64,
    field6: f64,
}

Running rustfmt on the code above removes the empty line, destroying the logical grouping of the fields.

Start by reproducing the reported rustfmt behavior with the Rust struct example in the issue, then trace how rustfmt handles comments and blank lines in struct declarations and literals. Done means the empty line after a comment is preserved while formatting, with coverage for both forms.