Wrong XmlDoc for union case when previous case contains no bar

[auduchinok]

Xml doc has wrong reported range (which may affect tooling) and a comment from previous case without bar is shown in the wrong case:

type U =
    /// Aa
    A
    /// Bb
    | B

With bar it works as expected:

type U =
    /// Aa
    | A
    /// Bb
    | B

[auduchinok]

Another issue is the comment is not detected for A at all:

[Smaug123]

I was about to report this exact issue, due to this: fsprojects/fantomas#1563

What I was going to report was that the following gets no docstring emitted:

type Foo =
    /// Hi!
    Bar of int

Whereas it does in the following:

type Foo =
    /// Hi!
    | Bar of int