BUGFIX- recursive active pattern with [<return: Struct>] was not possible

[T-Gro]

Following code:

[<return: Struct>]let rec(|HasOne|_|)xs =match xs with|[]-> ValueNone
| h::_when h =1-> ValueSome true|_::tail ->match tail with| HasOne x -> ValueSome x
|_-> ValueNone

Was failing with:
error FS0001: The type ''a option' does not match the type 'bool voption'

This fixes it + adds more test around struct active patterns, I did not find much of them in the codebase.

[edgarfgp]

Love to see this fixed . Thanks 👍