Has* methods on messages ambiguous for union types.

[abraithwaite]

Just noticed this. If you have a union type in a struct and you check msg.Has* for the different union types, they'll both return true if only one is set.

From the generated code:

func (s Message) HasLog() bool {
    p, err := s.Struct.Ptr(1)
    return p.IsValid() || err != nil
}

func (s Message) HasRequest() bool {
    p, err := s.Struct.Ptr(1)
    return p.IsValid() || err != nil
}

[abraithwaite]

Not sure if anything needs to be done about this. Maybe a little documentation is all.

[zombiezen]

Hm. While in general the behavior of using the wrong union field is undefined, perhaps there should be more explicit checking. What does the C++ implementation do?

[zombiezen]

C++ does do this check. It also makes assertions for every union member access that which matches.

[zombiezen]

Forgot to mention: I opened #56 to add runtime assertions for other accessor methods.