ModelBuilderSemantics Subclassing

[Victorious3]

start = expression $;

expression =
    | addition
    | subtraction
    | number;

addition::BinaryOp::Op = left:expression op:'+' ~ right:number;
subtraction::BinaryOp::Op = left:expression op:'-' ~ right:number;

number = /\d+/;

This triggers an exception: https://pastebin.com/raw/qMUUXEKb
It works when you remove left:expression in addition and subtraction

I'm not sure how this feature is supposed to work in the first place, how does it decide what to put on the base class and what on the inherited one? I suppose the workaround would be to create the base class manually and pass it to the ModelBuilderSemantics instance.

In either case, this should be documented better.

[apalala]

Python 3.7 is recent, and the semantics of metaclasses may have changed to better support typing. This case should be added as a unit test.

[Victorious3]

This isn't just broken in 3.7. While the above compiles on 3.5, BinaryOp doesn't end up being a subclass of Op either. I'll see if I can come up with a fix.
Edit: As I found out, you are supposed to generate the object model as well and then use that as an instance. It's quite dubious, and not documented.

[Victorious3]

@apalala What's supposed to happen if there are multiple base classes?

rule2::A::B::C = a:();

Is B a subclass of C now, and A a subclass of B?
Or does A inherit from B and C, and B is unrelated to C?

[apalala]

@apalala What's supposed to happen if there are multiple base classes?

rule2::A::B::C = a:();

Is B a subclass of C now, and A a subclass of B?
Or does A inherit from B and C, and B is unrelated to C?

TasSu currently doesn't check that the inheritance tree makes sense. I guess the Python compiler will err if the generated Python is no good.