Segmentation fault with custom TypeTraverserVisitor

[mkurnikov]

I'm trying to copy methods from one class into the other, need to add some imports to other class' module.
https://github.com/django/django/blob/b9cf764be62e77b4777b3a75ec256f6209a57671/django/db/models/manager.py#L101

I'd like to use custom TypeTraverserVisitor for that

signature_node: FuncDef

def import_symbol_from_source(name: str) -> None:
    if name in source_symbols['__builtins__'].node.names:
        return
    sym = source_symbols[name].copy()
    self.semanal_api.add_imported_symbol(name, sym, context=self.semanal_api.cur_mod_node)

class UnimportedTypesVisitor(TypeTraverserVisitor):
    def visit_instance(self, t: Instance) -> None:
        super().visit_instance(t)
        if isinstance(t.type, FakeInfo):
            return
        type_name = t.type.name
        sym = currently_imported_symbols.get(type_name)
        if sym is None:
            import_symbol_from_source(type_name)

signature_node.type.accept(UnimportedTypesVisitor())

Compiled version of mypy segfaults for me, when I'm trying to use code like this. The plain Python version runs just fine.

[msullivan]

Could you try to produce a standalone test case for me to run somehow?

[msullivan]

There are two issues here: that we don't support what this code does, and that it segfaults. I've opened mypyc/mypyc#754 for the former and submitted #9248 for the latter.

The specific problem is that we don't support subclassing compiled traits from interpreted code. We could create a concrete subclass of TypeTraverserVisitor in complied code, though, and you could subclass that?
(Eventually we want to actually support this, of course, but we don't yet.)