Message 391582 - Python tracker

FWIW, I was the one who converted arraymodule to use heap types in 75bf107c62fbdc00af51ee4f6ab69df4bd201104 (GH-23124) in January. Sorry 'bout the accidental change of behaviour.

> I think we may need a new flag bit meaning "built-in type, immutable". This bit should not be inherited of course.

+1.

See attached PoC patch. As far as I understand, type flags must be explicitly inherited in Objects/typeobject.c, no?

Should all previous static types be immutable, or are there exceptions?