mypy

9393fa1e - [mypyc] Track definedness of native int attributes using a bitmap (#13532)

[mypyc] Track definedness of native int attributes using a bitmap (#13532) Since native ints can't support a reserved value to mark an undefined attribute, use a separate bitmap attribute (or attributes) to store information about defined/undefined attributes with native int types. The bitmap is only defined if we can't infer that an attribute is always defined, and it's only needed for native int attributes. We only access the bitmap if the runtime value of an attribute is equal to the (overlapping) error value. This way the performance cost of the bitmap is pretty low on average. I'll add support for traits in a follow-up PR to keep this PR simple. Work on mypyc/mypyc#837.