Class level scoping is miscompiled

[JelleZijlstra]

Compiling the below:

from typing import Final

class StringParser:
    DEFAULT_TOKEN: Final = -1
    d: Final = {DEFAULT_TOKEN: 1}

And running it produces:

$ mypyc fud.py
$ python -c 'import fud'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "fud.py", line 5, in <module>
    d: Final = {DEFAULT_TOKEN: 1}
KeyError: 'DEFAULT_TOKEN'

The relevant snippet of C code is:

    cpy_r_r39 = CPyStatic_globals;
    cpy_r_r40 = CPyStatics[3]; /* 'DEFAULT_TOKEN' */
    cpy_r_r41 = CPyDict_GetItem(cpy_r_r39, cpy_r_r40);

This looks like it's looking up the name in the globals dict instead of the class dict.

It doesn't reproduce with a positive integer, float, or string Final.

This is minimized from code in Black, originally found by @ichard26.

[msullivan]

Oh, argh.

I think the core issue here is that we don't really understand class-level scoping.
... and it comes up with negative integers because mypyc doesn't understand negative integers are constants.

[JukkaL]

There seem to be two things to fix:

• Support negative integers as constants (or more generally, various integer operations involving constants expressions, such as addition and bitwise ops).
• Fix class-level scoping in general.

[JukkaL]

python/mypy#14283 fixes the negative integer case.