mypy

52de0c73 - [mypyc] Preserve inherited attribute defaults under separate=True (#21547)

[mypyc] Preserve inherited attribute defaults under separate=True (#21547) Fixes #21542 Under `separate=True`, when a subclass is recompiled while its parent is loaded from mypy's incremental cache, parent default-attribute assignments are silently dropped from the subclass's `__mypyc_defaults_setup`. The first read of an inherited default-attr then raises: ``` AttributeError: attribute '<name>' of '<Parent>' undefined ``` `find_attr_initializers` walks `cdef.info.mro` and reads `info.defn.defs.body` for `AssignmentStmt`s. `ClassDef.serialize` (mypy/nodes.py) does not serialize `defs`, so a cache-loaded parent has `defs = Block([])`; the MRO walk collects no parent assignments and the subclass's emitted setup leaves inherited slots in the undefined-sentinel state. This PR implements the fix discussed in the linked issue.