Support metaclasses #2475
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -1946,6 +1946,29 @@ def __init__(self, names: 'SymbolTable', defn: ClassDef, module_name: str) -> No | |
| for vd in defn.type_vars: | ||
| self.type_vars.append(vd.name) | ||
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| _metaclass_type = None # type: Optional[mypy.types.Instance] | ||
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| @property | ||
| def metaclass_type(self) -> 'Optional[mypy.types.Instance]': | ||
| if self._metaclass_type: | ||
| return self._metaclass_type | ||
| if self._fullname == 'builtins.type': | ||
| return mypy.types.Instance(self, []) | ||
| if self.mro is None: | ||
| # XXX why does this happen? | ||
| return None | ||
| if len(self.mro) > 1: | ||
| return self.mro[1].metaclass_type | ||
| # FIX: assert False | ||
| return None | ||
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| @metaclass_type.setter | ||
| def metaclass_type(self, value: 'mypy.types.Instance'): | ||
| self._metaclass_type = value | ||
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| def is_metaclass(self) -> bool: | ||
| return self.has_base('builtins.type') | ||
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| def name(self) -> str: | ||
| """Short name.""" | ||
| return self.defn.name | ||
|
3CAE
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Do you have a sample that triggers this condition?
Presumably the clue is the comment in
__init__on line 1940 above. Maybe it has something to do with the MRO being calculated twice -- the first time (in semanal.py on line 850) it may fail if there's an import cycle causing a base class being a forward reference; the second time on line 3128 in ThirdPass, called from build.py line 1440. (There's also a call from fixup.py, but I think that's not what you're seeing.)There was a problem hiding this comment.
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Turns out it happens during deserialization in incremental mode: the type of a direct base class may be None. (I should have looked into it long time ago. Sorry)
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I think I will remove the call from deserialize, since it shouldn't be done yet - it should be done from fixup.py. Does it sound reasonable?