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Make return type implicitly None for type checked __init__ and __init_subclass__ #5677

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merged 8 commits into from
Oct 1, 2018
Merged

Make return type implicitly None for type checked __init__ and __init_subclass__ #5677

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ea1f7da
Make return type implicitly None
onlined Sep 26, 2018
dd0b7e6
Assert for type checking
onlined Sep 26, 2018
5c6eaac
Fix import style
onlined Sep 26, 2018
2563c34
Add decorated tests
onlined Sep 26, 2018
7a82feb
Correct first parameter of __init_subclass__
onlined Sep 26, 2018
d65bb74
Add overloaded tests
onlined Sep 26, 2018
3f84608
Correct test name
onlined Sep 27, 2018
9becf45
Add explicit Any return type tests
onlined Sep 27, 2018
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7 changes: 5 additions & 2 deletions mypy/semanal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,8 +68,7 @@
from mypy.types import (
FunctionLike, UnboundType, TypeVarDef, TupleType, UnionType, StarType, function_type,
CallableType, Overloaded, Instance, Type, AnyType,
TypeTranslator, TypeOfAny, TypeType,
)
TypeTranslator, TypeOfAny, TypeType, NoneTyp)
from mypy.nodes import implicit_module_attrs
from mypy.typeanal import (
TypeAnalyser, analyze_type_alias, no_subscript_builtin_alias,
Expand Down Expand Up @@ -407,6 +406,10 @@ def _visit_func_def(self, defn: FuncDef) -> None:
add_symbol = False
if add_symbol:
self.type.names[defn.name()] = SymbolTableNode(MDEF, defn)
if defn.type is not None and defn.name() in ('__init__', '__init_subclass__'):
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Are you sure this works with overloads and decorated methods? Please add tests to verify that.

Also perhaps it should only work inside a class definition?

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I think one needs similar check at least in visit_overloaded_func_def.

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@gvanrossum It works only inside a class definition.
@gvanrossum @ilevkivskyi You are right, I will find a way to extend behavior.

assert isinstance(defn.type, CallableType)
if isinstance(defn.type.ret_type, AnyType):
defn.type = defn.type.copy_modified(ret_type=NoneTyp())
self.prepare_method_signature(defn, self.type)
elif self.is_func_scope():
# Nested function
Expand Down
2 changes: 0 additions & 2 deletions test-data/unit/check-classes.test
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Expand Up @@ -577,7 +577,6 @@ import typing
class A:
def __init__(self, x: int): pass
[out]
main:3: error: The return type of "__init__" must be None

[case testInitSubclassWithReturnValueType]
import typing
Expand All @@ -591,7 +590,6 @@ import typing
class A:
def __init_subclass__(cls, x: int=1): pass
[out]
main:3: error: The return type of "__init_subclass__" must be None

[case testGlobalFunctionInitWithReturnType]
import typing
Expand Down