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Minor updates to protocol semantics #3996

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Merged
gvanrossum merged 6 commits into from
Sep 29, 2017
Merged

Minor updates to protocol semantics #3996

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ec7e239
None should be subtype of empty protocol
ilevkivskyi Sep 24, 2017
2876a95
Apply None rule only to Callables, add unrelated previously forgotten…
ilevkivskyi Sep 24, 2017
fcdb276
Prohibit issubclass() for non-method protocols
ilevkivskyi Sep 24, 2017
22f942c
Merge remote-tracking branch 'upstream/master' into update-protocols
ilevkivskyi Sep 28, 2017
c31c99f
Address CR
ilevkivskyi Sep 28, 2017
07de2a3
Restore correct typeshed commit
ilevkivskyi Sep 28, 2017
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Address CR
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@ilevkivskyi
ilevkivskyi committed Sep 28, 2017
commit c31c99fbaa0be2b37eae84e43263020aa3736a6f
43 changes: 24 additions & 19 deletions mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -264,32 +264,37 @@ def visit_call_expr(self, e: CallExpr, allow_none_return: bool = False) -> Type:
callee_type = self.apply_method_signature_hook(
e, callee_type, object_type, signature_hook)
ret_type = self.check_call_expr_with_callee_type(callee_type, e, fullname, object_type)
if (isinstance(e.callee, RefExpr) and len(e.args) == 2 and
e.callee.fullname in ('builtins.isinstance', 'builtins.issubclass')):
for expr in mypy.checker.flatten(e.args[1]):
tp = self.chk.type_map[expr]
if (isinstance(tp, CallableType) and tp.is_type_obj() and
tp.type_object().is_protocol and
not tp.type_object().runtime_protocol):
self.chk.fail('Only @runtime protocols can be used with'
' instance and class checks', e)
if (isinstance(e.callee, RefExpr) and len(e.args) == 2 and
e.callee.fullname == 'builtins.issubclass'):
for expr in mypy.checker.flatten(e.args[1]):
tp = self.chk.type_map[expr]
if (isinstance(tp, CallableType) and tp.is_type_obj() and
tp.type_object().is_protocol):
attr_members = non_method_protocol_members(tp.type_object())
if attr_members:
self.chk.msg.report_non_method_protocol(tp.type_object(),
attr_members, e)
if isinstance(e.callee, RefExpr) and len(e.args) == 2:
if e.callee.fullname in ('builtins.isinstance', 'builtins.issubclass'):
self.check_runtime_protocol_test(e)
if e.callee.fullname == 'builtins.issubclass':
self.check_protocol_issubclass(e)
if isinstance(ret_type, UninhabitedType):
self.chk.binder.unreachable()
if not allow_none_return and isinstance(ret_type, NoneTyp):
self.chk.msg.does_not_return_value(callee_type, e)
return AnyType(TypeOfAny.from_error)
return ret_type

def check_runtime_protocol_test(self, e: CallExpr) -> None:
for expr in mypy.checker.flatten(e.args[1]):
tp = self.chk.type_map[expr]
if (isinstance(tp, CallableType) and tp.is_type_obj() and
tp.type_object().is_protocol and
not tp.type_object().runtime_protocol):
self.chk.fail('Only @runtime protocols can be used with'
' instance and class checks', e)

def check_protocol_issubclass(self, e: CallExpr) -> None:
for expr in mypy.checker.flatten(e.args[1]):
tp = self.chk.type_map[expr]
if (isinstance(tp, CallableType) and tp.is_type_obj() and
tp.type_object().is_protocol):
attr_members = non_method_protocol_members(tp.type_object())
if attr_members:
self.chk.msg.report_non_method_protocol(tp.type_object(),
attr_members, e)

def check_typeddict_call(self, callee: TypedDictType,
arg_kinds: List[int],
arg_names: Sequence[Optional[str]],
Expand Down
10 changes: 10 additions & 0 deletions test-data/unit/check-protocols.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2132,6 +2132,16 @@ class P(Protocol):
x: P = None

@JukkaL JukkaL Sep 28, 2017

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Also test that None is compatible with a non-empty protocol when not using strict optional checking.

[out]

[case testNoneSubtypeOfAllProtocolsWithoutStrictOptional]
from typing import Protocol
class P(Protocol):
attr: int
def meth(self, arg: str) -> str:
pass

x: P = None
[out]

[case testNoneSubtypeOfEmptyProtocolStrict]
# flags: --strict-optional
from typing import Protocol
Expand Down