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Merged
JelleZijlstra merged 2 commits into from
Oct 11, 2021
Merged

None.__bool__ returns Literal[False] #11290

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d99807e
WIP: `None.__bool__` returns `Literal[False]`, refs #11287
sobolevn Oct 7, 2021
1cfc73e
Adds support for `None.__bool__` when `show_none_errors = False` is set
sobolevn Oct 7, 2021
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7 changes: 4 additions & 3 deletions mypy/checkmember.py
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Original file line number Diff line number Diff line change
Expand Up @@ -317,17 +317,18 @@ def analyze_union_member_access(name: str, typ: UnionType, mx: MemberContext) ->


def analyze_none_member_access(name: str, typ: NoneType, mx: MemberContext) -> Type:
if mx.chk.should_suppress_optional_error([typ]):
return AnyType(TypeOfAny.from_error)
is_python_3 = mx.chk.options.python_version[0] >= 3
# In Python 2 "None" has exactly the same attributes as "object". Python 3 adds a single
# extra attribute, "__bool__".
if is_python_3 and name == '__bool__':
literal_false = LiteralType(False, fallback=mx.named_type('builtins.bool'))
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return CallableType(arg_types=[],
arg_kinds=[],
arg_names=[],
ret_type=mx.named_type('builtins.bool'),
ret_type=literal_false,
fallback=mx.named_type('builtins.function'))
elif mx.chk.should_suppress_optional_error([typ]):
return AnyType(TypeOfAny.from_error)
else:
return _analyze_member_access(name, mx.named_type('builtins.object'), mx)

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11 changes: 10 additions & 1 deletion test-data/unit/check-basic.test
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Expand Up @@ -401,9 +401,18 @@ def foo(
[case testNoneHasBool]
none = None
b = none.__bool__()
reveal_type(b) # N: Revealed type is "builtins.bool"
reveal_type(b) # N: Revealed type is "Literal[False]"
[builtins fixtures/bool.pyi]

[case testNoneHasBoolShowNoneErrorsFalse]
none = None
b = none.__bool__()
reveal_type(b) # N: Revealed type is "Literal[False]"
[builtins fixtures/bool.pyi]
[file mypy.ini]
\[mypy]
show_none_errors = False

[case testAssignmentInvariantNoteForList]
from typing import List
x: List[int]
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