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Fix narrowing from object to Optional #4118

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Merged
merged 2 commits into from
Oct 26, 2017
Merged

Fix narrowing from object to Optional #4118

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fadfcff
Fix narrowing from object to Optional
ilevkivskyi Oct 13, 2017
f06e8a5
Fix test
ilevkivskyi Oct 13, 2017
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4 changes: 4 additions & 0 deletions mypy/meet.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,10 @@ class C(A, B): ...
# Any overlaps with everything
if isinstance(t, AnyType) or isinstance(s, AnyType):
return True
# object overlaps with everything
if (isinstance(t, Instance) and t.type.fullname() == 'builtins.object' or
isinstance(s, Instance) and s.type.fullname() == 'builtins.object'):
return True

# Since we are effectively working with the erased types, we only
# need to handle occurrences of TypeVarType at the top level.
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8 changes: 8 additions & 0 deletions test-data/unit/check-optional.test
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Expand Up @@ -642,3 +642,11 @@ def test_or_shortcut(value: Optional[Any]) -> None:
if not value or value.get('foo') == 'hello':
pass
[builtins fixtures/bool.pyi]

[case testNarrowingFromObjectToOptional]
from typing import Optional
x: object
y: Optional[int]
x = y
reveal_type(x) # E: Revealed type is 'Union[builtins.int, builtins.None]'
[out]
6 changes: 3 additions & 3 deletions test-data/unit/check-unions.test
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Expand Up @@ -902,10 +902,10 @@ x: object
a: Any
d: Dict[str, Tuple[List[Tuple[str, str]], str]]
x, _ = d.get(a, (None, None))
# FIXME: fix narrow_declared_type for narrowed Optional types.
reveal_type(x) # E: Revealed type is 'builtins.list[Tuple[builtins.str, builtins.str]]'
reveal_type(x) # E: Revealed type is 'Union[builtins.list[Tuple[builtins.str, builtins.str]], builtins.None]'

for y in x: pass
if x:
for y in x: pass
[builtins fixtures/dict.pyi]
[out]

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