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Merged
hauntsaninja merged 2 commits into from
Jan 22, 2026
Merged

Move tests to check-narrowing , improve them slightly #20637

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fbc57f7
Move tests to check-narrowing
hauntsaninja Jan 11, 2026
a593d58
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hauntsaninja Jan 22, 2026
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123 changes: 0 additions & 123 deletions test-data/unit/check-isinstance.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2699,129 +2699,6 @@ else:
reveal_type(x) # N: Revealed type is "type[__main__.A]"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsCheck]
from typing import Any

y: Any
if type(y) == int:
reveal_type(y) # N: Revealed type is "builtins.int"


[case testMultipleTypeEqualsCheck]
from typing import Any

x: Any
y: Any
if type(x) == type(y) == int:
reveal_type(y) # N: Revealed type is "builtins.int"
reveal_type(x) # N: Revealed type is "builtins.int"

[case testTypeEqualsCheckUsingIs]
from typing import Any

y: Any
if type(y) is int:
reveal_type(y) # N: Revealed type is "builtins.int"

[case testTypeEqualsCheckUsingIsNonOverlapping]
# flags: --warn-unreachable
from typing import Union

y: str
if type(y) is int: # E: Subclass of "str" and "int" cannot exist: would have incompatible method signatures
y # E: Statement is unreachable
else:
reveal_type(y) # N: Revealed type is "builtins.str"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsCheckUsingIsNonOverlappingChild-xfail]
# flags: --warn-unreachable
from typing import Union

class A: ...
class B: ...
class C(A): ...
x: Union[B, C]
# C instance cannot be exactly its parent A, we need reversed subtyping relationship
# here (type(parent) is Child).
if type(x) is A:
reveal_type(x) # E: Statement is unreachable
else:
reveal_type(x) # N: Revealed type is "Union[__main__.B, __main__.C]"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsNarrowingUnionWithElse]
from typing import Union

x: Union[int, str]
if type(x) is int:
reveal_type(x) # N: Revealed type is "builtins.int"
else:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"

[case testTypeEqualsMultipleTypesShouldntNarrow]
# flags: --warn-unreachable
# make sure we don't do any narrowing if there are multiple types being compared

from typing import Union

x: Union[int, str]
if type(x) == int == str:
reveal_type(x) # E: Statement is unreachable
else:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"

# mypy thinks int isn't defined unless we include this
[builtins fixtures/primitives.pyi]

[case testTypeNotEqualsCheck]
from typing import Union

x: Union[int, str]
if type(x) != int:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"
else:
reveal_type(x) # N: Revealed type is "builtins.int"

# mypy thinks int isn't defined unless we include this
[builtins fixtures/primitives.pyi]

[case testTypeNotEqualsCheckUsingIsNot]
from typing import Union

x: Union[int, str]
if type(x) is not int:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"
else:
reveal_type(x) # N: Revealed type is "builtins.int"

[case testNarrowInElseCaseIfFinal]
from typing import final, Union
@final
class C:
pass
class D:
pass

x: Union[C, D]
if type(x) is C:
reveal_type(x) # N: Revealed type is "__main__.C"
else:
reveal_type(x) # N: Revealed type is "__main__.D"
[case testNarrowInIfCaseIfFinalUsingIsNot]
from typing import final, Union
@final
class C:
pass
class D:
pass

x: Union[C, D]
if type(x) is not C:
reveal_type(x) # N: Revealed type is "__main__.D"
else:
reveal_type(x) # N: Revealed type is "__main__.C"

[case testHasAttrExistingAttribute]
class C:
x: int
Expand Down
130 changes: 130 additions & 0 deletions test-data/unit/check-narrowing.test
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Original file line number Diff line number Diff line change
Expand Up @@ -2920,3 +2920,133 @@ def f2(x: Any) -> None:
return
reveal_type(x) # N: Revealed type is "Any"
[builtins fixtures/tuple.pyi]

[case testTypeEqualsCheck]
# flags: --strict-equality --warn-unreachable
from typing import Any

y: Any
if type(y) == int:
reveal_type(y) # N: Revealed type is "builtins.int"

[case testMultipleTypeEqualsCheck]
# flags: --strict-equality --warn-unreachable
from typing import Any

x: Any
y: Any
if type(x) == type(y) == int:
reveal_type(y) # N: Revealed type is "builtins.int"
reveal_type(x) # N: Revealed type is "builtins.int"

[case testTypeEqualsCheckUsingIs]
# flags: --strict-equality --warn-unreachable
from typing import Any

y: Any
if type(y) is int:
reveal_type(y) # N: Revealed type is "builtins.int"

[case testTypeEqualsCheckUsingIsNonOverlapping]
# flags: --strict-equality --warn-unreachable
from typing import Union

y: str
if type(y) is int: # E: Non-overlapping identity check (left operand type: "type[str]", right operand type: "type[int]") \
# E: Subclass of "str" and "int" cannot exist: would have incompatible method signatures
y # E: Statement is unreachable
else:
reveal_type(y) # N: Revealed type is "builtins.str"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsCheckUsingIsNonOverlappingChild-xfail]
# flags: --strict-equality --warn-unreachable
from typing import Union

class A: ...
class B: ...
class C(A): ...
def main(x: Union[B, C]):
# C instance cannot be exactly its parent A, we need reversed subtyping relationship
# here (type(parent) is Child).
if type(x) is A:
reveal_type(x) # E: Statement is unreachable
else:
reveal_type(x) # N: Revealed type is "Union[__main__.B, __main__.C]"
[builtins fixtures/isinstance.pyi]

[case testTypeEqualsNarrowingUnionWithElse]
# flags: --strict-equality --warn-unreachable
from typing import Union

x: Union[int, str]
if type(x) is int:
reveal_type(x) # N: Revealed type is "builtins.int"
else:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"

[case testTypeEqualsMultipleTypesShouldntNarrow]
# flags: --strict-equality --warn-unreachable

from typing import Union

x: Union[int, str]
if type(x) == int == str: # E: Non-overlapping equality check (left operand type: "type[int]", right operand type: "type[str]")
reveal_type(x) # E: Statement is unreachable
else:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"

[builtins fixtures/primitives.pyi]

[case testTypeNotEqualsCheck]
# flags: --strict-equality --warn-unreachable
from typing import Union

x: Union[int, str]
if type(x) != int:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"
else:
reveal_type(x) # N: Revealed type is "builtins.int"

# mypy thinks int isn't defined unless we include this
[builtins fixtures/primitives.pyi]

[case testTypeNotEqualsCheckUsingIsNot]
# flags: --strict-equality --warn-unreachable
from typing import Union

x: Union[int, str]
if type(x) is not int:
reveal_type(x) # N: Revealed type is "builtins.int | builtins.str"
else:
reveal_type(x) # N: Revealed type is "builtins.int"

[case testNarrowInElseCaseIfFinal]
# flags: --strict-equality --warn-unreachable
from typing import final, Union
@final
class C:
pass
class D:
pass

x: Union[C, D]
if type(x) is C:
reveal_type(x) # N: Revealed type is "__main__.C"
else:
reveal_type(x) # N: Revealed type is "__main__.D"

[case testNarrowInIfCaseIfFinalUsingIsNot]
# flags: --strict-equality --warn-unreachable
from typing import final, Union
@final
class C:
pass
class D:
pass

x: Union[C, D]
if type(x) is not C:
reveal_type(x) # N: Revealed type is "__main__.D"
else:
reveal_type(x) # N: Revealed type is "__main__.C"