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Support narrowing unions that include type[None]. #16315

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Merged
hauntsaninja merged 7 commits into from
Jan 14, 2024
Merged

Support narrowing unions that include type[None]. #16315

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05f2c71
Support narrowing unions that include type[None].
tyralla Oct 23, 2023
1ea576c
Merge branch 'master' into fix/narrow_nonetype
tyralla Oct 23, 2023
32ca5f4
special case `types.NoneType`
tyralla Oct 24, 2023
fc853e9
Merge branch 'master' into fix/narrow_nonetype
tyralla Dec 4, 2023
fe12f7d
Add test case `testNarrowingIsInstanceNoIntersectionWithFinalTypeAndN…
tyralla Dec 5, 2023
58f0562
A little additional effort for `Subclass of "..." and "NoneType" cann…
tyralla Dec 5, 2023
55b2858
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Dec 5, 2023
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Support narrowing unions that include type[None].
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@tyralla
tyralla committed Oct 23, 2023
commit 05f2c713556be88b73e8c73159d958642683b5ad
8 changes: 6 additions & 2 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6831,7 +6831,11 @@ def get_isinstance_type(self, expr: Expression) -> list[TypeRange] | None:
elif isinstance(typ, TypeType):
# Type[A] means "any type that is a subtype of A" rather than "precisely type A"
# we indicate this by setting is_upper_bound flag
types.append(TypeRange(typ.item, is_upper_bound=True))
is_upper_bound = True
if isinstance(typ.item, NoneType):
# except for Type[None], because "'NoneType' is not an acceptable base type"
is_upper_bound = False
types.append(TypeRange(typ.item, is_upper_bound=is_upper_bound))
elif isinstance(typ, Instance) and typ.type.fullname == "builtins.type":
object_type = Instance(typ.type.mro[-1], [])
types.append(TypeRange(object_type, is_upper_bound=True))
Expand Down Expand Up @@ -7258,7 +7262,7 @@ def convert_to_typetype(type_map: TypeMap) -> TypeMap:
if isinstance(t, TypeVarType):
t = t.upper_bound
# TODO: should we only allow unions of instances as per PEP 484?
if not isinstance(get_proper_type(t), (UnionType, Instance)):
if not isinstance(get_proper_type(t), (UnionType, Instance, NoneType)):
# unknown type; error was likely reported earlier
return {}
converted_type_map[expr] = TypeType.make_normalized(typ)
Expand Down
16 changes: 9 additions & 7 deletions mypy/checkexpr.py
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Expand Up @@ -496,13 +496,13 @@ def visit_call_expr_inner(self, e: CallExpr, allow_none_return: bool = False) ->
if is_expr_literal_type(typ):
self.msg.cannot_use_function_with_type(e.callee.name, "Literal", e)
continue
if (
node
and isinstance(node.node, TypeAlias)
and isinstance(get_proper_type(node.node.target), AnyType)
):
self.msg.cannot_use_function_with_type(e.callee.name, "Any", e)
continue
if node and isinstance(node.node, TypeAlias):
target = get_proper_type(node.node.target)
if isinstance(target, AnyType):
self.msg.cannot_use_function_with_type(e.callee.name, "Any", e)
continue
if isinstance(target, NoneType):
continue
if (
isinstance(typ, IndexExpr)
and isinstance(typ.analyzed, (TypeApplication, TypeAliasExpr))
Expand Down Expand Up @@ -4645,6 +4645,8 @@ class LongName(Generic[T]): ...
return type_object_type(tuple_fallback(item).type, self.named_type)
elif isinstance(item, TypedDictType):
return self.typeddict_callable_from_context(item)
elif isinstance(item, NoneType):
return TypeType(item, line=item.line, column=item.column)
elif isinstance(item, AnyType):
return AnyType(TypeOfAny.from_another_any, source_any=item)
else:
Expand Down
35 changes: 35 additions & 0 deletions test-data/unit/check-narrowing.test
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Expand Up @@ -1334,3 +1334,38 @@ if isinstance(some, raw):
else:
reveal_type(some) # N: Revealed type is "Union[builtins.int, __main__.Base]"
[builtins fixtures/dict.pyi]


[case testNarrowingIsSubclassNoneType1]
from typing import Type, Union

def f(cls: Type[Union[None, int]]) -> None:
if issubclass(cls, int):
reveal_type(cls) # N: Revealed type is "Type[builtins.int]"
else:
reveal_type(cls) # N: Revealed type is "Type[None]"
[builtins fixtures/isinstance.pyi]


[case testNarrowingIsSubclassNoneType2]
from typing import Type, Union

def f(cls: Type[Union[None, int]]) -> None:
if issubclass(cls, type(None)):
reveal_type(cls) # N: Revealed type is "Type[None]"
else:
reveal_type(cls) # N: Revealed type is "Type[builtins.int]"
[builtins fixtures/isinstance.pyi]


[case testNarrowingIsSubclassNoneType3]
from typing import Type, Union

NoneType_ = type(None)

def f(cls: Type[Union[None, int]]) -> None:
if issubclass(cls, NoneType_):
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@ghost ghost Oct 23, 2023

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One case is still broken, I believe: (python3.10+)

if issubclass(cls, types.Nonetype)

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@tyralla tyralla Oct 24, 2023

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You are right. The definition in types.pyi is not helpful. I assumed something similar to mentioned test:

NoneType = type(None)

But it is:

    @final
    class NoneType:
        def __bool__(self) -> Literal[False]: ...

My suggestion is to let ExpressionChecker.analyze_ref_expr directly return TypeType(NoneType()) when it encounters the full name "types.NoneType". (already pushed)

reveal_type(cls) # N: Revealed type is "Type[None]"
else:
reveal_type(cls) # N: Revealed type is "Type[builtins.int]"
[builtins fixtures/isinstance.pyi]