test-data/unit/check-narrowing.test

[case testNarrowingParentWithStrsBasic]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import NamedTuple, Tuple, Union
from typing_extensions import Literal, TypedDict

class Object1:
    key: Literal["A"]
    foo: int
class Object2:
    key: Literal["B"]
    bar: str

@dataclass
class Dataclass1:
    key: Literal["A"]
    foo: int
@dataclass
class Dataclass2:
    key: Literal["B"]
    foo: str

class NamedTuple1(NamedTuple):
    key: Literal["A"]
    foo: int
class NamedTuple2(NamedTuple):
    key: Literal["B"]
    foo: str

Tuple1 = Tuple[Literal["A"], int]
Tuple2 = Tuple[Literal["B"], str]

class TypedDict1(TypedDict):
    key: Literal["A"]
    foo: int
class TypedDict2(TypedDict):
    key: Literal["B"]
    foo: str

x1: Union[Object1, Object2]
if x1.key == "A":
    reveal_type(x1)         # N: Revealed type is '__main__.Object1'
    reveal_type(x1.key)     # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x1)         # N: Revealed type is '__main__.Object2'
    reveal_type(x1.key)     # N: Revealed type is 'Literal['B']'

x2: Union[Dataclass1, Dataclass2]
if x2.key == "A":
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass1'
    reveal_type(x2.key)     # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass2'
    reveal_type(x2.key)     # N: Revealed type is 'Literal['B']'

x3: Union[NamedTuple1, NamedTuple2]
if x3.key == "A":
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal['A'], builtins.int, fallback=__main__.NamedTuple1]'
    reveal_type(x3.key)     # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal['B'], builtins.str, fallback=__main__.NamedTuple2]'
    reveal_type(x3.key)     # N: Revealed type is 'Literal['B']'
if x3[0] == "A":
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal['A'], builtins.int, fallback=__main__.NamedTuple1]'
    reveal_type(x3[0])      # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal['B'], builtins.str, fallback=__main__.NamedTuple2]'
    reveal_type(x3[0])      # N: Revealed type is 'Literal['B']'

x4: Union[Tuple1, Tuple2]
if x4[0] == "A":
    reveal_type(x4)         # N: Revealed type is 'Tuple[Literal['A'], builtins.int]'
    reveal_type(x4[0])      # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x4)         # N: Revealed type is 'Tuple[Literal['B'], builtins.str]'
    reveal_type(x4[0])      # N: Revealed type is 'Literal['B']'

x5: Union[TypedDict1, TypedDict2]
if x5["key"] == "A":
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict1', {'key': Literal['A'], 'foo': builtins.int})'
else:
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict2', {'key': Literal['B'], 'foo': builtins.str})'
[builtins fixtures/primitives.pyi]

[case testNarrowingParentWithEnumsBasic]
# flags: --python-version 3.7
from enum import Enum
from dataclasses import dataclass
from typing import NamedTuple, Tuple, Union
from typing_extensions import Literal, TypedDict

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Object1:
    key: Literal[Key.A]
    foo: int
class Object2:
    key: Literal[Key.B]
    bar: str

@dataclass
class Dataclass1:
    key: Literal[Key.A]
    foo: int
@dataclass
class Dataclass2:
    key: Literal[Key.B]
    foo: str

class NamedTuple1(NamedTuple):
    key: Literal[Key.A]
    foo: int
class NamedTuple2(NamedTuple):
    key: Literal[Key.B]
    foo: str

Tuple1 = Tuple[Literal[Key.A], int]
Tuple2 = Tuple[Literal[Key.B], str]

class TypedDict1(TypedDict):
    key: Literal[Key.A]
    foo: int
class TypedDict2(TypedDict):
    key: Literal[Key.B]
    foo: str

x1: Union[Object1, Object2]
if x1.key is Key.A:
    reveal_type(x1)         # N: Revealed type is '__main__.Object1'
    reveal_type(x1.key)     # N: Revealed type is 'Literal[__main__.Key.A]'
else:
    reveal_type(x1)         # N: Revealed type is '__main__.Object2'
    reveal_type(x1.key)     # N: Revealed type is 'Literal[__main__.Key.B]'

x2: Union[Dataclass1, Dataclass2]
if x2.key is Key.A:
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass1'
    reveal_type(x2.key)     # N: Revealed type is 'Literal[__main__.Key.A]'
else:
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass2'
    reveal_type(x2.key)     # N: Revealed type is 'Literal[__main__.Key.B]'

x3: Union[NamedTuple1, NamedTuple2]
if x3.key is Key.A:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal[__main__.Key.A], builtins.int, fallback=__main__.NamedTuple1]'
    reveal_type(x3.key)     # N: Revealed type is 'Literal[__main__.Key.A]'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal[__main__.Key.B], builtins.str, fallback=__main__.NamedTuple2]'
    reveal_type(x3.key)     # N: Revealed type is 'Literal[__main__.Key.B]'
if x3[0] is Key.A:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal[__main__.Key.A], builtins.int, fallback=__main__.NamedTuple1]'
    reveal_type(x3[0])      # N: Revealed type is 'Literal[__main__.Key.A]'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[Literal[__main__.Key.B], builtins.str, fallback=__main__.NamedTuple2]'
    reveal_type(x3[0])      # N: Revealed type is 'Literal[__main__.Key.B]'

x4: Union[Tuple1, Tuple2]
if x4[0] is Key.A:
    reveal_type(x4)         # N: Revealed type is 'Tuple[Literal[__main__.Key.A], builtins.int]'
    reveal_type(x4[0])      # N: Revealed type is 'Literal[__main__.Key.A]'
else:
    reveal_type(x4)         # N: Revealed type is 'Tuple[Literal[__main__.Key.B], builtins.str]'
    reveal_type(x4[0])      # N: Revealed type is 'Literal[__main__.Key.B]'

x5: Union[TypedDict1, TypedDict2]
if x5["key"] is Key.A:
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict1', {'key': Literal[__main__.Key.A], 'foo': builtins.int})'
else:
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict2', {'key': Literal[__main__.Key.B], 'foo': builtins.str})'
[builtins fixtures/tuple.pyi]

[case testNarrowingParentWithIsInstanceBasic]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import NamedTuple, Tuple, Union
from typing_extensions import TypedDict

class Object1:
    key: int
class Object2:
    key: str

@dataclass
class Dataclass1:
    key: int
@dataclass
class Dataclass2:
    key: str

class NamedTuple1(NamedTuple):
    key: int
class NamedTuple2(NamedTuple):
    key: str

Tuple1 = Tuple[int]
Tuple2 = Tuple[str]

class TypedDict1(TypedDict):
    key: int
class TypedDict2(TypedDict):
    key: str

x1: Union[Object1, Object2]
if isinstance(x1.key, int):
    reveal_type(x1)         # N: Revealed type is '__main__.Object1'
else:
    reveal_type(x1)         # N: Revealed type is '__main__.Object2'

x2: Union[Dataclass1, Dataclass2]
if isinstance(x2.key, int):
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass1'
else:
    reveal_type(x2)         # N: Revealed type is '__main__.Dataclass2'

x3: Union[NamedTuple1, NamedTuple2]
if isinstance(x3.key, int):
    reveal_type(x3)         # N: Revealed type is 'Tuple[builtins.int, fallback=__main__.NamedTuple1]'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[builtins.str, fallback=__main__.NamedTuple2]'
if isinstance(x3[0], int):
    reveal_type(x3)         # N: Revealed type is 'Tuple[builtins.int, fallback=__main__.NamedTuple1]'
else:
    reveal_type(x3)         # N: Revealed type is 'Tuple[builtins.str, fallback=__main__.NamedTuple2]'

x4: Union[Tuple1, Tuple2]
if isinstance(x4[0], int):
    reveal_type(x4)         # N: Revealed type is 'Tuple[builtins.int]'
else:
    reveal_type(x4)         # N: Revealed type is 'Tuple[builtins.str]'

x5: Union[TypedDict1, TypedDict2]
if isinstance(x5["key"], int):
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict1', {'key': builtins.int})'
else:
    reveal_type(x5)         # N: Revealed type is 'TypedDict('__main__.TypedDict2', {'key': builtins.str})'
[builtins fixtures/isinstance.pyi]

[case testNarrowingParentMultipleKeys]
# flags: --warn-unreachable
from enum import Enum
from typing import Union
from typing_extensions import Literal

class Key(Enum):
    A = 1
    B = 2
    C = 3
    D = 4

class Object1:
    key: Literal[Key.A, Key.C]
class Object2:
    key: Literal[Key.B, Key.C]

x: Union[Object1, Object2]
if x.key is Key.A:
    reveal_type(x)  # N: Revealed type is '__main__.Object1'
else:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2]'

if x.key is Key.C:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2]'
else:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2]'

if x.key is Key.D:
    reveal_type(x)  # E: Statement is unreachable
else:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2]'
[builtins fixtures/tuple.pyi]

[case testNarrowingTypedDictParentMultipleKeys]
# flags: --warn-unreachable
from typing import Union
from typing_extensions import Literal, TypedDict

class TypedDict1(TypedDict):
    key: Literal['A', 'C']
class TypedDict2(TypedDict):
    key: Literal['B', 'C']

x: Union[TypedDict1, TypedDict2]
if x['key'] == 'A':
    reveal_type(x)  # N: Revealed type is 'TypedDict('__main__.TypedDict1', {'key': Union[Literal['A'], Literal['C']]})'
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key': Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key': Union[Literal['B'], Literal['C']]})]'

if x['key'] == 'C':
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key': Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key': Union[Literal['B'], Literal['C']]})]'
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key': Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key': Union[Literal['B'], Literal['C']]})]'

if x['key'] == 'D':
    reveal_type(x)  # E: Statement is unreachable
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key': Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key': Union[Literal['B'], Literal['C']]})]'
[builtins fixtures/primitives.pyi]

[case testNarrowingPartialTypedDictParentMultipleKeys]
# flags: --warn-unreachable
from typing import Union
from typing_extensions import Literal, TypedDict

class TypedDict1(TypedDict, total=False):
    key: Literal['A', 'C']
class TypedDict2(TypedDict, total=False):
    key: Literal['B', 'C']

x: Union[TypedDict1, TypedDict2]
if x['key'] == 'A':
    reveal_type(x)  # N: Revealed type is 'TypedDict('__main__.TypedDict1', {'key'?: Union[Literal['A'], Literal['C']]})'
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key'?: Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key'?: Union[Literal['B'], Literal['C']]})]'

if x['key'] == 'C':
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key'?: Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key'?: Union[Literal['B'], Literal['C']]})]'
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key'?: Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key'?: Union[Literal['B'], Literal['C']]})]'

if x['key'] == 'D':
    reveal_type(x)  # E: Statement is unreachable
else:
    reveal_type(x)  # N: Revealed type is 'Union[TypedDict('__main__.TypedDict1', {'key'?: Union[Literal['A'], Literal['C']]}), TypedDict('__main__.TypedDict2', {'key'?: Union[Literal['B'], Literal['C']]})]'
[builtins fixtures/primitives.pyi]

[case testNarrowingNestedTypedDicts]
from typing import Union
from typing_extensions import TypedDict, Literal

class A(TypedDict):
    key: Literal['A']
class B(TypedDict):
    key: Literal['B']
class C(TypedDict):
    key: Literal['C']

class X(TypedDict):
    inner: Union[A, B]
class Y(TypedDict):
    inner: Union[B, C]

unknown: Union[X, Y]
if unknown['inner']['key'] == 'A':
    reveal_type(unknown)            # N: Revealed type is 'TypedDict('__main__.X', {'inner': Union[TypedDict('__main__.A', {'key': Literal['A']}), TypedDict('__main__.B', {'key': Literal['B']})]})'
    reveal_type(unknown['inner'])   # N: Revealed type is 'TypedDict('__main__.A', {'key': Literal['A']})'
if unknown['inner']['key'] == 'B':
    reveal_type(unknown)            # N: Revealed type is 'Union[TypedDict('__main__.X', {'inner': Union[TypedDict('__main__.A', {'key': Literal['A']}), TypedDict('__main__.B', {'key': Literal['B']})]}), TypedDict('__main__.Y', {'inner': Union[TypedDict('__main__.B', {'key': Literal['B']}), TypedDict('__main__.C', {'key': Literal['C']})]})]'
    reveal_type(unknown['inner'])   # N: Revealed type is 'TypedDict('__main__.B', {'key': Literal['B']})'
if unknown['inner']['key'] == 'C':
    reveal_type(unknown)            # N: Revealed type is 'TypedDict('__main__.Y', {'inner': Union[TypedDict('__main__.B', {'key': Literal['B']}), TypedDict('__main__.C', {'key': Literal['C']})]})'
    reveal_type(unknown['inner'])   # N: Revealed type is 'TypedDict('__main__.C', {'key': Literal['C']})'
[builtins fixtures/primitives.pyi]

[case testNarrowingParentWithMultipleParents]
from enum import Enum
from typing import Union
from typing_extensions import Literal

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Object1:
    key: Literal[Key.A]
class Object2:
    key: Literal[Key.B]
class Object3:
    key: Literal[Key.C]
class Object4:
    key: str

x: Union[Object1, Object2, Object3, Object4]
if x.key is Key.A:
    reveal_type(x)  # N: Revealed type is '__main__.Object1'
else:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object2, __main__.Object3, __main__.Object4]'

if isinstance(x.key, str):
    reveal_type(x)  # N: Revealed type is '__main__.Object4'
else:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2, __main__.Object3]'
[builtins fixtures/isinstance.pyi]

[case testNarrowingParentsWithGenerics]
from typing import Union, TypeVar, Generic

T = TypeVar('T')
class Wrapper(Generic[T]):
    key: T

x: Union[Wrapper[int], Wrapper[str]]
if isinstance(x.key, int):
    reveal_type(x)  # N: Revealed type is '__main__.Wrapper[builtins.int]'
else:
    reveal_type(x)  # N: Revealed type is '__main__.Wrapper[builtins.str]'
[builtins fixtures/isinstance.pyi]

[case testNarrowingParentWithParentMixtures]
from enum import Enum
from typing import Union, NamedTuple
from typing_extensions import Literal, TypedDict

class Key(Enum):
    A = 1
    B = 2
    C = 3

class KeyedObject:
    key: Literal[Key.A]
class KeyedTypedDict(TypedDict):
    key: Literal[Key.B]
class KeyedNamedTuple(NamedTuple):
    key: Literal[Key.C]

ok_mixture: Union[KeyedObject, KeyedNamedTuple]
if ok_mixture.key is Key.A:
    reveal_type(ok_mixture)             # N: Revealed type is '__main__.KeyedObject'
else:
    reveal_type(ok_mixture)             # N: Revealed type is 'Tuple[Literal[__main__.Key.C], fallback=__main__.KeyedNamedTuple]'

impossible_mixture: Union[KeyedObject, KeyedTypedDict]
if impossible_mixture.key is Key.A:     # E: Item "KeyedTypedDict" of "Union[KeyedObject, KeyedTypedDict]" has no attribute "key"
    reveal_type(impossible_mixture)     # N: Revealed type is 'Union[__main__.KeyedObject, TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]})]'
else:
    reveal_type(impossible_mixture)     # N: Revealed type is 'Union[__main__.KeyedObject, TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]})]'

if impossible_mixture["key"] is Key.A:  # E: Value of type "Union[KeyedObject, KeyedTypedDict]" is not indexable
    reveal_type(impossible_mixture)     # N: Revealed type is 'Union[__main__.KeyedObject, TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]})]'
else:
    reveal_type(impossible_mixture)     # N: Revealed type is 'Union[__main__.KeyedObject, TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]})]'

weird_mixture: Union[KeyedTypedDict, KeyedNamedTuple]
if weird_mixture["key"] is Key.B:       # E: Invalid tuple index type (actual type "str", expected type "Union[int, slice]")
    reveal_type(weird_mixture)          # N: Revealed type is 'Union[TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]}), Tuple[Literal[__main__.Key.C], fallback=__main__.KeyedNamedTuple]]'
else:
    reveal_type(weird_mixture)          # N: Revealed type is 'Union[TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]}), Tuple[Literal[__main__.Key.C], fallback=__main__.KeyedNamedTuple]]'

if weird_mixture[0] is Key.B:           # E: TypedDict key must be a string literal; expected one of ('key')
    reveal_type(weird_mixture)          # N: Revealed type is 'Union[TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]}), Tuple[Literal[__main__.Key.C], fallback=__main__.KeyedNamedTuple]]'
else:
    reveal_type(weird_mixture)          # N: Revealed type is 'Union[TypedDict('__main__.KeyedTypedDict', {'key': Literal[__main__.Key.B]}), Tuple[Literal[__main__.Key.C], fallback=__main__.KeyedNamedTuple]]'
[builtins fixtures/slice.pyi]

[case testNarrowingParentWithProperties]
from enum import Enum
from typing import Union
from typing_extensions import Literal

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Object1:
    key: Literal[Key.A]

class Object2:
    @property
    def key(self) -> Literal[Key.A]: ...

class Object3:
    @property
    def key(self) -> Literal[Key.B]: ...

x: Union[Object1, Object2, Object3]
if x.key is Key.A:
    reveal_type(x)  # N: Revealed type is 'Union[__main__.Object1, __main__.Object2]'
else:
    reveal_type(x)  # N: Revealed type is '__main__.Object3'
[builtins fixtures/property.pyi]

[case testNarrowingParentWithAny]
from enum import Enum
from typing import Union, Any
from typing_extensions import Literal

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Object1:
    key: Literal[Key.A]

class Object2:
    key: Literal[Key.B]

x: Union[Object1, Object2, Any]
if x.key is Key.A:
    reveal_type(x.key)  # N: Revealed type is 'Literal[__main__.Key.A]'
    reveal_type(x)      # N: Revealed type is 'Union[__main__.Object1, Any]'
else:
    # TODO: Is this a bug? Should we skip inferring Any for singleton types?
    reveal_type(x.key)  # N: Revealed type is 'Union[Any, Literal[__main__.Key.B]]'
    reveal_type(x)      # N: Revealed type is 'Union[__main__.Object1, __main__.Object2, Any]'
[builtins fixtures/tuple.pyi]

[case testNarrowingParentsHierarchy]
from typing import Union
from typing_extensions import Literal
from enum import Enum

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Parent1:
    child: Union[Child1, Child2]
class Parent2:
    child: Union[Child2, Child3]
class Parent3:
    child: Union[Child3, Child1]

class Child1:
    main: Literal[Key.A]
    same_for_1_and_2: Literal[Key.A]
class Child2:
    main: Literal[Key.B]
    same_for_1_and_2: Literal[Key.A]
class Child3:
    main: Literal[Key.C]
    same_for_1_and_2: Literal[Key.B]

x: Union[Parent1, Parent2, Parent3]
if x.child.main is Key.A:
    reveal_type(x)          # N: Revealed type is 'Union[__main__.Parent1, __main__.Parent3]'
    reveal_type(x.child)    # N: Revealed type is '__main__.Child1'
else:
    reveal_type(x)          # N: Revealed type is 'Union[__main__.Parent1, __main__.Parent2, __main__.Parent3]'
    reveal_type(x.child)    # N: Revealed type is 'Union[__main__.Child2, __main__.Child3]'

if x.child.same_for_1_and_2 is Key.A:
    reveal_type(x)          # N: Revealed type is 'Union[__main__.Parent1, __main__.Parent2, __main__.Parent3]'
    reveal_type(x.child)    # N: Revealed type is 'Union[__main__.Child1, __main__.Child2]'
else:
    reveal_type(x)          # N: Revealed type is 'Union[__main__.Parent2, __main__.Parent3]'
    reveal_type(x.child)    # N: Revealed type is '__main__.Child3'

y: Union[Parent1, Parent2]
if y.child.main is Key.A:
    reveal_type(y)          # N: Revealed type is '__main__.Parent1'
    reveal_type(y.child)    # N: Revealed type is '__main__.Child1'
else:
    reveal_type(y)          # N: Revealed type is 'Union[__main__.Parent1, __main__.Parent2]'
    reveal_type(y.child)    # N: Revealed type is 'Union[__main__.Child2, __main__.Child3]'

if y.child.same_for_1_and_2 is Key.A:
    reveal_type(y)          # N: Revealed type is 'Union[__main__.Parent1, __main__.Parent2]'
    reveal_type(y.child)    # N: Revealed type is 'Union[__main__.Child1, __main__.Child2]'
else:
    reveal_type(y)          # N: Revealed type is '__main__.Parent2'
    reveal_type(y.child)    # N: Revealed type is '__main__.Child3'
[builtins fixtures/tuple.pyi]

[case testNarrowingParentsHierarchyGenerics]
from typing import Generic, TypeVar, Union

T = TypeVar('T')
class Model(Generic[T]):
    attr: T
class A:
    model: Model[int]
class B:
    model: Model[str]

x: Union[A, B]
if isinstance(x.model.attr, int):
    reveal_type(x)          # N: Revealed type is '__main__.A'
    reveal_type(x.model)    # N: Revealed type is '__main__.Model[builtins.int]'
else:
    reveal_type(x)          # N: Revealed type is '__main__.B'
    reveal_type(x.model)    # N: Revealed type is '__main__.Model[builtins.str]'
[builtins fixtures/isinstance.pyi]

[case testNarrowingParentsHierarchyTypedDict]
# flags: --warn-unreachable
from typing import Union
from typing_extensions import TypedDict, Literal
from enum import Enum

class Key(Enum):
    A = 1
    B = 2
    C = 3

class Parent1(TypedDict):
    model: Model1
    foo: int

class Parent2(TypedDict):
    model: Model2
    bar: str

class Model1(TypedDict):
    key: Literal[Key.A]

class Model2(TypedDict):
    key: Literal[Key.B]

x: Union[Parent1, Parent2]
if x["model"]["key"] is Key.A:
    reveal_type(x)              # N: Revealed type is 'TypedDict('__main__.Parent1', {'model': TypedDict('__main__.Model1', {'key': Literal[__main__.Key.A]}), 'foo': builtins.int})'
    reveal_type(x["model"])     # N: Revealed type is 'TypedDict('__main__.Model1', {'key': Literal[__main__.Key.A]})'
else:
    reveal_type(x)              # N: Revealed type is 'TypedDict('__main__.Parent2', {'model': TypedDict('__main__.Model2', {'key': Literal[__main__.Key.B]}), 'bar': builtins.str})'
    reveal_type(x["model"])     # N: Revealed type is 'TypedDict('__main__.Model2', {'key': Literal[__main__.Key.B]})'

y: Union[Parent1, Parent2]
if y["model"]["key"] is Key.C:
    reveal_type(y)              # E: Statement is unreachable
    reveal_type(y["model"])
else:
    reveal_type(y)              # N: Revealed type is 'Union[TypedDict('__main__.Parent1', {'model': TypedDict('__main__.Model1', {'key': Literal[__main__.Key.A]}), 'foo': builtins.int}), TypedDict('__main__.Parent2', {'model': TypedDict('__main__.Model2', {'key': Literal[__main__.Key.B]}), 'bar': builtins.str})]'
    reveal_type(y["model"])     # N: Revealed type is 'Union[TypedDict('__main__.Model1', {'key': Literal[__main__.Key.A]}), TypedDict('__main__.Model2', {'key': Literal[__main__.Key.B]})]'
[builtins fixtures/tuple.pyi]

[case testNarrowingParentsHierarchyTypedDictWithStr]
# flags: --warn-unreachable
from typing import Union
from typing_extensions import TypedDict, Literal

class Parent1(TypedDict):
    model: Model1
    foo: int

class Parent2(TypedDict):
    model: Model2
    bar: str

class Model1(TypedDict):
    key: Literal['A']

class Model2(TypedDict):
    key: Literal['B']

x: Union[Parent1, Parent2]
if x["model"]["key"] == 'A':
    reveal_type(x)              # N: Revealed type is 'TypedDict('__main__.Parent1', {'model': TypedDict('__main__.Model1', {'key': Literal['A']}), 'foo': builtins.int})'
    reveal_type(x["model"])     # N: Revealed type is 'TypedDict('__main__.Model1', {'key': Literal['A']})'
else:
    reveal_type(x)              # N: Revealed type is 'TypedDict('__main__.Parent2', {'model': TypedDict('__main__.Model2', {'key': Literal['B']}), 'bar': builtins.str})'
    reveal_type(x["model"])     # N: Revealed type is 'TypedDict('__main__.Model2', {'key': Literal['B']})'

y: Union[Parent1, Parent2]
if y["model"]["key"] == 'C':
    reveal_type(y)              # E: Statement is unreachable
    reveal_type(y["model"])
else:
    reveal_type(y)              # N: Revealed type is 'Union[TypedDict('__main__.Parent1', {'model': TypedDict('__main__.Model1', {'key': Literal['A']}), 'foo': builtins.int}), TypedDict('__main__.Parent2', {'model': TypedDict('__main__.Model2', {'key': Literal['B']}), 'bar': builtins.str})]'
    reveal_type(y["model"])     # N: Revealed type is 'Union[TypedDict('__main__.Model1', {'key': Literal['A']}), TypedDict('__main__.Model2', {'key': Literal['B']})]'
[builtins fixtures/primitives.pyi]

[case testNarrowingEqualityFlipFlop]
# flags: --warn-unreachable --strict-equality
from typing_extensions import Literal, Final
from enum import Enum

class State(Enum):
    A = 1
    B = 2

class FlipFlopEnum:
    def __init__(self) -> None:
        self.state = State.A

    def mutate(self) -> None:
        self.state = State.B if self.state == State.A else State.A

class FlipFlopStr:
    def __init__(self) -> None:
        self.state = "state-1"

    def mutate(self) -> None:
        self.state = "state-2" if self.state == "state-1" else "state-1"

def test1(switch: FlipFlopEnum) -> None:
    # Naively, we might assume the 'assert' here would narrow the type to
    # Literal[State.A]. However, doing this ends up breaking a fair number of real-world
    # code (usually test cases) that looks similar to this function: e.g. checks
    # to make sure a field was mutated to some particular value.
    #
    # And since mypy can't really reason about state mutation, we take a conservative
    # approach and avoid narrowing anything here.

    assert switch.state == State.A
    reveal_type(switch.state)          # N: Revealed type is '__main__.State'

    switch.mutate()

    assert switch.state == State.B
    reveal_type(switch.state)          # N: Revealed type is '__main__.State'

def test2(switch: FlipFlopEnum) -> None:
    # So strictly speaking, we ought to do the same thing with 'is' comparisons
    # for the same reasons as above. But in practice, not too many people seem to
    # know that doing 'some_enum is MyEnum.Value' is idiomatic. So in practice,
    # this is probably good enough for now.

    assert switch.state is State.A
    reveal_type(switch.state)          # N: Revealed type is 'Literal[__main__.State.A]'

    switch.mutate()

    assert switch.state is State.B     # E: Non-overlapping identity check (left operand type: "Literal[State.A]", right operand type: "Literal[State.B]")
    reveal_type(switch.state)          # E: Statement is unreachable

def test3(switch: FlipFlopStr) -> None:
    # This is the same thing as 'test1', except we try using str literals.

    assert switch.state == "state-1"
    reveal_type(switch.state)          # N: Revealed type is 'builtins.str'

    switch.mutate()

    assert switch.state == "state-2"
    reveal_type(switch.state)          # N: Revealed type is 'builtins.str'
[builtins fixtures/primitives.pyi]

[case testNarrowingEqualityRequiresExplicitStrLiteral]
# flags: --strict-optional
from typing_extensions import Literal, Final

A_final: Final = "A"
A_literal: Literal["A"]

# Neither the LHS nor the RHS are explicit literals, so regrettably nothing
# is narrowed here -- see 'testNarrowingEqualityFlipFlop' for an example of
# why more precise inference here is problematic.
x_str: str
if x_str == "A":
    reveal_type(x_str)  # N: Revealed type is 'builtins.str'
else:
    reveal_type(x_str)  # N: Revealed type is 'builtins.str'
reveal_type(x_str)      # N: Revealed type is 'builtins.str'

if x_str == A_final:
    reveal_type(x_str)  # N: Revealed type is 'builtins.str'
else:
    reveal_type(x_str)  # N: Revealed type is 'builtins.str'
reveal_type(x_str)      # N: Revealed type is 'builtins.str'

# But the RHS is a literal, so we can at least narrow the 'if' case now.
if x_str == A_literal:
    reveal_type(x_str)  # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x_str)  # N: Revealed type is 'builtins.str'
reveal_type(x_str)      # N: Revealed type is 'builtins.str'

# But in these two cases, the LHS is a literal/literal-like type. So we
# assume the user *does* want literal-based narrowing and narrow accordingly
# regardless of whether the RHS is an explicit literal or not.
x_union: Literal["A", "B", None]
if x_union == A_final:
    reveal_type(x_union)  # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x_union)  # N: Revealed type is 'Union[Literal['B'], None]'
reveal_type(x_union)      # N: Revealed type is 'Union[Literal['A'], Literal['B'], None]'

if x_union == A_literal:
    reveal_type(x_union)  # N: Revealed type is 'Literal['A']'
else:
    reveal_type(x_union)  # N: Revealed type is 'Union[Literal['B'], None]'
reveal_type(x_union)      # N: Revealed type is 'Union[Literal['A'], Literal['B'], None]'
[builtins fixtures/primitives.pyi]

[case testNarrowingEqualityRequiresExplicitEnumLiteral]
# flags: --strict-optional
from typing_extensions import Literal, Final
from enum import Enum

class Foo(Enum):
    A = 1
    B = 2

A_final: Final = Foo.A
A_literal: Literal[Foo.A]

# See comments in testNarrowingEqualityRequiresExplicitStrLiteral and
# testNarrowingEqualityFlipFlop for more on why we can't narrow here.
x1: Foo
if x1 == Foo.A:
    reveal_type(x1)  # N: Revealed type is '__main__.Foo'
else:
    reveal_type(x1)  # N: Revealed type is '__main__.Foo'

x2: Foo
if x2 == A_final:
    reveal_type(x2)  # N: Revealed type is '__main__.Foo'
else:
    reveal_type(x2)  # N: Revealed type is '__main__.Foo'

# But we let this narrow since there's an explicit literal in the RHS.
x3: Foo
if x3 == A_literal:
    reveal_type(x3)  # N: Revealed type is 'Literal[__main__.Foo.A]'
else:
    reveal_type(x3)  # N: Revealed type is 'Literal[__main__.Foo.B]'
[builtins fixtures/primitives.pyi]

[case testNarrowingEqualityDisabledForCustomEquality]
from typing import Union
from typing_extensions import Literal
from enum import Enum

class Custom:
    def __eq__(self, other: object) -> bool: return True

class Default: pass

x1: Union[Custom, Literal[1], Literal[2]]
if x1 == 1:
    reveal_type(x1)  # N: Revealed type is 'Union[__main__.Custom, Literal[1], Literal[2]]'
else:
    reveal_type(x1)  # N: Revealed type is 'Union[__main__.Custom, Literal[1], Literal[2]]'

x2: Union[Default, Literal[1], Literal[2]]
if x2 == 1:
    reveal_type(x2)  # N: Revealed type is 'Literal[1]'
else:
    reveal_type(x2)  # N: Revealed type is 'Union[__main__.Default, Literal[2]]'

class CustomEnum(Enum):
    A = 1
    B = 2

    def __eq__(self, other: object) -> bool: return True

x3: CustomEnum
key: Literal[CustomEnum.A]
if x3 == key:
    reveal_type(x3)  # N: Revealed type is '__main__.CustomEnum'
else:
    reveal_type(x3)  # N: Revealed type is '__main__.CustomEnum'

# For comparison, this narrows since we bypass __eq__
if x3 is key:
    reveal_type(x3)  # N: Revealed type is 'Literal[__main__.CustomEnum.A]'
else:
    reveal_type(x3)  # N: Revealed type is 'Literal[__main__.CustomEnum.B]'
[builtins fixtures/primitives.pyi]

[case testNarrowingEqualityDisabledForCustomEqualityChain]
# flags: --strict-optional --strict-equality --warn-unreachable
from typing import Union
from typing_extensions import Literal

class Custom:
    def __eq__(self, other: object) -> bool: return True

class Default: pass

x: Literal[1, 2, None]
y: Custom
z: Default

# We could maybe try doing something clever, but for simplicity we
# treat the whole chain as contaminated and mostly disable narrowing.
#
# The only exception is that we do at least strip away the 'None'. We
# (perhaps optimistically) assume no custom class would be pathological
# enough to declare itself to be equal to None and so permit this narrowing,
# since it's often convenient in practice.
if 1 == x == y:
    reveal_type(x)   # N: Revealed type is 'Union[Literal[1], Literal[2]]'
    reveal_type(y)   # N: Revealed type is '__main__.Custom'
else:
    reveal_type(x)   # N: Revealed type is 'Union[Literal[1], Literal[2], None]'
    reveal_type(y)   # N: Revealed type is '__main__.Custom'

# No contamination here
if 1 == x == z:      # E: Non-overlapping equality check (left operand type: "Union[Literal[1], Literal[2], None]", right operand type: "Default")
    reveal_type(x)   # E: Statement is unreachable
    reveal_type(z)
else:
    reveal_type(x)   # N: Revealed type is 'Union[Literal[1], Literal[2], None]'
    reveal_type(z)   # N: Revealed type is '__main__.Default'
[builtins fixtures/primitives.pyi]

[case testNarrowingUnreachableCases]
# flags: --strict-optional --strict-equality --warn-unreachable
from typing import Union
from typing_extensions import Literal

a: Literal[1]
b: Literal[1, 2]
c: Literal[2, 3]

if a == b == c:
    reveal_type(a)  # E: Statement is unreachable
    reveal_type(b)
    reveal_type(c)
else:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
    reveal_type(b)  # N: Revealed type is 'Union[Literal[1], Literal[2]]'
    reveal_type(c)  # N: Revealed type is 'Union[Literal[2], Literal[3]]'

if a == a == a:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
else:
    reveal_type(a)  # E: Statement is unreachable

if a == a == b:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
    reveal_type(b)  # N: Revealed type is 'Literal[1]'
else:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
    reveal_type(b)  # N: Revealed type is 'Literal[2]'

# In this case, it's ok for 'b' to narrow down to Literal[1] in the else case
# since that's the only way 'b == 2' can be false
if b == 2:
    reveal_type(b)  # N: Revealed type is 'Literal[2]'
else:
    reveal_type(b)  # N: Revealed type is 'Literal[1]'

# But in this case, we can't conclude anything about the else case. This expression
# could end up being either '2 == 2 == 3' or '1 == 2 == 2', which means we can't
# conclude anything.
if b == 2 == c:
    reveal_type(b)  # N: Revealed type is 'Literal[2]'
    reveal_type(c)  # N: Revealed type is 'Literal[2]'
else:
    reveal_type(b)  # N: Revealed type is 'Union[Literal[1], Literal[2]]'
    reveal_type(c)  # N: Revealed type is 'Union[Literal[2], Literal[3]]'
[builtins fixtures/primitives.pyi]

[case testNarrowingUnreachableCases2]
# flags: --strict-optional --strict-equality --warn-unreachable
from typing import Union
from typing_extensions import Literal

a: Literal[1, 2, 3, 4]
b: Literal[1, 2, 3, 4]

if a == b == 1:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
    reveal_type(b)  # N: Revealed type is 'Literal[1]'
elif a == b == 2:
    reveal_type(a)  # N: Revealed type is 'Literal[2]'
    reveal_type(b)  # N: Revealed type is 'Literal[2]'
elif a == b == 3:
    reveal_type(a)  # N: Revealed type is 'Literal[3]'
    reveal_type(b)  # N: Revealed type is 'Literal[3]'
elif a == b == 4:
    reveal_type(a)  # N: Revealed type is 'Literal[4]'
    reveal_type(b)  # N: Revealed type is 'Literal[4]'
else:
    # This branch is reachable if a == 1 and b == 2, for example.
    reveal_type(a)  # N: Revealed type is 'Union[Literal[1], Literal[2], Literal[3], Literal[4]]'
    reveal_type(b)  # N: Revealed type is 'Union[Literal[1], Literal[2], Literal[3], Literal[4]]'

if a == a == 1:
    reveal_type(a)  # N: Revealed type is 'Literal[1]'
elif a == a == 2:
    reveal_type(a)  # N: Revealed type is 'Literal[2]'
elif a == a == 3:
    reveal_type(a)  # N: Revealed type is 'Literal[3]'
elif a == a == 4:
    reveal_type(a)  # N: Revealed type is 'Literal[4]'
else:
    # In contrast, this branch must be unreachable: we assume (maybe naively)
    # that 'a' won't be mutated in the middle of the expression.
    reveal_type(a)  # E: Statement is unreachable
    reveal_type(b)
[builtins fixtures/primitives.pyi]

[case testNarrowingLiteralTruthiness]
from typing import Union
from typing_extensions import Literal

str_or_false: Union[Literal[False], str]

if str_or_false:
    reveal_type(str_or_false)   # N: Revealed type is 'builtins.str'
else:
    reveal_type(str_or_false)   # N: Revealed type is 'Union[Literal[False], builtins.str]'

true_or_false: Literal[True, False]

if true_or_false:
    reveal_type(true_or_false)  # N: Revealed type is 'Literal[True]'
else:
    reveal_type(true_or_false)  # N: Revealed type is 'Literal[False]'
[builtins fixtures/primitives.pyi]

[case testNarrowingLiteralIdentityCheck]
from typing import Union
from typing_extensions import Literal

str_or_false: Union[Literal[False], str]

if str_or_false is not False:
    reveal_type(str_or_false)   # N: Revealed type is 'builtins.str'
else:
    reveal_type(str_or_false)   # N: Revealed type is 'Literal[False]'

if str_or_false is False:
    reveal_type(str_or_false)  # N: Revealed type is 'Literal[False]'
else:
    reveal_type(str_or_false)  # N: Revealed type is 'builtins.str'

str_or_true: Union[Literal[True], str]

if str_or_true is True:
    reveal_type(str_or_true)  # N: Revealed type is 'Literal[True]'
else:
    reveal_type(str_or_true)  # N: Revealed type is 'builtins.str'

if str_or_true is not True:
    reveal_type(str_or_true)  # N: Revealed type is 'builtins.str'
else:
    reveal_type(str_or_true)  # N: Revealed type is 'Literal[True]'

str_or_bool_literal: Union[Literal[False], Literal[True], str]

if str_or_bool_literal is not True:
    reveal_type(str_or_bool_literal)  # N: Revealed type is 'Union[Literal[False], builtins.str]'
else:
    reveal_type(str_or_bool_literal)  # N: Revealed type is 'Literal[True]'

if str_or_bool_literal is not True and str_or_bool_literal is not False:
    reveal_type(str_or_bool_literal)  # N: Revealed type is 'builtins.str'
else:
    reveal_type(str_or_bool_literal)  # N: Revealed type is 'Union[Literal[False], Literal[True]]'

[builtins fixtures/primitives.pyi]