check-inference.test

-- Inferring locals/globals with simple types
-- ------------------------------------------


[case testInferSimpleGvarType]
class A: pass
class B: pass

x = A()
y = B()
if int():
    x = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    x = A()
if int():
    x = y   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    x = x
[case testInferSimpleLvarType]
import typing
def f() -> None:
    x = A()
    y = B()
    if int():
        x = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        x = A()
        x = y   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        x = x
class A: pass
class B: pass
[out]

[case testLvarInitializedToVoid]
import typing
def f() -> None:
    a = g()    # E: "g" does not return a value (it only ever returns None)
    #b, c = g() # "g" does not return a value (it only ever returns None) TODO

def g() -> None: pass
[out]

[case testInferringLvarTypeFromArgument]
import typing
def f(a: 'A') -> None:
    b = a
    if int():
        b = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = a
        a = b

class A: pass
class B: pass
[out]

[case testInferringLvarTypeFromGvar]

g: B

def f() -> None:
    a = g
    if int():
        a = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")
        a = B()

class A: pass
class B: pass
[out]

[case testInferringImplicitDynamicTypeForLvar]
import typing
def f() -> None:
    a = g()
    None(a) # E: "None" not callable
    a.x()

def g(): pass
[out]

[case testInferringExplicitDynamicTypeForLvar]
from typing import Any
g: Any

def f(a: Any) -> None:
    b = g
    None(b) # E: "None" not callable
    a.x()
[out]


-- Inferring types of local variables with complex types
-- -----------------------------------------------------


[case testInferringTupleTypeForLvar]

def f() -> None:
    a = A(), B()
    aa: A
    bb: B
    if int():
        bb = a[0] # E: Incompatible types in assignment (expression has type "A", variable has type "B")
        aa = a[1] # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        aa = a[0]
        bb = a[1]

class A: pass
class B: pass
[builtins fixtures/tuple.pyi]
[out]

[case testInferringTupleTypeForLvarWithNones]
import typing
def f() -> None:
    a = A(), None
    b = None, A()

class A: pass
[builtins fixtures/tuple.pyi]
[out]

[case testInferringGenericTypeForLvar]
from typing import TypeVar, Generic
T = TypeVar('T')
class A(Generic[T]): pass
a_i: A[int]
a_s: A[str]

def f() -> None:
    a_int = A() # type: A[int]
    a = a_int
    if int():
        a = a_s # E: Incompatible types in assignment (expression has type "A[str]", variable has type "A[int]")
        a = a_i
[builtins fixtures/tuple.pyi]
[out]

[case testInferringFunctionTypeForLvar]
import typing
def f() -> None:
    a = g
    a(B()) # E: Argument 1 has incompatible type "B"; expected "A"
    a(A())

def g(a: 'A') -> None: pass

class A: pass
class B: pass
[out]

[case testInferringFunctionTypeForLvarFromTypeObject]
import typing
def f() -> None:
    a = A
    a(A()) # E: Too many arguments
    a()
    t = a # type: type

class A: pass
[out]


-- Inferring variable types in multiple definition
-- -----------------------------------------------


[case testInferringLvarTypesInMultiDef]
import typing
def f() -> None:
    a, b = A(), B()
    if int():
        a = b   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")

        a = A()
        b = B()

class A: pass
class B: pass
[out]

[case testInferringLvarTypesInTupleAssignment]
from typing import Tuple
def f() -> None:
    t: Tuple[A, B]
    a, b = t
    if int():
        a = b   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")

        a = A()
        b = B()

class A: pass
class B: pass
[builtins fixtures/tuple.pyi]
[out]

[case testInferringLvarTypesInNestedTupleAssignment1]
from typing import Tuple
def f() -> None:
    t: Tuple[A, B]
    a1, (a, b) = A(), t
    if int():
        a = b   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")

        a = A()
        b = B()

class A: pass
class B: pass
[builtins fixtures/tuple.pyi]
[out]

[case testInferringLvarTypesInNestedTupleAssignment2]
import typing
def f() -> None:
    a, (b, c) = A(), (B(), C())
    if int():
        a = b   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")
        c = A() # E: Incompatible types in assignment (expression has type "A", variable has type "C")

        a = A()
        b = B()
        c = C()

class A: pass
class B: pass
class C: pass
[out]

[case testInferringLvarTypesInNestedListAssignment]
import typing
def f() -> None:
    a, (b, c) = A(), [B(), C()]
    if int():
        a = b   # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
        b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")
        c = A() # E: Incompatible types in assignment (expression has type "A", variable has type "C")

        a = A()
        b = B()
        c = C()

class A: pass
class B: pass
class C: pass
[out]

[case testInferringLvarTypesInMultiDefWithNoneTypes]
import typing
def f() -> None:
    a, b = A(), None
    c, d = None, A()

class A: pass
[out]

[case testInferringLvarTypesInNestedTupleAssignmentWithNoneTypes]
import typing
def f() -> None:
    a1, (a2, b) = A(), (A(), None)

class A: pass
[out]

[case testClassObjectsNotUnpackableWithoutIterableMetaclass]
from typing import Type

class Foo: ...
A: Type[Foo] = Foo
a, b = Foo  # E: "Type[Foo]" object is not iterable
c, d = A  # E: "Type[Foo]" object is not iterable

class Meta(type): ...
class Bar(metaclass=Meta): ...
B: Type[Bar] = Bar
e, f = Bar  # E: "Type[Bar]" object is not iterable
g, h = B  # E: "Type[Bar]" object is not iterable

reveal_type(a)  # E: Cannot determine type of "a"  # N: Revealed type is "Any"
reveal_type(b)  # E: Cannot determine type of "b"  # N: Revealed type is "Any"
reveal_type(c)  # E: Cannot determine type of "c"  # N: Revealed type is "Any"
reveal_type(d)  # E: Cannot determine type of "d"  # N: Revealed type is "Any"
reveal_type(e)  # E: Cannot determine type of "e"  # N: Revealed type is "Any"
reveal_type(f)  # E: Cannot determine type of "f"  # N: Revealed type is "Any"
reveal_type(g)  # E: Cannot determine type of "g"  # N: Revealed type is "Any"
reveal_type(h)  # E: Cannot determine type of "h"  # N: Revealed type is "Any"
[out]

[case testInferringLvarTypesUnpackedFromIterableClassObject]
from typing import Iterator, Type, TypeVar, Union, overload
class Meta(type):
    def __iter__(cls) -> Iterator[int]:
        yield from [1, 2, 3]

class Meta2(type):
    def __iter__(cls) -> Iterator[str]:
        yield from ["foo", "bar", "baz"]

class Meta3(type): ...

class Foo(metaclass=Meta): ...
class Bar(metaclass=Meta2): ...
class Baz(metaclass=Meta3): ...
class Spam: ...

class Eggs(metaclass=Meta):
    @overload
    def __init__(self, x: int) -> None: ...
    @overload
    def __init__(self, x: int, y: int, z: int) -> None: ...
    def __init__(self, x: int, y: int = ..., z: int = ...) -> None: ...

A: Type[Foo] = Foo
B: Type[Union[Foo, Bar]] = Foo
C: Union[Type[Foo], Type[Bar]] = Foo
D: Type[Union[Foo, Baz]] = Foo
E: Type[Union[Foo, Spam]] = Foo
F: Type[Eggs] = Eggs
G: Type[Union[Foo, Eggs]] = Foo

a, b, c = Foo
d, e, f = A
g, h, i = B
j, k, l = C
m, n, o = D  # E: "Type[Baz]" object is not iterable
p, q, r = E  # E: "Type[Spam]" object is not iterable
s, t, u = Eggs
v, w, x = F
y, z, aa = G

for var in [a, b, c, d, e, f, s, t, u, v, w, x, y, z, aa]:
    reveal_type(var)  # N: Revealed type is "builtins.int"

for var2 in [g, h, i, j, k, l]:
    reveal_type(var2)  # N: Revealed type is "Union[builtins.int, builtins.str]"

for var3 in [m, n, o, p, q, r]:
    reveal_type(var3)  # N: Revealed type is "Union[builtins.int, Any]"

T = TypeVar("T", bound=Type[Foo])

def check(x: T) -> T:
    a, b, c = x
    for var in [a, b, c]:
        reveal_type(var)  # N: Revealed type is "builtins.int"
    return x

T2 = TypeVar("T2", bound=Type[Union[Foo, Bar]])

def check2(x: T2) -> T2:
    a, b, c = x
    for var in [a, b, c]:
        reveal_type(var)  # N: Revealed type is "Union[builtins.int, builtins.str]"
    return x

T3 = TypeVar("T3", bound=Union[Type[Foo], Type[Bar]])

def check3(x: T3) -> T3:
    a, b, c = x
    for var in [a, b, c]:
        reveal_type(var)  # N: Revealed type is "Union[builtins.int, builtins.str]"
    return x
[out]

[case testInferringLvarTypesUnpackedFromIterableClassObjectWithGenericIter]
from typing import Iterator, Type, TypeVar

T = TypeVar("T")
class Meta(type):
    def __iter__(self: Type[T]) -> Iterator[T]: ...
class Foo(metaclass=Meta): ...

A, B, C = Foo
reveal_type(A)  # N: Revealed type is "__main__.Foo"
reveal_type(B)  # N: Revealed type is "__main__.Foo"
reveal_type(C)  # N: Revealed type is "__main__.Foo"
[out]

[case testInferringLvarTypesInMultiDefWithInvalidTuple]
from typing import Tuple
t: Tuple[object, object, object]

def f() -> None:
    a, b = t         # Fail
    c, d, e, f = t   # Fail
    g, h, i = t
[builtins fixtures/tuple.pyi]
[out]
main:5: error: Too many values to unpack (2 expected, 3 provided)
main:6: error: Need more than 3 values to unpack (4 expected)

[case testInvalidRvalueTypeInInferredMultipleLvarDefinition]
import typing
def f() -> None:
    a, b = f   # E: "Callable[[], None]" object is not iterable
    c, d = A() # E: "A" object is not iterable
class A: pass
[builtins fixtures/for.pyi]
[out]

[case testInvalidRvalueTypeInInferredNestedTupleAssignment]
import typing
def f() -> None:
    a1, (a2, b) = A(), f   # E: "Callable[[], None]" object is not iterable
    a3, (c, d) = A(), A() # E: "A" object is not iterable
class A: pass
[builtins fixtures/for.pyi]
[out]

[case testInferringMultipleLvarDefinitionWithListRvalue]
from typing import List

class C: pass
class D: pass

def f() -> None:
    list_c = [C()]
    list_d = [D()]
    a, b = list_c
    c, d, e = list_d
    if int():
        a = D() # E: Incompatible types in assignment (expression has type "D", variable has type "C")
        b = D() # E: Incompatible types in assignment (expression has type "D", variable has type "C")
        c = C() # E: Incompatible types in assignment (expression has type "C", variable has type "D")
        b = c   # E: Incompatible types in assignment (expression has type "D", variable has type "C")

        a = C()
        b = C()
        c = D()
        d = D()
        e = D()

        a = b
        c = d
        d = e
[builtins fixtures/for.pyi]
[out]

[case testInferringNestedTupleAssignmentWithListRvalue]
from typing import List

class C: pass
class D: pass

def f() -> None:
    list_c = [C()]
    list_d = [D()]
    c1, (a, b) = C(), list_c
    c2, (c, d, e) = C(), list_d
    if int():
        a = D() # E: Incompatible types in assignment (expression has type "D", variable has type "C")
        b = D() # E: Incompatible types in assignment (expression has type "D", variable has type "C")
        c = C() # E: Incompatible types in assignment (expression has type "C", variable has type "D")
        b = c   # E: Incompatible types in assignment (expression has type "D", variable has type "C")

        a = C()
        b = C()
        c = D()
        d = D()
        e = D()

        a = b
        c = d
        d = e
[builtins fixtures/for.pyi]
[out]

[case testInferringMultipleLvarDefinitionWithImplicitDynamicRvalue]
import typing
def f() -> None:
    a, b = g()
    a.x
    b.x
def g(): pass

[case testInferringMultipleLvarDefinitionWithExplicitDynamicRvalue]
from typing import Any
def f(d: Any) -> None:
    a, b = d
    a.x
    b.x

[case testInferringTypesFromIterable]
from typing import Iterable
class Nums(Iterable[int]):
    def __iter__(self): pass
    def __next__(self): pass
a, b = Nums()
reveal_type(a)  # N: Revealed type is "builtins.int"
reveal_type(b)  # N: Revealed type is "builtins.int"
if int():
    a = b = 1
if int():
    a = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
if int():
    b = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[builtins fixtures/for.pyi]

[case testInferringTypesFromIterableStructuralSubtyping1]
from typing import Iterator
class Nums:
    def __iter__(self) -> Iterator[int]: pass
a, b = Nums()
reveal_type(a)  # N: Revealed type is "builtins.int"
reveal_type(b)  # N: Revealed type is "builtins.int"
if int():
    a = b = 1
if int():
    a = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
if int():
    b = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[builtins fixtures/for.pyi]

[case testInferringTypesFromIterableStructuralSubtyping2]
from typing import Self
class Nums:
    def __iter__(self) -> Self: pass
    def __next__(self) -> int: pass
a, b = Nums()
reveal_type(a)  # N: Revealed type is "builtins.int"
reveal_type(b)  # N: Revealed type is "builtins.int"
if int():
    a = b = 1
if int():
    a = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
if int():
    b = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[builtins fixtures/tuple.pyi]


-- Type variable inference for generic functions
-- ---------------------------------------------


[case testInferSimpleGenericFunction]
from typing import Tuple, TypeVar
T = TypeVar('T')
a: A
b: B
c: Tuple[A, object]

def id(a: T) -> T: pass

if int():
    b = id(a) # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    a = id(b) # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    a = id(c) # E: Incompatible types in assignment (expression has type "Tuple[A, object]", variable has type "A")

if int():
    a = id(a)
    b = id(b)
    c = id(c)

class A: pass
class B: pass
[builtins fixtures/tuple.pyi]

[case testInferringGenericFunctionTypeForLvar]
from typing import TypeVar
T = TypeVar('T')
def f() -> None:
    a = id
    b: int
    c: str
    if int():
        b = a(c) # E: Incompatible types in assignment (expression has type "str", variable has type "int")
        b = a(b)
        c = a(c)
def id(x: T) -> T:
    return x
[out]

[case testUnderspecifiedInferenceResult]
# flags: --no-strict-optional
from typing import TypeVar
T = TypeVar('T')
class A: pass
a: A

def ff() -> None:
    x = f() # E: Need type annotation for "x"
    reveal_type(x) # N: Revealed type is "Any"

def f() -> T: pass # E: A function returning TypeVar should receive at least one argument containing the same TypeVar
def g(a: T) -> None: pass

g(None) # Ok
f()     # Ok because not used to infer local variable type
g(a)
[out]

[case testInferenceWithMultipleConstraints]
from typing import TypeVar

class A: pass
class B(A): pass

T = TypeVar('T')
a: A
b: B

def f(a: T, b: T) -> T: pass

if int():
    b = f(a, b) # E: Incompatible types in assignment (expression has type "A", variable has type "B")
if int():
    b = f(b, a) # E: Incompatible types in assignment (expression has type "A", variable has type "B")
if int():
    a = f(a, b)
if int():
    a = f(b, a)

[case testInferenceWithMultipleVariables]
from typing import Tuple, TypeVar
T = TypeVar('T')
S = TypeVar('S')

def f(a: T, b: S) -> Tuple[T, S]: pass

class A: pass
class B: pass

a: A
b: B
taa: Tuple[A, A]
tab: Tuple[A, B]
tba: Tuple[B, A]

if int():
    taa = f(a, b) # E: Argument 2 to "f" has incompatible type "B"; expected "A"
if int():
    taa = f(b, a) # E: Argument 1 to "f" has incompatible type "B"; expected "A"
if int():
    tba = f(a, b) # E: Argument 1 to "f" has incompatible type "A"; expected "B" \
                  # E: Argument 2 to "f" has incompatible type "B"; expected "A"

if int():
    tab = f(a, b)
if int():
    tba = f(b, a)
[builtins fixtures/tuple.pyi]

[case testConstraintSolvingWithSimpleGenerics]
from typing import TypeVar, Generic
T = TypeVar('T')
ao: A[object]
ab: A[B]
ac: A[C]

def f(a: 'A[T]') -> 'A[T]': pass

def g(a: T) -> T: pass

class A(Generic[T]): pass
class B: pass
class C: pass

if int():
    ab = f(ao) # E: Argument 1 to "f" has incompatible type "A[object]"; expected "A[B]"
    ao = f(ab) # E: Argument 1 to "f" has incompatible type "A[B]"; expected "A[object]"
if int():
    ab = f(ac) # E: Argument 1 to "f" has incompatible type "A[C]"; expected "A[B]"
if int():
    ab = g(ao) # E: Argument 1 to "g" has incompatible type "A[object]"; expected "A[B]"
    ao = g(ab) # E: Argument 1 to "g" has incompatible type "A[B]"; expected "A[object]"

if int():
    ab = f(ab)
    ac = f(ac)
    ao = f(ao)

if int():
    ab = g(ab)
    ao = g(ao)
[case testConstraintSolvingFailureWithSimpleGenerics]
from typing import TypeVar, Generic
T = TypeVar('T')
ao: A[object]
ab: A[B]

def f(a: 'A[T]', b: 'A[T]') -> None: pass

class A(Generic[T]): pass
class B: pass


f(ao, ab) # E: Cannot infer type argument 1 of "f"
f(ab, ao) # E: Cannot infer type argument 1 of "f"
f(ao, ao)
f(ab, ab)

[case testTypeInferenceWithCalleeDefaultArgs]
# flags: --no-strict-optional
from typing import TypeVar
T = TypeVar('T')
a = None # type: A
o = None # type: object

def f(a: T = None) -> T: pass
def g(a: T, b: T = None) -> T: pass

class A: pass

if int():
    a = f(o)    # E: Incompatible types in assignment (expression has type "object", variable has type "A")
if int():
    a = g(a, o) # E: Incompatible types in assignment (expression has type "object", variable has type "A")

if int():
    o = f()
if int():
    o = f(o)
if int():
    a = f(a)
if int():
    a = g(a)


-- Generic function inference with multiple inheritance
-- ----------------------------------------------------


[case testGenericFunctionInferenceWithMultipleInheritance]
from typing import TypeVar

class I: pass
class J: pass

class A(I, J): pass
class B(I, J): pass
class C(I): pass
class D(J): pass

T = TypeVar('T')
def f(a: T, b: T) -> T: pass
def g(x: I) -> None: pass

a = f(A(), C())
g(a)
b = f(A(), B())
g(b)
c = f(A(), D())
g(c) # E: Argument 1 to "g" has incompatible type "J"; expected "I"
d = f(D(), A())
g(d) # E: Argument 1 to "g" has incompatible type "J"; expected "I"
e = f(D(), C())
g(e) # E: Argument 1 to "g" has incompatible type "object"; expected "I"

[case testGenericFunctionInferenceWithMultipleInheritance2]
from typing import TypeVar

class I: pass
class J: pass

class A(I): pass
class B(A, J): pass
class C(I, J): pass

T = TypeVar('T')
def f(a: T, b: T) -> T: pass
def g(x: I) -> None: pass
def h(x: J) -> None: pass

a = f(B(), C())
g(a)
h(a) # E: Argument 1 to "h" has incompatible type "I"; expected "J"
b = f(C(), B())
g(b)
h(b) # E: Argument 1 to "h" has incompatible type "I"; expected "J"
c = f(A(), B())
g(a)
h(b) # E: Argument 1 to "h" has incompatible type "I"; expected "J"

[case testGenericFunctionInferenceWithMultipleInheritance3]
from typing import TypeVar

class I: pass
class J: pass
class K(J): pass

class A(K): pass
class B(A, I): pass
class C(I, J): pass

T = TypeVar('T')
def f(a: T, b: T) -> T: pass
def g(x: K) -> None: pass

a = f(B(), C())
g(a) # E: Argument 1 to "g" has incompatible type "J"; expected "K"
b = f(A(), C())
g(b) # E: Argument 1 to "g" has incompatible type "J"; expected "K"
c = f(A(), B())
g(c)

[case testPrecedenceOfFirstBaseAsInferenceResult]
from typing import TypeVar
from abc import abstractmethod, ABCMeta
class A: pass
class B(A, I, J): pass
class C(A, I, J): pass

def f(a: T, b: T) -> T: pass

T = TypeVar('T')
a: A
i: I
j: J

a = f(B(), C())

class I(metaclass=ABCMeta): pass
class J(metaclass=ABCMeta): pass


[builtins fixtures/tuple.pyi]


-- Generic function inference with function arguments
-- --------------------------------------------------


[case testNonOverloadedMapInference]
from typing import TypeVar, Callable, List
t = TypeVar('t')
s = TypeVar('s')
class A: pass
b = bool()
def f(x: bool) -> A: pass
def mymap(f: Callable[[t], s], a: List[t]) -> List[s]: pass

l = mymap(f, [b])
if int():
    l = [A()]
lb = [b]
if int():
    l = lb # E: Incompatible types in assignment (expression has type "List[bool]", variable has type "List[A]")
[builtins fixtures/for.pyi]

[case testGenericFunctionWithTypeTypeAsCallable]
from typing import Callable, Type, TypeVar
T = TypeVar('T')
def f(x: Callable[..., T]) -> T: return x()
class A: pass
x: Type[A]
y = f(x)
reveal_type(y)  # N: Revealed type is "__main__.A"

-- Generic function inference with unions
-- --------------------------------------


[case testUnionInference]
from typing import TypeVar, Union, List
T = TypeVar('T')
U = TypeVar('U')
def f(x: Union[T, int], y: T) -> T: pass
f(1, 'a')() # E: "str" not callable
f('a', 1)() # E: "object" not callable
f('a', 'a')() # E: "str" not callable
f(1, 1)() # E: "int" not callable

def g(x: Union[T, List[T]]) -> List[T]: pass
def h(x: List[str]) -> None: pass
g('a')() # E: "List[str]" not callable

g(['a'])

h(g(['a']))

def i(x: Union[List[T], List[U]], y: List[T], z: List[U]) -> None: pass
a = [1]
b = ['b']
i(a, a, b)
i(b, a, b)
i(a, b, b) # E: Argument 1 to "i" has incompatible type "List[int]"; expected "List[str]"
[builtins fixtures/list.pyi]

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

T = TypeVar('T')

class GenericClass(Generic[T]):
    def __init__(self, value: T) -> None:
        self.value = value

def method_with_union(arg: Union[GenericClass[T], T]) -> GenericClass[T]:
    if not isinstance(arg, GenericClass):
        arg = GenericClass(arg)
    return arg

result_1 = method_with_union(GenericClass("test"))
reveal_type(result_1) # N: Revealed type is "__main__.GenericClass[builtins.str]"

result_2 = method_with_union("test")
reveal_type(result_2) # N: Revealed type is "__main__.GenericClass[builtins.str]"

[builtins fixtures/isinstance.pyi]

[case testInferenceOfUnionOfSequenceOfAnyAndSequenceOfSequence]
from typing import Sequence, Iterable, TypeVar, Union

T = TypeVar("T")
S = TypeVar("S")

def sub_method(value: Union[S, Iterable[S]]) -> Iterable[S]:
    pass

def method(value: Union[Sequence[T], Sequence[Sequence[T]]]) -> None:
    reveal_type(sub_method(value)) # N: Revealed type is "typing.Iterable[typing.Sequence[T`-1]]"

[case testInferenceOfUnionOfUnionWithSequenceAndSequenceOfThatUnion]
from typing import Sequence, Iterable, TypeVar, Union

T = Union[str, Sequence[int]]
S = TypeVar("S", bound=T)

def sub_method(value: Union[S, Iterable[S]]) -> Iterable[S]:
    pass

def method(value: Union[T, Sequence[T]]) -> None:
    reveal_type(sub_method(value)) # N: Revealed type is "typing.Iterable[Union[builtins.str, typing.Sequence[builtins.int]]]"


[case testCallableListJoinInference]
from typing import Any, Callable

def fun() -> None:
    callbacks = [
        callback1,
        callback2,
    ]

    for c in callbacks:
        call(c, 1234) # this must not fail

def callback1(i: int) -> int:
    return i
def callback2(i: int) -> str:
    return 'hello'
def call(c: Callable[[int], Any], i: int) -> None:
    c(i)
[builtins fixtures/list.pyi]
[out]

[case testCallableMeetAndJoin]
from typing import Callable, Any, TypeVar

class A: ...
class B(A): ...

def f(c: Callable[[B], int]) -> None: ...

c: Callable[[A], int]
d: Callable[[B], int]

lst = [c, d]
reveal_type(lst) # N: Revealed type is "builtins.list[def (__main__.B) -> builtins.int]"

T = TypeVar('T')
def meet_test(x: Callable[[T], int], y: Callable[[T], int]) -> T: ...

CA = Callable[[A], A]
CB = Callable[[B], B]

ca: Callable[[CA], int]
cb: Callable[[CB], int]
reveal_type(meet_test(ca, cb)) # N: Revealed type is "def (__main__.A) -> __main__.B"
[builtins fixtures/list.pyi]
[out]

[case testUnionInferenceWithTypeVarValues]
from typing import TypeVar, Union
AnyStr = TypeVar('AnyStr', bytes, str)
def f(x: Union[AnyStr, int], *a: AnyStr) -> None: pass
f('foo')
f('foo', 'bar')
f('foo', b'bar') # E: Value of type variable "AnyStr" of "f" cannot be "Sequence[object]"
f(1)
f(1, 'foo')
f(1, 'foo', b'bar') # E: Value of type variable "AnyStr" of "f" cannot be "Sequence[object]"
[builtins fixtures/primitives.pyi]


[case testUnionTwoPassInference-skip]
from typing import TypeVar, Union, List
T = TypeVar('T')
U = TypeVar('U')
def j(x: Union[List[T], List[U]], y: List[T]) -> List[U]: pass

a = [1]
b = ['b']
# We could infer: Since List[str] <: List[T], we must have T = str.
# Then since List[int] <: Union[List[str], List[U]], and List[int] is
# not a subtype of List[str], we must have U = int.
# This is not currently implemented.
j(a, b)
[builtins fixtures/list.pyi]


[case testUnionContext]
from typing import TypeVar, Union, List
T = TypeVar('T')
def f() -> List[T]: pass
d1 = f() # type: Union[List[int], str]
d2 = f() # type: Union[int, str] # E: Incompatible types in assignment (expression has type "List[Never]", variable has type "Union[int, str]")
def g(x: T) -> List[T]: pass
d3 = g(1) # type: Union[List[int], List[str]]
[builtins fixtures/list.pyi]


[case testGenericFunctionSubtypingWithUnions]
from typing import TypeVar, Union, List
T = TypeVar('T')
S = TypeVar('S')
def k1(x: int, y: List[T]) -> List[Union[T, int]]: pass
def k2(x: S, y: List[T]) -> List[Union[T, int]]: pass
a = k2
if int():
    a = k2
if int():
    a = k1 # E: Incompatible types in assignment (expression has type "Callable[[int, List[T@k1]], List[Union[T@k1, int]]]", variable has type "Callable[[S, List[T@k2]], List[Union[T@k2, int]]]")
b = k1
if int():
    b = k1
if int():
    b = k2
[builtins fixtures/list.pyi]

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

_T = TypeVar('_T')

class T(Generic[_T]): pass
class U(Generic[_T]): pass
class V(T[_T], U[_T]): pass

def wait_for(fut: Union[T[_T], U[_T]]) -> _T: ...

reveal_type(wait_for(V[str]()))  # N: Revealed type is "builtins.str"

[case testAmbiguousUnionContextAndMultipleInheritance2]
from typing import TypeVar, Union, Generic

_T = TypeVar('_T')
_S = TypeVar('_S')

class T(Generic[_T, _S]): pass
class U(Generic[_T, _S]): pass
class V(T[_T, _S], U[_T, _S]): pass

def wait_for(fut: Union[T[_T, _S], U[_T, _S]]) -> T[_T, _S]: ...

reveal_type(wait_for(V[int, str]()))  \
    # N: Revealed type is "__main__.T[builtins.int, builtins.str]"


-- Literal expressions
-- -------------------


[case testDictLiteral]
from typing import Dict
class A: pass
class B: pass
def d_ab() -> Dict[A, B]: return {}
def d_aa() -> Dict[A, A]: return {}
a: A
b: B
d = {a:b}
if int():
    d = d_ab()
if int():
    d = d_aa() # E: Incompatible types in assignment (expression has type "Dict[A, A]", variable has type "Dict[A, B]")
[builtins fixtures/dict.pyi]

[case testSetLiteral]
from typing import Any, Set
a: int
x: Any
def s_i() -> Set[int]: return set()
def s_s() -> Set[str]: return set()
s = {a}
if int():
    s = {x}
if int():
    s = s_i()
if int():
    s = s_s() # E: Incompatible types in assignment (expression has type "Set[str]", variable has type "Set[int]")
[builtins fixtures/set.pyi]

[case testSetWithStarExpr]
s = {1, 2, *(3, 4)}
t = {1, 2, *s}
reveal_type(s)  # N: Revealed type is "builtins.set[builtins.int]"
reveal_type(t)  # N: Revealed type is "builtins.set[builtins.int]"
[builtins fixtures/set.pyi]

[case testListLiteralWithFunctionsErasesNames]
def f1(x: int) -> int: ...
def g1(y: int) -> int: ...
def h1(x: int) -> int: ...

list_1 = [f1, g1]
list_2 = [f1, h1]
reveal_type(list_1)  # N: Revealed type is "builtins.list[def (builtins.int) -> builtins.int]"
reveal_type(list_2)  # N: Revealed type is "builtins.list[def (x: builtins.int) -> builtins.int]"

def f2(x: int, z: str) -> int: ...
def g2(y: int, z: str) -> int: ...
def h2(x: int, z: str) -> int: ...

list_3 = [f2, g2]
list_4 = [f2, h2]
reveal_type(list_3)  # N: Revealed type is "builtins.list[def (builtins.int, z: builtins.str) -> builtins.int]"
reveal_type(list_4)  # N: Revealed type is "builtins.list[def (x: builtins.int, z: builtins.str) -> builtins.int]"
[builtins fixtures/list.pyi]

[case testListLiteralWithSimilarFunctionsErasesName]
from typing import Union

class A: ...
class B(A): ...
class C: ...
class D: ...

def f(x: Union[A, C], y: B) -> A: ...
def g(z: Union[B, D], y: A) -> B: ...
def h(x: Union[B, D], y: A) -> B: ...

list_1 = [f, g]
list_2 = [f, h]
reveal_type(list_1)  # N: Revealed type is "builtins.list[def (__main__.B, y: __main__.B) -> __main__.A]"
reveal_type(list_2)  # N: Revealed type is "builtins.list[def (x: __main__.B, y: __main__.B) -> __main__.A]"
[builtins fixtures/list.pyi]

[case testListLiteralWithNameOnlyArgsDoesNotEraseNames]
def f(*, x: int) -> int: ...
def g(*, y: int) -> int: ...
def h(*, x: int) -> int: ...

list_1 = [f, g]  # E: List item 0 has incompatible type "Callable[[NamedArg(int, 'x')], int]"; expected "Callable[[NamedArg(int, 'y')], int]"
list_2 = [f, h]
[builtins fixtures/list.pyi]


-- For statements
-- --------------


[case testInferenceOfFor1]
a: A
b: B

class A: pass
class B: pass

for x in [A()]:
    b = x # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    a = x

for y in []: # E: Need type annotation for "y"
    a = y
    reveal_type(y)  # N: Revealed type is "Any"
[builtins fixtures/for.pyi]

[case testInferenceOfFor2]
class A: pass
class B: pass
class C: pass

a: A
b: B
c: C
for x, (y, z) in [(A(), (B(), C()))]:
    b = x # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    c = y # E: Incompatible types in assignment (expression has type "B", variable has type "C")
    a = z # E: Incompatible types in assignment (expression has type "C", variable has type "A")
    a = x
    b = y
    c = z
for xx, yy, zz in [(A(), B())]: # E: Need more than 2 values to unpack (3 expected)
    pass
for xx, (yy, zz) in [(A(), B())]: # E: "B" object is not iterable
    pass
for xxx, yyy in [(None, None)]:
    pass
[builtins fixtures/for.pyi]

[case testInferenceOfFor3]
class A: pass
class B: pass

a: A
b: B

for x, y in [[A()]]:
    b = x # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    b = y # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    a = x
    a = y

for e, f in [[]]:  # E: Need type annotation for "e" \
                   # E: Need type annotation for "f"
    reveal_type(e)  # N: Revealed type is "Any"
    reveal_type(f)  # N: Revealed type is "Any"

[builtins fixtures/for.pyi]

[case testForStatementInferenceWithVoid]
def f() -> None: pass

for x in f(): # E: "f" does not return a value (it only ever returns None)
    pass
[builtins fixtures/for.pyi]

[case testReusingInferredForIndex]
import typing

class A: pass
class B: pass

for a in [A()]: pass
a = A()
if int():
    a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
    for a in []: pass
    a = A()
    a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
[builtins fixtures/for.pyi]

[case testReusingInferredForIndex2]
# flags: --allow-redefinition

def f() -> None:
    for a in [A()]: pass
    a = A()
    a
    if int():
        a = B() \
            # E: Incompatible types in assignment (expression has type "B", variable has type "A")
    for a in []: pass # E: Need type annotation for "a"
    a = A()
    if int():
        a = B() \
            # E: Incompatible types in assignment (expression has type "B", variable has type "A")
class A: pass
class B: pass
[builtins fixtures/for.pyi]
[out]

[case testReusingInferredForIndex3]
# flags: --disallow-redefinition
def f() -> None:
    for a in [A()]: pass
    a = A()
    a
    if int():
        a = B() \
            # E: Incompatible types in assignment (expression has type "B", variable has type "A")
    for a in []: pass
    a = A()
    if int():
        a = B() \
            # E: Incompatible types in assignment (expression has type "B", variable has type "A")
class A: pass
class B: pass
[builtins fixtures/for.pyi]
[out]

[case testForStatementIndexNarrowing]
from typing_extensions import TypedDict

class X(TypedDict):
    hourly: int
    daily: int

x: X
for a in ("hourly", "daily"):
    reveal_type(a)  # N: Revealed type is "Union[Literal['hourly']?, Literal['daily']?]"
    reveal_type(x[a])  # N: Revealed type is "builtins.int"
    reveal_type(a.upper())  # N: Revealed type is "builtins.str"
    c = a
    reveal_type(c)  # N: Revealed type is "builtins.str"
    a = "monthly"
    reveal_type(a)  # N: Revealed type is "builtins.str"
    a = "yearly"
    reveal_type(a)  # N: Revealed type is "builtins.str"
    a = 1  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
    reveal_type(a)  # N: Revealed type is "builtins.str"
    d = a
    reveal_type(d)  # N: Revealed type is "builtins.str"

b: str
for b in ("hourly", "daily"):
    reveal_type(b)  # N: Revealed type is "builtins.str"
    reveal_type(b.upper())  # N: Revealed type is "builtins.str"
[builtins fixtures/for.pyi]


-- Regression tests
-- ----------------


[case testMultipleAssignmentWithPartialDefinition]
a: A
if int():
    x, a = a, a
    if int():
        x = a
    a = x
    if int():
        x = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
    a = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
class A: pass

[case testMultipleAssignmentWithPartialDefinition2]
a: A
if int():
    a, x = [a, a]
    if int():
        x = a
    a = x
    if int():
        x = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
    a = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
class A: pass
[builtins fixtures/for.pyi]

[case testMultipleAssignmentWithPartialDefinition3]
from typing import Any, cast
a: A
if int():
    x, a = cast(Any, a)
    if int():
        x = a
    a = x
    if int():
        x = object()
    a = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
class A: pass

[case testInferGlobalDefinedInBlock]
class A: pass
class B: pass

if int():
    a = A()
    if int():
        a = A()
    if int():
        a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")

[case testAssigningAnyStrToNone]
from typing import Tuple, TypeVar
AnyStr = TypeVar('AnyStr', str, bytes)

def f(x: AnyStr) -> Tuple[AnyStr]: pass
x = None
(x,) = f('')
reveal_type(x)  # N: Revealed type is "builtins.str"
[builtins fixtures/tuple.pyi]


-- Inferring attribute types
-- -------------------------


[case testInferAttributeType]
import typing
class A:
    a = B()
class B: pass

A().a = B()
A().a = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")

[case testInferAttributeTypeAndAssignInInit]
import typing
class A:
    a = B()
    def __init__(self) -> None:
        self.a = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")
        self.a = B()
class B: pass
[out]

[case testInferAttributeInInit]
import typing
class B: pass
class A:
    def __init__(self) -> None:
        self.a = A()
        self.b = B()
a = A()
a.a = A()
a.b = B()
a.a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
a.b = A() # E: Incompatible types in assignment (expression has type "A", variable has type "B")

[case testInferAttributeInInitUsingChainedAssignment]
import typing
class B: pass
class A:
    def __init__(self) -> None:
        self.a = self.b = A()
a = A()
a.a = A()
a.b = A()
a.a = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
a.b = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")


-- Lambdas
-- -------


[case testInferLambdaType]
from typing import List, Callable
li = [1]
l = lambda: li
f1 = l # type: Callable[[], List[int]]
f2 = l # type: Callable[[], List[str]] # E: Incompatible types in assignment (expression has type "Callable[[], List[int]]", variable has type "Callable[[], List[str]]")
[builtins fixtures/list.pyi]

[case testInferLambdaType2]
from typing import List, Callable
l = lambda: [B()]
f1 = l # type: Callable[[], List[B]]
f2 = l # type: Callable[[], List[A]] # E: Incompatible types in assignment (expression has type "Callable[[], List[B]]", variable has type "Callable[[], List[A]]")

class A: pass
class B: pass
[builtins fixtures/list.pyi]

[case testUninferableLambda]
# flags: --new-type-inference
from typing import TypeVar, Callable
X = TypeVar('X')
def f(x: Callable[[X], X]) -> X: pass
y = f(lambda x: x)  # E: Need type annotation for "y"

[case testUninferableLambdaWithTypeError]
# flags: --new-type-inference
from typing import TypeVar, Callable
X = TypeVar('X')
def f(x: Callable[[X], X], y: str) -> X: pass
y = f(lambda x: x, 1) # E: Need type annotation for "y" \
                      # E: Argument 2 to "f" has incompatible type "int"; expected "str"

[case testInferLambdaNone]
# flags: --no-strict-optional
from typing import Callable
def f(x: Callable[[], None]) -> None: pass
def g(x: Callable[[], int]) -> None: pass
a = lambda: None
f(a)
g(a)
b = lambda: None  # type: Callable[[], None]
f(b)
g(b)

[case testLambdaDefaultContext]
from typing import Callable
def f(a: Callable[..., None] = lambda *a, **k: None):
    pass

def g(a: Callable[..., None] = lambda *a, **k: 1):  # E: Incompatible default for argument "a" (default has type "Callable[[VarArg(Any), KwArg(Any)], int]", argument has type "Callable[..., None]")
    pass
[builtins fixtures/dict.pyi]

[case testLambdaVarargContext]
# Should not crash
from typing import Callable
def f(a: Callable[[int, int, int], int] = lambda *a, **k: 1):
    pass
[builtins fixtures/dict.pyi]

[case testLambdaDeferredSpecialCase]
from typing import Callable

class A:
    def f(self) -> None:
        h(lambda: self.x)

    def g(self) -> None:
        self.x = 1

def h(x: Callable[[], int]) -> None:
    pass

[case testLambdaJoinWithDynamicConstructor]
from typing import Any, Union

class Wrapper:
    def __init__(self, x: Any) -> None: ...

def f(cond: bool) -> Any:
    f = Wrapper if cond else lambda x: x
    reveal_type(f)  # N: Revealed type is "Union[def (x: Any) -> __main__.Wrapper, def (x: Any) -> Any]"
    return f(3)

def g(cond: bool) -> Any:
    f = lambda x: x if cond else Wrapper
    reveal_type(f)  # N: Revealed type is "def (x: Any) -> Union[Any, def (x: Any) -> __main__.Wrapper]"
    return f(3)

def h(cond: bool) -> Any:
    f = (lambda x: x) if cond else Wrapper
    reveal_type(f)  # N: Revealed type is "Union[def (x: Any) -> Any, def (x: Any) -> __main__.Wrapper]"
    return f(3)

-- Boolean operators
-- -----------------

[case testOrOperationWithGenericOperands]
from typing import List
a: List[A]
o: List[object]
a2 = a or []
if int():
    a = a2
    a2 = o # E: Incompatible types in assignment (expression has type "List[object]", variable has type "List[A]")
class A: pass
[builtins fixtures/list.pyi]


-- Accessing variable before its type has been inferred
-- ----------------------------------------------------


[case testAccessGlobalVarBeforeItsTypeIsAvailable]
import typing
x.y  # E: Cannot determine type of "x"  # E: Name "x" is used before definition
x = object()
x.y  # E: "object" has no attribute "y"

[case testAccessDataAttributeBeforeItsTypeIsAvailable]

a: A
a.x.y  # E: Cannot determine type of "x"
class A:
   def __init__(self) -> None:
       self.x = object()
a.x.y  # E: "object" has no attribute "y"


-- Ducktype declarations
-- ---------------------


[case testListWithDucktypeCompatibility]
from typing import List, _promote
class A: pass
@_promote(A)
class B: pass
a: List[A]
x1 = [A(), B()]
x2 = [B(), A()]
x3 = [B(), B()]
if int():
    a = x1
if int():
    a = x2
if int():
    a = x3 \
     # E: Incompatible types in assignment (expression has type "List[B]", variable has type "List[A]") \
     # N: "List" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance \
     # N: Consider using "Sequence" instead, which is covariant
[builtins fixtures/list.pyi]
[typing fixtures/typing-medium.pyi]

[case testListWithDucktypeCompatibilityAndTransitivity]
from typing import List, _promote
class A: pass
@_promote(A)
class B: pass
@_promote(B)
class C: pass
a: List[A]
x1 = [A(), C()]
x2 = [C(), A()]
x3 = [B(), C()]
if int():
    a = x1
if int():
    a = x2
if int():
    a = x3 \
     # E: Incompatible types in assignment (expression has type "List[B]", variable has type "List[A]") \
     # N: "List" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance \
     # N: Consider using "Sequence" instead, which is covariant
[builtins fixtures/list.pyi]
[typing fixtures/typing-medium.pyi]


-- Inferring type of variable when initialized to an empty collection
-- ------------------------------------------------------------------


[case testInferListInitializedToEmpty]
a = []
a.append(1)
a.append('')  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyUsingUpdate]
a = []
a.extend([''])
a.append(0)  # E: Argument 1 to "append" of "list" has incompatible type "int"; expected "str"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndNotAnnotated]
a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndReadBeforeAppend]
a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
if a: pass
a.xyz  # E: "List[Any]" has no attribute "xyz"
a.append('')
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndIncompleteTypeInAppend]
a = [] # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
a.append([])
a()  # E: "List[Any]" not callable
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndMultipleAssignment]
a, b = [], []
a.append(1)
b.append('')
a() # E: "List[int]" not callable
b() # E: "List[str]" not callable
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyInFunction]
def f() -> None:
   a = []
   a.append(1)
   a.append('')  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndNotAnnotatedInFunction]
def f() -> None:
    a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")

def g() -> None: pass

a = []
a.append(1)
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndReadBeforeAppendInFunction]
def f() -> None:
    a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
    if a: pass
    a.xyz  # E: "List[Any]" has no attribute "xyz"
    a.append('')
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyInClassBody]
class A:
   a = []
   a.append(1)
   a.append('')  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndNotAnnotatedInClassBody]
class A:
    a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")

class B:
    a = []
    a.append(1)
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyInMethod]
class A:
    def f(self) -> None:
        a = []
        a.append(1)
        a.append('')  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndNotAnnotatedInMethod]
class A:
    def f(self) -> None:
        a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyInMethodViaAttribute]
class A:
    def f(self) -> None:
        # Attributes aren't supported right now.
        self.a = []
        self.a.append(1)
        self.a.append('')  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyInClassBodyAndOverriden]
from typing import List

class A:
    def __init__(self) -> None:
        self.x = [] # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")

class B(A):
    @property
    def x(self) -> List[int]:  # E: Cannot override writeable attribute with read-only property
        return [123]
[builtins fixtures/list.pyi]

[case testInferSetInitializedToEmpty]
a = set()
a.add(1)
a.add('')  # E: Argument 1 to "add" of "set" has incompatible type "str"; expected "int"
[builtins fixtures/set.pyi]

[case testInferSetInitializedToEmptyUsingDiscard]
a = set()
a.discard('')
a.add(0)  # E: Argument 1 to "add" of "set" has incompatible type "int"; expected "str"
[builtins fixtures/set.pyi]

[case testInferSetInitializedToEmptyUsingUpdate]
a = set()
a.update({0})
a.add('')  # E: Argument 1 to "add" of "set" has incompatible type "str"; expected "int"
[builtins fixtures/set.pyi]

[case testInferDictInitializedToEmpty]
a = {}
a[1] = ''
a() # E: "Dict[int, str]" not callable
[builtins fixtures/dict.pyi]

[case testInferDictInitializedToEmptyUsingUpdate]
a = {}
a.update({'': 42})
a() # E: "Dict[str, int]" not callable
[builtins fixtures/dict.pyi]

[case testInferDictInitializedToEmptyUsingUpdateError]
a = {}  # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")
a.update([1, 2])  # E: Argument 1 to "update" of "dict" has incompatible type "List[int]"; expected "SupportsKeysAndGetItem[Any, Any]" \
                  # N: "list" is missing following "SupportsKeysAndGetItem" protocol member: \
                  # N:     keys
a()  # E: "Dict[Any, Any]" not callable
[builtins fixtures/dict.pyi]

[case testInferDictInitializedToEmptyAndIncompleteTypeInUpdate]
a = {} # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")
a[1] = {}
b = {} # E: Need type annotation for "b" (hint: "b: Dict[<type>, <type>] = ...")
b[{}] = 1
[builtins fixtures/dict.pyi]

[case testInferDictInitializedToEmptyAndUpdatedFromMethod]
map = {}
def add() -> None:
    map[1] = 2
[builtins fixtures/dict.pyi]

[case testInferDictInitializedToEmptyAndUpdatedFromMethodUnannotated]
map = {}
def add():
    map[1] = 2
[builtins fixtures/dict.pyi]

[case testSpecialCaseEmptyListInitialization]
def f(blocks: Any): # E: Name "Any" is not defined \
                    # N: Did you forget to import it from "typing"? (Suggestion: "from typing import Any")
    to_process = []
    to_process = list(blocks)
[builtins fixtures/list.pyi]

[case testSpecialCaseEmptyListInitialization2]
def f(blocks: object):
    to_process = []
    to_process = list(blocks) # E: No overload variant of "list" matches argument type "object" \
                              # N: Possible overload variants: \
                              # N:     def [T] __init__(self) -> List[T] \
                              # N:     def [T] __init__(self, x: Iterable[T]) -> List[T]
[builtins fixtures/list.pyi]

[case testInferListInitializedToEmptyAndAssigned]
a = []
if bool():
    a = [1]
reveal_type(a) # N: Revealed type is "builtins.list[builtins.int]"

def f():
    return [1]
b = []
if bool():
    b = f()
reveal_type(b) # N: Revealed type is "builtins.list[Any]"

d = {}
if bool():
    d = {1: 'x'}
reveal_type(d) # N: Revealed type is "builtins.dict[builtins.int, builtins.str]"

dd = {} # E: Need type annotation for "dd" (hint: "dd: Dict[<type>, <type>] = ...")
if bool():
    dd = [1] # E: Incompatible types in assignment (expression has type "List[int]", variable has type "Dict[Any, Any]")
reveal_type(dd) # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testInferOrderedDictInitializedToEmpty]
from collections import OrderedDict

o = OrderedDict()
o[1] = 'x'
reveal_type(o) # N: Revealed type is "collections.OrderedDict[builtins.int, builtins.str]"

d = {1: 'x'}
oo = OrderedDict()
oo.update(d)
reveal_type(oo) # N: Revealed type is "collections.OrderedDict[builtins.int, builtins.str]"
[builtins fixtures/dict.pyi]

[case testEmptyCollectionAssignedToVariableTwiceIncremental]
x = [] # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
y = x
x = []
reveal_type(x) # N: Revealed type is "builtins.list[Any]"
d = {} # E: Need type annotation for "d" (hint: "d: Dict[<type>, <type>] = ...")
z = d
d = {}
reveal_type(d) # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]
[out2]
main:1: error: Need type annotation for "x" (hint: "x: List[<type>] = ...")
main:4: note: Revealed type is "builtins.list[Any]"
main:5: error: Need type annotation for "d" (hint: "d: Dict[<type>, <type>] = ...")
main:8: note: Revealed type is "builtins.dict[Any, Any]"

[case testEmptyCollectionAssignedToVariableTwiceNoReadIncremental]
x = [] # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
x = []
[builtins fixtures/list.pyi]
[out2]
main:1: error: Need type annotation for "x" (hint: "x: List[<type>] = ...")

[case testInferAttributeInitializedToEmptyAndAssigned]
class C:
    def __init__(self) -> None:
        self.a = []
        if bool():
            self.a = [1]
reveal_type(C().a)  # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAppended]
class C:
    def __init__(self) -> None:
        self.a = []
        if bool():
            self.a.append(1)
reveal_type(C().a)  # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAssignedItem]
class C:
    def __init__(self) -> None:
        self.a = {}
        if bool():
            self.a[0] = 'yes'
reveal_type(C().a)  # N: Revealed type is "builtins.dict[builtins.int, builtins.str]"
[builtins fixtures/dict.pyi]

[case testInferAttributeInitializedToNoneAndAssigned]
class C:
    def __init__(self) -> None:
        self.a = None
        if bool():
            self.a = 1
reveal_type(C().a)  # N: Revealed type is "Union[builtins.int, None]"

[case testInferAttributeInitializedToEmptyNonSelf]
class C:
    def __init__(self) -> None:
        self.a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
        if bool():
            a = self
            a.a = [1]
            a.a.append(1)
reveal_type(C().a)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAssignedOtherMethod]
class C:
    def __init__(self) -> None:
        self.a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
    def meth(self) -> None:
        self.a = [1]
reveal_type(C().a)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAppendedOtherMethod]
class C:
    def __init__(self) -> None:
        self.a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
    def meth(self) -> None:
        self.a.append(1)
reveal_type(C().a)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAssignedItemOtherMethod]
class C:
    def __init__(self) -> None:
        self.a = {}  # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")
    def meth(self) -> None:
        self.a[0] = 'yes'
reveal_type(C().a)  # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testInferAttributeInitializedToNoneAndAssignedOtherMethod]
class C:
    def __init__(self) -> None:
        self.a = None
    def meth(self) -> None:
        self.a = 1  # E: Incompatible types in assignment (expression has type "int", variable has type "None")
reveal_type(C().a)  # N: Revealed type is "None"

[case testInferAttributeInitializedToEmptyAndAssignedClassBody]
class C:
    a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
    def __init__(self) -> None:
        self.a = [1]
reveal_type(C().a)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAppendedClassBody]
class C:
    a = []  # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")
    def __init__(self) -> None:
        self.a.append(1)
reveal_type(C().a)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferAttributeInitializedToEmptyAndAssignedItemClassBody]
class C:
    a = {}  # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")
    def __init__(self) -> None:
        self.a[0] = 'yes'
reveal_type(C().a)  # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testInferAttributeInitializedToNoneAndAssignedClassBody]
class C:
    a = None
    def __init__(self) -> None:
        self.a = 1
reveal_type(C().a)  # N: Revealed type is "Union[builtins.int, None]"

[case testInferListTypeFromEmptyListAndAny]
def f():
    return []

def g() -> None:
    x = []
    if bool():
        x = f()
    reveal_type(x)  # N: Revealed type is "builtins.list[Any]"

    y = []
    y.extend(f())
    reveal_type(y)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferFromEmptyDictWhenUsingIn]
d = {}
if 'x' in d:
    d['x'] = 1
reveal_type(d)  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"

dd = {}
if 'x' not in dd:
    dd['x'] = 1
reveal_type(dd)  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
[builtins fixtures/dict.pyi]

[case testInferFromEmptyDictWhenUsingInSpecialCase]
# flags: --no-strict-optional
d = None
if 'x' in d:  # E: "None" has no attribute "__iter__" (not iterable)
    pass
reveal_type(d)  # N: Revealed type is "None"
[builtins fixtures/dict.pyi]

[case testInferFromEmptyListWhenUsingInWithStrictEquality]
# flags: --strict-equality
def f() -> None:
    a = []
    if 1 in a:  # TODO: This should be an error
        a.append('x')
[builtins fixtures/list.pyi]
[typing fixtures/typing-full.pyi]

[case testInferListTypeFromInplaceAdd]
a = []
a += [1]
reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testInferSetTypeFromInplaceOr]
# flags: --no-strict-optional
a = set()
a |= {'x'}
reveal_type(a)  # N: Revealed type is "builtins.set[builtins.str]"
[builtins fixtures/set.pyi]


-- Inferring types of variables first initialized to None (partial types)
-- ----------------------------------------------------------------------


[case testLocalVariablePartiallyInitializedToNone]
def f() -> None:
    if object():
        x = None
    else:
        x = 1
    x() # E: "int" not callable \
        # E: "None" not callable
[out]

[case testLocalVariablePartiallyTwiceInitializedToNone]
def f() -> None:
    if object():
        x = None
    elif object():
        x = None
    else:
        x = 1
    x() # E: "int" not callable \
        # E: "None" not callable
[out]

[case testLvarInitializedToNoneWithoutType]
import typing
def f() -> None:
    a = None
    a.x() # E: "None" has no attribute "x"
[out]

[case testGvarPartiallyInitializedToNone]
x = None
if object():
    x = 1
x() # E: "int" not callable \
    # E: "None" not callable

[case testPartiallyInitializedToNoneAndThenToPartialList]
x = None
if object():
    # Promote from partial None to partial list.
    x = []
    x.append(1)
x.append('') # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testPartiallyInitializedToNoneAndThenReadPartialList]
x = None
if object():
    # Promote from partial None to partial list.
    x = []  # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
    x
[builtins fixtures/list.pyi]

[case testPartiallyInitializedToNoneAndPartialListAndLeftPartial]
def f() -> None:
    x = None
    if object():
        # Promote from partial None to partial list.
        x = []  # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
[builtins fixtures/list.pyi]
[out]

[case testPartiallyInitializedToNoneAndThenToIncompleteType-skip]
# TODO(ddfisher): fix partial type bug and re-enable
from typing import TypeVar,  Dict
T = TypeVar('T')
def f(*x: T) -> Dict[int, T]: pass
x = None  # E: Need type annotation for "x"
if object():
    x = f()
[builtins fixtures/dict.pyi]

[case testPartiallyInitializedVariableDoesNotEscapeScope1]
def f() -> None:
    x = None
    reveal_type(x)  # N: Revealed type is "None"
x = 1
[out]

[case testPartiallyInitializedVariableDoesNotEscapeScope2]
x = None
def f() -> None:
    x = None
    x = 1
x()  # E: "None" not callable

[case testAttributePartiallyInitializedToNone]
class A:
    def f(self) -> None:
        self.x = None
        self.x = 1
        self.x() # E: "int" not callable
[out]

[case testAttributePartiallyInitializedToNoneWithMissingAnnotation]
class A:
    def f(self) -> None:
        self.x = None

    def g(self) -> None:
        self.x = 1
        self.x()
[out]
main:6: error: Incompatible types in assignment (expression has type "int", variable has type "None")
main:7: error: "None" not callable

[case testGlobalInitializedToNoneSetFromFunction]
a = None
def f():
    global a
    a = 42
[out]

[case testGlobalInitializedToNoneSetFromMethod]
a = None
class C:
    def m(self):
        global a
        a = 42
[out]

-- More partial type errors
-- ------------------------

[case testPartialTypeErrorSpecialCase1]
# This used to crash.
class A:
    x = None
    def f(self) -> None:
        for a in self.x:
            pass
[builtins fixtures/for.pyi]
[out]
main:5: error: "None" has no attribute "__iter__" (not iterable)

[case testPartialTypeErrorSpecialCase2]
# This used to crash.
class A:
    x = []
    def f(self) -> None:
        for a in self.x:
            pass
[builtins fixtures/for.pyi]
[out]
main:3: error: Need type annotation for "x" (hint: "x: List[<type>] = ...")

[case testPartialTypeErrorSpecialCase3]
class A:
    x = None
    def f(self) -> None:
        for a in A.x:
            pass
[builtins fixtures/for.pyi]
[out]
main:4: error: "None" has no attribute "__iter__" (not iterable)

[case testPartialTypeErrorSpecialCase4]
# This used to crash.
arr = []
arr.append(arr.append(1))
[builtins fixtures/list.pyi]
[out]
main:3: error: "append" of "list" does not return a value (it only ever returns None)

-- Multipass
-- ---------


[case testMultipassAndAccessVariableBeforeDefinition]
def f() -> None:
    y = x
    y() # E: "int" not callable
x = 1
[out]

[case testMultipassAndAccessInstanceVariableBeforeDefinition]
class A:
    def f(self) -> None:
        y = self.x
        y() # E: "int" not callable

    def g(self) -> None:
        self.x = 1
[out]

[case testMultipassAndTopLevelVariable]
y = x # E: Cannot determine type of "x"  # E: Name "x" is used before definition
y()
x = 1+int()
[out]

[case testMultipassAndDecoratedMethod]
from typing import Callable, TypeVar

T = TypeVar('T')

class A:
    def f(self) -> None:
        self.g() # E: Too few arguments for "g" of "A"
        self.g(1)
    @dec
    def g(self, x: str) -> None: pass

def dec(f: Callable[[A, str], T]) -> Callable[[A, int], T]: pass
[out]

[case testMultipassAndDefineAttributeBasedOnNotReadyAttribute]
class A:
    def f(self) -> None:
        self.y = self.x

    def g(self) -> None:
        self.x = 1

    def h(self) -> None:
        self.y() # E: "int" not callable
[out]

[case testMultipassAndDefineAttributeBasedOnNotReadyAttribute2]
class A:
    def f(self) -> None:
        self.y = self.x
        self.z = self.y
        self.z() # E
        self.y() # E

    def g(self) -> None:
        self.x = 1

    def h(self) -> None:
        self.y() # E
[out]
main:5: error: "int" not callable
main:6: error: "int" not callable
main:12: error: "int" not callable

[case testMultipassAndPartialTypes]
def f() -> None:
    x = []
    y
    x.append(1)
    x.append('') # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
    x.append(y) # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
y = ''
[builtins fixtures/list.pyi]
[out]

[case testMultipassAndPartialTypes2]
s = ''
n = 0
def f() -> None:
    global s, n
    x = []
    x.append(y)
    s = x[0]
    n = x[0] # E: Incompatible types in assignment (expression has type "str", variable has type "int")
    x.append(1) # E: Argument 1 to "append" of "list" has incompatible type "int"; expected "str"
y = ''
[builtins fixtures/list.pyi]
[out]

[case testMultipassAndPartialTypes3]
from typing import Dict
def g(d: Dict[str, int]) -> None: pass
def f() -> None:
    x = {}
    x[1] = y
    g(x) # E: Argument 1 to "g" has incompatible type "Dict[int, str]"; expected "Dict[str, int]"
    x[1] = 1 # E: Incompatible types in assignment (expression has type "int", target has type "str")
    x[1] = ''
y = ''
[builtins fixtures/dict.pyi]
[out]

[case testMultipassAndPartialTypes4]
from typing import Dict
def g(d: Dict[str, int]) -> None: pass
def f() -> None:
    x = {}
    y
    x[1] = 1
    g(x) # E: Argument 1 to "g" has incompatible type "Dict[int, int]"; expected "Dict[str, int]"
y = ''
[builtins fixtures/dict.pyi]
[out]

[case testMultipassAndCircularDependency]
class A:
    def f(self) -> None:
        self.x = self.y # E: Cannot determine type of "y"

    def g(self) -> None:
        self.y = self.x
[out]

[case testMultipassAndPartialTypesSpecialCase1]
def f() -> None:
    y = o
    x = []
    x.append(y)
    x() # E: "List[int]" not callable
o = 1
[builtins fixtures/list.pyi]
[out]

[case testMultipassAndPartialTypesSpecialCase2]
def f() -> None:
    y = o
    x = {}
    x[''] = y
    x() # E: "Dict[str, int]" not callable
o = 1
[builtins fixtures/dict.pyi]
[out]

[case testMultipassAndPartialTypesSpecialCase3]
def f() -> None:
    x = {} # E: Need type annotation for "x" (hint: "x: Dict[<type>, <type>] = ...")
    y = o
    z = {} # E: Need type annotation for "z" (hint: "z: Dict[<type>, <type>] = ...")
o = 1
[builtins fixtures/dict.pyi]
[out]

[case testMultipassAndPartialTypesSpecialCase4]
def f() -> None:
    y = o
    x = None
    x = y
    x() # E: "int" not callable
o = 1
[out]

[case testMultipassAndPartialTypesSpecialCase5]
def f() -> None:
    x = None
    y = o
    x = y
    x() # E: "int" not callable
o = 1
[out]

[case testMultipassAndClassAttribute]
class S:
    def foo(self) -> int:
        return R.X

class R:
    X = 2

[case testMultipassAndMultipleFiles]
import m
def f() -> None:
    x()
x = 0
[file m.py]
def g() -> None:
    y()
y = 0
[out]
tmp/m.py:2: error: "int" not callable
main:3: error: "int" not callable

[case testForwardReferenceToDecoratedClassMethod]
from typing import TypeVar, Callable

T = TypeVar('T')
def dec() -> Callable[[T], T]: pass

A.g  # E: Cannot determine type of "g"  # E: Name "A" is used before definition

class A:
    @classmethod
    def f(cls) -> None:
        reveal_type(cls.g)  # N: Revealed type is "def (x: builtins.str)"

    @classmethod
    @dec()
    def g(cls, x: str) -> None:
        pass

    @classmethod
    def h(cls) -> None:
        reveal_type(cls.g)  # N: Revealed type is "def (x: builtins.str)"

reveal_type(A.g)  # N: Revealed type is "def (x: builtins.str)"
[builtins fixtures/classmethod.pyi]


-- Tests for special cases of unification
-- --------------------------------------


[case testUnificationRedundantUnion]
from typing import Union
a: Union[int, str]
b: Union[str, tuple]
def f(): pass
def g(x: Union[int, str]): pass
c = a if f() else b
g(c) # E: Argument 1 to "g" has incompatible type "Union[int, str, Tuple[Any, ...]]"; expected "Union[int, str]"
[builtins fixtures/tuple.pyi]

[case testUnificationMultipleInheritance]
class A: pass
class B:
    def foo(self): pass
class C(A, B): pass
def f(): pass
a1 = B() if f() else C()
a1.foo()
a2 = C() if f() else B()
a2.foo()

[case testUnificationMultipleInheritanceAmbiguous]
# Show that join_instances_via_supertype() breaks ties using the first base class.
class A1: pass
class B1:
    def foo1(self): pass
class C1(A1, B1): pass

class A2: pass
class B2:
    def foo2(self): pass
class C2(A2, B2): pass

class D1(C1, C2): pass
class D2(C2, C1): pass

def f(): pass

a1 = D1() if f() else D2()
a1.foo1()
a2 = D2() if f() else D1()
a2.foo2()

[case testUnificationEmptyListLeft]
def f(): pass
a = [] if f() else [0]
a() # E: "List[int]" not callable
[builtins fixtures/list.pyi]

[case testUnificationEmptyListRight]
def f(): pass
a = [0] if f() else []
a() # E: "List[int]" not callable
[builtins fixtures/list.pyi]

[case testUnificationEmptyListLeftInContext]
from typing import List
def f(): pass
a = [] if f() else [0] # type: List[int]
a() # E: "List[int]" not callable
[builtins fixtures/list.pyi]

[case testUnificationEmptyListRightInContext]
# TODO Find an example that really needs the context
from typing import List
def f(): pass
a = [0] if f() else [] # type: List[int]
a() # E: "List[int]" not callable
[builtins fixtures/list.pyi]

[case testUnificationEmptySetLeft]
def f(): pass
a = set() if f() else {0}
a() # E: "Set[int]" not callable
[builtins fixtures/set.pyi]

[case testUnificationEmptyDictLeft]
def f(): pass
a = {} if f() else {0: 0}
a() # E: "Dict[int, int]" not callable
[builtins fixtures/dict.pyi]

[case testUnificationEmptyDictRight]
def f(): pass
a = {0: 0} if f() else {}
a() # E: "Dict[int, int]" not callable
[builtins fixtures/dict.pyi]

[case testUnificationDictWithEmptyListLeft]
def f(): pass
a = {0: []} if f() else {0: [0]}
a() # E: "Dict[int, List[int]]" not callable
[builtins fixtures/dict.pyi]

[case testUnificationDictWithEmptyListRight]
def f(): pass
a = {0: [0]} if f() else {0: []}
a() # E: "Dict[int, List[int]]" not callable
[builtins fixtures/dict.pyi]

[case testMisguidedSetItem]
from typing import Generic, Sequence, TypeVar
T = TypeVar('T')
class C(Sequence[T], Generic[T]): pass
C[0] = 0
[out]
main:4: error: Unsupported target for indexed assignment ("Type[C[Any]]")
main:4: error: Invalid type: try using Literal[0] instead?

[case testNoCrashOnPartialMember]
class C:
    x = None
    def __init__(self) -> None:
        self.x = []  # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
[builtins fixtures/list.pyi]
[out]

[case testNoCrashOnPartialVariable]
from typing import Tuple, TypeVar
T = TypeVar('T', bound=str)

def f(x: T) -> Tuple[T]:
    ...
x = None
(x,) = f('')
reveal_type(x) # N: Revealed type is "builtins.str"
[builtins fixtures/tuple.pyi]
[out]

[case testNoCrashOnPartialVariable2]
from typing import Tuple, TypeVar
T = TypeVar('T', bound=str)

def f() -> Tuple[T]:
    ...
x = None
if int():
    (x,) = f()
[builtins fixtures/tuple.pyi]
[out]

[case testNoCrashOnPartialVariable3]
from typing import Tuple, TypeVar
T = TypeVar('T')

def f(x: T) -> Tuple[T, T]:
    ...
x = None
(x, x) = f('')
reveal_type(x) # N: Revealed type is "builtins.str"
[builtins fixtures/tuple.pyi]
[out]

[case testInferenceNestedTuplesFromGenericIterable]
from typing import Tuple, TypeVar

T = TypeVar('T')

def make_tuple(elem: T) -> Tuple[T]:
    return (elem,)

def main() -> None:
    ((a, b),) = make_tuple((1, 2))
    reveal_type(a) # N: Revealed type is "builtins.int"
    reveal_type(b) # N: Revealed type is "builtins.int"
[builtins fixtures/tuple.pyi]
[out]

[case testDontMarkUnreachableAfterInferenceUninhabited]
from typing import TypeVar
T = TypeVar('T')
def f() -> T: pass # E: A function returning TypeVar should receive at least one argument containing the same TypeVar

class C:
    x = f() # E: Need type annotation for "x"
    def m(self) -> str:
        return 42 # E: Incompatible return value type (got "int", expected "str")

if bool():
    f()
    1() # E: "int" not callable
[builtins fixtures/list.pyi]
[out]

[case testDontMarkUnreachableAfterInferenceUninhabited2]
from typing import TypeVar, Optional
T = TypeVar('T')
def f(x: Optional[T] = None) -> T: pass

class C:
    x = f() # E: Need type annotation for "x"
    def m(self) -> str:
        return 42 # E: Incompatible return value type (got "int", expected "str")

if bool():
    f()
    1() # E: "int" not callable
[builtins fixtures/list.pyi]
[out]

[case testDontMarkUnreachableAfterInferenceUninhabited3]
from typing import TypeVar, List
T = TypeVar('T')
def f(x: List[T]) -> T: pass

class C:
    x = f([]) # E: Need type annotation for "x"
    def m(self) -> str:
        return 42 # E: Incompatible return value type (got "int", expected "str")

if bool():
    f([])
    1() # E: "int" not callable
[builtins fixtures/list.pyi]
[out]


-- --local-partial-types
-- ---------------------


[case testLocalPartialTypesWithGlobalInitializedToNone]
# flags: --local-partial-types
x = None # E: Need type annotation for "x" (hint: "x: Optional[<type>] = ...")

def f() -> None:
    global x
    x = 1

# TODO: "Any" could be a better type here to avoid multiple error messages
reveal_type(x) # N: Revealed type is "None"

[case testLocalPartialTypesWithGlobalInitializedToNone2]
# flags: --local-partial-types
x = None # E: Need type annotation for "x" (hint: "x: Optional[<type>] = ...")

def f():
    global x
    x = 1

# TODO: "Any" could be a better type here to avoid multiple error messages
reveal_type(x) # N: Revealed type is "None"

[case testLocalPartialTypesWithGlobalInitializedToNone3]
# flags: --local-partial-types --no-strict-optional
x = None

def f() -> None:
    global x
    x = 1 # E: Incompatible types in assignment (expression has type "int", variable has type "str")

x = ''
reveal_type(x) # N: Revealed type is "builtins.str"

[case testLocalPartialTypesWithGlobalInitializedToNoneStrictOptional]
# flags: --local-partial-types
x = None

def f() -> None:
    global x
    x = 1 # E: Incompatible types in assignment (expression has type "int", variable has type "Optional[str]")

x = ''
def g() -> None:
    reveal_type(x) # N: Revealed type is "Union[builtins.str, None]"

[case testLocalPartialTypesWithGlobalInitializedToNone4]
# flags: --local-partial-types --no-strict-optional
a = None

def f() -> None:
    reveal_type(a)  # N: Revealed type is "builtins.str"

# TODO: This should probably be 'builtins.str', since there could be a
#     call that causes a non-None value to be assigned
reveal_type(a)  # N: Revealed type is "None"
a = ''
reveal_type(a)  # N: Revealed type is "builtins.str"
[builtins fixtures/list.pyi]

[case testLocalPartialTypesWithClassAttributeInitializedToNone]
# flags: --local-partial-types
class A:
    x = None # E: Need type annotation for "x" (hint: "x: Optional[<type>] = ...")

    def f(self) -> None:
        self.x = 1

[case testLocalPartialTypesWithClassAttributeInitializedToEmptyDict]
# flags: --local-partial-types
class A:
    x = {}  # E: Need type annotation for "x" (hint: "x: Dict[<type>, <type>] = ...")

    def f(self) -> None:
        self.x[0] = ''

reveal_type(A().x)  # N: Revealed type is "builtins.dict[Any, Any]"
reveal_type(A.x)  # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyList]
# flags: --local-partial-types
a = []

def f() -> None:
    a[0]
    reveal_type(a)  # N: Revealed type is "builtins.list[builtins.int]"

a.append(1)
reveal_type(a) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyList2]
# flags: --local-partial-types
a = [] # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")

def f() -> None:
    a.append(1)
    reveal_type(a)  # N: Revealed type is "builtins.list[Any]"

reveal_type(a) # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyList3]
# flags: --local-partial-types
a = [] # E: Need type annotation for "a" (hint: "a: List[<type>] = ...")

def f():
    a.append(1)

reveal_type(a) # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyDict]
# flags: --local-partial-types
a = {}

def f() -> None:
    a[0]
    reveal_type(a)  # N: Revealed type is "builtins.dict[builtins.int, builtins.str]"

a[0] = ''
reveal_type(a) # N: Revealed type is "builtins.dict[builtins.int, builtins.str]"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyDict2]
# flags: --local-partial-types
a = {} # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")

def f() -> None:
    a[0] = ''
    reveal_type(a)  # N: Revealed type is "builtins.dict[Any, Any]"

reveal_type(a) # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithGlobalInitializedToEmptyDict3]
# flags: --local-partial-types
a = {} # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")

def f():
    a[0] = ''

reveal_type(a) # N: Revealed type is "builtins.dict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithNestedFunction]
# flags: --local-partial-types
def f() -> None:
    a = {}
    def g() -> None:
        a[0] = ''
    reveal_type(a) # N: Revealed type is "builtins.dict[builtins.int, builtins.str]"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithNestedFunction2]
# flags: --local-partial-types
def f() -> None:
    a = []
    def g() -> None:
        a.append(1)
    reveal_type(a) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/list.pyi]

[case testLocalPartialTypesWithNestedFunction3]
# flags: --local-partial-types --no-strict-optional
def f() -> None:
    a = None
    def g() -> None:
        nonlocal a
        a = ''
    reveal_type(a) # N: Revealed type is "builtins.str"
[builtins fixtures/dict.pyi]

[case testLocalPartialTypesWithInheritance]
# flags: --local-partial-types
from typing import Optional

class A:
    x: Optional[str]

class B(A):
    x = None

reveal_type(B.x) # N: Revealed type is "None"

[case testLocalPartialTypesWithInheritance2]
# flags: --local-partial-types
class A:
    x: str

class B(A):
    x = None  # E: Incompatible types in assignment (expression has type "None", base class "A" defined the type as "str")

[case testLocalPartialTypesWithAnyBaseClass]
# flags: --local-partial-types
from typing import Any

A: Any

class B(A):
    x = None

class C(B):
    y = None

[case testLocalPartialTypesInMultipleMroItems]
# flags: --local-partial-types
from typing import Optional

class A:
    x: Optional[str]

class B(A):
    x = None

class C(B):
    x = None

# TODO: Inferring None below is unsafe (https://github.com/python/mypy/issues/3208)
reveal_type(B.x)  # N: Revealed type is "None"
reveal_type(C.x)  # N: Revealed type is "None"

[case testLocalPartialTypesWithInheritance3]
# flags: --local-partial-types
from typing import Optional

class X: pass
class Y(X): pass

class A:
    x: Optional[X]

class B(A):
    x = None
    x = Y()

reveal_type(B.x) # N: Revealed type is "Union[__main__.Y, None]"

[case testLocalPartialTypesBinderSpecialCase]
# flags: --local-partial-types
from typing import List

def f(x): pass

class A:
    x = None  # E: Need type annotation for "x" (hint: "x: Optional[<type>] = ...")

    def f(self, p: List[str]) -> None:
        self.x = f(p)
        f(z for z in p)
[builtins fixtures/list.pyi]

[case testLocalPartialTypesAccessPartialNoneAttribute]
# flags: --local-partial-types
class C:
    a = None  # E: Need type annotation for "a" (hint: "a: Optional[<type>] = ...")

    def f(self, x) -> None:
        C.a.y  # E: Item "None" of "Optional[Any]" has no attribute "y"

[case testLocalPartialTypesAccessPartialNoneAttribute2]
# flags: --local-partial-types
class C:
    a = None  # E: Need type annotation for "a" (hint: "a: Optional[<type>] = ...")

    def f(self, x) -> None:
        self.a.y  # E: Item "None" of "Optional[Any]" has no attribute "y"

-- Special case for assignment to '_'
-- ----------------------------------

[case testUnusedTargetLocal]
def foo() -> None:
    _ = 0
    _ = ''

[case testUnusedTargetNotGlobal]
_ = 0
_ = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")

[case testUnusedTargetNotClass]
# flags: --allow-redefinition
class C:
    _, _ = 0, 0
    _ = ''
reveal_type(C._) # N: Revealed type is "builtins.str"

[case testUnusedTargetNotClass2]
# flags: --disallow-redefinition
class C:
    _, _ = 0, 0
    _ = ''  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
reveal_type(C._) # N: Revealed type is "builtins.int"

[case testUnusedTargetTupleUnpacking]
def foo() -> None:
    _, _ = (0, '')
    _ = 0
    _ = ''
def bar() -> None:
    t = (0, '')
    _, _ = t
    _ = 0
    _ = ''
[builtins fixtures/tuple.pyi]

[case testUnusedTargetMultipleTargets]
def foo() -> None:
    _ = x = 0
    _ = y = ''
    _ = 0
    _ = ''
def bar() -> None:
    x = _ = 0
    y = _ = ''
    _ = 0
    _ = ''
    x + 0
    y + ''
    x + ''  # E: Unsupported operand types for + ("int" and "str")
    y + 0  # E: Unsupported operand types for + ("str" and "int")
[builtins fixtures/primitives.pyi]

[case testUnusedTargetNotImport]
import d, c, b, a
[file _.py]
def f(): pass
[file m.py]
def f(): pass
_ = f
_ = 0  # E: Incompatible types in assignment (expression has type "int", variable has type "Callable[[], Any]")
[file a.py]
def foo() -> None:
    import _
    _.f()
    _ = 0  # E: Incompatible types in assignment (expression has type "int", variable has type Module)
[file b.py]
def foo() -> None:
    import m as _
    _.f()
    _ = 0  # E: Incompatible types in assignment (expression has type "int", variable has type Module)
[file c.py]
def foo() -> None:
    from m import _
    _()
    _ = ''  # E: Incompatible types in assignment (expression has type "str", variable has type "Callable[[], Any]")
[file d.py]
def foo() -> None:
    from m import f as _
    _()
    _ = 0  # E: Incompatible types in assignment (expression has type "int", variable has type "Callable[[], Any]")
[builtins fixtures/module.pyi]

[case testUnderscoreClass]
def foo() -> None:
    class _:
        pass
    _().method()  # E: "_" has no attribute "method"

[case testUnusedTargetForLoop]
def f() -> None:
    a = [(0, '', 0)]
    for _, _, x in a:
        x = 0
        x = ''  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
    _ = 0
    _ = ''
[builtins fixtures/list.pyi]

[case testUnusedTargetWithClause]
class C:
    def __enter__(self) -> int: pass
    def __exit__(self, *args): pass
def f() -> None:
    with C() as _: pass
    _ = 0
    _ = ''
[builtins fixtures/tuple.pyi]

[case testUnusedTargetNotExceptClause]
# Things don't work for except clauses.
# This is due to the implementation, but it's just as well.
def f() -> None:
    try: pass
    except BaseException as _:
        _ = 0  # E: Incompatible types in assignment (expression has type "int", variable has type "BaseException")
        _ = ''  # E: Incompatible types in assignment (expression has type "str", variable has type "BaseException")
[builtins fixtures/exception.pyi]

-- Tests for permissive toplevel checking
-- --------------

[case testPermissiveAttributeOverride1]
# flags: --allow-untyped-globals

class A:
    x = None

class B(A):
    x = 12

class C(A):
    x = '12'

reveal_type(A.x) # N: Revealed type is "Union[Any, None]"
reveal_type(B.x) # N: Revealed type is "builtins.int"
reveal_type(C.x) # N: Revealed type is "builtins.str"

[case testPermissiveAttributeOverride2]
# flags: --allow-untyped-globals

class A:
    x = []

class B(A):
    x = [12]

class C(A):
    x = ['12']

reveal_type(A.x) # N: Revealed type is "builtins.list[Any]"
reveal_type(B.x) # N: Revealed type is "builtins.list[builtins.int]"
reveal_type(C.x) # N: Revealed type is "builtins.list[builtins.str]"

[builtins fixtures/list.pyi]

[case testPermissiveAttribute]
# flags: --allow-untyped-globals

class A:
    x = []
    def f(self) -> None:
        reveal_type(self.x)  # N: Revealed type is "builtins.list[Any]"

[builtins fixtures/list.pyi]

[case testPermissiveGlobalContainer1]
# flags: --allow-untyped-globals --local-partial-types

import a

[file b.py]
x = []
y = {}

def foo() -> None:
    reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
    reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[file a.py]
from b import x, y
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[builtins fixtures/dict.pyi]

[case testPermissiveGlobalContainer2]
# flags: --allow-untyped-globals

import a

[file b.py]
x = []
y = {}

def foo() -> None:
    reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
    reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[file a.py]
from b import x, y
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[builtins fixtures/dict.pyi]

[case testPermissiveGlobalContainer3]
# flags: --allow-untyped-globals --local-partial-types

import a

[file b.py]
x = []
y = {}
z = y


[file a.py]
from b import x, y
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[builtins fixtures/dict.pyi]
[case testPermissiveGlobalContainer4]
# flags: --allow-untyped-globals

import a

[file b.py]
x = []
y = {}
z = y


[file a.py]
from b import x, y
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
reveal_type(y)  # N: Revealed type is "builtins.dict[Any, Any]"

[builtins fixtures/dict.pyi]

[case testInheritedAttributeNoStrictOptional]
# flags: --no-strict-optional
class A:
    x: str

class B(A):
    x = None
    x = ''
    reveal_type(x)  # N: Revealed type is "builtins.str"

[case testIncompatibleInheritedAttributeNoStrictOptional]
# flags: --no-strict-optional
class A:
    x: str

class B(A):
    x = None
    x = 2  # E: Incompatible types in assignment (expression has type "int", base class "A" defined the type as "str")

[case testInheritedAttributeStrictOptional]
class A:
    x: str

class B(A):
    x = None  # E: Incompatible types in assignment (expression has type "None", base class "A" defined the type as "str")
    x = ''

[case testNeedAnnotationForCallable]
from typing import TypeVar, Optional, Callable

T = TypeVar('T')

def f(x: Optional[T] = None) -> Callable[..., T]: ...

x = f()  # E: Need type annotation for "x"
y = x

[case testDontNeedAnnotationForCallable]
from typing import TypeVar, Optional, Callable, NoReturn

T = TypeVar('T')

def f() -> Callable[..., NoReturn]: ...

x = f()
reveal_type(x)  # N: Revealed type is "def (*Any, **Any) -> Never"

[case testDeferralInNestedScopes]


def g() -> None:
    def f() -> None:
        x + 'no way'  # E: Unsupported operand types for + ("int" and "str")
    x = int()
    f()

[case testDeferralOfMemberNested]
from typing import Tuple

def f() -> None:
    c: C
    t: Tuple[str, Tuple[str, str]]
    x, (y, c.a) = t  # E: Incompatible types in assignment (expression has type "str", variable has type "int")

class C:
    def __init__(self, a: int) -> None:
        self.a = a
[builtins fixtures/tuple.pyi]

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

class A: ...
class B(A): ...

T = TypeVar('T', bound=A)
class Z(Generic[T]):
    def __init__(self, y: T) -> None:
        self.y = y

F = TypeVar('F', bound=A)

def q1(x: Union[F, Z[F]]) -> F:
    if isinstance(x, Z):
        return x.y
    else:
        return x

def q2(x: Union[Z[F], F]) -> F:
    if isinstance(x, Z):
        return x.y
    else:
        return x

b: B
reveal_type(q1(b))  # N: Revealed type is "__main__.B"
reveal_type(q2(b))  # N: Revealed type is "__main__.B"

z: Z[B]
reveal_type(q1(z))  # N: Revealed type is "__main__.B"
reveal_type(q2(z))  # N: Revealed type is "__main__.B"

reveal_type(q1(Z(b)))  # N: Revealed type is "__main__.B"
reveal_type(q2(Z(b)))  # N: Revealed type is "__main__.B"
[builtins fixtures/isinstancelist.pyi]

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

T = TypeVar('T')
T_co = TypeVar('T_co', covariant=True)

class Cov(Generic[T_co]): ...
class Inv(Cov[T]): ...

X = Union[Cov[T], Inv[T]]

def f(x: X[T]) -> T: ...
x: Inv[int]
reveal_type(f(x))  # N: Revealed type is "builtins.int"

[case testOptionalTypeVarAgainstOptional]
from typing import Optional, TypeVar, Iterable, Iterator, List

_T = TypeVar('_T')

def filter(__function: None, __iterable: Iterable[Optional[_T]]) -> List[_T]: ...

x: Optional[str]

y = filter(None, [x])
reveal_type(y)  # N: Revealed type is "builtins.list[builtins.str]"
[builtins fixtures/list.pyi]

[case testPartialDefaultDict]
from collections import defaultdict
x = defaultdict(int)
x[''] = 1
reveal_type(x) # N: Revealed type is "collections.defaultdict[builtins.str, builtins.int]"

y = defaultdict(int) # E: Need type annotation for "y"

z = defaultdict(int)  # E: Need type annotation for "z"
z[''] = ''
reveal_type(z) # N: Revealed type is "collections.defaultdict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictInconsistentValueTypes]
from collections import defaultdict
a = defaultdict(int)  # E: Need type annotation for "a"
a[''] = ''
a[''] = 1
reveal_type(a) # N: Revealed type is "collections.defaultdict[builtins.str, builtins.int]"
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictListValue]
# flags: --no-strict-optional
from collections import defaultdict
a = defaultdict(list)
a['x'].append(1)
reveal_type(a) # N: Revealed type is "collections.defaultdict[builtins.str, builtins.list[builtins.int]]"

b = defaultdict(lambda: [])
b[1].append('x')
reveal_type(b) # N: Revealed type is "collections.defaultdict[builtins.int, builtins.list[builtins.str]]"
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictListValueStrictOptional]
from collections import defaultdict
a = defaultdict(list)
a['x'].append(1)
reveal_type(a) # N: Revealed type is "collections.defaultdict[builtins.str, builtins.list[builtins.int]]"

b = defaultdict(lambda: [])
b[1].append('x')
reveal_type(b) # N: Revealed type is "collections.defaultdict[builtins.int, builtins.list[builtins.str]]"
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictSpecialCases]
from collections import defaultdict
class A:
    def f(self) -> None:
        self.x = defaultdict(list)
        self.x['x'].append(1)
        reveal_type(self.x) # N: Revealed type is "collections.defaultdict[builtins.str, builtins.list[builtins.int]]"
        self.y = defaultdict(list)  # E: Need type annotation for "y"
        s = self
        s.y['x'].append(1)

x = {} # E: Need type annotation for "x" (hint: "x: Dict[<type>, <type>] = ...")
x['x'].append(1)

y = defaultdict(list)  # E: Need type annotation for "y"
y[[]].append(1)
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictSpecialCases2]
from collections import defaultdict

x = defaultdict(lambda: [1]) # E: Need type annotation for "x"
x[1].append('') # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
reveal_type(x) # N: Revealed type is "collections.defaultdict[Any, builtins.list[builtins.int]]"

xx = defaultdict(lambda: {'x': 1}) # E: Need type annotation for "xx"
xx[1]['z'] = 3
reveal_type(xx) # N: Revealed type is "collections.defaultdict[Any, builtins.dict[builtins.str, builtins.int]]"

y = defaultdict(dict)  # E: Need type annotation for "y"
y['x'][1] = [3]

z = defaultdict(int) # E: Need type annotation for "z"
z[1].append('')
reveal_type(z) # N: Revealed type is "collections.defaultdict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testPartialDefaultDictSpecialCase3]
from collections import defaultdict

x = defaultdict(list)
x['a'] = [1, 2, 3]
reveal_type(x)  # N: Revealed type is "collections.defaultdict[builtins.str, builtins.list[builtins.int]]"

y = defaultdict(list)  # E: Need type annotation for "y"
y['a'] = []
reveal_type(y)  # N: Revealed type is "collections.defaultdict[Any, Any]"
[builtins fixtures/dict.pyi]

[case testInferCallableReturningNone1]
# flags: --no-strict-optional
from typing import Callable, TypeVar

T = TypeVar("T")

def f(x: Callable[[], T]) -> T:
    return x()

reveal_type(f(lambda: None))  # N: Revealed type is "None"
reveal_type(f(lambda: 1))  # N: Revealed type is "builtins.int"

def g() -> None: pass

reveal_type(f(g))  # N: Revealed type is "None"

[case testInferCallableReturningNone2]
from typing import Callable, TypeVar

T = TypeVar("T")

def f(x: Callable[[], T]) -> T:
    return x()

reveal_type(f(lambda: None))  # N: Revealed type is "None"
reveal_type(f(lambda: 1))  # N: Revealed type is "builtins.int"

def g() -> None: pass

reveal_type(f(g))  # N: Revealed type is "None"

[case testInferredTypeIsSimpleNestedList]
from typing import Any, Union, List

y: Union[List[Any], Any]
x: Union[List[Any], Any]
x = [y]
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferredTypeIsSimpleNestedIterable]
from typing import Any, Union, Iterable

y: Union[Iterable[Any], Any]
x: Union[Iterable[Any], Any]
x = [y]
reveal_type(x)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferredTypeIsSimpleNestedListLoop]
from typing import Any, Union, List

def test(seq: List[Union[List, Any]]) -> None:
    k: Union[List, Any]
    for k in seq:
        if bool():
            k = [k]
            reveal_type(k)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testInferredTypeIsSimpleNestedIterableLoop]
from typing import Any, Union, List, Iterable

def test(seq: List[Union[Iterable, Any]]) -> None:
    k: Union[Iterable, Any]
    for k in seq:
        if bool():
            k = [k]
            reveal_type(k)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testErasedTypeRuntimeCoverage]
# https://github.com/python/mypy/issues/11913
from typing import TypeVar, Type, Generic, Callable, Iterable

class DataType: ...

T1 = TypeVar('T1')
T2 = TypeVar("T2", bound=DataType)

def map(__func: T1) -> None: ...

def collection_from_dict_value(model: Type[T2]) -> None:
    map(lambda i: i if isinstance(i, model) else i)
[builtins fixtures/isinstancelist.pyi]

[case testRegression11705_Strict]
# See: https://github.com/python/mypy/issues/11705
from typing import Dict, Optional, NamedTuple
class C(NamedTuple):
    x: int

t: Optional[C]
d: Dict[C, bytes]
x = t and d[t]
reveal_type(x)  # N: Revealed type is "Union[None, builtins.bytes]"
if x:
    reveal_type(x)  # N: Revealed type is "builtins.bytes"
[builtins fixtures/dict.pyi]

[case testRegression11705_NoStrict]
# flags: --no-strict-optional
# See: https://github.com/python/mypy/issues/11705
from typing import Dict, Optional, NamedTuple
class C(NamedTuple):
    x: int

t: Optional[C]
d: Dict[C, bytes]
x = t and d[t]
reveal_type(x)  # N: Revealed type is "builtins.bytes"
if x:
    reveal_type(x)  # N: Revealed type is "builtins.bytes"
[builtins fixtures/dict.pyi]

[case testSuggestPep604AnnotationForPartialNone]
# flags: --local-partial-types --python-version 3.10
x = None # E: Need type annotation for "x" (hint: "x: <type> | None = ...")

[case testTupleContextFromIterable]
from typing import TypeVar, Iterable, List, Union

T = TypeVar("T")

def foo(x: List[T]) -> List[T]: ...
x: Iterable[List[Union[int, str]]] = (foo([1]), foo(["a"]))
[builtins fixtures/tuple.pyi]

[case testTupleContextFromIterable2]
from typing import Dict, Iterable, Tuple, Union

def foo(x: Union[Tuple[str, Dict[str, int], str], Iterable[object]]) -> None: ...
foo(("a", {"a": "b"}, "b"))
[builtins fixtures/dict.pyi]

[case testUseSupertypeAsInferenceContext]
from typing import List, Optional

class B:
    x: List[Optional[int]]

class C(B):
    x = [1]

reveal_type(C().x)  # N: Revealed type is "builtins.list[Union[builtins.int, None]]"
[builtins fixtures/list.pyi]

[case testUseSupertypeAsInferenceContextInvalidType]
from typing import List
class P:
    x: List[int]
class C(P):
    x = ['a']  # E: List item 0 has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testUseSupertypeAsInferenceContextPartial]
from typing import List

class A:
    x: List[str]

class B(A):
    x = []

reveal_type(B().x)  # N: Revealed type is "builtins.list[builtins.str]"
[builtins fixtures/list.pyi]

[case testUseSupertypeAsInferenceContextPartialError]
class A:
    x = ['a', 'b']

class B(A):
    x = []
    x.append(2)  # E: Argument 1 to "append" of "list" has incompatible type "int"; expected "str"
[builtins fixtures/list.pyi]

[case testUseSupertypeAsInferenceContextPartialErrorProperty]
from typing import List

class P:
    @property
    def x(self) -> List[int]: ...
class C(P):
    x = []

C.x.append("no")  # E: Argument 1 to "append" of "list" has incompatible type "str"; expected "int"
[builtins fixtures/list.pyi]

[case testUseSupertypeAsInferenceContextConflict]
from typing import List
class P:
    x: List[int]
class M:
    x: List[str]
class C(P, M):
    x = []  # E: Need type annotation for "x" (hint: "x: List[<type>] = ...")
reveal_type(C.x)  # N: Revealed type is "builtins.list[Any]"
[builtins fixtures/list.pyi]

[case testNoPartialInSupertypeAsContext]
class A:
    args = {}  # E: Need type annotation for "args" (hint: "args: Dict[<type>, <type>] = ...")
    def f(self) -> None:
        value = {1: "Hello"}
        class B(A):
            args = value
[builtins fixtures/dict.pyi]

[case testInferSimpleLiteralInClassBodyCycle]
import a
[file a.py]
import b
reveal_type(b.B.x)
class A:
    x = 42
[file b.py]
import a
reveal_type(a.A.x)
class B:
    x = 42
[out]
tmp/b.py:2: note: Revealed type is "builtins.int"
tmp/a.py:2: note: Revealed type is "builtins.int"

[case testUnionTypeCallableInference]
from typing import Callable, Type, TypeVar, Union

class A:
    def __init__(self, x: str) -> None: ...

T = TypeVar("T")
def type_or_callable(value: T, tp: Union[Type[T], Callable[[int], T]]) -> T: ...
reveal_type(type_or_callable(A("test"), A))  # N: Revealed type is "__main__.A"

[case testUpperBoundAsInferenceFallback]
from typing import Callable, TypeVar, Any, Mapping, Optional
T = TypeVar("T", bound=Mapping[str, Any])
def raises(opts: Optional[T]) -> T: pass
def assertRaises(cb: Callable[..., object]) -> None: pass
assertRaises(raises)  # OK
[builtins fixtures/dict.pyi]

[case testJoinWithAnyFallback]
from unknown import X  # type: ignore[import]

class A: ...
class B(X, A): ...
class C(B): ...
class D(C): ...
class E(D): ...

reveal_type([E(), D()])  # N: Revealed type is "builtins.list[__main__.D]"
reveal_type([D(), E()])  # N: Revealed type is "builtins.list[__main__.D]"

[case testCallableInferenceAgainstCallablePosVsStar]
from typing import TypeVar, Callable, Tuple

T = TypeVar('T')
S = TypeVar('S')

def f(x: Callable[[T, S], None]) -> Tuple[T, S]: ...
def g(*x: int) -> None: ...
reveal_type(f(g))  # N: Revealed type is "Tuple[builtins.int, builtins.int]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableStarVsPos]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T, S]):
    def __call__(self, __x: T, *args: S) -> None: ...

def f(x: Call[T, S]) -> Tuple[T, S]: ...
def g(*x: int) -> None: ...
reveal_type(f(g))  # N: Revealed type is "Tuple[builtins.int, builtins.int]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableNamedVsStar]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T, S]):
    def __call__(self, *, x: T, y: S) -> None: ...

def f(x: Call[T, S]) -> Tuple[T, S]: ...
def g(**kwargs: int) -> None: ...
reveal_type(f(g))  # N: Revealed type is "Tuple[builtins.int, builtins.int]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableStarVsNamed]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T, S]):
    def __call__(self, *, x: T, **kwargs: S) -> None: ...

def f(x: Call[T, S]) -> Tuple[T, S]: ...
def g(**kwargs: int) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[builtins.int, builtins.int]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableNamedVsNamed]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T, S]):
    def __call__(self, *, x: T, y: S) -> None: ...

def f(x: Call[T, S]) -> Tuple[T, S]: ...

# Note: order of names is different w.r.t. protocol
def g(*, y: int, x: str) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[builtins.str, builtins.int]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallablePosOnlyVsNamed]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T]):
    def __call__(self, *, x: T) -> None: ...

def f(x: Call[T]) -> Tuple[T, T]: ...

def g(__x: str) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[Never, Never]" \
                   # E: Argument 1 to "f" has incompatible type "Callable[[str], None]"; expected "Call[Never]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableNamedVsPosOnly]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T]):
    def __call__(self, __x: T) -> None: ...

def f(x: Call[T]) -> Tuple[T, T]: ...

def g(*, x: str) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[Never, Never]" \
                   # E: Argument 1 to "f" has incompatible type "Callable[[NamedArg(str, 'x')], None]"; expected "Call[Never]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallablePosOnlyVsKwargs]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T]):
    def __call__(self, __x: T) -> None: ...

def f(x: Call[T]) -> Tuple[T, T]: ...

def g(**x: str) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[Never, Never]" \
                   # E: Argument 1 to "f" has incompatible type "Callable[[KwArg(str)], None]"; expected "Call[Never]"
[builtins fixtures/list.pyi]

[case testCallableInferenceAgainstCallableNamedVsArgs]
from typing import TypeVar, Callable, Tuple, Protocol

T = TypeVar('T', contravariant=True)
S = TypeVar('S', contravariant=True)

class Call(Protocol[T]):
    def __call__(self, *, x: T) -> None: ...

def f(x: Call[T]) -> Tuple[T, T]: ...

def g(*args: str) -> None: pass
reveal_type(f(g))  # N: Revealed type is "Tuple[Never, Never]" \
                   # E: Argument 1 to "f" has incompatible type "Callable[[VarArg(str)], None]"; expected "Call[Never]"
[builtins fixtures/list.pyi]

[case testInferenceAgainstTypeVarActualBound]
from typing import Callable, TypeVar

T = TypeVar("T")
S = TypeVar("S")
def test(f: Callable[[T], S]) -> Callable[[T], S]: ...

F = TypeVar("F", bound=Callable[..., object])
def dec(f: F) -> F:
    reveal_type(test(f))  # N: Revealed type is "def (Any) -> builtins.object"
    return f

[case testInferenceAgainstTypeVarActualUnionBound]
from typing import Protocol, TypeVar, Union

T_co = TypeVar("T_co", covariant=True)
class SupportsFoo(Protocol[T_co]):
    def foo(self) -> T_co: ...

class A:
    def foo(self) -> A: ...
class B:
    def foo(self) -> B: ...

def foo(f: SupportsFoo[T_co]) -> T_co: ...

ABT = TypeVar("ABT", bound=Union[A, B])
def simpler(k: ABT):
    foo(k)

[case testInferenceWorksWithEmptyCollectionsNested]
from typing import List, TypeVar, NoReturn
T = TypeVar('T')
def f(a: List[T], b: List[T]) -> T: pass
x = ["yes"]
reveal_type(f(x, []))  # N: Revealed type is "builtins.str"
reveal_type(f(["yes"], []))  # N: Revealed type is "builtins.str"

empty: List[NoReturn]
f(x, empty)  # E: Cannot infer type argument 1 of "f"
f(["no"], empty)  # E: Cannot infer type argument 1 of "f"
[builtins fixtures/list.pyi]

[case testInferenceWorksWithEmptyCollectionsUnion]
from typing import Any, Dict, NoReturn, NoReturn, Union

def foo() -> Union[Dict[str, Any], Dict[int, Any]]:
    return {}

empty: Dict[NoReturn, NoReturn]
def bar() -> Union[Dict[str, Any], Dict[int, Any]]:
    return empty
[builtins fixtures/dict.pyi]

[case testUpperBoundInferenceFallbackNotOverused]
from typing import TypeVar, Protocol, List

S = TypeVar("S", covariant=True)
class Foo(Protocol[S]):
    def foo(self) -> S: ...
def foo(x: Foo[S]) -> S: ...

T = TypeVar("T", bound="Base")
class Base:
    def foo(self: T) -> T: ...
class C(Base):
    pass

def f(values: List[T]) -> T: ...
x = foo(f([C()]))
reveal_type(x)  # N: Revealed type is "__main__.C"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallableUnion]
from typing import Callable, TypeVar, List, Union

T = TypeVar("T")
S = TypeVar("S")

def dec(f: Callable[[S], T]) -> Callable[[S], List[T]]: ...
@dec
def func(arg: T) -> Union[T, str]:
    ...
reveal_type(func)  # N: Revealed type is "def [S] (S`1) -> builtins.list[Union[S`1, builtins.str]]"
reveal_type(func(42))  # N: Revealed type is "builtins.list[Union[builtins.int, builtins.str]]"

def dec2(f: Callable[[S], List[T]]) -> Callable[[S], T]: ...
@dec2
def func2(arg: T) -> List[Union[T, str]]:
    ...
reveal_type(func2)  # N: Revealed type is "def [S] (S`4) -> Union[S`4, builtins.str]"
reveal_type(func2(42))  # N: Revealed type is "Union[builtins.int, builtins.str]"
[builtins fixtures/list.pyi]

[case testInferenceAgainstGenericCallbackProtoMultiple]
from typing import Callable, Protocol, TypeVar
from typing_extensions import Concatenate, ParamSpec

V_co = TypeVar("V_co", covariant=True)
class Metric(Protocol[V_co]):
    def __call__(self) -> V_co: ...

T = TypeVar("T")
P = ParamSpec("P")
def simple_metric(func: Callable[Concatenate[int, P], T]) -> Callable[P, T]: ...

@simple_metric
def Negate(count: int, /, metric: Metric[float]) -> float: ...
@simple_metric
def Combine(count: int, m1: Metric[T], m2: Metric[T], /, *more: Metric[T]) -> T: ...

reveal_type(Negate)  # N: Revealed type is "def (metric: __main__.Metric[builtins.float]) -> builtins.float"
reveal_type(Combine)  # N: Revealed type is "def [T] (def () -> T`5, def () -> T`5, *more: def () -> T`5) -> T`5"

def m1() -> float: ...
def m2() -> float: ...
reveal_type(Combine(m1, m2))  # N: Revealed type is "builtins.float"
[builtins fixtures/list.pyi]

[case testInferenceWithUninhabitedType]
from typing import Dict, Generic, List, Never, TypeVar

T = TypeVar("T")

class A(Generic[T]): ...
class B(Dict[T, T]): ...

def func1(a: A[T], b: T) -> T: ...
def func2(a: T, b: A[T]) -> T: ...

def a1(a: A[Dict[str, int]]) -> None:
    reveal_type(func1(a, {}))  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
    reveal_type(func2({}, a))  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"

def a2(check: bool, a: B[str]) -> None:
    reveal_type(a if check else {})  # N: Revealed type is "builtins.dict[builtins.str, builtins.str]"

def a3() -> None:
    a = {}  # E: Need type annotation for "a" (hint: "a: Dict[<type>, <type>] = ...")
    b = {1: {}}  # E: Need type annotation for "b"
    c = {1: {}, 2: {"key": {}}}  # E: Need type annotation for "c"
    reveal_type(a)  # N: Revealed type is "builtins.dict[Any, Any]"
    reveal_type(b)  # N: Revealed type is "builtins.dict[builtins.int, builtins.dict[Any, Any]]"
    reveal_type(c)  # N: Revealed type is "builtins.dict[builtins.int, builtins.dict[builtins.str, builtins.dict[Any, Any]]]"

def a4(x: List[str], y: List[Never]) -> None:
    z1 = [x, y]
    z2 = [y, x]
    reveal_type(z1)  # N: Revealed type is "builtins.list[builtins.object]"
    reveal_type(z2)  # N: Revealed type is "builtins.list[builtins.object]"
    z1[1].append("asdf")  # E: "object" has no attribute "append"
[builtins fixtures/dict.pyi]