check-functions.test

-- Test cases for the type checker related to functions, function types and
-- calls.

-- See also check-varargs.test.


-- Callable type basics
-- --------------------


[case testCallingVariableWithFunctionType]
from typing import Callable
f: Callable[[A], B]
a: A
b: B
if int():
    a = f(a)    # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    b = f(b)    # E: Argument 1 has incompatible type "B"; expected "A"
if int():
    b = f()     # E: Too few arguments
if int():
    b = f(a, a) # E: Too many arguments
if int():
    b = f(a)

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

[case testKeywordOnlyArgumentOrderInsensitivity]
import typing

class A(object):
    def f(self, *, a: int, b: str) -> None: pass

class B(A):
    def f(self, *, b: str, a: int) -> None: pass

class C(A):
    def f(self, *, b: int, a: str) -> None: pass  # Fail
[out]
main:10: error: Argument 1 of "f" is incompatible with supertype "A"; supertype defines the argument type as "str"
main:10: note: This violates the Liskov substitution principle
main:10: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
main:10: error: Argument 2 of "f" is incompatible with supertype "A"; supertype defines the argument type as "int"

[case testPositionalOverridingArgumentNameInsensitivity]
import typing

class A(object):
    def f(self, a: int, b: str) -> None: pass

class B(A):
    def f(self, b: str, a: int) -> None: pass # E: Argument 1 of "f" is incompatible with supertype "A"; supertype defines the argument type as "int" \
                                              # N: This violates the Liskov substitution principle \
                                              # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides \
                                              # E: Argument 2 of "f" is incompatible with supertype "A"; supertype defines the argument type as "str"

class C(A):
    def f(self, foo: int, bar: str) -> None: pass


[case testPositionalOverridingArgumentNamesCheckedWhenMismatchingPos]
import typing

class A(object):
    def f(self, a: int, b: str) -> None: pass

class B(A):
    def f(self, b: int, a: str) -> None: pass  # Fail
[out]
main:7: error: Signature of "f" incompatible with supertype "A"
main:7: note:      Superclass:
main:7: note:          def f(self, a: int, b: str) -> None
main:7: note:      Subclass:
main:7: note:          def f(self, b: int, a: str) -> None

[case testSubtypingFunctionTypes]
from typing import Callable

class A: pass
class B(A): pass

f: Callable[[B], A]
g: Callable[[A], A]  # subtype of f
h: Callable[[B], B]  # subtype of f
if int():
    g = h  # E: Incompatible types in assignment (expression has type "Callable[[B], B]", variable has type "Callable[[A], A]")
if int():
    h = f  # E: Incompatible types in assignment (expression has type "Callable[[B], A]", variable has type "Callable[[B], B]")
if int():
    h = g  # E: Incompatible types in assignment (expression has type "Callable[[A], A]", variable has type "Callable[[B], B]")
if int():
    g = f  # E: Incompatible types in assignment (expression has type "Callable[[B], A]", variable has type "Callable[[A], A]")
if int():
    f = g
if int():
    f = h
if int():
    f = f
if int():
    g = g
if int():
    h = h

[case testSubtypingFunctionsDoubleCorrespondence]
def l(x) -> None: ...
def r(__x, *, x) -> None: ...
r = l  # E: Incompatible types in assignment (expression has type "Callable[[Any], None]", variable has type "def r(Any, /, *, x: Any) -> None")

[case testSubtypingFunctionsDoubleCorrespondenceNamedOptional]
def l(x) -> None: ...
def r(__x, *, x = 1) -> None: ...
r = l  # E: Incompatible types in assignment (expression has type "Callable[[Any], None]", variable has type "def r(Any, /, *, x: Any = ...) -> None")

[case testSubtypingFunctionsDoubleCorrespondenceBothNamedOptional]
def l(x = 1) -> None: ...
def r(__x, *, x = 1) -> None: ...
r = l  # E: Incompatible types in assignment (expression has type "Callable[[Any], None]", variable has type "def r(Any, /, *, x: Any = ...) -> None")

[case testSubtypingFunctionsTrivialSuffixRequired]
def l(__x) -> None: ...
def r(x, *args, **kwargs) -> None: ...

r = l  # E: Incompatible types in assignment (expression has type "Callable[[Any], None]", variable has type "def r(x: Any, *args: Any, **kwargs: Any) -> None")
[builtins fixtures/dict.pyi]

[case testSubtypingFunctionsTrivialSuffixOptional]
def l(__x = 1) -> None: ...
def r(x = 1, *args, **kwargs) -> None: ...

r = l  # E: Incompatible types in assignment (expression has type "def l(Any = ..., /) -> None", variable has type "def r(x: Any = ..., *args: Any, **kwargs: Any) -> None")
[builtins fixtures/dict.pyi]

[case testSubtypingFunctionsRequiredLeftArgNotPresent]
def l(x, y) -> None: ...
def r(x) -> None: ...
r = l  # E: Incompatible types in assignment (expression has type "Callable[[Any, Any], None]", variable has type "Callable[[Any], None]")

[case testSubtypingFunctionsImplicitNames]
from typing import Any

def f(a, b): pass
def g(c: Any, d: Any) -> Any: pass

ff = f
gg = g

gg = f
ff = g

[case testSubtypingFunctionsDefaultsNames]
from typing import Callable

def f(a: int, b: str) -> None: pass
f_nonames: Callable[[int, str], None]
def g(a: int, b: str = "") -> None: pass
def h(aa: int, b: str = "") -> None: pass

ff_nonames = f_nonames
ff = f
gg = g
hh = h

if int():
    ff = gg
if int():
    ff_nonames = ff
if int():
    ff_nonames = f_nonames # reset
if int():
    ff = ff_nonames # E: Incompatible types in assignment (expression has type "Callable[[int, str], None]", variable has type "def f(a: int, b: str) -> None")
if int():
    ff = f # reset
if int():
    gg = ff # E: Incompatible types in assignment (expression has type "def f(a: int, b: str) -> None", variable has type "def g(a: int, b: str = ...) -> None")
if int():
    gg = hh # E: Incompatible types in assignment (expression has type "def h(aa: int, b: str = ...) -> None", variable has type "def g(a: int, b: str = ...) -> None")

[case testSubtypingFunctionsArgsKwargs]
from typing import Any, Callable

def everything(*args: Any, **kwargs: Any) -> None: pass
everywhere: Callable[..., None]

def specific_1(a: int, b: str) -> None: pass
def specific_2(a: int, *, b: str) -> None: pass

ss_1 = specific_1
ss_2 = specific_2
ee_def = everything
ee_var = everywhere

if int():
    ss_1 = ee_def
if int():
    ss_1 = specific_1
if int():
    ss_2 = ee_def
if int():
    ss_2 = specific_2
if int():
    ee_def = everywhere
if int():
    ee_def = everything
if int():
    ee_var = everything
if int():
    ee_var = everywhere

if int():
    ee_var = specific_1
if int():
    ee_def = specific_1

[builtins fixtures/dict.pyi]

[case testSubtypingFunctionsDecorated]
from typing import Any

# untyped decorator
def deco(f): pass

class A:
    @deco
    def f(self) -> Any:
        pass

class B(A):
    @deco
    def f(self) -> Any:
        pass

[builtins fixtures/list.pyi]


[case testLackOfNames]
def f(__a: int, __b: str) -> None: pass
def g(a: int, b: str) -> None: pass

ff = f
gg = g

if int():
    ff = g
if int():
    gg = f # E: Incompatible types in assignment (expression has type "Callable[[int, str], None]", variable has type "def g(a: int, b: str) -> None")

[case testLackOfNamesFastparse]
def f(__a: int, __b: str) -> None: pass
def g(a: int, b: str) -> None: pass

ff = f
gg = g

if int():
    ff = g
if int():
    gg = f # E: Incompatible types in assignment (expression has type "Callable[[int, str], None]", variable has type "def g(a: int, b: str) -> None")

[case testFunctionTypeCompatibilityWithOtherTypes]
# flags: --no-strict-optional
from typing import Callable
f = None # type: Callable[[], None]
a, o = None, None # type: (A, object)
if int():
    a = f   # E: Incompatible types in assignment (expression has type "Callable[[], None]", variable has type "A")
if int():
    f = a   # E: Incompatible types in assignment (expression has type "A", variable has type "Callable[[], None]")
if int():
    f = o   # E: Incompatible types in assignment (expression has type "object", variable has type "Callable[[], None]")
if int():
    f = f() # E: Function does not return a value (it only ever returns None)

if int():
    f = f
if int():
    f = None
if int():
    o = f

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

[case testReturnEmptyTuple]
from typing import Tuple
def f(x): # type: (int) -> () # E: Syntax error in type annotation \
                              # N: Suggestion: Use Tuple[()] instead of () for an empty tuple, or None for a function without a return value
   pass

def g(x: int) -> Tuple[()]:
   pass
[builtins fixtures/tuple.pyi]

[case testFunctionSubtypingWithVoid]
from typing import Callable
f: Callable[[], None]
g: Callable[[], object]
if int():
    f = g  # E: Incompatible types in assignment (expression has type "Callable[[], object]", variable has type "Callable[[], None]")
if int():
    g = f  # OK

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

[case testFunctionSubtypingWithMultipleArgs]
from typing import Callable
f: Callable[[A, A], None]
g: Callable[[A, B], None]
h: Callable[[B, B], None]
if int():
    f = g  # E: Incompatible types in assignment (expression has type "Callable[[A, B], None]", variable has type "Callable[[A, A], None]")
if int():
    f = h  # E: Incompatible types in assignment (expression has type "Callable[[B, B], None]", variable has type "Callable[[A, A], None]")
if int():
    g = h  # E: Incompatible types in assignment (expression has type "Callable[[B, B], None]", variable has type "Callable[[A, B], None]")
if int():
    g = f
if int():
    h = f
if int():
    h = g
if int():
    f = f
if int():
    g = g
if int():
    h = h

class A: pass
class B(A): pass

[case testFunctionTypesWithDifferentArgumentCounts]
from typing import Callable
f: Callable[[], None]
g: Callable[[A], None]
h: Callable[[A, A], None]

if int():
    f = g   # E: Incompatible types in assignment (expression has type "Callable[[A], None]", variable has type "Callable[[], None]")
if int():
    f = h   # E: Incompatible types in assignment (expression has type "Callable[[A, A], None]", variable has type "Callable[[], None]")
if int():
    h = f   # E: Incompatible types in assignment (expression has type "Callable[[], None]", variable has type "Callable[[A, A], None]")
if int():
    h = g   # E: Incompatible types in assignment (expression has type "Callable[[A], None]", variable has type "Callable[[A, A], None]")

if int():
    f = f
if int():
    g = g
if int():
    h = h

class A: pass
[out]

[case testCompatibilityOfSimpleTypeObjectWithStdType]
class A:
    def __init__(self, a: 'A') -> None: pass

def f() -> None: pass

t: type
a: A

if int():
    a = A # E: Incompatible types in assignment (expression has type "type[A]", variable has type "A")
if int():
    t = f # E: Incompatible types in assignment (expression has type "Callable[[], None]", variable has type "type")
if int():
    t = A

[case testFunctionTypesWithOverloads]
from foo import *
[file foo.pyi]
from typing import Callable, overload
f: Callable[[AA], A]
g: Callable[[B], B]
h: Callable[[A], AA]

if int():
    h = i  # E: Incompatible types in assignment (expression has type overloaded function, variable has type "Callable[[A], AA]")
if int():
    f = j

if int():
    f = i
if int():
    g = i
if int():
    g = j

class A: pass
class AA(A): pass

class B: pass

@overload
def i(x: AA) -> A:
    pass
@overload
def i(x: B) -> B:
    pass

@overload
def j(x: B) -> B:
    pass
@overload
def j(x: A) -> AA:
    pass

[case testOverloadWithThreeItems]
from foo import *
[file foo.pyi]
from typing import Callable, overload
g1: Callable[[A], A]
g2: Callable[[B], B]
g3: Callable[[C], C]
g4: Callable[[A], B]
a: A
b: B
c: C

if int():
    b = f(a)  # E: Incompatible types in assignment (expression has type "A", variable has type "B")
if int():
    a = f(b)  # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    b = f(c)  # E: Incompatible types in assignment (expression has type "C", variable has type "B")
if int():
    g4 = f    # E: Incompatible types in assignment (expression has type overloaded function, variable has type "Callable[[A], B]")

if int():
    g1 = f
if int():
    g2 = f
if int():
    g3 = f
if int():
    a = f(a)
if int():
    b = f(b)
if int():
    c = f(c)

class A: pass
class B: pass
class C: pass

@overload
def f(x: A) -> A: pass
@overload
def f(x: B) -> B: pass
@overload
def f(x: C) -> C: pass
[builtins fixtures/tuple.pyi]

[case testInferConstraintsUnequalLengths]
from typing import Any, Callable, List
def f(fields: List[Callable[[Any], Any]]): pass
class C: pass
f([C])  # E: List item 0 has incompatible type "type[C]"; expected "Callable[[Any], Any]"
class D:
    def __init__(self, a, b): pass
f([D])  # E: List item 0 has incompatible type "type[D]"; expected "Callable[[Any], Any]"
[builtins fixtures/list.pyi]

[case testSubtypingTypeTypeAsCallable]
from typing import Callable, Type
class A: pass
x: Callable[..., A]
y: Type[A]
x = y

[case testSubtypingCallableAsTypeType]
from typing import Callable, Type
class A: pass
x: Callable[..., A]
y: Type[A]
if int():
    y = x  # E: Incompatible types in assignment (expression has type "Callable[..., A]", variable has type "type[A]")

-- Default argument values
-- -----------------------


[case testCallingFunctionsWithDefaultArgumentValues]
# flags: --implicit-optional --no-strict-optional
class A: pass
class AA(A): pass
class B: pass

def f(x: 'A'  =  None) -> 'B': pass

a, b = None, None # type: (A, B)
if int():
    a = f()     # E: Incompatible types in assignment (expression has type "B", variable has type "A")
if int():
    b = f(b)    # E: Argument 1 to "f" has incompatible type "B"; expected "A | None"
if int():
    b = f(a, a) # E: Too many arguments for "f"

if int():
    b = f()
if int():
    b = f(a)
if int():
    b = f(AA())

[builtins fixtures/tuple.pyi]

[case testDefaultArgumentExpressions]
import typing
class B: pass
class A: pass

def f(x: 'A' = A()) -> None:
    b = x # type: B # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    a = x # type: A
[out]

[case testDefaultArgumentExpressions2]
import typing
class B: pass
class A: pass

def f(x: 'A' = B()) -> None: # E: Incompatible default for argument "x" (default has type "B", argument has type "A")
    b = x # type: B      # E: Incompatible types in assignment (expression has type "A", variable has type "B")
    a = x # type: A
[case testDefaultArgumentExpressionsGeneric]
from typing import TypeVar
T = TypeVar('T', bound='A')

class B: pass
class A: pass

def f(x: T = B()) -> None: # E: Incompatible default for argument "x" (default has type "B", argument has type "T")
    b = x # type: B      # E: Incompatible types in assignment (expression has type "T", variable has type "B")
    a = x # type: A
[case testDefaultArgumentsWithSubtypes]
import typing
class A: pass
class B(A): pass

def f(x: 'B' = A()) -> None: # E: Incompatible default for argument "x" (default has type "A", argument has type "B")
    pass
def g(x: 'A' = B()) -> None:
    pass
[out]

[case testMultipleDefaultArgumentExpressions]
import typing
class A: pass
class B: pass

def f(x: 'A' = B(), y: 'B' = B()) -> None: # E: Incompatible default for argument "x" (default has type "B", argument has type "A")
    pass
def h(x: 'A' = A(), y: 'B' = B()) -> None:
    pass
[out]

[case testMultipleDefaultArgumentExpressions2]
import typing
class A: pass
class B: pass

def g(x: 'A' = A(), y: 'B' = A()) -> None: # E: Incompatible default for argument "y" (default has type "A", argument has type "B")
    pass
[out]

[case testDefaultArgumentsAndSignatureAsComment]
import typing
def f(x = 1): # type: (int) -> str
    pass
f()
f(1)
f('') # E: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testMethodDefaultArgumentsAndSignatureAsComment]
import typing
class A:
    def f(self, x = 1): # type: (int) -> str
        pass
A().f()
A().f(1)
A().f('') # E: Argument 1 to "f" of "A" has incompatible type "str"; expected "int"


-- Access to method defined as a data attribute
-- --------------------------------------------


[case testMethodAsDataAttribute]
from typing import Any, Callable, ClassVar
class B: pass
x: Any
class A:
    f = x # type: ClassVar[Callable[[A], None]]
    g = x # type: ClassVar[Callable[[A, B], None]]
a: A
a.f()
a.g(B())
a.f(a) # E: Too many arguments
a.g()  # E: Too few arguments

[case testMethodWithInvalidMethodAsDataAttribute]
from typing import Any, Callable, ClassVar
class B: pass
x: Any
class A:
    f = x # type: ClassVar[Callable[[], None]]
    g = x # type: ClassVar[Callable[[B], None]]
a: A
a.f() # E: Attribute function "f" with type "Callable[[], None]" does not accept self argument
a.g() # E: Invalid self argument "A" to attribute function "g" with type "Callable[[B], None]"

[case testMethodWithDynamicallyTypedMethodAsDataAttribute]
from typing import Any, Callable, ClassVar
class B: pass
x: Any
class A:
    f = x # type: ClassVar[Callable[[Any], Any]]
a: A
a.f()
a.f(a) # E: Too many arguments

[case testMethodWithInferredMethodAsDataAttribute]
from typing import Any
def m(self: "A") -> int: ...

class A:
    n = m

a = A()
reveal_type(a.n())  # N: Revealed type is "builtins.int"
reveal_type(A.n(a))  # N: Revealed type is "builtins.int"
A.n()  # E: Too few arguments

[case testOverloadedMethodAsDataAttribute]
from foo import *
[file foo.pyi]
from typing import overload
class B: pass
class A:
    @overload
    def f(self) -> None: pass
    @overload
    def f(self, b: B) -> None: pass
    g = f
a: A
a.g()
a.g(B())
a.g(a) # E: No overload variant matches argument type "A" \
       # N: Possible overload variants: \
       # N:     def f(self) -> None \
       # N:     def f(self, b: B) -> None

[case testMethodAsDataAttributeInferredFromDynamicallyTypedMethod]

class A:
    def f(self, x): pass
    g = f
a: A
a.g(object())
a.g(a, a) # E: Too many arguments
a.g()     # E: Too few arguments

[case testMethodAsDataAttributeInGenericClass]
from typing import TypeVar, Generic
t = TypeVar('t')
class B: pass
class A(Generic[t]):
    def f(self, x: t) -> None: pass
    g = f
a: A[B]
a.g(B())
a.g(a)   # E: Argument 1 has incompatible type "A[B]"; expected "B"

[case testInvalidMethodAsDataAttributeInGenericClass]
from typing import Any, TypeVar, Generic, Callable, ClassVar
t = TypeVar('t')
class B: pass
class C: pass
x: Any
class A(Generic[t]):
    f = x # type: ClassVar[Callable[[A[B]], None]]
ab: A[B]
ac: A[C]
ab.f()
ac.f()   # E: Invalid self argument "A[C]" to attribute function "f" with type "Callable[[A[B]], None]"

[case testPartiallyTypedSelfInMethodDataAttribute]
from typing import Any, TypeVar, Generic, Callable, ClassVar
t = TypeVar('t')
class B: pass
class C: pass
x: Any
class A(Generic[t]):
    f = x # type: ClassVar[Callable[[A], None]]
ab: A[B]
ac: A[C]
ab.f()
ac.f()

[case testCallableDataAttribute]
from typing import Callable, ClassVar
class A:
    g: ClassVar[Callable[[A], None]]
    def __init__(self, f: Callable[[], None]) -> None:
        self.f = f
a = A(lambda: None)
a.f()
a.g()
a.f(a) # E: Too many arguments
a.g(a) # E: Too many arguments


-- Nested functions
-- ----------------


[case testSimpleNestedFunction]
import typing
def f(a: 'A') -> None:
    def g(b: 'B') -> None:
        if int():
            b = a \
            # E: Incompatible types in assignment (expression has type "A", variable has type "B")
            aa = a # type: A # ok
            b = B()
    g(a) # E: Argument 1 to "g" has incompatible type "A"; expected "B"
    g(B())
class A: pass
class B: pass

[case testReturnAndNestedFunction]
import typing
def f() -> 'A':
    def g() -> 'B':
        return A() # fail
        return B()
    return B() # fail
    return A()
class A: pass
class B: pass
[out]
main:4: error: Incompatible return value type (got "A", expected "B")
main:6: error: Incompatible return value type (got "B", expected "A")

[case testDynamicallyTypedNestedFunction]
import typing
def f(x: object) -> None:
    def g(y):
        pass
    g() # E: Missing positional argument "y" in call to "g"
    g(x)
[out]

[case testNestedFunctionInMethod]
import typing
class A:
    def f(self) -> None:
        def g(x: int) -> None:
            y = x # type: int
            a = x # type: A # fail
        g(2)
        g(A()) # fail
[out]
main:6: error: Incompatible types in assignment (expression has type "int", variable has type "A")
main:8: error: Argument 1 to "g" has incompatible type "A"; expected "int"

[case testNestedFunctionInMethodWithTooFewArgumentsInTypeComment]
class A:
    def f(self):
        # type: () -> None
        def g(x):  # E: Type signature has too few arguments
            # type: () -> None
            pass

[case testNestedFunctionInMethodCannotAccessEnclosingClassAttributes]
class A:
    var: int
    import mod
    class B: ...

    def method(self) -> None:
        def f1(arg: object) -> None:
            arg.var  # E: "object" has no attribute "var"
            arg.mod  # E: "object" has no attribute "mod"
            arg.B  # E: "object" has no attribute "B"
[file mod.py]

[case testDeepNestedFunctionWithTooFewArgumentsInTypeComment]
class A:
    def f(self):
        # type: () -> None
        class B:
            def g(self):
                # type: () -> None
                def h(x):  # E: Type signature has too few arguments
                    # type: () -> None
                    pass

[case testDeepNestedMethodInTypeComment]
class A:
    def f(self):
        # type: () -> None
        class B:
            class C:
                def g(self):
                    # type: () -> None
                    pass

[case testMutuallyRecursiveNestedFunctions]
def f() -> None:
    def g() -> None:
        h(1)
        h('') # E
    def h(x: int) -> None:
        g()
        g(1) # E
[out]
main:4: error: Argument 1 to "h" has incompatible type "str"; expected "int"
main:7: error: Too many arguments for "g"

[case testMutuallyRecursiveDecoratedFunctions]
from typing import Callable, Any
def dec(f) -> Callable[..., Any]: pass
def f() -> None:
    @dec
    def g() -> None:
        h()
        h.x # E
    @dec
    def h(x: int) -> None:
        g(1)
        g.x # E
[out]
main:7: error: "Callable[..., Any]" has no attribute "x"
main:11: error: "Callable[..., Any]" has no attribute "x"

[case testNestedGenericFunctions]
from typing import TypeVar
T = TypeVar('T')
U = TypeVar('U')

def outer(x: T) -> T:
    def inner(y: U) -> T: ...
    return inner(1)


-- Casts
-- -----


[case testCastsToAndFromFunctionTypes]
from typing import TypeVar, Callable, Any, cast
t = TypeVar('t')
def f(x: t,
      f1: Callable[[], None],
      f2: Callable[[Any], None], o: object) -> None:
    x = cast(t, f1)
    f1 = cast(Callable[[], None], x)
    f1 = cast(Callable[[], None], f2)
    f1 = cast(Callable[[], None], o)


-- Function decorators
-- -------------------


[case testTrivialStaticallyTypedFunctionDecorator]
from typing import TypeVar
t = TypeVar('t')
def dec(f: t) -> t:
    return f
@dec
def f(x: int) -> None: pass
f(1)
f('x') # E: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testTrivialStaticallyTypedMethodDecorator]
from typing import TypeVar
t = TypeVar('t')
def dec(f: t) -> t:
    return f
class A:
    @dec
    def f(self, x: int) -> None: pass
A().f(1)
A().f('') # E: Argument 1 to "f" of "A" has incompatible type "str"; expected "int"
class B: pass

[case testTrivialDecoratedNestedFunction]
from typing import TypeVar
t = TypeVar('t')
def dec(f: t) -> t:
    return f
def g() -> None:
    @dec
    def f(x: int) -> None: pass
    f(1)
    f('') # E: Argument 1 to "f" has incompatible type "str"; expected "int"
[out]

[case testCheckingDecoratedFunction]
import typing
def dec(f): pass
@dec
def f(x: 'A') -> None:
    a = x # type: A
    if int():
        x = object() # E: Incompatible types in assignment (expression has type "object", variable has type "A")
class A: pass
[out]

[case testDecoratorThatSwitchesType]
from typing import Callable
def dec(x) -> Callable[[], None]: pass
@dec
def f(y): pass
f()
f(None) # E: Too many arguments for "f"

[case testDecoratorThatSwitchesTypeWithMethod]
from typing import Any, Callable
def dec(x) -> Callable[[Any], None]: pass
class A:
    @dec
    def f(self, a, b, c): pass
a: A
a.f()
a.f(None) # E: Too many arguments for "f" of "A"

[case testNestedDecorators]
from typing import Any, Callable
def dec1(f: Callable[[Any], None]) -> Callable[[], None]: pass
def dec2(f: Callable[[Any, Any], None]) -> Callable[[Any], None]: pass
@dec1
@dec2
def f(x, y): pass
f()
f(None) # E: Too many arguments for "f"

[case testInvalidDecorator1]
from typing import Any, Callable
def dec1(f: Callable[[Any], None]) -> Callable[[], None]: pass
def dec2(f: Callable[[Any, Any], None]) -> Callable[[Any], None]: pass
@dec1
@dec2  # E: Argument 1 to "dec2" has incompatible type "Callable[[Any], Any]"; expected "Callable[[Any, Any], None]"
def f(x): pass

def faulty(c: Callable[[int], None]) -> Callable[[tuple[int, int]], None]:
    return lambda x: None

@faulty  # E: Argument 1 to "faulty" has incompatible type "Callable[[tuple[int, int]], None]"; expected "Callable[[int], None]"
@faulty  # E: Argument 1 to "faulty" has incompatible type "Callable[[str], None]"; expected "Callable[[int], None]"
def g(x: str) -> None:
    return None
[builtins fixtures/tuple.pyi]

[case testInvalidDecorator2]
from typing import Any, Callable
def dec1(f: Callable[[Any, Any], None]) -> Callable[[], None]: pass
def dec2(f: Callable[[Any, Any], None]) -> Callable[[Any], None]: pass
@dec1 # E: Argument 1 to "dec1" has incompatible type "Callable[[Any], None]"; expected "Callable[[Any, Any], None]"
@dec2
def f(x, y): pass

[case testNoTypeCheckDecoratorOnMethod1]
from typing import no_type_check

@no_type_check
def foo(x: 'bar', y: {'x': 4}) -> 42:
    1 + 'x'
[typing fixtures/typing-medium.pyi]

[case testNoTypeCheckDecoratorOnMethod2]
import typing

@typing.no_type_check
def foo(x: 's', y: {'x': 4}) -> 42:
    1 + 'x'

@typing.no_type_check
def bar() -> None:
    1 + 'x'
[typing fixtures/typing-medium.pyi]

[case testCallingNoTypeCheckFunction]
import typing

@typing.no_type_check
def foo(x: {1:2}) -> [1]:
    1 + 'x'

foo()
foo(1, 'b')
[typing fixtures/typing-medium.pyi]

[case testCallingNoTypeCheckFunction2]
import typing

def f() -> None:
    foo()

@typing.no_type_check
def foo(x: {1:2}) -> [1]:
    1 + 'x'
[typing fixtures/typing-medium.pyi]

[case testNoTypeCheckDecoratorSemanticError]
import typing

@typing.no_type_check
def foo(x: {1:2}) -> [1]:
    x = y
[typing fixtures/typing-medium.pyi]


-- Forward references to decorated functions
-- -----------------------------------------


[case testForwardReferenceToDynamicallyTypedDecorator]
def f(self) -> None:
    g()
    g(1)

def dec(f):
    return f

@dec
def g():
    pass

[case testForwardReferenceToDecoratorWithAnyReturn]
from typing import Any

def f(self) -> None:
    g()
    g(1)

def dec(f) -> Any:
    return f

@dec
def g():
    pass

[case testForwardReferenceToDecoratorWithIdentityMapping]
from typing import TypeVar

def f(self) -> None:
    g()
    g(1) # E: Too many arguments for "g"
    h(1).x # E: "str" has no attribute "x"
    h('') # E: Argument 1 to "h" has incompatible type "str"; expected "int"

T = TypeVar('T')
def dec(f: T) -> T:
    return f

@dec
def g(): pass
@dec
def h(x: int) -> str: pass
[out]

[case testForwardReferenceToDynamicallyTypedDecoratedMethod]
def f(self) -> None:
    A().f(1).y
    A().f()

class A:
    @dec
    def f(self, x): pass

def dec(f): return f
[builtins fixtures/staticmethod.pyi]

[case testForwardReferenceToStaticallyTypedDecoratedMethod]
from typing import TypeVar

def f(self) -> None:
    A().f(1).y # E: "str" has no attribute "y"
    A().f('') # E: Argument 1 to "f" of "A" has incompatible type "str"; expected "int"

class A:
    @dec
    def f(self, a: int) -> str: return ''

T = TypeVar('T')
def dec(f: T) -> T: return f
[builtins fixtures/staticmethod.pyi]
[out]

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

class A:
    @property
    def x(self): pass
[builtins fixtures/property.pyi]

[case testForwardReferenceToStaticallyTypedProperty]
def f(self) -> None:
    A().x.y # E: "int" has no attribute "y"

class A:
    @property
    def x(self) -> int: return 1
[builtins fixtures/property.pyi]
[out]

[case testForwardReferenceToDynamicallyTypedStaticMethod]
def f(self) -> None:
    A.x(1).y
    A.x() # E: Missing positional argument "x" in call to "x"

class A:
    @staticmethod
    def x(x): pass
[builtins fixtures/staticmethod.pyi]
[out]

[case testForwardReferenceToStaticallyTypedStaticMethod]
def f(self) -> None:
    A.x(1).y # E: "str" has no attribute "y"
    A.x('') # E: Argument 1 to "x" of "A" has incompatible type "str"; expected "int"

class A:
    @staticmethod
    def x(a: int) -> str: return ''
[builtins fixtures/staticmethod.pyi]
[out]

[case testForwardReferenceToDynamicallyTypedClassMethod]
def f(self) -> None:
    A.x(1).y
    A.x() # E: Missing positional argument "a" in call to "x"

class A:
    @classmethod
    def x(cls, a): pass
[builtins fixtures/classmethod.pyi]
[out]

[case testForwardReferenceToStaticallyTypedClassMethod]
def f(self) -> None:
    A.x(1).y # E: "str" has no attribute "y"
    A.x('') # E: Argument 1 to "x" of "A" has incompatible type "str"; expected "int"

class A:
    @classmethod
    def x(cls, x: int) -> str: return ''
[builtins fixtures/classmethod.pyi]
[out]

[case testForwardReferenceToDecoratedFunctionUsingMemberExpr]
import m

def f(self) -> None:
    g(1).x # E: "str" has no attribute "x"

@m.dec
def g(x: int) -> str: pass
[file m.py]
from typing import TypeVar
T = TypeVar('T')
def dec(f: T) -> T:
    return f
[out]

[case testForwardReferenceToFunctionWithMultipleDecorators]
# flags: --disable-error-code=used-before-def
def f(self) -> None:
    g()
    g(1)

def dec(f):
    return f

@dec
@dec2
def g():
    pass

def dec2(f):
    return f

[case testForwardReferenceToDynamicallyTypedDecoratedStaticMethod]
def f(self) -> None:
    A().f(1).y
    A().f()
    A().g(1).y
    A().g()

class A:
    @dec
    @staticmethod
    def f(self, x): pass
    @staticmethod
    @dec
    def g(self, x): pass

def dec(f): return f
[builtins fixtures/staticmethod.pyi]

[case testForwardRefereceToDecoratedFunctionWithCallExpressionDecorator]
# flags: --disable-error-code=used-before-def
def f(self) -> None:
    g()
    g(1)

@dec(1)
def g(): pass

def dec(f): pass


-- Decorator functions in import cycles
-- ------------------------------------


[case testDecoratorWithIdentityTypeInImportCycle]
import a

[file a.py]
import b
from d import dec
@dec
def f(x: int) -> None: pass
b.g(1)  # E: Argument 1 to "g" has incompatible type "int"; expected "str"

[file b.py]
import a
from d import dec
@dec
def g(x: str) -> None: pass
a.f('')  # E: Argument 1 to "f" has incompatible type "str"; expected "int"

[file d.py]
from typing import TypeVar
T = TypeVar('T')
def dec(f: T) -> T: return f

[case testDecoratorWithNoAnnotationInImportCycle]
import a

[file a.py]
import b
from d import dec
@dec
def f(x: int) -> None: pass
b.g(1, z=4)

[file b.py]
import a
from d import dec
@dec
def g(x: str) -> None: pass
a.f('', y=2)

[file d.py]
def dec(f): return f

[case testDecoratorWithFixedReturnTypeInImportCycle]
import a

[file a.py]
import b
from d import dec
@dec
def f(x: int) -> str: pass
b.g(1)()  # E: "str" not callable

[file b.py]
import a
from d import dec
@dec
def g(x: int) -> str: pass
a.f(1)()  # E: "str" not callable

[file d.py]
from typing import Callable
def dec(f: Callable[[int], str]) -> Callable[[int], str]: return f

[case testDecoratorWithCallAndFixedReturnTypeInImportCycle]
import a

[file a.py]
import b
from d import dec
@dec()
def f(x: int) -> str: pass
b.g(1)()  # E: "str" not callable

[file b.py]
import a
from d import dec
@dec()
def g(x: int) -> str: pass
a.f(1)()  # E: "str" not callable

[file d.py]
from typing import Callable
def dec() -> Callable[[Callable[[int], str]], Callable[[int], str]]: pass

[case testDecoratorWithCallAndFixedReturnTypeInImportCycleAndDecoratorArgs]
import a

[file a.py]
import b
from d import dec
@dec(1)  # E: Argument 1 to "dec" has incompatible type "int"; expected "str"
def f(x: int) -> str: pass
b.g(1)()  # E: "str" not callable

[file b.py]
import a
from d import dec
@dec(1)  # E: Argument 1 to "dec" has incompatible type "int"; expected "str"
def g(x: int) -> str: pass
a.f(1)()  # E: "str" not callable

[file d.py]
from typing import Callable
def dec(x: str) -> Callable[[Callable[[int], str]], Callable[[int], str]]: pass

[case testUndefinedDecoratorInImportCycle]
# cmd: mypy -m foo.base
[file foo/__init__.py]
import foo.base
class Derived(foo.base.Base):
    def method(self) -> None: pass
[file foo/base.py]
import foo
class Base:
    @decorator
    def method(self) -> None: pass
[out]
tmp/foo/base.py:3: error: Name "decorator" is not defined


-- Conditional function definition
-- -------------------------------


[case testTypeCheckBodyOfConditionalFunction]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None:
        if int():
            x = 1
            x = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[out]

[case testCallConditionalFunction]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None:  pass
    f(1)
    f('x') # E: Argument 1 to "f" has incompatible type "str"; expected "int"
f(1)
f('x') # E: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testConditionalFunctionDefinitionWithIfElse]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None:
        'x' + x   # fail
        if int():
            x = 1
else:
    def f(x: int) -> None:
        x + 'x'   # fail
        if int():
            x = 1
f(1)
f('x') # fail
[builtins fixtures/primitives.pyi]
[out]
main:5: error: Unsupported operand types for + ("str" and "int")
main:10: error: Unsupported operand types for + ("int" and "str")
main:14: error: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testNestedConditionalFunctionDefinitionWithIfElse]
from typing import Any
x = None # type: Any
def top() -> None:
    if x:
        def f(x: int) -> None:
            if int():
                x = 'x'  # E: Incompatible types in assignment \
                          (expression has type "str", variable has type "int")
                x = 1
    else:
        def f(x: int) -> None:
            x + 'x'   # E: Unsupported operand types for + ("int" and "str")
            x = 1
    f(1)
    f('x') # E: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testUnconditionalRedefinitionOfConditionalFunction]
from typing import Any
x = None # type: Any
if x:
    def f(): pass
def f(): pass # E: Name "f" already defined on line 4

[case testIncompatibleConditionalFunctionDefinition]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None: pass
else:
    def f(x): pass # E: All conditional function variants must have identical signatures \
                   # N: Original: \
                   # N:     def f(x: int) -> None \
                   # N: Redefinition: \
                   # N:     def f(x: Any) -> Any

[case testIncompatibleConditionalFunctionDefinition2]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None: pass
else:
    def f(y: int) -> None: pass # E: All conditional function variants must have identical signatures \
                                # N: Original: \
                                # N:     def f(x: int) -> None \
                                # N: Redefinition: \
                                # N:     def f(y: int) -> None

[case testIncompatibleConditionalFunctionDefinition3]
from typing import Any
x = None # type: Any
if x:
    def f(x: int) -> None: pass
else:
    def f(x: int = 0) -> None: pass # E: All conditional function variants must have identical signatures \
                                    # N: Original: \
                                    # N:     def f(x: int) -> None \
                                    # N: Redefinition: \
                                    # N:     def f(x: int = ...) -> None

[case testIncompatibleConditionalFunctionDefinition4]
from typing import Any, Union, TypeVar
T1 = TypeVar('T1')
T2 = TypeVar('T2', bound=Union[int, str])
x = None # type: Any
if x:
    def f(x: T1) -> T1: pass
else:
    def f(x: T2) -> T2: pass # E: All conditional function variants must have identical signatures \
                             # N: Original: \
                             # N:     def [T1] f(x: T1) -> T1 \
                             # N: Redefinition: \
                             # N:     def [T2: int | str] f(x: T2) -> T2

[case testConditionalFunctionDefinitionUsingDecorator1]
from typing import Callable

def dec(f) -> Callable[[int], None]: pass

x = int()
if x:
    @dec
    def f(): pass
else:
    def f(x: int) -> None: pass

[case testConditionalFunctionDefinitionUsingDecorator2]
from typing import Callable

def dec(f) -> Callable[[int], None]: pass

x = int()
if x:
    @dec
    def f(): pass
else:
    def f(x: str) -> None: pass # E: Incompatible redefinition (redefinition with type "Callable[[str], None]", original type "Callable[[int], None]")

[case testConditionalFunctionDefinitionUsingDecorator3]

from typing import Callable

def dec(f) -> Callable[[int], None]: pass

x = int()
if x:
    def f(x: int, /) -> None: pass
else:
    @dec
    def f(): pass

[case testConditionalFunctionDefinitionUsingDecorator4]

from typing import Callable

def dec(f) -> Callable[[int], None]: pass

x = int()
if x:
    def f(x: str) -> None: pass
else:
    @dec
    def f(): pass   # E: All conditional function variants must have identical signatures \
                    # N: Original: \
                    # N:     def f(x: str) -> None \
                    # N: Redefinition: \
                    # N:     def f(int, /) -> None

[case testConditionalFunctionDefinitionUnreachable]
def bar() -> None:
    if False:
        foo = 1
    else:
        def foo(obj): ...

def baz() -> None:
    if False:
        foo: int = 1
    else:
        def foo(obj): ...  # E: Incompatible redefinition (redefinition with type "Callable[[Any], Any]", original type "int")
[builtins fixtures/tuple.pyi]

[case testConditionalRedefinitionOfAnUnconditionalFunctionDefinition1]
from typing import Any
def f(x: str) -> None: pass
x = None # type: Any
if x:
    def f(x: int) -> None: pass # E: All conditional function variants must have identical signatures \
                                # N: Original: \
                                # N:     def f(x: str) -> None \
                                # N: Redefinition: \
                                # N:     def f(x: int) -> None

[case testConditionalRedefinitionOfAnUnconditionalFunctionDefinition2]
from typing import Any
def f(x: int) -> None: pass # N: "f" defined here
x = None # type: Any
if x:
    def f(y: int) -> None: pass # E: All conditional function variants must have identical signatures \
                                # N: Original: \
                                # N:     def f(x: int) -> None \
                                # N: Redefinition: \
                                # N:     def f(y: int) -> None
f(x=1) # The first definition takes precedence.
f(y=1) # E: Unexpected keyword argument "y" for "f"

[case testRedefineFunctionDefinedAsVariable]
def g(): pass
f = g
if g():
    def f(): pass
f()
f(1) # E: Too many arguments

[case testRedefineFunctionDefinedAsVariableInitializedToNone]
def g(): pass
f = None
if g():
    def f(): pass
f()
f(1) # E: Too many arguments for "f"

[case testRedefineNestedFunctionDefinedAsVariableInitializedToNone]
def g() -> None:
    f = None
    if object():
        def f(x: int) -> None: pass
    f() # E: Missing positional argument "x" in call to "f"
    f(1)
    f('') # E: Argument 1 to "f" has incompatible type "str"; expected "int"
[out]

[case testRedefineFunctionDefinedAsVariableWithInvalidSignature]
def g(): pass
f = g
if g():
    def f(x): pass  # E: Incompatible redefinition (redefinition with type "Callable[[Any], Any]", original type "Callable[[], Any]")

[case testRedefineFunctionDefinedAsVariableWithVariance1]
class B: pass
class C(B): pass
def g(x: C) -> B: pass
f = g
if g(C()):
    def f(x: C) -> C: pass

[case testRedefineFunctionDefinedAsVariableWithVariance2]
class B: pass
class C(B): pass
def g(x: C) -> B: pass
f = g
if g(C()):
    def f(x: B) -> B: pass

[case testRedefineFunctionDefinedAsVariableInitializedToEmptyList]
f = [] # E: Need type annotation for "f" (hint: "f: list[<type>] = ...")
if object():
    def f(): pass # E: Incompatible redefinition
f()  # E: "list[Any]" not callable
f(1)  # E: "list[Any]" not callable
[builtins fixtures/list.pyi]

[case testDefineConditionallyAsImportedAndDecorated]
from typing import Callable

def dec(f: Callable[[], None]) -> Callable[[], None]: ...

if int():
    from m import f
else:
    @dec
    def f():
        yield
[file m.py]
def f() -> None: pass

[case testDefineConditionallyAsImportedAndDecoratedWithInference]
if int():
    from m import f
else:
    from contextlib import contextmanager

    @contextmanager
    def f():
        yield
[file m.py]
from contextlib import contextmanager

@contextmanager
def f():
    yield
[typing fixtures/typing-medium.pyi]
[builtins fixtures/tuple.pyi]


-- Conditional method definition
-- -----------------------------


[case testTypeCheckBodyOfConditionalMethod]
from typing import Any
x = None # type: Any
class A:
    if x:
        def f(self, x: int) -> None:
            if int():
                x = 1
                x = '' # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[out]

[case testCallConditionalMethodInClassBody]
from typing import Any
x = None # type: Any
class A:
    if x:
        def f(self, x: int) -> None:  pass
        f(x, 1)
        f(x, 'x') # E: Argument 2 to "f" of "A" has incompatible type "str"; expected "int"
    f(x, 1)
    f(x, 'x') # E: Argument 2 to "f" of "A" has incompatible type "str"; expected "int"
[out]

[case testCallConditionalMethodViaInstance]
from typing import Any
x = None # type: Any
class A:
    if x:
         def f(self, x: int) -> None: pass
A().f(1)
A().f('x') # E: Argument 1 to "f" of "A" has incompatible type "str"; expected "int"

[case testConditionalMethodDefinitionWithIfElse]
from typing import Any
x = None # type: Any
class A:
    if x:
        def f(self, x: int) -> None:
            'x' + x   # fail
            if int():
                x = 1
    else:
        def f(self, x: int) -> None:
            x + 'x'   # fail
            if int():
                x = 1
A().f(1)
A().f('x') # fail
[builtins fixtures/primitives.pyi]
[out]
main:6: error: Unsupported operand types for + ("str" and "int")
main:11: error: Unsupported operand types for + ("int" and "str")
main:15: error: Argument 1 to "f" of "A" has incompatible type "str"; expected "int"

[case testUnconditionalRedefinitionOfConditionalMethod]
from typing import Any
x = None # type: Any
class A:
    if x:
        def f(self): pass
    def f(self): pass # E: Name "f" already defined on line 5

[case testIncompatibleConditionalMethodDefinition]
from typing import Any
x = None # type: Any
class A:
    if x:
        def f(self, x: int) -> None: pass
    else:
        def f(self, x): pass # E: All conditional function variants must have identical signatures \
                             # N: Original: \
                             # N:     def f(self: A, x: int) -> None \
                             # N: Redefinition: \
                             # N:     def f(self: A, x: Any) -> Any
[out]

[case testConditionalFunctionDefinitionInTry]
import typing
try:
    def f(x: int) -> None: pass
except:
    def g(x: str) -> None: pass
f(1)
f('x') # E: Argument 1 to "f" has incompatible type "str"; expected "int"
g('x')
g(1) # E: Argument 1 to "g" has incompatible type "int"; expected "str"

[case testConditionalMethodDefinitionUsingDecorator]
from typing import Callable

def dec(f) -> Callable[['A', int], None]: pass

class A:
    x = int()
    if x:
        @dec
        def f(self): pass
    else:
        def f(self, x: int) -> None: pass


-- Callable with specific arg list
-- -------------------------------


[case testCallableWithNamedArg]
from typing import Callable
from mypy_extensions import Arg

def a(f: Callable[[Arg(int, 'x')], int]):
    f(x=4)
    f(5)
    f(y=3) # E: Unexpected keyword argument "y"

[builtins fixtures/dict.pyi]

[case testCallableWithOptionalArg]
from typing import Callable
from mypy_extensions import DefaultArg

def a(f: Callable[[DefaultArg(int, 'x')], int]):
    f(x=4)
    f(2)
    f()
    f(y=3) # E: Unexpected keyword argument "y"
    f("foo") # E: Argument 1 has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testCallableWithNamedArgFromExpr]
from typing import Callable
from mypy_extensions import Arg

F = Callable[[Arg(int, 'x')], int]

def a(f: F):
    f(x=4)
    f(5)
    f(y=3) # E: Unexpected keyword argument "y"

[builtins fixtures/dict.pyi]

[case testCallableWithOptionalArgFromExpr]
from typing import Callable
from mypy_extensions import DefaultArg

F = Callable[[DefaultArg(int, 'x')], int]
def a(f: F):
    f(x=4)
    f(2)
    f()
    f(y=3) # E: Unexpected keyword argument "y"
    f("foo") # E: Argument 1 has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testCallableParsingInInheritance]

from collections import namedtuple
class C(namedtuple('t', 'x')):
    pass
[builtins fixtures/tuple.pyi]

[case testCallableParsingSameName]
from typing import Callable

def Arg(x, y): pass

F = Callable[[Arg(int, 'x')], int]  # E: Invalid argument constructor "__main__.Arg"

[case testCallableParsingFromExpr]
from typing import Callable, List
from mypy_extensions import Arg, VarArg, KwArg
import mypy_extensions
import types  # Needed for type checking

def WrongArg(x, y): return y
# Note that for this test, the 'Value of type "int" is not indexable' errors are silly,
# and a consequence of Callable being set to an int in the test stub.  We can't set it to
# something else sensible, because other tests require the stub not have anything
# that looks like a function call.
F = Callable[[WrongArg(int, 'x')], int] # E: Invalid argument constructor "__main__.WrongArg"
G = Callable[[Arg(1, 'x')], int] # E: Invalid type: try using Literal[1] instead?
H = Callable[[VarArg(int, 'x')], int] # E: VarArg arguments should not have names
I = Callable[[VarArg(int)], int] # ok
J = Callable[[VarArg(), KwArg()], int] # ok
K = Callable[[VarArg(), int], int] # E: Required positional args may not appear after default, named or var args
L = Callable[[Arg(name='x', type=int)], int] # ok
# I have commented out the following test because I don't know how to expect the "defined here" note part of the error.
# M = Callable[[Arg(gnome='x', type=int)], int]   E: Invalid type alias: expression is not a valid type   E: Unexpected keyword argument "gnome" for "Arg"
N = Callable[[Arg(name=None, type=int)], int] # ok
O = Callable[[List[Arg(int)]], int]  # E: Invalid type alias: expression is not a valid type \
                                     # E: Value of type "int" is not indexable \
                                     # E: Type expected within [...]
P = Callable[[mypy_extensions.VarArg(int)], int] # ok
Q = Callable[[Arg(int, type=int)], int]  # E: Invalid type alias: expression is not a valid type \
                                         # E: Value of type "int" is not indexable \
                                         # E: "Arg" gets multiple values for keyword argument "type"
R = Callable[[Arg(int, 'x', name='y')], int]  # E: Invalid type alias: expression is not a valid type \
                                              # E: Value of type "int" is not indexable \
                                              # E: "Arg" gets multiple values for keyword argument "name"
[builtins fixtures/dict.pyi]

[case testCallableParsing]
from typing import Callable
from mypy_extensions import Arg, VarArg, KwArg

def WrongArg(x, y): return y

def b(f: Callable[[Arg(1, 'x')], int]): pass # Invalid type. Try using Literal[1] instead?
def d(f: Callable[[VarArg(int)], int]): pass # ok
def e(f: Callable[[VarArg(), KwArg()], int]): pass # ok
def g(f: Callable[[Arg(name='x', type=int)], int]): pass # ok
def h(f: Callable[[Arg(gnome='x', type=int)], int]): pass  # E: Unexpected argument "gnome" for argument constructor
def i(f: Callable[[Arg(name=None, type=int)], int]): pass # ok
def j(f: Callable[[Arg(int, 'x', name='y')], int]): pass # E: "Arg" gets multiple values for keyword argument "name"
def k(f: Callable[[Arg(int, type=int)], int]): pass # E: "Arg" gets multiple values for keyword argument "type"

[builtins fixtures/dict.pyi]

[case testCallableTypeAnalysis]
from typing import Callable
from mypy_extensions import Arg, VarArg as VARG, KwArg
import mypy_extensions as ext

def WrongArg(x, y): return y
def a(f: Callable[[WrongArg(int, 'x')], int]): pass # E: Invalid argument constructor "__main__.WrongArg"
def b(f: Callable[[BadArg(int, 'x')], int]): pass # E: Name "BadArg" is not defined
def d(f: Callable[[ext.VarArg(int)], int]): pass # ok
def e(f: Callable[[VARG(), ext.KwArg()], int]): pass # ok
def g(f: Callable[[ext.Arg(name='x', type=int)], int]): pass # ok
def i(f: Callable[[Arg(name=None, type=int)], int]): pass # ok

def f1(*args) -> int: pass
def f2(*args, **kwargs) -> int: pass

d(f1)
e(f2)
d(f2)
e(f1)

[builtins fixtures/dict.pyi]

[case testCallableWrongTypeType]
from typing import Callable
from mypy_extensions import Arg
def b(f: Callable[[Arg(1, 'x')], int]): pass # E: Invalid type: try using Literal[1] instead?
[builtins fixtures/dict.pyi]

[case testCallableTooManyVarArg]
from typing import Callable
from mypy_extensions import VarArg
def c(f: Callable[[VarArg(int, 'x')], int]): pass # E: VarArg arguments should not have names
[builtins fixtures/dict.pyi]

[case testCallableFastParseGood]
from typing import Callable
from mypy_extensions import VarArg, Arg, KwArg
def d(f: Callable[[VarArg(int)], int]): pass # ok
def e(f: Callable[[VarArg(), KwArg()], int]): pass # ok
def g(f: Callable[[Arg(name='x', type=int)], int]): pass # ok
def i(f: Callable[[Arg(name=None, type=int)], int]): pass # ok
[builtins fixtures/dict.pyi]

[case testCallableFastParseBadArgArgName]
from typing import Callable
from mypy_extensions import Arg
def h(f: Callable[[Arg(gnome='x', type=int)], int]): pass # E: Unexpected argument "gnome" for argument constructor
[builtins fixtures/dict.pyi]

[case testCallableKindsOrdering]
from typing import Callable, Any
from mypy_extensions import Arg, VarArg, KwArg, DefaultArg, NamedArg

def f(f: Callable[[VarArg(), int], int]): pass # E: Required positional args may not appear after default, named or var args
def g(f: Callable[[VarArg(), VarArg()], int]): pass # E: Var args may not appear after named or var args
def h(f: Callable[[KwArg(), KwArg()], int]): pass # E: You may only have one **kwargs argument
def i(f: Callable[[DefaultArg(), int], int]): pass # E: Required positional args may not appear after default, named or var args
def j(f: Callable[[NamedArg(Any, 'x'), DefaultArg(int, 'y')], int]): pass # E: Positional default args may not appear after named or var args
def k(f: Callable[[KwArg(), NamedArg(Any, 'x')], int]): pass # E: A **kwargs argument must be the last argument
[builtins fixtures/dict.pyi]

[case testCallableDuplicateNames]
from typing import Callable
from mypy_extensions import Arg, VarArg, KwArg, DefaultArg

def f(f: Callable[[Arg(int, 'x'), int, Arg(int, 'x')], int]): pass # E: Duplicate argument "x" in Callable

[builtins fixtures/dict.pyi]


[case testCallableWithKeywordOnlyArg]
from typing import Callable
from mypy_extensions import NamedArg

def a(f: Callable[[NamedArg(int, 'x')], int]):
    f(x=4)
    f(2) # E: Too many positional arguments
    f() # E: Missing named argument "x"
    f(y=3) # E: Unexpected keyword argument "y"
    f(x="foo") # E: Argument "x" has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testCallableWithKeywordOnlyOptionalArg]
from typing import Callable
from mypy_extensions import DefaultNamedArg

def a(f: Callable[[DefaultNamedArg(int, 'x')], int]):
    f(x=4)
    f(2) # E: Too many positional arguments
    f()
    f(y=3) # E: Unexpected keyword argument "y"
    f(x="foo") # E: Argument "x" has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testCallableWithKwargs]
from typing import Callable
from mypy_extensions import KwArg

def a(f: Callable[[KwArg(int)], int]):
    f(x=4)
    f(2) # E: Too many arguments
    f()
    f(y=3)
    f(x=4, y=3, z=10)
    f(x="foo") # E: Argument "x" has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]


[case testCallableWithVarArg]
from typing import Callable
from mypy_extensions import VarArg

def a(f: Callable[[VarArg(int)], int]):
    f(x=4)  # E: Unexpected keyword argument "x"
    f(2)
    f()
    f(3, 4, 5)
    f("a")  # E: Argument 1 has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testCallableArgKindSubtyping]
from typing import Callable
from mypy_extensions import Arg, DefaultArg

int_str_fun: Callable[[int, str], str]
int_opt_str_fun: Callable[[int, DefaultArg(str, None)], str]
int_named_str_fun: Callable[[int, Arg(str, 's')], str]

def isf(ii: int, ss: str) -> str:
    return ss

def iosf(i: int, s: str = "bar") -> str:
    return s

def isf_unnamed(__i: int, __s: str) -> str:
    return __s

int_str_fun = isf
int_str_fun = isf_unnamed
int_named_str_fun = isf_unnamed # E: Incompatible types in assignment (expression has type "Callable[[int, str], str]", variable has type "def (int, /, s: str) -> str")
int_opt_str_fun = iosf
int_str_fun = iosf
int_opt_str_fun = isf # E: Incompatible types in assignment (expression has type "def isf(ii: int, ss: str) -> str", variable has type "def (int, str = ..., /) -> str")

int_named_str_fun = isf # E: Incompatible types in assignment (expression has type "def isf(ii: int, ss: str) -> str", variable has type "def (int, /, s: str) -> str")
int_named_str_fun = iosf

[builtins fixtures/dict.pyi]

-- Callable[..., T]
-- ----------------


[case testCallableWithArbitraryArgs]
from typing import Callable
def f(x: Callable[..., int]) -> None:
    x()
    x(1)
    x(z=1)
    x() + '' # E: Unsupported operand types for + ("int" and "str")
[out]

[case testCallableWithArbitraryArgs2]
from typing import Callable
def f(x: Callable[..., int]) -> None:
    x(*[1], **{'x': 2})
[builtins fixtures/dict.pyi]

[case testCastWithCallableAndArbitraryArgs]
from typing import Callable, cast
f = cast(Callable[..., int], None)
f(x=4) + '' # E: Unsupported operand types for + ("int" and "str")

[case testCallableWithArbitraryArgsInErrorMessage]
from typing import Callable
def f(x: Callable[..., int]) -> None:
    if int():
        x = 1  # E: Incompatible types in assignment (expression has type "int", variable has type "Callable[..., int]")
[out]

[case testCallableWithArbitraryArgsInGenericFunction]
from typing import Callable, TypeVar
T = TypeVar('T')
def f(x: Callable[..., T]) -> T: pass
def g(*x: int) -> str: pass
x = f(g)
x + 1 # E: Unsupported left operand type for + ("str")
[builtins fixtures/list.pyi]

[case testCallableWithArbitraryArgsSubtyping]
from typing import Callable
def f(x: Callable[..., int]) -> None: pass
def g1(): pass
def g2(x, y) -> int: pass
def g3(*, y: str) -> int: pass
def g4(*, y: int) -> str: pass
f(g1)
f(g2)
f(g3)
f(g4) # E: Argument 1 to "f" has incompatible type "def g4(*, y: int) -> str"; expected "Callable[..., int]"

[case testCallableWithArbitraryArgsSubtypingWithGenericFunc]
from typing import Callable, TypeVar
T = TypeVar('T')
def f(x: Callable[..., int]) -> None: pass
def g1(x: T) -> int: pass
def g2(*x: T) -> int: pass
def g3(*x: T) -> T: pass
f(g1)
f(g2)
f(g3)
[builtins fixtures/tuple.pyi]

-- (...) -> T
-- ----------------

[case testEllipsisWithArbitraryArgsOnBareFunction]
def f(x, y, z): # type: (...) -> None
    pass
f(1, "hello", [])
f(x=1, y="hello", z=[])
[builtins fixtures/dict.pyi]

[case testEllipsisWithArbitraryArgsOnBareFunctionWithDefaults]
def f(x, y=1, z="hey"): # type: (...) -> None
    pass
f(1, "hello", [])
f(x=1, y="hello", z=[])
[builtins fixtures/dict.pyi]

[case testEllipsisWithArbitraryArgsOnBareFunctionWithKwargs]
from typing import Dict
def f(x, **kwargs): # type: (...) -> None
    success_dict_type = kwargs # type: Dict[str, str]
    failure_dict_type = kwargs # type: Dict[int, str] # E: Incompatible types in assignment (expression has type "dict[str, Any]", variable has type "dict[int, str]")
f(1, thing_in_kwargs=["hey"])
[builtins fixtures/dict.pyi]
[out]

[case testEllipsisWithArbitraryArgsOnBareFunctionWithVarargs]
from typing import Tuple, Any
def f(x, *args): # type: (...) -> None
    success_tuple_type = args # type: Tuple[Any, ...]
    fail_tuple_type = args # type: None # E: Incompatible types in assignment (expression has type "tuple[Any, ...]", variable has type "None")
f(1, "hello")
[builtins fixtures/tuple.pyi]
[out]

[case testEllipsisWithArbitraryArgsOnInstanceMethod]
class A:
    def f(self, x, y, z): # type: (...) -> None
        pass

[case testEllipsisWithArbitraryArgsOnClassMethod]
class A:
    @classmethod
    def f(cls, x, y, z): # type: (...) -> None
        pass
[builtins fixtures/classmethod.pyi]

[case testEllipsisWithArbitraryArgsOnStaticMethod]
class A:
    @staticmethod
    def f(x, y, z): # type: (...) -> None
        pass
[builtins fixtures/staticmethod.pyi]

[case testEllipsisWithSomethingAfterItFails]
def f(x, y, z): # type: (..., int) -> None
    pass
[out]
main:1: error: Ellipses cannot accompany other argument types in function type signature

[case testEllipsisWithSomethingBeforeItFails]
def f(x, y, z): # type: (int, ...) -> None
    pass
[out]
main:1: error: Ellipses cannot accompany other argument types in function type signature

[case testRejectCovariantArgument]
from typing import TypeVar, Generic

t = TypeVar('t', covariant=True)
class A(Generic[t]):
    def foo(self, x: t) -> None:
        return None
[builtins fixtures/bool.pyi]
[out]
main:5: error: Cannot use a covariant type variable as a parameter

[case testRejectCovariantArgumentSplitLine]
from typing import TypeVar, Generic

t = TypeVar('t', covariant=True)
class A(Generic[t]):
    def foo(self,
            x: t) -> None:
        return None
[builtins fixtures/bool.pyi]
[out]
main:6: error: Cannot use a covariant type variable as a parameter

[case testRejectCovariantArgumentInLambda]
from typing import TypeVar, Generic, Callable

t = TypeVar('t', covariant=True)
class Thing(Generic[t]):
    def chain(self, func: Callable[[t], None]) -> None: pass
    def end(self) -> None:
        return self.chain(  # Note that lambda args have no line numbers
            lambda _: None)
[builtins fixtures/bool.pyi]
[out]
main:8: error: Cannot use a covariant type variable as a parameter

[case testRejectCovariantArgumentInLambdaSplitLine]
from typing import TypeVar, Generic, Callable

[case testRejectContravariantReturnType]
# flags: --no-strict-optional
from typing import TypeVar, Generic

t = TypeVar('t', contravariant=True)
class A(Generic[t]):
    def foo(self) -> t:
        return None
[builtins fixtures/bool.pyi]
[out]
main:6: error: Cannot use a contravariant type variable as return type

[case testAcceptCovariantReturnType]
# flags: --no-strict-optional
from typing import TypeVar, Generic

t = TypeVar('t', covariant=True)
class A(Generic[t]):
    def foo(self) -> t:
        return None
[builtins fixtures/bool.pyi]

[case testAcceptContravariantArgument]
from typing import TypeVar, Generic

t = TypeVar('t', contravariant=True)
class A(Generic[t]):
    def foo(self, x: t) -> None:
        return None
[builtins fixtures/bool.pyi]


-- Redefining functions
-- --------------------


[case testRedefineFunction]
from typing import Any
def f(x) -> Any: pass
def g(x, y): pass
def h(x): pass
def j(y) -> Any: pass
f = h
f = j # E: Incompatible types in assignment (expression has type "def j(y: Any) -> Any", variable has type "def f(x: Any) -> Any")
f = g # E: Incompatible types in assignment (expression has type "Callable[[Any, Any], Any]", variable has type "Callable[[Any], Any]")

[case testRedefineFunction2]
def f() -> None: pass
def f() -> None: pass # E: Name "f" already defined on line 1


-- Special cases
-- -------------


[case testFunctionDefinitionWithForStatement]
for _ in [1]:
    def f(): pass
else:
    def g(): pass
f()
g()
[builtins fixtures/list.pyi]

[case testFunctionDefinitionWithWhileStatement]
while bool():
    def f(): pass
else:
    def g(): pass
f()
g()
[builtins fixtures/bool.pyi]

[case testBareCallable]
from typing import Callable, Any

def foo(f: Callable) -> bool:
    return f()

def f1() -> bool:
    return False

foo(f1)
[builtins fixtures/bool.pyi]

[case testFunctionNestedWithinWith]
from typing import Any
a = 1  # type: Any
with a:
    def f() -> None:
        pass
    f(1) # E: Too many arguments for "f"


[case testNameForDecoratorMethod]
from typing import Callable

class A:
    def f(self) -> None:
        # In particular, test that the error message contains "g" of "A".
        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], None]) -> Callable[[A, int], None]: pass
[out]

[case testUnknownFunctionNotCallable]
from typing import TypeVar

def f() -> None:
    pass
def g(x: int) -> None:
    pass
h = f if bool() else g
reveal_type(h) # N: Revealed type is "(def ()) | (def (x: builtins.int))"
h(7) # E: Too many arguments for "f"

T = TypeVar("T")
def join(x: T, y: T) -> T: ...

h2 = join(f, g)
reveal_type(h2)  # N: Revealed type is "builtins.function"
h2(7)  # E: Cannot call function of unknown type

h3 = join(g, f)
reveal_type(h3)  # N: Revealed type is "builtins.function"
h3(7)  # E: Cannot call function of unknown type
[builtins fixtures/bool.pyi]

[case testFunctionWithNameUnderscore]
def _(x: int) -> None: pass

_(1)
_('x')  # E: Argument 1 to "_" has incompatible type "str"; expected "int"

-- Positional-only arguments
-- -------------------------

[case testPositionalOnlyArg]
def f(__a: int) -> None: pass
def g(__a__: int) -> None: pass

f(1)
f(__a=1) # E: Unexpected keyword argument "__a" for "f"

g(1)
# Argument names that also end with __ are not positional-only.
g(__a__=1)

[builtins fixtures/bool.pyi]
[out]
main:1: note: "f" defined here

[case testMagicMethodPositionalOnlyArg]
class A(object):
    def __eq__(self, other) -> bool: return True # We are all equal.  # N: "__eq__" of "A" defined here

a = A()
a.__eq__(a)
a.__eq__(other=a) # E: Unexpected keyword argument "other" for "__eq__" of "A"

[builtins fixtures/bool.pyi]

[case testMagicMethodPositionalOnlyArgFastparse]


class A(object):
    def __eq__(self, other) -> bool: return True # We are all equal.  # N: "__eq__" of "A" defined here

a = A()
a.__eq__(a)
a.__eq__(other=a) # E: Unexpected keyword argument "other" for "__eq__" of "A"

[builtins fixtures/bool.pyi]

-- Type variable shenanigans
-- -------------------------

[case testGenericFunctionTypeDecl]
from typing import Callable, TypeVar

T = TypeVar('T')

f: Callable[[T], T]
reveal_type(f)  # N: Revealed type is "def [T] (T`-1) -> T`-1"
def g(__x: T) -> T: pass
f = g
reveal_type(f)  # N: Revealed type is "def [T] (T`-1) -> T`-1"
i = f(3)
reveal_type(i)  # N: Revealed type is "builtins.int"

[case testFunctionReturningGenericFunction]
from typing import Callable, TypeVar

T = TypeVar('T')
def deco() -> Callable[[T], T]: pass
reveal_type(deco)  # N: Revealed type is "def () -> def [T] (T`-1) -> T`-1"
f = deco()
reveal_type(f)  # N: Revealed type is "def [T] (T`1) -> T`1"
i = f(3)
reveal_type(i)  # N: Revealed type is "builtins.int"

[case testFunctionReturningGenericFunctionPartialBinding]
from typing import Callable, TypeVar

T = TypeVar('T')
U = TypeVar('U')

def deco(x: U) -> Callable[[T, U], T]: pass
reveal_type(deco)  # N: Revealed type is "def [U] (x: U`-1) -> def [T] (T`-2, U`-1) -> T`-2"
f = deco("foo")
reveal_type(f)  # N: Revealed type is "def [T] (T`1, builtins.str) -> T`1"
i = f(3, "eggs")
reveal_type(i)  # N: Revealed type is "builtins.int"

[case testFunctionReturningGenericFunctionTwoLevelBinding]
from typing import Callable, TypeVar

T = TypeVar('T')
R = TypeVar('R')
def deco() -> Callable[[T], Callable[[T, R], R]]: pass
f = deco()
reveal_type(f)  # N: Revealed type is "def [T] (T`2) -> def [R] (T`2, R`1) -> R`1"
g = f(3)
reveal_type(g)  # N: Revealed type is "def [R] (builtins.int, R`3) -> R`3"
s = g(4, "foo")
reveal_type(s)  # N: Revealed type is "builtins.str"

[case testGenericFunctionReturnAsDecorator]
from typing import Callable, TypeVar

T = TypeVar('T')
def deco(__i: int) -> Callable[[T], T]: pass

@deco(3)
def lol(x: int) -> str: ...

reveal_type(lol)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
s = lol(4)
reveal_type(s)  # N: Revealed type is "builtins.str"

[case testGenericFunctionOnReturnTypeOnly]
from typing import TypeVar, List

T = TypeVar('T')

def make_list() -> List[T]: pass

l: List[int] = make_list()

bad = make_list()  # E: Need type annotation for "bad" (hint: "bad: list[<type>] = ...")
[builtins fixtures/list.pyi]

[case testAnonymousArgumentError]
def foo(__b: int, x: int, y: int) -> int: pass
foo(x=2, y=2)  # E: Too few arguments for "foo"
foo(y=2)  # E: Too few arguments for "foo"

[case testMissingArgumentError]
def f(a, b, c, d=None) -> None: pass
f(1, 2, d=3) # E: Missing positional argument "c" in call to "f"

[case testMissingArgumentErrorMoreThanOneOptional]
def f(a: int, b=None, c=None) -> None: pass
f(b=4) # E: Missing positional argument "a" in call to "f"

[case testMissingArgumentsError]
def f(a, b, c, d=None) -> None: pass
f(1, d=3) # E: Missing positional arguments "b", "c" in call to "f"

[case testReturnTypeLineNumberWithDecorator]
def dec(f): pass

@dec
def test(a: str) -> (str,): # E: Syntax error in type annotation # N: Suggestion: Is there a spurious trailing comma?
    return None

[case testReturnTypeLineNumberNewLine]
def fn(a: str
       ) -> badtype: # E: Name "badtype" is not defined
    pass

[case testArgumentTypeLineNumberWithDecorator]
def dec(f): pass

@dec
def some_method(self: badtype): pass # E: Name "badtype" is not defined

[case TestArgumentTypeLineNumberNewline]
def fn(
        a: badtype) -> None: # E: Name "badtype" is not defined
    pass

[case testInferredTypeSubTypeOfReturnType]
from typing import Union, Dict, List
def f() -> List[Union[str, int]]:
    x = ['a']
    return x # E: Incompatible return value type (got "list[str]", expected "list[str | int]") \
      # N: "list" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance \
      # N: Consider using "Sequence" instead, which is covariant \
      # N: Perhaps you need a type annotation for "x"? Suggestion: "list[str | int]"

def g() -> Dict[str, Union[str, int]]:
    x = {'a': 'a'}
    return x # E: Incompatible return value type (got "dict[str, str]", expected "dict[str, str | int]") \
      # N: "dict" is invariant -- see https://mypy.readthedocs.io/en/stable/common_issues.html#variance \
      # N: Consider using "Mapping" instead, which is covariant in the value type \
      # N: Perhaps you need a type annotation for "x"? Suggestion: "dict[str, str | int]"

def h() -> Dict[Union[str, int], str]:
    x = {'a': 'a'}
    return x # E: Incompatible return value type (got "dict[str, str]", expected "dict[str | int, str]") \
# N: Perhaps you need a type annotation for "x"? Suggestion: "dict[str | int, str]"

def i() -> List[Union[int, float]]:
    x: List[int] = [1]
    return x # E: Incompatible return value type (got "list[int]", expected "list[int | float]") \
      # 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/dict.pyi]

[case testInferredTypeNotSubTypeOfReturnType]
from typing import Union, List
def f() -> List[Union[int, float]]:
    x = ['a']
    return x # E: Incompatible return value type (got "list[str]", expected "list[int | float]")

def g() -> List[Union[str, int]]:
    x = ('a', 2)
    return x # E: Incompatible return value type (got "tuple[str, int]", expected "list[str | int]")

[builtins fixtures/list.pyi]

[case testInferredTypeIsObjectMismatch]
from typing import Union, Dict, List
def f() -> Dict[str, Union[str, int]]:
    x = {'a': 'a', 'b': 2}
    return x # E: Incompatible return value type (got "dict[str, object]", expected "dict[str, str | int]")

def g() -> Dict[str, Union[str, int]]:
    x: Dict[str, Union[str, int]] = {'a': 'a', 'b': 2}
    return x

def h() -> List[Union[str, int]]:
    x = ['a', 2]
    return x # E: Incompatible return value type (got "list[object]", expected "list[str | int]")

def i() -> List[Union[str, int]]:
    x: List[Union[str, int]] = ['a', 2]
    return x

[builtins fixtures/dict.pyi]

[case testLambdaSemanal]
f = lambda: xyz
[out]
main:1: error: Name "xyz" is not defined

[case testLambdaTypeCheck]
f = lambda: 1 + '1'
[out]
main:1: error: Unsupported operand types for + ("int" and "str")

[case testLambdaTypeInference]
f = lambda: 5
reveal_type(f)
[out]
main:2: note: Revealed type is "def () -> builtins.int"

[case testRevealLocalsFunction]
a = 1.0

class A: pass

def f(a: int, b: int) -> int:
    reveal_locals()
    c = a + b
    class C: pass
    reveal_locals()
    return c

reveal_locals()
[out]
main:6: note: Revealed local types are:
main:6: note:     a: builtins.int
main:6: note:     b: builtins.int
main:9: note: Revealed local types are:
main:9: note:     a: builtins.int
main:9: note:     b: builtins.int
main:9: note:     c: builtins.int
main:12: note: Revealed local types are:
main:12: note:     a: builtins.float

[case testNoComplainOverloadNone]
# flags: --no-strict-optional
from typing import overload, Optional
@overload
def bar(x: None) -> None:
    ...
@overload
def bar(x: int) -> str:
    ...
def bar(x: Optional[int]) -> Optional[str]:
    if x is None:
        return None
    return "number"

reveal_type(bar(None))  # N: Revealed type is "None"
[builtins fixtures/isinstance.pyi]
[out]

[case testNoComplainOverloadNoneStrict]
from typing import overload, Optional
@overload
def bar(x: None) -> None:
    ...
@overload
def bar(x: int) -> str:
    ...
def bar(x: Optional[int]) -> Optional[str]:
    if x is None:
        return None
    return "number"

reveal_type(bar(None))  # N: Revealed type is "None"
[builtins fixtures/isinstance.pyi]
[out]

[case testNoComplainInferredNone]
# flags: --no-strict-optional
from typing import TypeVar, Optional
T = TypeVar('T')
def X(val: T) -> T: ...
x_in = None
def Y(x: Optional[str] = X(x_in)): ...

xx: Optional[int] = X(x_in)
[out]

[case testNoComplainInferredNoneStrict]
from typing import TypeVar, Optional
T = TypeVar('T')
def X(val: T) -> T: ...
x_in = None
def Y(x: Optional[str] = X(x_in)): ...

xx: Optional[int] = X(x_in)
[out]

[case testNoComplainNoneReturnFromUntyped]
def foo() -> None:
    pass

def lol():
    x = foo()

[case testConditionalImportFunction]
import p
[file p/__init__.py]

if int():
    from p.a import f
elif int():
    from p.b import f
else:
    from p.c import f

[file p/a.py]
def f() -> int: ...

[file p/b.py]
from p.d import f

[file p/c.py]
def f() -> int: ...

[file p/d.py]
import p
def f() -> int: ...

[case testLambdaDefaultTypeErrors]
lambda a=(1 + 'asdf'): a  # E: Unsupported operand types for + ("int" and "str")
lambda a=nonsense: a  # E: Name "nonsense" is not defined
def f(x: int = i):  # E: Name "i" is not defined
    i = 42

[case testRevealTypeOfCallExpressionReturningNoneWorks]
def foo() -> None:
    pass

reveal_type(foo()) # N: Revealed type is "None"

[case testAnyArgument]
def a(b: any): pass # E: Function "builtins.any" is not valid as a type \
                    # N: Perhaps you meant "typing.Any" instead of "any"?
[builtins fixtures/any.pyi]

[case testCallableArgument]
def a(b: callable): pass # E: Function "builtins.callable" is not valid as a type \
                         # N: Perhaps you meant "typing.Callable" instead of "callable"?
[builtins fixtures/callable.pyi]

[case testDecoratedProperty]
from typing import TypeVar, Callable, final

T = TypeVar("T")

def dec(f: Callable[[T], int]) -> Callable[[T], str]: ...
def dec2(f: T) -> T: ...

class A:
    @property
    @dec
    def f(self) -> int: pass
    @property
    @dec2
    def g(self) -> int: pass
reveal_type(A().f)  # N: Revealed type is "builtins.str"
reveal_type(A().g)  # N: Revealed type is "builtins.int"

class B:
    @final
    @property
    @dec
    def f(self) -> int: pass
reveal_type(B().f)  # N: Revealed type is "builtins.str"

class C:
    @property  # E: Only instance methods can be decorated with @property
    @classmethod
    def f(cls) -> int: pass
reveal_type(C().f)  # N: Revealed type is "builtins.int"
[builtins fixtures/property.pyi]
[out]

[case testDecoratedPropertySetter]
from typing import TypeVar, Callable, final

T = TypeVar("T")
def dec(f: T) -> T: ...

class A:
    @property
    @dec
    def f(self) -> int: pass
    @f.setter
    @dec
    def f(self, v: int) -> None: pass
reveal_type(A().f)  # N: Revealed type is "builtins.int"

class B:
    @property
    @dec
    def f(self) -> int: pass
    @dec # E: Only supported top decorators are "@f.setter" and "@f.deleter"
    @f.setter
    def f(self, v: int) -> None: pass

class C:
    @dec  # E: Decorators on top of @property are not supported
    @property
    def f(self) -> int: pass
    @f.setter
    @dec
    def f(self, v: int) -> None: pass
[builtins fixtures/property.pyi]

[case testInvalidArgCountForProperty]
from typing import Callable, TypeVar

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

class A:
    @property  # E: Too many arguments for property
    def f(self, x) -> int: pass
    @property  # E: Too many arguments for property
    @dec
    def e(self) -> int: pass
    @property
    def g() -> int: pass   # E: Method must have at least one argument. Did you forget the "self" argument?
    @property
    def h(self, *args, **kwargs) -> int: pass   # OK
[builtins fixtures/property.pyi]

[case testSubtypingUnionGenericBounds]
from typing import Callable, TypeVar, Union, Sequence

TI = TypeVar("TI", bound=int)
TS = TypeVar("TS", bound=str)

f: Callable[[Sequence[TI]], None]
g: Callable[[Union[Sequence[TI], Sequence[TS]]], None]
f = g

[case testOverrideDecoratedProperty]
class Base:
    @property
    def foo(self) -> int: ...

class decorator:
    def __init__(self, fn):
        self.fn = fn
    def __call__(self, decorated_self) -> int:
        return self.fn(decorated_self)

class Child(Base):
    @property
    @decorator
    def foo(self) -> int:
        return 42
reveal_type(Child().foo)  # N: Revealed type is "builtins.int"
Child().foo = 1  # E: Property "foo" defined in "Child" is read-only

reveal_type(Child().foo)  # N: Revealed type is "builtins.int"

class BadChild1(Base):
    @decorator
    def foo(self) -> int:  # E: Signature of "foo" incompatible with supertype "Base" \
                           # N:      Superclass: \
                           # N:          int \
                           # N:      Subclass: \
                           # N:          decorator
        return 42

class not_a_decorator:
    def __init__(self, fn): ...

class BadChild2(Base):
    # Override error not shown as accessing 'foo' on BadChild2 returns Any.
    @property
    @not_a_decorator
    def foo(self) -> int:
        return 42
reveal_type(BadChild2().foo)  # E: "not_a_decorator" not callable \
                              # N: Revealed type is "Any"
[builtins fixtures/property.pyi]

[case explicitOverride]
# flags: --python-version 3.12
from typing import override

class A:
    def f(self, x: int) -> str: pass
    @override
    def g(self, x: int) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class B(A):
    @override
    def f(self, x: int) -> str: pass
    @override
    def g(self, x: int) -> str: pass

class C(A):
    @override
    def f(self, x: str) -> str: pass  # E: Argument 1 of "f" is incompatible with supertype "A"; supertype defines the argument type as "int" \
                                      # N: This violates the Liskov substitution principle \
                                      # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
    def g(self, x: int) -> str: pass

class D(A): pass
class E(D): pass
class F(E):
    @override
    def f(self, x: int) -> str: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideStaticmethod]
# flags: --python-version 3.12
from typing import override

class A:
    @staticmethod
    def f(x: int) -> str: pass

class B(A):
    @staticmethod
    @override
    def f(x: int) -> str: pass
    @override
    @staticmethod
    def g(x: int) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class C(A):  # inverted order of decorators
    @override
    @staticmethod
    def f(x: int) -> str: pass
    @override
    @staticmethod
    def g(x: int) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class D(A):
    @staticmethod
    @override
    def f(x: str) -> str: pass  # E: Argument 1 of "f" is incompatible with supertype "A"; supertype defines the argument type as "int" \
                                # N: This violates the Liskov substitution principle \
                                # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
[typing fixtures/typing-override.pyi]
[builtins fixtures/staticmethod.pyi]

[case explicitOverrideClassmethod]
# flags: --python-version 3.12
from typing import override

class A:
    @classmethod
    def f(cls, x: int) -> str: pass

class B(A):
    @classmethod
    @override
    def f(cls, x: int) -> str: pass
    @override
    @classmethod
    def g(cls, x: int) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class C(A):  # inverted order of decorators
    @override
    @classmethod
    def f(cls, x: int) -> str: pass
    @override
    @classmethod
    def g(cls, x: int) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class D(A):
    @classmethod
    @override
    def f(cls, x: str) -> str: pass  # E: Argument 1 of "f" is incompatible with supertype "A"; supertype defines the argument type as "int" \
                                     # N: This violates the Liskov substitution principle \
                                     # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
[typing fixtures/typing-override.pyi]
[builtins fixtures/classmethod.pyi]

[case explicitOverrideProperty]
# flags: --python-version 3.12
from typing import override

class A:
    @property
    def f(self) -> str: pass

class B(A):
    @property
    @override
    def f(self) -> str: pass
    @override
    @property
    def g(self) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class C(A):  # inverted order of decorators
    @override
    @property
    def f(self) -> str: pass
    @override
    @property
    def g(self) -> str: pass  # E: Method "g" is marked as an override, but no base method was found with this name

class D(A):
    @property
    @override
    def f(self) -> int: pass  # E: Signature of "f" incompatible with supertype "A" \
                              # N:      Superclass: \
                              # N:          str \
                              # N:      Subclass: \
                              # N:          int
[typing fixtures/typing-override.pyi]
[builtins fixtures/property.pyi]

[case explicitOverrideSettableProperty]
# flags: --python-version 3.12
from typing import override

class A:
    @property
    def f(self) -> str: pass

    @f.setter
    def f(self, value: str) -> None: pass

class B(A):
    @property  # E: Read-only property cannot override read-write property
    @override
    def f(self) -> str: pass

class C(A):
    @override
    @property
    def f(self) -> str: pass

    @f.setter
    def f(self, value: str) -> None: pass

class D(A):
    @override  # E: Signature of "f" incompatible with supertype "A" \
               # N:      Superclass: \
               # N:          str \
               # N:      Subclass: \
               # N:          int
    @property
    def f(self) -> int: pass

    @f.setter
    def f(self, value: int) -> None: pass
[typing fixtures/typing-override.pyi]
[builtins fixtures/property.pyi]

[case invalidExplicitOverride]
# flags: --python-version 3.12
from typing import override

@override  # E: "override" used with a non-method
def f(x: int) -> str: pass

@override  # this should probably throw an error but the signature from typeshed should ensure this already
class A: pass

def g() -> None:
    @override  # E: "override" used with a non-method
    def h(b: bool) -> int: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideSpecialMethods]
# flags: --python-version 3.12
from typing import override

class A:
    def __init__(self, a: int) -> None: pass

class B(A):
    @override
    def __init__(self, b: str) -> None: pass

class C:
    @override
    def __init__(self, a: int) -> None: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideFromExtensions]
from typing_extensions import override

class A:
    def f(self, x: int) -> str: pass

class B(A):
    @override
    def f2(self, x: int) -> str: pass  # E: Method "f2" is marked as an override, but no base method was found with this name
[builtins fixtures/tuple.pyi]

[case explicitOverrideOverloads]
# flags: --python-version 3.12
from typing import overload, override

class A:
    def f(self, x: int) -> str: pass

class B(A):
    @overload  # E: Method "f2" is marked as an override, but no base method was found with this name
    def f2(self, x: int) -> str: pass
    @overload
    def f2(self, x: str) -> str: pass
    @override
    def f2(self, x: int | str) -> str: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideNotOnOverloadsImplementation]
# flags: --python-version 3.12
from typing import overload, override

class A:
    def f(self, x: int) -> str: pass

class B(A):
    @overload  # E: Method "f2" is marked as an override, but no base method was found with this name
    def f2(self, x: int) -> str: pass
    @override
    @overload
    def f2(self, x: str) -> str: pass
    def f2(self, x: int | str) -> str: pass

class C(A):
    @overload
    def f(self, y: int) -> str: pass
    @override
    @overload
    def f(self, y: str) -> str: pass
    def f(self, y: int | str) -> str: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideOnMultipleOverloads]
# flags: --python-version 3.12
from typing import overload, override

class A:
    def f(self, x: int) -> str: pass

class B(A):
    @override  # E: Method "f2" is marked as an override, but no base method was found with this name
    @overload
    def f2(self, x: int) -> str: pass
    @override
    @overload
    def f2(self, x: str) -> str: pass
    def f2(self, x: int | str) -> str: pass

class C(A):
    @overload
    def f(self, y: int) -> str: pass
    @override
    @overload
    def f(self, y: str) -> str: pass
    @override
    def f(self, y: int | str) -> str: pass
[typing fixtures/typing-override.pyi]

[case explicitOverrideCyclicDependency]
# flags: --python-version 3.12
import b
[file a.py]
from typing import override
import b
import c

class A(b.B):
    @override  # This is fine
    @c.deco
    def meth(self) -> int: ...
[file b.py]
import a
import c

class B:
    @c.deco
    def meth(self) -> int: ...
[file c.py]
from typing import TypeVar, Tuple, Callable
T = TypeVar('T')
def deco(f: Callable[..., T]) -> Callable[..., Tuple[T, int]]: ...
[builtins fixtures/tuple.pyi]
[typing fixtures/typing-override.pyi]

[case requireExplicitOverrideMethod]
# flags: --enable-error-code explicit-override --python-version 3.12
from typing import override

class A:
    def f(self, x: int) -> str: pass

class B(A):
    @override
    def f(self, y: int) -> str: pass

class C(A):
    def f(self, y: int) -> str: pass  # E: Method "f" is not using @override but is overriding a method in class "__main__.A"

class D(B):
    def f(self, y: int) -> str: pass  # E: Method "f" is not using @override but is overriding a method in class "__main__.B"
[typing fixtures/typing-override.pyi]

[case requireExplicitOverrideSpecialMethod]
# flags: --enable-error-code explicit-override --python-version 3.12
from typing import Callable, Self, TypeVar, override, overload

T = TypeVar('T')
def some_decorator(f: Callable[..., T]) -> Callable[..., T]: ...

# Don't require override decorator for __init__ and __new__
# See: https://github.com/python/typing/issues/1376
class A:
    def __init__(self) -> None: pass
    def __new__(cls) -> Self: pass

class B(A):
    def __init__(self) -> None: pass
    def __new__(cls) -> Self: pass

class C(A):
    @some_decorator
    def __init__(self) -> None: pass

    @some_decorator
    def __new__(cls) -> Self: pass

class D(A):
    @overload
    def __init__(self, x: int) -> None: ...
    @overload
    def __init__(self, x: str) -> None: ...
    def __init__(self, x): pass

    @overload
    def __new__(cls, x: int) -> Self: pass
    @overload
    def __new__(cls, x: str) -> Self: pass
    def __new__(cls, x): pass
[typing fixtures/typing-override.pyi]

[case requireExplicitOverrideProperty]
# flags: --enable-error-code explicit-override --python-version 3.12
from typing import override

class A:
    @property
    def prop(self) -> int: pass

class B(A):
    @override
    @property
    def prop(self) -> int: pass

class C(A):
    @property
    def prop(self) -> int: pass  # E: Method "prop" is not using @override but is overriding a method in class "__main__.A"
[typing fixtures/typing-override.pyi]
[builtins fixtures/property.pyi]

[case requireExplicitOverrideOverload]
# flags: --enable-error-code explicit-override --python-version 3.12
from typing import overload, override

class A:
    @overload
    def f(self, x: int) -> str: ...
    @overload
    def f(self, x: str) -> str: ...
    def f(self, x): pass

class B(A):
    @overload
    def f(self, y: int) -> str: ...
    @overload
    def f(self, y: str) -> str: ...
    @override
    def f(self, y): pass

class C(A):
    @overload
    @override
    def f(self, y: int) -> str: ...
    @overload
    def f(self, y: str) -> str: ...
    def f(self, y): pass

class D(A):
    @overload
    def f(self, y: int) -> str: ...
    @overload
    def f(self, y: str) -> str: ...
    def f(self, y): pass  # E: Method "f" is not using @override but is overriding a method in class "__main__.A"
[typing fixtures/typing-override.pyi]

[case requireExplicitOverrideMultipleInheritance]
# flags: --enable-error-code explicit-override --python-version 3.12
from typing import override

class A:
    def f(self, x: int) -> str: pass
class B:
    def f(self, y: int) -> str: pass

class C(A, B):
    @override
    def f(self, z: int) -> str: pass

class D(A, B):
    def f(self, z: int) -> str: pass  # E: Method "f" is not using @override but is overriding a method in class "__main__.A"
[typing fixtures/typing-override.pyi]

[case testExplicitOverrideAllowedForPrivate]
# flags: --enable-error-code explicit-override --python-version 3.12

class B:
    def __f(self, y: int) -> str: pass

class C(B):
    def __f(self, y: int) -> str: pass  # OK
[typing fixtures/typing-override.pyi]

[case testOverrideUntypedDef]
# flags: --python-version 3.12
from typing import override

class Parent: pass

class Child(Parent):
    @override
    def foo(self, y): pass  # E: Method "foo" is marked as an override, but no base method was found with this name

[typing fixtures/typing-override.pyi]

[case testOverrideOnUnknownBaseClass]
# flags: --python-version 3.12
from typing import overload, override

from unknown import UnknownParent  # type: ignore[import-not-found]

class UnknownChild(UnknownParent):
    @override
    def foo(self, y): pass  # OK
    @override
    def bar(self, y: str) -> None: pass  # OK

    @override
    @overload
    def baz(self, y: str) -> None: ...
    @override
    @overload
    def baz(self, y: int) -> None: ...
    def baz(self, y: str | int) -> None: ...
[typing fixtures/typing-override.pyi]

[case testCallableProperty]
from typing import Callable

class something_callable:
    def __call__(self, fn) -> str: ...

def decorator(fn: Callable[..., int]) -> something_callable: ...

class A:
    @property
    @decorator
    def f(self) -> int: ...

reveal_type(A.f)  # N: Revealed type is "__main__.something_callable"
reveal_type(A().f)  # N: Revealed type is "builtins.str"
[builtins fixtures/property.pyi]

[case testFinalOverrideOnUntypedDef]
from typing import final

class Base:
    @final
    def foo(self):
        pass

class Derived(Base):
    def foo(self):  # E: Cannot override final attribute "foo" (previously declared in base class "Base")
        pass

[case testTypeVarIdClashPolymorphic]
from typing import Callable, Generic, TypeVar

A = TypeVar("A")
B = TypeVar("B")

class Gen(Generic[A]): ...

def id_(x: A) -> A: ...
def f(x: Gen[A], y: A) -> Gen[Gen[A]]: ...
def g(x: Gen[A], id_: Callable[[B], B], f: Callable[[A, B], Gen[A]]) -> A: ...

def test(x: Gen[Gen[A]]) -> Gen[A]:
    return g(x, id_, f)  # Technically OK

x: Gen[Gen[int]]
reveal_type(g(x, id_, f))  # N: Revealed type is "__main__.Gen[builtins.int]"

def h(x: A, y: A) -> A: ...
def gn(id_: Callable[[B], B], step: Callable[[A, B], A]) -> A: ...

def fn(x: A) -> A:
    return gn(id_, h)  # Technically OK

[case testTypeVarIdsNested]
from typing import Callable, TypeVar

A = TypeVar("A")
B = TypeVar("B")

def f(x: Callable[[A], A]) -> Callable[[B], B]:
    def g(x: B) -> B: ...
    return g

reveal_type(f(f))  # N: Revealed type is "def [B] (B`1) -> B`1"
reveal_type(f(f)(f))  # N: Revealed type is "def [A] (x: def (A`-1) -> A`-1) -> def [B] (B`-2) -> B`-2"

[case testGenericUnionFunctionJoin]
from typing import TypeVar, Union

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

def f(x: T, y: S) -> Union[T, S]: ...
def g(x: T, y: S) -> Union[T, S]: ...

x = [f, g]
reveal_type(x)  # N: Revealed type is "builtins.list[def [T, S] (x: T`4, y: S`5) -> T`4 | S`5]"
[builtins fixtures/list.pyi]

[case testTypeVariableClashErrorMessage]
from typing import TypeVar

T = TypeVar("T")

class C:  # Note: Generic[T] missing
    def bad_idea(self, x: T) -> None:
        self.x = x

    def nope(self, x: T) -> None:
        self.x = x  # E: Incompatible types in assignment (expression has type "T@nope", variable has type "T@bad_idea")

[case testNoCrashOnBadCallablePropertyOverride]
from typing import Callable, Union

class C: ...
class D: ...

A = Callable[[C], None]
B = Callable[[D], None]

class Foo:
    @property
    def method(self) -> Callable[[int, Union[A, B]], None]:
        ...

class Bar(Foo):
    @property
    def method(self) -> Callable[[int, A], None]:  # E: Argument 2 of "method" is incompatible with supertype "Foo"; supertype defines the argument type as "Callable[[C], None] | Callable[[D], None]" \
                                                   # N: This violates the Liskov substitution principle \
                                                   # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
        ...
[builtins fixtures/property.pyi]

[case testNoCrashOnUnpackOverride]
from typing import TypedDict, Unpack

class Params(TypedDict):
    x: int
    y: str

class Other(TypedDict):
    x: int
    y: int

class B:
    def meth(self, **kwargs: Unpack[Params]) -> None:
        ...
class C(B):
    def meth(self, **kwargs: Unpack[Other]) -> None:  # E: Signature of "meth" incompatible with supertype "B" \
                                                      # N:      Superclass: \
                                                      # N:          def meth(*, x: int, y: str) -> None \
                                                      # N:      Subclass: \
                                                      # N:          def meth(*, x: int, y: int) -> None
        ...
[builtins fixtures/dict.pyi]
[typing fixtures/typing-full.pyi]

[case testOverrideErrorLocationNamed]
class B:
    def meth(
        self, *,
        x: int,
        y: str,
    ) -> None:
        ...
class C(B):
    def meth(
        self, *,
        y: int,  # E: Argument 1 of "meth" is incompatible with supertype "B"; supertype defines the argument type as "str" \
                 # N: This violates the Liskov substitution principle \
                 # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
        x: int,
    ) -> None:
        ...
[builtins fixtures/tuple.pyi]

[case testLambdaAlwaysAllowed]
# flags: --disallow-untyped-calls
from typing import Callable, Optional

def func() -> Optional[str]: ...
var: Optional[str]

factory: Callable[[], Optional[str]]
for factory in (
    lambda: var,
    func,
):
    reveal_type(factory)  # N: Revealed type is "def () -> builtins.str | None"
    var = factory()
[builtins fixtures/tuple.pyi]

[case testLambdaInDeferredDecoratorNoCrash]
def foo(x):
    pass

class Bar:
    def baz(self, x):
        pass

class Qux(Bar):
    @foo(lambda x: None)
    def baz(self, x) -> None:
        pass
[builtins fixtures/tuple.pyi]

[case testGeneratorInDeferredDecoratorNoCrash]
from typing import Protocol, TypeVar

T = TypeVar("T", covariant=True)

class SupportsNext(Protocol[T]):
    def __next__(self) -> T: ...

def next(i: SupportsNext[T]) -> T: ...

def foo(x):
    pass

class Bar:
    def baz(self, x):
        pass

class Qux(Bar):
    @next(f for f in [foo])
    def baz(self, x) -> None:
        pass
[builtins fixtures/tuple.pyi]

[case testDistinctFormatting]
from typing import Awaitable, Callable, ParamSpec

P = ParamSpec("P")

class A: pass
class B(A): pass

def decorator(f: Callable[P, None]) -> Callable[[Callable[P, A]], None]:
    return lambda _: None

def key(x: int) -> None: ...
def fn_b(b: int) -> B: ...

decorator(key)(fn_b)  # E: Argument 1 has incompatible type "def fn_b(b: int) -> B"; expected "def (x: int) -> A"

def decorator2(f: Callable[P, None]) -> Callable[
    [Callable[P, Awaitable[None]]],
    Callable[P, Awaitable[None]],
]:
    return lambda f: f

def key2(x: int) -> None:
    ...

@decorator2(key2)  # E: Argument 1 has incompatible type "def foo2(y: int) -> Coroutine[Any, Any, None]"; expected "def (x: int) -> Awaitable[None]"
async def foo2(y: int) -> None:
    ...

class Parent:
    def method_without(self) -> "Parent": ...
    def method_with(self, param: str) -> "Parent": ...

class Child(Parent):
    method_without: Callable[[], "Child"]
    method_with: Callable[[str], "Child"]  # E: Incompatible types in assignment (expression has type "Callable[[str], Child]", base class "Parent" defined the type as "def method_with(self, param: str) -> Parent")
[builtins fixtures/tuple.pyi]

[case testDistinctFormattingUnion]
from typing import Callable, Union
from mypy_extensions import Arg

def f(x: Callable[[Arg(int, 'x')], None]) -> None: pass

y: Callable[[Union[int, str]], None]
f(y)  # E: Argument 1 to "f" has incompatible type "Callable[[int | str], None]"; expected "def (x: int) -> None"
[builtins fixtures/tuple.pyi]

[case testAbstractOverloadsWithoutImplementationAllowed]
from abc import abstractmethod
from typing import overload, Union

class Foo:
    @overload
    @abstractmethod
    def foo(self, value: int) -> int:
        ...
    @overload
    @abstractmethod
    def foo(self, value: str) -> str:
        ...

class Bar(Foo):
    @overload
    def foo(self, value: int) -> int:
        ...
    @overload
    def foo(self, value: str) -> str:
        ...

    def foo(self, value: Union[int, str]) -> Union[int, str]:
        return super().foo(value)  # E: Call to abstract method "foo" of "Foo" with trivial body via super() is unsafe

[case fullNamesOfImportedBaseClassesDisplayed]
from a import A

class B(A):
    def f(self, x: str) -> None:  # E: Argument 1 of "f" is incompatible with supertype "a.A"; supertype defines the argument type as "int" \
                                  # N: This violates the Liskov substitution principle \
                                  # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
        ...
    def g(self, x: str) -> None:  # E: Signature of "g" incompatible with supertype "a.A" \
                                  # N:      Superclass: \
                                  # N:          def g(self) -> None \
                                  # N:      Subclass: \
                                  # N:          def g(self, x: str) -> None
        ...

[file a.py]
class A:
    def f(self, x: int) -> None:
        ...
    def g(self) -> None:
        ...

[case testBoundMethodsAssignedInClassBody]
from typing import Callable

class A:
    def f(self, x: int) -> str:
        pass
    @classmethod
    def g(cls, x: int) -> str:
        pass
    @staticmethod
    def h(x: int) -> str:
        pass
    attr: Callable[[int], str]

class C:
    x1 = A.f
    x2 = A.g
    x3 = A().f
    x4 = A().g
    x5 = A.h
    x6 = A().h
    x7 = A().attr

reveal_type(C.x1)  # N: Revealed type is "def (self: __main__.A, x: builtins.int) -> builtins.str"
reveal_type(C.x2)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C.x3)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C.x4)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C.x5)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C.x6)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C.x7)  # N: Revealed type is "def (builtins.int) -> builtins.str"

reveal_type(C().x1)  # E: Invalid self argument "C" to attribute function "x1" with type "Callable[[A, int], str]" \
                     # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x2)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x3)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x4)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x5)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x6)  # N: Revealed type is "def (x: builtins.int) -> builtins.str"
reveal_type(C().x7)  # E: Invalid self argument "C" to attribute function "x7" with type "Callable[[int], str]" \
                     # N: Revealed type is "def () -> builtins.str"
[builtins fixtures/classmethod.pyi]

[case testFunctionRedefinitionDeferred]
from typing import Callable, TypeVar

def outer() -> None:
    if bool():
        def inner() -> str: ...
    else:
        def inner() -> int: ...  # E: All conditional function variants must have identical signatures \
                                 # N: Original: \
                                 # N:     def inner() -> str \
                                 # N: Redefinition: \
                                 # N:     def inner() -> int
    x = defer()

T = TypeVar("T")
def deco(fn: Callable[[], T]) -> Callable[[], list[T]]: ...

@deco
def defer() -> int: ...
[builtins fixtures/list.pyi]

[case testCheckFunctionErrorContextDuplicateDeferred]
# flags: --show-error-context
from typing import Callable, TypeVar

def a() -> None:
    def b() -> None:
        1 + ""
        x = defer()

T = TypeVar("T")
def deco(fn: Callable[[], T]) -> Callable[[], list[T]]: ...

@deco
def defer() -> int: ...
[out]
main: note: In function "a":
main:6: error: Unsupported operand types for + ("int" and "str")

[case testNoExtraNoteForUnpacking]
from typing import Protocol

class P(Protocol):
    arg: int
    # Something that list and dict also have
    def __contains__(self, item: object) -> bool: ...

def foo(x: P, y: P) -> None: ...

args: list[object]
foo(*args)  # E: Argument 1 to "foo" has incompatible type "*list[object]"; expected "P"
kwargs: dict[str, object]
foo(**kwargs)  # E: Argument 1 to "foo" has incompatible type "**dict[str, object]"; expected "P"
[builtins fixtures/dict.pyi]

[case testMissingPositionalArgumentShiftedTypes]
def f(x: int, y: str, z: bytes, aa: int) -> None: ...

f(1, b'x', 1)
[builtins fixtures/primitives.pyi]
[out]
main:3: error: Argument 2 to "f" has incompatible type "bytes"; expected "str" (did you forget argument "y"?)

[case testMissingPositionalArgumentShiftedTypesFirstArg]
def f(x: int, y: str, z: bytes) -> None: ...

f("hello", b'x')
[builtins fixtures/primitives.pyi]
[out]
main:3: error: Argument 1 to "f" has incompatible type "str"; expected "int" (did you forget argument "x"?)

[case testMissingPositionalArgumentNoShift]
def f(x: int, y: str, z: bytes) -> None: ...

f("wrong", 123)
[builtins fixtures/primitives.pyi]
[out]
main:3: error: Missing positional argument "z" in call to "f"
main:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"
main:3: error: Argument 2 to "f" has incompatible type "int"; expected "str"

[case testMissingPositionalArgumentShiftedTypesManyArgs]
def f(a: int, b: str, c: float, d: list[int], e: tuple[str, ...]) -> None: ...

f(1, 1.5, [1, 2, 3], ("a", "b"))
[builtins fixtures/list.pyi]
[out]
main:3: error: Argument 2 to "f" has incompatible type "float"; expected "str" (did you forget argument "b"?)

[case testMissingPositionalArgumentShiftedWithDefaults]
def f(x: int, y: str, z: bytes = b'default') -> None: ...

f("hello")
[builtins fixtures/primitives.pyi]
[out]
main:3: error: Missing positional argument "y" in call to "f"
main:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"

[case testMissingPositionalArgumentShiftedWithStarArgs]
def f(x: int, y: str, z: bytes, *args: int) -> None: ...

f("hello", b'x')
[builtins fixtures/primitives.pyi]
[out]
main:3: error: Missing positional argument "z" in call to "f"
main:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"
main:3: error: Argument 2 to "f" has incompatible type "bytes"; expected "str"