check-functools.test

[case testTotalOrderingEqLt]
from functools import total_ordering

@total_ordering
class Ord:
    def __eq__(self, other: object) -> bool:
        return False

    def __lt__(self, other: "Ord") -> bool:
        return False

reveal_type(Ord() < Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() <= Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() == Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() > Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() >= Ord())  # N: Revealed type is "builtins.bool"

Ord() < 1  # E: Unsupported operand types for < ("Ord" and "int")
Ord() <= 1  # E: Unsupported operand types for <= ("Ord" and "int")
Ord() == 1
Ord() > 1  # E: Unsupported operand types for > ("Ord" and "int")
Ord() >= 1  # E: Unsupported operand types for >= ("Ord" and "int")
[builtins fixtures/dict.pyi]

[case testTotalOrderingLambda]
from functools import total_ordering
from typing import Any, Callable, ClassVar

@total_ordering
class Ord:
    __eq__: Callable[[Any, object], bool] = lambda self, other: False
    __lt__: Callable[[Any, "Ord"], bool] = lambda self, other: False

reveal_type(Ord() < Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() <= Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() == Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() > Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() >= Ord())  # N: Revealed type is "builtins.bool"

Ord() < 1  # E: Argument 1 has incompatible type "int"; expected "Ord"
Ord() <= 1  # E: Unsupported operand types for <= ("Ord" and "int")
Ord() == 1
Ord() > 1  # E: Unsupported operand types for > ("Ord" and "int")
Ord() >= 1  # E: Unsupported operand types for >= ("Ord" and "int")
[builtins fixtures/dict.pyi]

[case testTotalOrderingNonCallable]
from functools import total_ordering

@total_ordering
class Ord(object):
    def __eq__(self, other: object) -> bool:
        return False

    __lt__ = 5

Ord() <= Ord()  # E: Unsupported left operand type for <= ("Ord")
Ord() > Ord()  # E: "int" not callable
Ord() >= Ord()  # E: Unsupported left operand type for >= ("Ord")
[builtins fixtures/dict.pyi]

[case testTotalOrderingReturnNotBool]
from functools import total_ordering

@total_ordering
class Ord:
    def __eq__(self, other: object) -> bool:
        return False

    def __lt__(self, other: "Ord") -> str:
        return "blah"

reveal_type(Ord() < Ord())  # N: Revealed type is "builtins.str"
reveal_type(Ord() <= Ord())  # N: Revealed type is "Any"
reveal_type(Ord() == Ord())  # N: Revealed type is "builtins.bool"
reveal_type(Ord() > Ord())  # N: Revealed type is "Any"
reveal_type(Ord() >= Ord())  # N: Revealed type is "Any"
[builtins fixtures/dict.pyi]

[case testTotalOrderingAllowsAny]
from functools import total_ordering

@total_ordering
class Ord:
    def __eq__(self, other):
        return False

    def __gt__(self, other):
        return False

reveal_type(Ord() < Ord())  # N: Revealed type is "Any"
Ord() <= Ord()  # E: Unsupported left operand type for <= ("Ord")
reveal_type(Ord() == Ord())  # N: Revealed type is "Any"
reveal_type(Ord() > Ord())  # N: Revealed type is "Any"
Ord() >= Ord()  # E: Unsupported left operand type for >= ("Ord")

Ord() < 1  # E: Unsupported left operand type for < ("Ord")
Ord() <= 1  # E: Unsupported left operand type for <= ("Ord")
Ord() == 1
Ord() > 1
Ord() >= 1  # E: Unsupported left operand type for >= ("Ord")
[builtins fixtures/dict.pyi]

[case testCachedProperty]
from functools import cached_property
class Parent:
    @property
    def f(self) -> str: pass
class Child(Parent):
    @cached_property
    def f(self) -> str: pass
    @cached_property
    def g(self) -> int: pass
    @cached_property  # E: Too many arguments for property
    def h(self, arg) -> int: pass
reveal_type(Parent().f)  # N: Revealed type is "builtins.str"
reveal_type(Child().f)  # N: Revealed type is "builtins.str"
reveal_type(Child().g)  # N: Revealed type is "builtins.int"
Child().f = "Hello World"
Child().g = "invalid"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
[file functools.pyi]
import sys
from typing import TypeVar, Generic
_T = TypeVar('_T')
class cached_property(Generic[_T]): ...
[builtins fixtures/property.pyi]

[case testTotalOrderingWithForwardReference]
from typing import Generic, Any, TypeVar
import functools

T = TypeVar("T", bound="C")

@functools.total_ordering
class D(Generic[T]):
    def __lt__(self, other: Any) -> bool:
        ...

class C:
    pass

def f(d: D[C]) -> None:
    reveal_type(d.__gt__)  # N: Revealed type is "def (other: Any) -> builtins.bool"

d: D[int]  # E: Type argument "int" of "D" must be a subtype of "C"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialBasic]
from typing import Callable
import functools

def foo(a: int, b: str, c: int = 5) -> int: ...

p1 = functools.partial(foo)
p1(1, "a", 3)  # OK
p1(1, "a", c=3)  # OK
p1(1, b="a", c=3)  # OK

reveal_type(p1)  # N: Revealed type is "functools.partial[builtins.int]"

def takes_callable_int(f: Callable[..., int]) -> None: ...
def takes_callable_str(f: Callable[..., str]) -> None: ...
takes_callable_int(p1)
takes_callable_str(p1)  # E: Argument 1 to "takes_callable_str" has incompatible type "partial[int]"; expected "Callable[..., str]" \
                        # N: "partial[int].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> int"

p2 = functools.partial(foo, 1)
p2("a")  # OK
p2("a", 3)  # OK
p2("a", c=3)  # OK
p2(1, 3)  # E: Argument 1 to "foo" has incompatible type "int"; expected "str"
p2(1, "a", 3)  # E: Too many arguments for "foo" \
               # E: Argument 1 to "foo" has incompatible type "int"; expected "str" \
               # E: Argument 2 to "foo" has incompatible type "str"; expected "int"
p2(a=1, b="a", c=3)  # E: Unexpected keyword argument "a" for "foo"

p3 = functools.partial(foo, b="a")
p3(1)  # OK
p3(1, c=3)  # OK
p3(a=1)  # OK
p3(1, b="a", c=3)  # OK, keywords can be clobbered
p3(1, 3)  # E: Too many positional arguments for "foo" \
          # E: Argument 2 to "foo" has incompatible type "int"; expected "str"

functools.partial(foo, "a")  # E: Argument 1 to "foo" has incompatible type "str"; expected "int"
functools.partial(foo, b=1)  # E: Argument "b" to "foo" has incompatible type "int"; expected "str"
functools.partial(foo, a=1, b=2, c=3)  # E: Argument "b" to "foo" has incompatible type "int"; expected "str"
functools.partial(1)  # E: "int" not callable \
                      # E: Argument 1 to "partial" has incompatible type "int"; expected "Callable[..., Never]"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialStar]
import functools
from typing import List

def foo(a: int, b: str, *args: int, d: str, **kwargs: int) -> int: ...

p1 = functools.partial(foo, 1, d="a", x=9)
p1("a", 2, 3, 4)  # OK
p1("a", 2, 3, 4, d="a")  # OK
p1("a", 2, 3, 4, "a")  # E: Argument 5 to "foo" has incompatible type "str"; expected "int"
p1("a", 2, 3, 4, x="a")  # E: Argument "x" to "foo" has incompatible type "str"; expected "int"

p2 = functools.partial(foo, 1, "a")
p2(2, 3, 4, d="a")  # OK
p2("a")  # E: Missing named argument "d" for "foo" \
         # E: Argument 1 to "foo" has incompatible type "str"; expected "int"
p2(2, 3, 4)  # E: Missing named argument "d" for "foo"

functools.partial(foo, 1, "a", "b", "c", d="a")  # E: Argument 3 to "foo" has incompatible type "str"; expected "int" \
                                                 # E: Argument 4 to "foo" has incompatible type "str"; expected "int"

def bar(*a: bytes, **k: int):
    p1("a", 2, 3, 4, d="a", **k)
    p1("a", d="a", **k)
    p1("a", **k)  # E: Argument 2 to "foo" has incompatible type "**dict[str, int]"; expected "str"
    p1(**k)  # E: Argument 1 to "foo" has incompatible type "**dict[str, int]"; expected "str"
    p1(*a)  # E: Expected iterable as variadic argument


def baz(a: int, b: int) -> int: ...
def test_baz(xs: List[int]):
    p3 = functools.partial(baz, *xs)
    p3()
    p3(1)  # E: Too many arguments for "baz"


[builtins fixtures/dict.pyi]

[case testFunctoolsPartialGeneric]
from typing import TypeVar
import functools

T = TypeVar("T")
U = TypeVar("U")

def foo(a: T, b: T) -> T: ...

p1 = functools.partial(foo, 1)
reveal_type(p1(2))  # N: Revealed type is "builtins.int"
p1("a")  # E: Argument 1 to "foo" has incompatible type "str"; expected "int"

p2 = functools.partial(foo, "a")
p2(1)  # E: Argument 1 to "foo" has incompatible type "int"; expected "str"
reveal_type(p2("a"))  # N: Revealed type is "builtins.str"

def bar(a: T, b: U) -> U: ...

p3 = functools.partial(bar, 1)
reveal_type(p3(2))  # N: Revealed type is "builtins.int"
reveal_type(p3("a"))  # N: Revealed type is "builtins.str"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialCallable]
from typing import Callable
import functools

def main1(f: Callable[[int, str], int]) -> None:
    p = functools.partial(f, 1)
    p("a")  # OK
    p(1)  # E: Argument 1 has incompatible type "int"; expected "str"

    functools.partial(f, a=1)  # E: Unexpected keyword argument "a"

class CallbackProto:
    def __call__(self, a: int, b: str) -> int: ...

def main2(f: CallbackProto) -> None:
    p = functools.partial(f, b="a")
    p(1)  # OK
    p("a")  # E: Argument 1 to "__call__" of "CallbackProto" has incompatible type "str"; expected "int"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialOverload]
from typing import overload
import functools

@overload
def foo(a: int, b: str) -> int: ...
@overload
def foo(a: str, b: int) -> str: ...
def foo(*a, **k): ...

p1 = functools.partial(foo)
reveal_type(p1(1, "a"))  # N: Revealed type is "builtins.int"
reveal_type(p1("a", 1))  # N: Revealed type is "builtins.int"
p1(1, 2)  # TODO: false negative
p1("a", "b")  # TODO: false negative
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialTypeGuard]
import functools
from typing_extensions import TypeGuard

def is_str_list(val: list[object]) -> TypeGuard[list[str]]: ...

reveal_type(functools.partial(is_str_list, [1, 2, 3]))  # N: Revealed type is "functools.partial[builtins.bool]"
reveal_type(functools.partial(is_str_list, [1, 2, 3])())  # N: Revealed type is "builtins.bool"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialType]
import functools
from typing import Type

class A:
    def __init__(self, a: int, b: str) -> None: ...

p = functools.partial(A, 1)
reveal_type(p)  # N: Revealed type is "functools.partial[__main__.A]"

p("a")  # OK
p(1)  # E: Argument 1 to "A" has incompatible type "int"; expected "str"
p(z=1)  # E: Unexpected keyword argument "z" for "A"

def main(t: Type[A]) -> None:
    p = functools.partial(t, 1)
    reveal_type(p)  # N: Revealed type is "functools.partial[__main__.A]"

    p("a")  # OK
    p(1)  # E: Argument 1 to "A" has incompatible type "int"; expected "str"
    p(z=1)  # E: Unexpected keyword argument "z" for "A"

[builtins fixtures/dict.pyi]

[case testFunctoolsPartialTypeVarTuple]
import functools
import typing
Ts = typing.TypeVarTuple("Ts")
def foo(fn: typing.Callable[[typing.Unpack[Ts]], None], /, *arg: typing.Unpack[Ts], kwarg: str) -> None: ...
p = functools.partial(foo, kwarg="asdf")

def bar(a: int, b: str, c: float) -> None: ...
p(bar, 1, "a", 3.0)  # OK
p(bar, 1, "a", 3.0, kwarg="asdf")  # OK
p(bar, 1, "a", "b")  # E: Argument 1 to "foo" has incompatible type "Callable[[int, str, float], None]"; expected "Callable[[int, str, str], None]"
[builtins fixtures/dict.pyi]

[case testFunctoolsPartialUnion]
import functools
from typing import Any, Callable, Union

cls1: Any
cls2: Union[Any, Any]
reveal_type(functools.partial(cls1, 2)())  # N: Revealed type is "Any"
reveal_type(functools.partial(cls2, 2)())  # N: Revealed type is "Any"

fn1: Union[Callable[[int], int], Callable[[int], int]]
reveal_type(functools.partial(fn1, 2)())  # N: Revealed type is "builtins.int"

fn2: Union[Callable[[int], int], Callable[[int], str]]
reveal_type(functools.partial(fn2, 2)())  # N: Revealed type is "builtins.int | builtins.str"

fn3: Union[Callable[[int], int], str]
reveal_type(functools.partial(fn3, 2)())  # E: "str" not callable \
                                          # N: Revealed type is "builtins.int" \
                                          # E: Argument 1 to "partial" has incompatible type "Callable[[int], int] | str"; expected "Callable[..., int]"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialUnionOfTypeAndCallable]
import functools
from typing import Callable, Union, Type
from typing_extensions import TypeAlias

class FooBar:
    def __init__(self, arg1: str) -> None:
        pass

def f1(t: Union[Type[FooBar], Callable[..., 'FooBar']]) -> None:
    val = functools.partial(t)

FooBarFunc: TypeAlias = Callable[..., 'FooBar']

def f2(t: Union[Type[FooBar], FooBarFunc]) -> None:
    val = functools.partial(t)
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialExplicitType]
from functools import partial
from typing import Type, TypeVar, Callable

T = TypeVar("T")
def generic(string: str, integer: int, resulting_type: Type[T]) -> T: ...

p: partial[str] = partial(generic, resulting_type=str)
q: partial[bool] = partial(generic, resulting_type=str)  # E: Argument "resulting_type" to "generic" has incompatible type "type[str]"; expected "type[bool]"

pc: Callable[..., str] = partial(generic, resulting_type=str)
qc: Callable[..., bool] = partial(generic, resulting_type=str)  # E: Incompatible types in assignment (expression has type "partial[str]", variable has type "Callable[..., bool]") \
                                                                # N: "partial[str].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> str"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialNestedPartial]
from functools import partial
from typing import Any

def foo(x: int) -> int: ...
p = partial(partial, foo)
reveal_type(p()(1))  # N: Revealed type is "builtins.int"
p()("no")  # E: Argument 1 to "foo" has incompatible type "str"; expected "int"

q = partial(partial, partial, foo)
q()()("no")  # E: Argument 1 to "foo" has incompatible type "str"; expected "int"

r = partial(partial, foo, 1)
reveal_type(r()())  # N: Revealed type is "builtins.int"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypeObject]
import functools
from typing import Type, Generic, TypeVar

class A:
    def __init__(self, val: int) -> None: ...

cls1: Type[A]
reveal_type(functools.partial(cls1, 2)())  # N: Revealed type is "__main__.A"
functools.partial(cls1, "asdf")  # E: Argument 1 to "A" has incompatible type "str"; expected "int"

T = TypeVar("T")
class B(Generic[T]):
    def __init__(self, val: T) -> None: ...

cls2: Type[B[int]]
reveal_type(functools.partial(cls2, 2)())  # N: Revealed type is "__main__.B[builtins.int]"
functools.partial(cls2, "asdf")  # E: Argument 1 to "B" has incompatible type "str"; expected "int"

def foo(cls3: Type[B[T]]):
    reveal_type(functools.partial(cls3, "asdf"))  # N: Revealed type is "functools.partial[__main__.B[T`-1]]" \
                                                  # E: Argument 1 to "B" has incompatible type "str"; expected "T"
    reveal_type(functools.partial(cls3, 2)())  # N: Revealed type is "__main__.B[T`-1]" \
                                               # E: Argument 1 to "B" has incompatible type "int"; expected "T"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypedDictUnpack]
from typing import TypedDict
from typing_extensions import Unpack
from functools import partial

class D1(TypedDict, total=False):
    a1: int

def fn1(a1: int) -> None: ...
def main1(**d1: Unpack[D1]) -> None:
    partial(fn1, **d1)()
    partial(fn1, **d1)(**d1)
    partial(fn1, **d1)(a1=1)
    partial(fn1, **d1)(a1="asdf")  # E: Argument "a1" to "fn1" has incompatible type "str"; expected "int"
    partial(fn1, **d1)(oops=1)  # E: Unexpected keyword argument "oops" for "fn1"

def fn2(**kwargs: Unpack[D1]) -> None: ...
def main2(**d1: Unpack[D1]) -> None:
    partial(fn2, **d1)()
    partial(fn2, **d1)(**d1)
    partial(fn2, **d1)(a1=1)
    partial(fn2, **d1)(a1="asdf")  # E: Argument "a1" to "fn2" has incompatible type "str"; expected "int"
    partial(fn2, **d1)(oops=1)  # E: Unexpected keyword argument "oops" for "fn2"

class D2(TypedDict, total=False):
    a1: int
    a2: str

class A2Good(TypedDict, total=False):
    a2: str
class A2Bad(TypedDict, total=False):
    a2: int

def fn3(a1: int, a2: str) -> None: ...
def main3(a2good: A2Good, a2bad: A2Bad, **d2: Unpack[D2]) -> None:
    partial(fn3, **d2)()
    partial(fn3, **d2)(a1=1, a2="asdf")

    partial(fn3, **d2)(**d2)

    partial(fn3, **d2)(a1="asdf")  # E: Argument "a1" to "fn3" has incompatible type "str"; expected "int"
    partial(fn3, **d2)(a1=1, a2="asdf", oops=1)  # E: Unexpected keyword argument "oops" for "fn3"

    partial(fn3, **d2)(**a2good)
    partial(fn3, **d2)(**a2bad)  # E: Argument "a2" to "fn3" has incompatible type "int"; expected "str"

def fn4(**kwargs: Unpack[D2]) -> None: ...
def main4(a2good: A2Good, a2bad: A2Bad, **d2: Unpack[D2]) -> None:
    partial(fn4, **d2)()
    partial(fn4, **d2)(a1=1, a2="asdf")

    partial(fn4, **d2)(**d2)

    partial(fn4, **d2)(a1="asdf")  # E: Argument "a1" to "fn4" has incompatible type "str"; expected "int"
    partial(fn4, **d2)(a1=1, a2="asdf", oops=1)  # E: Unexpected keyword argument "oops" for "fn4"

    partial(fn3, **d2)(**a2good)
    partial(fn3, **d2)(**a2bad)  # E: Argument "a2" to "fn3" has incompatible type "int"; expected "str"

def main5(**d2: Unpack[D2]) -> None:
    partial(fn1, **d2)()  # E: Extra argument "a2" from **args for "fn1"
    partial(fn2, **d2)()  # E: Extra argument "a2" from **args for "fn2"

def main6(a2good: A2Good, a2bad: A2Bad, **d1: Unpack[D1]) -> None:
    partial(fn3, **d1)()  # E: Missing positional argument "a1" in call to "fn3"
    partial(fn3, **d1)("asdf")  # E: Too many positional arguments for "fn3" \
                                # E: Too few arguments for "fn3" \
                                # E: Argument 1 to "fn3" has incompatible type "str"; expected "int"
    partial(fn3, **d1)(a2="asdf")
    partial(fn3, **d1)(**a2good)
    partial(fn3, **d1)(**a2bad)  # E: Argument "a2" to "fn3" has incompatible type "int"; expected "str"

    partial(fn4, **d1)()
    partial(fn4, **d1)("asdf")  # E: Too many positional arguments for "fn4" \
                                # E: Argument 1 to "fn4" has incompatible type "str"; expected "int"
    partial(fn4, **d1)(a2="asdf")
    partial(fn4, **d1)(**a2good)
    partial(fn4, **d1)(**a2bad)  # E: Argument "a2" to "fn4" has incompatible type "int"; expected "str"
[builtins fixtures/dict.pyi]
[typing fixtures/typing-typeddict.pyi]


[case testFunctoolsPartialNestedGeneric]
from functools import partial
from typing import Generic, TypeVar, List

T = TypeVar("T")
def get(n: int, args: List[T]) -> T: ...
first = partial(get, 0)

x: List[str]
reveal_type(first(x))  # N: Revealed type is "builtins.str"
reveal_type(first([1]))  # N: Revealed type is "builtins.int"

first_kw = partial(get, n=0)
reveal_type(first_kw(args=[1]))  # N: Revealed type is "builtins.int"

# TODO: this is indeed invalid, but the error is incomprehensible.
first_kw([1])  # E: Too many positional arguments for "get" \
               # E: Too few arguments for "get" \
               # E: Argument 1 to "get" has incompatible type "list[int]"; expected "int"
[builtins fixtures/list.pyi]

[case testFunctoolsPartialHigherOrder]
from functools import partial
from typing import Callable

def fn(a: int, b: str, c: bytes) -> int: ...

def callback1(fn: Callable[[str, bytes], int]) -> None: ...
def callback2(fn: Callable[[str, int], int]) -> None: ...

callback1(partial(fn, 1))
# TODO: false negative
# https://github.com/python/mypy/issues/17461
callback2(partial(fn, 1))
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialClassObjectMatchingPartial]
from functools import partial

class A:
    def __init__(self, var: int, b: int, c: int) -> None: ...

p = partial(A, 1)
reveal_type(p)  # N: Revealed type is "functools.partial[__main__.A]"
p(1, "no")  # E: Argument 2 to "A" has incompatible type "str"; expected "int"

q: partial[A] = partial(A, 1)  # OK
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypeVarBound]
from typing import Callable, TypeVar, Type
import functools

T = TypeVar("T", bound=Callable[[str, int], str])
S = TypeVar("S", bound=Type[int])

def foo(f: T) -> T:
    g = functools.partial(f, "foo")
    return f

def bar(f: S) -> S:
    g = functools.partial(f, "foo")
    return f
[builtins fixtures/primitives.pyi]

[case testFunctoolsPartialAbstractType]
from abc import ABC, abstractmethod
from functools import partial

class A(ABC):
    def __init__(self) -> None: ...
    @abstractmethod
    def method(self) -> None: ...

def f1(cls: type[A]) -> None:
    cls()
    partial_cls = partial(cls)
    partial_cls()

def f2() -> None:
    A()  # E: Cannot instantiate abstract class "A" with abstract attribute "method"
    partial_cls = partial(A)  # E: Cannot instantiate abstract class "A" with abstract attribute "method" \
                              # E: Argument 1 to "partial" has incompatible type "type[A]"; expected "Callable[..., A]"
    partial_cls()  # E: Cannot instantiate abstract class "A" with abstract attribute "method"

[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialSelfType]
from functools import partial
from typing_extensions import Self

class A:
    def __init__(self, ts: float, msg: str) -> None: ...

    @classmethod
    def from_msg(cls, msg: str) -> Self:
        factory = partial(cls, ts=0)
        return factory(msg=msg)
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypeVarValues]
from functools import partial
from typing import TypeVar

T = TypeVar("T", int, str)

def f(x: int, y: T) -> T:
    return y

def g(x: T, y: int) -> T:
    return x

def h(x: T, y: T) -> T:
    return x

fp = partial(f, 1)
reveal_type(fp(1))  # N: Revealed type is "builtins.int"
reveal_type(fp("a"))  # N: Revealed type is "builtins.str"
fp(object())  # E: Value of type variable "T" of "f" cannot be "object"

gp = partial(g, 1)
reveal_type(gp(1))  # N: Revealed type is "builtins.int"
gp("a")  # E: Argument 1 to "g" has incompatible type "str"; expected "int"

hp = partial(h, 1)
reveal_type(hp(1))  # N: Revealed type is "builtins.int"
hp("a")  # E: Argument 1 to "h" has incompatible type "str"; expected "int"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialOverloadedCallableProtocol]
from functools import partial
from typing import Callable, Protocol, overload

class P(Protocol):
    @overload
    def __call__(self, x: int) -> int: ...
    @overload
    def __call__(self, x: str) -> str: ...

def f(x: P):
    reveal_type(partial(x, 1)())  # N: Revealed type is "builtins.int"

    # TODO: but this is incorrect, predating the functools.partial plugin
    reveal_type(partial(x, "a")())  # N: Revealed type is "builtins.int"
[builtins fixtures/tuple.pyi]

[case testFunctoolsPartialTypeVarErasure]
from typing import Callable, TypeVar, Union
from typing_extensions import ParamSpec, TypeVarTuple, Unpack
from functools import partial

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

Tc = TypeVar("Tc", int, str)
Tb = TypeVar("Tb", bound=Union[int, str])
P = ParamSpec("P")
Ts = TypeVarTuple("Ts")

def func_b(a: Tb, b: str) -> Tb:
    return a
def func_c(a: Tc, b: str) -> Tc:
    return a

def func_fn(fn: Callable[P, Tc], b: str) -> Callable[P, Tc]:
    return fn
def func_fn_unpack(fn: Callable[[Unpack[Ts]], Tc], b: str) -> Callable[[Unpack[Ts]], Tc]:
    return fn

# We should not leak stray typevars that aren't in scope:
reveal_type(partial(func_b, b=""))  # N: Revealed type is "functools.partial[Any]"
reveal_type(partial(func_c, b=""))  # N: Revealed type is "functools.partial[Any]"
reveal_type(partial(func_fn, b=""))  # N: Revealed type is "functools.partial[def (*Any, **Any) -> Any]"
reveal_type(partial(func_fn_unpack, b=""))  # N: Revealed type is "functools.partial[def (*Any) -> Any]"

use_int_callable(partial(func_b, b=""))
use_func_callable(partial(func_b, b=""))
use_int_callable(partial(func_c, b=""))
use_func_callable(partial(func_c, b=""))
use_int_callable(partial(func_fn, b=""))  # E: Argument 1 to "use_int_callable" has incompatible type "partial[def (*Any, **Any) -> Any]"; expected "Callable[[int], int]" \
                                          # N: "partial[def (*Any, **Any) -> Any].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> def (*Any, **Any) -> Any"
use_func_callable(partial(func_fn, b=""))
use_int_callable(partial(func_fn_unpack, b=""))  # E: Argument 1 to "use_int_callable" has incompatible type "partial[def (*Any) -> Any]"; expected "Callable[[int], int]" \
                                                 # N: "partial[def (*Any) -> Any].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> def (*Any) -> Any"
use_func_callable(partial(func_fn_unpack, b=""))

# But we should not erase typevars that aren't bound by function
# passed to `partial`:

def outer_b(arg: Tb) -> None:

    def inner(a: Tb, b: str) -> Tb:
        return a

    reveal_type(partial(inner, b=""))  # N: Revealed type is "functools.partial[Tb`-1]"
    use_int_callable(partial(inner, b=""))  # E: Argument 1 to "use_int_callable" has incompatible type "partial[Tb]"; expected "Callable[[int], int]" \
                                            # N: "partial[Tb].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> Tb"

def outer_c(arg: Tc) -> None:

    def inner(a: Tc, b: str) -> Tc:
        return a

    reveal_type(partial(inner, b=""))  # N: Revealed type is "functools.partial[builtins.int]" \
                                       # N: Revealed type is "functools.partial[builtins.str]"
    use_int_callable(partial(inner, b=""))  # E: Argument 1 to "use_int_callable" has incompatible type "partial[str]"; expected "Callable[[int], int]" \
                                            # N: "partial[str].__call__" has type "def __call__(__self, *args: Any, **kwargs: Any) -> str"
[builtins fixtures/tuple.pyi]