test-data/unit/check-dataclasses.test

[case testDataclassesBasic]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Person:
    name: str
    age: int

    def summary(self):
        return "%s is %d years old." % (self.name, self.age)

reveal_type(Person)  # N: Revealed type is "def (name: builtins.str, age: builtins.int) -> __main__.Person"
Person('John', 32)
Person('Jonh', 21, None)  # E: Too many arguments for "Person"

[builtins fixtures/dataclasses.pyi]
[typing fixtures/typing-medium.pyi]

[case testDataclassesCustomInit]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class A:
    a: int

    def __init__(self, a: str) -> None:
        pass

A('1')

[builtins fixtures/dataclasses.pyi]

[case testDataclassesBasicInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Mammal:
    age: int

@dataclass
class Person(Mammal):
    name: str

    def summary(self):
        return "%s is %d years old." % (self.name, self.age)

reveal_type(Person)  # N: Revealed type is "def (age: builtins.int, name: builtins.str) -> __main__.Person"
Mammal(10)
Person(32, 'John')
Person(21, 'Jonh', None)  # E: Too many arguments for "Person"

[builtins fixtures/dataclasses.pyi]
[typing fixtures/typing-medium.pyi]

[case testDataclassesDeepInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class A:
    a: int

@dataclass
class B(A):
    b: int

@dataclass
class C(B):
    c: int

@dataclass
class D(C):
    d: int

reveal_type(A)  # N: Revealed type is "def (a: builtins.int) -> __main__.A"
reveal_type(B)  # N: Revealed type is "def (a: builtins.int, b: builtins.int) -> __main__.B"
reveal_type(C)  # N: Revealed type is "def (a: builtins.int, b: builtins.int, c: builtins.int) -> __main__.C"
reveal_type(D)  # N: Revealed type is "def (a: builtins.int, b: builtins.int, c: builtins.int, d: builtins.int) -> __main__.D"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesMultipleInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass, field, InitVar
@dataclass
class A:
    a: bool

@dataclass
class B:
    b: InitVar[bool]
    _b: bool = field(init=False)

    def __post_init__(self, b: bool):
        self._b = b

@dataclass
class C(A, B):
    pass

reveal_type(C)  # N: Revealed type is "def (b: builtins.bool, a: builtins.bool) -> __main__.C"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDeepInitVarInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass, field, InitVar
@dataclass
class A:
    a: bool

@dataclass
class B:
    b: InitVar[bool]
    _b: bool = field(init=False)

    def __post_init__(self, b: bool):
        self._b = b

@dataclass(init=False)
class C(B):
    def __init__(self):
        super().__init__(True)

@dataclass
class D(C):
    pass

reveal_type(C)  # N: Revealed type is "def () -> __main__.C"
reveal_type(D)  # N: Revealed type is "def (b: builtins.bool) -> __main__.D"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOverriding]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Mammal:
    age: int

@dataclass
class Person(Mammal):
    name: str
    age: int

@dataclass
class SpecialPerson(Person):
    special_factor: float

@dataclass
class ExtraSpecialPerson(SpecialPerson):
    age: int
    special_factor: float
    name: str

reveal_type(Person)  # N: Revealed type is "def (age: builtins.int, name: builtins.str) -> __main__.Person"
reveal_type(SpecialPerson)  # N: Revealed type is "def (age: builtins.int, name: builtins.str, special_factor: builtins.float) -> __main__.SpecialPerson"
reveal_type(ExtraSpecialPerson)  # N: Revealed type is "def (age: builtins.int, name: builtins.str, special_factor: builtins.float) -> __main__.ExtraSpecialPerson"
Person(32, 'John')
Person(21, 'John', None)  # E: Too many arguments for "Person"
SpecialPerson(21, 'John', 0.5)
ExtraSpecialPerson(21, 'John', 0.5)

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOverridingWithDefaults]
# Issue #5681 https://github.com/python/mypy/issues/5681
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Any

@dataclass
class Base:
    some_int: Any
    some_str: str = 'foo'


@dataclass
class C(Base):
    some_int: int

reveal_type(C)  # N: Revealed type is "def (some_int: builtins.int, some_str: builtins.str =) -> __main__.C"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesFreezing]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass(frozen=True)
class Person:
    name: str

john = Person('John')
john.name = 'Ben'  # E: Property "name" defined in "Person" is read-only

[builtins fixtures/dataclasses.pyi]

[case testDataclassesFields]
# flags: --python-version 3.7
from dataclasses import dataclass, field

@dataclass
class Person:
    name: str
    age: int = field(default=0, init=False)

reveal_type(Person)  # N: Revealed type is "def (name: builtins.str) -> __main__.Person"
john = Person('John')
john.age = 'invalid'  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
john.age = 24

[builtins fixtures/dataclasses.pyi]

[case testDataclassesBadInit]
# flags: --python-version 3.7
from dataclasses import dataclass, field

@dataclass
class Person:
    name: str
    age: int = field(init=None)  # E: No overload variant of "field" matches argument type "None" \
                                 # N: Possible overload variants: \
                                 # N:     def [_T] field(*, default: _T, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T \
                                 # N:     def [_T] field(*, default_factory: Callable[[], _T], init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T \
                                 # N:     def field(*, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> Any

[builtins fixtures/dataclasses.pyi]

[case testDataclassesMultiInit]
# flags: --python-version 3.7
from dataclasses import dataclass, field
from typing import List

@dataclass
class Person:
    name: str
    age: int = field(init=False)
    friend_names: List[str] = field(init=True)
    enemy_names: List[str]

reveal_type(Person)  # N: Revealed type is "def (name: builtins.str, friend_names: builtins.list[builtins.str], enemy_names: builtins.list[builtins.str]) -> __main__.Person"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesMultiInitDefaults]
# flags: --python-version 3.7
from dataclasses import dataclass, field
from typing import List, Optional

@dataclass
class Person:
    name: str
    age: int = field(init=False)
    friend_names: List[str] = field(init=True)
    enemy_names: List[str]
    nickname: Optional[str] = None

reveal_type(Person)  # N: Revealed type is "def (name: builtins.str, friend_names: builtins.list[builtins.str], enemy_names: builtins.list[builtins.str], nickname: Union[builtins.str, None] =) -> __main__.Person"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaults]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int = 0

reveal_type(Application)  # N: Revealed type is "def (name: builtins.str =, rating: builtins.int =) -> __main__.Application"
app = Application()

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaultFactories]
# flags: --python-version 3.7
from dataclasses import dataclass, field

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int = field(default_factory=int)
    rating_count: int = field()  # E: Attributes without a default cannot follow attributes with one

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaultFactoryTypeChecking]
# flags: --python-version 3.7
from dataclasses import dataclass, field

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int = field(default_factory=str)  # E: Incompatible types in assignment (expression has type "str", variable has type "int")

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaultOrdering]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int  # E: Attributes without a default cannot follow attributes with one

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnly]
# flags: --python-version 3.10
from dataclasses import dataclass

@dataclass(kw_only=True)
class Application:
    name: str = 'Unnamed'
    rating: int

Application(rating=5)
Application(name='name', rating=5)
Application()  # E: Missing named argument "rating" for "Application"
Application('name')  # E: Too many positional arguments for "Application" # E: Missing named argument "rating" for "Application"
Application('name', 123)  # E: Too many positional arguments for "Application"
Application('name', rating=123)  # E: Too many positional arguments for "Application"
Application(name=123, rating='name') # E: Argument "name" to "Application" has incompatible type "int"; expected "str" # E: Argument "rating" to "Application" has incompatible type "str"; expected "int"
Application(rating='name', name=123) # E: Argument "rating" to "Application" has incompatible type "str"; expected "int" # E: Argument "name" to "Application" has incompatible type "int"; expected "str"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyOnField]
# flags: --python-version 3.10
from dataclasses import dataclass, field

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int = field(kw_only=True)

Application(rating=5)
Application('name', rating=123)
Application(name='name', rating=5)
Application()  # E: Missing named argument "rating" for "Application"
Application('name')  # E: Missing named argument "rating" for "Application"
Application('name', 123)  # E: Too many positional arguments for "Application"
Application(123, rating='name') # E: Argument 1 to "Application" has incompatible type "int"; expected "str" # E: Argument "rating" to "Application" has incompatible type "str"; expected "int"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyOnFieldFalse]
# flags: --python-version 3.10
from dataclasses import dataclass, field

@dataclass
class Application:
    name: str = 'Unnamed'
    rating: int = field(kw_only=False)  # E: Attributes without a default cannot follow attributes with one

Application(name='name', rating=5)
Application('name', 123)
Application('name', rating=123)
Application()  # E: Missing positional argument "name" in call to "Application"
Application('name')  # E: Too few arguments for "Application"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyWithSentinel]
# flags: --python-version 3.10
from dataclasses import dataclass, KW_ONLY

@dataclass
class Application:
    _: KW_ONLY
    name: str = 'Unnamed'
    rating: int

Application(rating=5)
Application(name='name', rating=5)
Application()  # E: Missing named argument "rating" for "Application"
Application('name')  # E: Too many positional arguments for "Application" # E: Missing named argument "rating" for "Application"
Application('name', 123)  # E: Too many positional arguments for "Application"
Application('name', rating=123)  # E: Too many positional arguments for "Application"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyWithSentinelAndFieldOverride]
# flags: --python-version 3.10
from dataclasses import dataclass, field, KW_ONLY

@dataclass
class Application:
    _: KW_ONLY
    name: str = 'Unnamed'
    rating: int = field(kw_only=False)  # E: Attributes without a default cannot follow attributes with one

Application(name='name', rating=5)
Application()  # E: Missing positional argument "name" in call to "Application"
Application('name')  # E: Too many positional arguments for "Application" # E: Too few arguments for "Application"
Application('name', 123)  # E: Too many positional arguments for "Application"
Application('name', rating=123)  # E: Too many positional arguments for "Application"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyWithSentinelAndSubclass]
# flags: --python-version 3.10
from dataclasses import dataclass, field, KW_ONLY

@dataclass
class Base:
    x: str
    _: KW_ONLY
    y: int = 0
    w: int = 1

@dataclass
class D(Base):
    z: str
    a: str = "a"

D("Hello", "World")
D(x="Hello", z="World")
D("Hello", "World", y=1, w=2, a="b")
D("Hello")  # E: Missing positional argument "z" in call to "D"
D()  # E: Missing positional arguments "x", "z" in call to "D"
D(123, "World")  # E: Argument 1 to "D" has incompatible type "int"; expected "str"
D("Hello", False)  # E: Argument 2 to "D" has incompatible type "bool"; expected "str"
D(123, False)  # E: Argument 1 to "D" has incompatible type "int"; expected "str" # E: Argument 2 to "D" has incompatible type "bool"; expected "str"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOrderingKwOnlyWithMultipleSentinel]
# flags: --python-version 3.10
from dataclasses import dataclass, field, KW_ONLY

@dataclass
class Base:
    x: str
    _: KW_ONLY
    y: int = 0
    __: KW_ONLY  # E: There may not be more than one field with the KW_ONLY type
    w: int = 1

[builtins fixtures/dataclasses.pyi]

[case testDataclassesClassmethods]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class Application:
    name: str

    @classmethod
    def parse(cls, request: str) -> "Application":
        return cls(name='...')

app = Application.parse('')

[builtins fixtures/dataclasses.pyi]

[case testDataclassesOverloadsAndClassmethods]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import overload, Union

@dataclass
class A:
    a: int
    b: str

    @classmethod
    def other(cls) -> str:
        return "..."

    @overload
    @classmethod
    def foo(cls, x: int) -> int: ...

    @overload
    @classmethod
    def foo(cls, x: str) -> str: ...

    @classmethod
    def foo(cls, x: Union[int, str]) -> Union[int, str]:
        reveal_type(cls)            # N: Revealed type is "Type[__main__.A]"
        reveal_type(cls.other())    # N: Revealed type is "builtins.str"
        return x

reveal_type(A.foo(3))      # N: Revealed type is "builtins.int"
reveal_type(A.foo("foo"))  # N: Revealed type is "builtins.str"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesClassVars]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import ClassVar

@dataclass
class Application:
  name: str

  COUNTER: ClassVar[int] = 0

reveal_type(Application)  # N: Revealed type is "def (name: builtins.str) -> __main__.Application"
application = Application("example")
application.COUNTER = 1  # E: Cannot assign to class variable "COUNTER" via instance
Application.COUNTER = 1

[builtins fixtures/dataclasses.pyi]

[case testDataclassOrdering]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass(order=True)
class Application:
  name: str
  rating: int

app1 = Application('example-1', 5)
app2 = Application('example-2', 5)
app1 < app2
app1 > app2
app1 <= app2
app1 >= app2
app1 < 5  # E: Unsupported operand types for < ("Application" and "int")
app1 > 5  # E: Unsupported operand types for > ("Application" and "int")
app1 <= 5  # E: Unsupported operand types for <= ("Application" and "int")
app1 >= 5  # E: Unsupported operand types for >= ("Application" and "int")

class SpecializedApplication(Application):
  ...

app3 = SpecializedApplication('example-3', 5)
app1 < app3
app1 > app3
app1 <= app3
app1 >= app3

[builtins fixtures/dataclasses.pyi]

[case testDataclassOrderingWithoutEquality]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass(eq=False, order=True)
class Application:  # E: eq must be True if order is True
   ...

[builtins fixtures/dataclasses.pyi]

[case testDataclassOrderingWithCustomMethods]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass(order=True)
class Application:
  def __lt__(self, other: 'Application') -> bool: # E: You may not have a custom __lt__ method when order=True
    ...

[builtins fixtures/dataclasses.pyi]

[case testDataclassDefaultsInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Optional

@dataclass(order=True)
class Application:
  id: Optional[int]
  name: str

@dataclass
class SpecializedApplication(Application):
  rating: int = 0

reveal_type(SpecializedApplication)  # N: Revealed type is "def (id: Union[builtins.int, None], name: builtins.str, rating: builtins.int =) -> __main__.SpecializedApplication"

[builtins fixtures/dataclasses.pyi]

[case testDataclassGenerics]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, List, Optional, TypeVar

T = TypeVar('T')

@dataclass
class A(Generic[T]):
  x: T
  y: T
  z: List[T]

  def foo(self) -> List[T]:
    return [self.x, self.y]

  def bar(self) -> T:
    return self.z[0]

  def problem(self) -> T:
    return self.z  # E: Incompatible return value type (got "List[T]", expected "T")

reveal_type(A)  # N: Revealed type is "def [T] (x: T`1, y: T`1, z: builtins.list[T`1]) -> __main__.A[T`1]"
A(1, 2, ["a", "b"])  # E: Cannot infer type argument 1 of "A"
a = A(1, 2, [1, 2])
reveal_type(a)  # N: Revealed type is "__main__.A[builtins.int*]"
reveal_type(a.x)  # N: Revealed type is "builtins.int*"
reveal_type(a.y)  # N: Revealed type is "builtins.int*"
reveal_type(a.z)  # N: Revealed type is "builtins.list[builtins.int*]"
s: str = a.bar()  # E: Incompatible types in assignment (expression has type "int", variable has type "str")

[builtins fixtures/dataclasses.pyi]


[case testDataclassUntypedGenericInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, TypeVar

T = TypeVar("T")

@dataclass
class Base(Generic[T]):
    attr: T

@dataclass
class Sub(Base):
    pass

sub = Sub(attr=1)
reveal_type(sub)  # N: Revealed type is "__main__.Sub"
reveal_type(sub.attr)  # N: Revealed type is "Any"

[builtins fixtures/dataclasses.pyi]

[case testDataclassGenericSubtype]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, TypeVar

T = TypeVar("T")

@dataclass
class Base(Generic[T]):
    attr: T

S = TypeVar("S")

@dataclass
class Sub(Base[S]):
    pass

sub_int = Sub[int](attr=1)
reveal_type(sub_int)  # N: Revealed type is "__main__.Sub[builtins.int*]"
reveal_type(sub_int.attr)  # N: Revealed type is "builtins.int*"

sub_str = Sub[str](attr='ok')
reveal_type(sub_str)  # N: Revealed type is "__main__.Sub[builtins.str*]"
reveal_type(sub_str.attr)  # N: Revealed type is "builtins.str*"

[builtins fixtures/dataclasses.pyi]

[case testDataclassGenericInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, TypeVar

T1 = TypeVar("T1")
T2 = TypeVar("T2")
T3 = TypeVar("T3")

@dataclass
class Base(Generic[T1, T2, T3]):
    one: T1
    two: T2
    three: T3

@dataclass
class Sub(Base[int, str, float]):
    pass

sub = Sub(one=1, two='ok', three=3.14)
reveal_type(sub)  # N: Revealed type is "__main__.Sub"
reveal_type(sub.one)  # N: Revealed type is "builtins.int*"
reveal_type(sub.two)  # N: Revealed type is "builtins.str*"
reveal_type(sub.three)  # N: Revealed type is "builtins.float*"

[builtins fixtures/dataclasses.pyi]

[case testDataclassMultiGenericInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, TypeVar

T = TypeVar("T")

@dataclass
class Base(Generic[T]):
    base_attr: T

S = TypeVar("S")

@dataclass
class Middle(Base[int], Generic[S]):
    middle_attr: S

@dataclass
class Sub(Middle[str]):
    pass

sub = Sub(base_attr=1, middle_attr='ok')
reveal_type(sub)  # N: Revealed type is "__main__.Sub"
reveal_type(sub.base_attr)  # N: Revealed type is "builtins.int*"
reveal_type(sub.middle_attr)  # N: Revealed type is "builtins.str*"

[builtins fixtures/dataclasses.pyi]

[case testDataclassGenericsClassmethod]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Generic, TypeVar

T = TypeVar('T')

@dataclass
class A(Generic[T]):
  x: T

  @classmethod
  def foo(cls) -> None:
      reveal_type(cls)  # N: Revealed type is "Type[__main__.A[T`1]]"
      cls.x  # E: Access to generic instance variables via class is ambiguous

  @classmethod
  def other(cls, x: T) -> A[T]: ...

reveal_type(A(0).other)  # N: Revealed type is "def (x: builtins.int*) -> __main__.A[builtins.int*]"
[builtins fixtures/dataclasses.pyi]

[case testDataclassesForwardRefs]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class A:
  b: 'B'

@dataclass
class B:
  x: int

reveal_type(A)  # N: Revealed type is "def (b: __main__.B) -> __main__.A"
A(b=B(42))
A(b=42)  # E: Argument "b" to "A" has incompatible type "int"; expected "B"

[builtins fixtures/dataclasses.pyi]


[case testDataclassesInitVars]
# flags: --python-version 3.7
from dataclasses import InitVar, dataclass

@dataclass
class Application:
  name: str
  database_name: InitVar[str]

reveal_type(Application)  # N: Revealed type is "def (name: builtins.str, database_name: builtins.str) -> __main__.Application"
app = Application("example", 42)  # E: Argument 2 to "Application" has incompatible type "int"; expected "str"
app = Application("example", "apps")
app.name
app.database_name  # E: "Application" has no attribute "database_name"


@dataclass
class SpecializedApplication(Application):
  rating: int

reveal_type(SpecializedApplication)  # N: Revealed type is "def (name: builtins.str, database_name: builtins.str, rating: builtins.int) -> __main__.SpecializedApplication"
app = SpecializedApplication("example", "apps", "five")  # E: Argument 3 to "SpecializedApplication" has incompatible type "str"; expected "int"
app = SpecializedApplication("example", "apps", 5)
app.name
app.rating
app.database_name  # E: "SpecializedApplication" has no attribute "database_name"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesInitVarsAndDefer]
# flags: --python-version 3.7
from dataclasses import InitVar, dataclass

defer: Yes

@dataclass
class Application:
  name: str
  database_name: InitVar[str]

reveal_type(Application)  # N: Revealed type is "def (name: builtins.str, database_name: builtins.str) -> __main__.Application"
app = Application("example", 42)  # E: Argument 2 to "Application" has incompatible type "int"; expected "str"
app = Application("example", "apps")
app.name
app.database_name  # E: "Application" has no attribute "database_name"

class Yes: ...
[builtins fixtures/dataclasses.pyi]

[case testDataclassesNoInitInitVarInheritance]
# flags: --python-version 3.7
from dataclasses import dataclass, field, InitVar

@dataclass
class Super:
    foo: InitVar = field(init=False)

@dataclass
class Sub(Super):
    bar: int

sub = Sub(5)
sub.foo  # E: "Sub" has no attribute "foo"
sub.bar
[builtins fixtures/dataclasses.pyi]

[case testDataclassFactory]
# flags: --python-version 3.7
from typing import Type, TypeVar
from dataclasses import dataclass

T = TypeVar('T', bound='A')

@dataclass
class A:
    @classmethod
    def make(cls: Type[T]) -> T:
        reveal_type(cls)  # N: Revealed type is "Type[T`-1]"
        reveal_type(cls())  # N: Revealed type is "T`-1"
        return cls()
[builtins fixtures/dataclasses.pyi]

[case testDataclassesInitVarOverride]
# flags: --python-version 3.7
import dataclasses

@dataclasses.dataclass
class A:
    a: dataclasses.InitVar[int]
    _a: int = dataclasses.field(init=False)

    def __post_init__(self, a):
        self._a = a

@dataclasses.dataclass(init=False)
class B(A):
    b: dataclasses.InitVar[int]
    _b: int = dataclasses.field(init=False)

    def __init__(self, b):
        super().__init__(b+1)
        self._b = b

[builtins fixtures/dataclasses.pyi]

[case testDataclassesInitVarNoOverride]
# flags: --python-version 3.7
import dataclasses

@dataclasses.dataclass
class A:
    a: dataclasses.InitVar[int]
    _a: int = dataclasses.field(init=False)

    def __post_init__(self, a):
        self._a = a

@dataclasses.dataclass(init=True)
class B(A):
    b: dataclasses.InitVar[int]
    _b: int = dataclasses.field(init=False)

    def __post_init__(self, a, b):
        self._a = a
        self._b = b

B(1, 2)
B(1, 'a') # E: Argument 2 to "B" has incompatible type "str"; expected "int"

[builtins fixtures/dataclasses.pyi]

[case testDataclassesInitVarPostInitOverride]
# flags: --python-version 3.7
import dataclasses

@dataclasses.dataclass
class A:
    a: dataclasses.InitVar[int]
    _a: int = dataclasses.field(init=False)

    def __post_init__(self, a: int) -> None:
        self._a = a

@dataclasses.dataclass
class B(A):
    b: int = dataclasses.field(init=False)

    def __post_init__(self, a: int) -> None:
        super().__post_init__(a)
        self.b = a + 1

@dataclasses.dataclass(init=False)
class C(B):
    c: int

    def __init__(self, a: int, c: int) -> None:
        super().__init__(a)
        self.c = c + self.b

A(1)
B(1)
B(1, 2)  # E: Too many arguments for "B"
C(1, 2)
C(1, 'a')  # E: Argument 2 to "C" has incompatible type "str"; expected "int"

[builtins fixtures/primitives.pyi]

[case testDataclassesInitVarIncremental]
# flags: --python-version 3.7
import a

[file a.py]
import dataclasses
from b import A

@dataclasses.dataclass
class B(A):
    b: int = dataclasses.field(init=False)

    def __post_init__(self, a: int) -> None:
        super().__post_init__(a)
        self.b = a + 1

[file a.py.2]
import dataclasses
from b import A

@dataclasses.dataclass
class B(A):
    b: int = dataclasses.field(init=False)

    def __post_init__(self, a: int) -> None:
        super().__post_init__(a)
        self.b = a + 2

reveal_type(B)

[file b.py]
import dataclasses

@dataclasses.dataclass
class A:
    a: dataclasses.InitVar[int]
    _a: int = dataclasses.field(init=False)

    def __post_init__(self, a: int) -> None:
        self._a = a
[out2]
tmp/a.py:12: note: Revealed type is "def (a: builtins.int) -> a.B"

[builtins fixtures/primitives.pyi]


[case testNoComplainFieldNone]
# flags: --python-version 3.7
# flags: --no-strict-optional
from dataclasses import dataclass, field
from typing import Optional

@dataclass
class Foo:
    bar: Optional[int] = field(default=None)
[builtins fixtures/dataclasses.pyi]
[out]

[case testNoComplainFieldNoneStrict]
# flags: --python-version 3.7
# flags: --strict-optional
from dataclasses import dataclass, field
from typing import Optional

@dataclass
class Foo:
    bar: Optional[int] = field(default=None)
[builtins fixtures/dataclasses.pyi]
[out]

[case testDisallowUntypedWorksForward]
# flags: --disallow-untyped-defs --python-version 3.7
from dataclasses import dataclass
from typing import List

@dataclass
class B:
    x: C

class C(List[C]):
    pass

reveal_type(B)  # N: Revealed type is "def (x: __main__.C) -> __main__.B"
[builtins fixtures/dataclasses.pyi]

[case testDisallowUntypedWorksForwardBad]
# flags: --disallow-untyped-defs --python-version 3.7
from dataclasses import dataclass

@dataclass
class B:
    x: Undefined  # E: Name "Undefined" is not defined
    y = undefined()  # E: Name "undefined" is not defined

reveal_type(B)  # N: Revealed type is "def (x: Any) -> __main__.B"
[builtins fixtures/dataclasses.pyi]

[case testMemberExprWorksAsField]
# flags: --python-version 3.7
import dataclasses

@dataclasses.dataclass
class A:
    x: int = dataclasses.field(metadata={"doc": "foo"})
    y: str

@dataclasses.dataclass
class B:
    x: int = dataclasses.field(init=False, default=1)
    y: str

@dataclasses.dataclass
class C:
    x: int = dataclasses.field(default=1)
    y: str = dataclasses.field(metadata={"doc": "foo"})  # E: Attributes without a default cannot follow attributes with one
[builtins fixtures/dict.pyi]

[case testDataclassOrderingDeferred]
# flags: --python-version 3.7
from dataclasses import dataclass

defer: Yes

@dataclass(order=True)
class Application:
  name: str
  rating: int

a = Application('', 0)
b = Application('', 0)
a < b

class Yes: ...
[builtins fixtures/dataclasses.pyi]

[case testDataclassFieldDeferred]
# flags: --python-version 3.7
from dataclasses import field, dataclass

@dataclass
class C:
    x: int = field(default=func())

def func() -> int: ...
C('no')  # E: Argument 1 to "C" has incompatible type "str"; expected "int"
[builtins fixtures/dataclasses.pyi]

[case testDataclassFieldDeferredFrozen]
# flags: --python-version 3.7
from dataclasses import field, dataclass

@dataclass(frozen=True)
class C:
    x: int = field(default=func())

def func() -> int: ...
c: C
c.x = 1  # E: Property "x" defined in "C" is read-only
[builtins fixtures/dataclasses.pyi]

[case testTypeInDataclassDeferredStar]
# flags: --python-version 3.7
import lib
[file lib.py]
from dataclasses import dataclass
MYPY = False
if MYPY:  # Force deferral
    from other import *

@dataclass
class C:
    total: int

C()  # E: Missing positional argument "total" in call to "C"
C('no')  # E: Argument 1 to "C" has incompatible type "str"; expected "int"
[file other.py]
import lib
[builtins fixtures/dataclasses.pyi]

[case testDeferredDataclassInitSignature]
# flags: --python-version 3.7 --no-strict-optional
from dataclasses import dataclass
from typing import Optional, Type

@dataclass
class C:
    x: Optional[int] = None
    y: Type[Deferred] = Deferred

    @classmethod
    def default(cls) -> C:
        return cls(x=None, y=None)

class Deferred: pass
[builtins fixtures/dataclasses.pyi]

[case testDeferredDataclassInitSignatureSubclass]
# flags: --strict-optional --python-version 3.7
from dataclasses import dataclass
from typing import Optional

@dataclass
class B:
    x: Optional[C]

@dataclass
class C(B):
    y: str

a = C(None, 'abc')
[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaultsIncremental]
# flags: --python-version 3.7
import a

[file a.py]
from dataclasses import dataclass
from b import Person

@dataclass
class Asdf(Person):
    c: str = 'test'

[file a.py.2]
from dataclasses import dataclass
from b import Person

@dataclass
class Asdf(Person):
    c: str = 'test'

# asdf

[file b.py]
from dataclasses import dataclass

@dataclass
class Person:
    b: int
    a: str = 'test'

[builtins fixtures/dataclasses.pyi]

[case testDataclassesDefaultsMroOtherFile]
# flags: --python-version 3.7
import a

[file a.py]
from dataclasses import dataclass
from b import A1, A2

@dataclass
class Asdf(A1, A2):  # E: Attributes without a default cannot follow attributes with one
    pass

[file b.py]
from dataclasses import dataclass

# a bunch of blank lines to make sure the error doesn't accidentally line up...



@dataclass
class A1:
    a: int

@dataclass
class A2:
    b: str = 'test'

[builtins fixtures/dataclasses.pyi]

[case testDataclassesInheritingDuplicateField]
# flags: --python-version 3.7
# see mypy issue #7792
from dataclasses import dataclass

@dataclass
class A:  # E: Name "x" already defined (possibly by an import)
    x: int = 0
    x: int = 0  # E: Name "x" already defined on line 7

@dataclass
class B(A):
    pass

[builtins fixtures/dataclasses.pyi]

[case testDataclassInheritanceNoAnnotation]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class A:
    foo: int

x = 0
@dataclass
class B(A):
    foo = x

reveal_type(B)  # N: Revealed type is "def (foo: builtins.int) -> __main__.B"

[builtins fixtures/dataclasses.pyi]

[case testDataclassInheritanceNoAnnotation2]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass(frozen=True)
class A:
    foo: int

@dataclass
class B(A):
    @property
    def foo(self) -> int: pass  # E: Signature of "foo" incompatible with supertype "A"

reveal_type(B)  # N: Revealed type is "def (foo: builtins.int) -> __main__.B"

[builtins fixtures/dataclasses.pyi]

[case testDataclassHasAttributeWithFields]
# flags: --python-version 3.7
from dataclasses import dataclass

@dataclass
class A:
    pass

reveal_type(A.__dataclass_fields__)  # N: Revealed type is "builtins.dict[builtins.str, dataclasses.Field[Any]]"

[builtins fixtures/dict.pyi]

[case testDataclassCallableProperty]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Callable

@dataclass
class A:
    foo: Callable[[int], int]

def my_foo(x: int) -> int:
    return x

a = A(foo=my_foo)
a.foo(1)
reveal_type(a.foo)  # N: Revealed type is "def (builtins.int) -> builtins.int"
reveal_type(A.foo)  # N: Revealed type is "def (builtins.int) -> builtins.int"
[typing fixtures/typing-medium.pyi]
[builtins fixtures/dataclasses.pyi]

[case testDataclassCallableAssignment]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Callable

@dataclass
class A:
    foo: Callable[[int], int]

def my_foo(x: int) -> int:
    return x

a = A(foo=my_foo)

def another_foo(x: int) -> int:
    return x

a.foo = another_foo
[builtins fixtures/dataclasses.pyi]

[case testDataclassCallablePropertyWrongType]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Callable

@dataclass
class A:
    foo: Callable[[int], int]

def my_foo(x: int) -> str:
    return "foo"

a = A(foo=my_foo)  # E: Argument "foo" to "A" has incompatible type "Callable[[int], str]"; expected "Callable[[int], int]"
[typing fixtures/typing-medium.pyi]
[builtins fixtures/dataclasses.pyi]

[case testDataclassCallablePropertyWrongTypeAssignment]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Callable

@dataclass
class A:
    foo: Callable[[int], int]

def my_foo(x: int) -> int:
    return x

a = A(foo=my_foo)

def another_foo(x: int) -> str:
    return "foo"

a.foo = another_foo  # E: Incompatible types in assignment (expression has type "Callable[[int], str]", variable has type "Callable[[int], int]")
[typing fixtures/typing-medium.pyi]
[builtins fixtures/dataclasses.pyi]

[case testDataclassFieldDoesNotFailOnKwargsUnpacking]
# flags: --python-version 3.7
# https://github.com/python/mypy/issues/10879
from dataclasses import dataclass, field

@dataclass
class Foo:
    bar: float = field(**{"repr": False})
[out]
main:7: error: Unpacking **kwargs in "field()" is not supported
main:7: error: No overload variant of "field" matches argument type "Dict[str, bool]"
main:7: note: Possible overload variants:
main:7: note:     def [_T] field(*, default: _T, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T
main:7: note:     def [_T] field(*, default_factory: Callable[[], _T], init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T
main:7: note:     def field(*, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> Any
[builtins fixtures/dataclasses.pyi]

[case testDataclassFieldWithPositionalArguments]
# flags: --python-version 3.7
from dataclasses import dataclass, field

@dataclass
class C:
    x: int = field(0)  # E: "field()" does not accept positional arguments \
                       # E: No overload variant of "field" matches argument type "int" \
                       # N: Possible overload variants: \
                       # N:     def [_T] field(*, default: _T, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T \
                       # N:     def [_T] field(*, default_factory: Callable[[], _T], init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T \
                       # N:     def field(*, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> Any
[builtins fixtures/dataclasses.pyi]

[case testDataclassFieldWithTypedDictUnpacking]
# flags: --python-version 3.7
from dataclasses import dataclass, field
from typing_extensions import TypedDict

class FieldKwargs(TypedDict):
    repr: bool

field_kwargs: FieldKwargs = {"repr": False}

@dataclass
class Foo:
    bar: float = field(**field_kwargs)  # E: Unpacking **kwargs in "field()" is not supported

reveal_type(Foo(bar=1.5))  # N: Revealed type is "__main__.Foo"
[builtins fixtures/dataclasses.pyi]

[case testDataclassWithSlotsArg]
# flags: --python-version 3.10
from dataclasses import dataclass

@dataclass(slots=True)
class Some:
    x: int

    def __init__(self, x: int) -> None:
        self.x = x
        self.y = 0  # E: Trying to assign name "y" that is not in "__slots__" of type "__main__.Some"

    def __post_init__(self) -> None:
        self.y = 1  # E: Trying to assign name "y" that is not in "__slots__" of type "__main__.Some"
[builtins fixtures/dataclasses.pyi]

[case testDataclassWithSlotsDef]
# flags: --python-version 3.10
from dataclasses import dataclass

@dataclass(slots=False)
class Some:
    __slots__ = ('x',)
    x: int

    def __init__(self, x: int) -> None:
        self.x = x
        self.y = 0  # E: Trying to assign name "y" that is not in "__slots__" of type "__main__.Some"

    def __post_init__(self) -> None:
        self.y = 1  # E: Trying to assign name "y" that is not in "__slots__" of type "__main__.Some"
[builtins fixtures/dataclasses.pyi]

[case testDataclassWithSlotsConflict]
# flags: --python-version 3.10
from dataclasses import dataclass

@dataclass(slots=True)
class Some:  # E: "Some" both defines "__slots__" and is used with "slots=True"
    __slots__ = ('x',)
    x: int

@dataclass(slots=True)
class EmptyDef:  # E: "EmptyDef" both defines "__slots__" and is used with "slots=True"
    __slots__ = ()
    x: int

slots = ('x',)

@dataclass(slots=True)
class DynamicDef:  # E: "DynamicDef" both defines "__slots__" and is used with "slots=True"
    __slots__ = slots
    x: int
[builtins fixtures/dataclasses.pyi]

[case testDataclassWithSlotsArgBefore310]
# flags: --python-version 3.9
from dataclasses import dataclass

@dataclass(slots=True)  # E: Keyword argument "slots" for "dataclass" is only valid in Python 3.10 and higher
class Some:
    x: int

# Possible conflict:
@dataclass(slots=True)  # E: Keyword argument "slots" for "dataclass" is only valid in Python 3.10 and higher
class Other:
    __slots__ = ('x',)
    x: int
[builtins fixtures/dataclasses.pyi]


[case testSlotsDefinitionWithTwoPasses1]
# flags: --python-version 3.10
# https://github.com/python/mypy/issues/11821
from typing import TypeVar, Protocol, Generic
from dataclasses import dataclass

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

class Comparable(Protocol):
    pass

V = TypeVar("V", bound=Comparable)

@dataclass(slots=True)
class Node(Generic[V]):  # Error was here
    data: V
[builtins fixtures/dataclasses.pyi]

[case testSlotsDefinitionWithTwoPasses2]
# flags: --python-version 3.10
from typing import TypeVar, Protocol, Generic
from dataclasses import dataclass

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

class Comparable(Protocol):
    pass

V = TypeVar("V", bound=Comparable)

@dataclass(slots=True)  # Explicit slots are still not ok:
class Node(Generic[V]):  # E: "Node" both defines "__slots__" and is used with "slots=True"
    __slots__ = ('data',)
    data: V
[builtins fixtures/dataclasses.pyi]

[case testSlotsDefinitionWithTwoPasses3]
# flags: --python-version 3.10
from typing import TypeVar, Protocol, Generic
from dataclasses import dataclass

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

class Comparable(Protocol):
    pass

V = TypeVar("V", bound=Comparable)

@dataclass(slots=True)  # Explicit slots are still not ok, even empty ones:
class Node(Generic[V]):  # E: "Node" both defines "__slots__" and is used with "slots=True"
    __slots__ = ()
    data: V
[builtins fixtures/dataclasses.pyi]

[case testSlotsDefinitionWithTwoPasses4]
# flags: --python-version 3.10
import dataclasses as dtc

PublishedMessagesVar = dict[int, 'PublishedMessages']

@dtc.dataclass(frozen=True, slots=True)
class PublishedMessages:
    left: int
[builtins fixtures/dataclasses.pyi]

[case testDataclassesAnyInherit]
# flags: --python-version 3.7
from dataclasses import dataclass
from typing import Any
B: Any
@dataclass
class A(B):
    a: int

A(a=1, b=2)
A(1)
A(a="foo")  # E: Argument "a" to "A" has incompatible type "str"; expected "int"
[builtins fixtures/dataclasses.pyi]