test-data/unit/check-abstract.test

-- Type checker test cases for abstract classes.


-- Subtyping with abstract classes
-- -------------------------------


[case testAbstractClassSubclasses]

from abc import abstractmethod, ABCMeta

i: I
j: J
a: A
b: B
c: C

def f(): i, j, a, b, c # Prevent redefinition

j = c  # E: Incompatible types in assignment (expression has type "C", variable has type "J")
a = i  # E: Incompatible types in assignment (expression has type "I", variable has type "A")
a = j  # E: Incompatible types in assignment (expression has type "J", variable has type "A")
b = i  # E: Incompatible types in assignment (expression has type "I", variable has type "B")

i = a
i = b
i = c
j = a
j = b
a = b

class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self): pass
class J(metaclass=ABCMeta):
    @abstractmethod
    def g(self): pass
class A(I, J): pass
class B(A): pass
class C(I): pass
[builtins fixtures/tuple.pyi]

[case testAbstractClassSubtypingViaExtension]

from abc import abstractmethod, ABCMeta

i: I
j: J
a: A
o: object

def f(): i, j, a, o # Prevent redefinition

j = i # E: Incompatible types in assignment (expression has type "I", variable has type "J")
a = i # E: Incompatible types in assignment (expression has type "I", variable has type "A")
a = j # E: Incompatible types in assignment (expression has type "J", variable has type "A")
i = o # E: Incompatible types in assignment (expression has type "object", variable has type "I")
j = o # E: Incompatible types in assignment (expression has type "object", variable has type "J")

i = a
j = a
i = j
o = i
o = j

class I(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
class J(I): pass
class A(J): pass
[builtins fixtures/tuple.pyi]

[case testInheritingAbstractClassInSubclass]
from abc import abstractmethod, ABCMeta

i: I
a: A
b: B

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

if int():
    a = b
if int():
    i = b

class I(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
class A: pass
class B(A, I): pass


-- Abstract class objects
-- ----------------------


[case testAbstractClassAsTypeObject]

from abc import abstractmethod, ABCMeta

class I(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass

o: object
t: type

o = I
t = I

[case testAbstractClassInCasts]
from typing import cast
from abc import abstractmethod, ABCMeta

class I(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
class A(I): pass
class B: pass

i: I
a: A
b: B
o: object

if int():
    a = cast(I, o) # E: Incompatible types in assignment (expression has type "I", variable has type "A")
if int():
    b = cast(B, i) # Ok; a subclass of B might inherit I
if int():
    i = cast(I, b) # Ok; a subclass of B might inherit I

if int():
    i = cast(I, o)
if int():
    i = cast(I, a)
[builtins fixtures/tuple.pyi]

[case testInstantiatingClassThatImplementsAbstractMethod]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
class B(A):
  def f(self): pass
B()
[out]

[case testInstantiatingAbstractClass]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta): pass
class B(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
A() # OK
B() # E: Cannot instantiate abstract class "B" with abstract attribute "f"
[out]

[case testInstantiatingClassWithInheritedAbstractMethod]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta):
  @abstractmethod
  def f(self): pass
  @abstractmethod
  def g(self): pass
class B(A): pass
B() # E: Cannot instantiate abstract class "B" with abstract attributes "f" and "g"
[out]

[case testInstantiationAbstractsInTypeForFunctions]
from typing import Type
from abc import abstractmethod

class A:
    @abstractmethod
    def m(self) -> None: pass
class B(A): pass
class C(B):
    def m(self) -> None:
        pass

def f(cls: Type[A]) -> A:
    return cls()  # OK
def g() -> A:
    return A()  # E: Cannot instantiate abstract class "A" with abstract attribute "m"

f(A)  # E: Only concrete class can be given where "type[A]" is expected
f(B)  # E: Only concrete class can be given where "type[A]" is expected
f(C)  # OK
x: Type[B]
f(x)  # OK
[out]

[case testAbstractTypeInADict]
from typing import Dict, Type
from abc import abstractmethod

class Class:
    @abstractmethod
    def method(self) -> None:
        pass

my_dict_init: Dict[int, Type[Class]] = {0: Class}  # E: Only concrete class can be given where "tuple[int, type[Class]]" is expected

class Child(Class):
    def method(self) -> None: ...

other_dict_init: Dict[int, Type[Class]] = {0: Child}  # ok
[builtins fixtures/dict.pyi]
[out]

[case testInstantiationAbstractsInTypeForAliases]
from typing import Type
from abc import abstractmethod

class A:
    @abstractmethod
    def m(self) -> None: pass
class B(A): pass
class C(B):
    def m(self) -> None:
        pass

def f(cls: Type[A]) -> A:
    return cls()  # OK

Alias = A
GoodAlias = C
Alias()  # E: Cannot instantiate abstract class "A" with abstract attribute "m"
GoodAlias()
f(Alias)  # E: Only concrete class can be given where "type[A]" is expected
f(GoodAlias)
[out]

[case testInstantiationAbstractsInTypeForVariables]
# flags: --no-strict-optional
from typing import Type, overload
from abc import abstractmethod

class A:
    @abstractmethod
    def m(self) -> None: pass
class B(A): pass
class C(B):
    def m(self) -> None:
        pass

var: Type[A]
var()
if int():
    var = A # E: Can only assign concrete classes to a variable of type "type[A]"
if int():
    var = B # E: Can only assign concrete classes to a variable of type "type[A]"
if int():
    var = C # OK

var_old = None # type: Type[A] # Old syntax for variable annotations
var_old()
if int():
    var_old = A # E: Can only assign concrete classes to a variable of type "type[A]"
if int():
    var_old = B # E: Can only assign concrete classes to a variable of type "type[A]"
if int():
    var_old = C # OK

class D(A):
    @overload
    def __new__(cls, a) -> "D": ...
    @overload
    def __new__(cls) -> "D": ...
    def __new__(cls, a=None) -> "D": ...
if int():
    var = D # E: Can only assign concrete classes to a variable of type "type[A]"
[out]

[case testInstantiationAbstractsInTypeForClassMethods]
from typing import Type
from abc import abstractmethod

class Logger:
    @staticmethod
    def log(a: Type[C]):
        pass
class C:
    @classmethod
    def action(cls) -> None:
        cls() #OK for classmethods
        Logger.log(cls)  #OK for classmethods
    @abstractmethod
    def m(self) -> None:
        pass
[builtins fixtures/classmethod.pyi]
[out]

[case testInstantiatingClassWithInheritedAbstractMethodAndSuppression]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta):
    @abstractmethod
    def a(self): pass
    @abstractmethod
    def b(self): pass
    @abstractmethod
    def c(self): pass
    @abstractmethod
    def d(self): pass
    @abstractmethod
    def e(self): pass
    @abstractmethod
    def f(self): pass
    @abstractmethod
    def g(self): pass
    @abstractmethod
    def h(self): pass
    @abstractmethod
    def i(self): pass
    @abstractmethod
    def j(self): pass
a = A() # E: Cannot instantiate abstract class "A" with abstract attributes "a", "b", ... and "j" (7 methods suppressed)
[out]


-- Implementing abstract methods
-- -----------------------------


[case testImplementingAbstractMethod]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x: int) -> int: pass
    @abstractmethod
    def g(self, x: int) -> int: pass
class B(A):
    def f(self, x: str) -> int: \
            # 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
        return 0
    def g(self, x: int) -> int: return 0
[out]

[case testImplementingAbstractMethodWithMultipleBaseClasses]
from abc import abstractmethod, ABCMeta
import typing
class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x: int) -> int: pass
class J(metaclass=ABCMeta):
    @abstractmethod
    def g(self, x: str) -> str: pass
class A(I, J):
    def f(self, x: str) -> int: return 0 \
        # E: Argument 1 of "f" is incompatible with supertype "I"; 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) -> int: return 0 \
        # E: Return type "int" of "g" incompatible with return type "str" in supertype "J"
    def h(self) -> int: return 0 # Not related to any base class
[out]

[case testImplementingAbstractMethodWithExtension]
from abc import abstractmethod, ABCMeta
import typing
class J(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x: int) -> int: pass
class I(J): pass
class A(I):
    def f(self, x: str) -> int: return 0 \
        # E: Argument 1 of "f" is incompatible with supertype "J"; 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
[out]

[case testInvalidOverridingAbstractMethod]
from abc import abstractmethod, ABCMeta
import typing
class J(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x: 'J') -> None: pass
class I(J):
    @abstractmethod
    def f(self, x: 'I') -> None: pass # E: Argument 1 of "f" is incompatible with supertype "J"; supertype defines the argument type as "J" \
                                      # N: This violates the Liskov substitution principle \
                                      # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
[out]

[case testAbstractClassCoAndContraVariance]
from abc import abstractmethod, ABCMeta
import typing
class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, a: A) -> 'I': pass
    @abstractmethod
    def g(self, a: A) -> 'I': pass
    @abstractmethod
    def h(self, a: 'I') -> A: pass
class A(I):
    def h(self, a: 'A') -> 'I': # Fail
        return A()
    def f(self, a: 'I') -> 'I':
        return A()
    def g(self, a: 'A') -> 'A':
        return A()
[out]
main:11: error: Return type "I" of "h" incompatible with return type "A" in supertype "I"
main:11: error: Argument 1 of "h" is incompatible with supertype "I"; supertype defines the argument type as "I"
main:11: note: This violates the Liskov substitution principle
main:11: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides


-- Accessing abstract members
-- --------------------------


[case testAccessingAbstractMethod]
from abc import abstractmethod, ABCMeta

class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, a: int) -> str: pass

i: I
a: int
b: str

if int():
    a = i.f(a) # E: Incompatible types in assignment (expression has type "str", variable has type "int")
if int():
    b = i.f(b) # E: Argument 1 to "f" of "I" has incompatible type "str"; expected "int"
i.g()      # E: "I" has no attribute "g"

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

[case testAccessingInheritedAbstractMethod]
from abc import abstractmethod, ABCMeta

class J(metaclass=ABCMeta):
    @abstractmethod
    def f(self, a: int) -> str: pass
class I(J): pass

i: I
a: int
b: str

if int():
    a = i.f(1) # E: Incompatible types in assignment (expression has type "str", variable has type "int")
if int():
    b = i.f(1)


-- Any (dynamic) types
-- -------------------
[builtins fixtures/tuple.pyi]


[case testAbstractClassWithAllDynamicTypes]
from abc import abstractmethod, ABCMeta
import typing
class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x): pass
    @abstractmethod
    def g(self, x): pass
class A(I):
    def f(self, x): pass
    def g(self, x, y) -> None: pass  # Fail
[out]
main:10: error: Signature of "g" incompatible with supertype "I"
main:10: note:      Superclass:
main:10: note:          def g(self, x: Any) -> Any
main:10: note:      Subclass:
main:10: note:          def g(self, x: Any, y: Any) -> None

[case testAbstractClassWithAllDynamicTypes2]
from abc import abstractmethod, ABCMeta
import typing
class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x): pass
    @abstractmethod
    def g(self, x): pass
class A(I):
    def f(self, x): pass
    def g(self, x, y): pass
[out]

[case testAbstractClassWithImplementationUsingDynamicTypes]
from abc import abstractmethod, ABCMeta
import typing
class I(metaclass=ABCMeta):
    @abstractmethod
    def f(self, x: int) -> None: pass
    @abstractmethod
    def g(self, x: int) -> None: pass
class A(I):
    def f(self, x): pass
    def g(self, x, y): pass
[out]


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


[case testMultipleAbstractBases]
from abc import abstractmethod, ABCMeta
import typing
class A(metaclass=ABCMeta):
  @abstractmethod
  def f(self) -> None: pass
class B(metaclass=ABCMeta):
  @abstractmethod
  def g(self) -> None: pass
class C(A, B):
  @abstractmethod
  def h(self) -> None: pass

[case testMemberAccessWithMultipleAbstractBaseClasses]

from abc import abstractmethod, ABCMeta

class A(metaclass=ABCMeta):
    @abstractmethod
    def f(self) -> None: pass
class B(metaclass=ABCMeta):
    @abstractmethod
    def g(self) -> None: pass
class C(A, B): pass
x: C
x.f()
x.g()
x.f(x) # E: Too many arguments for "f" of "A"
x.g(x) # E: Too many arguments for "g" of "B"

[case testInstantiatingAbstractClassWithMultipleBaseClasses]

from abc import abstractmethod, ABCMeta

class A(metaclass=ABCMeta):
  @abstractmethod
  def f(self) -> None: pass
class B(metaclass=ABCMeta):
  @abstractmethod
  def g(self) -> None: pass
class C(A, B):
  def f(self) -> None: pass
class D(A, B):
  def g(self) -> None: pass
class E(A, B):
  def f(self) -> None: pass
  def g(self) -> None: pass
C() # E: Cannot instantiate abstract class "C" with abstract attribute "g"
D() # E: Cannot instantiate abstract class "D" with abstract attribute "f"
E()

[case testInconsistentMro]
from abc import abstractmethod, ABCMeta
import typing

class A(metaclass=ABCMeta): pass
class B(object, A, metaclass=ABCMeta): # E: Cannot determine consistent method resolution order (MRO) for "B"
    pass

class C(object, A):  # E: Cannot determine consistent method resolution order (MRO) for "C" \
                     # E: Metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases
    pass

[case testOverloadedAbstractMethod]
from foo import *
[file foo.pyi]
from abc import abstractmethod, ABCMeta
from typing import overload

class A(metaclass=ABCMeta):
  @abstractmethod
  @overload
  def f(self, x: int) -> int: pass
  @abstractmethod
  @overload
  def f(self, x: str) -> str: pass

class B(A):
  @overload
  def f(self, x: int) -> int: pass
  @overload
  def f(self, x: str) -> str: pass
A() # E: Cannot instantiate abstract class "A" with abstract attribute "f"
B()
B().f(1)
a = B() # type: A
a.f(1)
a.f('')
a.f(B()) # E: No overload variant of "f" of "A" matches argument type "B" \
         # N: Possible overload variants: \
         # N:     def f(self, x: int) -> int \
         # N:     def f(self, x: str) -> str

[case testOverloadedAbstractMethodWithAlternativeDecoratorOrder]
from foo import *
[file foo.pyi]
from abc import abstractmethod, ABCMeta
from typing import overload

class A(metaclass=ABCMeta):
  @overload
  @abstractmethod
  def f(self, x: int) -> int: pass
  @overload
  @abstractmethod
  def f(self, x: str) -> str: pass

class B(A):
  @overload
  def f(self, x: int) -> int: pass
  @overload
  def f(self, x: str) -> str: pass
A() # E: Cannot instantiate abstract class "A" with abstract attribute "f"
B()
B().f(1)
a = B() # type: A
a.f(1)
a.f('')
a.f(B()) # E: No overload variant of "f" of "A" matches argument type "B" \
         # N: Possible overload variants: \
         # N:     def f(self, x: int) -> int \
         # N:     def f(self, x: str) -> str

[case testOverloadedAbstractMethodVariantMissingDecorator0]
from foo import *
[file foo.pyi]
from abc import abstractmethod, ABCMeta
from typing import overload

class A(metaclass=ABCMeta):
  @abstractmethod \
    # E: Overloaded method has both abstract and non-abstract variants
  @overload
  def f(self, x: int) -> int: pass
  @overload
  def f(self, x: str) -> str: pass
[out]

[case testOverloadedAbstractMethodVariantMissingDecorator1]
from foo import *
[file foo.pyi]
from abc import abstractmethod, ABCMeta
from typing import overload

class A(metaclass=ABCMeta):
  @overload \
    # E: Overloaded method has both abstract and non-abstract variants
  def f(self, x: int) -> int: pass
  @abstractmethod
  @overload
  def f(self, x: str) -> str: pass
[out]

[case testMultipleInheritanceAndAbstractMethod]
import typing
from abc import abstractmethod, ABCMeta
class A:
  def f(self, x: str) -> None: pass
class B(metaclass=ABCMeta):
  @abstractmethod
  def f(self, x: str) -> None: pass
class C(A, B): pass

[case testMultipleInheritanceAndAbstractMethod2]
import typing
from abc import abstractmethod, ABCMeta
class A:
  def f(self, x: str) -> None: pass
class B(metaclass=ABCMeta):
  @abstractmethod
  def f(self, x: int) -> None: pass
class C(A, B): pass
[out]
main:8: error: Definition of "f" in base class "A" is incompatible with definition in base class "B"

[case testCallAbstractMethodBeforeDefinition]
import typing
from abc import abstractmethod, ABCMeta
class A(metaclass=ABCMeta):
    def f(self) -> None:
        self.g(1) # E: Argument 1 to "g" of "A" has incompatible type "int"; expected "str"
    @abstractmethod
    def g(self, x: str) -> None: pass
[out]

[case testAbstractOperatorMethods1]
import typing
from abc import abstractmethod, ABCMeta
class A(metaclass=ABCMeta):
    @abstractmethod
    def __lt__(self, other: 'A') -> int: pass
    @abstractmethod
    def __gt__(self, other: 'A') -> int: pass

[case testAbstractOperatorMethods2]
from typing import cast, Any
from abc import abstractmethod, ABCMeta
class A(metaclass=ABCMeta):
    @abstractmethod
    def __radd__(self, other: 'C') -> str: pass # Error
class B:
    @abstractmethod
    def __add__(self, other: 'A') -> int: pass
class C:
    def __add__(self, other: int) -> B:
        return cast(Any, None)
[out]

[case testAbstractClassWithAnyBase]
from typing import Any
from abc import abstractmethod, ABCMeta

A: Any

class D(metaclass=ABCMeta):
    @abstractmethod
    def f(self) -> None: pass

class C(A, D):
    pass

C()  # A might implement 'f'


-- Abstract properties
-- -------------------


[case testReadOnlyAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
def f(a: A) -> None:
    a.x() # E: "int" not callable
    a.x = 1  # E: Property "x" defined in "A" is read-only
[out]

[case testReadOnlyAbstractPropertyForwardRef]
from abc import abstractproperty, ABCMeta
def f(a: A) -> None:
    a.x() # E: "int" not callable
    a.x = 1  # E: Property "x" defined in "A" is read-only
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
[out]

[case testReadWriteAbstractProperty]
from abc import abstractproperty, ABCMeta
def f(a: A) -> None:
    a.x.y # E: "int" has no attribute "y"
    a.x = 1
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
    @x.setter
    def x(self, x: int) -> None: pass

[case testReadWriteDeleteAbstractProperty]
# flags: --no-strict-optional
from abc import ABC, abstractmethod
class Abstract(ABC):
    @property
    @abstractmethod
    def prop(self) -> str: ...

    @prop.setter
    @abstractmethod
    def prop(self, code: str) -> None: ...

    @prop.deleter
    @abstractmethod
    def prop(self) -> None: ...

class Good(Abstract):
    @property
    def prop(self) -> str: ...
    @prop.setter
    def prop(self, code: str) -> None: ...
    @prop.deleter
    def prop(self) -> None: ...

class Bad1(Abstract):
    @property  # E: Read-only property cannot override read-write property
    def prop(self) -> str: ...

class ThisShouldProbablyError(Abstract):
    @property
    def prop(self) -> str: ...
    @prop.setter
    def prop(self, code: str) -> None: ...

a = Good()
reveal_type(a.prop)  # N: Revealed type is "builtins.str"
a.prop = 123  # E: Incompatible types in assignment (expression has type "int", variable has type "str")
[builtins fixtures/property.pyi]

[case testInstantiateClassWithReadOnlyAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
class B(A): pass
b = B() # E: Cannot instantiate abstract class "B" with abstract attribute "x"

[case testInstantiateClassWithReadWriteAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
    @x.setter
    def x(self, x: int) -> None: pass
class B(A): pass
b = B() # E: Cannot instantiate abstract class "B" with abstract attribute "x"

[case testImplementAbstractPropertyViaProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
class B(A):
    @property
    def x(self) -> int: return 0
b = B()
b.x() # E: "int" not callable
[builtins fixtures/property.pyi]

[case testImplementReadWriteAbstractPropertyViaProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
    @x.setter
    def x(self, v: int) -> None: pass
class B(A):
    @property
    def x(self) -> int: return 0
    @x.setter
    def x(self, v: int) -> None: pass
b = B()
b.x.y # E: "int" has no attribute "y"
[builtins fixtures/property.pyi]

[case testImplementAbstractPropertyViaPropertyInvalidType]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
class B(A):
    @property
    def x(self) -> str: return "no" # E: Signature of "x" incompatible with supertype "A" \
                                    # N:      Superclass: \
                                    # N:          int \
                                    # N:      Subclass: \
                                    # N:          str
b = B()
b.x() # E: "str" not callable
[builtins fixtures/property.pyi]

[case testCantImplementAbstractPropertyViaInstanceVariable]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
class B(A):
    def __init__(self) -> None:
        self.x = 1 # E
b = B() # E
b.x.y # E
[builtins fixtures/property.pyi]
[out]
main:7: error: Property "x" defined in "A" is read-only
main:8: error: Cannot instantiate abstract class "B" with abstract attribute "x"
main:9: error: "int" has no attribute "y"

[case testSuperWithAbstractProperty]
# flags: --no-strict-optional
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
class B(A):
    @property
    def x(self) -> int:
        return super().x.y  # E: Call to abstract method "x" of "A" with trivial body via super() is unsafe \
                            # E: "int" has no attribute "y"
[builtins fixtures/property.pyi]

[case testSuperWithReadWriteAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
    @x.setter
    def x(self, v: int) -> None: pass
class B(A):
    @property
    def x(self) -> int:
        return super().x.y # E
    @x.setter
    def x(self, v: int) -> None:
        super().x = '' # E
[builtins fixtures/property.pyi]
[out]
main:10: error: "int" has no attribute "y"
main:13: error: Invalid assignment target

[case testOnlyImplementGetterOfReadWriteAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self) -> int: pass
    @x.setter
    def x(self, v: int) -> None: pass
class B(A):
    @property # E
    def x(self) -> int: return 0
b = B()
b.x.y # E
[builtins fixtures/property.pyi]
[out]
main:8: error: Read-only property cannot override read-write property
main:11: error: "int" has no attribute "y"

[case testDynamicallyTypedReadOnlyAbstractProperty]
from abc import abstractproperty, ABCMeta
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self): pass
def f(a: A) -> None:
    a.x.y
    a.x = 1  # E: Property "x" defined in "A" is read-only
[out]

[case testDynamicallyTypedReadOnlyAbstractPropertyForwardRef]
from abc import abstractproperty, ABCMeta
def f(a: A) -> None:
    a.x.y
    a.x = 1  # E: Property "x" defined in "A" is read-only
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self): pass
[out]

[case testDynamicallyTypedReadWriteAbstractProperty]
from abc import abstractproperty, ABCMeta
def f(a: A) -> None:
    a.x.y
    a.x = 1
class A(metaclass=ABCMeta):
    @abstractproperty
    def x(self): pass
    @x.setter
    def x(self, x): pass
[out]

[case testMixinTypedAbstractProperty]
from abc import ABCMeta, abstractproperty
class A(metaclass=ABCMeta):
    @abstractproperty
    def foo(cls) -> str:
        pass
class Mixin:
    foo = "foo"
class C(Mixin, A):
    pass
[out]

[case testMixinTypedProperty]
class A:
    @property
    def foo(cls) -> str:
        return "yes"
class Mixin:
    foo = "foo"
class C(Mixin, A):
    pass
[builtins fixtures/property.pyi]

[case testMixinSubtypedProperty]
class X:
    pass
class Y(X):
    pass
class A:
    @property
    def foo(cls) -> X:
        return X()
class Mixin:
    foo = Y()
class C(Mixin, A):
    pass
[builtins fixtures/property.pyi]

[case testMixinTypedPropertyReversed]
class A:
    @property
    def foo(cls) -> str:
        return "no"
class Mixin:
    foo = "foo"
class C(A, Mixin): # E: Cannot override writeable attribute "foo" in base "Mixin" with read-only property in base "A"
    pass
[builtins fixtures/property.pyi]

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


[case testNestedAbstractClass]
from abc import abstractmethod, ABCMeta

class A:
    class B(metaclass=ABCMeta):
        @abstractmethod
        def f(self) -> None: pass

    class C(B): pass

A.B()  # E: Cannot instantiate abstract class "B" with abstract attribute "f"
A.C()  # E: Cannot instantiate abstract class "C" with abstract attribute "f"

[case testAbstractNewTypeAllowed]
from typing import NewType, Mapping

Config = NewType('Config', Mapping[str, str])

bad = Mapping[str, str]()  # E: Cannot instantiate abstract class "Mapping" with abstract attribute "__iter__"
default = Config({'cannot': 'modify'})  # OK

default[1] = 2  # E: Unsupported target for indexed assignment ("Config")
[builtins fixtures/dict.pyi]
[typing fixtures/typing-full.pyi]

[case testSubclassOfABCFromDictionary]
from abc import abstractmethod, ABCMeta

class MyAbstractType(metaclass=ABCMeta):
  @abstractmethod
  def do(self): pass

class MyConcreteA(MyAbstractType):
  def do(self):
    print('A')

class MyConcreteB(MyAbstractType):
  def do(self):
    print('B')

class MyAbstractA(MyAbstractType):
  @abstractmethod
  def do(self): pass

class MyAbstractB(MyAbstractType):
  @abstractmethod
  def do(self): pass

my_concrete_types = {
  'A': MyConcreteA,
  'B': MyConcreteB,
}

my_abstract_types = {
  'A': MyAbstractA,
  'B': MyAbstractB,
}

reveal_type(my_concrete_types)  # N: Revealed type is "builtins.dict[builtins.str, def () -> __main__.MyAbstractType]"
reveal_type(my_abstract_types)  # N: Revealed type is "builtins.dict[builtins.str, def () -> __main__.MyAbstractType]"

a = my_concrete_types['A']()
a.do()
b = my_concrete_types['B']()
b.do()

c = my_abstract_types['A']()  # E: Cannot instantiate abstract class "MyAbstractType" with abstract attribute "do"
c.do()
d = my_abstract_types['B']()  # E: Cannot instantiate abstract class "MyAbstractType" with abstract attribute "do"
d.do()

[builtins fixtures/dict.pyi]

[case testAbstractClassesWorkWithGenericDecorators]
from abc import abstractmethod, ABCMeta
from typing import Type, TypeVar

T = TypeVar("T")
def deco(cls: Type[T]) -> Type[T]: return cls

@deco
class A(metaclass=ABCMeta):
    @abstractmethod
    def foo(self, x: int) -> None: ...

[case testAbstractPropertiesAllowed]
from abc import abstractmethod

class B:
    @property
    @abstractmethod
    def x(self) -> int: ...
    @property
    @abstractmethod
    def y(self) -> int: ...
    @y.setter
    @abstractmethod
    def y(self, value: int) -> None: ...

B()  # E: Cannot instantiate abstract class "B" with abstract attributes "x" and "y"
b: B
b.x = 1  # E: Property "x" defined in "B" is read-only
b.y = 1
[builtins fixtures/property.pyi]


-- Treatment of empty bodies in ABCs and protocols
-- -----------------------------------------------

[case testEmptyBodyProhibitedFunction]
from typing import overload, Union

def func1(x: str) -> int: pass  # E: Missing return statement
def func2(x: str) -> int: ...  # E: Missing return statement
def func3(x: str) -> int:  # E: Missing return statement
    """Some function."""

@overload
def func4(x: int) -> int: ...
@overload
def func4(x: str) -> str: ...
def func4(x: Union[int, str]) -> Union[int, str]:  # E: Missing return statement
    pass

@overload
def func5(x: int) -> int: ...
@overload
def func5(x: str) -> str: ...
def func5(x: Union[int, str]) -> Union[int, str]:  # E: Missing return statement
    """Some function."""

[case testEmptyBodyProhibitedMethodNonAbstract]
from typing import overload, Union

class A:
    def func1(self, x: str) -> int: pass  # E: Missing return statement
    def func2(self, x: str) -> int: ...  # E: Missing return statement
    def func3(self, x: str) -> int:  # E: Missing return statement
        """Some function."""

class B:
    @classmethod
    def func1(cls, x: str) -> int: pass  # E: Missing return statement
    @classmethod
    def func2(cls, x: str) -> int: ...  # E: Missing return statement
    @classmethod
    def func3(cls, x: str) -> int:  # E: Missing return statement
        """Some function."""

class C:
    @overload
    def func4(self, x: int) -> int: ...
    @overload
    def func4(self, x: str) -> str: ...
    def func4(self, x: Union[int, str]) -> Union[int, str]:  # E: Missing return statement
        pass

    @overload
    def func5(self, x: int) -> int: ...
    @overload
    def func5(self, x: str) -> str: ...
    def func5(self, x: Union[int, str]) -> Union[int, str]:  # E: Missing return statement
        """Some function."""
[builtins fixtures/classmethod.pyi]

[case testEmptyBodyProhibitedPropertyNonAbstract]
class A:
    @property
    def x(self) -> int: ...  # E: Missing return statement
    @property
    def y(self) -> int: ...  # E: Missing return statement
    @y.setter
    def y(self, value: int) -> None: ...

class B:
    @property
    def x(self) -> int: pass  # E: Missing return statement
    @property
    def y(self) -> int: pass  # E: Missing return statement
    @y.setter
    def y(self, value: int) -> None: pass

class C:
    @property
    def x(self) -> int:  # E: Missing return statement
       """Some property."""
    @property
    def y(self) -> int:  # E: Missing return statement
        """Some property."""
    @y.setter
    def y(self, value: int) -> None: pass
[builtins fixtures/property.pyi]

[case testEmptyBodyNoteABCMeta]
from abc import ABC

class A(ABC):
    def foo(self) -> int:  # E: Missing return statement \
                           # N: If the method is meant to be abstract, use @abc.abstractmethod
        ...

[case testEmptyBodyAllowedFunctionStub]
import stub
[file stub.pyi]
from typing import overload, Union

def func1(x: str) -> int: pass
def func2(x: str) -> int: ...
def func3(x: str) -> int:
    """Some function."""

[case testEmptyBodyAllowedMethodNonAbstractStub]
import stub
[file stub.pyi]
from typing import overload, Union

class A:
    def func1(self, x: str) -> int: pass
    def func2(self, x: str) -> int: ...
    def func3(self, x: str) -> int:
        """Some function."""

class B:
    @classmethod
    def func1(cls, x: str) -> int: pass
    @classmethod
    def func2(cls, x: str) -> int: ...
    @classmethod
    def func3(cls, x: str) -> int:
        """Some function."""
[builtins fixtures/classmethod.pyi]

[case testEmptyBodyAllowedPropertyNonAbstractStub]
import stub
[file stub.pyi]
class A:
    @property
    def x(self) -> int: ...
    @property
    def y(self) -> int: ...
    @y.setter
    def y(self, value: int) -> None: ...

class B:
    @property
    def x(self) -> int: pass
    @property
    def y(self) -> int: pass
    @y.setter
    def y(self, value: int) -> None: pass

class C:
    @property
    def x(self) -> int:
       """Some property."""
    @property
    def y(self) -> int:
        """Some property."""
    @y.setter
    def y(self, value: int) -> None: pass
[builtins fixtures/property.pyi]

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

class A:
    @abstractmethod
    def func1(self, x: str) -> int: pass
    @abstractmethod
    def func2(self, x: str) -> int: ...
    @abstractmethod
    def func3(self, x: str) -> int:
        """Some function."""

class B:
    @classmethod
    @abstractmethod
    def func1(cls, x: str) -> int: pass
    @classmethod
    @abstractmethod
    def func2(cls, x: str) -> int: ...
    @classmethod
    @abstractmethod
    def func3(cls, x: str) -> int:
        """Some function."""

class C:
    @overload
    @abstractmethod
    def func4(self, x: int) -> int: ...
    @overload
    @abstractmethod
    def func4(self, x: str) -> str: ...
    @abstractmethod
    def func4(self, x: Union[int, str]) -> Union[int, str]:
        pass

    @overload
    @abstractmethod
    def func5(self, x: int) -> int: ...
    @overload
    @abstractmethod
    def func5(self, x: str) -> str: ...
    @abstractmethod
    def func5(self, x: Union[int, str]) -> Union[int, str]:
        """Some function."""
[builtins fixtures/classmethod.pyi]

[case testEmptyBodyAllowedPropertyAbstract]
from abc import abstractmethod
class A:
    @property
    @abstractmethod
    def x(self) -> int: ...
    @property
    @abstractmethod
    def y(self) -> int: ...
    @y.setter
    @abstractmethod
    def y(self, value: int) -> None: ...

class B:
    @property
    @abstractmethod
    def x(self) -> int: pass
    @property
    @abstractmethod
    def y(self) -> int: pass
    @y.setter
    @abstractmethod
    def y(self, value: int) -> None: pass

class C:
    @property
    @abstractmethod
    def x(self) -> int:
       """Some property."""
    @property
    @abstractmethod
    def y(self) -> int:
        """Some property."""
    @y.setter
    @abstractmethod
    def y(self, value: int) -> None: pass
[builtins fixtures/property.pyi]

[case testEmptyBodyImplicitlyAbstractProtocol]
from typing import Protocol, overload, Union

class P1(Protocol):
    def meth(self) -> int: ...
class B1(P1): ...
class C1(P1):
    def meth(self) -> int:
        return 0
B1()  # E: Cannot instantiate abstract class "B1" with abstract attribute "meth"
C1()

class P2(Protocol):
    @classmethod
    def meth(cls) -> int: ...
class B2(P2): ...
class C2(P2):
    @classmethod
    def meth(cls) -> int:
        return 0
B2()  # E: Cannot instantiate abstract class "B2" with abstract attribute "meth"
C2()

class P3(Protocol):
    @overload
    def meth(self, x: int) -> int: ...
    @overload
    def meth(self, x: str) -> str: ...
class B3(P3): ...
class C3(P3):
    @overload
    def meth(self, x: int) -> int: ...
    @overload
    def meth(self, x: str) -> str: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return 0
B3()  # E: Cannot instantiate abstract class "B3" with abstract attribute "meth"
C3()
[builtins fixtures/classmethod.pyi]

[case testEmptyBodyImplicitlyAbstractProtocolProperty]
from typing import Protocol

class P1(Protocol):
    @property
    def attr(self) -> int: ...
class B1(P1): ...
class C1(P1):
    @property
    def attr(self) -> int:
        return 0
B1()  # E: Cannot instantiate abstract class "B1" with abstract attribute "attr"
C1()

class P2(Protocol):
    @property
    def attr(self) -> int: ...
    @attr.setter
    def attr(self, value: int) -> None: ...
class B2(P2): ...
class C2(P2):
    @property
    def attr(self) -> int: return 0
    @attr.setter
    def attr(self, value: int) -> None: pass
B2()  # E: Cannot instantiate abstract class "B2" with abstract attribute "attr"
C2()
[builtins fixtures/property.pyi]

[case testEmptyBodyImplicitlyAbstractProtocolStub]
from stub import P1, P2, P3, P4

class B1(P1): ...
class B2(P2): ...
class B3(P3): ...
class B4(P4): ...

B1()
B2()
B3()
B4()  # E: Cannot instantiate abstract class "B4" with abstract attribute "meth"

[file stub.pyi]
from typing import Protocol, overload, Union
from abc import abstractmethod

class P1(Protocol):
    def meth(self) -> int: ...

class P2(Protocol):
    @classmethod
    def meth(cls) -> int: ...

class P3(Protocol):
    @overload
    def meth(self, x: int) -> int: ...
    @overload
    def meth(self, x: str) -> str: ...

class P4(Protocol):
    @abstractmethod
    def meth(self) -> int: ...
[builtins fixtures/classmethod.pyi]

[case testEmptyBodyUnsafeAbstractSuper]
from stub import StubProto, StubAbstract
from typing import Protocol
from abc import abstractmethod

class Proto(Protocol):
    def meth(self) -> int: ...
class ProtoDef(Protocol):
    def meth(self) -> int: return 0

class Abstract:
    @abstractmethod
    def meth(self) -> int: ...
class AbstractDef:
    @abstractmethod
    def meth(self) -> int: return 0

class SubProto(Proto):
    def meth(self) -> int:
        return super().meth()  # E: Call to abstract method "meth" of "Proto" with trivial body via super() is unsafe
class SubProtoDef(ProtoDef):
    def meth(self) -> int:
        return super().meth()

class SubAbstract(Abstract):
    def meth(self) -> int:
        return super().meth()  # E: Call to abstract method "meth" of "Abstract" with trivial body via super() is unsafe
class SubAbstractDef(AbstractDef):
    def meth(self) -> int:
        return super().meth()

class SubStubProto(StubProto):
    def meth(self) -> int:
        return super().meth()
class SubStubAbstract(StubAbstract):
    def meth(self) -> int:
        return super().meth()

[file stub.pyi]
from typing import Protocol
from abc import abstractmethod

class StubProto(Protocol):
    def meth(self) -> int: ...
class StubAbstract:
    @abstractmethod
    def meth(self) -> int: ...

[case testEmptyBodyUnsafeAbstractSuperProperty]
from stub import StubProto, StubAbstract
from typing import Protocol
from abc import abstractmethod

class Proto(Protocol):
    @property
    def attr(self) -> int: ...
class SubProto(Proto):
    @property
    def attr(self) -> int: return super().attr  # E: Call to abstract method "attr" of "Proto" with trivial body via super() is unsafe

class ProtoDef(Protocol):
    @property
    def attr(self) -> int: return 0
class SubProtoDef(ProtoDef):
    @property
    def attr(self) -> int: return super().attr

class Abstract:
    @property
    @abstractmethod
    def attr(self) -> int: ...
class SubAbstract(Abstract):
    @property
    @abstractmethod
    def attr(self) -> int: return super().attr # E: Call to abstract method "attr" of "Abstract" with trivial body via super() is unsafe

class AbstractDef:
    @property
    @abstractmethod
    def attr(self) -> int: return 0
class SubAbstractDef(AbstractDef):
    @property
    @abstractmethod
    def attr(self) -> int: return super().attr

class SubStubProto(StubProto):
    @property
    def attr(self) -> int: return super().attr
class SubStubAbstract(StubAbstract):
    @property
    def attr(self) -> int: return super().attr

[file stub.pyi]
from typing import Protocol
from abc import abstractmethod

class StubProto(Protocol):
    @property
    def attr(self) -> int: ...
class StubAbstract:
    @property
    @abstractmethod
    def attr(self) -> int: ...
[builtins fixtures/property.pyi]

[case testEmptyBodyUnsafeAbstractSuperOverloads]
from stub import StubProto
from typing import Protocol, overload, Union

class ProtoEmptyImpl(Protocol):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        raise NotImplementedError
class ProtoDefImpl(Protocol):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return 0
class ProtoNoImpl(Protocol):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...

class SubProtoEmptyImpl(ProtoEmptyImpl):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return super().meth(0)  # E: Call to abstract method "meth" of "ProtoEmptyImpl" with trivial body via super() is unsafe
class SubProtoDefImpl(ProtoDefImpl):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return super().meth(0)
class SubStubProto(StubProto):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return super().meth(0)

# TODO: it would be good to also give an error in this case.
class SubProtoNoImpl(ProtoNoImpl):
    @overload
    def meth(self, x: str) -> str: ...
    @overload
    def meth(self, x: int) -> int: ...
    def meth(self, x: Union[int, str]) -> Union[int, str]:
        return super().meth(0)

[file stub.pyi]
from typing import Protocol, overload

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

[builtins fixtures/exception.pyi]

[case testEmptyBodyNoSuperWarningWithoutStrict]
# flags: --no-strict-optional
from typing import Protocol
from abc import abstractmethod

class Proto(Protocol):
    def meth(self) -> int: ...
class Abstract:
    @abstractmethod
    def meth(self) -> int: ...

class SubProto(Proto):
    def meth(self) -> int:
        return super().meth()  # E: Call to abstract method "meth" of "Proto" with trivial body via super() is unsafe
class SubAbstract(Abstract):
    def meth(self) -> int:
        return super().meth()  # E: Call to abstract method "meth" of "Abstract" with trivial body via super() is unsafe

[case testEmptyBodyNoSuperWarningOptionalReturn]
from typing import Protocol, Optional
from abc import abstractmethod

class Proto(Protocol):
    def meth(self) -> Optional[int]: pass
class Abstract:
    @abstractmethod
    def meth(self) -> Optional[int]: pass

class SubProto(Proto):
    def meth(self) -> Optional[int]:
        return super().meth()  # E: Call to abstract method "meth" of "Proto" with trivial body via super() is unsafe
class SubAbstract(Abstract):
    def meth(self) -> Optional[int]:
        return super().meth()  # E: Call to abstract method "meth" of "Abstract" with trivial body via super() is unsafe

[case testEmptyBodyTypeCheckingOnly]
from typing import TYPE_CHECKING

class C:
    if TYPE_CHECKING:
        def dynamic(self) -> int: ...  # OK