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Merged
merged 8 commits into from
Aug 13, 2022
Merged

Make any callable compatible with (*args: Any, **kwargs: Any) #11203

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e5250d4
Make any callable compatible with (*args: Any, **kwargs: Any)
Sep 27, 2021
eb7f369
proper type
Sep 27, 2021
3c6f959
fix up tests
Sep 27, 2021
5d7cc46
another test
Sep 27, 2021
a3abf7b
Merge branch 'master' into anycallable
ilevkivskyi Aug 12, 2022
83fe962
Fix black
ilevkivskyi Aug 12, 2022
168e064
Fix a test
ilevkivskyi Aug 12, 2022
9edc6f8
Fix a test for real
ilevkivskyi Aug 12, 2022
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10 changes: 9 additions & 1 deletion mypy/subtypes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@
# import mypy.solve
from mypy.nodes import (
FuncBase, Var, Decorator, OverloadedFuncDef, TypeInfo, CONTRAVARIANT, COVARIANT,

ARG_STAR, ARG_STAR2,
)
from mypy.maptype import map_instance_to_supertype
from mypy.expandtype import expand_type_by_instance
Expand Down Expand Up @@ -893,6 +893,14 @@ def g(x: int) -> int: ...
right_star = right.var_arg()
right_star2 = right.kw_arg()

# Treat "def _(*a: Any, **kw: Any) -> X" similarly to "Callable[..., X]"
if (
right.arg_kinds == [ARG_STAR, ARG_STAR2]
and right_star and isinstance(get_proper_type(right_star.typ), AnyType)
and right_star2 and isinstance(get_proper_type(right_star2.typ), AnyType)
):
return True

# Match up corresponding arguments and check them for compatibility. In
# every pair (argL, argR) of corresponding arguments from L and R, argL must
# be "more general" than argR if L is to be a subtype of R.
Expand Down
11 changes: 11 additions & 0 deletions test-data/unit/check-classes.test
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Expand Up @@ -6891,3 +6891,14 @@ class B(A): # E: Final class __main__.B has abstract attributes "foo"
[case testUndefinedBaseclassInNestedClass]
class C:
class C1(XX): pass # E: Name "XX" is not defined


[case testArgsKwargsInheritance]
from typing import Any

class A(object):
def f(self, *args: Any, **kwargs: Any) -> int: ...

class B(A):
def f(self, x: int) -> int: ...
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I understand that this is very handy in some cases, #5876 has a handful of them. But, it is important to remember that this is not type-safe.

from typing import Any

class A(object):
    def f(self, *args: Any, **kwargs: Any) -> int: ...

class B(A):
    def f(self, x: int) -> int: ...

def test(arg: A):
    arg.f(x=0, kw1=1, kw2=2)

test(A())  # ok
test(B())  # mypy is ok with that, but raises TypeError in real-life

It breaks Liskov's law.

Maybe we can somehow limit the scope of this new rule? For example:

  • It is fine for decorator example from Make any callable compatible with (*args: Any, **kwargs: Any)? #5876
  • It is fine for Protocol check (when protocol defines less-or-equally broad signature): Procol.method(self, arg: int) -> is ok with Impl.method(self, *args, **kwargs)
  • It is fine for callbacks
  • Maybe something else
  • It is not fine for subclassing

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Yeah, I think the ask is explicitly for something that is not type safe. The check when "protocol defines less-or-equally broad signature" should already work. The decorator example from #5876 is a little interesting; this PR doesn't actually change inference there.

#5876 is probably a top five most popular mypy issue, so ideally something would be done. Maybe the answer is another flag.

[builtins fixtures/dict.pyi]
8 changes: 4 additions & 4 deletions test-data/unit/check-functions.test
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Expand Up @@ -188,9 +188,9 @@ if int():
ee_var = everywhere

if int():
ee_var = specific_1 # The difference between Callable[..., blah] and one with a *args: Any, **kwargs: Any is that the ... goes loosely both ways.
ee_var = specific_1
if int():
ee_def = specific_1 # E: Incompatible types in assignment (expression has type "Callable[[int, str], None]", variable has type "Callable[[VarArg(Any), KwArg(Any)], None]")
ee_def = specific_1

[builtins fixtures/dict.pyi]

Expand Down Expand Up @@ -1827,7 +1827,7 @@ def f2(*args, **kwargs) -> int: pass
d(f1)
e(f2)
d(f2)
e(f1) # E: Argument 1 to "e" has incompatible type "Callable[[VarArg(Any)], int]"; expected "Callable[[VarArg(Any), KwArg(Any)], int]"
e(f1)

[builtins fixtures/dict.pyi]

Expand Down Expand Up @@ -2224,7 +2224,7 @@ from typing import Callable
class A:
def f(self) -> None:
# In particular, test that the error message contains "g" of "A".
self.g() # E: Too few arguments for "g" of "A"
self.g() # E: Too few arguments for "g" of "A"
self.g(1)
@dec
def g(self, x: str) -> None: pass
Expand Down