Comments (7)
AlexWaygood
commented on September 27, 2024
1
Here's a slightly more minimal repro that doesn't involve Literal or Any:
from __future__ import annotations
from typing import Protocol, TypeVar, overload
X = TypeVar("X")
Y = TypeVar("Y")
X2 = TypeVar("X2")
Y2 = TypeVar("Y2")
class Transform(Protocol[X, Y]):
def __or__(self, other: Transform[X2, Y2]) -> Transform[tuple[X, X2], tuple[Y, Y2]]: ...
@overload
def chain_encoders(e: Transform[X, Y], simplify: bool) -> Transform[X, Y]: ...
@overload
def chain_encoders(*es: *tuple[*tuple[Transform, ...], Transform[X, object]]) -> Transform[X, Y]: ...The cause is a recursion error; recursion errors cause segfaults if the code has been compiled with mypyc. Here's the last part of the traceback if you use an uncompiled version of mypy from the master branch:
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 180, in is_subtype
return _is_subtype(left, right, subtype_context, proper_subtype=False)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 353, in _is_subtype
return left.accept(SubtypeVisitor(orig_right, subtype_context, proper_subtype))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 1966, in accept
return visitor.visit_callable_type(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 711, in visit_callable_type
return is_callable_compatible(
^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 1550, in is_callable_compatible
if not ignore_return and not is_compat_return(left.ret_type, right.ret_type):
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 415, in _is_subtype
return is_subtype(left, right, subtype_context=self.subtype_context)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 180, in is_subtype
return _is_subtype(left, right, subtype_context, proper_subtype=False)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 353, in _is_subtype
return left.accept(SubtypeVisitor(orig_right, subtype_context, proper_subtype))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 1422, in accept
return visitor.visit_instance(self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 607, in visit_instance
if right.type.is_protocol and is_protocol_implementation(
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/subtypes.py", line 1147, in is_protocol_implementation
if l == left and r == right:
^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 1434, in __eq__
and self.args == other.args
^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 2406, in __eq__
return self.items == other.items and self.partial_fallback == other.partial_fallback
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 2406, in __eq__
return self.items == other.items and self.partial_fallback == other.partial_fallback
^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/alexw/dev/mypy/mypy/types.py", line 2406, in __eq__
return self.items == other.items and self.partial_fallback == other.partial_fallback
^^^^^^^^^^^^^^^^^^^^^^^^^
[Previous line repeated 370 more times]
RecursionError: maximum recursion depth exceededfrom mypy.
AlexWaygood
commented on September 27, 2024
1
An appropriate issue title might be something like "segfault on recursive protocol used in overloaded function that also uses PEP-646"
from mypy.
ilevkivskyi
commented on September 27, 2024
1
This has actually nothing to do with overloads or tuples. The real problem is diverging recursive protocols. These are very similar to diverging recursive aliases (that are plain prohibited at semanal level), even though they (theoretically) may have real use cases (e.g. an exercise: represent a non-mixed union like list[T] | list[list[T]] | list[list[list[T]]] | ...).
Sorry for a detour, the real minimal repro is:
[case testDivergingProtocol]
from typing import Protocol, TypeVar, List
T = TypeVar("T")
class P(Protocol[T]):
def meth(self) -> P[List[T]]: ...
class C:
def meth(self) -> C: ...
x: P = C()
[builtins fixtures/tuple.pyi]
FWIW generic types like type A[T] = <something with A[Other[T]]>, where Other is an arbitrary non-identity (technically maybe non-linear, like not representable as a union with T) type constructor, are highly problematic. And not just in mypy, to the best of my knowledge, the only existing "algorithm" to handle them is finite nesting expansion.
TBH I am not sure what to do. We may just prohibit such protocols, and require them to be nominal classes.
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randolf-scholz
commented on September 27, 2024
Maybe related to #17319, since I also do tuple unpacking.
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randolf-scholz
commented on September 27, 2024
For context, the __or__ method here is simply the binary Cartesian product of functions. All I am saying here is if one has a Transform Transform f | g (as notational substitute for Transform from
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randolf-scholz
commented on September 27, 2024
class P(Protocol[T]): def meth(self) -> P[List[T]]: ... class C: def meth(self) -> C: ...
Hm, I think I see the issue, when trying to test C <: P[T], the condition on .meth leads to C <: P[T] ⟺ C <: P[list[T]] ⟺ C <: P[list[list[T]]] ⟺ ..., an infinite regress. However, there are no additional conditions here, so shouldn't T=Unknown be a trivial solution? That's what pyright reports: Code sample in pyright playground
from typing import Protocol
class P[T](Protocol):
def meth(self) -> "P[list[T]]": ...
class C:
def meth(self) -> "C":
return self
def as_p[T](x: P[T]) -> P[T]:
return x
reveal_type(as_p(C())) # P[Unknown]from mypy.
ilevkivskyi
commented on September 27, 2024
That's what
pyrightreports
Well, what do you think
export const maxTypeRecursionCount = 20;mean?
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