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Disallow calling type on Protocol #18095

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Disallow calling type on Protocol #18095

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afa72b9
Disallow calling type on Protocol
hauntsaninja Nov 3, 2024
2dc29e6
okay, fallback because of primer hits
hauntsaninja Nov 3, 2024
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16 changes: 14 additions & 2 deletions mypy/checkexpr.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1802,10 +1802,22 @@ def check_callable_call(

if (
callee.is_type_obj()
and (len(arg_types) == 1)
and len(arg_types) == 1
and is_equivalent(callee.ret_type, self.named_type("builtins.type"))
):
callee = callee.copy_modified(ret_type=TypeType.make_normalized(arg_types[0]))
proper_arg = get_proper_type(arg_types[0])
if isinstance(proper_arg, Instance) and proper_arg.type.is_protocol:
callee = callee.copy_modified(
ret_type=UnionType(
[
self.named_type("builtins.type"),
self.named_type("types.ModuleType"),
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(sorry, I got confused myself, deleted & reposted)

self.named_type('types.ModuleType') isn't the correct type here:

import types
assert type(types) is types.ModuleType

When you call type(some_module), you obtain types.ModuleType class itself, not its instance. So this union isn't type | types.ModuleType | Any, it should be type | type[ModuleType] | Any, and at this point type[ModuleType] member is redundant (it's also a type, isn't it?).

AnyType(TypeOfAny.special_form),
]
)
)
else:
callee = callee.copy_modified(ret_type=TypeType.make_normalized(arg_types[0]))

if callable_node:
# Store the inferred callable type.
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29 changes: 29 additions & 0 deletions test-data/unit/check-protocols.test
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Original file line number Diff line number Diff line change
Expand Up @@ -4215,3 +4215,32 @@ def g4(a: Input[bytes], b: Output[str]) -> None:
f(a, b) # E: Cannot infer type argument 1 of "f"

[builtins fixtures/tuple.pyi]

[case testTypeCallOnProtocol]
from typing import Any, Protocol, cast
import types

class P(Protocol):
def foo(self) -> None: ...

import mod

a: P = mod
value = type(a)
reveal_type(value) # N: Revealed type is "Union[builtins.type, types.ModuleType, Any]"
reveal_type(value.foo) # E: Item "type" of "Union[type, Module, Any]" has no attribute "foo" \
# N: Revealed type is "Any"

class Namespace: ...
n = Namespace()
n.foo = lambda: None # E: "Namespace" has no attribute "foo"

b: P = cast(Any, n)
value = type(b)
reveal_type(value) # N: Revealed type is "Union[builtins.type, types.ModuleType, Any]"
reveal_type(value.foo) # E: Item "type" of "Union[type, Module, Any]" has no attribute "foo" \
# N: Revealed type is "Any"
[file mod.py]
def foo() -> None: ...

[builtins fixtures/tuple.pyi]
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