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conformance: Fix TypeIs Any intersection case #2236

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18 changes: 9 additions & 9 deletions conformance/results/mypy/narrowing_typeis.toml
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Original file line number Diff line number Diff line change
@@ -1,15 +1,15 @@
conformant = "Pass"
output = """
narrowing_typeis.py:105: error: "TypeIs" functions must have a positional argument [valid-type]
narrowing_typeis.py:110: error: "TypeIs" functions must have a positional argument [valid-type]
narrowing_typeis.py:132: error: Argument 1 to "takes_callable_str" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], str]" [arg-type]
narrowing_typeis.py:152: error: Argument 1 to "takes_callable_str_proto" has incompatible type "Callable[[object], TypeIs[int]]"; expected "CallableStrProto" [arg-type]
narrowing_typeis.py:152: note: "CallableStrProto.__call__" has type "def __call__(self, val: object) -> str"
narrowing_typeis.py:169: error: Argument 1 to "takes_typeguard" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], TypeGuard[int]]" [arg-type]
narrowing_typeis.py:170: error: Argument 1 to "takes_typeis" has incompatible type "Callable[[object], TypeGuard[int]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:191: error: Argument 1 to "takes_int_typeis" has incompatible type "Callable[[object], TypeIs[bool]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:195: error: Narrowed type "str" is not a subtype of input type "int" [narrowed-type-not-subtype]
narrowing_typeis.py:199: error: Narrowed type "list[int]" is not a subtype of input type "list[object]" [narrowed-type-not-subtype]
narrowing_typeis.py:115: error: "TypeIs" functions must have a positional argument [valid-type]
narrowing_typeis.py:137: error: Argument 1 to "takes_callable_str" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], str]" [arg-type]
narrowing_typeis.py:157: error: Argument 1 to "takes_callable_str_proto" has incompatible type "Callable[[object], TypeIs[int]]"; expected "CallableStrProto" [arg-type]
narrowing_typeis.py:157: note: "CallableStrProto.__call__" has type "def __call__(self, val: object) -> str"
narrowing_typeis.py:174: error: Argument 1 to "takes_typeguard" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], TypeGuard[int]]" [arg-type]
narrowing_typeis.py:175: error: Argument 1 to "takes_typeis" has incompatible type "Callable[[object], TypeGuard[int]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:196: error: Argument 1 to "takes_int_typeis" has incompatible type "Callable[[object], TypeIs[bool]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:200: error: Narrowed type "str" is not a subtype of input type "int" [narrowed-type-not-subtype]
narrowing_typeis.py:204: error: Narrowed type "list[int]" is not a subtype of input type "list[object]" [narrowed-type-not-subtype]
"""
conformance_automated = "Pass"
errors_diff = """
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16 changes: 8 additions & 8 deletions conformance/results/pyrefly/narrowing_typeis.toml
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Expand Up @@ -3,13 +3,13 @@ conformance_automated = "Pass"
errors_diff = """
"""
output = """
ERROR narrowing_typeis.py:105:9-13: Type guard functions must accept at least one positional argument [bad-function-definition]
ERROR narrowing_typeis.py:110:9-13: Type guard functions must accept at least one positional argument [bad-function-definition]
ERROR narrowing_typeis.py:132:20-36: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `(object) -> str` in function `takes_callable_str` [bad-argument-type]
ERROR narrowing_typeis.py:152:26-42: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `CallableStrProto` in function `takes_callable_str_proto` [bad-argument-type]
ERROR narrowing_typeis.py:169:17-30: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `(object) -> TypeGuard[int]` in function `takes_typeguard` [bad-argument-type]
ERROR narrowing_typeis.py:170:14-30: Argument `(val: object) -> TypeGuard[int]` is not assignable to parameter `f` with type `(object) -> TypeIs[int]` in function `takes_typeis` [bad-argument-type]
ERROR narrowing_typeis.py:191:18-29: Argument `(val: object) -> TypeIs[bool]` is not assignable to parameter `f` with type `(object) -> TypeIs[int]` in function `takes_int_typeis` [bad-argument-type]
ERROR narrowing_typeis.py:195:5-15: Return type `str` must be assignable to the first argument type `int` [bad-function-definition]
ERROR narrowing_typeis.py:199:5-24: Return type `list[int]` must be assignable to the first argument type `list[object]` [bad-function-definition]
ERROR narrowing_typeis.py:115:9-13: Type guard functions must accept at least one positional argument [bad-function-definition]
ERROR narrowing_typeis.py:137:20-36: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `(object) -> str` in function `takes_callable_str` [bad-argument-type]
ERROR narrowing_typeis.py:157:26-42: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `CallableStrProto` in function `takes_callable_str_proto` [bad-argument-type]
ERROR narrowing_typeis.py:174:17-30: Argument `(val: object) -> TypeIs[int]` is not assignable to parameter `f` with type `(object) -> TypeGuard[int]` in function `takes_typeguard` [bad-argument-type]
ERROR narrowing_typeis.py:175:14-30: Argument `(val: object) -> TypeGuard[int]` is not assignable to parameter `f` with type `(object) -> TypeIs[int]` in function `takes_typeis` [bad-argument-type]
ERROR narrowing_typeis.py:196:18-29: Argument `(val: object) -> TypeIs[bool]` is not assignable to parameter `f` with type `(object) -> TypeIs[int]` in function `takes_int_typeis` [bad-argument-type]
ERROR narrowing_typeis.py:200:5-15: Return type `str` must be assignable to the first argument type `int` [bad-function-definition]
ERROR narrowing_typeis.py:204:5-24: Return type `list[int]` must be assignable to the first argument type `list[object]` [bad-function-definition]
"""
16 changes: 8 additions & 8 deletions conformance/results/pyright/narrowing_typeis.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -3,34 +3,34 @@ conformance_automated = "Pass"
errors_diff = """
"""
output = """
narrowing_typeis.py:105:9 - error: User-defined type guard functions and methods must have at least one input parameter (reportGeneralTypeIssues)
narrowing_typeis.py:110:9 - error: User-defined type guard functions and methods must have at least one input parameter (reportGeneralTypeIssues)
narrowing_typeis.py:132:20 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "(object) -> str" in function "takes_callable_str"
narrowing_typeis.py:115:9 - error: User-defined type guard functions and methods must have at least one input parameter (reportGeneralTypeIssues)
narrowing_typeis.py:137:20 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "(object) -> str" in function "takes_callable_str"
  Type "(val: object) -> TypeIs[int]" is not assignable to type "(object) -> str"
    Function return type "TypeIs[int]" is incompatible with type "str"
      "TypeIs[int]" is not assignable to "str"
      "bool" is not assignable to "str" (reportArgumentType)
narrowing_typeis.py:152:26 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "CallableStrProto" in function "takes_callable_str_proto"
narrowing_typeis.py:157:26 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "CallableStrProto" in function "takes_callable_str_proto"
  Type "(val: object) -> TypeIs[int]" is not assignable to type "(val: object) -> str"
    Function return type "TypeIs[int]" is incompatible with type "str"
      "TypeIs[int]" is not assignable to "str"
      "bool" is not assignable to "str" (reportArgumentType)
narrowing_typeis.py:169:17 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "(object) -> TypeGuard[int]" in function "takes_typeguard"
narrowing_typeis.py:174:17 - error: Argument of type "(val: object) -> TypeIs[int]" cannot be assigned to parameter "f" of type "(object) -> TypeGuard[int]" in function "takes_typeguard"
  Type "(val: object) -> TypeIs[int]" is not assignable to type "(object) -> TypeGuard[int]"
    Function return type "TypeIs[int]" is incompatible with type "TypeGuard[int]"
      "TypeIs[int]" is not assignable to "TypeGuard[int]"
      "bool" is not assignable to "TypeGuard[int]" (reportArgumentType)
narrowing_typeis.py:170:14 - error: Argument of type "(val: object) -> TypeGuard[int]" cannot be assigned to parameter "f" of type "(object) -> TypeIs[int]" in function "takes_typeis"
narrowing_typeis.py:175:14 - error: Argument of type "(val: object) -> TypeGuard[int]" cannot be assigned to parameter "f" of type "(object) -> TypeIs[int]" in function "takes_typeis"
  Type "(val: object) -> TypeGuard[int]" is not assignable to type "(object) -> TypeIs[int]"
    Function return type "TypeGuard[int]" is incompatible with type "TypeIs[int]"
      "TypeGuard[int]" is not assignable to "TypeIs[int]"
      "bool" is not assignable to "TypeIs[int]" (reportArgumentType)
narrowing_typeis.py:191:18 - error: Argument of type "(val: object) -> TypeIs[bool]" cannot be assigned to parameter "f" of type "(object) -> TypeIs[int]" in function "takes_int_typeis"
narrowing_typeis.py:196:18 - error: Argument of type "(val: object) -> TypeIs[bool]" cannot be assigned to parameter "f" of type "(object) -> TypeIs[int]" in function "takes_int_typeis"
  Type "(val: object) -> TypeIs[bool]" is not assignable to type "(object) -> TypeIs[int]"
    Function return type "TypeIs[bool]" is incompatible with type "TypeIs[int]"
      "TypeIs[bool]" is not assignable to "TypeIs[int]"
        Type parameter "T@TypeIs" is invariant, but "bool" is not the same as "int"
      "bool" is not assignable to "TypeIs[int]" (reportArgumentType)
narrowing_typeis.py:195:27 - error: Return type of TypeIs ("str") is not consistent with value parameter type ("int") (reportGeneralTypeIssues)
narrowing_typeis.py:199:45 - error: Return type of TypeIs ("list[int]") is not consistent with value parameter type ("list[object]") (reportGeneralTypeIssues)
narrowing_typeis.py:200:27 - error: Return type of TypeIs ("str") is not consistent with value parameter type ("int") (reportGeneralTypeIssues)
narrowing_typeis.py:204:45 - error: Return type of TypeIs ("list[int]") is not consistent with value parameter type ("list[object]") (reportGeneralTypeIssues)
"""
18 changes: 9 additions & 9 deletions conformance/results/ty/narrowing_typeis.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -8,13 +8,13 @@ Line 35: Unexpected errors ['narrowing_typeis.py:35:18: error[invalid-assignment
"""
output = """
narrowing_typeis.py:35:18: error[invalid-assignment] Object of type `object` is not assignable to `int`
narrowing_typeis.py:105:23: error[invalid-type-guard-definition] `TypeIs` function must have a parameter to narrow
narrowing_typeis.py:110:22: error[invalid-type-guard-definition] `TypeIs` function must have a parameter to narrow
narrowing_typeis.py:132:20: error[invalid-argument-type] Argument to function `takes_callable_str` is incorrect: Expected `(object, /) -> str`, found `def simple_typeguard(val: object) -> TypeIs[int]`
narrowing_typeis.py:152:26: error[invalid-argument-type] Argument to function `takes_callable_str_proto` is incorrect: Expected `CallableStrProto`, found `def simple_typeguard(val: object) -> TypeIs[int]`
narrowing_typeis.py:169:17: error[invalid-argument-type] Argument to function `takes_typeguard` is incorrect: Expected `(object, /) -> TypeGuard[int]`, found `def is_int_typeis(val: object) -> TypeIs[int]`
narrowing_typeis.py:170:14: error[invalid-argument-type] Argument to function `takes_typeis` is incorrect: Expected `(object, /) -> TypeIs[int]`, found `def is_int_typeguard(val: object) -> TypeGuard[int]`
narrowing_typeis.py:191:18: error[invalid-argument-type] Argument to function `takes_int_typeis` is incorrect: Expected `(object, /) -> TypeIs[int]`, found `def bool_typeis(val: object) -> TypeIs[bool]`
narrowing_typeis.py:195:27: error[invalid-type-guard-definition] Narrowed type `str` is not assignable to the declared parameter type `int`
narrowing_typeis.py:199:45: error[invalid-type-guard-definition] Narrowed type `list[int]` is not assignable to the declared parameter type `list[object]`
narrowing_typeis.py:110:23: error[invalid-type-guard-definition] `TypeIs` function must have a parameter to narrow
narrowing_typeis.py:115:22: error[invalid-type-guard-definition] `TypeIs` function must have a parameter to narrow
narrowing_typeis.py:137:20: error[invalid-argument-type] Argument to function `takes_callable_str` is incorrect: Expected `(object, /) -> str`, found `def simple_typeguard(val: object) -> TypeIs[int]`
narrowing_typeis.py:157:26: error[invalid-argument-type] Argument to function `takes_callable_str_proto` is incorrect: Expected `CallableStrProto`, found `def simple_typeguard(val: object) -> TypeIs[int]`
narrowing_typeis.py:174:17: error[invalid-argument-type] Argument to function `takes_typeguard` is incorrect: Expected `(object, /) -> TypeGuard[int]`, found `def is_int_typeis(val: object) -> TypeIs[int]`
narrowing_typeis.py:175:14: error[invalid-argument-type] Argument to function `takes_typeis` is incorrect: Expected `(object, /) -> TypeIs[int]`, found `def is_int_typeguard(val: object) -> TypeGuard[int]`
narrowing_typeis.py:196:18: error[invalid-argument-type] Argument to function `takes_int_typeis` is incorrect: Expected `(object, /) -> TypeIs[int]`, found `def bool_typeis(val: object) -> TypeIs[bool]`
narrowing_typeis.py:200:27: error[invalid-type-guard-definition] Narrowed type `str` is not assignable to the declared parameter type `int`
narrowing_typeis.py:204:45: error[invalid-type-guard-definition] Narrowed type `list[int]` is not assignable to the declared parameter type `list[object]`
"""
16 changes: 8 additions & 8 deletions conformance/results/zuban/narrowing_typeis.toml
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Expand Up @@ -2,13 +2,13 @@ conformance_automated = "Pass"
errors_diff = """
"""
output = """
narrowing_typeis.py:105: error: "TypeIs" functions must have a positional argument [misc]
narrowing_typeis.py:110: error: "TypeIs" functions must have a positional argument [misc]
narrowing_typeis.py:132: error: Argument 1 to "takes_callable_str" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], str]" [arg-type]
narrowing_typeis.py:152: error: Argument 1 to "takes_callable_str_proto" has incompatible type "Callable[[object], TypeIs[int]]"; expected "CallableStrProto" [arg-type]
narrowing_typeis.py:169: error: Argument 1 to "takes_typeguard" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], TypeGuard[int]]" [arg-type]
narrowing_typeis.py:170: error: Argument 1 to "takes_typeis" has incompatible type "Callable[[object], TypeGuard[int]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:191: error: Argument 1 to "takes_int_typeis" has incompatible type "Callable[[object], TypeIs[bool]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:195: error: Narrowed type "str" is not a subtype of input type "int" [narrowed-type-not-subtype]
narrowing_typeis.py:199: error: Narrowed type "list[int]" is not a subtype of input type "list[object]" [narrowed-type-not-subtype]
narrowing_typeis.py:115: error: "TypeIs" functions must have a positional argument [misc]
narrowing_typeis.py:137: error: Argument 1 to "takes_callable_str" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], str]" [arg-type]
narrowing_typeis.py:157: error: Argument 1 to "takes_callable_str_proto" has incompatible type "Callable[[object], TypeIs[int]]"; expected "CallableStrProto" [arg-type]
narrowing_typeis.py:174: error: Argument 1 to "takes_typeguard" has incompatible type "Callable[[object], TypeIs[int]]"; expected "Callable[[object], TypeGuard[int]]" [arg-type]
narrowing_typeis.py:175: error: Argument 1 to "takes_typeis" has incompatible type "Callable[[object], TypeGuard[int]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:196: error: Argument 1 to "takes_int_typeis" has incompatible type "Callable[[object], TypeIs[bool]]"; expected "Callable[[object], TypeIs[int]]" [arg-type]
narrowing_typeis.py:200: error: Narrowed type "str" is not a subtype of input type "int" [narrowed-type-not-subtype]
narrowing_typeis.py:204: error: Narrowed type "list[int]" is not a subtype of input type "list[object]" [narrowed-type-not-subtype]
"""
7 changes: 6 additions & 1 deletion conformance/tests/narrowing_typeis.py
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Expand Up @@ -35,7 +35,12 @@ async def func2(val: int | Awaitable[int]):
x: int = await val
return x
else:
assert_type(val, int)
# We can't say much here. The strictly correct answer is
# (int | Awaitable[int]) & ~Awaitable[Any], but conformant implementations
# may simplify this.
# But it should definitely remain assignable to `int | Awaitable[int]`.
y: int | Awaitable[int] = val
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@rchen152 rchen152 Apr 3, 2026

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I feel like this isn't testing all that much anymore. Not sure how to improve it, though ^^;

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@JelleZijlstra JelleZijlstra Apr 3, 2026

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Yes, unfortunately I can't think of a better way here. Using theoretically correct intersection semantics is not always practical. For reference here are the tests I added to pycroscope while looking at this: https://github.com/JelleZijlstra/pycroscope/pull/444/changes#diff-17d47f7718e5c338fb6076c1e2971a2ca798555e661e881cd1653cf5e54d99fe

I tried both TypeIs[Awaitable[Any]] and TypeIs[Awaitable[object]].

Among the current type checkers, two type checkers actually have explicit intersections, but neither produces the full theoretically correct types. Ty treats the Awaitable[Any] TypeIs as if it's Awaitable[object]. That behaves better in some cases but worse in others; in this check it means that y: int = await val is rejected because val might also be int & Awaitable[object]. Pycroscope (unreleased version) doesn't do that but it drops negation types, so the else branch types are simpler.

Three of the other type checkers (mypy, zuban, pyright) narrow to Awaitable[int] and int for both the Any and object guards; pyrefly narrows to Awaitable[Any] for the TypeIs[Awaitable[Any]]. This is unsound but perhaps more practical than the precise intersection behavior.

return y


T_A = TypeVar("T_A", bound="A")
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