Revert "Infer correct types with overloads of Type[Guard | Is] (#17678)"

This reverts commit 43ea203.

The commit caused a regression (#19139). If we can't fix the
regression soon enough, reverting the original change temporarily will
at least unblock the mypy public release. The reverted PR can be
merged again once the regression is fixed.

Author: JukkaL

mypy/checker.py

@@ -6160,31 +6160,15 @@ def find_isinstance_check_helper(
                         # considered "always right" (i.e. even if the types are not overlapping).
                         # Also note that a care must be taken to unwrap this back at read places
                         # where we use this to narrow down declared type.
-                        with self.msg.filter_errors(), self.local_type_map():
-                            # `node.callee` can be an `overload`ed function,
-                            # we need to resolve the real `overload` case.
-                            _, real_func = self.expr_checker.check_call(
-                                get_proper_type(self.lookup_type(node.callee)),
-                                node.args,
-                                node.arg_kinds,
-                                node,
-                                node.arg_names,
-                            )
-                        real_func = get_proper_type(real_func)
-                        if not isinstance(real_func, CallableType) or not (
-                            real_func.type_guard or real_func.type_is
-                        ):
-                            return {}, {}
-
-                        if real_func.type_guard is not None:
-                            return {expr: TypeGuardedType(real_func.type_guard)}, {}
+                        if node.callee.type_guard is not None:
+                            return {expr: TypeGuardedType(node.callee.type_guard)}, {}
                         else:
-                            assert real_func.type_is is not None
+                            assert node.callee.type_is is not None
                             return conditional_types_to_typemaps(
                                 expr,
                                 *self.conditional_types_with_intersection(
                                     self.lookup_type(expr),
-                                    [TypeRange(real_func.type_is, is_upper_bound=False)],
+                                    [TypeRange(node.callee.type_is, is_upper_bound=False)],
                                     expr,
                                 ),
                             )

mypy/checkexpr.py

@@ -2925,37 +2925,16 @@ def infer_overload_return_type(
             elif all_same_types([erase_type(typ) for typ in return_types]):
                 self.chk.store_types(type_maps[0])
                 return erase_type(return_types[0]), erase_type(inferred_types[0])
-            return self.check_call(
-                callee=AnyType(TypeOfAny.special_form),
-                args=args,
-                arg_kinds=arg_kinds,
-                arg_names=arg_names,
-                context=context,
-                callable_name=callable_name,
-                object_type=object_type,
-            )
-        elif not all_same_type_narrowers(matches):
-            # This is an example of how overloads can be:
-            #
-            # @overload
-            # def is_int(obj: float) -> TypeGuard[float]: ...
-            # @overload
-            # def is_int(obj: int) -> TypeGuard[int]: ...
-            #
-            # x: Any
-            # if is_int(x):
-            #     reveal_type(x)  # N: int | float
-            #
-            # So, we need to check that special case.
-            return self.check_call(
-                callee=self.combine_function_signatures(cast("list[ProperType]", matches)),
-                args=args,
-                arg_kinds=arg_kinds,
-                arg_names=arg_names,
-                context=context,
-                callable_name=callable_name,
-                object_type=object_type,
-            )
+            else:
+                return self.check_call(
+                    callee=AnyType(TypeOfAny.special_form),
+                    args=args,
+                    arg_kinds=arg_kinds,
+                    arg_names=arg_names,
+                    context=context,
+                    callable_name=callable_name,
+                    object_type=object_type,
+                )
         else:
             # Success! No ambiguity; return the first match.
             self.chk.store_types(type_maps[0])
@@ -3170,8 +3149,6 @@ def combine_function_signatures(self, types: list[ProperType]) -> AnyType | Call
         new_args: list[list[Type]] = [[] for _ in range(len(callables[0].arg_types))]
         new_kinds = list(callables[0].arg_kinds)
         new_returns: list[Type] = []
-        new_type_guards: list[Type] = []
-        new_type_narrowers: list[Type] = []
 
         too_complex = False
         for target in callables:
@@ -3198,25 +3175,8 @@ def combine_function_signatures(self, types: list[ProperType]) -> AnyType | Call
             for i, arg in enumerate(target.arg_types):
                 new_args[i].append(arg)
             new_returns.append(target.ret_type)
-            if target.type_guard:
-                new_type_guards.append(target.type_guard)
-            if target.type_is:
-                new_type_narrowers.append(target.type_is)
-
-        if new_type_guards and new_type_narrowers:
-            # They cannot be defined at the same time,
-            # declaring this function as too complex!
-            too_complex = True
-            union_type_guard = None
-            union_type_is = None
-        else:
-            union_type_guard = make_simplified_union(new_type_guards) if new_type_guards else None
-            union_type_is = (
-                make_simplified_union(new_type_narrowers) if new_type_narrowers else None
-            )
 
         union_return = make_simplified_union(new_returns)
-
         if too_complex:
             any = AnyType(TypeOfAny.special_form)
             return callables[0].copy_modified(
@@ -3226,8 +3186,6 @@ def combine_function_signatures(self, types: list[ProperType]) -> AnyType | Call
                 ret_type=union_return,
                 variables=variables,
                 implicit=True,
-                type_guard=union_type_guard,
-                type_is=union_type_is,
             )
 
         final_args = []
@@ -3241,8 +3199,6 @@ def combine_function_signatures(self, types: list[ProperType]) -> AnyType | Call
             ret_type=union_return,
             variables=variables,
             implicit=True,
-            type_guard=union_type_guard,
-            type_is=union_type_is,
         )
 
     def erased_signature_similarity(
@@ -6599,25 +6555,6 @@ def all_same_types(types: list[Type]) -> bool:
     return all(is_same_type(t, types[0]) for t in types[1:])
 
 
-def all_same_type_narrowers(types: list[CallableType]) -> bool:
-    if len(types) <= 1:
-        return True
-
-    type_guards: list[Type] = []
-    type_narrowers: list[Type] = []
-
-    for typ in types:
-        if typ.type_guard:
-            type_guards.append(typ.type_guard)
-        if typ.type_is:
-            type_narrowers.append(typ.type_is)
-    if type_guards and type_narrowers:
-        # Some overloads declare `TypeGuard` and some declare `TypeIs`,
-        # we cannot handle this in a union.
-        return False
-    return all_same_types(type_guards) and all_same_types(type_narrowers)
-
-
 def merge_typevars_in_callables_by_name(
     callables: Sequence[CallableType],
 ) -> tuple[list[CallableType], list[TypeVarType]]:

test-data/unit/check-typeguard.test

@@ -731,62 +731,6 @@ assert a(x=x)
 reveal_type(x)  # N: Revealed type is "builtins.int"
 [builtins fixtures/tuple.pyi]
 
-[case testTypeGuardInOverloads]
-from typing import Any, overload, Union
-from typing_extensions import TypeGuard
-
-@overload
-def func1(x: str) -> TypeGuard[str]:
-    ...
-
-@overload
-def func1(x: int) -> TypeGuard[int]:
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Any):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.str, builtins.int]"
-    else:
-        reveal_type(val)  # N: Revealed type is "Any"
-
-def func3(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-    else:
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-
-def func4(val: int):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "builtins.int"
-    else:
-        reveal_type(val)  # N: Revealed type is "builtins.int"
-[builtins fixtures/tuple.pyi]
-
-[case testTypeIsInOverloadsSameReturn]
-from typing import Any, overload, Union
-from typing_extensions import TypeGuard
-
-@overload
-def func1(x: str) -> TypeGuard[str]:
-    ...
-
-@overload
-def func1(x: int) -> TypeGuard[str]:
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "builtins.str"
-    else:
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-[builtins fixtures/tuple.pyi]
-
 [case testTypeGuardRestrictAwaySingleInvariant]
 from typing import List
 from typing_extensions import TypeGuard

test-data/unit/check-typeis.test

@@ -818,125 +818,6 @@ accept_typeguard(typeguard)
 
 [builtins fixtures/tuple.pyi]
 
-[case testTypeIsInOverloads]
-from typing import Any, overload, Union
-from typing_extensions import TypeIs
-
-@overload
-def func1(x: str) -> TypeIs[str]:
-    ...
-
-@overload
-def func1(x: int) -> TypeIs[int]:
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Any):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.str, builtins.int]"
-    else:
-        reveal_type(val)  # N: Revealed type is "Any"
-
-def func3(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-    else:
-        reveal_type(val)
-
-def func4(val: int):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "builtins.int"
-    else:
-        reveal_type(val)
-[builtins fixtures/tuple.pyi]
-
-[case testTypeIsInOverloadsSameReturn]
-from typing import Any, overload, Union
-from typing_extensions import TypeIs
-
-@overload
-def func1(x: str) -> TypeIs[str]:
-    ...
-
-@overload
-def func1(x: int) -> TypeIs[str]:  # type: ignore
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "builtins.str"
-    else:
-        reveal_type(val)  # N: Revealed type is "builtins.int"
-[builtins fixtures/tuple.pyi]
-
-[case testTypeIsInOverloadsUnionizeError]
-from typing import Any, overload, Union
-from typing_extensions import TypeIs, TypeGuard
-
-@overload
-def func1(x: str) -> TypeIs[str]:
-    ...
-
-@overload
-def func1(x: int) -> TypeGuard[int]:
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-    else:
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-[builtins fixtures/tuple.pyi]
-
-[case testTypeIsInOverloadsUnionizeError2]
-from typing import Any, overload, Union
-from typing_extensions import TypeIs, TypeGuard
-
-@overload
-def func1(x: int) -> TypeGuard[int]:
-    ...
-
-@overload
-def func1(x: str) -> TypeIs[str]:
-    ...
-
-def func1(x: Any) -> Any:
-    return True
-
-def func2(val: Union[int, str]):
-    if func1(val):
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-    else:
-        reveal_type(val)  # N: Revealed type is "Union[builtins.int, builtins.str]"
-[builtins fixtures/tuple.pyi]
-
-[case testTypeIsLikeIsDataclass]
-from typing import Any, overload, Union, Type
-from typing_extensions import TypeIs
-
-class DataclassInstance: ...
-
-@overload
-def is_dataclass(obj: type) -> TypeIs[Type[DataclassInstance]]: ...
-@overload
-def is_dataclass(obj: object) -> TypeIs[Union[DataclassInstance, Type[DataclassInstance]]]: ...
-
-def is_dataclass(obj: Union[type, object]) -> bool:
-    return False
-
-def func(arg: Any) -> None:
-    if is_dataclass(arg):
-        reveal_type(arg)  # N: Revealed type is "Union[Type[__main__.DataclassInstance], __main__.DataclassInstance]"
-[builtins fixtures/tuple.pyi]
-
 [case testTypeIsEnumOverlappingUnionExcludesIrrelevant]
 from enum import Enum
 from typing import Literal