Fix constructor calls for union-bounded TypeVars (#21571)

Fixes #21106

Author: 97littleleaf11

mypy/checkexpr.py

@@ -1948,12 +1948,7 @@ def analyze_type_type_callee(self, item: ProperType, context: Context) -> Type:
             # but better than AnyType...), but replace the return type
             # with typevar.
             callee = self.analyze_type_type_callee(get_proper_type(item.upper_bound), context)
-            callee = get_proper_type(callee)
-            if isinstance(callee, CallableType):
-                callee = callee.copy_modified(ret_type=item)
-            elif isinstance(callee, Overloaded):
-                callee = Overloaded([c.copy_modified(ret_type=item) for c in callee.items])
-            return callee
+            return self.replace_type_type_callee_ret_type(callee, item)
         # We support Type of namedtuples but not of tuples in general
         if isinstance(item, TupleType) and tuple_fallback(item).type.fullname != "builtins.tuple":
             return self.analyze_type_type_callee(tuple_fallback(item), context)
@@ -1963,6 +1958,23 @@ def analyze_type_type_callee(self, item: ProperType, context: Context) -> Type:
         self.msg.unsupported_type_type(item, context)
         return AnyType(TypeOfAny.from_error)
 
+    def replace_type_type_callee_ret_type(self, callee: Type, ret_type: Type) -> Type:
+        callee = get_proper_type(callee)
+        if isinstance(callee, CallableType):
+            return callee.copy_modified(ret_type=ret_type)
+        if isinstance(callee, Overloaded):
+            return Overloaded([c.copy_modified(ret_type=ret_type) for c in callee.items])
+        if isinstance(callee, UnionType):
+            return UnionType(
+                [
+                    self.replace_type_type_callee_ret_type(item, ret_type)
+                    for item in callee.relevant_items()
+                ],
+                line=callee.line,
+                column=callee.column,
+            )
+        return callee
+
     def infer_arg_types_in_empty_context(self, args: list[Expression]) -> list[Type]:
         """Infer argument expression types in an empty context.
 

test-data/unit/check-classes.test

@@ -3889,6 +3889,24 @@ def process(cls: Type[U]):
 [builtins fixtures/classmethod.pyi]
 [out]
 
+[case testTypeUsingTypeCConstructorReturnFromTypeVarUnionBound]
+from typing import Optional, Type, TypeVar, Union
+
+class A:
+    def __init__(self, value: str = "") -> None: pass
+class B:
+    def __init__(self, value: str = "") -> None: pass
+
+T = TypeVar("T", bound=Union[A, B])
+
+def make(ftype: Type[T], value: Optional[str]) -> T:
+    if value is None:
+        return ftype()
+    return ftype(value)
+
+reveal_type(make(A, "a"))  # N: Revealed type is "__main__.A"
+reveal_type(make(B, None))  # N: Revealed type is "__main__.B"
+
 [case testTypeUsingTypeCErrorUnsupportedType]
 from typing import Type, Tuple
 def foo(arg: Type[Tuple[int]]):

test-data/unit/check-python310.test

@@ -3531,7 +3531,7 @@ def switch(choice: type[T_Choice]) -> None:
             reveal_type(choice())  # N: Revealed type is "b.Two"
         case _:
             reveal_type(choice)  # N: Revealed type is "type[T_Choice`-1]"
-            reveal_type(choice())  # N: Revealed type is "b.One | b.Two"
+            reveal_type(choice())  # N: Revealed type is "T_Choice`-1"
 
 [file b.py]
 class One: ...

test-data/unit/check-python312.test

@@ -824,6 +824,20 @@ f(1, u)
 f('x', None)  # E: Value of type variable "T" of "f" cannot be "str" \
               # E: Value of type variable "S" of "f" cannot be "None"
 
+[case testPEP695UpperBoundTypeTypeConstructorReturnType]
+class A:
+    def __init__(self, value: str = "") -> None: pass
+class B:
+    def __init__(self, value: str = "") -> None: pass
+
+def make[T: A | B](ftype: type[T], value: str | None) -> T:
+    if value is None:
+        return ftype()
+    return ftype(value)
+
+reveal_type(make(A, "a"))  # N: Revealed type is "__main__.A"
+reveal_type(make(B, None))  # N: Revealed type is "__main__.B"
+
 [case testPEP695InferVarianceOfTupleType]
 class Cov[T](tuple[int, str]):
     def f(self) -> T: pass