Support type aliases, NamedTuple and TypedDict in constrained TypeVar defaults

mypy/checker.py

@@ -2658,7 +2658,7 @@ def check_typevar_defaults(self, tvars: Sequence[TypeVarLikeType]) -> None:
                 continue
             if not is_subtype(tv.default, tv.upper_bound):
                 self.fail("TypeVar default must be a subtype of the bound type", tv)
-            if tv.values and not any(tv.default == value for value in tv.values):
+            if tv.values and not any(is_same_type(tv.default, value) for value in tv.values):
                 self.fail("TypeVar default must be one of the constraint types", tv)
 
     def check_enum(self, defn: ClassDef) -> None:

mypy/checkexpr.py

@@ -6210,7 +6210,7 @@ def visit_type_var_expr(self, e: TypeVarExpr) -> Type:
         ):
             if not is_subtype(p_default, e.upper_bound):
                 self.chk.fail("TypeVar default must be a subtype of the bound type", e)
-            if e.values and not any(p_default == value for value in e.values):
+            if e.values and not any(is_same_type(p_default, value) for value in e.values):
                 self.chk.fail("TypeVar default must be one of the constraint types", e)
         return AnyType(TypeOfAny.special_form)
 

test-data/unit/check-python312.test

@@ -2042,3 +2042,27 @@ tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type i
 b: tuple[*tuple[int, ...], *tuple[int, ...]]  # E: More than one Unpack in a type is not allowed
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-full.pyi]
+
+[case testPEP695TypeVarConstraintsDefaultAliases]
+from typing import Generic
+from typing_extensions import TypeVar
+
+type K = int
+type V = int
+type L = list[int]
+
+T1 = TypeVar("T1", str, K, default=K)
+T2 = TypeVar("T2", str, K, default=V)
+T3 = TypeVar("T3", str, L, default=L)
+
+class A1(Generic[T1]):
+    x: T1
+class A2(Generic[T2]):
+    x: T2
+class A3(Generic[T3]):
+    x: T3
+
+reveal_type(A1().x)  # N: Revealed type is "builtins.int"
+reveal_type(A2().x)  # N: Revealed type is "builtins.int"
+reveal_type(A3().x)  # N: Revealed type is "builtins.list[builtins.int]"
+[builtins fixtures/tuple.pyi]

test-data/unit/check-python313.test

@@ -274,3 +274,19 @@ def func_d1(
     reveal_type(d)  # N: Revealed type is "__main__.A[builtins.float, builtins.str]"
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-full.pyi]
+
+[case testTypeVarConstraintsDefaultAliasesInline]
+type K = int
+type V = int
+
+class A1[T: (str, int) = K]:
+    x: T
+class A2[T: (str, K) = K]:
+    x: T
+class A3[T: (str, K) = V]:
+    x: T
+
+reveal_type(A1().x)  # N: Revealed type is "builtins.int"
+reveal_type(A2().x)  # N: Revealed type is "builtins.int"
+reveal_type(A3().x)  # N: Revealed type is "builtins.int"
+[builtins fixtures/tuple.pyi]

test-data/unit/check-typevar-defaults.test

@@ -729,8 +729,6 @@ class C(Generic[_I]): pass
 t: type[C] | int = C
 [builtins fixtures/tuple.pyi]
 
-
-
 [case testGenericTypeAliasWithDefaultTypeVarPreservesNoneInDefault]
 from typing_extensions import TypeVar
 from typing import Generic, Union
@@ -749,3 +747,104 @@ MyA = A[T1, int]
 a: MyA = A(None, 10)
 reveal_type(a.a)  # N: Revealed type is "Union[builtins.int, None]"
 [builtins fixtures/tuple.pyi]
+
+[case testTypeVarConstraintsDefaultAliasesTypeAliasType]
+from typing import Generic
+from typing_extensions import TypeAliasType, TypeVar
+
+K = TypeAliasType("K", int)
+V = TypeAliasType("V", int)
+L = TypeAliasType("L", list[int])
+T1 = TypeVar("T1", str, K, default=K)
+T2 = TypeVar("T2", str, K, default=V)
+T3 = TypeVar("T3", str, L, default=L)
+
+class A1(Generic[T1]):
+    x: T1
+class A2(Generic[T2]):
+    x: T2
+class A3(Generic[T3]):
+    x: T3
+
+reveal_type(A1().x)  # N: Revealed type is "builtins.int"
+reveal_type(A2().x)  # N: Revealed type is "builtins.int"
+reveal_type(A3().x)  # N: Revealed type is "builtins.list[builtins.int]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeVarConstraintsDefaultAliasesImplicitAlias]
+from typing_extensions import TypeVar
+
+K = int
+V = int
+L = list[int]
+T1 = TypeVar("T1", str, K, default=K)
+T2 = TypeVar("T2", str, K, default=V)
+T3 = TypeVar("T3", str, L, default=L)
+[builtins fixtures/tuple.pyi]
+
+[case testTypeVarConstraintsDefaultAliasesExplicitAlias]
+from typing_extensions import TypeAlias, TypeVar
+
+K: TypeAlias = int
+V: TypeAlias = int
+L: TypeAlias = list[int]
+T1 = TypeVar("T1", str, K, default=K)
+T2 = TypeVar("T2", str, K, default=V)
+T3 = TypeVar("T3", str, L, default=L)
+[builtins fixtures/tuple.pyi]
+
+[case testTypeVarConstraintsDefaultSpecialTypes]
+from typing import Generic, NamedTuple
+from typing_extensions import TypedDict, TypeVar
+
+class TD(TypedDict):
+    foo: str
+
+class NT(NamedTuple):
+    foo: str
+
+T1 = TypeVar("T1", str, TD, default=TD)
+T2 = TypeVar("T2", str, NT, default=NT)
+
+class A1(Generic[T1]):
+    x: T1
+class A2(Generic[T2]):
+    x: T2
+
+reveal_type(A1().x)  # N: Revealed type is "TypedDict('__main__.TD', {'foo': builtins.str})"
+reveal_type(A2().x)  # N: Revealed type is "Tuple[builtins.str, fallback=__main__.NT]"
+[builtins fixtures/tuple.pyi]
+
+[case testTypeVarConstraintsDefaultSpecialTypesGeneric]
+from typing import Generic, NamedTuple
+from typing_extensions import TypedDict, TypeVar
+
+T = TypeVar("T")
+
+class TD(TypedDict, Generic[T]):
+    foo: T
+class TD2(TD[int]): pass
+class TD3(TD[int]):
+    bar: str
+
+class NT(NamedTuple, Generic[T]):
+    foo: T
+class NT2(NT[int]): pass
+
+T1 = TypeVar("T1", str, TD[int], default=TD[int])
+T2 = TypeVar("T2", str, NT[int], default=NT[int])
+T3 = TypeVar("T3", str, TD2, default=TD[int])
+T4 = TypeVar("T4", str, TD3, default=TD[int])  # E: TypeVar default must be one of the constraint types
+T5 = TypeVar("T5", str, NT2, default=NT[int])  # E: TypeVar default must be one of the constraint types
+
+class A1(Generic[T1]):
+    x: T1
+class A2(Generic[T2]):
+    x: T2
+class A3(Generic[T3]):
+    x: T3
+
+reveal_type(A1().x)  # N: Revealed type is "TypedDict('__main__.TD', {'foo': builtins.int})"
+reveal_type(A2().x)  # N: Revealed type is "Tuple[builtins.int, fallback=__main__.NT[builtins.int]]"
+reveal_type(A3().x)  # N: Revealed type is "TypedDict('__main__.TD', {'foo': builtins.int})"
+[builtins fixtures/tuple.pyi]