Require ListExpr for ParamSpec defaults

mypy/exprtotype.py

@@ -33,7 +33,6 @@
     Type,
     TypeList,
     TypeOfAny,
-    TypeOfTypeList,
     UnboundType,
     UnionType,
 )
@@ -162,12 +161,9 @@ def expr_to_unanalyzed_type(
             else:
                 raise TypeTranslationError()
         return CallableArgument(typ, name, arg_const, expr.line, expr.column)
-    elif isinstance(expr, (ListExpr, TupleExpr)):
+    elif isinstance(expr, ListExpr):
         return TypeList(
             [expr_to_unanalyzed_type(t, options, allow_new_syntax, expr) for t in expr.items],
-            TypeOfTypeList.callable_args
-            if isinstance(expr, ListExpr)
-            else TypeOfTypeList.param_spec_defaults,
             line=expr.line,
             column=expr.column,
         )

mypy/semanal.py

@@ -4114,9 +4114,7 @@ def process_typevar_parameters(
                 tv_arg = self.get_typevarlike_argument(
                     "TypeVar", param_name, param_value, context, allow_unbound_tvars=True
                 )
-                if tv_arg is None:
-                    return None
-                default = tv_arg
+                default = tv_arg or AnyType(TypeOfAny.from_error)
             elif param_name == "values":
                 # Probably using obsolete syntax with values=(...). Explain the current syntax.
                 self.fail('TypeVar "values" argument not supported', context)
@@ -4153,6 +4151,7 @@ def get_typevarlike_argument(
         *,
         allow_unbound_tvars: bool = False,
         allow_param_spec_literals: bool = False,
+        report_invalid_typevar_arg: bool = True,
     ) -> ProperType | None:
         try:
             # We want to use our custom error message below, so we suppress
@@ -4173,7 +4172,7 @@ def get_typevarlike_argument(
                 #         ...
                 analyzed = PlaceholderType(None, [], context.line)
             typ = get_proper_type(analyzed)
-            if isinstance(typ, AnyType) and typ.is_from_error:
+            if report_invalid_typevar_arg and isinstance(typ, AnyType) and typ.is_from_error:
                 self.fail(
                     message_registry.TYPEVAR_ARG_MUST_BE_TYPE.format(typevarlike_name, param_name),
                     param_value,
@@ -4182,10 +4181,11 @@ def get_typevarlike_argument(
                 # using the AnyType as the upper bound.
             return typ
         except TypeTranslationError:
-            self.fail(
-                message_registry.TYPEVAR_ARG_MUST_BE_TYPE.format(typevarlike_name, param_name),
-                param_value,
-            )
+            if report_invalid_typevar_arg:
+                self.fail(
+                    message_registry.TYPEVAR_ARG_MUST_BE_TYPE.format(typevarlike_name, param_name),
+                    param_value,
+                )
             return None
 
     def extract_typevarlike_name(self, s: AssignmentStmt, call: CallExpr) -> str | None:
@@ -4236,20 +4236,23 @@ def process_paramspec_declaration(self, s: AssignmentStmt) -> bool:
                     s,
                     allow_unbound_tvars=True,
                     allow_param_spec_literals=True,
+                    report_invalid_typevar_arg=False,
                 )
-                if tv_arg is None:
-                    return False
-                default = tv_arg
+                default = tv_arg or AnyType(TypeOfAny.from_error)
                 if isinstance(tv_arg, Parameters):
                     for i, arg_type in enumerate(tv_arg.arg_types):
                         typ = get_proper_type(arg_type)
                         if isinstance(typ, AnyType) and typ.is_from_error:
                             self.fail(
                                 f"Argument {i} of ParamSpec default must be a type", param_value
                             )
-                elif not isinstance(default, (AnyType, UnboundType)):
+                elif (
+                    isinstance(default, AnyType)
+                    and default.is_from_error
+                    or not isinstance(default, (AnyType, UnboundType))
+                ):
                     self.fail(
-                        "The default argument to ParamSpec must be a tuple expression, ellipsis, or a ParamSpec",
+                        "The default argument to ParamSpec must be a list expression, ellipsis, or a ParamSpec",
                         param_value,
                     )
                     default = AnyType(TypeOfAny.from_error)
@@ -4306,11 +4309,14 @@ def process_typevartuple_declaration(self, s: AssignmentStmt) -> bool:
         ):
             if param_name == "default":
                 tv_arg = self.get_typevarlike_argument(
-                    "TypeVarTuple", param_name, param_value, s, allow_unbound_tvars=True
+                    "TypeVarTuple",
+                    param_name,
+                    param_value,
+                    s,
+                    allow_unbound_tvars=True,
+                    report_invalid_typevar_arg=False,
                 )
-                if tv_arg is None:
-                    return False
-                default = tv_arg
+                default = tv_arg or AnyType(TypeOfAny.from_error)
                 if not isinstance(default, UnpackType):
                     self.fail(
                         "The default argument to TypeVarTuple must be an Unpacked tuple",

mypy/typeanal.py

@@ -72,7 +72,6 @@
     TypedDictType,
     TypeList,
     TypeOfAny,
-    TypeOfTypeList,
     TypeQuery,
     TypeType,
     TypeVarLikeType,
@@ -897,12 +896,10 @@ def visit_type_list(self, t: TypeList) -> Type:
             else:
                 return AnyType(TypeOfAny.from_error)
         else:
-            s = "[...]" if t.list_type == TypeOfTypeList.callable_args else "(...)"
             self.fail(
-                f'Bracketed expression "{s}" is not valid as a type', t, code=codes.VALID_TYPE
+                'Bracketed expression "[...]" is not valid as a type', t, code=codes.VALID_TYPE
             )
-            if t.list_type == TypeOfTypeList.callable_args:
-                self.note('Did you mean "List[...]"?', t)
+            self.note('Did you mean "List[...]"?', t)
             return AnyType(TypeOfAny.from_error)
 
     def visit_callable_argument(self, t: CallableArgument) -> Type:

mypy/types.py

@@ -197,17 +197,6 @@ class TypeOfAny:
     suggestion_engine: Final = 9
 
 
-class TypeOfTypeList:
-    """This class describes the different types of TypeList."""
-
-    __slots__ = ()
-
-    # List expressions for callable args
-    callable_args: Final = 1
-    # Tuple expressions for ParamSpec defaults
-    param_spec_defaults: Final = 2
-
-
 def deserialize_type(data: JsonDict | str) -> Type:
     if isinstance(data, str):
         return Instance.deserialize(data)
@@ -1005,20 +994,13 @@ class TypeList(ProperType):
     types before they are processed into Callable types.
     """
 
-    __slots__ = ("items", "list_type")
+    __slots__ = ("items",)
 
     items: list[Type]
 
-    def __init__(
-        self,
-        items: list[Type],
-        list_type: int = TypeOfTypeList.callable_args,
-        line: int = -1,
-        column: int = -1,
-    ) -> None:
+    def __init__(self, items: list[Type], line: int = -1, column: int = -1) -> None:
         super().__init__(line, column)
         self.items = items
-        self.list_type = list_type
 
     def accept(self, visitor: TypeVisitor[T]) -> T:
         assert isinstance(visitor, SyntheticTypeVisitor)
@@ -1032,11 +1014,7 @@ def __hash__(self) -> int:
         return hash(tuple(self.items))
 
     def __eq__(self, other: object) -> bool:
-        return (
-            isinstance(other, TypeList)
-            and self.items == other.items
-            and self.list_type == other.list_type
-        )
+        return isinstance(other, TypeList) and self.items == other.items
 
 
 class UnpackType(ProperType):

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

@@ -4,7 +4,7 @@ from typing import Generic, TypeVar, ParamSpec, Callable, Tuple, List
 from typing_extensions import TypeVarTuple, Unpack
 
 T1 = TypeVar("T1", default=int)
-P1 = ParamSpec("P1", default=(int, str))
+P1 = ParamSpec("P1", default=[int, str])
 Ts1 = TypeVarTuple("Ts1", default=Unpack[Tuple[int, str]])
 
 def f1(a: T1) -> List[T1]: ...
@@ -44,9 +44,9 @@ T5 = TypeVar("T5", default=S0)
 T6 = TypeVar("T6", bound=float, default=S1)
 # T7 = TypeVar("T7", bound=List[Any], default=List[S0])  # TODO
 
-P1 = ParamSpec("P1", default=())
+P1 = ParamSpec("P1", default=[])
 P2 = ParamSpec("P2", default=...)
-P3 = ParamSpec("P3", default=(int, str))
+P3 = ParamSpec("P3", default=[int, str])
 P4 = ParamSpec("P4", default=P0)
 
 Ts1 = TypeVarTuple("Ts1", default=Unpack[Tuple[int]])
@@ -59,15 +59,16 @@ from typing import TypeVar, ParamSpec, Tuple
 from typing_extensions import TypeVarTuple, Unpack
 
 T1 = TypeVar("T1", default=2)  # E: TypeVar "default" must be a type
-T2 = TypeVar("T2", default=(int, str))  # E: Bracketed expression "(...)" is not valid as a type \
+T2 = TypeVar("T2", default=[int, str])  # E: Bracketed expression "[...]" is not valid as a type \
+                                        # N: Did you mean "List[...]"? \
                                         # E: TypeVar "default" must be a type
 
-P1 = ParamSpec("P1", default=int)  # E: The default argument to ParamSpec must be a tuple expression, ellipsis, or a ParamSpec
-P2 = ParamSpec("P2", default=2)  # E: ParamSpec "default" must be a type
-P3 = ParamSpec("P3", default=(2, int))  # E: Argument 0 of ParamSpec default must be a type
+P1 = ParamSpec("P1", default=int)  # E: The default argument to ParamSpec must be a list expression, ellipsis, or a ParamSpec
+P2 = ParamSpec("P2", default=2)  # E: The default argument to ParamSpec must be a list expression, ellipsis, or a ParamSpec
+P3 = ParamSpec("P3", default=(2, int))  # E: The default argument to ParamSpec must be a list expression, ellipsis, or a ParamSpec
+P4 = ParamSpec("P4", default=[2, int])  # E: Argument 0 of ParamSpec default must be a type
 
-Ts1 = TypeVarTuple("Ts1", default=2)  # E: TypeVarTuple "default" must be a type \
-                                      # E: The default argument to TypeVarTuple must be an Unpacked tuple
+Ts1 = TypeVarTuple("Ts1", default=2) # E: The default argument to TypeVarTuple must be an Unpacked tuple
 Ts2 = TypeVarTuple("Ts2", default=int)  # E: The default argument to TypeVarTuple must be an Unpacked tuple
 Ts3 = TypeVarTuple("Ts3", default=Tuple[int])  # E: The default argument to TypeVarTuple must be an Unpacked tuple
 [builtins fixtures/tuple.pyi]

test-data/unit/semanal-errors.test

@@ -1045,7 +1045,7 @@ c = TypeVar(1)      # E: TypeVar() expects a string literal as first argument
 T = TypeVar(b'T')      # E: TypeVar() expects a string literal as first argument
 d = TypeVar('D')    # E: String argument 1 "D" to TypeVar(...) does not match variable name "d"
 e = TypeVar('e', int, str, x=1)   # E: Unexpected argument to "TypeVar()": "x"
-f = TypeVar('f', (int, str), int) # E: Bracketed expression "(...)" is not valid as a type
+f = TypeVar('f', (int, str), int) # E: Type expected
 g = TypeVar('g', int)             # E: TypeVar cannot have only a single constraint
 h = TypeVar('h', x=(int, str))    # E: Unexpected argument to "TypeVar()": "x"
 i = TypeVar('i', bound=1)         # E: TypeVar "bound" must be a type