Use tuple[object, ...] and dict[str, object] as upper bounds for ParamSpec.args and ParamSpec.kwargs (#12668)

Mypy thought that a variable annotated with P.args is not iterable, and 
that a variable annotated with P.kwargs does not have a .pop() method.

Fixes #12386.

Author: AlexWaygood

mypy/checkmember.py

@@ -164,7 +164,7 @@ def _analyze_member_access(name: str,
         return analyze_typeddict_access(name, typ, mx, override_info)
     elif isinstance(typ, NoneType):
         return analyze_none_member_access(name, typ, mx)
-    elif isinstance(typ, TypeVarType):
+    elif isinstance(typ, TypeVarLikeType):
         return _analyze_member_access(name, typ.upper_bound, mx, override_info)
     elif isinstance(typ, DeletedType):
         mx.msg.deleted_as_rvalue(typ, mx.context)

mypy/semanal_shared.py

@@ -2,16 +2,17 @@
 
 from abc import abstractmethod
 
-from typing import Optional, List, Callable
-from typing_extensions import Final
+from typing import Optional, List, Callable, Union
+from typing_extensions import Final, Protocol
 from mypy_extensions import trait
 
 from mypy.nodes import (
     Context, SymbolTableNode, FuncDef, Node, TypeInfo, Expression,
     SymbolNode, SymbolTable
 )
 from mypy.types import (
-    Type, FunctionLike, Instance, TupleType, TPDICT_FB_NAMES, ProperType, get_proper_type
+    Type, FunctionLike, Instance, TupleType, TPDICT_FB_NAMES, ProperType, get_proper_type,
+    ParamSpecType, ParamSpecFlavor, Parameters, TypeVarId
 )
 from mypy.tvar_scope import TypeVarLikeScope
 from mypy.errorcodes import ErrorCode
@@ -212,3 +213,46 @@ def calculate_tuple_fallback(typ: TupleType) -> None:
     fallback = typ.partial_fallback
     assert fallback.type.fullname == 'builtins.tuple'
     fallback.args = (join.join_type_list(list(typ.items)),) + fallback.args[1:]
+
+
+class _NamedTypeCallback(Protocol):
+    def __call__(
+        self, fully_qualified_name: str, args: Optional[List[Type]] = None
+    ) -> Instance: ...
+
+
+def paramspec_args(
+    name: str, fullname: str, id: Union[TypeVarId, int], *,
+    named_type_func: _NamedTypeCallback, line: int = -1, column: int = -1,
+    prefix: Optional[Parameters] = None
+) -> ParamSpecType:
+    return ParamSpecType(
+        name,
+        fullname,
+        id,
+        flavor=ParamSpecFlavor.ARGS,
+        upper_bound=named_type_func('builtins.tuple', [named_type_func('builtins.object')]),
+        line=line,
+        column=column,
+        prefix=prefix
+    )
+
+
+def paramspec_kwargs(
+    name: str, fullname: str, id: Union[TypeVarId, int], *,
+    named_type_func: _NamedTypeCallback, line: int = -1, column: int = -1,
+    prefix: Optional[Parameters] = None
+) -> ParamSpecType:
+    return ParamSpecType(
+        name,
+        fullname,
+        id,
+        flavor=ParamSpecFlavor.KWARGS,
+        upper_bound=named_type_func(
+            'builtins.dict',
+            [named_type_func('builtins.str'), named_type_func('builtins.object')]
+        ),
+        line=line,
+        column=column,
+        prefix=prefix
+    )

mypy/typeanal.py

@@ -33,7 +33,7 @@
 from mypy.tvar_scope import TypeVarLikeScope
 from mypy.exprtotype import expr_to_unanalyzed_type, TypeTranslationError
 from mypy.plugin import Plugin, TypeAnalyzerPluginInterface, AnalyzeTypeContext
-from mypy.semanal_shared import SemanticAnalyzerCoreInterface
+from mypy.semanal_shared import SemanticAnalyzerCoreInterface, paramspec_args, paramspec_kwargs
 from mypy.errorcodes import ErrorCode
 from mypy import nodes, message_registry, errorcodes as codes
 
@@ -711,13 +711,13 @@ def anal_star_arg_type(self, t: Type, kind: ArgKind, nested: bool) -> Type:
                 tvar_def = self.tvar_scope.get_binding(sym)
                 if isinstance(tvar_def, ParamSpecType):
                     if kind == ARG_STAR:
-                        flavor = ParamSpecFlavor.ARGS
+                        make_paramspec = paramspec_args
                     elif kind == ARG_STAR2:
-                        flavor = ParamSpecFlavor.KWARGS
+                        make_paramspec = paramspec_kwargs
                     else:
                         assert False, kind
-                    return ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, flavor,
-                                         upper_bound=self.named_type('builtins.object'),
+                    return make_paramspec(tvar_def.name, tvar_def.fullname, tvar_def.id,
+                                         named_type_func=self.named_type,
                                          line=t.line, column=t.column)
         return self.anal_type(t, nested=nested)
 
@@ -855,13 +855,11 @@ def analyze_callable_args_for_paramspec(
         if not isinstance(tvar_def, ParamSpecType):
             return None
 
-        # TODO: Use tuple[...] or Mapping[..] instead?
-        obj = self.named_type('builtins.object')
         return CallableType(
-            [ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.ARGS,
-                           upper_bound=obj),
-             ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.KWARGS,
-                           upper_bound=obj)],
+            [paramspec_args(tvar_def.name, tvar_def.fullname, tvar_def.id,
+                           named_type_func=self.named_type),
+             paramspec_kwargs(tvar_def.name, tvar_def.fullname, tvar_def.id,
+                           named_type_func=self.named_type)],
             [nodes.ARG_STAR, nodes.ARG_STAR2],
             [None, None],
             ret_type=ret_type,
@@ -891,18 +889,16 @@ def analyze_callable_args_for_concatenate(
         if not isinstance(tvar_def, ParamSpecType):
             return None
 
-        # TODO: Use tuple[...] or Mapping[..] instead?
-        obj = self.named_type('builtins.object')
         # ick, CallableType should take ParamSpecType
         prefix = tvar_def.prefix
         # we don't set the prefix here as generic arguments will get updated at some point
         # in the future. CallableType.param_spec() accounts for this.
         return CallableType(
             [*prefix.arg_types,
-             ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.ARGS,
-                           upper_bound=obj),
-             ParamSpecType(tvar_def.name, tvar_def.fullname, tvar_def.id, ParamSpecFlavor.KWARGS,
-                           upper_bound=obj)],
+             paramspec_args(tvar_def.name, tvar_def.fullname, tvar_def.id,
+                           named_type_func=self.named_type),
+             paramspec_kwargs(tvar_def.name, tvar_def.fullname, tvar_def.id,
+                           named_type_func=self.named_type)],
             [*prefix.arg_kinds, nodes.ARG_STAR, nodes.ARG_STAR2],
             [*prefix.arg_names, None, None],
             ret_type=ret_type,