Improve type checking of ParamSpec in calls

Check that the correct ParamSpec and flavor are used in
`*args` and `**kwargs`.

Follow-up to #11594.

Author: JukkaL

mypy/argmap.py

@@ -4,7 +4,7 @@
 
 from mypy.maptype import map_instance_to_supertype
 from mypy.types import (
-    Type, Instance, TupleType, AnyType, TypeOfAny, TypedDictType, get_proper_type
+    Type, Instance, TupleType, AnyType, TypeOfAny, TypedDictType, ParamSpecType, get_proper_type
 )
 from mypy import nodes
 
@@ -191,6 +191,9 @@ def expand_actual_type(self,
                 else:
                     self.tuple_index += 1
                 return actual_type.items[self.tuple_index - 1]
+            elif isinstance(actual_type, ParamSpecType):
+                # ParamSpec is valid in *args but it can't be unpacked.
+                return actual_type
             else:
                 return AnyType(TypeOfAny.from_error)
         elif actual_kind == nodes.ARG_STAR2:
@@ -215,6 +218,9 @@ def expand_actual_type(self,
                     actual_type,
                     self.context.mapping_type.type,
                 ).args[1]
+            elif isinstance(actual_type, ParamSpecType):
+                # ParamSpec is valid in **kwargs but it can't be unpacked.
+                return actual_type
             else:
                 return AnyType(TypeOfAny.from_error)
         else:

mypy/checkexpr.py

@@ -1032,24 +1032,24 @@ def check_callable_call(self,
             callee = self.infer_function_type_arguments(
                 callee, args, arg_kinds, formal_to_actual, context)
             if need_refresh:
-                # Argument kinds etc. may have changed; recalculate actual-to-formal map
+                # Argument kinds etc. may have changed due to
+                # ParamSpec variables being replaced with an arbitrary
+                # number of arguments; recalculate actual-to-formal map
                 formal_to_actual = map_actuals_to_formals(
                     arg_kinds, arg_names,
                     callee.arg_kinds, callee.arg_names,
                     lambda i: self.accept(args[i]))
 
         param_spec = callee.param_spec()
         if param_spec is not None and arg_kinds == [ARG_STAR, ARG_STAR2]:
-            arg1 = get_proper_type(self.accept(args[0]))
-            arg2 = get_proper_type(self.accept(args[1]))
-            if (is_named_instance(arg1, 'builtins.tuple')
-                    and is_named_instance(arg2, 'builtins.dict')):
-                assert isinstance(arg1, Instance)
-                assert isinstance(arg2, Instance)
-                if (isinstance(arg1.args[0], ParamSpecType)
-                        and isinstance(arg2.args[1], ParamSpecType)):
-                    # TODO: Check ParamSpec ids and flavors
-                    return callee.ret_type, callee
+            arg1 = self.accept(args[0])
+            arg2 = self.accept(args[1])
+            if (isinstance(arg1, ParamSpecType)
+                    and isinstance(arg2, ParamSpecType)
+                    and arg1.flavor == ParamSpecFlavor.ARGS
+                    and arg2.flavor == ParamSpecFlavor.KWARGS
+                    and arg1.id == arg2.id == param_spec.id):
+                return callee.ret_type, callee
 
         arg_types = self.infer_arg_types_in_context(
             callee, args, arg_kinds, formal_to_actual)
@@ -4003,7 +4003,7 @@ def is_valid_var_arg(self, typ: Type) -> bool:
                 is_subtype(typ, self.chk.named_generic_type('typing.Iterable',
                                                             [AnyType(TypeOfAny.special_form)])) or
                 isinstance(typ, AnyType) or
-                (isinstance(typ, ParamSpecType) and typ.flavor == ParamSpecFlavor.ARGS))
+                isinstance(typ, ParamSpecType))
 
     def is_valid_keyword_var_arg(self, typ: Type) -> bool:
         """Is a type valid as a **kwargs argument?"""
@@ -4012,7 +4012,7 @@ def is_valid_keyword_var_arg(self, typ: Type) -> bool:
                     [self.named_type('builtins.str'), AnyType(TypeOfAny.special_form)])) or
                 is_subtype(typ, self.chk.named_generic_type('typing.Mapping',
                     [UninhabitedType(), UninhabitedType()])) or
-                (isinstance(typ, ParamSpecType) and typ.flavor == ParamSpecFlavor.KWARGS)
+                isinstance(typ, ParamSpecType)
         )
         if self.chk.options.python_version[0] < 3:
             ret = ret or is_subtype(typ, self.chk.named_generic_type('typing.Mapping',

mypy/expandtype.py

@@ -106,6 +106,8 @@ def visit_param_spec(self, t: ParamSpecType) -> Type:
             # Return copy of instance with type erasure flag on.
             return Instance(inst.type, inst.args, line=inst.line,
                             column=inst.column, erased=True)
+        elif isinstance(repl, ParamSpecType):
+            return repl.with_flavor(t.flavor)
         else:
             return repl
 

mypy/types.py

@@ -491,6 +491,10 @@ def new_unification_variable(old: 'ParamSpecType') -> 'ParamSpecType':
         return ParamSpecType(old.name, old.fullname, new_id, old.flavor, old.upper_bound,
                              line=old.line, column=old.column)
 
+    def with_flavor(self, flavor: int) -> 'ParamSpecType':
+        return ParamSpecType(self.name, self.fullname, self.id, flavor,
+                             upper_bound=self.upper_bound)
+
     def accept(self, visitor: 'TypeVisitor[T]') -> T:
         return visitor.visit_param_spec(self)
 

test-data/unit/check-parameter-specification.test

@@ -346,3 +346,35 @@ reveal_type(register(lambda x: f(x), x=1))  # N: Revealed type is "def (x: Any)"
 register(lambda x: f(x))  # E: Missing positional argument "x" in call to "register"
 register(lambda x: f(x), y=1)  # E: Unexpected keyword argument "y" for "register"
 [builtins fixtures/dict.pyi]
+
+[case testParamSpecInvalidCalls]
+from typing import Callable, Generic
+from typing_extensions import ParamSpec
+
+P = ParamSpec('P')
+P2 = ParamSpec('P2')
+
+class C(Generic[P, P2]):
+    def m1(self, *args: P.args, **kwargs: P.kwargs) -> None:
+        self.m1(*args, **kwargs)
+        self.m2(*args, **kwargs)  # E: Argument 1 to "m2" of "C" has incompatible type "*P.args"; expected "P2.args" \
+            # E: Argument 2 to "m2" of "C" has incompatible type "**P.kwargs"; expected "P2.kwargs"
+        self.m1(*kwargs, **args)  # E: Argument 1 to "m1" of "C" has incompatible type "*P.kwargs"; expected "P.args" \
+            # E: Argument 2 to "m1" of "C" has incompatible type "**P.args"; expected "P.kwargs"
+        self.m3(*args, **kwargs)  # E: Argument 1 to "m3" of "C" has incompatible type "*P.args"; expected "int" \
+            # E: Argument 2 to "m3" of "C" has incompatible type "**P.kwargs"; expected "int"
+        self.m4(*args, **kwargs)  # E: Argument 1 to "m4" of "C" has incompatible type "*P.args"; expected "int" \
+            # E: Argument 2 to "m4" of "C" has incompatible type "**P.kwargs"; expected "int"
+
+        self.m1(*args, **args)  # E: Argument 2 to "m1" of "C" has incompatible type "**P.args"; expected "P.kwargs"
+        self.m1(*kwargs, **kwargs)  # E: Argument 1 to "m1" of "C" has incompatible type "*P.kwargs"; expected "P.args"
+
+    def m2(self, *args: P2.args, **kwargs: P2.kwargs) -> None:
+        pass
+
+    def m3(self, *args: int, **kwargs: int) -> None:
+        pass
+
+    def m4(self, x: int) -> None:
+        pass
+[builtins fixtures/dict.pyi]