Handle more ParamSpec literal form special cases

This is more:tm: correct as shown by changes in test cases. I can't find
any issues that are closed by this though. From what I remember, this
was a followup fix for python#14903 in
order to fix some incorrect mypy-primer output.

Author: A5rocks

mypy/checkexpr.py

@@ -105,6 +105,7 @@
     has_any_from_unimported_type,
     instantiate_type_alias,
     make_optional_type,
+    pack_paramspec_args,
     set_any_tvars,
 )
 from mypy.typeops import (
@@ -4083,6 +4084,9 @@ def apply_type_arguments_to_callable(
         tp = get_proper_type(tp)
 
         if isinstance(tp, CallableType):
+            if len(tp.variables) == 1 and isinstance(tp.variables[0], ParamSpecType):
+                args = pack_paramspec_args(args)
+
             if len(tp.variables) != len(args):
                 if tp.is_type_obj() and tp.type_object().fullname == "builtins.tuple":
                     # TODO: Specialize the callable for the type arguments

mypy/typeanal.py

@@ -166,6 +166,29 @@ def no_subscript_builtin_alias(name: str, propose_alt: bool = True) -> str:
     return msg
 
 
+def pack_paramspec_args(an_args: Sequence[Type]) -> list[Type]:
+    # "Aesthetic" ParamSpec literals for single ParamSpec: C[int, str] -> C[[int, str]].
+    # These do not support mypy_extensions VarArgs, etc. as they were already analyzed
+    # TODO: should these be re-analyzed to get rid of this inconsistency?
+    count = len(an_args)
+    if count > 0:
+        first_arg = get_proper_type(an_args[0])
+        if not (count == 1 and isinstance(first_arg, (Parameters, ParamSpecType))):
+            if isinstance(first_arg, AnyType) and first_arg.type_of_any == TypeOfAny.from_error:
+                # Question: should I make new AnyTypes instead of reusing them?
+                return [
+                    Parameters(
+                        [first_arg, first_arg],
+                        [ARG_STAR, ARG_STAR2],
+                        [None, None],
+                        is_ellipsis_args=True,
+                    )
+                ]
+            else:
+                return [Parameters(an_args, [ARG_POS] * count, [None] * count)]
+    return list(an_args)
+
+
 class TypeAnalyser(SyntheticTypeVisitor[Type], TypeAnalyzerPluginInterface):
     """Semantic analyzer for types.
 
@@ -395,7 +418,7 @@ def visit_unbound_type_nonoptional(self, t: UnboundType, defining_literal: bool)
                     allow_param_spec_literals=node.has_param_spec_type,
                 )
                 if node.has_param_spec_type and len(node.alias_tvars) == 1:
-                    an_args = self.pack_paramspec_args(an_args)
+                    an_args = pack_paramspec_args(an_args)
 
                 disallow_any = self.options.disallow_any_generics and not self.is_typeshed_stub
                 res = instantiate_type_alias(
@@ -440,17 +463,6 @@ def visit_unbound_type_nonoptional(self, t: UnboundType, defining_literal: bool)
         else:  # sym is None
             return AnyType(TypeOfAny.special_form)
 
-    def pack_paramspec_args(self, an_args: Sequence[Type]) -> list[Type]:
-        # "Aesthetic" ParamSpec literals for single ParamSpec: C[int, str] -> C[[int, str]].
-        # These do not support mypy_extensions VarArgs, etc. as they were already analyzed
-        # TODO: should these be re-analyzed to get rid of this inconsistency?
-        count = len(an_args)
-        if count > 0:
-            first_arg = get_proper_type(an_args[0])
-            if not (count == 1 and isinstance(first_arg, (Parameters, ParamSpecType, AnyType))):
-                return [Parameters(an_args, [ARG_POS] * count, [None] * count)]
-        return list(an_args)
-
     def cannot_resolve_type(self, t: UnboundType) -> None:
         # TODO: Move error message generation to messages.py. We'd first
         #       need access to MessageBuilder here. Also move the similar
@@ -686,7 +698,7 @@ def analyze_type_with_type_info(
             ctx.column,
         )
         if len(info.type_vars) == 1 and info.has_param_spec_type:
-            instance.args = tuple(self.pack_paramspec_args(instance.args))
+            instance.args = tuple(pack_paramspec_args(instance.args))
 
         if info.has_type_var_tuple_type:
             if instance.args:

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

@@ -325,9 +325,12 @@ class C(Generic[P]):
     def m(self, *args: P.args, **kwargs: P.kwargs) -> int:
         return 1
 
-c: C[Any]
-reveal_type(c)  # N: Revealed type is "__main__.C[Any]"
-reveal_type(c.m)  # N: Revealed type is "def (*args: Any, **kwargs: Any) -> builtins.int"
+c_old: C[Any]
+reveal_type(c_old)  # N: Revealed type is "__main__.C[[Any]]"
+reveal_type(c_old.m)  # N: Revealed type is "def (Any) -> builtins.int"
+c: C[...]
+reveal_type(c)  # N: Revealed type is "__main__.C[...]"
+reveal_type(c.m)  # N: Revealed type is "def (*Any, **Any) -> builtins.int"
 c.m(4, 6, y='x')
 c = c
 
@@ -1520,3 +1523,16 @@ def identity(func: Callable[P, None]) -> Callable[P, None]: ...
 @identity
 def f(f: Callable[P, None], *args: P.args, **kwargs: P.kwargs) -> None: ...
 [builtins fixtures/paramspec.pyi]
+
+[case testRuntimeSpecialParamspecLiteralSyntax]
+import sub
+
+reveal_type(sub.Ex[None]())  # N: Revealed type is "sub.Ex[[None]]"
+[file sub/__init__.py]
+from typing_extensions import ParamSpec
+from typing import Generic
+
+P = ParamSpec("P")
+
+class Ex(Generic[P]): ...
+[builtins fixtures/paramspec.pyi]