Turn on ParamSpec semanal by default

This PR does not mean mypy supports PEP 612, but it does do enough to
unblock python#10862
mypy should now treat Callable[P, T] as Callable[..., T] and the
code paths with incomplete support will no longer crash (but will not do
what you'd want)

Author: hauntsaninja

mypy/applytype.py

@@ -19,6 +19,8 @@ def get_target_type(
     skip_unsatisfied: bool
 ) -> Optional[Type]:
     # TODO(shantanu): fix for ParamSpecDef
+    if not isinstance(tvar, TypeVarDef):
+        return None
     assert isinstance(tvar, TypeVarDef)
     values = get_proper_types(tvar.values)
     if values:

mypy/checkexpr.py

@@ -4481,6 +4481,8 @@ def merge_typevars_in_callables_by_name(
                 name = tvdef.fullname
                 if name not in unique_typevars:
                     # TODO(shantanu): fix for ParamSpecDef
+                    if not isinstance(tvdef, TypeVarDef):
+                        continue
                     assert isinstance(tvdef, TypeVarDef)
                     unique_typevars[name] = TypeVarType(tvdef)
                     variables.append(tvdef)

mypy/expandtype.py

@@ -41,6 +41,8 @@ def freshen_function_type_vars(callee: F) -> F:
         tvmap: Dict[TypeVarId, Type] = {}
         for v in callee.variables:
             # TODO(shantanu): fix for ParamSpecDef
+            if not isinstance(v, TypeVarDef):
+                continue
             assert isinstance(v, TypeVarDef)
             tvdef = TypeVarDef.new_unification_variable(v)
             tvdefs.append(tvdef)

mypy/main.py

@@ -852,8 +852,6 @@ def add_invertible_flag(flag: str,
     # Must be followed by another flag or by '--' (and then only file args may follow).
     parser.add_argument('--cache-map', nargs='+', dest='special-opts:cache_map',
                         help=argparse.SUPPRESS)
-    # PEP 612 support is a work in progress, hide it from users
-    parser.add_argument('--wip-pep-612', action="store_true", help=argparse.SUPPRESS)
 
     # options specifying code to check
     code_group = parser.add_argument_group(

mypy/options.py

@@ -242,9 +242,6 @@ def __init__(self) -> None:
         # mypy. (Like mypyc.)
         self.preserve_asts = False
 
-        # PEP 612 support is a work in progress, hide it from users
-        self.wip_pep_612 = False
-
         # Paths of user plugins
         self.plugins: List[str] = []
 

mypy/semanal.py

@@ -3151,8 +3151,6 @@ def process_paramspec_declaration(self, s: AssignmentStmt) -> bool:
         In the future, ParamSpec may accept bounds and variance arguments, in which
         case more aggressive sharing of code with process_typevar_declaration should be pursued.
         """
-        if not self.options.wip_pep_612:
-            return False
         call = self.get_typevarlike_declaration(
             s, ("typing_extensions.ParamSpec", "typing.ParamSpec")
         )

mypy/typeops.py

@@ -512,6 +512,8 @@ def true_or_false(t: Type) -> ProperType:
 
 def erase_def_to_union_or_bound(tdef: TypeVarLikeDef) -> Type:
     # TODO(shantanu): fix for ParamSpecDef
+    if not isinstance(tdef, TypeVarDef):
+        return AnyType(TypeOfAny.from_error)
     assert isinstance(tdef, TypeVarDef)
     if tdef.values:
         return make_simplified_union(tdef.values)

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

@@ -1,11 +1,9 @@
 [case testBasicParamSpec]
-# flags: --wip-pep-612
 from typing_extensions import ParamSpec
 P = ParamSpec('P')
 [builtins fixtures/tuple.pyi]
 
 [case testParamSpecLocations]
-# flags: --wip-pep-612
 from typing import Callable, List
 from typing_extensions import ParamSpec, Concatenate
 P = ParamSpec('P')

test-data/unit/semanal-errors.test

@@ -1426,7 +1426,6 @@ def g() -> None:
 [out]
 
 [case testParamSpec]
-# flags: --wip-pep-612
 from typing_extensions import ParamSpec
 
 TParams = ParamSpec('TParams')

test-data/unit/semanal-types.test

@@ -1500,12 +1500,11 @@ MypyFile:1(
 
 
 [case testParamSpec]
-# flags: --wip-pep-612
 from typing import ParamSpec
 P = ParamSpec("P")
 [out]
 MypyFile:1(
-  ImportFrom:2(typing, [ParamSpec])
-  AssignmentStmt:3(
+  ImportFrom:1(typing, [ParamSpec])
+  AssignmentStmt:2(
     NameExpr(P* [__main__.P])
-    ParamSpecExpr:3()))
+    ParamSpecExpr:2()))