Defer comprehension implicit-arg recast to __init__

The inlined recast and deferring to __init__ for the rare '.0'
comprehension argument perform identically, so keep the simpler version
that does not duplicate __init__'s logic.

Author: gaborbernat

Lib/inspect.py

@@ -2735,12 +2735,11 @@ def _from_valid_args(cls, name, kind, default, annotation):
         # the name comes from a code object's co_varnames -- always a valid,
         # non-keyword identifier -- and the kind is one of the module-level
         # _ParameterKind constants. Skips the validation done in __init__.
-        if name[0] == '.' and name[1:].isdigit():
-            # Implicit argument generated by a comprehension; recast '.N' as
-            # 'implicitN' and treat it as positional-only, as __init__ does
-            # (see gh-issue 19611).
-            kind = _POSITIONAL_ONLY
-            name = 'implicit' + name[1:]
+        # Implicit comprehension arguments ('.0') are rare and need the
+        # recast __init__ performs, so defer those to it rather than
+        # duplicate the logic here.
+        if name[0] == '.':
+            return cls(name, kind=kind, default=default, annotation=annotation)
         self = cls.__new__(cls)
         self._name = name
         self._kind = kind