Single-source the bare-string name_order guard

The identical TypeError lived in both Policy and PolicyPatch
__post_init__ and could drift; extracted to a module helper. Also add
the missing back-reference on Lexicon.__setstate__ pointing at its
deliberately-duplicated twin in _types (the sync note was previously
one-directional).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: derek73

nameparser/_lexicon.py

@@ -204,6 +204,8 @@ def __setstate__(self, state: dict[str, object]) -> None:
         # Fail at the unpickle site if the state comes from a different
         # Lexicon field layout (version skew) -- silently loading it
         # would defer the failure to some distant attribute read.
+        # Message kept in sync with _types._guarded_setstate by design
+        # (layering keeps this module import-free of _types).
         expected = {f.name for f in dataclasses.fields(Lexicon)} - {"_cap_map"}
         if set(state) != expected:
             missing = ", ".join(sorted(expected - set(state))) or "none"

nameparser/_policy.py

@@ -28,6 +28,17 @@ class PatronymicRule(StrEnum):
 _NAME_ROLES = frozenset({Role.GIVEN, Role.MIDDLE, Role.FAMILY})
 
 
+def _reject_bare_string_order(value: object) -> None:
+    # tuple("gmf") would be ("g", "m", "f") -- catch the bare string
+    # with the same TypeError every other iterable field raises.
+    # Single-sourced: called from Policy AND PolicyPatch __post_init__.
+    if isinstance(value, str):
+        raise TypeError(
+            f"name_order must be an iterable of three Roles, "
+            f"not a bare string: {value!r}"
+        )
+
+
 @dataclass(frozen=True, slots=True)
 class Policy:
     name_order: tuple[Role, Role, Role] = GIVEN_FIRST
@@ -50,13 +61,7 @@ class Policy:
     __setstate__ = _guarded_setstate
 
     def __post_init__(self) -> None:
-        # tuple("gmf") would be ("g", "m", "f") -- catch the bare string
-        # with the same TypeError every other iterable field raises
-        if isinstance(self.name_order, str):
-            raise TypeError(
-                f"name_order must be an iterable of three Roles, "
-                f"not a bare string: {self.name_order!r}"
-            )
+        _reject_bare_string_order(self.name_order)
         order = tuple(self.name_order)
         if len(order) != 3 or set(order) != _NAME_ROLES:
             raise ValueError(
@@ -203,11 +208,7 @@ def __post_init__(self) -> None:
         # coerce a list at apply time, but the patch itself (and any
         # Locale holding it) must already be hashable.
         if self.name_order is not UNSET:
-            if isinstance(self.name_order, str):
-                raise TypeError(
-                    f"name_order must be an iterable of three Roles, "
-                    f"not a bare string: {self.name_order!r}"
-                )
+            _reject_bare_string_order(self.name_order)
             object.__setattr__(self, "name_order", tuple(self.name_order))
         for f in dataclasses.fields(self):
             if f.metadata.get("compose") != "union":