style

ikonst · ikonst · commit 6721b51c67d6 · 2023-04-13T21:14:30.000-04:00
diff --git a/mypy/plugins/attrs.py b/mypy/plugins/attrs.py
@@ -971,24 +971,21 @@ def _get_expanded_attr_types(
     parent_typ: ProperType,
 ) -> list[Mapping[str, Type]] | None:
     """
-    For a given type, determine what attrs classes it can be, and return the field types for each class.
+    For a given type, determine what attrs classes it can be: for each class, return the field types.
     For generic classes, the field types are expanded.
     If the type contains Any or a non-attrs type, returns None; in the latter case, also reports an error.
     """
     if isinstance(typ, AnyType):
         return None
     if isinstance(typ, UnionType):
         types = []
-        had_errors = False
         for item in typ.relevant_items():
             item = get_proper_type(item)
             item_types = _get_expanded_attr_types(ctx, item, item, parent_typ)
-            if isinstance(item_types, list):
+            if types is not None and item_types is not None:
                 types += item_types
             else:
-                had_errors = True
-        if had_errors:
-            return None
+                types = None  # but keep iterating to emit all errors
         return types
     if isinstance(typ, TypeVarType):
         return _get_expanded_attr_types(
