1 files changed, 12 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/coercions.py b/lib/sqlalchemy/sql/coercions.py
index be412c770..588c485ae 100644
--- a/lib/sqlalchemy/sql/coercions.py
+++ b/lib/sqlalchemy/sql/coercions.py
@@ -52,6 +52,18 @@ def _document_text_coercion(paramname, meth_rst, param_rst):
     )
 
 
+def _expression_collection_was_a_list(attrname, fnname, args):
+    if args and isinstance(args[0], (list, set)) and len(args) == 1:
+        util.warn_deprecated_20(
+            'The "%s" argument to %s() is now passed as a series of '
+            "positional "
+            "elements, rather than as a list. " % (attrname, fnname)
+        )
+        return args[0]
+    else:
+        return args
+
+
 def expect(role, element, apply_propagate_attrs=None, argname=None, **kw):
     if (
         role.allows_lambda