Index: src/Parser/parser.yy
===================================================================
--- src/Parser/parser.yy	(revision cbbd8fd770714fe40fffe90e2b2b492682101bfb)
+++ src/Parser/parser.yy	(revision 393d59a90f59576e7d77b5d3c2e7b153655897dd)
@@ -10,6 +10,6 @@
 // Created On       : Sat Sep  1 20:22:55 2001
 // Last Modified By : Peter A. Buhr
-// Last Modified On : Sat May 23 09:22:36 2020
-// Update Count     : 4499
+// Last Modified On : Thu May 28 12:11:45 2020
+// Update Count     : 4500
 //
 
@@ -1332,5 +1332,6 @@
 	cast_expression
 	| cast_expression_list ',' cast_expression
-		{ $$ = (ExpressionNode *)($1->set_last( $3 )); }
+		// { $$ = (ExpressionNode *)($1->set_last( $3 )); }
+		{ SemanticError( yylloc, "List of mutex member is currently unimplemented." ); $$ = nullptr; }
 	;