Index: src/Parser/parser.yy
===================================================================
--- src/Parser/parser.yy	(revision 68b52b006e663115432e37a155c3be322899e8da)
+++ src/Parser/parser.yy	(revision 1d7120877bb2a57ce230731420cd13e6e42a563e)
@@ -635,7 +635,10 @@
 postfix_expression:
 	primary_expression
-	| postfix_expression '[' assignment_expression ',' comma_expression ']'
-		// { $$ = new ExpressionNode( build_binary_val( OperKinds::Index, $1, new ExpressionNode( build_binary_val( OperKinds::Index, $3, $5 ) ) ) ); }
-		{ SemanticError( yylloc, "New array subscript is currently unimplemented." ); $$ = nullptr; }
+	| postfix_expression '[' assignment_expression ',' tuple_expression_list ']'
+			// Historic, transitional: Disallow commas in subscripts.
+			// Switching to this behaviour may help check if a C compatibilty case uses comma-exprs in subscripts.
+		// { SemanticError( yylloc, "New array subscript is currently unimplemented." ); $$ = nullptr; }
+			// Current: Commas in subscripts make tuples.
+		{ $$ = new ExpressionNode( build_binary_val( OperKinds::Index, $1, new ExpressionNode( build_tuple( (ExpressionNode *)($3->set_last( $5 ) ) )) ) ); }
 	| postfix_expression '[' assignment_expression ']'
 		// CFA, comma_expression disallowed in this context because it results in a common user error: subscripting a