add ellipsis token

test/corpus/for_expressions.txt

@@ -32,6 +32,33 @@ foo = [for i, v in ["a", "b"]: i]
 
 ---
 
+(config_file 
+  (body 
+    (attribute 
+      (identifier) 
+      (expression 
+        (expr_term 
+          (for_expr 
+            (for_tuple_expr 
+              (for_intro 
+              (identifier) 
+              (identifier) 
+              (expression 
+                (expr_term 
+                  (collection_value 
+                    (tuple 
+                      (expression (expr_term (literal_value (string_lit)))) 
+                      (expression (expr_term (literal_value (string_lit)))))))))
+              (expression (expr_term (variable_expr (identifier))))))))))) 
+
+==================
+for tuple expression with predicate
+==================
+
+foo = [for i, v in ["a", "b", "c"]: v if pred(i)]
+
+---
+
 (config_file 
   (body 
     (attribute