rm push/pop

tests/suite.cm

@@ -2918,7 +2918,7 @@ return {
     test_arrfor_with_index: function() {
         var arr = ["a", "b", "c"]
         var indices = []
-        arrfor(arr, (x, i) => { push(indices, i) })
+        arrfor(arr, (x, i) => { indices[] = i })
         if (indices[0] != 0 || indices[2] != 2) return "arrfor with index failed"
     },
 
@@ -2931,7 +2931,7 @@ return {
     test_arrfor_mutation: function() {
         var arr = [1, 2, 3]
         var results = []
-        arrfor(arr, x => { push(results, x * 2) })
+        arrfor(arr, x => { results[] = x * 2 })
         if (results[0] != 2 || results[1] != 4 || results[2] != 6) return "arrfor mutation failed"
     },