Fix bug 73940.

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index ef82674d789e2460e10cc2cf5fc995a7ae6bdbc2..182cc7a16b65cecab8c74cd2d0a481f8e5126f81 100644
--- a/src/array.js
+++ b/src/array.js
@@ -1018,13 +1018,13 @@ function ArrayIndexOf(element, index) {
   }
   var min = index;
   var max = length;
-  if (UseSparseVariant(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, length);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by length already.
       // Fall through to loop below.
     } else {
@@ -1074,13 +1074,13 @@ function ArrayLastIndexOf(element, index) {
   }
   var min = 0;
   var max = index;
-  if (UseSparseVariant(this, length, true)) {
+  if (UseSparseVariant(this, length, IS_ARRAY(this))) {
     var intervals = %GetArrayKeys(this, index + 1);
     if (intervals.length == 2 && intervals[0] < 0) {
       // A single interval.
       var intervalMin = -(intervals[0] + 1);
       var intervalMax = intervalMin + intervals[1];
-      min = MAX(min, intervalMin);
+      if (min < intervalMin) min = intervalMin;
       max = intervalMax;  // Capped by index already.
       // Fall through to loop below.
     } else {