1 files changed, 44 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/ion/fold-in.js b/js/src/jit-test/tests/ion/fold-in.js
new file mode 100644
index 0000000000..4e0c54cd5d
--- /dev/null
+++ b/js/src/jit-test/tests/ion/fold-in.js
@@ -0,0 +1,44 @@
+// Singleton
+function f() {
+    var res = 0;
+    for (var i=0; i<500; i++)
+	res += ("abcd" in Math);
+    return res;
+}
+assertEq(f(), 0);
+Math.abcd = 3;
+assertEq(f(), 500);
+delete Math.abcd;
+assertEq(f(), 0);
+
+// Non-singleton
+function O(x) { if (x) this.x = 1; }
+
+var arr = [];
+for (var i=0; i<4; i++)
+    arr.push(new O(i % 2));
+
+function g(arr) {
+    var res = 0;
+    for (var i=0; i<500; i++) {
+	var o = arr[i % arr.length];
+	res += "x" in o;
+	res += "abcd" in o;
+    }
+    return res;
+}
+assertEq(g(arr), 250);
+arr[0].abcd = 3;
+assertEq(g(arr), 375);
+
+function testPrimitive() {
+    var x = 7;
+    var c = 0;
+    for (var i=0; i<5; i++) {
+	try {
+	    "z" in x;
+	} catch(e) { c++; }
+    }
+    assertEq(c, 5);
+}
+testPrimitive();