1 files changed, 46 insertions, 0 deletions
diff --git a/js/src/tests/ecma_2017/Statements/for-in-with-assignment-semantics.js b/js/src/tests/ecma_2017/Statements/for-in-with-assignment-semantics.js
new file mode 100644
index 000000000..f1dbb3438
--- /dev/null
+++ b/js/src/tests/ecma_2017/Statements/for-in-with-assignment-semantics.js
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const unreachable = () => { throw "unreachable"; };
+
+// var-initializer expression is executed before for-in expression.
+var log = "";
+for (var x = (log += "head") in (log += "|expr", null)) unreachable();
+assertEq(log, "head|expr");
+
+log = "";
+for (var x = (log += "head") in (log += "|expr", {})) unreachable();
+assertEq(log, "head|expr");
+
+
+// for-in expression isn't executed when var-initializer throws exception.
+function ExpectedError() {}
+assertThrowsInstanceOf(() => {
+    var throwErr = () => { throw new ExpectedError(); };
+    for (var x = throwErr() in unreachable()) unreachable();
+}, ExpectedError);
+
+
+// Ensure environment operations are performed correctly.
+var scope = new Proxy({x: 0}, new Proxy({}, {
+    get(t, pk, r) {
+        log += pk + "|";
+    }
+}));
+
+log = "";
+with (scope) {
+    for (var x = 0 in {}) ;
+}
+assertEq(log, "has|get|set|getOwnPropertyDescriptor|defineProperty|");
+
+log = "";
+with (scope) {
+    for (var x = 0 in {p: 0}) ;
+}
+assertEq(log, "has|get|set|getOwnPropertyDescriptor|defineProperty|".repeat(2));
+
+
+if (typeof reportCompare === "function")
+    reportCompare(true, true);