1 files changed, 32 insertions, 0 deletions
diff --git a/js/src/tests/non262/lexical-environment/unscopables-strict.js b/js/src/tests/non262/lexical-environment/unscopables-strict.js
new file mode 100644
index 0000000000..fd0413ed7b
--- /dev/null
+++ b/js/src/tests/non262/lexical-environment/unscopables-strict.js
@@ -0,0 +1,32 @@
+// Strict assignment to the name of a property that's masked by @@unscopables
+// throws a ReferenceError.
+
+let env = {k: 1};
+let f;
+with (env) {
+    f = function () {
+        "use strict";
+        k = 2;
+    };
+}
+
+f();
+assertEq(env.k, 2);
+
+env[Symbol.unscopables] = {k: true};
+assertThrowsInstanceOf(f, ReferenceError);
+
+// @@unscopables is tested when the LHS of assignment is evaluated, so there is
+// no effect on the assignment if it is changed while evaluating the RHS.
+let g;
+with (env) {
+    g = function () {
+        "use strict";
+        k = (env[Symbol.unscopables].k = true, 3);
+    }
+}
+env[Symbol.unscopables].k = false;
+g();
+assertEq(env.k, 3);
+
+reportCompare(0, 0);