1 files changed, 39 insertions, 0 deletions
diff --git a/js/src/tests/non262/lexical-environment/unscopables-proto.js b/js/src/tests/non262/lexical-environment/unscopables-proto.js
new file mode 100644
index 0000000000..dbbfb712d3
--- /dev/null
+++ b/js/src/tests/non262/lexical-environment/unscopables-proto.js
@@ -0,0 +1,39 @@
+// @@unscopables treats properties found on prototype chains the same as other
+// properties.
+
+const x = "global x";
+const y = "global y";
+
+// obj[@@unscopables].x works when obj.x is inherited via the prototype chain.
+let proto = {x: "object x", y: "object y"};
+let env = Object.create(proto);
+env[Symbol.unscopables] = {x: true, y: false};
+with (env) {
+    assertEq(x, "global x");
+    assertEq(delete x, false);
+    assertEq(y, "object y");
+}
+assertEq(env.x, "object x");
+
+// @@unscopables works if is inherited via the prototype chain.
+env = {
+    x: "object",
+    [Symbol.unscopables]: {x: true, y: true}
+};
+for (let i = 0; i < 50; i++)
+    env = Object.create(env);
+env.y = 1;
+with (env) {
+    assertEq(x, "global x");
+    assertEq(y, "global y");
+}
+
+// @@unscopables works if the obj[@@unscopables][id] property is inherited.
+env = {
+    x: "object",
+    [Symbol.unscopables]: Object.create({x: true})
+};
+with (env)
+    assertEq(x, "global x");
+
+reportCompare(0, 0);