1 files changed, 38 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/debug/optimized-out-arrow-this.js b/js/src/jit-test/tests/debug/optimized-out-arrow-this.js
new file mode 100644
index 0000000000..adc1702fa1
--- /dev/null
+++ b/js/src/jit-test/tests/debug/optimized-out-arrow-this.js
@@ -0,0 +1,38 @@
+var g = newGlobal({newCompartment: true});
+var dbg = new Debugger(g);
+
+g.eval(`
+function f() {
+  // |this| in arrow-functions refers to the |this| binding in outer functions.
+  // So when |frame.eval("this")| is executed, the outer |this| binding should
+  // be returned, unless it has been optimised out.
+  (() => {})();
+
+  // Ensure a |this| binding is created for |f|.
+  return this;
+}
+`);
+
+var errors = [];
+
+function enterFrame(frame) {
+  // Disable the handler so we don't call it recursively through |frame.eval|.
+  dbg.onEnterFrame = undefined;
+
+  // Store the error when resolving |this| was unsuccessful.
+  var r = frame.eval("this");
+  if (r.throw) {
+    errors.push(r.throw);
+  }
+
+  // Re-enable the handler.
+  dbg.onEnterFrame = enterFrame;
+};
+
+dbg.onEnterFrame = enterFrame;
+
+g.f();
+
+assertEq(errors.length, 1);
+assertEq(errors[0].unsafeDereference().toString(),
+         "Error: variable 'this' has been optimized out");