1 files changed, 26 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/debug/Environment-bug-1431461.js b/js/src/jit-test/tests/debug/Environment-bug-1431461.js
new file mode 100644
index 0000000000..188f3ee5a7
--- /dev/null
+++ b/js/src/jit-test/tests/debug/Environment-bug-1431461.js
@@ -0,0 +1,26 @@
+// Check that duplicate bindings are not created for let/const variables.
+
+let g = newGlobal({newCompartment: true});
+let dbg = new Debugger(g);
+
+g.eval(`
+function f(x, y=x) {
+    let z = "Z";
+    debugger;
+    return x + y + z;
+}
+`);
+
+let hits = 0;
+let names = [];
+
+dbg.onDebuggerStatement = frame => {
+    hits++;
+    for (let env = frame.environment; env.type !== "object"; env = env.parent) {
+        names.push(...env.names());
+    }
+};
+
+assertEq(g.f("X", "Y"), "XYZ");
+assertEq(hits, 1);
+assertEq(names.sort().join(", "), "arguments, x, y, z");