LibJS: Enable now working tests for duplicated variable declarations

Author: https://github.com/davidot
Commit: 10bf91a293
Pull-request: https://github.com/SerenityOS/serenity/pull/10483
Issue: https://github.com/SerenityOS/serenity/issues/8198
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibJS/Tests/var-scoping.js

@@ -15,3 +15,21 @@ test("basic functionality", () => {
     }
     expect(caught_exception).not.toBeUndefined();
 });
+
+test("Issue #8198 arrow function escapes function scope", () => {
+    const b = 3;
+
+    function f() {
+        expect(b).toBe(3);
+        (() => {
+            expect(b).toBe(3);
+            var a = "wat";
+            eval("var b=a;");
+            expect(b).toBe("wat");
+        })();
+        expect(b).toBe(3);
+    }
+
+    f();
+    expect(b).toBe(3);
+});