QL code and tests for C#/C++/JavaScript.

csharp/ql/test/query-tests/Useless Code/DefaultToString/DefaultToString.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Text;
+
+class DefaultToString
+{
+    void M()
+    {
+        var d = new DefaultToString();
+        Console.WriteLine(d.ToString()); // BAD
+        var s = "hello " + d; // BAD
+
+        new A().ToString(); // GOOD
+        new B().ToString(); // GOOD
+
+        var ints = new int[] { 1, 2, 3 };
+        Console.WriteLine(ints); // BAD
+        Console.WriteLine(string.Join(", ", ints)); // GOOD
+
+        s = "hello " + ints; // BAD
+        s = "hello " + string.Join(", ", ints); // GOOD
+
+        s = "" + NullableE; // GOOD
+
+        E e = E.A;
+        Console.WriteLine(e); // GOOD
+
+        C c = new D();
+        Console.WriteLine(c); // GOOD
+    }
+
+    class A
+    {
+        override public string ToString() { return "hello"; }
+    }
+
+    class B : A { }
+
+    enum E { A, B }
+
+    E? NullableE { get; set; }
+
+    class C { }
+
+    class D : C
+    {
+        override public string ToString() { return "D"; }
+    }
+}
+
+// semmle-extractor-options: /r:System.Runtime.Extensions.dll