C#: Add viable callable test cases for statics in interfaces.

Author: michaelnebel

csharp/ql/test/library-tests/dispatch/ViableCallable.cs

@@ -503,4 +503,75 @@ void Run(C19 c)
         // Viable callables: C19.op_CheckedExplicit()
         var n2 = checked((int)c);
     }
-}
+}
+
+public interface I3<T> where T : I3<T>
+{
+    static abstract T operator +(T x, T y);
+    static abstract T operator checked +(T x, T y);
+
+    static abstract T operator -(T x, T y);
+    static virtual T operator checked -(T x, T y) => throw null;
+
+    static virtual T operator *(T x, T y) => throw null;
+    static virtual T operator checked *(T x, T y) => throw null;
+
+    static virtual T operator /(T x, T y) => throw null;
+    static virtual T operator checked /(T x, T y) => throw null;
+
+    void M11();
+
+    virtual void M12() => throw null;
+
+    virtual void M13() => throw null;
+}
+
+public class C20 : I3<C20>
+{
+    public static C20 operator +(C20 x, C20 y) => throw null;
+    public static C20 operator checked +(C20 x, C20 y) => throw null;
+
+    public static C20 operator -(C20 x, C20 y) => throw null;
+
+    public static C20 operator /(C20 x, C20 y) => throw null;
+    public static C20 operator checked /(C20 x, C20 y) => throw null;
+
+    public void M11() { }
+    public void M12() { }
+
+    void Run<T>(T c) where T : I3<T>
+    {
+        // Viable callables: C20.op_Addition(). MISSING: C20.op_Addition()
+        var c1 = c + c;
+
+        // Viable callables: C20.op_CheckedAddition(). MISSING: C20.op_CheckedAddition()
+        var c2 = checked(c + c);
+
+        // Viable callables: C20.op_Subtraction(). Missing: C20.op_Subtraction()
+        var c3 = c - c;
+
+        // Viable callables: I3<C20>.op_CheckedSubtraction().
+        var c4 = checked(c - c);
+
+        // Viable callables: I3<C20>.op_Multiply().
+        var c5 = c * c;
+
+        // Viable callables: I3<C20>.op_CheckedMultiply().
+        var c6 = checked(c * c);
+
+        // Viable callables: {C20,I3<C20>}.op_Division(). MISSING: C20.op_Division()
+        var c7 = c / c;
+
+        // Viable callables: {C20,I3<C20>}.op_CheckedDivision(). MISSING: C20.op_CheckedDivision()
+        var c8 = checked(c / c);
+
+        // Viable callables: C20.M11. MISSING: C20.M11()
+        c.M11();
+
+        // Viable callables: {C20,I3<C20>}.M12(). MISSING: C20.M12()
+        c.M12();
+
+        // Viable callables: I3<C20>.M13()
+        c.M13();
+    }
+}