C#: Update ContentDataFlow test

Illustrates missing flow when the sink is inside a method that is also part of
a `subpath`.

Author: hvitved

csharp/ql/test/library-tests/dataflow/content/ContentFlow.cs

@@ -16,16 +16,36 @@ public class B
     public void M(A a, B b)
     {
         var a1 = new A();
-        Sink(a1.FieldA.FieldB);
+        Sink(Through(a1.FieldA.FieldB));
 
         a.FieldA.FieldB = new B();
-        Sink(a);
+        Sink(Through(a));
 
         var a2 = new A();
         b.FieldB.FieldA = a2.FieldB.FieldA;
-        Sink(b);
+        Sink(Through(b));
+
+        Sink(Through(Out()));
+
+        In(new A().FieldA.FieldB);
     }
 
     public static void Sink<T>(T t) { }
 
+    public T Through<T>(T t)
+    {
+        Sink(t);
+        return t;
+    }
+
+    public void In<T>(T t)
+    {
+        Sink(t);
+    }
+
+    public B Out()
+    {
+        var a = new A();
+        return a.FieldA.FieldB;
+    }
 }

csharp/ql/test/library-tests/dataflow/content/ContentFlow.expected

@@ -1,3 +1,5 @@
-| ContentFlow.cs:18:18:18:24 | object creation of type A | field FieldB.field FieldA. | ContentFlow.cs:19:14:19:29 | access to field FieldB |  | true |
-| ContentFlow.cs:21:27:21:33 | object creation of type B |  | ContentFlow.cs:22:14:22:14 | access to parameter a | field FieldA.field FieldB. | true |
-| ContentFlow.cs:24:18:24:24 | object creation of type A | field FieldA.field FieldB. | ContentFlow.cs:26:14:26:14 | access to parameter b | field FieldB.field FieldA. | true |
+| ContentFlow.cs:18:18:18:24 | object creation of type A | field FieldB.field FieldA. | ContentFlow.cs:19:14:19:38 | call to method Through<B> |  | true |
+| ContentFlow.cs:21:27:21:33 | object creation of type B |  | ContentFlow.cs:22:14:22:23 | call to method Through<A> | field FieldA.field FieldB. | true |
+| ContentFlow.cs:24:18:24:24 | object creation of type A | field FieldA.field FieldB. | ContentFlow.cs:26:14:26:23 | call to method Through<B> | field FieldB.field FieldA. | true |
+| ContentFlow.cs:30:12:30:18 | object creation of type A | field FieldB.field FieldA. | ContentFlow.cs:43:14:43:14 | access to parameter t |  | true |
+| ContentFlow.cs:48:17:48:23 | object creation of type A | field FieldB.field FieldA. | ContentFlow.cs:28:14:28:27 | call to method Through<B> |  | true |