C#/Java: Add some examples of missing synthetic field element flow.

Author: michaelnebel

csharp/ql/test/utils/modelgenerator/dataflow/Summaries.cs

@@ -839,6 +839,23 @@ public void SetProp2(string v)
     }
 }
 
+public class SyntheticCollections
+{
+    private object[] array;
+
+    // summary=Models;SyntheticCollections;false;SyntheticCollections;(System.Object[]);;Argument[0].Element;Argument[this];taint;df-generated
+    public SyntheticCollections(object[] array)
+    {
+        this.array = array;
+    }
+
+    // summary=Models;SyntheticCollections;false;GetElement;(System.Int32);;Argument[this];ReturnValue;taint;df-generated
+    public object GetElement(int index)
+    {
+        return array[index];
+    }
+}
+
 public class Fanout
 {
 

java/ql/test/utils/modelgenerator/dataflow/p/SyntheticCollections.java

@@ -0,0 +1,15 @@
+package p;
+
+public class SyntheticCollections {
+  private String[] array;
+
+  // summary=p;SyntheticCollections;true;SyntheticCollections;(String[]);;Argument[0].ArrayElement;Argument[this];taint;df-generated
+  public SyntheticCollections(String[] array) {
+    this.array = array;
+  }
+
+  // summary=p;SyntheticCollections;true;getElement;(Integer);;Argument[this];ReturnValue;taint;df-generated
+  public String getElement(Integer index) {
+    return array[index];
+  }
+}