JS: Expose data flow node for field declaration

javascript/ql/src/semmle/javascript/dataflow/DataFlow.qll

@@ -1308,6 +1308,22 @@ module DataFlow {
     nd = TFunctionReturnNode(function)
   }
 
+  /**
+   * INTERNAL: Do not use outside standard library.
+   *
+   * Gets a data flow node unique to the given field declaration.
+   *
+   * Note that this node defaults to being disconnected from the data flow
+   * graph, as the individual property reads and writes affecting the field are
+   * analyzed independently of the field declaration.
+   *
+   * Certain framework models may need this node to model the behavior of
+   * class and field decorators.
+   */
+  DataFlow::Node fieldDeclarationNode(FieldDeclaration field) {
+    result = TPropNode(field)
+  }
+
   /**
    * Gets the data flow node corresponding the given l-value expression, if
    * such a node exists.

javascript/ql/src/semmle/javascript/frameworks/Angular2.qll

@@ -293,7 +293,7 @@ module Angular2 {
       exists(FieldDeclaration f |
         f.getName() = name and
         f.getDeclaringClass().flow() = this and
-        result = f.getNameExpr().flow()
+        result = DataFlow::fieldDeclarationNode(f)
       )
     }