title: Ensure a method implements an interface WITHOUT being an explicit implementation: is there a "EnsureImplementsInterface" ReSharper attribute?
body: <p>Given the following example code, I wish to be able to annotate that a method is absolutely expected to implement an interface.</p>
  
  <pre><code>interface X {
      void a(string x);
  }
  
  class Y : X {
      [EnsureImplementsInterface]
      public void a(string x) { .. }
  
      [EnsureImplementsInterface] // Should result in some form of "error"
      public void a(object x) { .. }
  }
  </code></pre>
  
  <p>An explicit interface implementation is not suitable because the main usage will be via 'var' using statements; furthermore, changing to an explicit interface would break existing contracts.</p>
  
  <p>The <code>override</code> keyword is not suitable/usable, because no method is being overridden and C# just doesn't work like that.</p>