title: Should underscore(_) prefix be added to method input parameters in Dart?
body: <p>Both compiles but I wonder which version is correct?</p>
  
  <pre><code>  int add(int _a, int _b) {
      return _a + _b;
    }
  </code></pre>
  
  <p>or</p>
  
  <pre><code>  int add(int a, int b) {
      return a + b;
    }
  </code></pre>