protected internal virtual void PostWalk(EnvironmentExpression node) { }
 protected internal virtual void PostWalk(EnvironmentExpression node)
 {
 }
 // EnvironmentExpression
 protected internal virtual bool Walk(EnvironmentExpression node) { return true; }
 // EnvironmentExpression
 protected internal virtual bool Walk(EnvironmentExpression node)
 {
     return(true);
 }