private IEnumerable <SyntaxTrivia> DescendantTriviaImpl(TextSpan span, Func <SyntaxNode, bool> descendIntoChildren = null, bool descendIntoTrivia = false)
 {
     return(descendIntoTrivia
         ? DescendantTriviaIntoTrivia(span, descendIntoChildren)
         : DescendantTriviaOnly(span, descendIntoChildren));
 }
 private IEnumerable <SyntaxNode> DescendantNodesAndTokensImpl(TextSpan span, Func <SyntaxNode, bool> descendIntoChildren, bool descendIntoTrivia, bool includeSelf)
 {
     return(descendIntoTrivia
         ? DescendantNodesAndTokensIntoTrivia(span, descendIntoChildren, includeSelf)
         : DescendantNodesAndTokensOnly(span, descendIntoChildren, includeSelf));
 }