public void f()
        {
            var input =
                @"#r ""./a/b.dll""
using System;
";
            var tree      = CSharpSyntaxTree.ParseText(input);
            var root      = (CompilationUnitSyntax)tree.GetRoot();
            var collector = new ReferenceDirectiveTriviaCollector();

            collector.Visit(root);
            Assert.Equal(1, collector.Reference.Count);
            Assert.Equal("./a/b.dll", collector.Reference.First());
        }
        public void g()
        {
            var input =
                @"#r ""./a/b.dll""
#r ""./c/d.dll""
#r ""./e.dll""
using System;
";
            var tree      = CSharpSyntaxTree.ParseText(input);
            var root      = (CompilationUnitSyntax)tree.GetRoot();
            var collector = new ReferenceDirectiveTriviaCollector();

            collector.Visit(root);
            var ret = new string[] { "./a/b.dll", "./c/d.dll", "./e.dll" }.ToHashSet();

            Assert.Equal(3, collector.Reference.Count);
            foreach (var x in collector.Reference)
            {
                Assert.Contains(x, ret);
            }
        }