错误日志
升级到Unity2018之后，使用 Open C# Project 打开VS工程，出现报错，无法启动VS。
错误日志如下：
ArgumentException: Value does not fall within the expected range.
SyntaxTree.VisualStudio.Unity.Bridge.CompilationUnit.LanguageOf (SyntaxTree.VisualStudio.Unity.Bridge.CompilationUnit unit)
SyntaxTree.VisualStudio.Unity.Bridge.CompilationUnit.CompilationUnits (System.String method)
SyntaxTree.VisualStudio.Unity.Bridge.CompilationUnit.CompilationUnits ()
SyntaxTree.VisualStudio.Unity.Bridge.ProjectSystem.UnitySolutionBuilder..ctor ()
SyntaxTree.VisualStudio.Unity.Bridge.ProjectSystem.UnitySolutionBuilder.CreateSolutionFromAssetDatabase ()
SyntaxTree.VisualStudio.Unity.Bridge.ProjectFilesGenerator.GenerateProject ()
SyntaxTree.VisualStudio.Unity.Bridge.ProjectFilePostprocessor.OnPreGeneratingCSProjectFiles ()
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.AssetPostprocessingInternal.OnPreGeneratingCSProjectFiles () (at C:/buildslave/unity/build/Editor/Mono/AssetPostprocessor.cs:194)
UnityEditor.VisualStudioIntegration.SolutionSynchronizer.Sync () (at C:/buildslave/unity/build/Editor/Mono/VisualStudioIntegration/SolutionSynchronizer.cs:207)
UnityEditor.SyncVS.SyncSolution () (at C:/buildslave/unity/build/Editor/Mono/SyncProject.cs:190)
UnityEditor.SyncVS.SyncAndOpenSolution () (at C:/buildslave/unity/build/Editor/Mono/SyncProje
Unity Down Assistant
在Unity的Download Assistant中进行下载VS组件
vs_Enterprise安装Unity组件
在vs_Enterprise.exe 中安装unity的组件也是失败
其它排查方法
怀疑是Unity的问题，重新安装 Unity，问题无法解决。
更换其它版本的unity，比如2018.2.9f1，问题无法解决。
解决方案
如果是VS2015，则可以通过下载新版本的Visual Studio Tools For Unity 进行更新。（公司机器测试通过）
如果是VS2013，下载新版本的Visual Studio Tools For Unity 更新后也是失败（家里机器）。
更新VS2017，问题得到解决。