可靠地将类型符号 (ITypeSymbol) 与 Roslyn 进行比较

Question

我正在尝试在以下情况下可靠地比较 ITypeSymbol 的两个实例，这是最简单和最直接的方式（我在一个更大的项目中遇到了这些问题，并试图尽可能地简化它）：

我已经用这个 SyntaxTree 进行了 CSharpCompilation：

  namespace MyAssembly
  {
    public class Foo
    {
      public Foo(Foo x)
      {
      }
    }
  }

我们正在使用CSharpSyntaxRewriter 遍历树，更改类并更新Compilation。在第一次运行中，我们记住了第一个构造函数参数的ITypeSymbol（在这种情况下是类本身的类型）。 更新编译后，我们再次调用相同的重写器并再次从构造函数参数中获取 ITypeSymbol。 之后，我比较了两个 ITypeSymbol，我希望它们代表相同的类型 MyAssembly.Foo。

我的第一个比较方法只是调用 ITypeSymbol.Equals() 方法，但它返回了 false。它基本上返回false，因为我们更改了编译并同时得到了一个新的SemanticModel。如果我们不这样做，Equals() 方法实际上会返回 true。

比较DeclaringSyntaxReferences（这里也提到How to compare type symbols (ITypeSymbol) from different projects in Roslyn?）返回false，因为我们同时更改了Foo 类本身。如果构造函数参数的类型为Bar 并且我们重写Bar，则行为将相同。要验证这一点，只需取消注释该行

//RewriteBar(rewriter, compilation, resultTree); 

并将代码示例中的构造函数参数类型替换为Bar。

结论： ITypeSymbol.Equals() 不适用于新的编译和语义模型，比较 DeclaringSyntaxReferences 不适用于我们同时更改的类型。 （我还使用一种外部程序集测试了该行为——在这种情况下，ITypeSymbol.Equals() 对我有用。）

所以我的问题是：

• 在所述情况下比较类型的预期方法是什么？
• 是否有一个包罗万象的解决方案，或者我必须有 混合/组合不同的方法来确定类型相等（也许 还采用完全限定名称的字符串表示 考虑）？

这是我可以重现问题的完整测试程序。只需复制、包含 Roslyn 引用并执行：

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace Demo.TypeSymbol
{
  class Program
  {
    static void Main(string[] args)
    {    
      var compilation = (CSharpCompilation) GetTestCompilation();

      var rewriter = new Rewriter(changeSomething: true);
      var tree = compilation.SyntaxTrees.First(); //first SyntaxTree is the one of class MyAssembly.Foo
      rewriter.Model = compilation.GetSemanticModel (tree);

      //first rewrite run
      var resultTree = rewriter.Visit (tree.GetRoot()).SyntaxTree;
      compilation = UpdateIfNecessary (compilation, rewriter, tree, resultTree);
      rewriter.Model = compilation.GetSemanticModel (resultTree);

      //just for demonstration; comment in to test behaviour when we are rewriting the class Bar -> in this case use Bar as constructor parameter in Foo
      //RewriteBar(rewriter, compilation, resultTree);

      //second rewrite run
      rewriter.Visit (resultTree.GetRoot());

      //now we want to compare the types...

      Console.WriteLine(rewriter.ParameterTypeFirstRun);
      Console.WriteLine(rewriter.ParameterTypeSecondRun);

      //=> types are *not* equal
      var typesAreEqual = rewriter.ParameterTypeFirstRun.Equals (rewriter.ParameterTypeSecondRun);
      Console.WriteLine("typesAreEqual:            " + typesAreEqual);

      //=> syntax references are not equal
      if(rewriter.ParameterTypeFirstRun.DeclaringSyntaxReferences.Any())
      {
        var syntaxReferencesAreEqual =
          rewriter.ParameterTypeFirstRun.DeclaringSyntaxReferences.First()
          .Equals(rewriter.ParameterTypeSecondRun.DeclaringSyntaxReferences.First());
        Console.WriteLine("syntaxReferencesAreEqual: " + syntaxReferencesAreEqual);
      }

      //==> other options??
    }

    private static CSharpCompilation UpdateIfNecessary(CSharpCompilation compilation, Rewriter rewriter, SyntaxTree oldTree, SyntaxTree newTree)
    {
      if (oldTree != newTree)
      {
        //update compilation as the syntaxTree changed
        compilation = compilation.ReplaceSyntaxTree(oldTree, newTree);
        rewriter.Model = compilation.GetSemanticModel(newTree);
      }
      return compilation;
    }

    /// <summary>
    /// rewrites the SyntaxTree of the class Bar, updates the compilation as well as the semantic model of the passed rewriter
    /// </summary>
    private static void RewriteBar(Rewriter rewriter, CSharpCompilation compilation, SyntaxTree firstSyntaxTree)
    {
      var otherRewriter = new Rewriter(true);
      var otherTree = compilation.SyntaxTrees.Last();
      otherRewriter.Model = compilation.GetSemanticModel(otherTree);
      var otherResultTree = otherRewriter.Visit(otherTree.GetRoot()).SyntaxTree;
      compilation = UpdateIfNecessary(compilation, otherRewriter, otherTree, otherResultTree);
      rewriter.Model = compilation.GetSemanticModel(firstSyntaxTree);
    }

    public class Rewriter : CSharpSyntaxRewriter
    {
      public SemanticModel Model { get; set; }
      private bool _firstRun = true;
      private bool _changeSomething;

      public ITypeSymbol ParameterTypeFirstRun { get; set; }
      public ITypeSymbol ParameterTypeSecondRun { get; set; }

      public Rewriter (bool changeSomething)
      {
        _changeSomething = changeSomething;
      }

      public override SyntaxNode VisitClassDeclaration(ClassDeclarationSyntax node)
      {
        node = (ClassDeclarationSyntax)base.VisitClassDeclaration(node);

        //remember the types of the parameter
        if (_firstRun)
          ParameterTypeFirstRun = GetTypeSymbol (node);
        else
          ParameterTypeSecondRun = GetTypeSymbol (node);

        _firstRun = false;

        //change something and return updated node
        if(_changeSomething)
          node = node.WithMembers(node.Members.Add(GetMethod()));
        return node;
      }

      /// <summary>
      /// Gets the type of the first parameter of the first method
      /// </summary>
      private ITypeSymbol GetTypeSymbol(ClassDeclarationSyntax classDeclaration)
      {
        var members = classDeclaration.Members;
        var methodSymbol = (IMethodSymbol) Model.GetDeclaredSymbol(members[0]);
        return methodSymbol.Parameters[0].Type;
      }

      private MethodDeclarationSyntax GetMethod()
      {
        return (MethodDeclarationSyntax)
          CSharpSyntaxTree.ParseText (@"public void SomeMethod(){ }").GetRoot().ChildNodes().First();
      }
    }

    private static SyntaxTree[] GetTrees()
    {
      var treeList = new List<SyntaxTree>();
      treeList.Add(CSharpSyntaxTree.ParseText(Source.Foo));
      treeList.Add(CSharpSyntaxTree.ParseText(Source.Bar));
      return treeList.ToArray();
    }

    private static Compilation GetTestCompilation()
    {
      var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);
      var refs = new List<PortableExecutableReference> { mscorlib };

      // I used this to test it with a reference to an external assembly
      // var testAssembly = MetadataReference.CreateFromFile(@"../../../Demo.TypeSymbol.TestAssembly/bin/Debug/Demo.TypeSymbol.TestAssembly.dll");
      // refs.Add (testAssembly);

      return CSharpCompilation.Create("dummyAssembly", GetTrees(), refs);
    }
  }

  public static class Source
  {
    public static string Foo => @"

      // for test with external assembly
      //using Demo.TypeSymbol.TestAssembly;

      namespace MyAssembly
      {
        public class Foo
        {
          public Foo(Foo x)
          {
          }
        }
      }
    ";

    public static string Bar => @"
      namespace MyAssembly
      {
        public class Bar
        {
          public Bar(int i)
          {
          }       
        }
      }
    ";
  }
}

Answer 1

一种可能性是调用SymbolFinder.FindSimilarSymbols，它会在您的新解决方案中为您提供一个按名称和其他一些属性匹配的符号。从那里你可以在你的新编译中使用 Equals。