如何确定FieldDeclarationSyntax的类型是否是Roslyn中的接口？

Question

假设有一个类包含接口类型的私有字段。在使用Roslyn分析上面的代码时，如何确定FieldDeclarationSyntax背后的类型是否是一个接口？使用下面的代码来检索字段声明的ISymbol，我找不到像IsInterface或类似的任何属性。

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

public class SampleClass
{
    public static void Main()
    {
        var str =
            @"
            namespace Sample
            {
                public interface IBar
                {
                    void Do();
                }

                public class Foo
                {
                    private IBar _bar;
                }
            }";

        var syntaxTree = SyntaxFactory.ParseSyntaxTree(str);

        var compilation = CSharpCompilation.Create("Sample", new[] { syntaxTree });

        var semanticModel = compilation.GetSemanticModel(syntaxTree, true);

        var classDeclarationSyntax =
        semanticModel.SyntaxTree.GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().First();

        var fieldDeclarationSyntax = classDeclarationSyntax.DescendantNodes().OfType<FieldDeclarationSyntax>().First();

        var declaredSymbol = semanticModel.GetDeclaredSymbol(fieldDeclarationSyntax.Declaration.Variables.First());

        // declaredSymbol (ISymbol) contains properties like IsDefinition, IsVirtual etc. but nothing like IsInterface.
    }
}

Answer 1

在fieldDeclarationSyntax.Declaration.Type上调用GetTypeInfo最终完成了这个技巧。完整的工作示例：

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

public class SanpleClass
{
    public static void Main()
    {
        var str =
            @"
            namespace Sample
            {
                public interface IBar
                {
                    void Do();
                }

                public class Foo
                {
                    private IBar _bar;
                }
            }";

        var syntaxTree = SyntaxFactory.ParseSyntaxTree(str);

        var compilation = CSharpCompilation.Create("Sample", new[] { syntaxTree });

        var semanticModel = compilation.GetSemanticModel(syntaxTree, true);

        var classDeclarationSyntax =
            semanticModel.SyntaxTree.GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().First();

        var fieldDeclarationSyntax = classDeclarationSyntax.DescendantNodes().OfType<FieldDeclarationSyntax>().First();

        var typeKind = semanticModel.GetTypeInfo(fieldDeclarationSyntax.Declaration.Type).Type.TypeKind;

        var isInterface = typeKind == TypeKind.Interface;

        Console.WriteLine($"Is Interface: {isInterface}");
    }
}