// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#nullable disable

using System.Linq;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.UnitTests;
using Microsoft.CodeAnalysis.Test.Utilities;
using Roslyn.Test.Utilities;
using Xunit;
using Microsoft.CodeAnalysis.CSharp.Test.Utilities;

namespace Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests.Semantics
{
    /// <summary>
    /// Contains tests for expression-bodied members in the semantic model.
    /// </summary>
    [CompilerTrait(CompilerFeature.ExpressionBody)]
    public class ExpressionBodiedMemberTests : SemanticModelTestBase
    {
        [Fact]
        public void PartialMethods()
        {
            var comp = CreateCompilationWithMscorlib461(@"
public partial class C
{
    static partial void goo() => System.Console.WriteLine(""test"");
}

public partial class C
{
    static partial void goo();
}
");
            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot()
                .DescendantNodes()
                .OfType<MethodDeclarationSyntax>()
                .ElementAt(1);

            var gooDef = model.GetDeclaredSymbol(node).GetSymbol<SourceOrdinaryMethodSymbol>();
            Assert.NotNull(gooDef);
            Assert.True(gooDef.IsPartial);
            Assert.True(gooDef.IsPartialDefinition);
            Assert.False(gooDef.IsPartialImplementation);
            Assert.Null(gooDef.PartialDefinitionPart);

            var gooImpl = gooDef.PartialImplementationPart
                as SourceOrdinaryMethodSymbol;
            Assert.NotNull(gooImpl);
            Assert.True(gooImpl.IsPartial);
            Assert.True(gooImpl.IsPartialImplementation);
            Assert.False(gooImpl.IsPartialDefinition);
            Assert.True(gooImpl.IsExpressionBodied);
        }

        [Fact]
        public void ExprBodiedProp01()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class Program
{
    public int F = 1;
    public int P2 => /*<bind>*/this.F/*</bind>*/;
}
");
            comp.VerifyDiagnostics();
            var semanticInfo = GetSemanticInfoForTest<MemberAccessExpressionSyntax>(comp);

            Assert.Equal(SpecialType.System_Int32, semanticInfo.Type.SpecialType);
            Assert.Equal(SpecialType.System_Int32, semanticInfo.ConvertedType.SpecialType);
            Assert.Equal(ConversionKind.Identity, semanticInfo.ImplicitConversion.Kind);

            var semanticSymbol = semanticInfo.Symbol;
            var global = comp.GlobalNamespace;
            var program = global.GetTypeMember("Program");
            var field = program.GetMember<SourceFieldSymbol>("F");

            Assert.Equal(field, semanticSymbol.GetSymbol());

            Assert.Equal(CandidateReason.None, semanticInfo.CandidateReason);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);

            Assert.Equal(0, semanticInfo.MethodGroup.Length);

            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [Fact]
        public void ExprBodiedProp03()
        {
            var semanticInfo = GetSemanticInfoForTest<LiteralExpressionSyntax>(@"
using System;

class C
{
    int P => /*<bind>*/10/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            Assert.Null(semanticInfo.Symbol);
            Assert.True(semanticInfo.IsCompileTimeConstant);
            Assert.Equal(10, semanticInfo.ConstantValue);
        }

        [Fact]
        public void ExprBodiedProp04()
        {
            var tree = Parse(@"
using System;

class C
{
    int P => /*<bind>*/P/*</bind>*/;
}");
            var comp = CreateCompilationWithMscorlib461(new[] { tree });

            var info = GetSemanticInfoForTest<IdentifierNameSyntax>(comp);
            Assert.NotNull(info);
            var sym = Assert.IsType<SourcePropertySymbol>(info.Symbol.GetSymbol());
            var c = comp.GlobalNamespace.GetMember<NamedTypeSymbol>("C");
            Assert.Equal(c.GetMember<SourcePropertySymbol>("P"), sym);
        }

        [Fact]
        public void ExprBodiedIndexer01()
        {
            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(@"
using System;
class Program
{
    public int this[int i] => /*<bind>*/i/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            Assert.Equal(SpecialType.System_Int32, semanticInfo.Type.SpecialType);
            Assert.Equal("i", semanticInfo.Symbol.Name);
            Assert.Equal(SymbolKind.Parameter, semanticInfo.Symbol.Kind);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);
            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [Fact]
        public void ExprBodiedIndexer02()
        {
            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(@"
using System;
class C {}
class Program
{
    public C this[C c] => /*<bind>*/c/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            Assert.Equal("C", semanticInfo.Type.Name);
            Assert.Equal("c", semanticInfo.Symbol.Name);
            Assert.Equal(SymbolKind.Parameter, semanticInfo.Symbol.Kind);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);
            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [Fact]
        public void ExprBodiedIndexer03()
        {
            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(@"
class C
{
    public object this[string s] => /*<bind>*/s/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            Assert.Equal("s", semanticInfo.Symbol.Name);
            Assert.Equal(SymbolKind.Parameter, semanticInfo.Symbol.Kind);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);
            Assert.False(semanticInfo.IsCompileTimeConstant);

            Assert.Equal(SpecialType.System_String, semanticInfo.Type.SpecialType);
            Assert.Equal(SpecialType.System_Object, semanticInfo.ConvertedType.SpecialType);
        }

        [Fact]
        public void ExprBodiedIndexer04()
        {
            var semanticInfo = GetSemanticInfoForTest<InvocationExpressionSyntax>(@"
class C
{
    int M(int i) => i;
    long M(long l) => l;
    string this[string s] => /*<bind>*/M(s)/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            Assert.Equal(2, semanticInfo.CandidateSymbols.Length);
            Assert.Equal("System.Int32 C.M(System.Int32 i)", semanticInfo.CandidateSymbols[0].ToTestDisplayString());
            Assert.Equal("System.Int64 C.M(System.Int64 l)", semanticInfo.CandidateSymbols[1].ToTestDisplayString());
            Assert.Equal(CandidateReason.OverloadResolutionFailure, semanticInfo.CandidateReason);
        }

        [Fact]
        public void ExprBodiedIndexer05()
        {
            var semanticInfo = GetSemanticInfoForTest<SimpleNameSyntax>(@"
class C
{
    int this[int i] => /*<bind>*/i/*</bind>*/;
}");
            Assert.NotNull(semanticInfo);
            var sym = semanticInfo.Symbol;
            var accessor = Assert.IsType<SourcePropertyAccessorSymbol>(sym.ContainingSymbol.GetSymbol());
            var prop = accessor.AssociatedSymbol;
            Assert.IsType<SourcePropertySymbol>(prop);
        }

        [Fact]
        public void ExprBodiedFunc01()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class Program
{
    public int M(int i) => /*<bind>*/i/*</bind>*/;
}");
            comp.VerifyDiagnostics();

            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(comp);

            Assert.Equal(SpecialType.System_Int32, semanticInfo.Type.SpecialType);
            Assert.Equal(SpecialType.System_Int32, semanticInfo.ConvertedType.SpecialType);
            Assert.Equal(ConversionKind.Identity, semanticInfo.ImplicitConversion.Kind);

            var semanticSymbol = semanticInfo.Symbol;
            var global = comp.GlobalNamespace;
            var program = global.GetTypeMember("Program");
            var method = program.GetMember<SourceOrdinaryMethodSymbol>("M");
            var i = method.Parameters[0];

            Assert.Equal(i, semanticSymbol.GetSymbol());

            Assert.Equal(CandidateReason.None, semanticInfo.CandidateReason);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);

            Assert.Equal(0, semanticInfo.MethodGroup.Length);

            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [Fact]
        [WorkItem(1009638, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/1009638")]
        public void ExprBodiedFunc02()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class C
{
    public T M<T>(T t) where T : class => /*<bind>*/t/*</bind>*/;
}");
            comp.VerifyDiagnostics();

            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(comp);

            Assert.Equal(TypeKind.TypeParameter, semanticInfo.Type.TypeKind);
            Assert.Equal("T", semanticInfo.Type.Name);
            Assert.Equal("t", semanticInfo.Symbol.Name);
            var m = semanticInfo.Symbol.ContainingSymbol.GetSymbol<SourceOrdinaryMethodSymbol>();
            Assert.Equal(1, m.TypeParameters.Length);
            Assert.Equal(m.TypeParameters[0], semanticInfo.Type.GetSymbol());
            Assert.Equal(m.TypeParameters[0], m.ReturnType);
            Assert.Equal(m, semanticInfo.Type.ContainingSymbol.GetSymbol());
            Assert.Equal(SymbolKind.Parameter, semanticInfo.Symbol.Kind);
        }

        [Fact]
        public void ExprBodiedOperator01()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class Program
{
    public static Program operator ++(Program p) => /*<bind>*/p/*</bind>*/;
}");
            comp.VerifyDiagnostics();

            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(comp);

            Assert.Equal("Program", semanticInfo.Type.Name);
            Assert.Equal("Program", semanticInfo.ConvertedType.Name);
            Assert.Equal(ConversionKind.Identity, semanticInfo.ImplicitConversion.Kind);

            var semanticSymbol = semanticInfo.Symbol;
            var global = comp.GlobalNamespace;
            var program = global.GetTypeMember("Program");
            var method = program.GetMember<SourceUserDefinedOperatorSymbol>("op_Increment");
            var p = method.Parameters[0];

            Assert.Equal(p, semanticSymbol.GetSymbol());

            Assert.Equal(CandidateReason.None, semanticInfo.CandidateReason);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);

            Assert.Equal(0, semanticInfo.MethodGroup.Length);

            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [Fact]
        public void ExprBodiedConversion01()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class C
{
    public static C M(int i) => new C();
    public static explicit operator C(int i) => M(/*<bind>*/i/*</bind>*/);
}");
            comp.VerifyDiagnostics();

            var semanticInfo = GetSemanticInfoForTest<IdentifierNameSyntax>(comp);

            Assert.Equal(SpecialType.System_Int32, semanticInfo.Type.SpecialType);
            Assert.Equal(SpecialType.System_Int32, semanticInfo.ConvertedType.SpecialType);
            Assert.Equal(ConversionKind.Identity, semanticInfo.ImplicitConversion.Kind);

            var semanticSymbol = semanticInfo.Symbol;
            var global = comp.GlobalNamespace;
            var program = global.GetTypeMember("C");
            var method = program.GetMember<SourceUserDefinedConversionSymbol>("op_Explicit");
            var p = method.Parameters[0];

            Assert.Equal(p, semanticSymbol.GetSymbol());

            Assert.Equal(CandidateReason.None, semanticInfo.CandidateReason);
            Assert.Equal(0, semanticInfo.CandidateSymbols.Length);

            Assert.Equal(0, semanticInfo.MethodGroup.Length);

            Assert.False(semanticInfo.IsCompileTimeConstant);
        }

        [WorkItem(1065375, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/1065375"), WorkItem(313, "CodePlex")]
        [Fact]
        public void Bug1065375_1()
        {
            string source = @"
using System;
public static class TestExtension 
{
    static void Main()
    {
        GetAction(1)();
    } 
   
    public static Action GetAction(int x) => () => Console.WriteLine(""GetAction {0}"", x);
}
";

            CompileAndVerify(source, expectedOutput: "GetAction 1");
        }

        [Fact, WorkItem(13691, "https://github.com/dotnet/roslyn/issues/13691")]
        public void RunCtorProp()
        {
            string source = @"
using System;
public class Program 
{
    static void Main()
    {
        var p = new Program();
        p.Prop = 2;
    }
    Program() => Console.Write(1);
    int Prop { set => Console.Write(value); }
    ~Program() => Console.Write(string.Empty);
}
";
            CompileAndVerify(source, expectedOutput: "12");
        }

        [Fact, WorkItem(13691, "https://github.com/dotnet/roslyn/issues/13691")]
        public void RunCtorWithBase01()
        {
            string source = @"
using System;
public class Program 
{
    static void Main()
    {
        var p = new Program();
    }
    Program() : base() => Console.Write(1);
}
";
            CompileAndVerify(source, expectedOutput: "1");
        }

        [Fact, WorkItem(13691, "https://github.com/dotnet/roslyn/issues/13691")]
        public void RunCtorWithBase02()
        {
            string source = @"
using System;
public class Base
{
    public Base(int i) { Console.Write(i); }
}
public class Program : Base
{
    static void Main()
    {
        var p = new Program();
    }
    Program() : base(1) => Console.Write(2);
}
";
            CompileAndVerify(source, expectedOutput: "12");
        }

        [Fact, WorkItem(1069421, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/1069421")]
        public void Bug1069421()
        {
            var comp = CreateCompilationWithMscorlib461(@"
class Program
{
    private int x => () => { 
}
");

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ParenthesizedLambdaExpressionSyntax>().Single();

            var typeInfo1 = model.GetTypeInfo(node);
            var typeInfo2 = model.GetTypeInfo(node);

            Assert.Equal(typeInfo1.Type, typeInfo2.Type);
        }

        [WorkItem(1112875, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/1112875")]
        [Fact]
        public void Bug1112875()
        {
            var comp = CreateCompilation(@"
class Program
{
    private void M() => (new object());
}
");
            comp.VerifyDiagnostics(
                // (4,25): error CS0201: Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement
                //     private void M() => (new object());
                Diagnostic(ErrorCode.ERR_IllegalStatement, "(new object())").WithLocation(4, 25));
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_01()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static void M1() 
    { }
    => P1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static void M1() 
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static void M1() 
    { }
    => P1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_02()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public int operator + (C x, C y)
    { return 1; }
    => P1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public int operator + (C x, C y)
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public int operator + (C x, C y)
    { return 1; }
    => P1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_03()
        {
            var comp = CreateCompilation(@"
public class C
{
    int P1 {get; set;}

    C()
    { P1 = 1; }
    => P1;
}
");

            comp.VerifyDiagnostics(
    // (5,5): error  CS8057: Block bodies and expression bodies cannot both be provided.
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"C()
    { P1 = 1; }
    => P1;").WithLocation(6, 5)
                );
            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());

            Assert.Contains("P1", model.LookupNames(tree.GetRoot().DescendantNodes().OfType<ConstructorDeclarationSyntax>().Single().Body.Position));

            var node2 = tree.GetRoot().DescendantNodes().OfType<ConstructorDeclarationSyntax>().Single()
                .Body.DescendantNodes().OfType<AssignmentExpressionSyntax>()
                .Single().Left;

            Assert.Equal("P1", node2.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node2).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_04()
        {
            var comp = CreateCompilation(@"
public class C
{
    int P1 {get; set;}

    ~C()
    { P1 = 1; }
    => P1;
}
");

            comp.VerifyDiagnostics(
                // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     ~C()
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"~C()
    { P1 = 1; }
    => P1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());

            Assert.Contains("P1", model.LookupNames(tree.GetRoot().DescendantNodes().OfType<DestructorDeclarationSyntax>().Single().Body.Position));

            var node2 = tree.GetRoot().DescendantNodes().OfType<DestructorDeclarationSyntax>().Single()
                .Body.DescendantNodes().OfType<AssignmentExpressionSyntax>()
                .Single().Left;

            Assert.Equal("P1", node2.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node2).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_05()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public int P2
    {
        get
        { return 1; }
        => P1;
    }
}
");

            comp.VerifyDiagnostics(
                // (8,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         get
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"get
        { return 1; }
        => P1;").WithLocation(8, 9)
                );

            var tree = comp.SyntaxTrees[0];
            Assert.Equal(1, tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Count());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_06()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public int P2
    {
    }
    => P1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public int P2
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public int P2
    {
    }
    => P1;").WithLocation(6, 5),
    // (6,23): error CS0548: 'C.P2': property or indexer must have at least one accessor
    //     static public int P2
    Diagnostic(ErrorCode.ERR_PropertyWithNoAccessors, "P2").WithArguments("C.P2").WithLocation(6, 23)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Null(model.GetSymbolInfo(node).Symbol);
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_07()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public explicit operator int (C x)
    { return 1; }
    => P1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public explicit operator int (C x)
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public explicit operator int (C x)
    { return 1; }
    => P1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ArrowExpressionClauseSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_08()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static int M1() 
    { return P1; }
    => 1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static int M1() 
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static int M1() 
    { return P1; }
    => 1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ReturnStatementSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_09()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public int operator + (C x, C y)
    { return P1; }
    => 1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public int operator + (C x, C y)
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public int operator + (C x, C y)
    { return P1; }
    => 1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ReturnStatementSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_10()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public int P2
    {
        get { return P1; }
    }
    => 1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public int P2
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public int P2
    {
        get { return P1; }
    }
    => 1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ReturnStatementSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact, WorkItem(1702, "https://github.com/dotnet/roslyn/issues/1702")]
        public void BlockBodyAndExpressionBody_11()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    static public explicit operator int (C x)
    { return P1; }
    => 1;
}
");

            comp.VerifyDiagnostics(
    // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
    //     static public explicit operator int (C x)
    Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"static public explicit operator int (C x)
    { return P1; }
    => 1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var node = tree.GetRoot().DescendantNodes().OfType<ReturnStatementSyntax>().Single().Expression;

            Assert.Equal("P1", node.ToString());
            Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
        }

        [Fact]
        public void BlockBodyAndExpressionBody_12()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    public C()
    { P1 = 1; }
    => P1 = 1;
}
");

            comp.VerifyDiagnostics(
                // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     public C()
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"public C()
    { P1 = 1; }
    => P1 = 1;").WithLocation(6, 5)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var nodes = tree.GetRoot().DescendantNodes().OfType<AssignmentExpressionSyntax>();
            Assert.Equal(2, nodes.Count());

            foreach (var assign in nodes)
            {
                var node = assign.Left;
                Assert.Equal("P1", node.ToString());
                Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
            }
        }

        [Fact]
        public void BlockBodyAndExpressionBody_13()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    ~C()
    { P1 = 1; }
    => P1 = 1;
}
");

            comp.VerifyDiagnostics(
                // (6,5): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     public C()
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"~C()
    { P1 = 1; }
    => P1 = 1;").WithLocation(6, 5));

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var nodes = tree.GetRoot().DescendantNodes().OfType<AssignmentExpressionSyntax>();
            Assert.Equal(2, nodes.Count());

            foreach (var assign in nodes)
            {
                var node = assign.Left;
                Assert.Equal("P1", node.ToString());
                Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
            }
        }

        [Fact]
        public void BlockBodyAndExpressionBody_14()
        {
            var comp = CreateCompilation(@"
public class C
{
    static int P1 {get; set;}

    int P2
    {
        set
            { P1 = 1; }
            => P1 = 1;
    }
}
");

            comp.VerifyDiagnostics(
                // (8,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         set
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, @"set
            { P1 = 1; }
            => P1 = 1;").WithLocation(8, 9)
                );

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var nodes = tree.GetRoot().DescendantNodes().OfType<AssignmentExpressionSyntax>();
            Assert.Equal(2, nodes.Count());

            foreach (var assign in nodes)
            {
                var node = assign.Left;
                Assert.Equal("P1", node.ToString());
                Assert.Equal("System.Int32 C.P1 { get; set; }", model.GetSymbolInfo(node).Symbol.ToTestDisplayString());
            }
        }

        [Fact]
        public void BlockBodyAndExpressionBody_15()
        {
            var comp = CreateCompilation(@"
public class C
{
    void Goo()
    {
        int Bar() { return 0; } => 0;
    }
}
");

            comp.VerifyDiagnostics(
                // (6,9): error CS8057: Block bodies and expression bodies cannot both be provided.
                //         int Bar() { return 0; } => 0;
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, "int Bar() { return 0; } => 0;").WithLocation(6, 9),
                // (6,13): warning CS8321: The local function 'Bar' is declared but never used
                //         int Bar() { return 0; } => 0;
                Diagnostic(ErrorCode.WRN_UnreferencedLocalFunction, "Bar").WithArguments("Bar").WithLocation(6, 13));
        }

        [Fact]
        public void BlockBodyAndExpressionBody_16()
        {
            var comp = CreateCompilation(@"
public class C
{
    int this[int i] { get { return 0; } } => 0;
}
");

            comp.VerifyDiagnostics(
                // (4,5): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     int this[int i] { get { return 0; } } => 0;
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, "int this[int i] { get { return 0; } } => 0;").WithLocation(4, 5));
        }

        [Fact]
        public void BlockBodyAndExpressionBody_17()
        {
            var comp = CreateCompilation(@"
public class C
{
    int this[int i] { get { return 0; } => 0; }
}
");

            comp.VerifyDiagnostics(
                // (4,23): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     int this[int i] { get { return 0; } => 0; }
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, "get { return 0; } => 0;").WithLocation(4, 23));
        }

        [Fact]
        public void BlockBodyAndExpressionBody_18()
        {
            var comp = CreateCompilation(@"
using System;
public class C
{
    event Action E { add { } => null; remove { } }
}
");

            comp.VerifyDiagnostics(
                // (5,22): error CS8057: Block bodies and expression bodies cannot both be provided.
                //     event Action E { add { } => null; remove { } }
                Diagnostic(ErrorCode.ERR_BlockBodyAndExpressionBody, "add { } => null;").WithLocation(5, 22));
        }

        [Fact, WorkItem(971, "https://github.com/dotnet/roslyn/issues/971")]
        public void LookupSymbols()
        {
            var comp = CreateCompilation(@"
using System;
public class C
{
    Func<int, int> U() => delegate (int y0) { return 0; }
    int V(int y1) => 1;
}

Func<int, int> W() => delegate (int y2) { return 2; }

public class D
{
    public D(int y3) => M(3);
    public ~D() => M(y4 => 4);
    public Func<int, int> Prop { get => y5 => 5; }
    public static void M(int i) {}
    public static void M(Func<int, int> d) {}
}
");

            var tree = comp.SyntaxTrees[0];
            var model = comp.GetSemanticModel(tree);

            var nodes = tree.GetRoot().DescendantNodes().OfType<LiteralExpressionSyntax>().ToArray();
            Assert.Equal(6, nodes.Length);

            for (int i = 0; i < nodes.Length; i++)
            {
                Assert.Equal($"{i}", nodes[i].ToString());
                Assert.Equal($"System.Int32 y{i}", model.LookupSymbols(nodes[i].SpanStart, name: $"y{i}").Single().ToTestDisplayString());
            }
        }

        [Fact, WorkItem(13578, "https://github.com/dotnet/roslyn/issues/13578")]
        public void ExpressionBodiesNotSupported()
        {
            var source = @"
using System;
public class C
{
    C() => Console.WriteLine(1);
    ~C() => Console.WriteLine(2);
    int P { set => Console.WriteLine(value); }
}
";
            CreateCompilation(source, parseOptions: TestOptions.Regular).VerifyDiagnostics();
            CreateCompilation(source, parseOptions: TestOptions.Regular6).VerifyDiagnostics(
                // (5,9): error CS8059: Feature 'expression body constructor and destructor' is not available in C# 6. Please use language version 7.0 or greater.
                //     C() => Console.WriteLine(1);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "=>").WithArguments("expression body constructor and destructor", "7.0").WithLocation(5, 9),
                // (6,10): error CS8059: Feature 'expression body constructor and destructor' is not available in C# 6. Please use language version 7.0 or greater.
                //     ~C() => Console.WriteLine(2);
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "=>").WithArguments("expression body constructor and destructor", "7.0").WithLocation(6, 10),
                // (7,17): error CS8059: Feature 'expression body property accessor' is not available in C# 6. Please use language version 7.0 or greater.
                //     int P { set => Console.WriteLine(value); }
                Diagnostic(ErrorCode.ERR_FeatureNotAvailableInVersion6, "=>").WithArguments("expression body property accessor", "7.0").WithLocation(7, 17));
        }
    }
}
