// 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.
 
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.LanguageService;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.UseObjectInitializer;
 
namespace Microsoft.CodeAnalysis.CSharp.UseObjectInitializer
{
    [DiagnosticAnalyzer(LanguageNames.CSharp)]
    internal class CSharpUseObjectInitializerDiagnosticAnalyzer :
        AbstractUseObjectInitializerDiagnosticAnalyzer<
            SyntaxKind,
            ExpressionSyntax,
            StatementSyntax,
            BaseObjectCreationExpressionSyntax,
            MemberAccessExpressionSyntax,
            ExpressionStatementSyntax,
            VariableDeclaratorSyntax>
    {
        protected override bool FadeOutOperatorToken => true;
 
        protected override bool AreObjectInitializersSupported(Compilation compilation)
        {
            // object initializers are only available in C# 3.0 and above.  Don't offer this refactoring
            // in projects targeting a lesser version.
            return compilation.LanguageVersion() >= LanguageVersion.CSharp3;
        }
 
        protected override ISyntaxFacts GetSyntaxFacts() => CSharpSyntaxFacts.Instance;
 
        protected override bool IsValidContainingStatement(StatementSyntax node)
        {
            // We don't want to offer this for using declarations because the way they are lifted means all
            // initialization is done before entering try block. For example
            // 
            // using var c = new Disposable() { Goo = 2 };
            //
            // is lowered to:
            //
            // var __c = new Disposable();
            // __c.Goo = 2;
            // var c = __c;
            // try
            // {
            // }
            // finally
            // {
            //     if (c != null)
            //     {
            //         ((IDisposable)c).Dispose();
            //     }
            // }
            //
            // As can be seen, if initializing throws any kind of exception, the newly created instance will not
            // be disposed properly.
            return node is not LocalDeclarationStatementSyntax localDecl ||
                localDecl.UsingKeyword == default;
        }
    }
}