// 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 System.Threading.Tasks;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis
{
    internal abstract class AsyncSymbolVisitor<TResult> : SymbolVisitor<ValueTask<TResult>>
    {
        protected abstract TResult DefaultResult { get; }
 
        public override ValueTask<TResult> Visit(ISymbol? symbol)
            => symbol?.Accept(this) ?? ValueTaskFactory.FromResult(DefaultResult);
 
        public override ValueTask<TResult> DefaultVisit(ISymbol symbol)
            => ValueTaskFactory.FromResult(DefaultResult);
    }
}