LocalRewriter_DelegateCreationExpression.cs

// 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.Diagnostics;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.CSharp
{
    internal partial class LocalRewriter
    {
        public override BoundNode VisitDelegateCreationExpression(BoundDelegateCreationExpression node)
        {
            Debug.Assert(!node.Type.IsAnonymousType); // Missing EnsureParamCollectionAttributeExists call?

            if (node.Argument.HasDynamicType())
            {
                var loweredArgument = VisitExpression(node.Argument);

                // Creates a delegate whose instance is the delegate that is returned by the call-site and the method is Invoke.
                var loweredReceiver = _dynamicFactory.MakeDynamicConversion(loweredArgument, isExplicit: false, isArrayIndex: false, isChecked: false, resultType: node.Type).ToExpression();

                return new BoundDelegateCreationExpression(node.Syntax, loweredReceiver, methodOpt: null, isExtensionMethod: false, node.WasTargetTyped, type: node.Type);
            }

            if (node.Argument.Kind == BoundKind.MethodGroup)
            {
                var mg = (BoundMethodGroup)node.Argument;
                var method = node.MethodOpt;
                Debug.Assert(method is { });
                var oldSyntax = _factory.Syntax;
                _factory.Syntax = (mg.ReceiverOpt ?? mg).Syntax;
                var receiver = (!method.RequiresInstanceReceiver && !node.IsExtensionMethod && !method.IsAbstract && !method.IsVirtual) ? _factory.Type(method.ContainingType) : VisitExpression(mg.ReceiverOpt)!;
                _factory.Syntax = oldSyntax;
                return node.Update(receiver, method, node.IsExtensionMethod, node.WasTargetTyped, node.Type);
            }

            return base.VisitDelegateCreationExpression(node)!;
        }
    }
}