CSharpChangeSignatureService.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;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Composition;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.ChangeSignature;
using Microsoft.CodeAnalysis.CSharp.CodeGeneration;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.LanguageService;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Formatting.Rules;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;
using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 
namespace Microsoft.CodeAnalysis.CSharp.ChangeSignature
{
    [ExportLanguageService(typeof(AbstractChangeSignatureService), LanguageNames.CSharp), Shared]
    internal sealed class CSharpChangeSignatureService : AbstractChangeSignatureService
    {
        protected override SyntaxGenerator Generator => CSharpSyntaxGenerator.Instance;
        protected override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
 
        private static readonly ImmutableArray<SyntaxKind> _declarationKinds = ImmutableArray.Create(
            SyntaxKind.MethodDeclaration,
            SyntaxKind.ConstructorDeclaration,
            SyntaxKind.IndexerDeclaration,
            SyntaxKind.DelegateDeclaration,
            SyntaxKind.SimpleLambdaExpression,
            SyntaxKind.ParenthesizedLambdaExpression,
            SyntaxKind.LocalFunctionStatement,
            SyntaxKind.RecordStructDeclaration,
            SyntaxKind.RecordDeclaration,
            SyntaxKind.StructDeclaration,
            SyntaxKind.ClassDeclaration);
 
        private static readonly ImmutableArray<SyntaxKind> _declarationAndInvocableKinds =
            _declarationKinds.Concat(ImmutableArray.Create(
                SyntaxKind.InvocationExpression,
                SyntaxKind.ElementAccessExpression,
                SyntaxKind.ThisConstructorInitializer,
                SyntaxKind.BaseConstructorInitializer,
                SyntaxKind.ObjectCreationExpression,
                SyntaxKind.ImplicitObjectCreationExpression,
                SyntaxKind.Attribute,
                SyntaxKind.NameMemberCref));
 
        private static readonly ImmutableArray<SyntaxKind> _updatableAncestorKinds = ImmutableArray.Create(
            SyntaxKind.ConstructorDeclaration,
            SyntaxKind.IndexerDeclaration,
            SyntaxKind.InvocationExpression,
            SyntaxKind.ElementAccessExpression,
            SyntaxKind.ThisConstructorInitializer,
            SyntaxKind.BaseConstructorInitializer,
            SyntaxKind.ObjectCreationExpression,
            SyntaxKind.Attribute,
            SyntaxKind.DelegateDeclaration,
            SyntaxKind.SimpleLambdaExpression,
            SyntaxKind.ParenthesizedLambdaExpression,
            SyntaxKind.NameMemberCref);
 
        private static readonly ImmutableArray<SyntaxKind> _updatableNodeKinds = ImmutableArray.Create(
            SyntaxKind.MethodDeclaration,
            SyntaxKind.LocalFunctionStatement,
            SyntaxKind.ConstructorDeclaration,
            SyntaxKind.IndexerDeclaration,
            SyntaxKind.InvocationExpression,
            SyntaxKind.ElementAccessExpression,
            SyntaxKind.ThisConstructorInitializer,
            SyntaxKind.BaseConstructorInitializer,
            SyntaxKind.ObjectCreationExpression,
            SyntaxKind.ImplicitObjectCreationExpression,
            SyntaxKind.Attribute,
            SyntaxKind.DelegateDeclaration,
            SyntaxKind.NameMemberCref,
            SyntaxKind.AnonymousMethodExpression,
            SyntaxKind.ParenthesizedLambdaExpression,
            SyntaxKind.SimpleLambdaExpression,
            SyntaxKind.RecordStructDeclaration,
            SyntaxKind.RecordDeclaration,
            SyntaxKind.StructDeclaration,
            SyntaxKind.ClassDeclaration);
 
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public CSharpChangeSignatureService()
        {
        }
 
        public override async Task<(ISymbol? symbol, int selectedIndex)> GetInvocationSymbolAsync(
            Document document, int position, bool restrictToDeclarations, CancellationToken cancellationToken)
        {
            var tree = await document.GetRequiredSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
 
            var token = root.FindToken(position != tree.Length ? position : Math.Max(0, position - 1));
 
            // Allow the user to invoke Change-Sig if they've written:   Goo(a, b, c);$$ 
            if (token.Kind() == SyntaxKind.SemicolonToken && token.Parent is StatementSyntax)
            {
                token = token.GetPreviousToken();
                position = token.Span.End;
            }
 
            if (token.Parent == null)
            {
                return default;
            }
 
            var matchingNode = GetMatchingNode(token.Parent, restrictToDeclarations);
            if (matchingNode == null)
            {
                return default;
            }
 
            // Don't show change-signature in the random whitespace/trivia for code.
            if (!matchingNode.Span.IntersectsWith(position))
            {
                return default;
            }
 
            // If we're actually on the declaration of some symbol, ensure that we're
            // in a good location for that symbol (i.e. not in the attributes/constraints).
            if (!InSymbolHeader(matchingNode, position))
            {
                return default;
            }
 
            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
            var symbol = semanticModel.GetDeclaredSymbol(matchingNode, cancellationToken);
            if (symbol != null)
            {
                var selectedIndex = TryGetSelectedIndexFromDeclaration(position, matchingNode);
                return (symbol, selectedIndex);
            }
 
            if (matchingNode is ObjectCreationExpressionSyntax objectCreation &&
                token.Parent.AncestorsAndSelf().Any(a => a == objectCreation.Type))
            {
                var typeSymbol = semanticModel.GetSymbolInfo(objectCreation.Type, cancellationToken).Symbol;
                if (typeSymbol != null && typeSymbol.IsKind(SymbolKind.NamedType) && ((ITypeSymbol)typeSymbol).TypeKind == TypeKind.Delegate)
                {
                    return (typeSymbol, 0);
                }
            }
 
            var symbolInfo = semanticModel.GetSymbolInfo(matchingNode, cancellationToken);
            var parameterIndex = 0;
 
            // If we're being called on an invocation and not a definition we need to find the selected argument index based on the original definition.
            var argumentList = matchingNode is ObjectCreationExpressionSyntax objCreation ? objCreation.ArgumentList
                : matchingNode.GetAncestorOrThis<InvocationExpressionSyntax>()?.ArgumentList;
            var argument = argumentList?.Arguments.FirstOrDefault(a => a.Span.Contains(position));
            if (argument != null)
            {
                parameterIndex = GetParameterIndexFromInvocationArgument(argument, document, semanticModel, cancellationToken);
            }
 
            return (symbolInfo.Symbol ?? symbolInfo.CandidateSymbols.FirstOrDefault(), parameterIndex);
        }
 
        private static int TryGetSelectedIndexFromDeclaration(int position, SyntaxNode matchingNode)
        {
            var parameters = matchingNode.ChildNodes().OfType<BaseParameterListSyntax>().SingleOrDefault();
            return parameters != null ? GetParameterIndex(parameters.Parameters, position) : 0;
        }
 
        private static SyntaxNode? GetMatchingNode(SyntaxNode node, bool restrictToDeclarations)
        {
            var matchKinds = restrictToDeclarations
                ? _declarationKinds
                : _declarationAndInvocableKinds;
 
            for (var current = node; current != null; current = current.Parent)
            {
                if (restrictToDeclarations &&
                    current.Kind() == SyntaxKind.Block || current.Kind() == SyntaxKind.ArrowExpressionClause)
                {
                    return null;
                }
 
                if (matchKinds.Contains(current.Kind()))
                {
                    return current;
                }
            }
 
            return null;
        }
 
        private static bool InSymbolHeader(SyntaxNode matchingNode, int position)
        {
            // Caret has to be after the attributes if the symbol has any.
            var lastAttributes = matchingNode.ChildNodes().LastOrDefault(n => n is AttributeListSyntax);
            var start = lastAttributes?.GetLastToken().GetNextToken().SpanStart ??
                        matchingNode.SpanStart;
 
            if (position < start)
            {
                return false;
            }
 
            // If the symbol has a parameter list, then the caret shouldn't be past the end of it.
            var parameterList = matchingNode.ChildNodes().LastOrDefault(n => n is ParameterListSyntax);
            if (parameterList != null)
            {
                return position <= parameterList.FullSpan.End;
            }
 
            // Case we haven't handled yet.  Just assume we're in the header.
            return true;
        }
 
        public override SyntaxNode? FindNodeToUpdate(Document document, SyntaxNode node)
        {
            if (_updatableNodeKinds.Contains(node.Kind()))
            {
                return node;
            }
 
            // TODO: file bug about this: var invocation = csnode.Ancestors().FirstOrDefault(a => a.Kind == SyntaxKind.InvocationExpression);
            var matchingNode = node.AncestorsAndSelf().FirstOrDefault(n => _updatableAncestorKinds.Contains(n.Kind()));
            if (matchingNode == null)
            {
                return null;
            }
 
            var nodeContainingOriginal = GetNodeContainingTargetNode(matchingNode);
            if (nodeContainingOriginal == null)
            {
                return null;
            }
 
            return node.AncestorsAndSelf().Any(n => n == nodeContainingOriginal) ? matchingNode : null;
        }
 
        private static SyntaxNode? GetNodeContainingTargetNode(SyntaxNode matchingNode)
        {
            switch (matchingNode.Kind())
            {
                case SyntaxKind.InvocationExpression:
                    return ((InvocationExpressionSyntax)matchingNode).Expression;
 
                case SyntaxKind.ElementAccessExpression:
                    return ((ElementAccessExpressionSyntax)matchingNode).ArgumentList;
 
                case SyntaxKind.ObjectCreationExpression:
                    return ((ObjectCreationExpressionSyntax)matchingNode).Type;
 
                case SyntaxKind.ConstructorDeclaration:
                case SyntaxKind.IndexerDeclaration:
                case SyntaxKind.ThisConstructorInitializer:
                case SyntaxKind.BaseConstructorInitializer:
                case SyntaxKind.Attribute:
                case SyntaxKind.DelegateDeclaration:
                case SyntaxKind.NameMemberCref:
                    return matchingNode;
 
                default:
                    return null;
            }
        }
 
        public override async Task<SyntaxNode> ChangeSignatureAsync(
            Document document,
            ISymbol declarationSymbol,
            SyntaxNode potentiallyUpdatedNode,
            SyntaxNode originalNode,
            SignatureChange signaturePermutation,
            LineFormattingOptionsProvider fallbackOptions,
            CancellationToken cancellationToken)
        {
            var updatedNode = potentiallyUpdatedNode as CSharpSyntaxNode;
 
            // Update <param> tags.
            if (updatedNode.IsKind(SyntaxKind.MethodDeclaration) ||
                updatedNode.IsKind(SyntaxKind.ConstructorDeclaration) ||
                updatedNode.IsKind(SyntaxKind.IndexerDeclaration) ||
                updatedNode.IsKind(SyntaxKind.DelegateDeclaration) ||
                updatedNode.IsKind(SyntaxKind.RecordStructDeclaration) ||
                updatedNode.IsKind(SyntaxKind.RecordDeclaration) ||
                updatedNode.IsKind(SyntaxKind.StructDeclaration) ||
                updatedNode.IsKind(SyntaxKind.ClassDeclaration))
            {
                var updatedLeadingTrivia = await UpdateParamTagsInLeadingTriviaAsync(document, updatedNode, declarationSymbol, signaturePermutation, fallbackOptions, cancellationToken).ConfigureAwait(false);
                if (updatedLeadingTrivia != default && !updatedLeadingTrivia.IsEmpty)
                {
                    updatedNode = updatedNode.WithLeadingTrivia(updatedLeadingTrivia);
                }
            }
 
            // Update declarations parameter lists
            if (updatedNode is MethodDeclarationSyntax method)
            {
                var updatedParameters = UpdateDeclaration(method.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return method.WithParameterList(method.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is TypeDeclarationSyntax { ParameterList: not null } typeWithParameters)
            {
                var updatedParameters = UpdateDeclaration(typeWithParameters.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return typeWithParameters.WithParameterList(typeWithParameters.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is LocalFunctionStatementSyntax localFunction)
            {
                var updatedParameters = UpdateDeclaration(localFunction.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return localFunction.WithParameterList(localFunction.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is ConstructorDeclarationSyntax constructor)
            {
                var updatedParameters = UpdateDeclaration(constructor.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return constructor.WithParameterList(constructor.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is IndexerDeclarationSyntax indexer)
            {
                var updatedParameters = UpdateDeclaration(indexer.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return indexer.WithParameterList(indexer.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is DelegateDeclarationSyntax delegateDeclaration)
            {
                var updatedParameters = UpdateDeclaration(delegateDeclaration.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return delegateDeclaration.WithParameterList(delegateDeclaration.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is AnonymousMethodExpressionSyntax anonymousMethod)
            {
                // Delegates may omit parameters in C#
                if (anonymousMethod.ParameterList == null)
                {
                    return anonymousMethod;
                }
 
                var updatedParameters = UpdateDeclaration(anonymousMethod.ParameterList.Parameters, signaturePermutation, CreateNewParameterSyntax);
                return anonymousMethod.WithParameterList(anonymousMethod.ParameterList.WithParameters(updatedParameters).WithAdditionalAnnotations(changeSignatureFormattingAnnotation));
            }
 
            if (updatedNode is SimpleLambdaExpressionSyntax lambda)
            {
                if (signaturePermutation.UpdatedConfiguration.ToListOfParameters().Any())
                {
                    var updatedParameters = UpdateDeclaration(SeparatedList(new[] { lambda.Parameter }), signaturePermutation, CreateNewParameterSyntax);
                    return ParenthesizedLambdaExpression(
                        lambda.AsyncKeyword,
                        ParameterList(updatedParameters),
                        lambda.ArrowToken,
                        lambda.Body);
                }
                else
                {
                    // No parameters. Change to a parenthesized lambda expression
                    var emptyParameterList = ParameterList()
                        .WithLeadingTrivia(lambda.Parameter.GetLeadingTrivia())
                        .WithTrailingTrivia(lambda.Parameter.GetTrailingTrivia());
 
                    return ParenthesizedLambdaExpression(lambda.AsyncKeyword, emptyParameterList, lambda.ArrowToken, lambda.Body);
                }
            }
 
            if (updatedNode is ParenthesizedLambdaExpressionSyntax parenLambda)
            {
                var doNotSkipParameterType = parenLambda.ParameterList.Parameters.FirstOrDefault()?.Type != null;
 
                var updatedParameters = UpdateDeclaration(
                    parenLambda.ParameterList.Parameters,
                    signaturePermutation,
                    p => CreateNewParameterSyntax(p, !doNotSkipParameterType));
                return parenLambda.WithParameterList(parenLambda.ParameterList.WithParameters(updatedParameters));
            }
 
            // Handle references in crefs
            if (updatedNode is NameMemberCrefSyntax nameMemberCref)
            {
                if (nameMemberCref.Parameters == null ||
                    !nameMemberCref.Parameters.Parameters.Any())
                {
                    return nameMemberCref;
                }
 
                var newParameters = UpdateDeclaration(nameMemberCref.Parameters.Parameters, signaturePermutation, CreateNewCrefParameterSyntax);
 
                var newCrefParameterList = nameMemberCref.Parameters.WithParameters(newParameters);
                return nameMemberCref.WithParameters(newCrefParameterList);
            }
 
            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
            // Update reference site argument lists
            if (updatedNode is InvocationExpressionSyntax invocation)
            {
                var symbolInfo = semanticModel.GetSymbolInfo((InvocationExpressionSyntax)originalNode, cancellationToken);
 
                return invocation.WithArgumentList(
                    await UpdateArgumentListAsync(
                        declarationSymbol,
                        signaturePermutation,
                        invocation.ArgumentList,
                        symbolInfo.Symbol is IMethodSymbol { MethodKind: MethodKind.ReducedExtension },
                        IsParamsArrayExpanded(semanticModel, invocation, symbolInfo, cancellationToken),
                        document,
                        originalNode.SpanStart,
                        cancellationToken).ConfigureAwait(false));
            }
 
            // Handles both ObjectCreationExpressionSyntax and ImplicitObjectCreationExpressionSyntax
            if (updatedNode is BaseObjectCreationExpressionSyntax objCreation)
            {
                if (objCreation.ArgumentList == null)
                {
                    return updatedNode;
                }
 
                var symbolInfo = semanticModel.GetSymbolInfo((BaseObjectCreationExpressionSyntax)originalNode, cancellationToken);
 
                return objCreation.WithArgumentList(
                    await UpdateArgumentListAsync(
                        declarationSymbol,
                        signaturePermutation,
                        objCreation.ArgumentList,
                        isReducedExtensionMethod: false,
                        IsParamsArrayExpanded(semanticModel, objCreation, symbolInfo, cancellationToken),
                        document,
                        originalNode.SpanStart,
                        cancellationToken).ConfigureAwait(false));
            }
 
            if (updatedNode is ConstructorInitializerSyntax constructorInit)
            {
                var symbolInfo = semanticModel.GetSymbolInfo((ConstructorInitializerSyntax)originalNode, cancellationToken);
 
                return constructorInit.WithArgumentList(
                    await UpdateArgumentListAsync(
                        declarationSymbol,
                        signaturePermutation,
                        constructorInit.ArgumentList,
                        isReducedExtensionMethod: false,
                        IsParamsArrayExpanded(semanticModel, constructorInit, symbolInfo, cancellationToken),
                        document,
                        originalNode.SpanStart,
                        cancellationToken).ConfigureAwait(false));
            }
 
            if (updatedNode is ElementAccessExpressionSyntax elementAccess)
            {
                var symbolInfo = semanticModel.GetSymbolInfo((ElementAccessExpressionSyntax)originalNode, cancellationToken);
 
                return elementAccess.WithArgumentList(
                    await UpdateArgumentListAsync(
                        declarationSymbol,
                        signaturePermutation,
                        elementAccess.ArgumentList,
                        isReducedExtensionMethod: false,
                        IsParamsArrayExpanded(semanticModel, elementAccess, symbolInfo, cancellationToken),
                        document,
                        originalNode.SpanStart,
                        cancellationToken).ConfigureAwait(false));
            }
 
            if (updatedNode is AttributeSyntax attribute)
            {
                var symbolInfo = semanticModel.GetSymbolInfo((AttributeSyntax)originalNode, cancellationToken);
 
                if (attribute.ArgumentList == null)
                {
                    return updatedNode;
                }
 
                return attribute.WithArgumentList(
                    await UpdateAttributeArgumentListAsync(
                        declarationSymbol,
                        signaturePermutation,
                        attribute.ArgumentList,
                        isReducedExtensionMethod: false,
                        IsParamsArrayExpanded(semanticModel, attribute, symbolInfo, cancellationToken),
                        document,
                        originalNode.SpanStart,
                        cancellationToken).ConfigureAwait(false));
            }
 
            Debug.Assert(false, "Unknown reference location");
            return null;
        }
 
        private async Task<T> UpdateArgumentListAsync<T>(
            ISymbol declarationSymbol,
            SignatureChange signaturePermutation,
            T argumentList,
            bool isReducedExtensionMethod,
            bool isParamsArrayExpanded,
            Document document,
            int position,
            CancellationToken cancellationToken) where T : BaseArgumentListSyntax
        {
            // Reorders and removes arguments
            // e.g. P(a, b, c) ==> P(c, a)
            var newArguments = PermuteArgumentList(
                declarationSymbol,
                argumentList.Arguments,
                signaturePermutation.WithoutAddedParameters(),
                isReducedExtensionMethod);
 
            // Adds new arguments into the updated list
            // e.g. P(c, a) ==> P(x, c, a, y)
            newArguments = await AddNewArgumentsToListAsync(
                declarationSymbol,
                newArguments,
                argumentList.Arguments,
                signaturePermutation,
                isReducedExtensionMethod,
                isParamsArrayExpanded,
                generateAttributeArguments: false,
                document,
                position,
                cancellationToken).ConfigureAwait(false);
 
            return (T)argumentList
                .WithArguments(newArguments)
                .WithAdditionalAnnotations(changeSignatureFormattingAnnotation);
        }
 
        private async Task<AttributeArgumentListSyntax> UpdateAttributeArgumentListAsync(
            ISymbol declarationSymbol,
            SignatureChange signaturePermutation,
            AttributeArgumentListSyntax argumentList,
            bool isReducedExtensionMethod,
            bool isParamsArrayExpanded,
            Document document,
            int position,
            CancellationToken cancellationToken)
        {
            var newArguments = PermuteAttributeArgumentList(
                declarationSymbol,
                argumentList.Arguments,
                signaturePermutation.WithoutAddedParameters());
 
            newArguments = await AddNewArgumentsToListAsync(
                declarationSymbol,
                newArguments,
                argumentList.Arguments,
                signaturePermutation,
                isReducedExtensionMethod,
                isParamsArrayExpanded,
                generateAttributeArguments: true,
                document,
                position,
                cancellationToken).ConfigureAwait(false);
 
            return argumentList
                .WithArguments(newArguments)
                .WithAdditionalAnnotations(changeSignatureFormattingAnnotation);
        }
 
        private static bool IsParamsArrayExpanded(SemanticModel semanticModel, SyntaxNode node, SymbolInfo symbolInfo, CancellationToken cancellationToken)
        {
            if (symbolInfo.Symbol == null)
            {
                return false;
            }
 
            int argumentCount;
            bool lastArgumentIsNamed;
            ExpressionSyntax lastArgumentExpression;
 
            if (node is AttributeSyntax attribute)
            {
                if (attribute.ArgumentList == null)
                {
                    return false;
                }
 
                argumentCount = attribute.ArgumentList.Arguments.Count;
                lastArgumentIsNamed = attribute.ArgumentList.Arguments.LastOrDefault()?.NameColon != null ||
                    attribute.ArgumentList.Arguments.LastOrDefault()?.NameEquals != null;
 
                var lastArgument = attribute.ArgumentList.Arguments.LastOrDefault();
                if (lastArgument == null)
                {
                    return false;
                }
 
                lastArgumentExpression = lastArgument.Expression;
            }
            else
            {
                BaseArgumentListSyntax? argumentList = node switch
                {
                    InvocationExpressionSyntax invocation => invocation.ArgumentList,
                    BaseObjectCreationExpressionSyntax objectCreation => objectCreation.ArgumentList,
                    ConstructorInitializerSyntax constructorInitializer => constructorInitializer.ArgumentList,
                    ElementAccessExpressionSyntax elementAccess => elementAccess.ArgumentList,
                    _ => throw ExceptionUtilities.UnexpectedValue(node.Kind())
                };
 
                if (argumentList == null)
                {
                    return false;
                }
 
                argumentCount = argumentList.Arguments.Count;
                lastArgumentIsNamed = argumentList.Arguments.LastOrDefault()?.NameColon != null;
 
                var lastArgument = argumentList.Arguments.LastOrDefault();
                if (lastArgument == null)
                {
                    return false;
                }
 
                lastArgumentExpression = lastArgument.Expression;
            }
 
            return IsParamsArrayExpandedHelper(symbolInfo.Symbol, argumentCount, lastArgumentIsNamed, semanticModel, lastArgumentExpression, cancellationToken);
        }
 
        private static ParameterSyntax CreateNewParameterSyntax(AddedParameter addedParameter)
            => CreateNewParameterSyntax(addedParameter, skipParameterType: false);
 
        private static ParameterSyntax CreateNewParameterSyntax(AddedParameter addedParameter, bool skipParameterType)
        {
            var equalsValueClause = addedParameter.HasDefaultValue
                ? EqualsValueClause(ParseExpression(addedParameter.DefaultValue))
                : null;
 
            return Parameter(
                attributeLists: default,
                modifiers: default,
                type: skipParameterType
                    ? null
                    : addedParameter.Type.GenerateTypeSyntax(),
                Identifier(addedParameter.Name),
                @default: equalsValueClause);
        }
 
        private static CrefParameterSyntax CreateNewCrefParameterSyntax(AddedParameter addedParameter)
            => CrefParameter(type: addedParameter.Type.GenerateTypeSyntax())
                .WithLeadingTrivia(ElasticSpace);
 
        private SeparatedSyntaxList<T> UpdateDeclaration<T>(
            SeparatedSyntaxList<T> list,
            SignatureChange updatedSignature,
            Func<AddedParameter, T> createNewParameterMethod) where T : SyntaxNode
        {
            var (parameters, separators) = base.UpdateDeclarationBase<T>(list, updatedSignature, createNewParameterMethod);
            return SeparatedList(parameters, separators);
        }
 
        protected override T TransferLeadingWhitespaceTrivia<T>(T newArgument, SyntaxNode oldArgument)
        {
            var oldTrivia = oldArgument.GetLeadingTrivia();
            var oldOnlyHasWhitespaceTrivia = oldTrivia.All(t => t.IsKind(SyntaxKind.WhitespaceTrivia));
 
            var newTrivia = newArgument.GetLeadingTrivia();
            var newOnlyHasWhitespaceTrivia = newTrivia.All(t => t.IsKind(SyntaxKind.WhitespaceTrivia));
 
            if (oldOnlyHasWhitespaceTrivia && newOnlyHasWhitespaceTrivia)
            {
                newArgument = newArgument.WithLeadingTrivia(oldTrivia);
            }
 
            return newArgument;
        }
 
        private async Task<SeparatedSyntaxList<SyntaxNode>> AddNewArgumentsToListAsync(
            ISymbol declarationSymbol,
            SeparatedSyntaxList<SyntaxNode> newArguments,
            SeparatedSyntaxList<SyntaxNode> originalArguments,
            SignatureChange signaturePermutation,
            bool isReducedExtensionMethod,
            bool isParamsArrayExpanded,
            bool generateAttributeArguments,
            Document document,
            int position,
            CancellationToken cancellationToken)
        {
            var newArgumentList = await AddNewArgumentsToListAsync(
                declarationSymbol, newArguments,
                signaturePermutation, isReducedExtensionMethod,
                isParamsArrayExpanded, generateAttributeArguments,
                document, position, cancellationToken).ConfigureAwait(false);
 
            return SeparatedList(
                TransferLeadingWhitespaceTrivia(newArgumentList, originalArguments),
                newArgumentList.GetSeparators());
        }
 
        private SeparatedSyntaxList<AttributeArgumentSyntax> PermuteAttributeArgumentList(
            ISymbol declarationSymbol,
            SeparatedSyntaxList<AttributeArgumentSyntax> arguments,
            SignatureChange updatedSignature)
        {
            var newArguments = PermuteArguments(declarationSymbol, arguments.Select(a => UnifiedArgumentSyntax.Create(a)).ToImmutableArray(),
                updatedSignature);
            var numSeparatorsToSkip = arguments.Count - newArguments.Length;
 
            // copy whitespace trivia from original position
            var newArgumentsWithTrivia = TransferLeadingWhitespaceTrivia(
                newArguments.Select(a => (AttributeArgumentSyntax)(UnifiedArgumentSyntax)a), arguments);
 
            return SeparatedList(newArgumentsWithTrivia, GetSeparators(arguments, numSeparatorsToSkip));
        }
 
        private SeparatedSyntaxList<ArgumentSyntax> PermuteArgumentList(
            ISymbol declarationSymbol,
            SeparatedSyntaxList<ArgumentSyntax> arguments,
            SignatureChange updatedSignature,
            bool isReducedExtensionMethod = false)
        {
            var newArguments = PermuteArguments(
                declarationSymbol,
                arguments.Select(a => UnifiedArgumentSyntax.Create(a)).ToImmutableArray(),
                updatedSignature,
                isReducedExtensionMethod);
 
            // copy whitespace trivia from original position
            var newArgumentsWithTrivia = TransferLeadingWhitespaceTrivia(
                newArguments.Select(a => (ArgumentSyntax)(UnifiedArgumentSyntax)a), arguments);
 
            var numSeparatorsToSkip = arguments.Count - newArguments.Length;
            return SeparatedList(newArgumentsWithTrivia, GetSeparators(arguments, numSeparatorsToSkip));
        }
 
        private ImmutableArray<T> TransferLeadingWhitespaceTrivia<T, U>(IEnumerable<T> newArguments, SeparatedSyntaxList<U> oldArguments)
            where T : SyntaxNode
            where U : SyntaxNode
        {
            var result = ImmutableArray.CreateBuilder<T>();
            var index = 0;
            foreach (var newArgument in newArguments)
            {
                result.Add(index < oldArguments.Count
                    ? TransferLeadingWhitespaceTrivia(newArgument, oldArguments[index])
                    : newArgument);
 
                index++;
            }
 
            return result.ToImmutable();
        }
 
        private async ValueTask<ImmutableArray<SyntaxTrivia>> UpdateParamTagsInLeadingTriviaAsync(
            Document document, CSharpSyntaxNode node, ISymbol declarationSymbol, SignatureChange updatedSignature, LineFormattingOptionsProvider fallbackOptions, CancellationToken cancellationToken)
        {
            if (!node.HasLeadingTrivia)
            {
                return ImmutableArray<SyntaxTrivia>.Empty;
            }
 
            var paramNodes = node
                .DescendantNodes(descendIntoTrivia: true)
                .OfType<XmlElementSyntax>()
                .Where(e => e.StartTag.Name.ToString() == DocumentationCommentXmlNames.ParameterElementName);
 
            var permutedParamNodes = VerifyAndPermuteParamNodes(paramNodes, declarationSymbol, updatedSignature);
            if (permutedParamNodes.IsEmpty)
            {
                return ImmutableArray<SyntaxTrivia>.Empty;
            }
 
            var options = await document.GetLineFormattingOptionsAsync(fallbackOptions, cancellationToken).ConfigureAwait(false);
            return GetPermutedDocCommentTrivia(node, permutedParamNodes, document.Project.Services, options);
        }
 
        private ImmutableArray<SyntaxNode> VerifyAndPermuteParamNodes(IEnumerable<XmlElementSyntax> paramNodes, ISymbol declarationSymbol, SignatureChange updatedSignature)
        {
            // Only reorder if count and order match originally.
            var originalParameters = updatedSignature.OriginalConfiguration.ToListOfParameters();
            var reorderedParameters = updatedSignature.UpdatedConfiguration.ToListOfParameters();
 
            var declaredParameters = GetParameters(declarationSymbol);
 
            if (paramNodes.Count() != declaredParameters.Length)
            {
                return ImmutableArray<SyntaxNode>.Empty;
            }
 
            // No parameters originally, so no param nodes to permute.
            if (declaredParameters.Length == 0)
            {
                return ImmutableArray<SyntaxNode>.Empty;
            }
 
            var dictionary = new Dictionary<string, XmlElementSyntax>();
            var i = 0;
            foreach (var paramNode in paramNodes)
            {
                var nameAttribute = paramNode.StartTag.Attributes.FirstOrDefault(a => a.Name.ToString().Equals("name", StringComparison.OrdinalIgnoreCase));
                if (nameAttribute == null)
                {
                    return ImmutableArray<SyntaxNode>.Empty;
                }
 
                var identifier = nameAttribute.DescendantNodes(descendIntoTrivia: true).OfType<IdentifierNameSyntax>().FirstOrDefault();
                if (identifier == null || identifier.ToString() != declaredParameters.ElementAt(i).Name)
                {
                    return ImmutableArray<SyntaxNode>.Empty;
                }
 
                dictionary.Add(originalParameters[i].Name.ToString(), paramNode);
                i++;
            }
 
            // Everything lines up, so permute them.
            var permutedParams = ArrayBuilder<SyntaxNode>.GetInstance();
            foreach (var parameter in reorderedParameters)
            {
                if (dictionary.TryGetValue(parameter.Name, out var permutedParam))
                {
                    permutedParams.Add(permutedParam);
                }
                else
                {
                    permutedParams.Add(XmlElement(
                        XmlElementStartTag(
                            XmlName("param"),
                            List<XmlAttributeSyntax>(new[] { XmlNameAttribute(parameter.Name) })),
                        XmlElementEndTag(XmlName("param"))));
                }
            }
 
            return permutedParams.ToImmutableAndFree();
        }
 
        public override async Task<ImmutableArray<ISymbol>> DetermineCascadedSymbolsFromDelegateInvokeAsync(
            IMethodSymbol symbol,
            Document document,
            CancellationToken cancellationToken)
        {
            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
            using var _ = ArrayBuilder<SyntaxNode>.GetInstance(out var convertedMethodNodes);
 
            foreach (var node in root.DescendantNodes())
            {
                if (!node.IsKind(SyntaxKind.IdentifierName) ||
                    !semanticModel.GetMemberGroup(node, cancellationToken).Any())
                {
                    continue;
                }
 
                var convertedType = (ISymbol?)semanticModel.GetTypeInfo(node, cancellationToken).ConvertedType;
                convertedType = convertedType?.OriginalDefinition;
 
                if (convertedType != null)
                {
                    convertedType = await SymbolFinder.FindSourceDefinitionAsync(convertedType, document.Project.Solution, cancellationToken).ConfigureAwait(false)
                        ?? convertedType;
                }
 
                if (Equals(convertedType, symbol.ContainingType))
                    convertedMethodNodes.Add(node);
            }
 
            var convertedMethodGroups = convertedMethodNodes
                .Select(n => semanticModel.GetSymbolInfo(n, cancellationToken).Symbol)
                .WhereNotNull()
                .ToImmutableArray();
 
            return convertedMethodGroups;
        }
 
        protected override IEnumerable<AbstractFormattingRule> GetFormattingRules(Document document)
            => Formatter.GetDefaultFormattingRules(document).Concat(new ChangeSignatureFormattingRule());
 
        protected override SyntaxNode AddNameToArgument(SyntaxNode newArgument, string name)
        {
            return newArgument switch
            {
                ArgumentSyntax a => a.WithNameColon(NameColon(name)),
                AttributeArgumentSyntax a => a.WithNameColon(NameColon(name)),
                _ => throw ExceptionUtilities.UnexpectedValue(newArgument.Kind())
            };
        }
 
        protected override SyntaxNode CreateExplicitParamsArrayFromIndividualArguments(SeparatedSyntaxList<SyntaxNode> newArguments, int indexInExistingList, IParameterSymbol parameterSymbol)
        {
            RoslynDebug.Assert(parameterSymbol.IsParams);
 
            // These arguments are part of a params array, and should not have any modifiers, making it okay to just use their expressions.
            var listOfArguments = SeparatedList(newArguments.Skip(indexInExistingList).Select(a => ((ArgumentSyntax)a).Expression), newArguments.GetSeparators().Skip(indexInExistingList));
            var initializerExpression = InitializerExpression(SyntaxKind.ArrayInitializerExpression, listOfArguments);
            var objectCreation = ArrayCreationExpression((ArrayTypeSyntax)parameterSymbol.Type.GenerateTypeSyntax(), initializerExpression);
            return Argument(objectCreation);
        }
 
        protected override bool SupportsOptionalAndParamsArrayParametersSimultaneously()
        {
            return true;
        }
 
        protected override SyntaxToken CommaTokenWithElasticSpace()
            => Token(SyntaxKind.CommaToken).WithTrailingTrivia(ElasticSpace);
 
        protected override bool TryGetRecordPrimaryConstructor(INamedTypeSymbol typeSymbol, [NotNullWhen(true)] out IMethodSymbol? primaryConstructor)
            => typeSymbol.TryGetRecordPrimaryConstructor(out primaryConstructor);
 
        protected override ImmutableArray<IParameterSymbol> GetParameters(ISymbol declarationSymbol)
        {
            var declaredParameters = declarationSymbol.GetParameters();
            if (declarationSymbol is INamedTypeSymbol namedTypeSymbol &&
                namedTypeSymbol.TryGetRecordPrimaryConstructor(out var primaryConstructor))
            {
                declaredParameters = primaryConstructor.Parameters;
            }
 
            return declaredParameters;
        }
    }
}
File: ChangeSignature\CSharpChangeSignatureService.cs	Web Access
Project: ..\..\..\src\Features\CSharp\Portable\Microsoft.CodeAnalysis.CSharp.Features.csproj (Microsoft.CodeAnalysis.CSharp.Features)