public async Task <SignatureHelpViewModel> ComputeSignatureHelpAsync(
SourceText sourceText,
LinePosition linePosition,
CancellationToken cancellationToken)
{
var signatureHelp = new SignatureHelpViewModel();
var position = sourceText.Lines.GetPosition(linePosition);
if (position <= 0)
{
return(signatureHelp);
}
var document = compilationWorkspace.GetSubmissionDocument(sourceText.Container);
var root = await document.GetSyntaxRootAsync(cancellationToken);
var syntaxToken = root.FindToken(position);
var semanticModel = await document.GetSemanticModelAsync(cancellationToken);
var currentNode = syntaxToken.Parent;
do
{
var creationExpression = currentNode as ObjectCreationExpressionSyntax;
if (creationExpression != null && creationExpression.ArgumentList.Span.Contains(position))
{
return(CreateMethodGroupSignatureHelp(
creationExpression,
creationExpression.ArgumentList,
position,
semanticModel));
}
var invocationExpression = currentNode as InvocationExpressionSyntax;
if (invocationExpression != null && invocationExpression.ArgumentList.Span.Contains(position))
{
return(CreateMethodGroupSignatureHelp(
invocationExpression.Expression,
invocationExpression.ArgumentList,
position,
semanticModel));
}
currentNode = currentNode.Parent;
} while (currentNode != null);
return(signatureHelp);
}
static SignatureHelpViewModel CreateMethodGroupSignatureHelp(
ExpressionSyntax expression,
ArgumentListSyntax argumentList,
int position,
SemanticModel semanticModel)
{
var signatureHelp = new SignatureHelpViewModel();
// Happens for object initializers with no preceding parens, as soon as user types comma
if (argumentList == null)
{
return(signatureHelp);
}
int currentArg;
if (TryGetCurrentArgumentIndex(argumentList, position, out currentArg))
{
signatureHelp.ActiveParameter = currentArg;
}
var symbolInfo = semanticModel.GetSymbolInfo(expression);
var bestGuessMethod = symbolInfo.Symbol as IMethodSymbol;
// Include everything by default (global eval context)
var includeInstance = true;
var includeStatic = true;
ITypeSymbol throughType = null;
// When accessing method via some member, only show static methods in static context and vice versa for instance methods.
// This block based on https://github.com/dotnet/roslyn/blob/3b6536f4a616e5f3b8ede940c63663a828e68b5d/src/Features/CSharp/Portable/SignatureHelp/InvocationExpressionSignatureHelpProvider_MethodGroup.cs#L44-L50
if (expression is MemberAccessExpressionSyntax memberAccessExpression)
{
var throughExpression = (memberAccessExpression).Expression;
if (!(throughExpression is BaseExpressionSyntax))
{
throughType = semanticModel.GetTypeInfo(throughExpression).Type;
}
var throughSymbolInfo = semanticModel.GetSymbolInfo(throughExpression);
var throughSymbol = throughSymbolInfo.Symbol ?? throughSymbolInfo.CandidateSymbols.FirstOrDefault();
includeInstance = !throughExpression.IsKind(SyntaxKind.IdentifierName) ||
semanticModel.LookupSymbols(throughExpression.SpanStart, name: throughSymbol.Name).Any(s => !(s is INamedTypeSymbol)) ||
(!(throughSymbol is INamespaceOrTypeSymbol) && semanticModel.LookupSymbols(throughExpression.SpanStart, throughSymbol.ContainingType).Any(s => !(s is INamedTypeSymbol)));
includeStatic = throughSymbol is INamedTypeSymbol ||
(throughExpression.IsKind(SyntaxKind.IdentifierName) &&
semanticModel.LookupNamespacesAndTypes(throughExpression.SpanStart, name: throughSymbol.Name).Any(t => t.GetSymbolType() == throughType));
}
// TODO: Start taking CT in here? Most calls in this method have optional CT arg. Could make this async.
var within = semanticModel.GetEnclosingNamedTypeOrAssembly(position, CancellationToken.None);
var methods = semanticModel
.GetMemberGroup(expression)
.OfType <IMethodSymbol> ()
.Where(m => (m.IsStatic && includeStatic) || (!m.IsStatic && includeInstance))
.Where(m => m.IsAccessibleWithin(within, throughTypeOpt: throughType))
.ToArray();
var signatures = new List <SignatureViewModel> ();
for (var i = 0; i < methods.Length; i++)
{
if (methods [i] == bestGuessMethod)
{
signatureHelp.ActiveSignature = i;
}
var signatureInfo = new SignatureViewModel(methods [i]);
signatures.Add(signatureInfo);
}
signatureHelp.Signatures = signatures.ToArray();
return(signatureHelp);
}