Add reference handler

src/Facility.LanguageServer/FsdDefinitionUtility.cs

@@ -17,6 +17,68 @@ from field in service.GetDescendants().OfType<ServiceFieldInfo>()
 				select service.FindMember(name)).FirstOrDefault();
 		}
 
+		public static IEnumerable<ServicePart> GetReferencedServicePartsAtPosition(this ServiceInfo service, Position requestPosition, bool includeDeclaration)
+		{
+			var members = service.GetDescendants().OfType<ServiceMemberInfo>().ToList().AsReadOnly();
+
+			// memberAtCursor will be null if the cursor is not on a member name.
+			var memberAtCursor = members
+				.Select(member =>
+				{
+					var part = member.GetPart(ServicePartKind.Name);
+					var name = member.Name;
+
+					return (part, name);
+				})
+				.Where(x => x.part != null && requestPosition >= x.part.Position && requestPosition < x.part.EndPosition)
+				.Select(x => (x.name, x.part))
+				.FirstOrDefault();
+
+			var fields = service.GetDescendants().OfType<ServiceFieldInfo>().ToList().AsReadOnly();
+
+			// fieldTypeNameAtCursor will be null if the cursor is not on a field type name.
+			var fieldTypeNameAtCursor = fields
+				.Select(field =>
+				{
+					var part = field.GetPart(ServicePartKind.TypeName);
+					var typeName = service.GetFieldTypeName(field);
+
+					return (part, typeName);
+				})
+				.Where(x => x.part != null && requestPosition >= x.part.Position && requestPosition < x.part.EndPosition)
+				.Select(x => x.typeName)
+				.FirstOrDefault();
+
+			var referencedFields = fields
+				.Select(field =>
+				{
+					var part = field.GetPart(ServicePartKind.TypeName);
+					var typeName = service.GetFieldTypeName(field);
+
+					var type = service.GetFieldType(field);
+					var memberTypeName = type?.GetMemberTypeName();
+
+					return (part, memberTypeName, typeName);
+				})
+				.Where(x => x.part != null && ((memberAtCursor.name != null && x.memberTypeName == memberAtCursor.name) || x.typeName == fieldTypeNameAtCursor))
+				.Select(x => x.part);
+
+			var referencedMembers = members
+				.Select(member =>
+				{
+					var part = member.GetPart(ServicePartKind.Name);
+					var name = member.Name;
+
+					return (part, name);
+				})
+				.Where(x => x.part != null && x.name == fieldTypeNameAtCursor)
+				.Select(x => x.part);
+
+			return includeDeclaration
+				? referencedFields.Concat(referencedMembers)
+				: referencedFields;
+		}
+
 		private static string GetMemberTypeName(this ServiceTypeInfo type)
 		{
 			switch (type.Kind)
@@ -36,5 +98,15 @@ private static string GetMemberTypeName(this ServiceTypeInfo type)
 			}
 			return null;
 		}
+
+		private static string GetFieldTypeName(this ServiceInfo service, ServiceFieldInfo field)
+		{
+			var type = service.GetFieldType(field);
+
+			while (type?.ValueType is { } valueType)
+				type = valueType;
+
+			return type?.ToString() ?? field.TypeName;
+		}
 	}
 }

src/Facility.LanguageServer/FsdReferenceHandler.cs

@@ -0,0 +1,47 @@
+using Facility.Definition;
+using OmniSharp.Extensions.LanguageServer.Protocol;
+using OmniSharp.Extensions.LanguageServer.Protocol.Client.Capabilities;
+using OmniSharp.Extensions.LanguageServer.Protocol.Document;
+using OmniSharp.Extensions.LanguageServer.Protocol.Models;
+using OmniSharp.Extensions.LanguageServer.Protocol.Server;
+using Range = OmniSharp.Extensions.LanguageServer.Protocol.Models.Range;
+
+namespace Facility.LanguageServer
+{
+	internal sealed class FsdReferenceHandler : FsdRequestHandler, IReferencesHandler
+	{
+		public FsdReferenceHandler(
+			ILanguageServerFacade router,
+			ILanguageServerConfiguration configuration,
+			IDictionary<DocumentUri, ServiceInfo> serviceInfos)
+			: base(router, configuration, serviceInfos)
+		{
+		}
+
+		public ReferenceRegistrationOptions GetRegistrationOptions(ReferenceCapability capability, ClientCapabilities clientCapabilities) =>
+			new ReferenceRegistrationOptions()
+			{
+				DocumentSelector = DocumentSelector,
+			};
+
+		public async Task<LocationContainer> Handle(ReferenceParams request, CancellationToken cancellationToken)
+		{
+			var documentUri = request.TextDocument.Uri;
+			var service = GetService(documentUri);
+			if (service == null)
+				return null;
+
+			var position = new Position(request.Position);
+
+			var serviceParts = service.GetReferencedServicePartsAtPosition(position, request.Context.IncludeDeclaration);
+
+			var locations = serviceParts.Select(part => new Location()
+			{
+				Uri = documentUri,
+				Range = new Range(new Position(part!.Position), new Position(part.EndPosition)),
+			});
+
+			return new LocationContainer(locations);
+		}
+	}
+}

src/Facility.LanguageServer/Program.cs

@@ -26,6 +26,7 @@
 					.AddSingleton<IDictionary<DocumentUri, ServiceInfo>>(serviceInfos))
 			.WithHandler<FsdSyncHandler>()
 			.WithHandler<FsdDefinitionHandler>()
+			.WithHandler<FsdReferenceHandler>()
 			.WithHandler<FsdHoverHandler>()
 			.WithServices(
 				x => x