Add the TypeDefinitionHandler to the LSP

src/OmniSharp.LanguageServerProtocol/Handlers/OmniSharpTypeDefinitionHandler.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using OmniSharp.Extensions.JsonRpc;
+using OmniSharp.Extensions.LanguageServer.Protocol.Client.Capabilities;
+using OmniSharp.Extensions.LanguageServer.Protocol.Document;
+using OmniSharp.Extensions.LanguageServer.Protocol.Models;
+using OmniSharp.Models.GotoTypeDefinition;
+using static OmniSharp.LanguageServerProtocol.Helpers;
+
+namespace OmniSharp.LanguageServerProtocol.Handlers
+{
+    class OmniSharpTypeDefinitionHandler : TypeDefinitionHandlerBase
+    {
+        public static IEnumerable<IJsonRpcHandler> Enumerate(RequestHandlers handlers)
+        {
+            foreach (var (selector, handler) in handlers.OfType<Mef.IRequestHandler<GotoTypeDefinitionRequest, GotoTypeDefinitionResponse>>())
+                if (handler != null)
+                    yield return new OmniSharpTypeDefinitionHandler(handler, selector);
+        }
+
+        private readonly Mef.IRequestHandler<GotoTypeDefinitionRequest, GotoTypeDefinitionResponse> _definitionHandler;
+        private readonly DocumentSelector _documentSelector;
+
+        public OmniSharpTypeDefinitionHandler(Mef.IRequestHandler<GotoTypeDefinitionRequest, GotoTypeDefinitionResponse> definitionHandler, DocumentSelector documentSelector)
+        {
+            _definitionHandler = definitionHandler;
+            _documentSelector = documentSelector;
+        }
+
+        public override async Task<LocationOrLocationLinks> Handle(TypeDefinitionParams request, CancellationToken token)
+        {
+            var omnisharpRequest = new GotoTypeDefinitionRequest()
+            {
+                FileName = FromUri(request.TextDocument.Uri),
+                Column = Convert.ToInt32(request.Position.Character),
+                Line = Convert.ToInt32(request.Position.Line)
+            };
+
+            var omnisharpResponse = await _definitionHandler.Handle(omnisharpRequest);
+
+            if (omnisharpResponse.Definitions == null)
+            {
+                return new LocationOrLocationLinks();
+            }
+
+            return new LocationOrLocationLinks(omnisharpResponse.Definitions.Select<TypeDefinition, LocationOrLocationLink>(definition => new Location()
+            {
+                Uri = definition.Location.FileName,
+                Range = ToRange(definition.Location.Range)
+            }));
+        }
+
+        protected override TypeDefinitionRegistrationOptions CreateRegistrationOptions(TypeDefinitionCapability capability, ClientCapabilities clientCapabilities)
+        {
+            return new TypeDefinitionRegistrationOptions()
+            {
+                DocumentSelector = _documentSelector
+            };
+        }
+    }
+}

src/OmniSharp.LanguageServerProtocol/LanguageServerHost.cs

@@ -371,6 +371,7 @@ internal static void RegisterHandlers(ILanguageServer server, CompositionHost co
             server.Register(s =>
             {
                 foreach (var handler in OmniSharpTextDocumentSyncHandler.Enumerate(handlers, workspace, documentVersions)
+                    .Concat(OmniSharpTypeDefinitionHandler.Enumerate(handlers))
                     .Concat(OmniSharpDefinitionHandler.Enumerate(handlers))
                     .Concat(OmniSharpHoverHandler.Enumerate(handlers))
                     .Concat(OmniSharpCompletionHandler.Enumerate(handlers))