Remove the synchronous GoToImplementation path for C#/VB.

src/EditorFeatures/CSharp/GoToImplementation/CSharpGoToImplementationService.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+#if false
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
 using System.Collections.Generic;
@@ -20,3 +21,4 @@ internal sealed class CSharpGoToImplementationService : AbstractGoToImplementati
         }
     }
 }
+#endif
\ No newline at end of file

src/EditorFeatures/Core/GoToImplementation/AbstractGoToImplementationService.cs

+#if false
 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using System;
@@ -97,3 +98,4 @@ private static IEnumerable<INavigableItem> CreateItemsForImplementation(ISymbol
         }
     }
 }
+#endif
\ No newline at end of file

src/EditorFeatures/Test2/GoToDefinition/GoToDefinitionTests.vb

 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 Imports System.Threading
+Imports System.Threading.Tasks
 Imports Microsoft.CodeAnalysis.Editor.CSharp.GoToDefinition
 Imports Microsoft.CodeAnalysis.Editor.Host
-Imports Microsoft.CodeAnalysis.Editor.VisualBasic.GoToDefinition
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.Utilities.GoToHelpers
-Imports System.Threading.Tasks
+Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
+Imports Microsoft.CodeAnalysis.Editor.VisualBasic.GoToDefinition
+Imports Microsoft.CodeAnalysis.Navigation
+Imports Microsoft.VisualStudio.Composition
+Imports Microsoft.VisualStudio.Text
 
 Namespace Microsoft.CodeAnalysis.Editor.UnitTests.GoToDefinition
     Public Class GoToDefinitionTests
+        Friend Async Function TestAsync(workspaceDefinition As XElement,
+                                        expectedResult As Boolean,
+                                        executeOnDocument As Func(Of Document, Integer, IEnumerable(Of Lazy(Of INavigableItemsPresenter)), Boolean)) As System.Threading.Tasks.Task
+            Using workspace = Await TestWorkspace.CreateAsync(
+                    workspaceDefinition, exportProvider:=GoToTestHelpers.ExportProvider)
+                Dim solution = workspace.CurrentSolution
+                Dim cursorDocument = workspace.Documents.First(Function(d) d.CursorPosition.HasValue)
+                Dim cursorPosition = cursorDocument.CursorPosition.Value
+
+                Dim items As IList(Of INavigableItem) = Nothing
+
+                ' Set up mocks. The IDocumentNavigationService should be called if there is one,
+                ' location and the INavigableItemsPresenter should be called if there are 
+                ' multiple locations.
+
+                ' prepare a notification listener
+                Dim textView = cursorDocument.GetTextView()
+                Dim textBuffer = textView.TextBuffer
+                textView.Caret.MoveTo(New SnapshotPoint(textBuffer.CurrentSnapshot, cursorPosition))
+
+                Dim cursorBuffer = cursorDocument.TextBuffer
+                Dim document = workspace.CurrentSolution.GetDocument(cursorDocument.Id)
+
+                Dim mockDocumentNavigationService = DirectCast(workspace.Services.GetService(Of IDocumentNavigationService)(), MockDocumentNavigationService)
+
+                Dim presenter = New MockNavigableItemsPresenter(Sub(i) items = i)
+                Dim presenters = {New Lazy(Of INavigableItemsPresenter)(Function() presenter)}
+                Dim actualResult = executeOnDocument(document, cursorPosition, presenters)
+
+                Assert.Equal(expectedResult, actualResult)
+
+                Dim expectedLocations As New List(Of FilePathAndSpan)
+
+                For Each testDocument In workspace.Documents
+                    For Each selectedSpan In testDocument.SelectedSpans
+                        expectedLocations.Add(New FilePathAndSpan(testDocument.FilePath, selectedSpan))
+                    Next
+                Next
+
+                expectedLocations.Sort()
+
+                If expectedResult Then
+                    If mockDocumentNavigationService._triedNavigationToSpan Then
+                        Dim definitionDocument = workspace.GetTestDocument(mockDocumentNavigationService._documentId)
+                        Assert.Single(definitionDocument.SelectedSpans)
+                        Assert.Equal(definitionDocument.SelectedSpans.Single(), mockDocumentNavigationService._span)
+
+                        ' The INavigableItemsPresenter should not have been called
+                        Assert.Null(items)
+                    Else
+                        Assert.False(mockDocumentNavigationService._triedNavigationToPosition)
+                        Assert.False(mockDocumentNavigationService._triedNavigationToLineAndOffset)
+                        Assert.NotEmpty(items)
+
+                        Dim actualLocations As New List(Of FilePathAndSpan)
+
+                        For Each location In items
+                            actualLocations.Add(New FilePathAndSpan(location.Document.FilePath, location.SourceSpan))
+                        Next
+
+                        actualLocations.Sort()
+                        Assert.Equal(expectedLocations, actualLocations)
+
+                        ' The IDocumentNavigationService should not have been called
+                        Assert.Null(mockDocumentNavigationService._documentId)
+                    End If
+                Else
+                    Assert.Null(mockDocumentNavigationService._documentId)
+                    Assert.True(items Is Nothing OrElse items.Count = 0)
+                End If
+            End Using
+        End Function
+
         Private Function TestAsync(workspaceDefinition As XElement, Optional expectedResult As Boolean = True) As Tasks.Task
-            Return GoToTestHelpers.TestAsync(workspaceDefinition, expectedResult,
+            Return TestAsync(workspaceDefinition, expectedResult,
                 Function(document As Document, cursorPosition As Integer, presenters As IEnumerable(Of Lazy(Of INavigableItemsPresenter)))
                     Dim goToDefService = If(document.Project.Language = LanguageNames.CSharp,
                         DirectCast(New CSharpGoToDefinitionService(presenters, {}), IGoToDefinitionService),

src/EditorFeatures/Test2/GoToImplementation/GoToImplementationTests.vb

@@ -2,23 +2,49 @@
 
 Imports System.Threading
 Imports System.Threading.Tasks
-Imports Microsoft.CodeAnalysis.Editor.CSharp.GoToImplementation
+Imports Microsoft.CodeAnalysis.Editor.FindUsages
 Imports Microsoft.CodeAnalysis.Editor.Host
 Imports Microsoft.CodeAnalysis.Editor.UnitTests.Utilities.GoToHelpers
-Imports Microsoft.CodeAnalysis.Editor.VisualBasic.GoToImplementation
+Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
 
 Namespace Microsoft.CodeAnalysis.Editor.UnitTests.GoToImplementation
     Public Class GoToImplementationTests
-        Private Function TestAsync(workspaceDefinition As XElement, Optional shouldSucceed As Boolean = True) As Tasks.Task
-            Return GoToTestHelpers.TestAsync(workspaceDefinition, shouldSucceed,
-                Function(document As Document, cursorPosition As Integer, presenters As IEnumerable(Of Lazy(Of INavigableItemsPresenter)))
-                    Dim service = If(document.Project.Language = LanguageNames.CSharp,
-                        DirectCast(New CSharpGoToImplementationService(presenters), IGoToImplementationService),
-                        New VisualBasicGoToImplementationService(presenters))
-
-                    Dim message As String = Nothing
-                    Return service.TryGoToImplementation(document, cursorPosition, CancellationToken.None, message)
-                End Function)
+        Private Async Function TestAsync(workspaceDefinition As XElement, Optional shouldSucceed As Boolean = True) As Tasks.Task
+            Using workspace = Await TestWorkspace.CreateAsync(workspaceDefinition)
+                Dim documentWithCursor = workspace.DocumentWithCursor
+                Dim position = documentWithCursor.CursorPosition.Value
+
+                Dim document = workspace.CurrentSolution.GetDocument(documentWithCursor.Id)
+                Dim findUsagesService = document.GetLanguageService(Of IFindUsagesService)
+
+                Dim context = New SimpleFindUsagesContext(CancellationToken.None)
+                Await findUsagesService.FindImplementationsAsync(document, position, context)
+
+                If Not shouldSucceed Then
+                    Assert.NotNull(context.Message)
+                Else
+                    Dim actualDefinitions = context.GetDefinitions().
+                                                    SelectMany(Function(d) d.SourceSpans).
+                                                    Select(Function(ss) New FilePathAndSpan(ss.Document.FilePath, ss.SourceSpan)).
+                                                    ToList()
+                    actualDefinitions.Sort()
+
+                    Dim expectedDefinitions = workspace.Documents.SelectMany(
+                        Function(d) d.SelectedSpans.Select(Function(ss) New FilePathAndSpan(d.FilePath, ss))).ToList()
+
+                    expectedDefinitions.Sort()
+
+                    Assert.Equal(actualDefinitions.Count, expectedDefinitions.Count)
+
+                    For i = 0 To actualDefinitions.Count - 1
+                        Dim actual = actualDefinitions(i)
+                        Dim expected = expectedDefinitions(i)
+
+                        Assert.True(actual.CompareTo(expected) = 0,
+                                    $"Expected: ({expected}) but got: ({actual})")
+                    Next
+                End If
+            End Using
         End Function
 
         <WpfFact, Trait(Traits.Feature, Traits.Features.GoToImplementation)>

src/EditorFeatures/TestUtilities/Workspaces/TestWorkspace.cs

@@ -93,7 +93,8 @@ protected internal override bool PartialSemanticsEnabled
             get { return _backgroundCompiler != null; }
         }
 
-        public TestHostDocument DocumentWithCursor { get { return Documents.Single(d => d.CursorPosition.HasValue && !d.IsLinkFile); } }
+        public TestHostDocument DocumentWithCursor 
+            => Documents.Single(d => d.CursorPosition.HasValue && !d.IsLinkFile);
 
         protected override void OnDocumentTextChanged(Document document)
         {

src/EditorFeatures/TestUtilities2/Utilities/GoToHelpers/GoToTestHelpers.vb

@@ -17,77 +17,9 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Utilities.GoToHelpers
 
         Public ReadOnly ExportProvider As ExportProvider = MinimalTestExportProvider.CreateExportProvider(Catalog)
 
-        Public Async Function TestAsync(workspaceDefinition As XElement, expectedResult As Boolean, executeOnDocument As Func(Of Document, Integer, IEnumerable(Of Lazy(Of INavigableItemsPresenter)), Boolean)) As System.Threading.Tasks.Task
-            Using workspace = Await TestWorkspace.CreateAsync(workspaceDefinition, exportProvider:=ExportProvider)
-                Dim solution = workspace.CurrentSolution
-                Dim cursorDocument = workspace.Documents.First(Function(d) d.CursorPosition.HasValue)
-                Dim cursorPosition = cursorDocument.CursorPosition.Value
-
-                Dim items As IList(Of INavigableItem) = Nothing
-
-                ' Set up mocks. The IDocumentNavigationService should be called if there is one,
-                ' location and the INavigableItemsPresenter should be called if there are 
-                ' multiple locations.
-
-                ' prepare a notification listener
-                Dim textView = cursorDocument.GetTextView()
-                Dim textBuffer = textView.TextBuffer
-                textView.Caret.MoveTo(New SnapshotPoint(textBuffer.CurrentSnapshot, cursorPosition))
-
-                Dim cursorBuffer = cursorDocument.TextBuffer
-                Dim document = workspace.CurrentSolution.GetDocument(cursorDocument.Id)
-
-                Dim mockDocumentNavigationService = DirectCast(workspace.Services.GetService(Of IDocumentNavigationService)(), MockDocumentNavigationService)
-
-                Dim presenter = New MockNavigableItemsPresenter(Sub(i) items = i)
-                Dim presenters = {New Lazy(Of INavigableItemsPresenter)(Function() presenter)}
-                Dim actualResult = executeOnDocument(document, cursorPosition, presenters)
-
-                Assert.Equal(expectedResult, actualResult)
-
-                Dim expectedLocations As New List(Of FilePathAndSpan)
-
-                For Each testDocument In workspace.Documents
-                    For Each selectedSpan In testDocument.SelectedSpans
-                        expectedLocations.Add(New FilePathAndSpan(testDocument.FilePath, selectedSpan))
-                    Next
-                Next
-
-                expectedLocations.Sort()
-
-                If expectedResult Then
-                    If mockDocumentNavigationService._triedNavigationToSpan Then
-                        Dim definitionDocument = workspace.GetTestDocument(mockDocumentNavigationService._documentId)
-                        Assert.Single(definitionDocument.SelectedSpans)
-                        Assert.Equal(definitionDocument.SelectedSpans.Single(), mockDocumentNavigationService._span)
-
-                        ' The INavigableItemsPresenter should not have been called
-                        Assert.Null(items)
-                    Else
-                        Assert.False(mockDocumentNavigationService._triedNavigationToPosition)
-                        Assert.False(mockDocumentNavigationService._triedNavigationToLineAndOffset)
-                        Assert.NotEmpty(items)
-
-                        Dim actualLocations As New List(Of FilePathAndSpan)
-
-                        For Each location In items
-                            actualLocations.Add(New FilePathAndSpan(location.Document.FilePath, location.SourceSpan))
-                        Next
-
-                        actualLocations.Sort()
-                        Assert.Equal(expectedLocations, actualLocations)
-
-                        ' The IDocumentNavigationService should not have been called
-                        Assert.Null(mockDocumentNavigationService._documentId)
-                    End If
-                Else
-                    Assert.Null(mockDocumentNavigationService._documentId)
-                    Assert.True(items Is Nothing OrElse items.Count = 0)
-                End If
-            End Using
-        End Function
+    End Module
 
-        Private Structure FilePathAndSpan
+    Friend Structure FilePathAndSpan
         Implements IComparable(Of FilePathAndSpan)
 
         Public ReadOnly Property FilePath As String
@@ -112,5 +44,5 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.Utilities.GoToHelpers
             Return $"{FilePath}, {Span}"
         End Function
     End Structure
-    End Module
+
 End Namespace
\ No newline at end of file

src/EditorFeatures/VisualBasic/GoToImplementation/VisualBasicGoToImplementationService.vb

+#If False Then
 ' Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 Imports System.Composition
@@ -16,3 +17,4 @@ Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.GoToImplementation
         End Sub
     End Class
 End Namespace
+#end if 
\ No newline at end of file