Merge remote-tracking branch 'upstream/features/lspSupport' into merge_lsp_to_master

src/Compilers/Core/Portable/InternalUtilities/StringExtensions.cs

@@ -118,6 +118,8 @@ internal static bool IsValidClrNamespaceName(this string name)
             return lastChar != '.';
         }
 
+        private const string AttributeSuffix = "Attribute";
+
         internal static string GetWithSingleAttributeSuffix(
             this string name,
             bool isCaseSensitive)
@@ -128,7 +130,7 @@ internal static bool IsValidClrNamespaceName(this string name)
                 name = cleaned;
             }
 
-            return name + "Attribute";
+            return name + AttributeSuffix;
         }
 
         internal static bool TryGetWithoutAttributeSuffix(
@@ -150,9 +152,7 @@ internal static bool IsValidClrNamespaceName(this string name)
             bool isCaseSensitive,
             out string result)
         {
-            const string AttributeSuffix = "Attribute";
-            var comparison = isCaseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase;
-            if (name.Length > AttributeSuffix.Length && name.EndsWith(AttributeSuffix, comparison))
+            if (name.HasAttributeSuffix(isCaseSensitive))
             {
                 result = name.Substring(0, name.Length - AttributeSuffix.Length);
                 return true;
@@ -162,6 +162,12 @@ internal static bool IsValidClrNamespaceName(this string name)
             return false;
         }
 
+        internal static bool HasAttributeSuffix(this string name, bool isCaseSensitive)
+        {
+            var comparison = isCaseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase;
+            return name.Length > AttributeSuffix.Length && name.EndsWith(AttributeSuffix, comparison);
+        }
+
         internal static bool IsValidUnicodeString(this string str)
         {
             int i = 0;

src/EditorFeatures/CSharpTest/Completion/CompletionProviders/TypeImportCompletionProviderTests.cs

@@ -907,6 +907,278 @@ class Bat
             AssertRelativeOrder(new List<string>() { "SomeType", "SomeTypeWithLongerName" }, completionList.Items);
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task AttributeTypeInAttributeNameContext()
+        {
+            var file1 = @"
+namespace Foo
+{
+    public class MyAttribute : System.Attribute { }
+    public class MyAttributeWithoutSuffix : System.Attribute { }
+    public class MyClass { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    [$$
+    class Program { }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+
+            await VerifyTypeImportItemExistsAsync(markup, "My", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.MyAttribute");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "MyAttributeWithoutSuffix", inlineDescription: "Foo");  // We intentionally ignore attribute types without proper suffix for perf reason
+            await VerifyTypeImportItemIsAbsentAsync(markup, "MyAttribute", inlineDescription: "Foo");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "MyClass", inlineDescription: "Foo");
+        }
+
+        [InlineData(SourceCodeKind.Regular)]
+        [InlineData(SourceCodeKind.Script)]
+        [WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task CommitAttributeTypeInAttributeNameContext(SourceCodeKind kind)
+        {
+            var file1 = @"
+namespace Foo
+{
+    public class MyAttribute : System.Attribute { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    [$$
+    class Program { }
+}";
+
+            string expectedCodeAfterCommit = @"
+using Foo;
+
+namespace Test
+{
+    [My$$
+    class Program { }
+}";
+
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+            await VerifyCustomCommitProviderAsync(markup, "My", expectedCodeAfterCommit, sourceCodeKind: kind);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task AttributeTypeInNonAttributeNameContext()
+        {
+            var file1 = @"
+namespace Foo
+{
+    public class MyAttribute : System.Attribute { }
+    public class MyAttributeWithoutSuffix : System.Attribute { }
+    public class MyClass { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    class Program 
+    {
+        $$
+    }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+
+            await VerifyTypeImportItemExistsAsync(markup, "MyAttribute", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.MyAttribute");
+            await VerifyTypeImportItemExistsAsync(markup, "MyAttributeWithoutSuffix", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.MyAttributeWithoutSuffix");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "My", inlineDescription: "Foo");
+            await VerifyTypeImportItemExistsAsync(markup, "MyClass", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.MyClass");
+        }
+
+        [InlineData(SourceCodeKind.Regular)]
+        [InlineData(SourceCodeKind.Script)]
+        [WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task CommitAttributeTypeInNonAttributeNameContext(SourceCodeKind kind)
+        {
+            var file1 = @"
+namespace Foo
+{
+    public class MyAttribute : System.Attribute { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    class Program 
+    {
+        $$
+    }
+}";
+
+            string expectedCodeAfterCommit = @"
+using Foo;
+
+namespace Test
+{
+    class Program 
+    {
+        MyAttribute$$
+    }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+            await VerifyCustomCommitProviderAsync(markup, "MyAttribute", expectedCodeAfterCommit, sourceCodeKind: kind);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task AttributeTypeWithoutSuffixInAttributeNameContext()
+        {
+            // attribute suffix isn't capitalized
+            var file1 = @"
+namespace Foo
+{
+    public class Myattribute : System.Attribute { }
+    public class MyClass { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    [$$
+    class Program { }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+
+            await VerifyTypeImportItemExistsAsync(markup, "Myattribute", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.Myattribute");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "My", inlineDescription: "Foo");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "MyClass", inlineDescription: "Foo");
+        }
+
+        [InlineData(SourceCodeKind.Regular)]
+        [InlineData(SourceCodeKind.Script)]
+        [WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task CommitAttributeTypeWithoutSuffixInAttributeNameContext(SourceCodeKind kind)
+        {
+            // attribute suffix isn't capitalized
+            var file1 = @"
+namespace Foo
+{
+    public class Myattribute : System.Attribute { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    [$$
+    class Program { }
+}";
+
+            string expectedCodeAfterCommit = @"
+using Foo;
+
+namespace Test
+{
+    [Myattribute$$
+    class Program { }
+}";
+
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+            await VerifyCustomCommitProviderAsync(markup, "Myattribute", expectedCodeAfterCommit, sourceCodeKind: kind);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task AttributeTypeWithoutSuffixInNonAttributeNameContext()
+        {
+            // attribute suffix isn't capitalized
+            var file1 = @"
+namespace Foo
+{
+    public class Myattribute : System.Attribute { }
+    public class MyClass { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    class Program 
+    {
+        $$
+    }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+
+            await VerifyTypeImportItemExistsAsync(markup, "Myattribute", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.Myattribute");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "My", inlineDescription: "Foo");
+            await VerifyTypeImportItemExistsAsync(markup, "MyClass", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.MyClass");
+        }
+
+        [InlineData(SourceCodeKind.Regular)]
+        [InlineData(SourceCodeKind.Script)]
+        [WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task CommitAttributeTypeWithoutSuffixInNonAttributeNameContext(SourceCodeKind kind)
+        {
+            // attribute suffix isn't capitalized
+            var file1 = @"
+namespace Foo
+{
+    public class Myattribute : System.Attribute { }
+}";
+
+            var file2 = @"
+namespace Test
+{
+    class Program 
+    {
+        $$
+    }
+}";
+
+            string expectedCodeAfterCommit = @"
+using Foo;
+
+namespace Test
+{
+    class Program 
+    {
+        Myattribute$$
+    }
+}";
+            var markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.CSharp);
+            await VerifyCustomCommitProviderAsync(markup, "Myattribute", expectedCodeAfterCommit, sourceCodeKind: kind);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.Completion)]
+        [WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")]
+        public async Task VBAttributeTypeWithoutSuffixInAttributeNameContext()
+        {
+            var file1 = @"
+Namespace Foo
+    Public Class Myattribute
+        Inherits System.Attribute
+    End Class
+    Public Class MyVBClass
+    End Class
+End Namespace";
+
+            var file2 = @"
+namespace Test
+{
+    [$$
+    class Program 
+    {
+    }
+}";
+
+            var markup = CreateMarkupForProjecWithProjectReference(file2, file1, LanguageNames.CSharp, LanguageNames.VisualBasic);
+
+            await VerifyTypeImportItemExistsAsync(markup, "Myattribute", glyph: (int)Glyph.ClassPublic, inlineDescription: "Foo", expectedDescriptionOrNull: "class Foo.Myattribute");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "My", inlineDescription: "Foo");
+            await VerifyTypeImportItemIsAbsentAsync(markup, "MyVBClass", inlineDescription: "Foo");
+        }
+
+
         private static void AssertRelativeOrder(List<string> expectedTypesInRelativeOrder, ImmutableArray<CompletionItem> allCompletionItems)
         {
             var hashset = new HashSet<string>(expectedTypesInRelativeOrder);
@@ -919,9 +1191,9 @@ private static void AssertRelativeOrder(List<string> expectedTypesInRelativeOrde
             }
         }
 
-        private Task VerifyTypeImportItemExistsAsync(string markup, string expectedItem, int glyph, string inlineDescription, string displayTextSuffix = null)
+        private Task VerifyTypeImportItemExistsAsync(string markup, string expectedItem, int glyph, string inlineDescription, string displayTextSuffix = null, string expectedDescriptionOrNull = null)
         {
-            return VerifyItemExistsAsync(markup, expectedItem, displayTextSuffix: displayTextSuffix, glyph: glyph, inlineDescription: inlineDescription);
+            return VerifyItemExistsAsync(markup, expectedItem, displayTextSuffix: displayTextSuffix, glyph: glyph, inlineDescription: inlineDescription, expectedDescriptionOrNull: expectedDescriptionOrNull);
         }
 
 

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/CommitManager.cs

@@ -172,7 +172,7 @@ internal CommitManager(ITextView textView, RecentItemsManager recentItemsManager
                 roslynItem, completionListSpan, commitChar, triggerSnapshot, serviceRules,
                 filterText, cancellationToken);
 
-            _recentItemsManager.MakeMostRecentItem(roslynItem.DisplayText);
+            _recentItemsManager.MakeMostRecentItem(roslynItem.FilterText);
             return new AsyncCompletionData.CommitResult(isHandled: true, commitBehavior);
         }
 

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/Helpers.cs

@@ -4,6 +4,8 @@
 using Microsoft.VisualStudio.Text;
 using AsyncCompletionData = Microsoft.VisualStudio.Language.Intellisense.AsyncCompletion.Data;
 using RoslynTrigger = Microsoft.CodeAnalysis.Completion.CompletionTrigger;
+using RoslynCompletionItem = Microsoft.CodeAnalysis.Completion.CompletionItem;
+using VSCompletionItem = Microsoft.VisualStudio.Language.Intellisense.AsyncCompletion.Data.CompletionItem;
 
 namespace Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.AsyncCompletion
 {
@@ -63,7 +65,7 @@ internal static CompletionFilterReason GetFilterReason(AsyncCompletionData.Compl
             }
         }
 
-        internal static bool IsFilterCharacter(CompletionItem item, char ch, string textTypedSoFar)
+        internal static bool IsFilterCharacter(RoslynCompletionItem item, char ch, string textTypedSoFar)
         {
             // First see if the item has any specific filter rules it wants followed.
             foreach (var rule in item.Rules.FilterCharacterRules)
@@ -97,5 +99,15 @@ internal static bool IsFilterCharacter(CompletionItem item, char ch, string text
 
             return false;
         }
+
+        // This is a temporarily method to support preference of IntelliCode items comparing to non-IntelliCode items.
+        // We expect that Editor will intorduce this support and we will get rid of relying on the "★" then.
+        internal static bool IsPreferredItem(this RoslynCompletionItem completionItem)
+            => completionItem.DisplayText.StartsWith("★");
+
+        // This is a temporarily method to support preference of IntelliCode items comparing to non-IntelliCode items.
+        // We expect that Editor will intorduce this support and we will get rid of relying on the "★" then.
+        internal static bool IsPreferredItem(this VSCompletionItem completionItem)
+            => completionItem.DisplayText.StartsWith("★");
     }
 }

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/ItemManager.cs

@@ -293,12 +293,12 @@ private static bool IsAfterDot(ITextSnapshot snapshot, ITrackingSpan applicableT
             if (bestItem != null)
             {
                 selectedItemIndex = itemsInList.IndexOf(i => Equals(i.FilterResult.CompletionItem, bestItem));
-                var deduplicatedList = matchingItems.Where(r => !r.DisplayText.StartsWith("★"));
+                var deduplicatedListCount = matchingItems.Where(r => !r.IsPreferredItem()).Count();
                 if (selectedItemIndex > -1 &&
-                    deduplicatedList.Count() == 1 &&
+                    deduplicatedListCount == 1 &&
                     filterText.Length > 0)
                 {
-                    var uniqueItemIndex = itemsInList.IndexOf(i => Equals(i.FilterResult.CompletionItem, deduplicatedList.First()));
+                    var uniqueItemIndex = itemsInList.IndexOf(i => Equals(i.FilterResult.CompletionItem, bestItem));
                     uniqueItem = highlightedList[uniqueItemIndex].CompletionItem;
                 }
             }
@@ -391,7 +391,7 @@ private static bool IsAfterDot(ITextSnapshot snapshot, ITrackingSpan applicableT
                 hardSelect = false;
             }
 
-            var deduplicatedListCount = matchingItems.Where(r => !r.VSCompletionItem.DisplayText.StartsWith("★")).Count();
+            var deduplicatedListCount = matchingItems.Where(r => !r.VSCompletionItem.IsPreferredItem()).Count();
 
             return new FilteredCompletionModel(
                 highlightedList, index, filters,
@@ -493,7 +493,8 @@ private static bool ShouldBeFilteredOutOfCompletionList(VSCompletionItem item, I
                 var mruIndex1 = GetRecentItemIndex(recentItems, bestItem);
                 var mruIndex2 = GetRecentItemIndex(recentItems, chosenItem);
 
-                if (mruIndex2 < mruIndex1)
+                if ((mruIndex2 < mruIndex1) ||
+                    (mruIndex2 == mruIndex1 && !bestItem.IsPreferredItem() && chosenItem.IsPreferredItem()))
                 {
                     bestItem = chosenItem;
                 }
@@ -513,7 +514,8 @@ private static bool ShouldBeFilteredOutOfCompletionList(VSCompletionItem item, I
                 var bestItemPriority = bestItem.Rules.MatchPriority;
                 var currentItemPriority = chosenItem.Rules.MatchPriority;
 
-                if (currentItemPriority > bestItemPriority)
+                if ((currentItemPriority > bestItemPriority) ||
+                    ((currentItemPriority == bestItemPriority) && !bestItem.IsPreferredItem() && chosenItem.IsPreferredItem()))
                 {
                     bestItem = chosenItem;
                 }
@@ -524,7 +526,7 @@ private static bool ShouldBeFilteredOutOfCompletionList(VSCompletionItem item, I
 
         internal static int GetRecentItemIndex(ImmutableArray<string> recentItems, RoslynCompletionItem item)
         {
-            var index = recentItems.IndexOf(item.DisplayText);
+            var index = recentItems.IndexOf(item.FilterText);
             return -index;
         }
 
@@ -565,7 +567,13 @@ internal static bool IsBetterDeletionMatch(FilterResult result1, FilterResult re
                 {
                     return true;
                 }
+
+                if (result1.CompletionItem.IsPreferredItem() && !result2.CompletionItem.IsPreferredItem())
+                {
+                    return true;
                 }
+            }
+
             return false;
         }
 

src/EditorFeatures/Test2/IntelliSense/CSharpCompletionCommandHandlerTests.vb

@@ -5057,13 +5057,112 @@ class C
 
                 state.SendTypeChars(".len")
                 Await state.AssertCompletionSession()
-                state.AssertCompletionItemsContainAll({"Length", "★ Length3", "★ Length2"})
+                state.AssertCompletionItemsContainAll({"Length", "★ Length", "★ Length2"})
                 state.SendCommitUniqueCompletionListItem()
                 Await state.AssertNoCompletionSession()
                 Assert.Contains("s.Length", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
             End Using
         End Function
 
+        ' Implementation for the Modern completion only
+        <InlineData(CompletionImplementation.Modern)>
+        <WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function IntelliCodeItemPreferredAfterCommitingIntelliCodeItem(completionImplementation As CompletionImplementation) As Task
+            Dim provider = New IntelliCodeMockProvider()
+            Using state = TestStateFactory.CreateCSharpTestState(completionImplementation,
+                              <Document>
+class C
+{
+    void Method()
+    {
+        var s = "";
+        s$$
+    }
+}
+                              </Document>, {provider})
+
+                state.Workspace.Options = state.Workspace.Options.WithChangedOption(
+                    CompletionOptions.TriggerOnDeletion, LanguageNames.CSharp, True)
+
+                state.SendTypeChars(".nor")
+                Await state.AssertCompletionSession()
+                state.AssertCompletionItemsContainAll({"Normalize", "★ Normalize"})
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+                state.SendTab()
+                Await state.AssertNoCompletionSession()
+                Assert.Contains("s.Normalize", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+                For i = 1 To "ze".Length
+                    state.SendBackspace()
+                Next
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+
+                state.SendEscape()
+                For i = 1 To "Normali".Length
+                    state.SendBackspace()
+                Next
+                state.SendEscape()
+                Assert.Contains("s.", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+                state.SendEscape()
+
+                state.SendTypeChars("n")
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+            End Using
+        End Function
+
+        ' Implementation for the Modern completion only
+        <InlineData(CompletionImplementation.Modern)>
+        <WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function IntelliCodeItemPreferredAfterCommitingNonIntelliCodeItem(completionImplementation As CompletionImplementation) As Task
+            Dim provider = New IntelliCodeMockProvider()
+            Using state = TestStateFactory.CreateCSharpTestState(completionImplementation,
+                              <Document>
+class C
+{
+    void Method()
+    {
+        var s = "";
+        s$$
+    }
+}
+                              </Document>, {provider})
+
+                state.Workspace.Options = state.Workspace.Options.WithChangedOption(
+                    CompletionOptions.TriggerOnDeletion, LanguageNames.CSharp, True)
+
+                state.SendTypeChars(".nor")
+                Await state.AssertCompletionSession()
+                state.AssertCompletionItemsContainAll({"Normalize", "★ Normalize"})
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+
+                state.NavigateToDisplayText("Normalize")
+                state.SendTab()
+
+                Await state.AssertNoCompletionSession()
+                Assert.Contains("s.Normalize", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+                For i = 1 To "ze".Length
+                    state.SendBackspace()
+                Next
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+
+                state.SendEscape()
+                For i = 1 To "Normali".Length
+                    state.SendBackspace()
+                Next
+                state.SendEscape()
+                Assert.Contains("s.", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+                state.SendEscape()
+
+                state.SendTypeChars("n")
+                Await state.AssertSelectedCompletionItem("★ Normalize", displayTextSuffix:="()")
+            End Using
+        End Function
+
         <WorkItem(35614, "https://github.com/dotnet/roslyn/issues/35614")>
         <MemberData(NameOf(AllCompletionImplementations))>
         <WpfTheory, Trait(Traits.Feature, Traits.Features.Completion)>
@@ -5451,33 +5550,37 @@ class C
 
             Public Overrides Function ProvideCompletionsAsync(context As CompletionContext) As Task
                 context.AddItem(CompletionItem.Create(displayText:="★ Length", filterText:="Length"))
-                context.AddItem(CompletionItem.Create(displayText:="★ Normalize", filterText:="Normalize"))
+                context.AddItem(CompletionItem.Create(displayText:="★ Normalize", filterText:="Normalize", displayTextSuffix:="()"))
                 context.AddItem(CompletionItem.Create(displayText:="Length", filterText:="Length"))
-                context.AddItem(CompletionItem.Create(displayText:="ToString()", filterText:="ToString"))
-                context.AddItem(CompletionItem.Create(displayText:="First()", filterText:="First"))
+                context.AddItem(CompletionItem.Create(displayText:="ToString", filterText:="ToString", displayTextSuffix:="()"))
+                context.AddItem(CompletionItem.Create(displayText:="First", filterText:="First", displayTextSuffix:="()"))
                 Return Task.CompletedTask
             End Function
 
             Public Overrides Function ShouldTriggerCompletion(text As SourceText, caretPosition As Integer, trigger As CompletionTrigger, options As OptionSet) As Boolean
                 Return True
             End Function
+
+            Public Overrides Function GetChangeAsync(document As Document, item As CompletionItem, commitKey As Char?, cancellationToken As CancellationToken) As Task(Of CompletionChange)
+                Dim commitText = item.DisplayText
+                If commitText.StartsWith("★") Then
+                    ' remove the star and the following space
+                    commitText = commitText.Substring(2)
+                End If
+
+                Return Task.FromResult(CompletionChange.Create(New TextChange(item.Span, commitText)))
+            End Function
         End Class
 
         ' Simulates a situation where IntelliCode provides items not included into the Rolsyn original list.
         ' We want to ignore these items in CommitIfUnique.
         ' This situation should not happen. Tests with this provider were added to cover protective scenarios.
         Private Class IntelliCodeMockWeirdProvider
-            Inherits CompletionProvider
+            Inherits IntelliCodeMockProvider
 
-            Public Overrides Function ProvideCompletionsAsync(context As CompletionContext) As Task
-                context.AddItem(CompletionItem.Create(displayText:="★ Length2", filterText:="Length2"))
-                context.AddItem(CompletionItem.Create(displayText:="Length", filterText:="Length"))
-                context.AddItem(CompletionItem.Create(displayText:="★ Length3", filterText:="Length3"))
-                Return Task.CompletedTask
-            End Function
-
-            Public Overrides Function ShouldTriggerCompletion(text As SourceText, caretPosition As Integer, trigger As CompletionTrigger, options As OptionSet) As Boolean
-                Return True
+            Public Overrides Async Function ProvideCompletionsAsync(context As CompletionContext) As Task
+                Await MyBase.ProvideCompletionsAsync(context).ConfigureAwait(False)
+                context.AddItem(CompletionItem.Create(displayText:="★ Length2", filterText:="Length"))
             End Function
         End Class
     End Class

src/EditorFeatures/TestUtilities/Completion/AbstractCompletionProviderTests.cs

@@ -9,7 +9,6 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Completion;
-using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.AsyncCompletion;
 using Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces;
 using Microsoft.CodeAnalysis.LanguageServices;

src/EditorFeatures/TestUtilities2/Intellisense/ModernCompletionTestState.vb

@@ -153,7 +153,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
             Dim completionItems = session.GetComputedItems(CancellationToken.None)
             ' During the computation we can explicitly dismiss the session or we can return no items.
             ' Each of these conditions mean that there is no active completion.
-            Assert.True(session.IsDismissed OrElse completionItems.Items.Count() = 0)
+            Assert.True(session.IsDismissed OrElse completionItems.Items.Count() = 0, "AssertNoCompletionSession")
         End Function
 
         Public Overrides Sub AssertNoCompletionSessionWithNoBlock()
@@ -188,7 +188,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
 
             Await WaitForAsynchronousOperationsAsync()
             Dim session = GetExportedValue(Of IAsyncCompletionBroker)().GetSession(view)
-            Assert.NotNull(session)
+            Assert.True(session IsNot Nothing, "AssertCompletionSession")
         End Function
 
         Public Overrides Async Function AssertCompletionSessionAfterTypingHash() As Task
@@ -291,15 +291,6 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
             End If
         End Sub
 
-        Private Function GetRoslynCompletionItemOpt(editorCompletionItem As Data.CompletionItem) As CompletionItem
-            Dim roslynCompletionItem As CompletionItem = Nothing
-            If editorCompletionItem?.Properties.TryGetProperty(RoslynItem, roslynCompletionItem) Then
-                Return roslynCompletionItem
-            End If
-
-            Return Nothing
-        End Function
-
         Public Overrides Function GetCompletionItems() As IList(Of CompletionItem)
             WaitForAsynchronousOperationsAsync()
             Dim session = GetExportedValue(Of IAsyncCompletionBroker)().GetSession(TextView)

src/EditorFeatures/TestUtilities2/Intellisense/TestStateBase.vb

@@ -259,6 +259,31 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
 
         Public MustOverride Function WaitForUIRenderedAsync() As Task
 
+        Public Sub NavigateToDisplayText(targetText As String)
+            Dim currentText = GetSelectedItem().DisplayText
+
+            ' GetComputedItems provided by the Editor for tests does not guarantee that 
+            ' the order of items match the order of items actually displayed in the completion popup.
+            ' For example, they put starred items (intellicode) below non-starred ones.
+            ' And the order they display those items in the UI is opposite.
+            ' Therefore, we do the full traverse: down to the bottom and if not found up to the top.
+            Do While currentText <> targetText
+                SendDownKey()
+                Dim newText = GetSelectedItem().DisplayText
+                If currentText = newText Then
+                    ' Nothing found on going down. Try going up
+                    Do While currentText <> targetText
+                        SendUpKey()
+                        newText = GetSelectedItem().DisplayText
+                        Assert.True(newText <> currentText, "Reached the bottom, then the top and didn't find the match")
+                        currentText = newText
+                    Loop
+                End If
+
+                currentText = newText
+            Loop
+        End Sub
+
 #End Region
 
 #Region "Signature Help Operations"

src/EditorFeatures/VisualBasicTest/Completion/CompletionProviders/TypeImportCompletionProviderTests.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 Microsoft.CodeAnalysis.Completion
+Imports Microsoft.CodeAnalysis.Editor.UnitTests
+Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
+Imports Microsoft.CodeAnalysis.Experiments
+Imports Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
+Imports Microsoft.VisualStudio.Composition
+
+Namespace Microsoft.CodeAnalysis.Editor.VisualBasic.UnitTests.Completion.CompletionProviders
+
+    <UseExportProvider>
+    Public Class TypeImportCompletionProviderTests
+        Inherits AbstractVisualBasicCompletionProviderTests
+
+        Public Sub New(workspaceFixture As VisualBasicTestWorkspaceFixture)
+            MyBase.New(workspaceFixture)
+        End Sub
+
+        Private Property ShowImportCompletionItemsOptionValue As Boolean = True
+
+        Protected Overrides Sub SetWorkspaceOptions(workspace As TestWorkspace)
+            workspace.Options = workspace.Options.WithChangedOption(CompletionOptions.ShowItemsFromUnimportedNamespaces, LanguageNames.VisualBasic, ShowImportCompletionItemsOptionValue)
+        End Sub
+
+        Protected Overrides Function GetExportProvider() As ExportProvider
+            Return ExportProviderCache.GetOrCreateExportProviderFactory(TestExportProvider.EntireAssemblyCatalogWithCSharpAndVisualBasic.WithPart(GetType(TestExperimentationService))).CreateExportProvider()
+        End Function
+
+        Friend Overrides Function CreateCompletionProvider() As CompletionProvider
+            Return New TypeImportCompletionProvider()
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")>
+        Public Async Function AttributeTypeInAttributeNameContext() As Task
+
+            Dim file1 = <Text>
+Namespace Foo
+    Public Class MyAttribute
+        Inherits System.Attribute
+    End Class
+
+    Public Class MyVBClass
+    End Class
+
+    Public Class MyAttributeWithoutSuffix
+        Inherits System.Attribute
+    End Class
+End Namespace</Text>.Value
+
+            Dim file2 = <Text><![CDATA[
+Public Class Bar
+    <$$
+    Sub Main()
+
+    End Sub
+End Class]]></Text>.Value
+
+            Dim markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.VisualBasic)
+            Await VerifyItemExistsAsync(markup, "My", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.MyAttribute")
+            Await VerifyItemIsAbsentAsync(markup, "MyAttributeWithoutSuffix", inlineDescription:="Foo") ' We intentionally ignore attribute types without proper suffix for perf reason
+            Await VerifyItemIsAbsentAsync(markup, "MyAttribute", inlineDescription:="Foo")
+            Await VerifyItemIsAbsentAsync(markup, "MyVBClass", inlineDescription:="Foo")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")>
+        Public Async Function AttributeTypeInNonAttributeNameContext() As Task
+
+            Dim file1 = <Text>
+Namespace Foo
+    Public Class MyAttribute
+        Inherits System.Attribute
+    End Class
+
+    Public Class MyVBClass
+    End Class
+
+    Public Class MyAttributeWithoutSuffix
+        Inherits System.Attribute
+End Namespace</Text>.Value
+
+            Dim file2 = <Text><![CDATA[
+Public Class Bar
+    Sub Main()
+        Dim x As $$
+    End Sub
+End Class]]></Text>.Value
+
+            Dim markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.VisualBasic)
+            Await VerifyItemExistsAsync(markup, "MyAttribute", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.MyAttribute")
+            Await VerifyItemExistsAsync(markup, "MyAttributeWithoutSuffix", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.MyAttributeWithoutSuffix")
+            Await VerifyItemExistsAsync(markup, "MyVBClass", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.MyVBClass")
+            Await VerifyItemIsAbsentAsync(markup, "My", inlineDescription:="Foo")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")>
+        Public Async Function AttributeTypeInAttributeNameContext2() As Task
+
+            ' attribute suffix isn't capitalized
+            Dim file1 = <Text>
+Namespace Foo
+    Public Class Myattribute
+        Inherits System.Attribute
+    End Class
+End Namespace</Text>.Value
+
+            Dim file2 = <Text><![CDATA[
+Public Class Bar
+    <$$
+    Sub Main()
+
+    End Sub
+End Class]]></Text>.Value
+
+            Dim markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.VisualBasic)
+            Await VerifyItemExistsAsync(markup, "My", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.Myattribute")
+            Await VerifyItemIsAbsentAsync(markup, "Myattribute", inlineDescription:="Foo")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(35540, "https://github.com/dotnet/roslyn/issues/35540")>
+        Public Async Function CSharpAttributeTypeWithoutSuffixInAttributeNameContext() As Task
+
+            ' attribute suffix isn't capitalized
+            Dim file1 = <Text>
+namespace Foo
+{
+    public class Myattribute : System.Attribute { }
+}</Text>.Value
+
+            Dim file2 = <Text><![CDATA[
+Public Class Bar
+    <$$
+    Sub Main()
+
+    End Sub
+End Class]]></Text>.Value
+
+            Dim markup = CreateMarkupForProjecWithProjectReference(file2, file1, LanguageNames.VisualBasic, LanguageNames.CSharp)
+            Await VerifyItemExistsAsync(markup, "My", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", expectedDescriptionOrNull:="Class Foo.Myattribute")
+            Await VerifyItemIsAbsentAsync(markup, "Myattribute", inlineDescription:="Foo")
+        End Function
+
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(35124, "https://github.com/dotnet/roslyn/issues/35124")>
+        Public Async Function GenericTypeShouldDisplayProperVBSyntax() As Task
+
+            Dim file1 = <Text>
+Namespace Foo
+    Public Class MyGenericClass(Of T)
+    End Class
+End Namespace</Text>.Value
+
+            Dim file2 = <Text><![CDATA[
+Public Class Bar
+    Sub Main()
+        Dim x As $$
+    End Sub
+End Class]]></Text>.Value
+
+            Dim markup = CreateMarkupForSingleProject(file2, file1, LanguageNames.VisualBasic)
+            Await VerifyItemExistsAsync(markup, "MyGenericClass", glyph:=Glyph.ClassPublic, inlineDescription:="Foo", displayTextSuffix:="(Of ...)", expectedDescriptionOrNull:="Class Foo.MyGenericClass(Of T)")
+        End Function
+    End Class
+End Namespace

src/Features/CSharp/Portable/Completion/CompletionProviders/ImportCompletion/CSharpTypeImportCompletionServiceFactory.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.
+
+using System.Composition;
+using Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+
+namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers
+{
+    [ExportLanguageServiceFactory(typeof(ITypeImportCompletionService), LanguageNames.CSharp), Shared]
+    internal sealed class CSharpTypeImportCompletionServiceFactory : ILanguageServiceFactory
+    {
+        [ImportingConstructor]
+        public CSharpTypeImportCompletionServiceFactory()
+        {
+        }
+
+        public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
+        {
+            return new CSharpTypeImportCompletionService(languageServices.WorkspaceServices.Workspace);
+        }
+
+        private class CSharpTypeImportCompletionService : AbstractTypeImportCompletionService
+        {
+            public CSharpTypeImportCompletionService(Workspace workspace)
+                : base(workspace)
+            {
+            }
+
+            protected override string GenericTypeSuffix
+                => "<>";
+
+            protected override bool IsCaseSensitive => true;
+        }
+    }
+}

src/Features/Core/Portable/Completion/Providers/AbstractTypeImportCompletionProvider.cs → src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractTypeImportCompletionProvider.cs

@@ -9,6 +9,7 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.AddImports;
 using Microsoft.CodeAnalysis.Completion.Log;
+using Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion;
 using Microsoft.CodeAnalysis.Debugging;
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Experiments;
@@ -78,7 +79,7 @@ private async Task AddCompletionItemsAsync(CompletionContext completionContext,
             var document = completionContext.Document;
             var project = document.Project;
             var workspace = project.Solution.Workspace;
-            var typeImportCompletionService = workspace.Services.GetService<ITypeImportCompletionService>();
+            var typeImportCompletionService = document.GetLanguageService<ITypeImportCompletionService>();
 
             // Find all namespaces in scope at current cursor location, 
             // which will be used to filter so the provider only returns out-of-scope types.
@@ -86,7 +87,7 @@ private async Task AddCompletionItemsAsync(CompletionContext completionContext,
 
             // Get completion items from current project. 
             var compilation = await project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
-            await typeImportCompletionService.GetTopLevelTypesAsync(project, HandlePublicAndInternalItem, cancellationToken)
+            await typeImportCompletionService.GetTopLevelTypesAsync(project, syntaxContext, HandlePublicAndInternalItem, cancellationToken)
                 .ConfigureAwait(false);
 
             // Get declarations from directly referenced projects and PEs
@@ -105,6 +106,7 @@ await typeImportCompletionService.GetTopLevelTypesAsync(project, HandlePublicAnd
                     {
                         await typeImportCompletionService.GetTopLevelTypesAsync(
                             assemblyProject,
+                            syntaxContext,
                             GetHandler(compilation.Assembly, assembly),
                             cancellationToken).ConfigureAwait(false);
                     }
@@ -114,6 +116,7 @@ await typeImportCompletionService.GetTopLevelTypesAsync(project, HandlePublicAnd
                             project.Solution,
                             compilation,
                             peReference,
+                            syntaxContext,
                             GetHandler(compilation.Assembly, assembly),
                             cancellationToken);
                     }
@@ -125,24 +128,24 @@ await typeImportCompletionService.GetTopLevelTypesAsync(project, HandlePublicAnd
             return;
 
             // Decide which item handler to use based on IVT
-            Action<TypeImportCompletionItemInfo> GetHandler(IAssemblySymbol assembly, IAssemblySymbol referencedAssembly)
+            Action<CompletionItem, bool> GetHandler(IAssemblySymbol assembly, IAssemblySymbol referencedAssembly)
                 => assembly.IsSameAssemblyOrHasFriendAccessTo(referencedAssembly)
-                        ? (Action<TypeImportCompletionItemInfo>)HandlePublicAndInternalItem
+                        ? (Action<CompletionItem, bool>)HandlePublicAndInternalItem
                         : HandlePublicItem;
 
             // Add only public types to completion list
-            void HandlePublicItem(TypeImportCompletionItemInfo itemInfo)
-                => AddItems(itemInfo, isInternalsVisible: false, completionContext, namespacesInScope, telemetryCounter);
+            void HandlePublicItem(CompletionItem item, bool isPublic)
+                => AddItems(item, isPublic, isInternalsVisible: false, completionContext, namespacesInScope, telemetryCounter);
 
             // Add both public and internal types to completion list
-            void HandlePublicAndInternalItem(TypeImportCompletionItemInfo itemInfo)
-                => AddItems(itemInfo, isInternalsVisible: true, completionContext, namespacesInScope, telemetryCounter);
+            void HandlePublicAndInternalItem(CompletionItem item, bool isPublic)
+                => AddItems(item, isPublic, isInternalsVisible: true, completionContext, namespacesInScope, telemetryCounter);
 
-            static void AddItems(TypeImportCompletionItemInfo itemInfo, bool isInternalsVisible, CompletionContext completionContext, HashSet<string> namespacesInScope, TelemetryCounter counter)
+            static void AddItems(CompletionItem item, bool isPublic, bool isInternalsVisible, CompletionContext completionContext, HashSet<string> namespacesInScope, TelemetryCounter counter)
             {
-                if (itemInfo.IsPublic || isInternalsVisible)
+                if (isPublic || isInternalsVisible)
                 {
-                    var containingNamespace = TypeImportCompletionItem.GetContainingNamespace(itemInfo.Item);
+                    var containingNamespace = TypeImportCompletionItem.GetContainingNamespace(item);
                     if (!namespacesInScope.Contains(containingNamespace))
                     {
                         // We can return cached item directly, item's span will be fixed by completion service.
@@ -150,7 +153,7 @@ static void AddItems(TypeImportCompletionItemInfo itemInfo, bool isInternalsVisi
                         // On the other hand, because of this (i.e. mutating the  span of cached item for each run),
                         // the provider can not be used as a service by components that might be run in parallel 
                         // with completion, which would be a race.
-                        completionContext.AddItem(itemInfo.Item);
+                        completionContext.AddItem(item);
                         counter.ItemsCount++; ;
                     }
                 }

src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractTypeImportCompletionService.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.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.FindSymbols;
+using Microsoft.CodeAnalysis.PooledObjects;
+using Microsoft.CodeAnalysis.Shared.Extensions;
+using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
+using Roslyn.Utilities;
+
+namespace Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion
+{
+    internal abstract partial class AbstractTypeImportCompletionService : ITypeImportCompletionService
+    {
+        private ITypeImportCompletionCacheService CacheService { get; }
+
+        protected abstract string GenericTypeSuffix { get; }
+
+        protected abstract bool IsCaseSensitive { get; }
+
+        internal AbstractTypeImportCompletionService(Workspace workspace)
+        {
+            CacheService = workspace.Services.GetService<ITypeImportCompletionCacheService>();
+        }
+
+        public async Task GetTopLevelTypesAsync(
+            Project project,
+            SyntaxContext syntaxContext,
+            Action<CompletionItem, bool> handleItem,
+            CancellationToken cancellationToken)
+        {
+            if (!project.SupportsCompilation)
+            {
+                throw new ArgumentException(nameof(project));
+            }
+
+            var compilation = await project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
+
+            // Since we only need top level types from source, therefore we only care if source symbol checksum changes.
+            var checksum = await SymbolTreeInfo.GetSourceSymbolsChecksumAsync(project, cancellationToken).ConfigureAwait(false);
+
+            GetAccessibleTopLevelTypesWorker(
+                project.Id,
+                compilation.Assembly,
+                checksum,
+                syntaxContext,
+                handleItem,
+                CacheService.ProjectItemsCache,
+                cancellationToken);
+        }
+
+        public void GetTopLevelTypesFromPEReference(
+            Solution solution,
+            Compilation compilation,
+            PortableExecutableReference peReference,
+            SyntaxContext syntaxContext,
+            Action<CompletionItem, bool> handleItem,
+            CancellationToken cancellationToken)
+        {
+            var key = GetReferenceKey(peReference);
+            if (key == null)
+            {
+                // Can't cache items for reference with null key. We don't want risk potential perf regression by 
+                // making those items repeatedly, so simply not returning anything from this assembly, until 
+                // we have a better understanding on this sceanrio.
+                // TODO: Add telemetry
+                return;
+            }
+
+            if (!(compilation.GetAssemblyOrModuleSymbol(peReference) is IAssemblySymbol assemblySymbol))
+            {
+                return;
+            }
+
+            var checksum = SymbolTreeInfo.GetMetadataChecksum(solution, peReference, cancellationToken);
+            GetAccessibleTopLevelTypesWorker(
+                key,
+                assemblySymbol,
+                checksum,
+                syntaxContext,
+                handleItem,
+                CacheService.PEItemsCache,
+                cancellationToken);
+
+            return;
+
+            static string GetReferenceKey(PortableExecutableReference reference)
+                => reference.FilePath ?? reference.Display;
+        }
+
+        private void GetAccessibleTopLevelTypesWorker<TKey>(
+            TKey key,
+            IAssemblySymbol assembly,
+            Checksum checksum,
+            SyntaxContext syntaxContext,
+            Action<CompletionItem, bool> handleItem,
+            IDictionary<TKey, ReferenceCacheEntry> cache,
+            CancellationToken cancellationToken)
+        {
+            var language = syntaxContext.SemanticModel.Language;
+
+            // Cache miss, create all requested items.
+            if (!cache.TryGetValue(key, out var cacheEntry) ||
+                cacheEntry.Checksum != checksum)
+            {
+                var builder = new ReferenceCacheEntry.Builder(checksum, language, GenericTypeSuffix);
+                GetCompletionItemsForTopLevelTypeDeclarations(assembly.GlobalNamespace, builder, cancellationToken);
+                cacheEntry = builder.ToReferenceCacheEntry();
+                cache[key] = cacheEntry;
+            }
+
+            foreach (var itemInfo in cacheEntry.GetItemsForContext(language, GenericTypeSuffix, syntaxContext.IsAttributeNameContext, IsCaseSensitive))
+            {
+                handleItem(itemInfo.Item, itemInfo.IsPublic);
+            }
+        }
+
+        private static void GetCompletionItemsForTopLevelTypeDeclarations(
+            INamespaceSymbol rootNamespaceSymbol,
+            ReferenceCacheEntry.Builder builder,
+            CancellationToken cancellationToken)
+        {
+            VisitNamespace(rootNamespaceSymbol, containingNamespace: null, builder, cancellationToken);
+            return;
+
+            static void VisitNamespace(
+                INamespaceSymbol symbol,
+                string containingNamespace,
+                ReferenceCacheEntry.Builder builder,
+                CancellationToken cancellationToken)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+                containingNamespace = ConcatNamespace(containingNamespace, symbol.Name);
+
+                foreach (var memberNamespace in symbol.GetNamespaceMembers())
+                {
+                    VisitNamespace(memberNamespace, containingNamespace, builder, cancellationToken);
+                }
+
+                var overloads = PooledDictionary<string, TypeOverloadInfo>.GetInstance();
+                var types = symbol.GetTypeMembers();
+
+                // Iterate over all top level internal and public types, keep track of "type overloads".
+                foreach (var type in types)
+                {
+                    // No need to check accessibility here, since top level types can only be internal or public.
+                    if (type.CanBeReferencedByName)
+                    {
+                        overloads.TryGetValue(type.Name, out var overloadInfo);
+                        overloads[type.Name] = overloadInfo.Aggregate(type);
+                    }
+                }
+
+                foreach (var pair in overloads)
+                {
+                    var overloadInfo = pair.Value;
+
+                    // Create CompletionItem for non-generic type overload, if exists.
+                    if (overloadInfo.NonGenericOverload != null)
+                    {
+                        builder.AddItem(
+                            overloadInfo.NonGenericOverload,
+                            containingNamespace,
+                            overloadInfo.NonGenericOverload.DeclaredAccessibility == Accessibility.Public);
+                    }
+
+                    // Create one CompletionItem for all generic type overloads, if there's any.
+                    // For simplicity, we always show the type symbol with lowest arity in CompletionDescription
+                    // and without displaying the total number of overloads.
+                    if (overloadInfo.BestGenericOverload != null)
+                    {
+                        // If any of the generic overloads is public, then the completion item is considered public.
+                        builder.AddItem(
+                            overloadInfo.BestGenericOverload,
+                            containingNamespace,
+                            overloadInfo.ContainsPublicGenericOverload);
+                    }
+                }
+
+                overloads.Free();
+            }
+        }
+
+        private static string ConcatNamespace(string containingNamespace, string name)
+        {
+            Debug.Assert(name != null);
+            if (string.IsNullOrEmpty(containingNamespace))
+            {
+                return name;
+            }
+
+            return containingNamespace + "." + name;
+        }
+
+        private readonly struct TypeOverloadInfo
+        {
+            public TypeOverloadInfo(INamedTypeSymbol nonGenericOverload, INamedTypeSymbol bestGenericOverload, bool containsPublicGenericOverload)
+            {
+                NonGenericOverload = nonGenericOverload;
+                BestGenericOverload = bestGenericOverload;
+                ContainsPublicGenericOverload = containsPublicGenericOverload;
+            }
+
+            public INamedTypeSymbol NonGenericOverload { get; }
+
+            // Generic with fewest type parameters is considered best symbol to show in description.
+            public INamedTypeSymbol BestGenericOverload { get; }
+
+            public bool ContainsPublicGenericOverload { get; }
+
+            public TypeOverloadInfo Aggregate(INamedTypeSymbol type)
+            {
+                if (type.Arity == 0)
+                {
+                    return new TypeOverloadInfo(nonGenericOverload: type, BestGenericOverload, ContainsPublicGenericOverload);
+                }
+
+                // We consider generic with fewer type parameters better symbol to show in description
+                var newBestGenericOverload = BestGenericOverload == null || type.Arity < BestGenericOverload.Arity
+                    ? type
+                    : BestGenericOverload;
+
+                var newContainsPublicGenericOverload = type.DeclaredAccessibility >= Accessibility.Public || ContainsPublicGenericOverload;
+
+                return new TypeOverloadInfo(NonGenericOverload, newBestGenericOverload, newContainsPublicGenericOverload);
+            }
+        }
+
+        private readonly struct ReferenceCacheEntry
+        {
+            public class Builder
+            {
+                private readonly string _language;
+                private readonly string _genericTypeSuffix;
+                private readonly Checksum _checksum;
+
+                public Builder(Checksum checksum, string language, string genericTypeSuffix)
+                {
+                    _checksum = checksum;
+                    _language = language;
+                    _genericTypeSuffix = genericTypeSuffix;
+
+                    _itemsBuilder = ArrayBuilder<TypeImportCompletionItemInfo>.GetInstance();
+                }
+
+                private ArrayBuilder<TypeImportCompletionItemInfo> _itemsBuilder;
+
+                public ReferenceCacheEntry ToReferenceCacheEntry()
+                {
+                    return new ReferenceCacheEntry(
+                        _checksum,
+                        _language,
+                        _itemsBuilder.ToImmutableAndFree());
+                }
+
+                public void AddItem(INamedTypeSymbol symbol, string containingNamespace, bool isPublic)
+                {
+                    var isGeneric = symbol.Arity > 0;
+
+                    // Need to determine if a type is an attribute up front since we want to filter out 
+                    // non-attribute types when in attribute context. We can't do this lazily since we don't hold 
+                    // on to symbols. However, the cost of calling `IsAttribute` on every top-level type symbols 
+                    // is prohibitively high, so we opt for the heuristic that would do the simple textual "Attribute" 
+                    // suffix check first, then the more expensive symbolic check. As a result, all unimported
+                    // attribute types that don't have "Attribute" suffix would be filtered out when in attribute context.
+                    var isAttribute = symbol.Name.HasAttributeSuffix(isCaseSensitive: false) && symbol.IsAttribute();
+
+                    var item = TypeImportCompletionItem.Create(symbol, containingNamespace, _genericTypeSuffix);
+                    item.IsCached = true;
+
+                    _itemsBuilder.Add(new TypeImportCompletionItemInfo(item, isPublic, isGeneric, isAttribute));
+                    return;
+                }
+            }
+
+            private ReferenceCacheEntry(
+                Checksum checksum,
+                string language,
+                ImmutableArray<TypeImportCompletionItemInfo> items)
+            {
+                Checksum = checksum;
+                Language = language;
+
+                ItemInfos = items;
+            }
+
+            public string Language { get; }
+
+            public Checksum Checksum { get; }
+
+            private ImmutableArray<TypeImportCompletionItemInfo> ItemInfos { get; }
+
+            public ImmutableArray<TypeImportCompletionItemInfo> GetItemsForContext(string language, string genericTypeSuffix, bool isAttributeContext, bool isCaseSensitive)
+            {
+                var isSameLanguage = Language == language;
+                if (isSameLanguage && !isAttributeContext)
+                {
+                    return ItemInfos;
+                }
+
+                var builder = ArrayBuilder<TypeImportCompletionItemInfo>.GetInstance();
+                foreach (var info in ItemInfos)
+                {
+                    CompletionItem item = info.Item;
+                    if (isAttributeContext)
+                    {
+                        if (!info.IsAttribute)
+                        {
+                            continue;
+                        }
+
+                        item = GetAppropriateAttributeItem(info.Item, isCaseSensitive);
+                    }
+
+                    if (!isSameLanguage && info.IsGeneric)
+                    {
+                        // We don't want to cache this item.
+                        item = TypeImportCompletionItem.CreateItemWithGenericDisplaySuffix(item, genericTypeSuffix);
+                    }
+
+                    builder.Add(info.WithItem(item));
+                }
+
+                return builder.ToImmutableAndFree();
+
+                static CompletionItem GetAppropriateAttributeItem(CompletionItem attributeItem, bool isCaseSensitive)
+                {
+                    if (attributeItem.DisplayText.TryGetWithoutAttributeSuffix(isCaseSensitive: isCaseSensitive, out var attributeNameWithoutSuffix))
+                    {
+                        // We don't want to cache this item.
+                        return TypeImportCompletionItem.CreateAttributeItemWithoutSuffix(attributeItem, attributeNameWithoutSuffix);
+                    }
+
+                    return attributeItem;
+                }
+            }
+        }
+
+        private readonly struct TypeImportCompletionItemInfo
+        {
+            private readonly ItemPropertyKind _properties;
+
+            public TypeImportCompletionItemInfo(CompletionItem item, bool isPublic, bool isGeneric, bool isAttribute)
+            {
+                Item = item;
+                _properties = (isPublic ? ItemPropertyKind.IsPublic : 0)
+                            | (isGeneric ? ItemPropertyKind.IsGeneric : 0)
+                            | (isAttribute ? ItemPropertyKind.IsAttribute : 0);
+            }
+
+            public CompletionItem Item { get; }
+
+            public bool IsPublic
+                => (_properties & ItemPropertyKind.IsPublic) != 0;
+
+            public bool IsGeneric
+                => (_properties & ItemPropertyKind.IsGeneric) != 0;
+
+            public bool IsAttribute
+                => (_properties & ItemPropertyKind.IsAttribute) != 0;
+
+            public TypeImportCompletionItemInfo WithItem(CompletionItem item)
+            {
+                return new TypeImportCompletionItemInfo(item, IsPublic, IsGeneric, IsAttribute);
+            }
+
+            [Flags]
+            private enum ItemPropertyKind : byte
+            {
+                IsPublic = 0x1,
+                IsGeneric = 0x2,
+                IsAttribute = 0x4,
+            }
+        }
+    }
+}

src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/AbstractTypeImportCompletionService_CacheService.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.
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+
+namespace Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion
+{
+    internal partial class AbstractTypeImportCompletionService
+    {
+        private interface ITypeImportCompletionCacheService : IWorkspaceService
+        {
+            // PE references are keyed on assembly path.
+            IDictionary<string, ReferenceCacheEntry> PEItemsCache { get; }
+
+            IDictionary<ProjectId, ReferenceCacheEntry> ProjectItemsCache { get; }
+        }
+
+        [ExportWorkspaceServiceFactory(typeof(ITypeImportCompletionCacheService), ServiceLayer.Editor), Shared]
+        private class TypeImportCompletionCacheServiceFactory : IWorkspaceServiceFactory
+        {
+            private readonly ConcurrentDictionary<string, ReferenceCacheEntry> _peItemsCache
+                = new ConcurrentDictionary<string, ReferenceCacheEntry>();
+
+            private readonly ConcurrentDictionary<ProjectId, ReferenceCacheEntry> _projectItemsCache
+                = new ConcurrentDictionary<ProjectId, ReferenceCacheEntry>();
+
+            [ImportingConstructor]
+            public TypeImportCompletionCacheServiceFactory()
+            {
+            }
+
+            public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
+            {
+                var workspace = workspaceServices.Workspace;
+                if (workspace.Kind == WorkspaceKind.Host)
+                {
+                    var cacheService = workspaceServices.GetService<IWorkspaceCacheService>();
+                    if (cacheService != null)
+                    {
+                        cacheService.CacheFlushRequested += OnCacheFlushRequested;
+                    }
+                }
+
+                return new TypeImportCompletionCacheService(_peItemsCache, _projectItemsCache);
+            }
+
+            private void OnCacheFlushRequested(object sender, EventArgs e)
+            {
+                _peItemsCache.Clear();
+                _projectItemsCache.Clear();
+            }
+
+            private class TypeImportCompletionCacheService : ITypeImportCompletionCacheService
+            {
+                public IDictionary<string, ReferenceCacheEntry> PEItemsCache { get; }
+
+                public IDictionary<ProjectId, ReferenceCacheEntry> ProjectItemsCache { get; }
+
+                public TypeImportCompletionCacheService(
+                    ConcurrentDictionary<string, ReferenceCacheEntry> peCache,
+                    ConcurrentDictionary<ProjectId, ReferenceCacheEntry> projectCache)
+                {
+                    PEItemsCache = peCache;
+                    ProjectItemsCache = projectCache;
+                }
+            }
+        }
+
+    }
+}

src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/ITypeImportCompletionService.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.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Shared.Extensions.ContextQuery;
+
+namespace Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion
+{
+    internal interface ITypeImportCompletionService : ILanguageService
+    {
+        /// <summary>
+        /// Get all the top level types from given project. This method is intended to be used for 
+        /// getting types from source only, so the project must support compilation. 
+        /// For getting types from PE, use <see cref="GetTopLevelTypesFromPEReference"/>.
+        /// </summary>
+        Task GetTopLevelTypesAsync(
+            Project project,
+            SyntaxContext syntaxContext,
+            Action<CompletionItem, bool> handleItem,
+            CancellationToken cancellationToken);
+
+        void GetTopLevelTypesFromPEReference(
+            Solution solution,
+            Compilation compilation,
+            PortableExecutableReference peReference,
+            SyntaxContext syntaxContext,
+            Action<CompletionItem, bool> handleItem,
+            CancellationToken cancellationToken);
+    }
+}

src/Features/Core/Portable/Completion/Providers/TypeImportCompletionItem.cs → src/Features/Core/Portable/Completion/Providers/ImportCompletionProvider/TypeImportCompletionItem.cs

@@ -16,8 +16,9 @@ internal static class TypeImportCompletionItem
         private static readonly string[] s_aritySuffixesOneToNine = { "`1", "`2", "`3", "`4", "`5", "`6", "`7", "`8", "`9" };
 
         private const string TypeAritySuffixName = nameof(TypeAritySuffixName);
+        private const string AttributeFullName = nameof(AttributeFullName);
 
-        public static CompletionItem Create(INamedTypeSymbol typeSymbol, string containingNamespace)
+        public static CompletionItem Create(INamedTypeSymbol typeSymbol, string containingNamespace, string genericTypeSuffix)
         {
             PooledDictionary<string, string> propertyBuilder = null;
 
@@ -27,17 +28,13 @@ public static CompletionItem Create(INamedTypeSymbol typeSymbol, string containi
                 propertyBuilder.Add(TypeAritySuffixName, GetAritySuffix(typeSymbol.Arity));
             }
 
-            // Hack: add tildes (ASCII: 126) to name and namespace as sort text:
+            // Add tildes (ASCII: 126) to name and namespace as sort text:
             // 1. '~' before type name makes import items show after in-scope items
             // 2. ' ' before namespace makes types with identical type name but from different namespace all show up in the list,
             //    it also makes sure type with shorter name shows first, e.g. 'SomeType` before 'SomeTypeWithLongerName'.  
             var sortTextBuilder = PooledStringBuilder.GetInstance();
             sortTextBuilder.Builder.AppendFormat(SortTextFormat, typeSymbol.Name, containingNamespace);
 
-            // TODO: 
-            // 1. Suffix should be language specific, i.e. `(Of ...)` if triggered from VB.
-            // 2. Sort the import items to be after in-scope symbols in a less hacky way.
-            // 3. Editor support for resolving item text conflicts?
             return CompletionItem.Create(
                  displayText: typeSymbol.Name,
                  filterText: typeSymbol.Name,
@@ -46,10 +43,37 @@ public static CompletionItem Create(INamedTypeSymbol typeSymbol, string containi
                  tags: GlyphTags.GetTags(typeSymbol.GetGlyph()),
                  rules: CompletionItemRules.Default,
                  displayTextPrefix: null,
-                 displayTextSuffix: typeSymbol.Arity == 0 ? string.Empty : "<>",
+                 displayTextSuffix: typeSymbol.Arity == 0 ? string.Empty : genericTypeSuffix,
                  inlineDescription: containingNamespace);
         }
 
+        public static CompletionItem CreateAttributeItemWithoutSuffix(CompletionItem attributeItem, string attributeNameWithoutSuffix)
+        {
+            Debug.Assert(!attributeItem.Properties.ContainsKey(AttributeFullName));
+
+            // Remember the full type name so we can get the symbol when description is displayed.
+            var newProperties = attributeItem.Properties.Add(AttributeFullName, attributeItem.DisplayText);
+
+            var sortTextBuilder = PooledStringBuilder.GetInstance();
+            sortTextBuilder.Builder.AppendFormat(SortTextFormat, attributeNameWithoutSuffix, attributeItem.InlineDescription);
+
+            return CompletionItem.Create(
+                 displayText: attributeNameWithoutSuffix,
+                 filterText: attributeNameWithoutSuffix,
+                 sortText: sortTextBuilder.ToStringAndFree(),
+                 properties: newProperties,
+                 tags: attributeItem.Tags,
+                 rules: attributeItem.Rules,
+                 displayTextPrefix: attributeItem.DisplayTextPrefix,
+                 displayTextSuffix: attributeItem.DisplayTextSuffix,
+                 inlineDescription: attributeItem.InlineDescription);
+        }
+
+        public static CompletionItem CreateItemWithGenericDisplaySuffix(CompletionItem item, string genericTypeSuffix)
+        {
+            return item.WithDisplayTextSuffix(genericTypeSuffix);
+        }
+
         public static string GetContainingNamespace(CompletionItem item)
             => item.InlineDescription;
 
@@ -95,7 +119,8 @@ private static string GetFullyQualifiedName(string namespaceName, string typeNam
         private static string GetMetadataName(CompletionItem item)
         {
             var containingNamespace = GetContainingNamespace(item);
-            var fullyQualifiedName = GetFullyQualifiedName(containingNamespace, item.DisplayText);
+            var typeName = item.Properties.TryGetValue(AttributeFullName, out var attributeFullName) ? attributeFullName : item.DisplayText;
+            var fullyQualifiedName = GetFullyQualifiedName(containingNamespace, typeName);
             if (item.Properties.TryGetValue(TypeAritySuffixName, out var aritySuffix))
             {
                 return fullyQualifiedName + aritySuffix;

src/Features/Core/Portable/Completion/Providers/TypeImportCompletionService.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.
-
-using System;
-using System.Collections.Concurrent;
-using System.Collections.Immutable;
-using System.Composition;
-using System.Diagnostics;
-using System.Threading;
-using System.Threading.Tasks;
-using Microsoft.CodeAnalysis.FindSymbols;
-using Microsoft.CodeAnalysis.Host;
-using Microsoft.CodeAnalysis.Host.Mef;
-using Microsoft.CodeAnalysis.PooledObjects;
-
-namespace Microsoft.CodeAnalysis.Completion.Providers
-{
-    internal interface ITypeImportCompletionService : IWorkspaceService
-    {
-        /// <summary>
-        /// Get all the top level types from given project. This method is intended to be used for 
-        /// getting types from source only, so the project must support compilation. 
-        /// For getting types from PE, use <see cref="GetTopLevelTypesFromPEReference"/>.
-        /// </summary>
-        Task GetTopLevelTypesAsync(
-            Project project,
-            Action<TypeImportCompletionItemInfo> handleItem,
-            CancellationToken cancellationToken);
-
-        void GetTopLevelTypesFromPEReference(
-            Solution solution,
-            Compilation compilation,
-            PortableExecutableReference peReference,
-            Action<TypeImportCompletionItemInfo> handleItem,
-            CancellationToken cancellationToken);
-    }
-
-    internal readonly struct TypeImportCompletionItemInfo
-    {
-        public TypeImportCompletionItemInfo(CompletionItem item, bool isPublic)
-        {
-            Item = item;
-            IsPublic = isPublic;
-        }
-
-        public CompletionItem Item { get; }
-
-        public bool IsPublic { get; }
-    }
-
-    [ExportWorkspaceServiceFactory(typeof(ITypeImportCompletionService), ServiceLayer.Editor), Shared]
-    internal sealed class TypeImportCompletionService : IWorkspaceServiceFactory
-    {
-        private readonly ConcurrentDictionary<string, ReferenceCacheEntry> _peItemsCache
-            = new ConcurrentDictionary<string, ReferenceCacheEntry>();
-
-        private readonly ConcurrentDictionary<ProjectId, ReferenceCacheEntry> _projectItemsCache
-            = new ConcurrentDictionary<ProjectId, ReferenceCacheEntry>();
-
-        [ImportingConstructor]
-        public TypeImportCompletionService()
-        {
-        }
-
-        public IWorkspaceService CreateService(HostWorkspaceServices workspaceServices)
-        {
-            var workspace = workspaceServices.Workspace;
-            if (workspace.Kind == WorkspaceKind.Host)
-            {
-                var cacheService = workspaceServices.GetService<IWorkspaceCacheService>();
-                if (cacheService != null)
-                {
-                    cacheService.CacheFlushRequested += OnCacheFlushRequested;
-                }
-            }
-
-            return new Service(workspace, _peItemsCache, _projectItemsCache);
-        }
-
-        private void OnCacheFlushRequested(object sender, EventArgs e)
-        {
-            _peItemsCache.Clear();
-            _projectItemsCache.Clear();
-        }
-
-        private class Service : ITypeImportCompletionService
-        {
-            // PE references are keyed on assembly path.
-            private readonly ConcurrentDictionary<string, ReferenceCacheEntry> _peItemsCache;
-            private readonly ConcurrentDictionary<ProjectId, ReferenceCacheEntry> _projectItemsCache;
-
-            public Service(
-                Workspace workspace,
-                ConcurrentDictionary<string, ReferenceCacheEntry> peReferenceCache,
-                ConcurrentDictionary<ProjectId, ReferenceCacheEntry> projectReferenceCache)
-            {
-                _peItemsCache = peReferenceCache;
-                _projectItemsCache = projectReferenceCache;
-
-                workspace.WorkspaceChanged += OnWorkspaceChanged;
-            }
-
-            public void OnWorkspaceChanged(object sender, WorkspaceChangeEventArgs e)
-            {
-                switch (e.Kind)
-                {
-                    case WorkspaceChangeKind.SolutionCleared:
-                    case WorkspaceChangeKind.SolutionReloaded:
-                    case WorkspaceChangeKind.SolutionRemoved:
-                        _peItemsCache.Clear();
-                        _projectItemsCache.Clear();
-                        break;
-                    case WorkspaceChangeKind.ProjectRemoved:
-                    case WorkspaceChangeKind.ProjectReloaded:
-                        _projectItemsCache.TryRemove(e.ProjectId, out _);
-                        break;
-                }
-            }
-
-            public async Task GetTopLevelTypesAsync(
-                Project project,
-                Action<TypeImportCompletionItemInfo> handleItem,
-                CancellationToken cancellationToken)
-            {
-                if (!project.SupportsCompilation)
-                {
-                    throw new ArgumentException(nameof(project));
-                }
-
-                var compilation = await project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
-
-                // Since we only need top level types from source, therefore we only care if source symbol checksum changes.
-                var checksum = await SymbolTreeInfo.GetSourceSymbolsChecksumAsync(project, cancellationToken).ConfigureAwait(false);
-
-                GetAccessibleTopLevelTypesWorker(
-                    project.Id,
-                    compilation.Assembly,
-                    checksum,
-                    handleItem,
-                    _projectItemsCache,
-                    cancellationToken);
-            }
-
-            public void GetTopLevelTypesFromPEReference(
-                Solution solution,
-                Compilation compilation,
-                PortableExecutableReference peReference,
-                Action<TypeImportCompletionItemInfo> handleItem,
-                CancellationToken cancellationToken)
-            {
-                var key = GetReferenceKey(peReference);
-                if (key == null)
-                {
-                    // Can't cache items for reference with null key. We don't want risk potential perf regression by 
-                    // making those items repeatedly, so simply not returning anything from this assembly, until 
-                    // we have a better understanding on this sceanrio.
-                    // TODO: Add telemetry
-                    return;
-                }
-
-                if (!(compilation.GetAssemblyOrModuleSymbol(peReference) is IAssemblySymbol assemblySymbol))
-                {
-                    return;
-                }
-
-                var checksum = SymbolTreeInfo.GetMetadataChecksum(solution, peReference, cancellationToken);
-                GetAccessibleTopLevelTypesWorker(
-                    key,
-                    assemblySymbol,
-                    checksum,
-                    handleItem,
-                    _peItemsCache,
-                    cancellationToken);
-
-                return;
-
-                static string GetReferenceKey(PortableExecutableReference reference)
-                    => reference.FilePath ?? reference.Display;
-            }
-
-            private static void GetAccessibleTopLevelTypesWorker<TKey>(
-                TKey key,
-                IAssemblySymbol assembly,
-                Checksum checksum,
-                Action<TypeImportCompletionItemInfo> handleItem,
-                ConcurrentDictionary<TKey, ReferenceCacheEntry> cache,
-                CancellationToken cancellationToken)
-            {
-                // Cache miss, create all requested items.
-                if (!cache.TryGetValue(key, out var cacheEntry) ||
-                    cacheEntry.Checksum != checksum)
-                {
-                    var items = GetCompletionItemsForTopLevelTypeDeclarations(assembly.GlobalNamespace, cancellationToken);
-                    cacheEntry = new ReferenceCacheEntry(checksum, items);
-                    cache[key] = cacheEntry;
-                }
-
-                foreach (var item in cacheEntry.CachedItems)
-                {
-                    handleItem(item);
-                }
-            }
-
-            private static ImmutableArray<TypeImportCompletionItemInfo> GetCompletionItemsForTopLevelTypeDeclarations(
-                INamespaceSymbol rootNamespaceSymbol,
-                CancellationToken cancellationToken)
-            {
-                var builder = ArrayBuilder<TypeImportCompletionItemInfo>.GetInstance();
-                VisitNamespace(rootNamespaceSymbol, containingNamespace: null, builder, cancellationToken);
-                return builder.ToImmutableAndFree();
-
-                static void VisitNamespace(
-                    INamespaceSymbol symbol,
-                    string containingNamespace,
-                    ArrayBuilder<TypeImportCompletionItemInfo> builder,
-                    CancellationToken cancellationToken)
-                {
-                    cancellationToken.ThrowIfCancellationRequested();
-                    containingNamespace = ConcatNamespace(containingNamespace, symbol.Name);
-
-                    foreach (var memberNamespace in symbol.GetNamespaceMembers())
-                    {
-                        VisitNamespace(memberNamespace, containingNamespace, builder, cancellationToken);
-                    }
-
-                    var overloads = PooledDictionary<string, TypeOverloadInfo>.GetInstance();
-                    var types = symbol.GetTypeMembers();
-
-                    // Iterate over all top level internal and public types, keep track of "type overloads".
-                    foreach (var type in types)
-                    {
-                        // No need to check accessibility here, since top level types can only be internal or public.
-                        if (type.CanBeReferencedByName)
-                        {
-                            overloads.TryGetValue(type.Name, out var overloadInfo);
-                            overloads[type.Name] = overloadInfo.Aggregate(type);
-                        }
-                    }
-
-                    foreach (var pair in overloads)
-                    {
-                        var overloadInfo = pair.Value;
-
-                        // Create CompletionItem for non-generic type overload, if exists.
-                        if (overloadInfo.NonGenericOverload != null)
-                        {
-                            var item = TypeImportCompletionItem.Create(overloadInfo.NonGenericOverload, containingNamespace);
-                            var isPublic = overloadInfo.NonGenericOverload.DeclaredAccessibility == Accessibility.Public;
-                            item.IsCached = true;
-                            builder.Add(new TypeImportCompletionItemInfo(item, isPublic));
-                        }
-
-                        // Create one CompletionItem for all generic type overloads, if there's any.
-                        // For simplicity, we always show the type symbol with lowest arity in CompletionDescription
-                        // and without displaying the total number of overloads.
-                        if (overloadInfo.BestGenericOverload != null)
-                        {
-                            // If any of the generic overloads is public, then the completion item is considered public.
-                            var item = TypeImportCompletionItem.Create(overloadInfo.BestGenericOverload, containingNamespace);
-                            var isPublic = overloadInfo.ContainsPublicGenericOverload;
-                            item.IsCached = true;
-                            builder.Add(new TypeImportCompletionItemInfo(item, isPublic));
-                        }
-                    }
-
-                    overloads.Free();
-                }
-            }
-        }
-
-        private static string ConcatNamespace(string containingNamespace, string name)
-        {
-            Debug.Assert(name != null);
-            if (string.IsNullOrEmpty(containingNamespace))
-            {
-                return name;
-            }
-
-            return containingNamespace + "." + name;
-        }
-
-        private readonly struct TypeOverloadInfo
-        {
-            public TypeOverloadInfo(INamedTypeSymbol nonGenericOverload, INamedTypeSymbol bestGenericOverload, bool containsPublicGenericOverload)
-            {
-                NonGenericOverload = nonGenericOverload;
-                BestGenericOverload = bestGenericOverload;
-                ContainsPublicGenericOverload = containsPublicGenericOverload;
-            }
-
-            public INamedTypeSymbol NonGenericOverload { get; }
-
-            // Generic with fewest type parameters is considered best symbol to show in description.
-            public INamedTypeSymbol BestGenericOverload { get; }
-
-            public bool ContainsPublicGenericOverload { get; }
-
-            public TypeOverloadInfo Aggregate(INamedTypeSymbol type)
-            {
-                if (type.Arity == 0)
-                {
-                    return new TypeOverloadInfo(nonGenericOverload: type, BestGenericOverload, ContainsPublicGenericOverload);
-                }
-
-                // We consider generic with fewer type parameters better symbol to show in description
-                var newBestGenericOverload = BestGenericOverload == null || type.Arity < BestGenericOverload.Arity
-                    ? type
-                    : BestGenericOverload;
-
-                var newContainsPublicGenericOverload = type.DeclaredAccessibility >= Accessibility.Public || ContainsPublicGenericOverload;
-
-                return new TypeOverloadInfo(NonGenericOverload, newBestGenericOverload, newContainsPublicGenericOverload);
-            }
-        }
-
-        private readonly struct ReferenceCacheEntry
-        {
-            public ReferenceCacheEntry(
-                Checksum checksum,
-                ImmutableArray<TypeImportCompletionItemInfo> cachedItems)
-            {
-                Checksum = checksum;
-                CachedItems = cachedItems;
-            }
-
-            public Checksum Checksum { get; }
-
-            public ImmutableArray<TypeImportCompletionItemInfo> CachedItems { get; }
-        }
-    }
-}

src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImportCompletionProvider/BasicTypeImportCompletionServiceFactory.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.Composition
+Imports Microsoft.CodeAnalysis.Completion.Providers.ImportCompletion
+Imports Microsoft.CodeAnalysis.Host
+Imports Microsoft.CodeAnalysis.Host.Mef
+
+Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
+    <ExportLanguageServiceFactory(GetType(ITypeImportCompletionService), LanguageNames.VisualBasic), [Shared]>
+    Friend NotInheritable Class BasicTypeImportCompletionServiceFactory
+        Implements ILanguageServiceFactory
+
+        <ImportingConstructor>
+        Public Sub New()
+        End Sub
+
+        Public Function CreateLanguageService(languageServices As HostLanguageServices) As ILanguageService Implements ILanguageServiceFactory.CreateLanguageService
+            Return New BasicTypeImportCompletionService(languageServices.WorkspaceServices.Workspace)
+        End Function
+
+        Private Class BasicTypeImportCompletionService
+            Inherits AbstractTypeImportCompletionService
+
+            Public Sub New(workspace As Workspace)
+                MyBase.New(workspace)
+            End Sub
+
+            Protected Overrides ReadOnly Property GenericTypeSuffix As String
+                Get
+                    Return "(Of ...)"
+                End Get
+            End Property
+
+            Protected Overrides ReadOnly Property IsCaseSensitive As Boolean
+                Get
+                    Return False
+                End Get
+            End Property
+        End Class
+    End Class
+End Namespace

src/Workspaces/Core/Portable/Extensions/OperationExtensions.cs

@@ -3,7 +3,6 @@
 using System;
 using System.Collections.Immutable;
 using System.Diagnostics;
-using System.Linq;
 using Microsoft.CodeAnalysis.FlowAnalysis;
 using Microsoft.CodeAnalysis.Operations;
 
@@ -61,7 +60,7 @@ public static ValueUsageInfo GetValueUsageInfo(this IOperation operation)
                         //
                         return ValueUsageInfo.Write;
 
-                    case IOperation iop when iop.GetType().GetInterfaces().Any(i => i.Name == "IRecursivePatternOperation"):
+                    case IRecursivePatternOperation _:
                         // A declaration pattern within a recursive pattern is a
                         // write for the declared local.
                         // For example, 'x' is defined and assigned the value from 'obj' below: