diff --git a/src/EditorFeatures/CSharpTest/NavigateTo/NavigateToTests.cs b/src/EditorFeatures/CSharpTest/NavigateTo/NavigateToTests.cs
index 77a47999daed8135373025e8d2e5ed064236fcdd..017725705a12585a74add6e5ed2bd89980853fb9 100644
--- a/src/EditorFeatures/CSharpTest/NavigateTo/NavigateToTests.cs
+++ b/src/EditorFeatures/CSharpTest/NavigateTo/NavigateToTests.cs
@@ -1095,5 +1095,23 @@ public void ToError()
                 VerifyNavigateToResultItem(item, "ToError", "ToError()", MatchKind.Regular, NavigateToItemKind.Method);
             });
         }
+
+        [WorkItem(18843, "https://github.com/dotnet/roslyn/issues/18843")]
+        [WpfFact, Trait(Traits.Feature, Traits.Features.NavigateTo)]
+        public async Task Test__arglist()
+        {
+            await TestAsync(
+@"class C
+{
+    public void ToError(__arglist)
+    {
+    }
+}", async w =>
+{
+    SetupVerifiableGlyph(StandardGlyphGroup.GlyphGroupMethod, StandardGlyphItem.GlyphItemPublic);
+    var item = (await _aggregator.GetItemsAsync("ToError")).Single();
+    VerifyNavigateToResultItem(item, "ToError", "[|ToError|](__arglist)", MatchKind.Exact, NavigateToItemKind.Method);
+});
+        }
     }
 }
\ No newline at end of file
diff --git a/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs b/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
index 9f5f53452292e7409b19685b9c5023c31d6fe2cc..2c65683e1aea07bf5e885e6a048592e0018d1847 100644
--- a/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
+++ b/src/EditorFeatures/Core/Implementation/Suggestions/SuggestedActionsSource.cs
@@ -113,7 +113,7 @@ public bool TryGetTelemetryId(out Guid telemetryId)
 
                 using (Logger.LogBlock(FunctionId.SuggestedActions_GetSuggestedActions, cancellationToken))
                 {
-                    var document = GetMatchingDocumentAsync(range.Snapshot, cancellationToken).WaitAndGetResult(cancellationToken);
+                    var document = range.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
                     if (document == null)
                     {
                         // this is here to fail test and see why it is failed.
@@ -288,7 +288,7 @@ private bool IsApplicable(CodeAction action, Workspace workspace)
                 if (!action.PerformFinalApplicabilityCheck)
                 {
                     // If we don't even need to perform the final applicability check,
-                    // then the code actoin is applicable.
+                    // then the code action is applicable.
                     return true;
                 }
 
@@ -588,7 +588,10 @@ private static SuggestedActionSetPriority GetSuggestedActionSetPriority(CodeActi
                     applicableSpan);
             }
 
-            public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet requestedActionCategories, SnapshotSpan range, CancellationToken cancellationToken)
+            public async Task<bool> HasSuggestedActionsAsync(
+                ISuggestedActionCategorySet requestedActionCategories,
+                SnapshotSpan range,
+                CancellationToken cancellationToken)
             {
                 // Explicitly hold onto below fields in locals and use these locals throughout this code path to avoid crashes
                 // if these fields happen to be cleared by Dispose() below. This is required since this code path involves
@@ -604,7 +607,7 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
 
                 using (var asyncToken = provider.OperationListener.BeginAsyncOperation("HasSuggestedActionsAsync"))
                 {
-                    var document = await GetMatchingDocumentAsync(range.Snapshot, cancellationToken).ConfigureAwait(false);
+                    var document = range.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
                     if (document == null)
                     {
                         // this is here to fail test and see why it is failed.
@@ -722,44 +725,6 @@ public async Task<bool> HasSuggestedActionsAsync(ISuggestedActionCategorySet req
                 return translatedSpan.Span.ToTextSpan();
             }
 
-            private static async Task<Document> GetMatchingDocumentAsync(ITextSnapshot givenSnapshot, CancellationToken cancellationToken)
-            {
-                var buffer = givenSnapshot.TextBuffer;
-                if (buffer == null)
-                {
-                    return null;
-                }
-
-                var workspace = buffer.GetWorkspace();
-                if (workspace == null)
-                {
-                    return null;
-                }
-
-                var documentId = workspace.GetDocumentIdInCurrentContext(buffer.AsTextContainer());
-                if (documentId == null)
-                {
-                    return null;
-                }
-
-                var document = workspace.CurrentSolution.GetDocument(documentId);
-                if (document == null)
-                {
-                    return null;
-                }
-
-                var sourceText = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
-                cancellationToken.ThrowIfCancellationRequested();
-
-                var snapshot = sourceText.FindCorrespondingEditorTextSnapshot();
-                if (snapshot == null || snapshot.Version.ReiteratedVersionNumber != givenSnapshot.Version.ReiteratedVersionNumber)
-                {
-                    return null;
-                }
-
-                return document;
-            }
-
             private void OnTextViewClosed(object sender, EventArgs e)
             {
                 Dispose();
diff --git a/src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs b/src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs
index 077229fba0fa0afe494b88fec70684ea9a846426..4c9b26d2b7c669dab00634219abb1e0a476088a1 100644
--- a/src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs
+++ b/src/Workspaces/CSharp/Portable/LanguageServices/CSharpSyntaxFactsService.cs
@@ -1014,7 +1014,14 @@ private void AppendParameters(SeparatedSyntaxList<ParameterSyntax> parameters, S
                     builder.Append(' ');
                 }
 
-                AppendTokens(parameter.Type, builder);
+                if (parameter.Type != null)
+                {
+                    AppendTokens(parameter.Type, builder);
+                }
+                else
+                {
+                    builder.Append(parameter.Identifier.Text);
+                }
 
                 first = false;
             }