adding test

src/EditorFeatures/Test2/EditorServicesTest2.vbproj

@@ -167,6 +167,7 @@
     <Compile Include="Diagnostics\UseAutoProperty\UseAutoPropertyTests.vb" />
     <Compile Include="Expansion\LambdaParameterExpansionTests.vb" />
     <Compile Include="GoToImplementation\GoToImplementationTests.vb" />
+    <Compile Include="IntelliSense\CompletionServiceTests.vb" />
     <Compile Include="InteractivePaste\InteractivePasteCommandHandlerTests.vb" />
     <Compile Include="IntelliSense\CompletionRulesTests.vb" />
     <Compile Include="LanguageServices\SyntaxFactsServiceTests.vb" />

src/EditorFeatures/Test2/IntelliSense/CompletionServiceTests.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.Globalization
+Imports System.Threading.Tasks
+Imports Microsoft.CodeAnalysis.Completion
+Imports Microsoft.CodeAnalysis.CSharp.Completion
+Imports Microsoft.CodeAnalysis.CSharp.Completion.Providers
+Imports Microsoft.CodeAnalysis.Editor.UnitTests.Workspaces
+Imports Microsoft.CodeAnalysis.Options
+Imports Microsoft.CodeAnalysis.Text
+
+Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
+    Public Class CompletionServiceTests
+        <Fact>
+        Public Async Function TestComplemtionDoesNotCrashWhenSyntaxTreeNotPresent() As Task
+            Dim workspaceDefinition =
+            <Workspace>
+                <Project Language="NoCompilation" AssemblyName="TestAssembly" CommonReferencesPortable="true">
+                    <Document>
+                        var x = {}; // e.g., TypeScript code or anything else that doesn't support compilations
+                    </Document>
+                </Project>
+            </Workspace>
+            Using workspace = Await TestWorkspace.CreateAsync(workspaceDefinition)
+                Dim document = workspace.CurrentSolution.Projects.First.Documents.First
+                Dim completionService As AbstractCompletionService = New CSharpCompletionService()
+                Dim list = Await completionService.GetCompletionListAsync(
+                    document:=document,
+                    position:=0,
+                    triggerInfo:=CompletionTriggerInfo.CreateInvokeCompletionTriggerInfo(),
+                    options:=Nothing,
+                    providers:={New TestCompletionProvider()},
+                    cancellationToken:=Nothing)
+                Assert.Null(list)
+            End Using
+        End Function
+
+        Private Class TestCompletionProvider
+            Inherits CompletionListProvider
+            Public Sub New()
+            End Sub
+
+            Public Overrides Function IsTriggerCharacter(text As SourceText, characterPosition As Int32, options As OptionSet) As [Boolean]
+                Return True
+            End Function
+
+            Public Overrides Function ProduceCompletionListAsync(context As CompletionListContext) As Task
+                Return Task.CompletedTask
+            End Function
+        End Class
+    End Class
+End Namespace
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