Merge pull request #18616 from rchande/fixcrash

Fix crash in implements clause completion

src/EditorFeatures/VisualBasicTest/Completion/CompletionProviders/ImplementsClauseCompletionProviderTests.vb

@@ -721,5 +721,23 @@ End Class</text>.Value
 
             Await VerifyItemExistsAsync(text, "Quux")
         End Function
+
+        <WorkItem(402811, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=402811")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function DoNotCrashWithOnlyDotTyped() As Task
+            Dim text = <text>Interface I
+    Sub Foo()
+    Sub Quux()
+End Interface
+
+Class B
+    Implements I
+
+    Public Sub Foo Implements .$$
+
+   </text>.Value
+
+            Await VerifyNoItemsExistAsync(text)
+        End Function
     End Class
 End Namespace
\ No newline at end of file

src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb

@@ -139,7 +139,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
             End If
 
             If container Is Nothing Then
-                Return Nothing
+                Return ImmutableArray(Of ISymbol).Empty
             End If
             Dim symbols = semanticModel.LookupSymbols(position, container)