Merge pull request #11465 from rchande/fixEnumCompletionWatson

Fix an IndexOutOfRangeException in EnumCompletion

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

@@ -460,6 +460,14 @@ End Class
             Await VerifyProviderCommitAsync(markup, "E.A", expected, ","c, textTypedSoFar:="")
         End Function
 
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        <WorkItem(201807, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=201807&triage=true&_a=edit")>
+        Public Async Function TestDoNotCrashAtPosition1AfterEquals() As Task
+            Dim markup = <Text><![CDATA[=$$     
+]]></Text>.Value
+            Await VerifyNoItemsExistAsync(markup)
+        End Function
+
         Friend Overrides Function CreateCompletionProvider() As CompletionProvider
             Return New EnumCompletionProvider()
         End Function

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

@@ -64,7 +64,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
         Friend Overrides Function IsInsertionTrigger(text As SourceText, characterPosition As Integer, options As OptionSet) As Boolean
             Return text(characterPosition) = " "c OrElse
                 text(characterPosition) = "("c OrElse
-                (text.Length > 2 AndAlso text(characterPosition) = "="c AndAlso text(characterPosition - 1) = ":"c) OrElse
+                (characterPosition > 1 AndAlso text(characterPosition) = "="c AndAlso text(characterPosition - 1) = ":"c) OrElse
                 SyntaxFacts.IsIdentifierStartCharacter(text(characterPosition)) AndAlso
                 options.GetOption(CompletionOptions.TriggerOnTypingLetters, LanguageNames.VisualBasic)
         End Function