diff --git a/src/EditorFeatures/Test2/IntelliSense/CSharpCompletionCommandHandlerTests_Regex.vb b/src/EditorFeatures/Test2/IntelliSense/CSharpCompletionCommandHandlerTests_Regex.vb
index 1756e0aad120d..90f5bb8416d67 100644
--- a/src/EditorFeatures/Test2/IntelliSense/CSharpCompletionCommandHandlerTests_Regex.vb
+++ b/src/EditorFeatures/Test2/IntelliSense/CSharpCompletionCommandHandlerTests_Regex.vb
@@ -6,7 +6,6 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.IntelliSense
     <[UseExportProvider]>
     <Trait(Traits.Feature, Traits.Features.Completion)>
     Public Class CSharpCompletionCommandHandlerTests_Regex
-
         <WpfTheory, CombinatorialData>
         Public Async Function ExplicitInvoke(showCompletionInArgumentLists As Boolean) As Task
             Using state = TestStateFactory.CreateCSharpTestState(
@@ -29,6 +28,28 @@ class c
             End Using
         End Function
 
+        <WpfTheory, CombinatorialData>
+        Public Async Function ExplicitInvoke_Utf8(showCompletionInArgumentLists As Boolean) As Task
+            Using state = TestStateFactory.CreateCSharpTestState(
+                <Document><![CDATA[
+using System.Text.RegularExpressions;
+class c
+{
+    void goo()
+    {
+        var r = new Regex("$$"u8);
+    }
+}
+]]></Document>, showCompletionInArgumentLists:=showCompletionInArgumentLists)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("\A", inlineDescription:=FeaturesResources.Regex_start_of_string_only_short)
+                state.SendTab()
+                Await state.AssertNoCompletionSession()
+                Assert.Contains("new Regex(""\\A""u8)", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+            End Using
+        End Function
+
         <WpfTheory, CombinatorialData>
         Public Async Function ExplicitInvoke_VerbatimString(showCompletionInArgumentLists As Boolean) As Task
             Using state = TestStateFactory.CreateCSharpTestState(
@@ -51,6 +72,74 @@ class c
             End Using
         End Function
 
+        <WpfTheory, CombinatorialData>
+        Public Async Function ExplicitInvoke_VerbatimUtf8String(showCompletionInArgumentLists As Boolean) As Task
+            Using state = TestStateFactory.CreateCSharpTestState(
+                <Document><![CDATA[
+using System.Text.RegularExpressions;
+class c
+{
+    void goo()
+    {
+        var r = new Regex(@"$$"u8);
+    }
+}
+]]></Document>, showCompletionInArgumentLists:=showCompletionInArgumentLists)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("\A")
+                state.SendTab()
+                Await state.AssertNoCompletionSession()
+                Assert.Contains("new Regex(@""\A""u8)", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+            End Using
+        End Function
+
+        <WpfTheory, CombinatorialData>
+        Public Async Function ExplicitInvoke_RawSingleLineString(showCompletionInArgumentLists As Boolean) As Task
+            Using state = TestStateFactory.CreateCSharpTestState(
+                <Document><![CDATA[
+using System.Text.RegularExpressions;
+class c
+{
+    void goo()
+    {
+        var r = new Regex("""$$ """);
+    }
+}
+]]></Document>, showCompletionInArgumentLists:=showCompletionInArgumentLists)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("\A")
+                state.SendTab()
+                Await state.AssertNoCompletionSession()
+                Assert.Contains("new Regex(""""""\A """""")", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+            End Using
+        End Function
+
+        <WpfTheory, CombinatorialData>
+        Public Async Function ExplicitInvoke_RawMultiLineString(showCompletionInArgumentLists As Boolean) As Task
+            Using state = TestStateFactory.CreateCSharpTestState(
+                <Document><![CDATA[
+using System.Text.RegularExpressions;
+class c
+{
+    void goo()
+    {
+        var r = new Regex("""
+            $$
+            """);
+    }
+}
+]]></Document>, showCompletionInArgumentLists:=showCompletionInArgumentLists)
+
+                state.SendInvokeCompletionList()
+                Await state.AssertSelectedCompletionItem("\A")
+                state.SendTab()
+                Await state.AssertNoCompletionSession()
+                Assert.Contains(" \A", state.GetLineTextFromCaretPosition(), StringComparison.Ordinal)
+            End Using
+        End Function
+
         <WpfTheory, CombinatorialData>
         Public Async Function TestCaretPlacement(showCompletionInArgumentLists As Boolean) As Task
             Using state = TestStateFactory.CreateCSharpTestState(
diff --git a/src/EditorFeatures/Test2/ReferenceHighlighting/CSharpReferenceHighlightingTests.vb b/src/EditorFeatures/Test2/ReferenceHighlighting/CSharpReferenceHighlightingTests.vb
index 6c94879c8aa9a..fb51d56fc8a4d 100644
--- a/src/EditorFeatures/Test2/ReferenceHighlighting/CSharpReferenceHighlightingTests.vb
+++ b/src/EditorFeatures/Test2/ReferenceHighlighting/CSharpReferenceHighlightingTests.vb
@@ -8,8 +8,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
     Public Class CSharpReferenceHighlightingTests
         Inherits AbstractReferenceHighlightingTests
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestVerifyNoHighlightsWhenOptionDisabled(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
                 <Workspace>
@@ -26,8 +25,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
                 optionIsEnabled:=False)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestVerifyHighlightsForClass(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
                 <Workspace>
@@ -41,8 +39,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
                 </Workspace>, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestVerifyHighlightsForScriptReference(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
                 <Workspace>
@@ -60,8 +57,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
                 </Workspace>, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestVerifyHighlightsForCSharpClassWithConstructor(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
                 <Workspace>
@@ -79,9 +75,8 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
                 </Workspace>, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(538721, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/538721")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestVerifyHighlightsForCSharpClassWithSynthesizedConstructor(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
                 <Workspace>
@@ -99,8 +94,7 @@ Namespace Microsoft.CodeAnalysis.Editor.UnitTests.ReferenceHighlighting
                 </Workspace>, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         <WorkItem(528436, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/528436")>
         Public Async Function TestVerifyHighlightsOnCloseAngleOfGeneric(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
@@ -123,8 +117,7 @@ class {|Definition:Program|}
                 </Workspace>, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         <WorkItem(570809, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/570809")>
         Public Async Function TestVerifyNoHighlightsOnAsyncLambda(testHost As TestHost) As Task
             Await VerifyHighlightsAsync(
@@ -149,9 +142,8 @@ class Program
                 </Workspace>, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(543768, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/543768")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAlias1(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -175,9 +167,8 @@ namespace X
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(543768, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/543768")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAlias2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -201,9 +192,8 @@ namespace X
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(543768, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/543768")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAlias3(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -227,9 +217,8 @@ namespace X
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(552000, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/552000")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAlias4(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -250,9 +239,8 @@ namespace N
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(542830, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/542830")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestHighlightThroughVar1(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -275,9 +263,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(542830, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/542830")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestHighlightThroughVar2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -300,9 +287,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(542830, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/542830")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestHighlightThroughVar3(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -327,9 +313,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(545648, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/545648")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestUsingAliasAndTypeWithSameName1(testHost As TestHost) As Task
             Dim input =
 <Workspace>
@@ -344,9 +329,8 @@ class X { }
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(545648, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/545648")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestUsingAliasAndTypeWithSameName2(testHost As TestHost) As Task
             Dim input =
 <Workspace>
@@ -361,9 +345,8 @@ class {|Definition:$$X|} { }
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(567959, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/567959")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAccessor1(testHost As TestHost) As Task
             Dim input =
 <Workspace>
@@ -390,9 +373,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(567959, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/567959")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestAccessor2(testHost As TestHost) As Task
             Dim input =
 <Workspace>
@@ -440,9 +422,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(531620, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/531620")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestHighlightDynamicallyBoundMethod(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -472,9 +453,8 @@ class A
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
+        <WpfTheory, CombinatorialData>
         <WorkItem(531624, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/531624")>
-        <WpfTheory>
-        <CombinatorialData>
         Public Async Function TestHighlightParameterizedPropertyParameter(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -497,8 +477,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestInterpolatedString1(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -520,8 +499,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestInterpolatedString2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -543,8 +521,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestWrittenReference(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -565,8 +542,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestWrittenReference2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -587,8 +563,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestPatternMatchingType1(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -612,8 +587,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestPatternMatchingType2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -637,8 +611,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestPatternMatchingTypeScoping1(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -669,8 +642,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestPatternMatchingTypeScoping2(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -701,10 +673,8 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestRegexReference1(testHost As TestHost) As Task
-
             Dim input =
            <Workspace>
                <Project Language="C#" CommonReferences="true">
@@ -725,8 +695,57 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
+        <WorkItem(65836, "https://github.com/dotnet/roslyn/issues/65836")>
+        Public Async Function TestRegexReference_RawStringInBounds(testHost As TestHost) As Task
+            Dim input =
+           <Workspace>
+               <Project Language="C#" CommonReferences="true">
+                   <Document>
+using System.Text.RegularExpressions;
+
+class C
+{
+    void Goo()
+    {
+        var r = new Regex("""
+           {|Reference:(a)|}\0{|Reference:\$$1|}
+           """);
+    }
+}
+                    </Document>
+               </Project>
+           </Workspace>
+
+            Await VerifyHighlightsAsync(input, testHost)
+        End Function
+
+        <WpfTheory, CombinatorialData>
+        <WorkItem(65836, "https://github.com/dotnet/roslyn/issues/65836")>
+        Public Async Function TestRegexReference_RawStringOutOfBounds(testHost As TestHost) As Task
+            Dim input =
+           <Workspace>
+               <Project Language="C#" CommonReferences="true">
+                   <Document>
+using System.Text.RegularExpressions;
+
+class C
+{
+    void Goo()
+    {
+        var r = new Regex("""
+    $$       (a)\0\1
+           """);
+    }
+}
+                    </Document>
+               </Project>
+           </Workspace>
+
+            Await VerifyHighlightsAsync(input, testHost)
+        End Function
+
+        <WpfTheory, CombinatorialData>
         Public Async Function TestHighlightParamAndCommentsCursorOnDefinition(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -753,8 +772,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestHighlightParamAndCommentsCursorOnReference(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -781,8 +799,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestHighlightParamAndCommentsDefinitionNestedBetweenReferences(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -809,8 +826,7 @@ class C
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestNotOnNewInObjectCreation(testHost As TestHost) As Task
             Dim input =
             <Workspace>
@@ -834,8 +850,7 @@ namespace X
             Await VerifyHighlightsAsync(input, testHost)
         End Function
 
-        <WpfTheory>
-        <CombinatorialData>
+        <WpfTheory, CombinatorialData>
         Public Async Function TestOnTypeInObjectCreation(testHost As TestHost) As Task
             Dim input =
             <Workspace>
diff --git a/src/Features/CSharp/Portable/EmbeddedLanguages/EmbeddedLanguageUtilities.cs b/src/Features/CSharp/Portable/EmbeddedLanguages/EmbeddedLanguageUtilities.cs
index e82e6a5995795..317e754a4970c 100644
--- a/src/Features/CSharp/Portable/EmbeddedLanguages/EmbeddedLanguageUtilities.cs
+++ b/src/Features/CSharp/Portable/EmbeddedLanguages/EmbeddedLanguageUtilities.cs
@@ -2,10 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
-
-using System.Diagnostics;
 using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.CSharp.Features.EmbeddedLanguages
 {
@@ -18,21 +16,22 @@ internal static void AddComment(SyntaxEditor editor, SyntaxToken stringLiteral,
                 SyntaxFactory.ElasticSpace);
             var newStringLiteral = stringLiteral.WithLeadingTrivia(
                 stringLiteral.LeadingTrivia.AddRange(triviaList));
-            editor.ReplaceNode(stringLiteral.Parent, stringLiteral.Parent.ReplaceToken(stringLiteral, newStringLiteral));
+            var parent = stringLiteral.GetRequiredParent();
+            editor.ReplaceNode(
+               parent,
+               parent.ReplaceToken(stringLiteral, newStringLiteral));
         }
 
         public static string EscapeText(string text, SyntaxToken token)
         {
-            // This function is called when Completion needs to escape something its going to
-            // insert into the user's string token.  This means that we only have to escape
-            // things that completion could insert.  In this case, the only regex character
-            // that is relevant is the \ character, and it's only relevant if we insert into
-            // a normal string and not a verbatim string.  There are no other regex characters
-            // that completion will produce that need any escaping. 
-            Debug.Assert(token.Kind() == SyntaxKind.StringLiteralToken);
-            return token.IsVerbatimStringLiteral()
-                ? text
-                : text.Replace(@"\", @"\\");
+            // This function is called when Completion needs to escape something its going to insert into the user's
+            // string token.  This means that we only have to escape things that completion could insert.  In this case,
+            // the only regex character that is relevant is the \ character, and it's only relevant if we insert into a
+            // normal string and not a verbatim string.  There are no other regex characters that completion will
+            // produce that need any escaping.
+            return token.Kind() is SyntaxKind.StringLiteralToken or SyntaxKind.Utf8StringLiteralToken && !token.IsVerbatimStringLiteral()
+                ? text.Replace(@"\", @"\\")
+                : text;
         }
     }
 }
diff --git a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
index 1aba88e39213d..0db80681639a7 100644
--- a/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
+++ b/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/EmbeddedLanguages/VirtualChars/VirtualCharSequence.Chunks.cs
@@ -62,7 +62,12 @@ public ImmutableSegmentedListChunk(ImmutableSegmentedList<VirtualChar> array)
 
                     return 0;
                 });
-                Debug.Assert(index >= 0);
+
+                // Characters can be discontiguous (for example, in multi-line-raw-string literals).  So if the
+                // position is in one of the gaps, it won't be able to find a corresponding virtual char.
+                if (index < 0)
+                    return null;
+
                 return _array[index];
             }
         }