Clean up and enable nullability for CodeRenderingContext and DefaultDocumentWriter

Author: DustinCampbell

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/ChecksumUtilities.cs

@@ -4,7 +4,6 @@
 using System;
 using System.Collections.Immutable;
 using System.Globalization;
-using System.Text;
 using Microsoft.AspNetCore.Razor.PooledObjects;
 
 namespace Microsoft.AspNetCore.Razor.Language;

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/CodeGeneration/CodeRenderingContext.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -28,6 +26,9 @@ public sealed class CodeRenderingContext : IDisposable
     private readonly ImmutableArray<SourceMapping>.Builder _sourceMappings;
     private readonly ImmutableArray<LinePragma>.Builder _linePragmas;
 
+    private IntermediateNodeVisitor? _visitor;
+    public IntermediateNodeVisitor Visitor => _visitor.AssumeNotNull();
+
     public string DocumentKind => _documentNode.DocumentKind;
 
     public CodeRenderingContext(
@@ -74,12 +75,16 @@ public void Dispose()
         CodeWriter.Dispose();
     }
 
-    // This will be initialized by the document writer when the context is 'live'.
-    public IntermediateNodeVisitor Visitor { get; set; }
+    // This will be called by the document writer when the context is 'live'.
+    public void SetVisitor(IntermediateNodeVisitor visitor)
+    {
+        _visitor = visitor;
+    }
 
     public IntermediateNodeWriter NodeWriter => _scopeStack.Peek().Writer;
 
-    public IntermediateNode Parent => _ancestorStack.Count == 0 ? null : _ancestorStack.Peek();
+    public IntermediateNode? Parent
+        => _ancestorStack.Count == 0 ? null : _ancestorStack.Peek();
 
     public void AddDiagnostic(RazorDiagnostic diagnostic)
     {