Clean up RazorSyntaxTree.Diagnostics computation

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

@@ -4,9 +4,9 @@
 #nullable disable
 
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.AspNetCore.Razor.Language.Legacy;
 using Microsoft.AspNetCore.Razor.Language.Syntax;
+using Microsoft.AspNetCore.Razor.PooledObjects;
 
 namespace Microsoft.AspNetCore.Razor.Language;
 
@@ -42,20 +42,32 @@ public sealed class RazorSyntaxTree
         {
             if (_allDiagnostics == null)
             {
-                var allDiagnostics = new HashSet<RazorDiagnostic>();
+                using var allDiagnostics = new PooledArrayBuilder<RazorDiagnostic>();
+                using var pooledList = ListPool<RazorDiagnostic>.GetPooledObject(out var rootDiagnostics);
+                using var diagnosticSet = new PooledHashSet<RazorDiagnostic>();
+
                 foreach (var diagnostic in _diagnostics)
                 {
-                    allDiagnostics.Add(diagnostic);
+                    if (diagnosticSet.Add(diagnostic))
+                    {
+                        allDiagnostics.Add(diagnostic);
+                    }
                 }
 
-                var rootDiagnostics = Root.GetAllDiagnostics();
-                for (var i = 0; i < rootDiagnostics.Count; i++)
+                Root.CollectAllDiagnostics(rootDiagnostics);
+
+                if (rootDiagnostics.Count > 0)
                 {
-                    allDiagnostics.Add(rootDiagnostics[i]);
+                    foreach (var diagnostic in rootDiagnostics)
+                    {
+                        if (diagnosticSet.Add(diagnostic))
+                        {
+                            allDiagnostics.Add(diagnostic);
+                        }
+                    }
                 }
 
-                var allOrderedDiagnostics = allDiagnostics.OrderBy(diagnostic => diagnostic.Span.AbsoluteIndex);
-                _allDiagnostics = allOrderedDiagnostics.ToArray();
+                _allDiagnostics = diagnosticSet.OrderByAsArray(static d => d.Span.AbsoluteIndex);
             }
 
             return _allDiagnostics;

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Syntax/SyntaxNodeExtensions.cs

@@ -57,13 +57,13 @@ internal static class SyntaxNodeExtensions
     /// </summary>
     /// <typeparam name="TNode">The type of syntax node.</typeparam>
     /// <param name="node">The syntax node.</param>
-    /// <returns>The list of <see cref="RazorDiagnostic"/>s.</returns>
-    public static IReadOnlyList<RazorDiagnostic> GetAllDiagnostics<TNode>(this TNode node) where TNode : SyntaxNode
+    /// <param name="list"></param>
+    /// <returns>The list of <see cref="RazorDiagnostic">RazorDiagnostics</see>.</returns>
+    public static void CollectAllDiagnostics<TNode>(this TNode node, List<RazorDiagnostic> list)
+        where TNode : SyntaxNode
     {
-        var walker = new DiagnosticSyntaxWalker();
+        var walker = new DiagnosticSyntaxWalker(list);
         walker.Visit(node);
-
-        return walker.Diagnostics;
     }
 
     public static SourceLocation GetSourceLocation(this SyntaxNode node, RazorSourceDocument source)
@@ -211,16 +211,9 @@ internal static class SyntaxNodeExtensions
         return writer.ToString();
     }
 
-    private class DiagnosticSyntaxWalker : SyntaxWalker
+    private sealed class DiagnosticSyntaxWalker(List<RazorDiagnostic> diagnostics) : SyntaxWalker
     {
-        private readonly List<RazorDiagnostic> _diagnostics;
-
-        public DiagnosticSyntaxWalker()
-        {
-            _diagnostics = new List<RazorDiagnostic>();
-        }
-
-        public IReadOnlyList<RazorDiagnostic> Diagnostics => _diagnostics;
+        private readonly List<RazorDiagnostic> _diagnostics = diagnostics ?? [];
 
         public override void Visit(SyntaxNode node)
         {