diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultDirectiveSyntaxTreePass.cs b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultDirectiveSyntaxTreePass.cs
index db5383cd62..6686ca4f14 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultDirectiveSyntaxTreePass.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultDirectiveSyntaxTreePass.cs
@@ -20,7 +20,10 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             if (errorSink.Errors.Count > 0)
             {
-                var combinedErrors = syntaxTree.Diagnostics.Concat(errorSink.Errors).ToList();
+                // Temporary code while we're still using legacy diagnostics in the SyntaxTree.
+                var errors = errorSink.Errors.Select(error => RazorDiagnostic.Create(error));
+
+                var combinedErrors = syntaxTree.Diagnostics.Concat(errors);
                 syntaxTree = RazorSyntaxTree.Create(syntaxTree.Root, syntaxTree.Source, combinedErrors, syntaxTree.Options);
             }
 
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorCSharpLoweringPhase.cs b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorCSharpLoweringPhase.cs
index d03a2d852b..cdb76b39bf 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorCSharpLoweringPhase.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorCSharpLoweringPhase.cs
@@ -2,10 +2,11 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Evolution.CodeGeneration;
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using Microsoft.AspNetCore.Razor.Evolution.Intermediate;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
 {
@@ -60,12 +61,17 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             renderer.VisitDocument(irDocument);
 
-            var combinedErrors = syntaxTree.Diagnostics.Concat(renderingContext.ErrorSink.Errors).ToList();
+            var diagnostics = new List<RazorDiagnostic>();
+            diagnostics.AddRange(syntaxTree.Diagnostics);
+
+            // Temporary code while we're still using legacy diagnostics in the SyntaxTree.
+            diagnostics.AddRange(renderingContext.ErrorSink.Errors.Select(error => RazorDiagnostic.Create(error)));
+
             var csharpDocument = new RazorCSharpDocument()
             {
                 GeneratedCode = renderingContext.Writer.GenerateCode(),
                 LineMappings = renderingContext.LineMappings,
-                Diagnostics = combinedErrors
+                Diagnostics = diagnostics
             };
 
             codeDocument.SetCSharpDocument(csharpDocument);
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorSyntaxTree.cs b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorSyntaxTree.cs
index 51d74f66ca..66631bb545 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorSyntaxTree.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/DefaultRazorSyntaxTree.cs
@@ -11,7 +11,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         public DefaultRazorSyntaxTree(
             Block root,
             RazorSourceDocument source,
-            IReadOnlyList<RazorError> diagnostics,
+            IReadOnlyList<RazorDiagnostic> diagnostics,
             RazorParserOptions options)
         {
             Root = root;
@@ -20,7 +20,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             Options = options;
         }
 
-        internal override IReadOnlyList<RazorError> Diagnostics { get; }
+        public override IReadOnlyList<RazorDiagnostic> Diagnostics { get; }
 
         public override RazorParserOptions Options { get; }
 
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ErrorSink.cs b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ErrorSink.cs
index 78157ea37f..7a37ab3159 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ErrorSink.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ErrorSink.cs
@@ -8,7 +8,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
     /// <summary>
     /// Used to manage <see cref="RazorError"/>s encountered during the Razor parsing phase.
     /// </summary>
-    public class ErrorSink
+    internal class ErrorSink
     {
         private readonly List<RazorError> _errors;
 
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ITagHelperDescriptorResolver.cs b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ITagHelperDescriptorResolver.cs
index af6c394de6..bec172d6f0 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ITagHelperDescriptorResolver.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/ITagHelperDescriptorResolver.cs
@@ -10,6 +10,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
     /// </summary>
     public interface ITagHelperDescriptorResolver
     {
-        IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink);
+        IEnumerable<TagHelperDescriptor> Resolve(IList<RazorDiagnostic> errors);
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorError.cs b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorError.cs
index de7f83791f..be4358b2db 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorError.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorError.cs
@@ -7,7 +7,7 @@ using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 {
-    public class RazorError : IEquatable<RazorError>
+    internal class RazorError : IEquatable<RazorError>
     {
         internal static readonly RazorError[] EmptyArray = new RazorError[0];
 
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorParser.cs b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorParser.cs
index 2da299bf5e..c9734e7c02 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorParser.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/Legacy/RazorParser.cs
@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 {
@@ -47,7 +48,10 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             markupParser.ParseDocument();
             
             var root = context.Builder.Build();
-            var diagnostics = context.ErrorSink.Errors;
+
+            // Temporary code while we're still using legacy diagnostics in the SyntaxTree.
+            var diagnostics = context.ErrorSink.Errors.Select(error => RazorDiagnostic.Create(error));
+
             return RazorSyntaxTree.Create(root, source, diagnostics, Options);
         }
     }
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/RazorCSharpDocument.cs b/src/Microsoft.AspNetCore.Razor.Evolution/RazorCSharpDocument.cs
index ab0b396337..4663ec9b09 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/RazorCSharpDocument.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/RazorCSharpDocument.cs
@@ -12,6 +12,6 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         public IReadOnlyList<LineMapping> LineMappings { get; set; }
 
-        public IReadOnlyList<RazorError> Diagnostics { get; set; }
+        public IReadOnlyList<RazorDiagnostic> Diagnostics { get; set; }
     }
 }
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/RazorDiagnostic.cs b/src/Microsoft.AspNetCore.Razor.Evolution/RazorDiagnostic.cs
index 5724e134ee..465adf40fb 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/RazorDiagnostic.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/RazorDiagnostic.cs
@@ -68,7 +68,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         string IFormattable.ToString(string ignore, IFormatProvider formatProvider)
         {
             // Our indices are 0-based, but we we want to print them as 1-based.
-            return string.Format($"{Span.FilePath}({Span.LineIndex + 1},{Span.CharacterIndex + 1}): {Severity} {Id}: {GetMessage(formatProvider)}");
+            return $"{Span.FilePath}({Span.LineIndex + 1},{Span.CharacterIndex + 1}): {Severity} {Id}: {GetMessage(formatProvider)}";
         }
     }
 }
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/RazorSyntaxTree.cs b/src/Microsoft.AspNetCore.Razor.Evolution/RazorSyntaxTree.cs
index 9ec849c11e..e5f56bd97d 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/RazorSyntaxTree.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/RazorSyntaxTree.cs
@@ -12,7 +12,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         internal static RazorSyntaxTree Create(
             Block root,
             RazorSourceDocument source,
-            IEnumerable<RazorError> diagnostics,
+            IEnumerable<RazorDiagnostic> diagnostics,
             RazorParserOptions options)
         {
             if (root == null)
@@ -35,7 +35,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                 throw new ArgumentNullException(nameof(options));
             }
 
-            return new DefaultRazorSyntaxTree(root, source, new List<RazorError>(diagnostics), options);
+            return new DefaultRazorSyntaxTree(root, source, new List<RazorDiagnostic>(diagnostics), options);
         }
 
         public static RazorSyntaxTree Parse(RazorSourceDocument source)
@@ -59,7 +59,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             return parser.Parse(source);
         }
 
-        internal abstract IReadOnlyList<RazorError> Diagnostics { get; }
+        public abstract IReadOnlyList<RazorDiagnostic> Diagnostics { get; }
 
         public abstract RazorParserOptions Options { get; }
 
diff --git a/src/Microsoft.AspNetCore.Razor.Evolution/TagHelperBinderSyntaxTreePass.cs b/src/Microsoft.AspNetCore.Razor.Evolution/TagHelperBinderSyntaxTreePass.cs
index 7c839c6b9d..0b229ddeaa 100644
--- a/src/Microsoft.AspNetCore.Razor.Evolution/TagHelperBinderSyntaxTreePass.cs
+++ b/src/Microsoft.AspNetCore.Razor.Evolution/TagHelperBinderSyntaxTreePass.cs
@@ -45,35 +45,36 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             
             visitor.VisitBlock(syntaxTree.Root);
 
+            var errorList = new List<RazorDiagnostic>();
+            var descriptors = (IReadOnlyList<TagHelperDescriptor>)resolver.Resolve(errorList).ToList();
+
             var errorSink = new ErrorSink();
             var directives = visitor.Directives;
-            var descriptors = (IReadOnlyList<TagHelperDescriptor>)resolver.Resolve(errorSink).ToList();
-
             descriptors = ProcessDirectives(directives, descriptors, errorSink);
 
+            var root = syntaxTree.Root;
+
             if (descriptors.Count == 0)
             {
-                // No TagHelpers, add any errors if we have them.
-                if (errorSink.Errors.Count > 0)
+                if (errorSink.Errors.Count == 0 && errorList.Count == 0)
                 {
-                    var errors = CombineErrors(syntaxTree.Diagnostics, errorSink.Errors);
-                    return RazorSyntaxTree.Create(syntaxTree.Root, syntaxTree.Source, errors, syntaxTree.Options);
+                    // No TagHelpers and errors, no op.
+                    return syntaxTree;
                 }
-
-                return syntaxTree;
+            }
+            else
+            { 
+                var descriptorProvider = new TagHelperDescriptorProvider(descriptors);
+                var rewriter = new TagHelperParseTreeRewriter(descriptorProvider);
+                root = rewriter.Rewrite(root, errorSink);
             }
 
-            var descriptorProvider = new TagHelperDescriptorProvider(descriptors);
-            var rewriter = new TagHelperParseTreeRewriter(descriptorProvider);
-            var rewrittenRoot = rewriter.Rewrite(syntaxTree.Root, errorSink);
-            var diagnostics = syntaxTree.Diagnostics;
+            // Temporary code while we're still using legacy diagnostics in the SyntaxTree.
+            errorList.AddRange(errorSink.Errors.Select(error => RazorDiagnostic.Create(error)));
 
-            if (errorSink.Errors.Count > 0)
-            {
-                diagnostics = CombineErrors(diagnostics, errorSink.Errors);
-            }
+            var diagnostics = CombineErrors(syntaxTree.Diagnostics, errorList);
 
-            var newSyntaxTree = RazorSyntaxTree.Create(rewrittenRoot, syntaxTree.Source, diagnostics, syntaxTree.Options);
+            var newSyntaxTree = RazorSyntaxTree.Create(root, syntaxTree.Source, diagnostics, syntaxTree.Options);
             return newSyntaxTree;
         }
 
@@ -299,9 +300,9 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             return normalizeEmptyStringLength;
         }
 
-        private IReadOnlyList<RazorError> CombineErrors(IReadOnlyList<RazorError> errors1, IReadOnlyList<RazorError> errors2)
+        private IReadOnlyList<RazorDiagnostic> CombineErrors(IReadOnlyList<RazorDiagnostic> errors1, IReadOnlyList<RazorDiagnostic> errors2)
         {
-            var combinedErrors = new List<RazorError>(errors1.Count + errors2.Count);
+            var combinedErrors = new List<RazorDiagnostic>(errors1.Count + errors2.Count);
             combinedErrors.AddRange(errors1);
             combinedErrors.AddRange(errors2);
 
diff --git a/src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperFeature.cs b/src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperFeature.cs
index 3e072f6255..de2e541997 100644
--- a/src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperFeature.cs
+++ b/src/Microsoft.CodeAnalysis.Razor/DefaultTagHelperFeature.cs
@@ -43,7 +43,7 @@ namespace Microsoft.CodeAnalysis.Razor
             {
                 _referenceFeature = referenceFeature;
             }
-            public IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink)
+            public IEnumerable<TagHelperDescriptor> Resolve(IList<RazorDiagnostic> errors)
             {
                 var compilation = CSharpCompilation.Create("__TagHelpers", references: _referenceFeature.References);
                 return TagHelpers.GetTagHelpers(compilation);
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/DefaultDirectiveSyntaxTreePassTest.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/DefaultDirectiveSyntaxTreePassTest.cs
index 0085646fbf..ab5e66332b 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/DefaultDirectiveSyntaxTreePassTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/DefaultDirectiveSyntaxTreePassTest.cs
@@ -1,8 +1,9 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using System;
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Evolution.Legacy;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Razor.Evolution
@@ -49,6 +50,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     new SourceLocation(41 + Environment.NewLine.Length * 4, 4, 4),
                     length: 8),
             };
+            var expectedDiagnostics = expectedErrors.Select(error => RazorDiagnostic.Create(error));
             var engine = RazorEngine.Create();
             var pass = new DefaultDirectiveSyntaxTreePass()
             {
@@ -72,7 +74,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Assert
             Assert.Empty(originalTree.Diagnostics);
             Assert.NotSame(originalTree, outputTree);
-            Assert.Equal(expectedErrors, outputTree.Diagnostics);
+            Assert.Equal(expectedDiagnostics, outputTree.Diagnostics);
         }
 
         [Fact]
@@ -90,6 +92,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
                     new SourceLocation(41 + Environment.NewLine.Length * 4, 4, 4),
                     length: 8),
             };
+            var expectedDiagnostics = expectedErrors.Select(error => RazorDiagnostic.Create(error)).ToList();
             var engine = RazorEngine.Create();
             var pass = new DefaultDirectiveSyntaxTreePass()
             {
@@ -109,7 +112,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             var erroredOriginalTree = RazorSyntaxTree.Create(
                 originalTree.Root, 
                 originalTree.Source, 
-                new[] { expectedErrors[0] }, 
+                new[] { expectedDiagnostics[0] }, 
                 originalTree.Options);
 
             // Act
@@ -118,7 +121,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             // Assert
             Assert.Empty(originalTree.Diagnostics);
             Assert.NotSame(originalTree, outputTree);
-            Assert.Equal(expectedErrors, outputTree.Diagnostics);
+            Assert.Equal(expectedDiagnostics, outputTree.Diagnostics);
         }
     }
 }
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/BasicIntegrationTest.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/BasicIntegrationTest.cs
index 595334297e..7caa0a4865 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/BasicIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/IntegrationTests/BasicIntegrationTest.cs
@@ -80,18 +80,18 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
 
             var document = RazorCodeDocument.Create(TestRazorSourceDocument.Create("@!!!"));
 
+            var expected = RazorDiagnostic.Create(new RazorError(
+                LegacyResources.FormatParseError_Unexpected_Character_At_Start_Of_CodeBlock_CS("!"),
+                new SourceLocation(1, 0, 1),
+                length: 1));
+
             // Act
             engine.Process(document);
 
             // Assert
             var csharpDocument = document.GetCSharpDocument();
             var error = Assert.Single(csharpDocument.Diagnostics);
-            Assert.Equal(
-                new RazorError(
-                    LegacyResources.FormatParseError_Unexpected_Character_At_Start_Of_CodeBlock_CS("!"),
-                    new SourceLocation(1, 0, 1),
-                    length: 1),
-                error);
+            Assert.Equal(expected, error);
         }
 
         [Fact]
@@ -102,18 +102,18 @@ namespace Microsoft.AspNetCore.Razor.Evolution.IntegrationTests
 
             var document = RazorCodeDocument.Create(TestRazorSourceDocument.Create("@{"));
 
+            var expected = RazorDiagnostic.Create(new RazorError(
+                LegacyResources.FormatParseError_Expected_EndOfBlock_Before_EOF(LegacyResources.BlockName_Code, "}", "{"),
+                new SourceLocation(1, 0, 1),
+                length: 1));
+
             // Act
             engine.Process(document);
 
             // Assert
             var csharpDocument = document.GetCSharpDocument();
             var error = Assert.Single(csharpDocument.Diagnostics);
-            Assert.Equal(
-                new RazorError(
-                    LegacyResources.FormatParseError_Expected_EndOfBlock_Before_EOF(LegacyResources.BlockName_Code, "}", "{"),
-                    new SourceLocation(1, 0, 1),
-                    length: 1),
-                error);
+            Assert.Equal(expected, error);
         }
     }
 }
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/CSharpDirectivesTest.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/CSharpDirectivesTest.cs
index 348a0739a5..f841638053 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/CSharpDirectivesTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/CSharpDirectivesTest.cs
@@ -883,7 +883,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
         {
             var result = ParseCodeBlock(document, descriptors, designTime: false);
 
-            EvaluateResults(result, expected, expectedErrors);
+            EvaluateResults(result, expected, expectedErrors.Select(error => RazorDiagnostic.Create(error)).ToList());
         }
     }
 }
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/ParserTestBase.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/ParserTestBase.cs
index fec20cc3d6..5ff3556240 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/ParserTestBase.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/ParserTestBase.cs
@@ -66,7 +66,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
                 parser.ParseBlock();
 
                 var root = context.Builder.Build();
-                var diagnostics = context.ErrorSink.Errors;
+                var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
                 var options = RazorParserOptions.CreateDefaultOptions();
                 options.DesignTimeMode = designTime;
 
@@ -99,7 +99,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
                 parser.ParseBlock();
 
                 var root = context.Builder.Build();
-                var diagnostics = context.ErrorSink.Errors;
+                var diagnostics = context.ErrorSink.Errors?.Select(error => RazorDiagnostic.Create(error));
 
                 var options = RazorParserOptions.CreateDefaultOptions();
                 options.DesignTimeMode = designTime;
@@ -173,7 +173,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
             if (!ReferenceEquals(expected, IgnoreOutput))
             {
-                EvaluateResults(result, expected, expectedErrors);
+                EvaluateResults(result, expected, expectedErrors?.Select(error => RazorDiagnostic.Create(error)).ToList());
             }
         }
 
@@ -223,7 +223,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
             if (!ReferenceEquals(expected, IgnoreOutput))
             {
-                EvaluateResults(result, expected, expectedErrors);
+                EvaluateResults(result, expected, expectedErrors?.Select(error => RazorDiagnostic.Create(error)).ToList());
             }
         }
 
@@ -269,7 +269,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
 
             if (!ReferenceEquals(expected, IgnoreOutput))
             {
-                EvaluateResults(result, expected, expectedErrors);
+                EvaluateResults(result, expected, expectedErrors?.Select(error => RazorDiagnostic.Create(error)).ToList());
             }
         }
 
@@ -300,7 +300,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             EvaluateResults(result, expectedRoot, null);
         }
 
-        internal static void EvaluateResults(RazorSyntaxTree result, Block expectedRoot, IList<RazorError> expectedErrors)
+        internal static void EvaluateResults(RazorSyntaxTree result, Block expectedRoot, IList<RazorDiagnostic> expectedErrors)
         {
             EvaluateParseTree(result.Root, expectedRoot);
             EvaluateRazorErrors(result.Diagnostics, expectedErrors);
@@ -494,7 +494,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             collector.AddError("{0} - FAILED :: Actual: << Null >>", expected);
         }
 
-        internal static void EvaluateRazorErrors(IEnumerable<RazorError> actualErrors, IList<RazorError> expectedErrors)
+        internal static void EvaluateRazorErrors(IEnumerable<RazorDiagnostic> actualErrors, IList<RazorDiagnostic> expectedErrors)
         {
             var realCount = actualErrors.Count();
 
@@ -517,7 +517,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             WriteTraceLine("Expected Errors were raised:" + Environment.NewLine + FormatErrors(expectedErrors));
         }
 
-        internal static string FormatErrors(IEnumerable<RazorError> errors)
+        internal static string FormatErrors(IEnumerable<RazorDiagnostic> errors)
         {
             if (errors == null)
             {
@@ -525,9 +525,9 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             }
 
             var builder = new StringBuilder();
-            foreach (RazorError err in errors)
+            foreach (var error in errors)
             {
-                builder.AppendFormat("\t{0}", err);
+                builder.AppendFormat("\t{0}", error);
                 builder.AppendLine();
             }
             return builder.ToString();
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/TagHelperRewritingTestBase.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/TagHelperRewritingTestBase.cs
index ece3052388..3081f1b726 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/TagHelperRewritingTestBase.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/Legacy/TagHelperRewritingTestBase.cs
@@ -64,12 +64,12 @@ namespace Microsoft.AspNetCore.Razor.Evolution.Legacy
             var parseTreeRewriter = new TagHelperParseTreeRewriter(provider);
             var actualTree = parseTreeRewriter.Rewrite(syntaxTree.Root, errorSink);
 
-            var allErrors = syntaxTree.Diagnostics.Concat(errorSink.Errors);
+            var allErrors = syntaxTree.Diagnostics.Concat(errorSink.Errors.Select(error => RazorDiagnostic.Create(error)));
             var actualErrors = allErrors
-                .OrderBy(error => error.Location.AbsoluteIndex)
+                .OrderBy(error => error.Span.AbsoluteIndex)
                 .ToList();
 
-            EvaluateRazorErrors(actualErrors, expectedErrors.ToList());
+            EvaluateRazorErrors(actualErrors, expectedErrors.Select(error => RazorDiagnostic.Create(error)).ToList());
             EvaluateParseTree(actualTree, expectedOutput);
         }
     }
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/TagHelperBinderSyntaxTreePassTest.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/TagHelperBinderSyntaxTreePassTest.cs
index 4b0fe630c1..d6b793d7d1 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/TagHelperBinderSyntaxTreePassTest.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/TagHelperBinderSyntaxTreePassTest.cs
@@ -275,10 +275,11 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             var codeDocument = RazorCodeDocument.Create(sourceDocument);
             var originalTree = RazorSyntaxTree.Parse(sourceDocument);
 
-            var expectedError = new RazorError(
-                Resources.FormatTagHelperAssemblyCouldNotBeResolved("TestAssembly"),
-                new SourceLocation(Environment.NewLine.Length + 17, 1, 1),
-                length: 12);
+            var expectedError = RazorDiagnostic.Create(
+                new RazorError(
+                    Resources.FormatTagHelperAssemblyCouldNotBeResolved("TestAssembly"),
+                    new SourceLocation(Environment.NewLine.Length + 17, 1, 1),
+                    length: 12));
 
             // Act
             var outputTree = pass.Execute(codeDocument, originalTree);
@@ -294,7 +295,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
         public void Execute_RecreatesSyntaxTreeOnResolverErrors()
         {
             // Arrange
-            var resolverError = new RazorError("Test error", new SourceLocation(19, 1, 17), length: 12);
+            var resolverError = RazorDiagnostic.Create(new RazorError("Test error", new SourceLocation(19, 1, 17), length: 12));
             var engine = RazorEngine.Create(builder =>
             {
                 var resolver = new ErrorLoggingTagHelperDescriptorResolver(resolverError);
@@ -310,7 +311,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
             var codeDocument = RazorCodeDocument.Create(sourceDocument);
             var originalTree = RazorSyntaxTree.Parse(sourceDocument);
 
-            var initialError = new RazorError("Initial test error", SourceLocation.Zero, length: 1);
+            var initialError = RazorDiagnostic.Create(new RazorError("Initial test error", SourceLocation.Zero, length: 1));
             var erroredOriginalTree = RazorSyntaxTree.Create(
                 originalTree.Root,
                 originalTree.Source,
@@ -362,11 +363,12 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
             var originalTree = RazorSyntaxTree.Parse(sourceDocument);
 
-            var initialError = new RazorError("Initial test error", SourceLocation.Zero, length: 1);
-            var expectedRewritingError = new RazorError(
-                LegacyResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper("form"),
-                new SourceLocation(Environment.NewLine.Length * 2 + 30, 2, 1),
-                length: 4);
+            var initialError = RazorDiagnostic.Create(new RazorError("Initial test error", SourceLocation.Zero, length: 1));
+            var expectedRewritingError = RazorDiagnostic.Create(
+                new RazorError(
+                    LegacyResources.FormatTagHelpersParseTreeRewriter_FoundMalformedTagHelper("form"),
+                    new SourceLocation(Environment.NewLine.Length * 2 + 30, 2, 1),
+                    length: 4));
 
             var erroredOriginalTree = RazorSyntaxTree.Create(originalTree.Root, originalTree.Source, new[] { initialError }, originalTree.Options);
 
@@ -1357,16 +1359,16 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         private class ErrorLoggingTagHelperDescriptorResolver : ITagHelperDescriptorResolver
         {
-            private readonly RazorError _error;
+            private readonly RazorDiagnostic _error;
 
-            public ErrorLoggingTagHelperDescriptorResolver(RazorError error)
+            public ErrorLoggingTagHelperDescriptorResolver(RazorDiagnostic error)
             {
                 _error = error;
             }
 
-            public IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink)
+            public IEnumerable<TagHelperDescriptor> Resolve(IList<RazorDiagnostic> errors)
             {
-                errorSink.OnError(_error);
+                errors.Add(_error);
 
                 return new[] { new TagHelperDescriptor() { AssemblyName = "TestAssembly" } };
             }
diff --git a/test/Microsoft.AspNetCore.Razor.Evolution.Test/TestTagHelperDescriptorResolver.cs b/test/Microsoft.AspNetCore.Razor.Evolution.Test/TestTagHelperDescriptorResolver.cs
index 5e676db902..2305e357d6 100644
--- a/test/Microsoft.AspNetCore.Razor.Evolution.Test/TestTagHelperDescriptorResolver.cs
+++ b/test/Microsoft.AspNetCore.Razor.Evolution.Test/TestTagHelperDescriptorResolver.cs
@@ -19,7 +19,7 @@ namespace Microsoft.AspNetCore.Razor.Evolution
 
         public List<TagHelperDescriptor> TagHelpers { get; } = new List<TagHelperDescriptor>();
 
-        public IEnumerable<TagHelperDescriptor> Resolve(ErrorSink errorSink)
+        public IEnumerable<TagHelperDescriptor> Resolve(IList<RazorDiagnostic> errors)
         {
             return TagHelpers;
         }
diff --git a/test/Microsoft.AspNetCore.Razor.Test/Framework/ParserTestBase.cs b/test/Microsoft.AspNetCore.Razor.Test/Framework/ParserTestBase.cs
index eb83a9926b..5d22d33a4f 100644
--- a/test/Microsoft.AspNetCore.Razor.Test/Framework/ParserTestBase.cs
+++ b/test/Microsoft.AspNetCore.Razor.Test/Framework/ParserTestBase.cs
@@ -492,9 +492,9 @@ namespace Microsoft.AspNetCore.Razor.Test.Framework
             }
 
             var builder = new StringBuilder();
-            foreach (RazorError err in errors)
+            foreach (var error in errors)
             {
-                builder.AppendFormat("\t{0}", err);
+                builder.AppendFormat("\t{0}", error);
                 builder.AppendLine();
             }
             return builder.ToString();