Remove SyntaxTrivia from the compiler (#11702)

Currently, the syntax tree produced by the Razor compiler _looks_ like
it might support trivia. It even has a `SyntaxTrivia` class, methods on
`SyntaxNode` and `SyntaxToken` to handle leading and trailing trivia,
and methods on `SyntaxVisitor`, `SyntaxRewriter` and `SyntaxWalker` to
visit trivia. There're even separate properties that look like they
might provide different values depending on trivia, such as `Width` and
`FullWIdth`.

None of that is real.

The Razor parser doesn't actually produce trivia. The leading and
trailing trivia for a `SyntaxToken` is always empty. The `FullWIdth` and
`Width` properties always return the same value, as do `FullSpan` and
`Span`. Since there's so much infrastructure to support trivia, it seems
like the Razor compiler _might_ have generated it at some point, though
I suspect it was just left over from an old copy-paste from Roslyn and
never cleaned up.'

Honestly, it would be a major endeavor if the Razor compiler were
updated to support trivia, and I personally don't believe the value is
worth the effort. So, this change removes all of the compiler
infrastructure in support of syntax trivia. The goal is to make steps
toward eventually converting `SyntaxToken` to a struct. Today,
`SyntaxToken` is defined as a class, which consistently shows up as a
major source of allocations in perf traces.

I was pretty meticulous with my commit history and recommend reviewing
commit-by-commit. Most of the changes are deletions. 😄

Author: DustinCampbell

src/Compiler/Microsoft.AspNetCore.Razor.Language/legacyTest/Legacy/CSharpToMarkupSwitchTest.cs

@@ -1,9 +1,8 @@
 // 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 Microsoft.AspNetCore.Razor.Language.Components;
+using Microsoft.AspNetCore.Razor.Language.Syntax;
 using Roslyn.Test.Utilities;
 using Xunit;
 
@@ -356,16 +355,22 @@ public void CodeBlocksTrailingWhitespace_10()
             """,
             directives: [ComponentCodeDirective.Directive]);
 
-        var codeBlock = tree1.Root.ChildNodes()[0].ChildNodes()[1];
-        Assert.Equal("CSharpCodeBlockSyntax<CSharpCodeBlock> at 0::11", codeBlock.ToString());
+        var codeBlock = Assert.IsType<CSharpCodeBlockSyntax>(tree1.Root.ChildNodes()[0].ChildNodes()[1]);
+        Assert.Equal(SyntaxKind.CSharpCodeBlock, codeBlock.Kind);
+        Assert.Equal(0, codeBlock.Position);
+        Assert.Equal(11, codeBlock.Width);
 
         var children = codeBlock.ChildNodes();
         Assert.Equal(2, children.Count);
 
-        var directive = children[0];
-        Assert.Equal("RazorDirectiveSyntax<RazorDirective> at 0::9", directive.ToString());
+        var directive = Assert.IsType<RazorDirectiveSyntax>(children[0]);
+        Assert.Equal(SyntaxKind.RazorDirective, directive.Kind);
+        Assert.Equal(0, directive.Position);
+        Assert.Equal(9, directive.Width);
 
-        var whitespace = children[1];
-        Assert.Equal("RazorMetaCodeSyntax<RazorMetaCode> at 9::2", whitespace.ToString());
+        var whitespace = Assert.IsType<RazorMetaCodeSyntax>(children[1]);
+        Assert.Equal(SyntaxKind.RazorMetaCode, whitespace.Kind);
+        Assert.Equal(9, whitespace.Position);
+        Assert.Equal(2, whitespace.Width);
     }
 }

src/Compiler/Microsoft.AspNetCore.Razor.Language/legacyTest/Legacy/TagHelperRewritingTestBase.cs

@@ -47,7 +47,7 @@ internal void EvaluateData(
         var binder = new TagHelperBinder(tagHelperPrefix, descriptors);
         var rewrittenTree = TagHelperParseTreeRewriter.Rewrite(syntaxTree, binder, out _);
 
-        Assert.Equal(syntaxTree.Root.FullWidth, rewrittenTree.Root.FullWidth);
+        Assert.Equal(syntaxTree.Root.Width, rewrittenTree.Root.Width);
 
         BaselineTest(rewrittenTree);
     }

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/Legacy/TagHelperRewritingTestBase.cs

@@ -47,7 +47,7 @@ internal void EvaluateData(
         var binder = new TagHelperBinder(tagHelperPrefix, descriptors);
         var rewrittenTree = TagHelperParseTreeRewriter.Rewrite(syntaxTree, binder, out _);
 
-        Assert.Equal(syntaxTree.Root.FullWidth, rewrittenTree.Root.FullWidth);
+        Assert.Equal(syntaxTree.Root.Width, rewrittenTree.Root.Width);
 
         BaselineTest(rewrittenTree);
     }

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

@@ -1251,7 +1251,7 @@ private void Combine(HtmlContentIntermediateNode node, SyntaxNode item)
                     node.Source.Value.AbsoluteIndex,
                     node.Source.Value.LineIndex,
                     node.Source.Value.CharacterIndex,
-                    node.Source.Value.Length + item.FullWidth,
+                    node.Source.Value.Length + item.Width,
                     node.Source.Value.LineCount,
                     node.Source.Value.EndCharacterIndex);
             }
@@ -2223,7 +2223,7 @@ private void Combine(HtmlContentIntermediateNode node, SyntaxNode item)
                     node.Source.Value.AbsoluteIndex,
                     node.Source.Value.LineIndex,
                     node.Source.Value.CharacterIndex,
-                    node.Source.Value.Length + item.FullWidth,
+                    node.Source.Value.Length + item.Width,
                     node.Source.Value.LineCount,
                     node.Source.Value.EndCharacterIndex);
             }

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Legacy/CSharpCodeParser.cs

@@ -1244,7 +1244,7 @@ private RazorDirectiveBodySyntax ParseTagHelperDirective(
 
             // Accept the directive name
             var keywordToken = EatCurrentToken();
-            var keywordLength = keywordToken.FullWidth + 1 /* @ */;
+            var keywordLength = keywordToken.Width + 1 /* @ */;
 
             var foundWhitespace = At(SyntaxKind.Whitespace);
 

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Legacy/HtmlMarkupParser.cs

@@ -1783,7 +1783,7 @@ private static bool IsTypeAttribute(MarkupAttributeBlockSyntax attributeBlock)
             return false;
         }
 
-        var trimmedStartContent = attributeBlock.Name.ToFullString().TrimStart();
+        var trimmedStartContent = attributeBlock.Name.ToString().TrimStart();
         if (trimmedStartContent.StartsWith("type", StringComparison.OrdinalIgnoreCase) &&
             (trimmedStartContent.Length == 4 ||
             ValidAfterTypeAttributeNameCharacters.Contains(trimmedStartContent[4])))

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Legacy/ImplicitExpressionEditHandler.cs

@@ -85,7 +85,7 @@ protected override PartialParseResultInternal CanAcceptChange(SyntaxNode target,
 
         // Get the edit context
         char? lastChar = null;
-        if (changeRelativePosition > 0 && target.FullWidth > 0)
+        if (changeRelativePosition > 0 && target.Width > 0)
         {
             lastChar = target.GetContent()[changeRelativePosition - 1];
         }

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Legacy/TagHelperBlockRewriter.cs

@@ -108,7 +108,7 @@ public static MarkupTagHelperStartTagSyntax Rewrite(
                         // TODO: Accept more than just Markup attributes: https://github.com/aspnet/Razor/issues/96.
                         // Something like:
                         // <input @checked />
-                        var location = new SourceSpan(codeBlock.GetSourceLocation(source), codeBlock.FullWidth);
+                        var location = new SourceSpan(codeBlock.GetSourceLocation(source), codeBlock.Width);
                         var diagnostic = RazorDiagnosticFactory.CreateParsing_TagHelpersCannotHaveCSharpInTagDeclaration(location, tagName);
                         errorSink.OnError(diagnostic);
                         break;

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Legacy/TagHelperParseTreeRewriter.cs

@@ -474,7 +474,7 @@ private void ValidateBinding(
                         {
                             _errorSink.OnError(
                                 RazorDiagnosticFactory.CreateTagHelper_InconsistentTagStructure(
-                                    new SourceSpan(tagBlock.GetSourceLocation(_source), tagBlock.FullWidth),
+                                    new SourceSpan(tagBlock.GetSourceLocation(_source), tagBlock.Width),
                                     baseDescriptor!.DisplayName,
                                     descriptor.DisplayName,
                                     tagName));

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

@@ -102,7 +102,7 @@ internal string GetOriginalText(SyntaxNode node)
             throw new ArgumentNullException(nameof(node));
         }
 
-        if (node.FullWidth == 0)
+        if (node.Width == 0)
         {
             return string.Empty;
         }