[messages] Clean up references to DiagnosticCode-derived classes.

Replaces "is" tests that refer to classes derived from
`DiagnosticCode` with tests on `DiagnosticCode.type`:

- `x is ScannerErrorCode || x is ParserErrorCode` is replaced with
  `x.type == DiagnosticType.SYNTACTIC_ERROR`. This is exactly
  equivalent, because `ScannerErrorCode` and `ParserErrorCode` are the
  only two `DiagnosticCode`-derived classes whose `type` method returns
  `SYNTACTIC_ERROR`.

- `x is TodoCode` is replaced with `x.type ==
  DiagnosticType.TODO`. This is exactly equivalent, because `TodoCode`
  is the only `DiagnosticCode`-derived class whose `type` method
  returns `TODO`.

- In `statement_completion.dart`, `x is! HintCode && x is!
  WarningCode` is replaced with `x.type ==
  DiagnosticType.SYNTACTIC_ERROR`. The new test is less accepting: for
  example, it previously accepted diagnostics of type
  `StaticWarningCode`. This test is used to short-cut the generation
  of statement completions such as completing an incomplete `do`
  statement. These completions are only necessary to generate if there
  is a syntax error, so there should be no user-visible behavior
  change.

- In `fix_processor.dart`, `x is LintCode || x is HintCode || x is
  WarningCode` is replaced with `x.type == DiagnosticType.LINT ||
  x.type == DiagnosticType.STATIC_WARNING`. The new test is more
  accepting: it now accepts any diagnostic code whose type is
  `STATIC_WARNING`, when previously it only accepted warnings of type
  `WarningCode` (and rejected warnings of types like
  `StaticWarningCode`). This test determines when quick fixes like
  "ignore diagnostic on this line" are offered, so the behavior change
  is appropriate.

- Also replaces a documentation reference to `TodoCode` (in
  `todo_codes.dart`) with a reference to `DiagnosticType.TODO`.

These changes pave the way for a follow-up CL in which I plan to
eliminate these derived classes entirely.

Change-Id: I6a6a69647ff62dfe06b0219d8b292da53427cf0d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/461140
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

pkg/analysis_server/lib/src/g3/utilities.dart

@@ -8,6 +8,7 @@ import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/source/line_info.dart';
 import 'package:analyzer/src/dart/analysis/experiments.dart';
@@ -37,11 +38,7 @@ String format(String content, {Version? languageVersion}) {
 ParseStringResult sortDirectives(String contents, {String? fileName}) {
   var (unit, diagnostics) = _parse(contents, fullName: fileName);
   var parseErrors = diagnostics
-      .where(
-        (d) =>
-            d.diagnosticCode is ScannerErrorCode ||
-            d.diagnosticCode is ParserErrorCode,
-      )
+      .where((d) => d.diagnosticCode.type == DiagnosticType.SYNTACTIC_ERROR)
       .toList();
   if (parseErrors.isNotEmpty) {
     return ParseStringResultImpl(contents, unit, parseErrors);

pkg/analysis_server/lib/src/handler/legacy/legacy_handler.dart

@@ -10,7 +10,7 @@ import 'package:analysis_server/src/legacy_analysis_server.dart';
 import 'package:analysis_server/src/protocol/protocol_internal.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart';
-import 'package:analyzer/src/dart/error/syntactic_errors.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/util/performance/operation_performance.dart';
 import 'package:analyzer/src/utilities/cancellation.dart';
 import 'package:dart_style/dart_style.dart';
@@ -82,8 +82,7 @@ abstract class LegacyHandler {
   int numberOfSyntacticErrors(List<Diagnostic> diagnostics) {
     var numScanParseErrors = 0;
     for (var diagnostic in diagnostics) {
-      if (diagnostic.diagnosticCode is ScannerErrorCode ||
-          diagnostic.diagnosticCode is ParserErrorCode) {
+      if (diagnostic.diagnosticCode.type == DiagnosticType.SYNTACTIC_ERROR) {
         numScanParseErrors++;
       }
     }

pkg/analysis_server/lib/src/lsp/handlers/commands/simple_edit_handler.dart

@@ -11,8 +11,7 @@ import 'package:analysis_server/src/lsp/mapping.dart';
 import 'package:analysis_server/src/lsp/source_edits.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart' as engine;
-import 'package:analyzer/src/dart/scanner/scanner.dart' as engine;
-import 'package:analyzer/src/generated/parser.dart' as engine;
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
 
 abstract class SimpleEditCommandHandler<S extends AnalysisServer>
@@ -23,9 +22,7 @@ abstract class SimpleEditCommandHandler<S extends AnalysisServer>
 
   bool hasScanParseErrors(List<engine.Diagnostic> diagnostics) {
     return diagnostics.any(
-      (d) =>
-          d.diagnosticCode is engine.ScannerErrorCode ||
-          d.diagnosticCode is engine.ParserErrorCode,
+      (d) => d.diagnosticCode.type == DiagnosticType.SYNTACTIC_ERROR,
     );
   }
 

pkg/analysis_server/lib/src/services/completion/statement/statement_completion.dart

@@ -188,8 +188,7 @@ class StatementCompletionProcessor {
     }
     for (var diagnostic in statementContext.resolveResult.diagnostics) {
       if (diagnostic.offset >= node.offset && diagnostic.offset <= node.end) {
-        if (diagnostic.diagnosticCode is! HintCode &&
-            diagnostic.diagnosticCode is! WarningCode) {
+        if (diagnostic.diagnosticCode.type == DiagnosticType.SYNTACTIC_ERROR) {
           diagnostics.add(diagnostic);
         }
       }

pkg/analysis_server/lib/src/services/correction/bulk_fix_processor.dart

@@ -32,7 +32,6 @@ import 'package:analyzer/source/file_source.dart';
 import 'package:analyzer/source/source.dart';
 import 'package:analyzer/source/source_range.dart';
 import 'package:analyzer/src/analysis_rule/rule_context.dart';
-import 'package:analyzer/src/dart/error/syntactic_errors.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/lint/linter_visitor.dart';
 import 'package:analyzer/src/lint/registry.dart';
@@ -918,9 +917,7 @@ class BulkFixProcessor {
         var diagnostics = unitResult.diagnostics;
         // Check if there are scan/parse errors in the file.
         var hasParseErrors = diagnostics.any(
-          (d) =>
-              d.diagnosticCode is ScannerErrorCode ||
-              d.diagnosticCode is ParserErrorCode,
+          (d) => d.diagnosticCode.type == DiagnosticType.SYNTACTIC_ERROR,
         );
         if (hasParseErrors) {
           // Cannot process files with parse errors.

pkg/analysis_server_plugin/lib/src/correction/fix_processor.dart

@@ -9,7 +9,7 @@ import 'package:analysis_server_plugin/src/correction/fix_generators.dart';
 import 'package:analysis_server_plugin/src/correction/fix_in_file_processor.dart';
 import 'package:analysis_server_plugin/src/correction/ignore_diagnostic.dart';
 import 'package:analysis_server_plugin/src/correction/performance.dart';
-import 'package:analyzer/src/error/codes.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 import 'package:analyzer_plugin/utilities/change_builder/conflicting_edit_exception.dart';
@@ -152,9 +152,9 @@ class FixProcessor {
       }
     }
 
-    if (diagnosticCode is LintCode ||
-        diagnosticCode is HintCode ||
-        diagnosticCode is WarningCode) {
+    if (diagnosticCode.type == DiagnosticType.LINT ||
+        diagnosticCode.type == DiagnosticType.HINT ||
+        diagnosticCode.type == DiagnosticType.STATIC_WARNING) {
       for (var generator in registeredFixGenerators.ignoreProducerGenerators) {
         var producer = generator(context: context);
         if (producer.fixKind == ignoreErrorAnalysisFileKind) {

pkg/analyzer/lib/src/dart/error/todo_codes.dart

@@ -6,7 +6,8 @@ import 'package:_fe_analyzer_shared/src/base/errors.dart';
 
 part 'package:analyzer/src/dart/error/todo_codes.g.dart';
 
-/// Static helper methods and properties for working with [TodoCode]s.
+/// Static helper methods and properties for working with [DiagnosticType.TODO]
+/// codes.
 class Todo {
   static const _codes = {
     'TODO': TodoCode.todo,

pkg/analyzer/test/src/task/strong/inferred_type_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/utilities/extensions/file_system.dart';
@@ -5906,7 +5907,7 @@ main() {
     assertErrorsInList(
       result.diagnostics.where((e) {
         return e.diagnosticCode != WarningCode.unusedLocalVariable &&
-            e.diagnosticCode is! TodoCode;
+            e.diagnosticCode.type != DiagnosticType.TODO;
       }).toList(),
       expectedDiagnostics,
     );

pkg/analyzer/tool/fine/ab_mutate/engine.dart

@@ -9,10 +9,10 @@ import 'package:analyzer/dart/analysis/analysis_context_collection.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/diagnostic/diagnostic.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/file_system/overlay_file_system.dart';
 import 'package:analyzer/source/error_processor.dart';
 import 'package:analyzer/src/dart/analysis/analysis_context_collection.dart';
-import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/util/performance/operation_performance.dart';
 import 'package:analyzer/src/utilities/extensions/object.dart';
 
@@ -77,7 +77,7 @@ class ABEngine {
       if (errorsResult is ErrorsResult) {
         for (var diagnostic in errorsResult.diagnostics) {
           // Filter TODOs, not interesting for comparison.
-          if (diagnostic.diagnosticCode is TodoCode) {
+          if (diagnostic.diagnosticCode.type == DiagnosticType.TODO) {
             continue;
           }
           var severityName = _getProcessedSeverity(errorsResult, diagnostic);