[messages] Remove _SyntacticErrorGenerator.checkForManualChanges.

Removes the method `_SyntacticErrorGenerator.checkForManualChanges`,
which was part of a previous effort to unify analyzer and CFE error
codes, and is not needed by the current effort. Removing this method
will make it easier to clean up and refactor the logic for handling
shared error codes.

Change-Id: I6a6a6964721c4ad0d4ca7336a97346681d476781
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/451825
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: stereotype441

pkg/analyzer/tool/messages/generate.dart

@@ -31,9 +31,7 @@ import 'error_code_info.dart';
 Future<void> main() async {
   await GeneratedContent.generateAll(pkg_root.packageRoot, allTargets);
 
-  _SyntacticErrorGenerator()
-    ..checkForManualChanges()
-    ..printSummary();
+  _SyntacticErrorGenerator().printSummary();
 }
 
 /// A list of all targets generated by this code generator.
@@ -327,36 +325,6 @@ class _SyntacticErrorGenerator {
 
   _SyntacticErrorGenerator._(this.errorConverterSource, this.parserSource);
 
-  void checkForManualChanges() {
-    // Check for ParserErrorCodes that could be removed from
-    // error_converter.dart now that those ParserErrorCodes are auto generated.
-    int converterCount = 0;
-    for (var errorCode
-        in sharedToAnalyzerErrorCodeTables.infoToAnalyzerCode.values) {
-      if (errorConverterSource.contains('"$errorCode"')) {
-        if (converterCount == 0) {
-          print('');
-          print(
-            'The following ParserErrorCodes could be removed'
-            ' from error_converter.dart:',
-          );
-        }
-        print('  $errorCode');
-        ++converterCount;
-      }
-    }
-    if (converterCount > 3) {
-      print('  $converterCount total');
-    }
-
-    // Fail if there are manual changes to be made, but do so
-    // in a fire and forget manner so that the files are still generated.
-    if (converterCount > 0) {
-      print('');
-      throw 'Error: missing manual code changes';
-    }
-  }
-
   void printSummary() {
     // Build a map of error message to ParserErrorCode
     var messageToName = <String, String>{};