anchor.diff:  enum _ElementType { string, block }
   
   class _ElementTypeAndVal extends _TypeAndVal<_ElementType, String> {
  -  _ElementTypeAndVal(var type, var value) : super(type, value);
  +  _ElementTypeAndVal(_ElementType type, String value) : super(type, value);
   }
   
   /// Block type.
   enum _BlockType { plural, ordinal, select, simple, string, unknown }
   
   class _BlockTypeAndVal extends _TypeAndVal<_BlockType, Object> {
  -  _BlockTypeAndVal(var type, var value) : super(type, value);
  +  _BlockTypeAndVal(_BlockType type, Object value) : super(type, value);
   }
  
positive.code:     var replaceRegex = _ordinalBlockRe;
      pattern = pattern.replaceFirstMapped(replaceRegex, (match) {
        // string, name
        argumentName = match.group(1)!;
        return '';
      });
  
  
negative.code: 
      // First replace '' with single quote placeholder since they can be found
      // inside other literals.
      pattern = pattern.replaceAllMapped(_patternDoubleApostrophe, (match) {
        literals.add("'");
        return buildPlaceholder(literals);
      });
  
      pattern = pattern.replaceAllMapped(_regexLiteral, (match) {
        // match, text
        var text = match[1]!;
        literals.add(text);
        return buildPlaceholder(literals);
      });
  