anchor.diff:  
   const ParserErrorCode _MISSING_ASSIGNABLE_SELECTOR = const ParserErrorCode(
       'MISSING_ASSIGNABLE_SELECTOR',
  -    r"Missing selector such as '.<identifier>' or '[0]'.",
  +    r"Missing selector such as '.identifier' or '[0]'.",
       correction: "Try adding a selector.");
   
   const ParserErrorCode _MISSING_ASSIGNMENT_IN_INITIALIZER =
  
positive.code: 
  const ParserErrorCode _EXTERNAL_FIELD = const ParserErrorCode(
      'EXTERNAL_FIELD', r"Fields can't be declared to be 'external'.",
      correction: "Try removing the keyword 'external'.");
  
  const ParserErrorCode _EXTERNAL_METHOD_WITH_BODY = const ParserErrorCode(
      'EXTERNAL_METHOD_WITH_BODY',
  
negative.code: 
  const ParserErrorCode _EQUALITY_CANNOT_BE_EQUALITY_OPERAND = const ParserErrorCode(
      'EQUALITY_CANNOT_BE_EQUALITY_OPERAND',
      r"A comparison expression can't be an operand of another comparison expression.",
      correction: "Try putting parentheses around one of the comparisons.");
  
  const ParserErrorCode _EXPECTED_BODY = const ParserErrorCode(
      'EXPECTED_BODY', r"A #string must have a body, even if it is empty.",
  