anchor.diff:     * value.
      */
     static const CompileTimeErrorCode CONST_EVAL_TYPE_BOOL =
  -      const CompileTimeErrorCode(
  -          'CONST_EVAL_TYPE_BOOL', "An expression of type 'bool' was expected");
  +      const CompileTimeErrorCode('CONST_EVAL_TYPE_BOOL',
  +          "In constant expressions, operand(s) of this operator must be of type 'bool'");
   
     /**
      * 12.11.2 Const: An expression of one of the forms e1 == e2 or e1 != e2 where
  
positive.code:    */
    static const CompileTimeErrorCode CONST_EVAL_TYPE_BOOL_NUM_STRING =
        const CompileTimeErrorCode('CONST_EVAL_TYPE_BOOL_NUM_STRING',
            "An expression of type 'bool', 'num', 'String' or 'null' was expected");
  
    /**
     * 12.11.2 Const: An expression of one of the forms ~e, e1 ^ e2, e1 & e2,
  
negative.code:    * value or to null.
     */
    static const CompileTimeErrorCode CONST_EVAL_TYPE_NUM =
        const CompileTimeErrorCode('CONST_EVAL_TYPE_NUM',
            "In constant expressions, operand(s) of this operator must be of type 'num'");
  
    /**
     * 12.11.2 Const: It is a compile-time error if evaluation of a constant
  