anchor.diff:            "The parameter '{0}' cannot have a value of 'null' because of its "
                 "type, but no default value it valid, so it must be a required "
                 "parameter.",
  -          correction: "Try making this nullable (by adding a '?') or "
  +          correction: "Try making this nullable (by adding a '?'), "
  +              "adding a default value, or "
                 "making this a required parameter.");
   
     /**
  
positive.code:           'DEFAULT_LIST_CONSTRUCTOR_MISMATCH',
            "A list whose values cannot be 'null' cannot be given an initial length "
                "because the initial values would all be 'null'.",
            correction: "Try removing the argument.");
  
    /**
     * 6.2.1 Required Formals: By means of a function signature that names the
  
negative.code:    */
    static const CompileTimeErrorCode GENERIC_FUNCTION_TYPE_CANNOT_BE_BOUND =
        const CompileTimeErrorCode('GENERIC_FUNCTION_TYPE_CANNOT_BE_BOUND',
            "Generic function types may not be used as type parameter bounds",
            correction: "Try making the free variable in the function type part"
                " of the larger declaration signature");
  
    static const CompileTimeErrorCode FOR_IN_WITH_CONST_VARIABLE =
        const CompileTimeErrorCode('FOR_IN_WITH_CONST_VARIABLE',
  