An enum type for defining the different logging levels. By default, ERROR and WARNING messages are printed to sterr. MESSAGE messages are printed to stdout, and others are ignored.

class Level {
 /// An error occurred and an operation could not be completed. Usually shown
 /// to the user on stderr.
 static const ERROR = const Level._("ERR ");

 /// Something unexpected happened, but the program was able to continue,
 /// though possibly in a degraded fashion.
 static const WARNING = const Level._("WARN");

 /// A message intended specifically to be shown to the user.
 static const MESSAGE = const Level._("MSG ");

 /// Some interaction with the external world occurred, such as a network
 /// operation, process spawning, or file IO.
 static const IO = const Level._("IO  ");

 /// Incremental output during pub's version constraint solver.
 static const SOLVER = const Level._("SLVR");

 /// Fine-grained and verbose additional information. Can be used to provide
 /// program state context for other logs (such as what pub was doing when an
 /// IO operation occurred) or just more detail for an operation.
 static const FINE = const Level._("FINE");

 const Level._(this.name);
 final String name;

 String toString() => name;
 int get hashCode => name.hashCode;
}