MessageProperty constructor
Create a diagnostics property that displays a message.
Messages have no concrete value (so value will return null). The message is stored as the description.
The name, message, and level arguments must not be null.
Implementation
MessageProperty(String name, String message, {
DiagnosticLevel level = DiagnosticLevel.info,
}) : assert(name != null),
assert(message != null),
assert(level != null),
super(name, null, description: message, level: level);