handlerTypeFromExpression function

HandlerType handlerTypeFromExpression(AST handler)

Classifies this event binding by it's form.

The simple form looks like

(event)="handler($event)"

or

(event)="handler()"

Since these types of handlers are so common, we can optimize the code generated for them.

Implementation

HandlerType handlerTypeFromExpression(AST handler) {
  var eventHandler = handler;
  if (eventHandler is! MethodCall) {
    return HandlerType.notSimple;
  }
  var call = eventHandler;
  if (call.receiver is! ImplicitReceiver || call.namedArgs.isNotEmpty) {
    return HandlerType.notSimple;
  }
  if (call.args.isEmpty) {
    return HandlerType.simpleNoArgs;
  }
  if (call.args.length != 1) {
    return HandlerType.notSimple;
  }
  var singleArg = call.args.single;
  if (singleArg is! PropertyRead) {
    return HandlerType.notSimple;
  }
  var property = singleArg;
  if (property.name == EventHandlerVars.event.name &&
      property.receiver is ImplicitReceiver) {
    return HandlerType.simpleOneArg;
  } else {
    return HandlerType.notSimple;
  }
}