Method reference assignment compatibility

Mark Mahieu mark at
Thu Jun 26 04:27:21 PDT 2008


Given a method with the signature:

	void subscribe(Topic topic, {Message=>void} processor)

I might want to pass myPriorityQueue#offer(Message) as the second  
argument, but this isn't permitted since Queue<E>#offer(E) has a  
boolean rather than void result type.

Obviously I can get around this using a closure literal {Message msg  
=> myPriorityQueue.offer(msg);}, however given:

	final class Processor {
		// ...
		void process(Message msg) {

In Java 6, if I were to alter the process(Message) method to return a  
value, such as a boolean indicating success or failure of the  
operation, then I'd break binary compatibility but I think source  
compatibility would be preserved.

Under BGGA, if I had used a method reference myProcessor#process 
(Message) as the argument to the subscribe() method above, then this  
API change will have broken source compatibility.

So my question is: would it be problematic to allow a method  
reference with a non-void result type to be assignment compatible  
with an interface or function type with a void result type (all other  
conditions being satisfied)?



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