Brent Simmons

Filed as rdar://22109003

@brentsimmons The reason why `messages as [NodeRepresentedObject]` doesn’t work is because it would make `as` be unexpectedly expensive.

@eridius It just has to check once that EmailMessage is a NodeRepresentedObject. It shouldn't have to check for each item.

@brentsimmons It’s not a type-check. The in-memory representation is different. It has to allocate a new array with the new values.

@eridius There may be plenty of benefits to that — but it makes app-writing a little more difficult.

@brentsimmons It seems to me the occasional `foo.map({$0})` is a small price to pay for avoiding hidden performance gotchas.

@eridius I’d argue that, instead, there shouldn’t be a hidden performance gotcha.

@brentsimmons That would be nice, but the only way to solve this without a new array basically requires all protocols to use message-passing