Andrea Faulds <a...@ajf.me> 於 2016年4月15日 星期五寫道： > > > This is something that particularly concerns me about union types, in that > they reduce type safety. If you have a union type of Foo|Bar for some > variable, then the set of methods you can call on that variable is actually > the intersection, not the union, of the set of methods you can call on Foo > and Bar. Which, unless those two classes share some interface, is probably > an empty set. So there's nothing you can actually do safely with it without > doing checks within the body of the function, and if you're doing that, > then why do we have a type declaration? It's only barely more useful than > omitting a type declaration at all; type declarations are supposed to > prevent you needing to check. On the other hand, if the two classes share > some methods, then either there's an interface you can already use here, or > you can create one. Either way, you don't need a union type.
+1 I agree. Language like Golang use interface to intersect the method calls, I think that's better. > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: http://www.php.net/unsub.php > > -- Sent from Gmail Mobile
