[swift-evolution] [Proposal] Change guarantee for GeneratorType.next() to always return nil past end
kevin at sb.org
Tue Mar 8 20:29:01 CST 2016
One minor change to what I've been proposing: Instead of merely saying that it's implementation-defined, we should expressly say that invoking next() after it has previously returned nil may return nil or it may return an implementation-defined value, but it should not fatalError() (unless some other GeneratorType requirement has been violated). Which is to say, after a GeneratorType has returned nil from next(), it should always be safe to invoke next() again, it's just up to the particular implementation to determine what value I get by doing that.
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