[swift-evolution] Proposal: Improve Import of Scanner APIs into Swift 3

Oliver Drobnik oliver at cocoanetics.com
Wed Nov 30 04:10:07 CST 2016

Working on a function for Foundation’s Scanner I stumbled on this LLVM crash: https://bugs.swift.org/browse/SR-3295

This got me thinking about a workaround and I would like to prose this:

When importing Foundation into Swift 3, all 


should instead be exposed as simple:

inout T?


open func scanString(_ string: String, into result: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool

would become

open func scanString(_ string: String, into result: inout String?) -> Bool

The call would stay exactly the same for normal use cases where you specify a receiving variable:

var string: String?
scanString("=", into: &string)

because inout parameters require a &

for the use case where you don’t require a receiving parameter, a second method without result parameter would be generated:

open func scanString(_ string: String) -> Bool

This is necessary because you cannot specify nil or an immutable value for an inout parameter. 

A fixit/migration would change calls to

scanString(“foo", into result: nil)



The normal call with receiving variable would stay the same. But the case without return would become more concise.

What do you think?

kind regards
Oliver Drobnik

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20161130/0ce5d929/attachment.html>

More information about the swift-evolution mailing list