Swift should support customizable nil behavior per class

Originator:heath.borders
Number:rdar://17930637 Date Originated:06-Aug-2014 08:45 AM
Status:Open Resolved:
Product:Developer Tools Product Version:n/a
Classification:Enhancement Reproducible:n/a
 
Summary:
Switch should allow a class to handle method calls on nil in a customizable way. For example, in objective-c, all methods on nil respond by returning a 0 of some kind. However, in Swift, the compiler should have enough information to know what type the nil should have, and the compiler could then redirect the nil call to a custom nil object. For example, a String's nil object could return a -1 startIndex when rangeOfString is called.

If no nil object is set, then the default nil behavior should occur.

Steps to Reproduce:
n/a

Expected Results:
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Actual Results:
n/a

Version:
n/a

Notes:
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Configuration:
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