[swift-dev] Optional to String conversion

[Greg Parker]

> On Dec 4, 2015, at 10:00 PM, Andrew Trick <atrick at apple.com> wrote:
> 
> I’m adding runtime functionality to support optional casts and ran into some Optional to String conversion behavior that is currently somewhat accidental—it will break when I add functionality. I want to understand the desired behavior before doing extra work to fix it.
> 
> Currently swift does this:
> 
>> print(Int?(3))
> Optional(3)
>> print(String?("meow"))
> Optional("meow")
> 
> I think swift should do this:
> 
>> print(Int?(3))
> 3
>> print(String?("meow"))
> "meow"
>> debugPrint(Int?(3))
> Optional(3)
>> debugPrint(String?("meow"))
> Optional("meow")
> 
> When a value already knows how to represent itself as a string, I don't think that the string "Optional" belongs in the textual representation.

There are unfortunate output ambiguities if you don't include it.

Consider the output of all of these:

print(String?("test"))
print(String?("nil"))
print(String?.None)

The current output is unambiguous:

print(String?("test"))
    Optional("test")
print(String?("nil"))
    Optional("nil")
print(String?.None)
    nil


-- 
Greg Parker     gparker at apple.com     Runtime Wrangler