[swift-evolution] URL Literals

[David Sweeris]

> On Dec 19, 2016, at 11:48 AM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
> 
> On Mon, Dec 19, 2016 at 1:44 PM, David Sweeris via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> On Dec 19, 2016, at 11:36 AM, David Sweeris via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> 
>>> On Dec 19, 2016, at 11:21 AM, Erica Sadun via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> ```swift
>>> let x = #imageLiteral(resourceName:"nothere.jpg")
>>> print(x)
>>> ```
>>> 
>>> This compiles. It crashes at runtime. I don't see why URLs should be any different.
>>> 
>>> — E
>> 
>> They shouldn’t be. The print function can already handle things that aren’t `CustomStringConvertible`:
>> struct Foo {}
>> let x = Foo()
>> Foo.self is CustomStringConvertible //says `false`
>> print(x) //says `"Foo()\n"`
>> so, IMHO, that’s a bug.
> 
> Oh, hey, wait a second… I didn’t catch the meaning of the resource name, and thought you meant it was crashing on the print statement. I still think it’s a bug, because the compiler should be able to check if the resource exists.
> 
> I think the point here is that what exists at compile time may not exist at runtime and vice versa, so while a warning might be elegant, it's not helpful for the compiler to refuse to proceed on the basis that the image does not yet exist. At the end of the day, an image literal hardcodes the path to an image, not the image itself. Whether it ought to is another kettle of fish.

Ah, ok, I didn’t realize that image literals weren’t actually created until runtime... In that case, I retract my statement that they shouldn't be any different, because they while they both may be called “literals", they use that word to mean to two quite different things.

- Dave Sweeris

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