The parameters for a fixed-size array type determine the type's size/stride, so 
how could the bounds not be needed during compile-time? The compiler can't 
layout objects otherwise. 

Or do you mean that the bounds are integer literals? (That's what I have in the 
design document now.)

Sent from my iPhone

On Jul 30, 2017, at 8:51 PM, John McCall <[email protected]> wrote:

>> On Jul 29, 2017, at 7:01 PM, Daryle Walker via swift-evolution 
>> <[email protected]> wrote:
>> The “constexpr” facility from C++ allows users to define constants and 
>> functions that are determined and usable at compile-time, for compile-time 
>> constructs but still usable at run-time. The facility is a key step for 
>> value-based generic parameters (and fixed-size arrays if you don’t want to 
>> be stuck with integer literals for bounds). Can figuring out Swift’s story 
>> here be part of Swift 5?
> 
> Note that there's no particular reason that value-based generic parameters, 
> including fixed-size arrays, actually need to be constant expressions in 
> Swift.
> 
> John.
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