[swift-evolution] [Planning][Request] "constexpr" for Swift 5

[John McCall]

> On Jul 29, 2017, at 7:01 PM, Daryle Walker via swift-evolution <swift-evolution at swift.org> 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.