[swift-evolution] [Pitch] Introduce user-defined dynamically "callable" types

[Chris Lattner]

> On Nov 11, 2017, at 10:33 AM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> The discussion phase in the previous thread considered several approaches, including burning python specific support in, implementing a python importer, and implementing a single “dynamic thing” protocol.  These are all bad ideas for reasons described in the thread.  If you’re curious, I’m happy to elaborate in alternatives considered.
> 
> As such, discussion converged on pitching two proposals, which are generally useful beyond this niche:
> 
> 1. The dynamically callable one already written.
> 2. A dynamically member lookupable proposal to sugar things like foo.get(member: “bar”) - and the corresponding setter.
> 

One other pertinent thing from the discussion thread: it seriously isn’t lost on me how the Swift type checker works.  One of the the alternate designs that I intend to explore is to add a second method to the protocol, to encapsulate the Swift member dispatch idiom:

  func dynamicCallMember(member: String, arguments: [(String, DynamicCallableArgument)]) throws ->
 DynamicCallableResult


This puts more effort onto the implementer of the protocol, but I think that is a totally acceptable tradeoff to save compiler complexity.

-Chris

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20171111/244a6041/attachment.html>