[swift-dev] [SE-0143] Dynamic casting for conditional conformances

[Douglas Gregor]

> On Dec 10, 2017, at 4:47 PM, Brent Royal-Gordon <brent at architechies.com> wrote:
> 
>> On Dec 5, 2017, at 2:28 PM, Douglas Gregor via swift-dev <swift-dev at swift.org <mailto:swift-dev at swift.org>> wrote:
>> 
>> To perform that mapping from a mangled type in a conditional requirement to type metadata, we effectively need an operation to take a mangled type name and turn it into a type metadata pointer. This is something we could surface in the Swift standard library/runtime as, e.g.,
>> 
>> func type(named: String) -> Any.Type?
>> 
>> to take a mangled type name and try to get the type metadata for it. From there, one can query protocol conformances that (say) allow one to construct instances of the arbitrarily-named type. Think of it as NSClassFromString for any type in the Swift language, including specializations of generic types.
> 
> 
> It's worth noting here that the standard library already provides a limited `_typeByName(_:)` function for Corelibs Foundation to use. That function will presumably become part of the ABI unless we design a public version in Swift 5.


Woah. That’s kinda awful… it parses “Foo.Bar” as a class name and looks for class Bar in module Foo.

	- Doug

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