[swift-dev] Emitting redundant protocol conformances to support type lookup

[Joe Groff]

> On Jan 12, 2016, at 7:46 PM, Luke Howard via swift-dev <swift-dev at swift.org> wrote:
> 
> Would it be possible to extend GenericParameterDescriptor to include a tail-emplaced set of references to ProtocolDescriptors for any parameter type constraints that require witness tables? This would be useful plumbing for a future API that can dynamically instantiate generic types.
> 
> See:
> 
> https://github.com/lhoward/swift/blob/SR-381/include/swift/Runtime/Metadata.h#L1199 <https://github.com/lhoward/swift/blob/SR-381/include/swift/Runtime/Metadata.h#L1199>
> 
> https://github.com/lhoward/swift/blob/SR-381/stdlib/public/runtime/MetadataLookup.cpp#L338 <https://github.com/lhoward/swift/blob/SR-381/stdlib/public/runtime/MetadataLookup.cpp#L338>
That's something to consider. However, we will be systematically revamping these metadata structures soon, so I don't think there's much benefit to incrementally changing what we have.

-Joe

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