Auto protocol conformance if Key Path Member Lookup meets protocol requirement

[xwu (Xiaodi Wu)]

Introduce “Dynamic Member” fulfillment of Protocols

FWIW, just explaining thought process here: This was suggested and I specifically considered this and pushed back on this during the review process. The entire point of the dynamic member lookup feature is to allow unbound syntactic extension of a member lookup in the case when the author of a type cannot enumerate all of the members that a user might want to use statically. In the case of protocol conformance, a protocol does have a specific static list of members that need to be satisfied. …