Tuples conform to Equatable

[xwu (Xiaodi Wu)]

@Alejandro

Correct, nobody can currently write an Equatable conformance for some tuple type, and yes, there is no semantic difference. If this is accepted, all clients who currently use == for tuples that compile against this new compiler + runtime will reference the Equatable implementation vs. using the stdlib == for tuples. That's it, just some machinery in the background working.

Question—if this is accepted, and a resilient library makes use of magically generated tuple equality, will it be an ABI-breaking change in a future version of Swift to implement a custom conformance when it becomes possible to do so?