swift234

Teach TypeChecker::conformsToProtocol() to identify protocol
conformance when it is trivial, e.g., when the source type is an
archetype or existential type that conforms to the candidate protocol
or a protocol that implies it. In this case, we don't build a
ProtocolConformance structure (which would be uninteresting anyway).

Extend the definition of ErasureExpr to allow for null entries in the
conformance mappings, when some of the conformance is trivial. IRgen
couldn't handle multi-protocol existential types anyway, so this
change has no impact there (yet).


Swift SVN r2212