swift

56e38b33 - [SE-0470] Promote isolated-conformance-to-sendable-metatype protocol to error

[SE-0470] Promote isolated-conformance-to-sendable-metatype protocol to error Forming an isolated conformance to a SendableMetatype-inherting protocol opens up a soundness hole any time the conformance is used. Reword the recently-introduced diagnostic for this case and promote it to an error (except when it's preconcurrency). Fixes rdar://154808002.