swift

d75a62ce - SIL: Enclose switch subjects in a new begin_borrow [fixed] variant.

SIL: Enclose switch subjects in a new begin_borrow [fixed] variant. We want to preserve the borrow scope during switch dispatch so that move-only checking doesn't try to analyze destructures or consumes out of it. SILGen should mark anywhere that's a potential possibility with its own marker so that it gets borrow checked independently.