swift234

IR generation for DynamicSelf method invocations on existentials.

When projecting an existential into an opened archetype, bind the
archetype with metadata and witness tables extracted from the
existential. Tweak SILGen so that it doesn't destroy the opened
archetype value an extra two times.

Use an executable testcase to ensure end-to-end operation, because we
still don't have a parsable form existential projection to opened
archetype instructions.



Swift SVN r13755