swift234

Fix rdar://problem/17584531 ("Crash in emitDynamicSubscript on access of multiple Foundation containers by subscript")

In buildSubscript, when forcing an implicitly unwrapped optional base expression of a subscript expression, we weren't updating the base type in for later use. In the case of a nested subscript expression, this could cause us to coerce to the wrong inner type.

Swift SVN r20736