`finish{Array,Dictionary}Expr` currently invoke `cs.cacheExprTypes` after building their semantic exprs, which in a nested collection expression, immediately undoes the type changes done by this peephole, leading to crashes due to inconsistencies in the AST later. rdar://problem/41040820
There are other parts of CSApply that attempt to peephole transform ArrayExprs (particularly bridging, which tries to turn `[x, y, ...] as T` into `[x as T, y as T, ...]`) and expect the elements to have already been rvalue-d. Fixes rdar://problem/40859007.
