swift234

Bubble the covariant conversions to the outermost relevant call.

When applying a function that was produced via a covariant function
conversion, strip off that covariant function conversion and introduce
a covariant (function or return) conversion outside of the
application. This allows us to perform the covariant conversion very
late, eliminating the need to produce reabstraction thunks for any
call to a DynamicSelf method.


Swift SVN r13779