swift234

[let-properties-opts] Don't remove assignments to let properties from initializers.

Let properties optimizations were removing assignments to let properties, which are private or internal and compiled with WMO. It seems to be safe, because all explicit reads of those properties were replaced by their compile-time constant values. But it turned out to be problematic if one uses Mirrors, because in this case, new values of a given type are constructed implicitly by dynamically invoking the initializer through introspection.

This fixes rdar://22725946

Swift SVN r32173