inlineness

[AndyShiue]

Make inlining functions and data types possible. Inlining a function has the usual meaning; inlining data types measn that the union type should not have a tag, having no runtime representation (That's why it's called inlining because inlining a functional also eliminate them at compile time). The variant actually in use must be known at compile time. Combining two different kinds of inlining should make erasing some unreachable code possible.