Type qualifiers offer a lightweight mechanism for enriching existing type systems to enforce additional, desirable, program invariants. They do so by offering a restricted but effective form of subtyping. While the theory of type qualifiers is well understood and present in many programming languages today, polymorphism over type qualifiers remains an area less well examined. We explore how such a polymorphic system could arise by constructing a calculus, System F-sub-Q, which combines the higher-rank bounded polymorphism of System F-sub with the theory of type qualifiers. We explore how the ideas used to construct System F-sub-Q can be reused in situations where type qualifiers naturally arise---in reference immutability, function colouring, and capture checking. Finally, we re-examine other qualifier systems in the literature in light of the observations presented while developing System F-sub-Q.

Parametric polymorphism enables programmers to express algorithms independently of the types of values that they operate on. The approach used to implement parametric polymorphism can have important performance implications. One popular approach, erasure, uses a uniform representation for generic data, which entails primitive boxing and other indirections that harm performance. Erasure destroys type information that could be used by language implementations to optimize generic code. We present TASTyTruffle, an implementation for a subset of the Scala programming language. Instead of JVM bytecode, TASTyTruffle interprets Scala's TASTy intermediate representation, a typed representation wherein generic types are not erased. TASTy's precise type information empowers TASTyTruffle to implement generic code more effectively. In particular, it allows TASTyTruffle to reify types as run-time objects that can be passed around. Using reified types, TASTyTruffle supports heterogeneous box-free representations for generic values. TASTyTruffle also uses reified types to specialize generic code, producing monomorphic copies of generic code that can be easily and reliably optimized by its just-in-time (JIT) compiler. Empirically, TASTyTruffle is competitive with standard JVM implementations on a small set of benchmark programs; when generic code is used with multiple types, TASTyTruffle consistently outperforms the JVM. The precise type information in TASTy enables TASTyTruffle to find additional optimization opportunities that could not be uncovered with erased JVM bytecode.

Top designers and design engineering managers will present this wish list to make their next (or even current) design a much better design experience. They will not focus on pie-in-the-sky research topics, but describe down-to-earth challenges that designers face in getting their designs out the door. The panelists will use their data and experiences to substantiate their wish lists and address the main question: What needs to change in the design flows and design tools to improve Time-to-Market (TTM) and design quality?