Reified Type Parameters Using Java']Java Annotations

Java generics are compiled by-erasure: all clients reuse the same bytecode, with uses of the unknown type erased. C++ templates are compiled by-expansion: each type-instantiation of a template pro- duces a different code definition. The two approaches offer trade- offs on multiple axes. We propose an extension of Java generics that allows by-expansion translation relative to selected type pa- rameters only. This language design allows sophisticated users to get the best of both worlds at a fine granularity. Furthermore, our proposal is based on Java 8 Type Annotations (JSR 308) and the Checker Framework as an abstraction layer for controlling compi- lation without changes to the internals of a Java compiler.