Recur relies on AST rewriting to turn self-recursion into a loop. The JVM doesn't play a part in this. My impression is that this is 50/50 language design (recu

Recur relies on AST rewriting to turn self-recursion into a loop. The JVM doesn't play a part in this. My impression is that this is 50/50 language design (recur throws errors on non-tail calls) and compromise for the JVM as a platform. OCaml on the JVM would have the same problems, if not worse. Eliminating tail recursion is essential in the ML family, and doing that while sanely supporting Java interop seems to be difficult. I don't really keep up with it much, but I remember proposals to give some bytecode operations that would help here in the next Java version. Not sure if any of them made it past that stage.