I think I mostly agree. When TCE isn’t guaranteed, it seems pretty bad to have code that runs fine in one engine but blows up the stack in another. When it is guaranteed it’s still hard because modifications to code may break TCE and so as well as knowing what those things are (eg wrapping in a try block), you need to be careful about every change that breaks TCE to make sure that the code isn’t relying on TCE. Also I think JS might have extra problems due to eg arguments.caller.
In languages which do have guaranteed TCE like scheme or ML variants, I think I would rather see some way to explicitly say “this is a tail call which should be eliminated” or “all recursive calls to this function should be tail calls” and then have the compiler complain if you have a call which should be eliminated but isn’t in tail position. I think the reason for clojure not doing TCE is that, in general[1], it is a global optimisation (not possible by simple syntax transformation) that the jvm doesn’t do. So clojure didn’t really have a choice in whether or not to have TCE.
[1] it is more possible to transform recursive or mutually recursive code into iterative code, but the latter becomes hard in the face of a dynamic language where functions can be redefined and impossible to do locally for all tail calls.
In languages which do have guaranteed TCE like scheme or ML variants, I think I would rather see some way to explicitly say “this is a tail call which should be eliminated” or “all recursive calls to this function should be tail calls” and then have the compiler complain if you have a call which should be eliminated but isn’t in tail position. I think the reason for clojure not doing TCE is that, in general[1], it is a global optimisation (not possible by simple syntax transformation) that the jvm doesn’t do. So clojure didn’t really have a choice in whether or not to have TCE.
[1] it is more possible to transform recursive or mutually recursive code into iterative code, but the latter becomes hard in the face of a dynamic language where functions can be redefined and impossible to do locally for all tail calls.