Spend some time with a language that not only supports them but actually encourages their use, and you will see for yourself. This isn't an example and does no

Spend some time with a language that not only supports them but actually encourages their use, and you will see for yourself. This isn't an example and does nothing to convince me that it's actually useful. Your suggested application just hints at difficult debugging when a Car object can be a stealth Truck. Maybe it isn't actually difficult, but why is this actually better than subclassing? TCO allows programs to, in certain circumstances, reuse existing stack frames for possibly many function invocations. For example, if a function is written to be tail recursive, a VM with TCO could reuse the same stack frame for each recursive function invocation until the terminating condition is reached, at which point the last return value is caught and the frame is popped off the stack. (TCO isn't strictly limited to making tail recursion more efficient, but that is its most often cited benefit.) Sounds like a loop.