The Starlark spec discusses this, and I consulted it before I wrote my comment. > It is a dynamic error for a function to call itself or another function value

The Starlark spec discusses this, and I consulted it before I wrote my comment. > It is a dynamic error for a function to call itself or another function value with the same declaration. > This rule, combined with the invariant that all loops are iterations over finite sequences, implies that Starlark programs are not Turing-complete. However, an implementation may allow clients to disable this check, allowing unbounded recursion. https://github.com/bazelbuild/starlark/blob/master/spec.md https://github.com/bazelbuild/starlark/blob/master/spec.md I do kind of agree with you about this, though: > At that point, just give your users a `while` loop for usability's sake. I'm generally in favor of powerful, purpose-built configuration languages, including Turing-complete ones. And the goal of assuring users that their programs will terminate at all is definitely aligned with a fuzzier goal, less formalizable, that their programs will terminate in a 'reasonable' period of time, whatever that means.