That's pretty hardcore, like you want to restrict the runtime substitution of function calls with their result values? Even Haskell doesn't go that far.
Generally you'd distinguish which function call introduces the error with the function call stack, which would include the location of each function's call-site, so maybe the "low-effort" label is accurate. But I could see a benefit in immediately knowing which functions are "pure" and "impure" in terms of manipulating non-local state. I don't think it changes any runtime behavior whatsoever, really, unless your runtime schedules function calls on an async queue and relies on the order in code for some reason.
It has been so long since I worked on the code that had chaining functions and caused problems that I am not sure I can do justice to describing the problems.
I vaguely remember the problem was one function returned a very structured array dealing with regex matches. But there was something wrong with the regex where once in a blue moon, it returned something odd.
So, the chained functions did not error. It just did something weird.
Whenever weird problems would pop up, it was always passed to me. And when I looked at it, I said, well...
I am going to rewrite this chain into steps and debug each return. Then run through many different scenarios and that was how I figured out the regex was not quite correct.
Generally you'd distinguish which function call introduces the error with the function call stack, which would include the location of each function's call-site, so maybe the "low-effort" label is accurate. But I could see a benefit in immediately knowing which functions are "pure" and "impure" in terms of manipulating non-local state. I don't think it changes any runtime behavior whatsoever, really, unless your runtime schedules function calls on an async queue and relies on the order in code for some reason.
My verdict is, "IDK", but worth investigating!