“functions should be simple enough to not be coded incorrectly”
That’s a cool postulate, one which can indeed revolutionize programming!
All one needs to ensure no errors at run time is a compile-time tool which will fail to compile if your function is not simple and short enough — and then it becomes automatically correct by definition, because it’s impossible to code such function incorrectly.
It also means you are a dream developer, having found this formula. Since you write functions “simple enough to not be coded incorrectly”, you have have never had a bug in your code, and never will.
Wait, that time when QA/integration testers found you had a bug, was it because you didn’t write a “simple enough” function?
Or is that you have bugs even though you write “simple enough” functions, because having a simple function is not the same as having a correct function?
Let me just presume that your code has bugs and you are talking nonsense.