At compile time, what is the return type of foo? Answer: Unknown. The compiler has no way of determining if the resulting type will be small or big int. This has to be taken into account not just in foo, but in every function calling foo, and every function that is called with the return of foo as a param.
One of the best things about golang, is how little "magic" there is. Everything that happens is immediately obvious from the code. An int that is upgraded to a completely different type when it reaches certain values, goes directly counter to that; it would be hidden behaviour, not immediately obvious from the code.
Should golang have a builtin arbitrary sized integer type? Maybe. Using math/big can become cumbersome. But a much better solution would be to introduce a new builtin type like `num`
One of the best things about golang, is how little "magic" there is. Everything that happens is immediately obvious from the code. An int that is upgraded to a completely different type when it reaches certain values, goes directly counter to that; it would be hidden behaviour, not immediately obvious from the code.
Should golang have a builtin arbitrary sized integer type? Maybe. Using math/big can become cumbersome. But a much better solution would be to introduce a new builtin type like `num`