I'm not convinced. Can the Rust function which is shown (that function alone) tokenize a number out of a string such that the number is overflowing the target type? Yet indicate to the caller where that overflowing number ends, so that tokenization can continue with subsequent characters, if any?

E.g. suppose we have a string with this kind of syntax:

   "12345 : 12345   , 12345"

We can

1. use strtol to get the first integer and a pointer to just after it.

2. use ptr += strspn(ptr, " ") to skip spaces

3. check for the colon and if we find it, skip with ptr++

4. use strtol to get the second integer (possibly preceded by space).

5. similarly to the colon handling, do the comma

6. strtol again to get the integer.

This is efficient: no splitting of the string into pieces requiring memory allocation, and extra list processing.

We can code this robustly: it can recognize valid syntax even if some of the numbers overflow. So for this kind of input:

    "1234523442345345345234534545454545 : 12345  12345" 

the code could diagnose the overflow, and the missing comma in one pass.

If you don't care about the details, just "is this number in range, with no trailing junk, or else is it bad", then raw strtol isn't convenient. But takes only a little code to wrap it.