Reject non-integer arguments in Integer.extended_gcd/2 zero clauses

[pnezis]

The zero base-case clauses guarded only on comparison with 0, so under Erlang term ordering non-integer arguments (floats, atoms) matched when the other argument was 0, e.g. Integer.extended_gcd(2.5, 0) returned {2.5, 1, 0} instead of raising, violating the spec and diverging from Integer.gcd/2.

iex(1)> Integer.extended_gcd(:atom, 0)
{:atom, 1, 0}
iex(2)> Integer.extended_gcd(2.5, 0)
{2.5, 1, 0}
iex(3)> Integer.extended_gcd(-2.5, 0)
{-2.5, 1, 0}
iex(4)> Integer.extended_gcd(0, -1.2)
{-1.2, 0, 1}

I am evaluating claude fable on code review tasks and this was one of the findings - more to follow

[josevalim]

💚 💙 💜 💛 ❤️