String.replace_leading leads to infinite recursion

[nroi]

String.replace_leading("foo", "", "")

should return "foo", but instead it runs forever.
Tested with elixir version 1.3. and Erlang version 19.0.

[whatyouhide]

Same happens for String.replace_trailing/3 btw.

[wobh]

Hah! Nice catch!

Looks like there's no null-case testing in either String.replace_leading/3 or the private function String.replace_leading/6. The latter could detect when prefix_size and suffix_size are both 0 and return the string. Likewise with String.replace_trailing/3.