it doesn't work in my program:
https://bitbucket.org/iopq/fizzbuzz-in-rust/src/bf4968973d73...
it gives an error when I use a generic `second` method from tool.rs
https://bitbucket.org/iopq/fizzbuzz-in-rust/src/bf4968973d73...
it gives an error when I use a generic `second` method from tool.rs
https://is.gd/Xnu0YJ