Function hlua::function3

pub fn function3<Z, R, A, B, C>(f: Z) -> Function<Z, (A, B, C), R> where
    Z: FnMut(A, B, C) -> R, 

Wraps a type that implements FnMut so that it can be used by hlua.

This is needed because of a limitation in Rust's inferrence system. Even though in practice functions and closures always have a fixed number of parameters, the FnMut trait of Rust was designed so that it allows calling the same closure with a varying number of parameters. The consequence however is that there is no way of inferring with the trait alone many parameters a function or closure expects.