Macro immut2 

macro_rules! immut2 {
    ($f:expr ; else $else:expr) => { ... };
    ($f:expr) => { ... };
}

Macro to wrap a FnMut with 2 arguments into a Fn.

This can wrap any FnMut with two arguments.

See immut1! and immut3! to support a different number of arguments.

Note

If this function tries to call itself recursively (for example by triggering an event in Cursive), the second call will be a no-op. Enabling recursive calls would break the FnMut contract.

In addition, due to weird interaction between Higher-rank trait bounds and closures, you should use the result from the macro directly, and not assign it to a variable.