Macro try_get 

macro_rules! try_get {
    (fn($input:ident: &mut $ity:ty) -> Result<($oty:ty, $aty:ty), $ety:ty> { $($v:tt)+ }) => { ... };
    (fn<$a:lifetime>($input:ident: &mut $ity:ty) -> Result<($oty:ty, $aty:ty), $ety:ty> { $($v:tt)+ }) => { ... };
}

A macro for quickly implementing crate::TryGetFut without capturing.

If you need capturing, you will have to manually capture what you want in a user-defined struct and implement crate::TryGetFut for that struct.