Example

fallible Fold

pub trait TryFold {
    type Error;

    fn try_fold_abi(&mut self, t: syn::Abi) -> Result<syn::Abi, Self::Error>
    {
        try_fold_abi(self, t)
    }

    // ...
}

fallible take (like fold but without return new value)

pub trait TryTake {
    type Error;

    fn try_take_abi(&mut self, t: syn::Abi) -> Result<(), Self::Error> {
        try_take_abi(self, t)
    }

    // ...
}