Function feast::core::one_if

pub fn one_if<'p, P, F>(
    predictate: F, 
    description: &'static str
) -> impl Fn(P) -> PassResult<'p, P, PassToken<'p, P>> where
    P: Pass<'p>,
    F: Fn(PassToken<'p, P>) -> Result<PassToken<'p, P>, PassToken<'p, P>>,