Macro rusticata_macros::upgrade_error

macro_rules! upgrade_error {
    ($i:expr, $submac:ident!( $($args:tt)*) ) => { ... };
    ($i:expr, $f:expr) => { ... };
    ($e:expr) => { ... };
}

Apply combinator, trying to "upgrade" error to next error type (using the Into or From traits).