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).