Function canonicalize 

pub fn canonicalize(
    package: &PackageName,
    interfaces: &HashMap<Name, Interface>,
    source: &Module,
) -> Result<Module, Vec<Error>>

Transform a given parser::Module into a canonical::Module, or into the errors that kept it from being one.

canonicalize_recovering, reduced to all-or-nothing: a module that came back with errors is Err with all of them.