Function check_module 

pub fn check_module(
    package: &PackageName,
    interfaces: &HashMap<Name, Interface>,
    source: &Module,
) -> Result<CheckedModule, CompilationError>

Take a parsed module file within the ecosystem and apply all checks to it

check_module_recovering, reduced to a module that either checked or did not: a module that came back with errors is Err with the first of them.