Function lower_entry 

pub fn lower_entry(
    checked: &Program,
    sources: &SourceMap,
    schemas: &HostSchemas,
    module: &str,
    name: &str,
) -> Result<Program, Vec<Diagnostic>>

Lowers only the declarations module.name can reach.

The one-root case of lower_roots, which is where everything this does is written down. It has a name of its own because one root is what almost every caller has — cove run has the entry it was asked for, cove replay has the entry the tape was recorded from, cove test has the test it is about to run — and because a set of one is the only set whose gaps belong to a single root.