Function compose_unit_embeds 

pub fn compose_unit_embeds(
    name: &str,
    unit_info: &BTreeMap<String, UnitInfo>,
) -> HashMap<String, EmbedDecl>

Every embed visible in unit name: its own, plus those of each commons it uses (one level, the same mixin rule crate::assets::compose_unit_assets applies to assets). A local declaration of any kind wins over an imported embed of the same name; two used commons declaring the same name is bynk.uses.name_conflict (phase_uses_name_conflicts), so which of them is kept here is never observable in a program that checks.