Function record_inst_fields 

pub fn record_inst_fields(
    name: &str,
    args: &[TypeRef],
    types: &HashMap<String, Arc<TypeDecl>>,
) -> Option<Vec<(String, TypeRef)>>

v0.174 (#592): the concrete (field-name, field-type) list for a generic record instantiation Name[args…] — the declared fields with every type parameter substituted by the matching argument. Returns None if name is not a declared generic record or the arity does not match (both guaranteed impossible by the checker, so this is purely defensive).