58     pub optional: bool,  field
75         !self.optional || features.contains(&format!("dep:{}", name))  in enabled()
320         if dependency.optional && !package_features.contains_key(&dependency.name) {  in resolve_features()
427                 optional: true,  in resolve_dep_features()
434                 optional: true,  in resolve_dep_features()
441                 optional: false,  in resolve_dep_features()
460                     optional: false,  in get_externs_cfg()
467                     optional: false,  in get_externs_cfg()
474                     optional: false,  in get_externs_cfg()
538                     optional: false,  in get_externs_extra_cfg()
545                     optional: false,  in get_externs_extra_cfg()
593                     optional: false,  in get_externs_rename()
600                     optional: true,  in get_externs_rename()
607                     optional: true,  in get_externs_rename()