Function warn_ignored_hint_mostly_unused 

fn warn_ignored_hint_mostly_unused(
    gctx: &GlobalContext,
    profile: &Value<TomlProfile>,
    name: &str,
    warnings: &mut Vec<String>,
) -> CargoResult<()>

Warns about each hint-mostly-unused = true in a config profile, which is ignored without -Zprofile-hint-mostly-unused. Manifest profiles are covered by the parse pass instead, see crate::diagnostics::rules::PARSE_PASS_RULES.