Function query_ensure 

pub(crate) fn query_ensure<'tcx, Cache>(
    tcx: TyCtxt<'tcx>,
    execute_query: fn(TyCtxt<'tcx>, Span, Cache::Key, QueryMode) -> Option<Cache::Value>,
    query_cache: &Cache,
    key: Cache::Key,
    check_cache: bool,
)
where
    Cache: QueryCache,

Shared implementation of tcx.ensure_ok().$query(..) for most queries, and tcx.ensure_done().$query(..) for all queries.