Function try_get_cached 

fn try_get_cached<'tcx, C>(
    tcx: TyCtxt<'tcx>,
    cache: &C,
    key: &C::Key,
) -> Option<C::Value>
where
    C: QueryCache,

Checks whether there is already a value for this key in the in-memory query cache, returning that value if present.

(Also performs some associated bookkeeping, if a value was found.)