-- no thunks involved at all.
--
-- It's called (i) in TidyPgm.hasCafRefs to decide if the rhs is, or
--- refers to, CAFs; and (ii) in CoreToStg to decide whether to put an
--- update flag on it.
+-- refers to, CAFs; (ii) in CoreToStg to decide whether to put an
+-- update flag on it and (iii) in DsExpr to decide how to expand
+-- list literals
--
-- The basic idea is that rhsIsStatic returns True only if the RHS is
-- (a) a value lambda