where
is_local_id = isJust mb_poly_rhs
poly_rhs | Just rhs <- mb_poly_rhs
- = rhs
- | Just unfolding <- maybeUnfoldingTemplate (idUnfolding poly_id)
- = unfolding
+ = rhs -- Local Id; this is its rhs
+ | Just unfolding <- maybeUnfoldingTemplate (realIdUnfolding poly_id)
+ = unfolding -- Imported Id; this is its unfolding
+ -- Use realIdUnfolding so we get the unfolding
+ -- even when it is a loop breaker.
+ -- We want to specialise recursive functions!
| otherwise = pprPanic "dsImpSpecs" (ppr poly_id)
- -- In the Nothing case the specialisation is for an imported Id
- -- whose unfolding gives the RHS to be specialised
- -- The type checker has checked that it has an unfolding
+ -- The type checker has checked that it *has* an unfolding
specUnfolding :: (CoreExpr -> CoreExpr) -> Type
-> Unfolding -> DsM (Unfolding, OrdList (Id,CoreExpr))