lookupSimpleInst (LitInst { tci_lit = lit@OverLit { ol_val = lit_val
, ol_rebindable = rebindable }
, tci_ty = ty, tci_loc = iloc})
-#ifdef DEBUG
- | rebindable = panic "lookupSimpleInst" -- A LitInst invariant
-#endif
+ | debugIsOn && rebindable = panic "lookupSimpleInst" -- A LitInst invariant
| Just witness <- shortCutLit lit_val ty
= do { let lit' = lit { ol_witness = witness, ol_type = ty }
; return (GenInst [] (L loc (HsOverLit lit'))) }