Fix Trac #959: a long-standing bug in instantiating otherwise-unbound type variables

[ghc-hetmet.git] / compiler / stgSyn / CoreToStg.lhs

diff --git a/compiler/stgSyn/CoreToStg.lhs b/compiler/stgSyn/CoreToStg.lhs
index b2d7257..b5484a4 100644 (file)
--- a/compiler/stgSyn/CoreToStg.lhs
+++ b/compiler/stgSyn/CoreToStg.lhs
@@ -437,7 +437,7 @@ mkStgAltType bndr alts
                    | isUnLiftedTyCon tc     -> PrimAlt tc
                    | isHiBootTyCon tc       -> look_for_better_tycon
                    | isAlgTyCon tc          -> AlgAlt tc
-                   | otherwise              -> ASSERT( _is_poly_alt_tycon tc )
+                   | otherwise              -> ASSERT2( _is_poly_alt_tycon tc, ppr tc )
                                                PolyAlt
        Nothing                              -> PolyAlt