; tcIfaceDataAlt con inst_tys arg_strs rhs }
tcIfaceAlt _ (tycon, inst_tys) (IfaceTupleAlt _boxity, arg_occs, rhs)
- = ASSERT( isTupleTyCon tycon )
+ = ASSERT2( isTupleTyCon tycon, ppr tycon )
do { let [data_con] = tyConDataCons tycon
; tcIfaceDataAlt data_con inst_tys arg_occs rhs }