import VarSet
import PrelNames
import SrcLoc
-import Unique
import UniqSupply
import Util
import ListSetOps
-- Generate the generic Representable0/1 instances from each type declaration
; repInstsMeta <- genGenericRepBinds is_boot tycl_decls
- ; let repInsts = concat (map (\(a,b,c) -> a) repInstsMeta)
- repMetaTys = map (\(a,b,c) -> b) repInstsMeta
- repTyCons = map (\(a,b,c) -> c) repInstsMeta
+ ; let repInsts = concat (map (\(a,_,_) -> a) repInstsMeta)
+ repMetaTys = map (\(_,b,_) -> b) repInstsMeta
+ repTyCons = map (\(_,_,c) -> c) repInstsMeta
-- Should we extendLocalInstEnv with repInsts?
; (inst_info, rn_binds, rn_dus) <- renameDeriv is_boot gen_binds (insts1 ++ insts2 ++ repInsts)
clas_nm = className clas
-----------------------------------------
+{- Now unused
mkGenericBinds :: Bool -> [LTyClDecl Name] -> TcM (LHsBinds RdrName)
mkGenericBinds is_boot tycl_decls
| is_boot
-- We are only interested in the data type declarations,
-- and then only in the ones whose 'has-generics' flag is on
-- The predicate tyConHasGenerics finds both of these
+-}
\end{code}
Note [Newtype deriving and unused constructors]
gen_soln (DS { ds_loc = loc, ds_orig = orig, ds_tvs = tyvars
, ds_cls = clas, ds_tys = inst_tys, ds_theta = deriv_rhs })
= setSrcSpan loc $
- addErrCtxt (derivInstCtxt clas inst_tys) $
+ addErrCtxt (derivInstCtxt the_pred) $
do { -- Check for a bizarre corner case, when the derived instance decl should
-- have form instance C a b => D (T a) where ...
-- Note that 'b' isn't a parameter of T. This gives rise to all sorts
, not (tyVarsOfPred pred `subVarSet` tv_set)]
; mapM_ (addErrTc . badDerivedPred) weird_preds
- ; theta <- simplifyDeriv orig tyvars deriv_rhs
+ ; theta <- simplifyDeriv orig the_pred tyvars deriv_rhs
-- checkValidInstance tyvars theta clas inst_tys
-- Not necessary; see Note [Exotic derived instance contexts]
-- in TcSimplify
-- Hence no need to call:
-- checkValidInstance tyvars theta clas inst_tys
; return (sortLe (<=) theta) } -- Canonicalise before returning the solution
+ where
+ the_pred = mkClassPred clas inst_tys
------------------------------------------------------------------
mkInstance :: OverlapFlag -> ThetaType -> DerivSpec -> Instance
, isDataDecl d ]
let tyDecls = filter tyConHasGenerics allTyDecls
inst1 <- mapM genGenericRepBind tyDecls
- let (repInsts, metaTyCons, repTys) = unzip3 inst1
+ let (_repInsts, metaTyCons, _repTys) = unzip3 inst1
metaInsts <- ASSERT (length tyDecls == length metaTyCons)
mapM genDtMeta (zip tyDecls metaTyCons)
return (ASSERT (length inst1 == length metaInsts)
standaloneCtxt ty = hang (ptext (sLit "In the stand-alone deriving instance for"))
2 (quotes (ppr ty))
-derivInstCtxt :: Class -> [Type] -> Message
-derivInstCtxt clas inst_tys
- = ptext (sLit "When deriving the instance for") <+> parens (pprClassPred clas inst_tys)
+derivInstCtxt :: PredType -> Message
+derivInstCtxt pred
+ = ptext (sLit "When deriving the instance for") <+> parens (ppr pred)
badDerivedPred :: PredType -> Message
badDerivedPred pred