import FunDeps
import PrelInfo
import PrelNames
-import Type
import TysWiredIn
import ErrUtils
import BasicTypes
import FiniteMap
import Bag
import Outputable
-import Maybes
import ListSetOps
import Util
import SrcLoc
tcSimplifyRuleLhs :: [Inst] -> TcM ([Inst], TcDictBinds)
tcSimplifyRuleLhs wanteds
= do { wanteds' <- zonkInsts wanteds
- ; (irreds, binds) <- go [] emptyBag wanteds'
+
+ -- Simplify equalities
+ -- It's important to do this: Trac #3346 for example
+ ; (_, wanteds'', tybinds, binds1) <- tcReduceEqs [] wanteds'
+ ; execTcTyVarBinds tybinds
+
+ -- Simplify other constraints
+ ; (irreds, binds2) <- go [] emptyBag wanteds''
+
+ -- Report anything that is left
; let (dicts, bad_irreds) = partition isDict irreds
; traceTc (text "tcSimplifyrulelhs" <+> pprInsts bad_irreds)
; addNoInstanceErrs (nub bad_irreds)
-- The nub removes duplicates, which has
-- not happened otherwise (see notes above)
- ; return (dicts, binds) }
+
+ ; return (dicts, binds1 `unionBags` binds2) }
where
go :: [Inst] -> TcDictBinds -> [Inst] -> TcM ([Inst], TcDictBinds)
go irreds binds []
\begin{code}
tcSimplifyBracket :: [Inst] -> TcM ()
tcSimplifyBracket wanteds
- = do { tryHardCheckLoop doc wanteds
+ = do { _ <- tryHardCheckLoop doc wanteds
; return () }
where
doc = text "tcSimplifyBracket"
= do { mb_chosen_ty <- try_default default_tys
; case mb_chosen_ty of
Nothing -> return ()
- Just chosen_ty -> do { unifyType chosen_ty (mkTyVarTy tyvar)
+ Just chosen_ty -> do { _ <- unifyType chosen_ty (mkTyVarTy tyvar)
; warnDefault dicts chosen_ty } }
where
(_,_,tyvar) = ASSERT(not (null dicts)) head dicts -- Should be non-empty
(friends, others) = partition is_friend insts
loc_msg = showSDoc (pprInstLoc (instLoc inst))
is_friend friend = showSDoc (pprInstLoc (instLoc friend)) == loc_msg
- do_one insts = addInstCtxt (instLoc (head insts)) (report_err insts)
+ do_one insts = setInstCtxt (instLoc (head insts)) (report_err insts)
-- Add location and context information derived from the Insts
-- Add the "arising from..." part to a message about bunch of dicts
warnDefault :: [(Inst, Class, Var)] -> Type -> TcM ()
warnDefault ups default_ty = do
warn_flag <- doptM Opt_WarnTypeDefaults
- addInstCtxt (instLoc (head (dicts))) (warnTc warn_flag warn_msg)
+ setInstCtxt (instLoc (head (dicts))) (warnTc warn_flag warn_msg)
where
dicts = [d | (d,_,_) <- ups]