Commit 57217f68 authored by simonpj@microsoft.com's avatar simonpj@microsoft.com

Improve error reporting for precedence errors

Adopt the suggestion of Trac #2993, and tidy up the reporting of
precedence parsing errors somewhat.
parent 1c15bee5
......@@ -23,7 +23,7 @@ import RnEnv
import TcRnMonad
import RdrName
import PrelNames
import TypeRep ( funTyCon )
import TypeRep ( funTyConName )
import Name
import SrcLoc
import NameSet
......@@ -32,6 +32,7 @@ import BasicTypes ( compareFixity, funTyFixity, negateFixity,
Fixity(..), FixityDirection(..) )
import Outputable
import FastString
import Control.Monad ( unless )
#include "HsVersions.h"
\end{code}
......@@ -116,7 +117,7 @@ rnHsType doc ty@(HsOpTy ty1 (L loc op) ty2)
; fix <- lookupTyFixityRn l_op'
; ty1' <- rnLHsType doc ty1
; ty2' <- rnLHsType doc ty2
; mkHsOpTyRn (\t1 t2 -> HsOpTy t1 l_op' t2) (ppr op') fix ty1' ty2' }
; mkHsOpTyRn (\t1 t2 -> HsOpTy t1 l_op' t2) op' fix ty1' ty2' }
rnHsType doc (HsParTy ty) = do
ty' <- rnLHsType doc ty
......@@ -141,7 +142,7 @@ rnHsType doc (HsFunTy ty1 ty2) = do
-- when we find return :: forall m. Monad m -> forall a. a -> m a
-- Check for fixity rearrangements
mkHsOpTyRn HsFunTy (ppr funTyCon) funTyFixity ty1' ty2'
mkHsOpTyRn HsFunTy funTyConName funTyFixity ty1' ty2'
rnHsType doc (HsListTy ty) = do
ty' <- rnLHsType doc ty
......@@ -270,36 +271,35 @@ by the presence of ->, which is a separate syntactic construct.
---------------
-- Building (ty1 `op1` (ty21 `op2` ty22))
mkHsOpTyRn :: (LHsType Name -> LHsType Name -> HsType Name)
-> SDoc -> Fixity -> LHsType Name -> LHsType Name
-> Name -> Fixity -> LHsType Name -> LHsType Name
-> RnM (HsType Name)
mkHsOpTyRn mk1 pp_op1 fix1 ty1 (L loc2 (HsOpTy ty21 op2 ty22))
= do { fix2 <- lookupTyFixityRn op2
; mk_hs_op_ty mk1 pp_op1 fix1 ty1
(\t1 t2 -> HsOpTy t1 op2 t2)
(ppr op2) fix2 ty21 ty22 loc2 }
(unLoc op2) fix2 ty21 ty22 loc2 }
mkHsOpTyRn mk1 pp_op1 fix1 ty1 (L loc2 (HsFunTy ty21 ty22))
= mk_hs_op_ty mk1 pp_op1 fix1 ty1
HsFunTy (ppr funTyCon) funTyFixity ty21 ty22 loc2
HsFunTy funTyConName funTyFixity ty21 ty22 loc2
mkHsOpTyRn mk1 _ _ ty1 ty2 -- Default case, no rearrangment
= return (mk1 ty1 ty2)
---------------
mk_hs_op_ty :: (LHsType Name -> LHsType Name -> HsType Name)
-> SDoc -> Fixity -> LHsType Name
-> Name -> Fixity -> LHsType Name
-> (LHsType Name -> LHsType Name -> HsType Name)
-> SDoc -> Fixity -> LHsType Name -> LHsType Name -> SrcSpan
-> Name -> Fixity -> LHsType Name -> LHsType Name -> SrcSpan
-> RnM (HsType Name)
mk_hs_op_ty mk1 pp_op1 fix1 ty1
mk2 pp_op2 fix2 ty21 ty22 loc2
| nofix_error = do { addErr (precParseErr (quotes pp_op1,fix1)
(quotes pp_op2,fix2))
mk_hs_op_ty mk1 op1 fix1 ty1
mk2 op2 fix2 ty21 ty22 loc2
| nofix_error = do { precParseErr (op1,fix1) (op2,fix2)
; return (mk1 ty1 (L loc2 (mk2 ty21 ty22))) }
| associate_right = return (mk1 ty1 (L loc2 (mk2 ty21 ty22)))
| otherwise = do { -- Rearrange to ((ty1 `op1` ty21) `op2` ty22)
new_ty <- mkHsOpTyRn mk1 pp_op1 fix1 ty1 ty21
new_ty <- mkHsOpTyRn mk1 op1 fix1 ty1 ty21
; return (mk2 (noLoc new_ty) ty22) }
where
(nofix_error, associate_right) = compareFixity fix1 fix2
......@@ -314,9 +314,9 @@ mkOpAppRn :: LHsExpr Name -- Left operand; already rearranged
-- (e11 `op1` e12) `op2` e2
mkOpAppRn e1@(L _ (OpApp e11 op1 fix1 e12)) op2 fix2 e2
| nofix_error = do
addErr (precParseErr (ppr_op op1,fix1) (ppr_op op2,fix2))
return (OpApp e1 op2 fix2 e2)
| nofix_error
= do precParseErr (get_op op1,fix1) (get_op op2,fix2)
return (OpApp e1 op2 fix2 e2)
| associate_right = do
new_e <- mkOpAppRn e12 op2 fix2 e2
......@@ -328,13 +328,13 @@ mkOpAppRn e1@(L _ (OpApp e11 op1 fix1 e12)) op2 fix2 e2
---------------------------
-- (- neg_arg) `op` e2
mkOpAppRn e1@(L _ (NegApp neg_arg neg_name)) op2 fix2 e2
| nofix_error = do
addErr (precParseErr (pp_prefix_minus,negateFixity) (ppr_op op2,fix2))
return (OpApp e1 op2 fix2 e2)
| nofix_error
= do precParseErr (negateName,negateFixity) (get_op op2,fix2)
return (OpApp e1 op2 fix2 e2)
| associate_right = do
new_e <- mkOpAppRn neg_arg op2 fix2 e2
return (NegApp (L loc' new_e) neg_name)
| associate_right
= do new_e <- mkOpAppRn neg_arg op2 fix2 e2
return (NegApp (L loc' new_e) neg_name)
where
loc' = combineLocs neg_arg e2
(nofix_error, associate_right) = compareFixity negateFixity fix2
......@@ -342,9 +342,9 @@ mkOpAppRn e1@(L _ (NegApp neg_arg neg_name)) op2 fix2 e2
---------------------------
-- e1 `op` - neg_arg
mkOpAppRn e1 op1 fix1 e2@(L _ (NegApp _ _)) -- NegApp can occur on the right
| not associate_right= do -- We *want* right association
addErr (precParseErr (ppr_op op1, fix1) (pp_prefix_minus, negateFixity))
return (OpApp e1 op1 fix1 e2)
| not associate_right -- We *want* right association
= do precParseErr (get_op op1, fix1) (negateName, negateFixity)
return (OpApp e1 op1 fix1 e2)
where
(_, associate_right) = compareFixity fix1 negateFixity
......@@ -356,6 +356,11 @@ mkOpAppRn e1 op fix e2 -- Default case, no rearrangment
)
return (OpApp e1 op fix e2)
----------------------------
get_op :: LHsExpr Name -> Name
get_op (L _ (HsVar n)) = n
get_op other = pprPanic "get_op" (ppr other)
-- Parser left-associates everything, but
-- derived instances may have correctly-associated things to
-- in the right operarand. So we just check that the right operand is OK
......@@ -387,14 +392,14 @@ mkOpFormRn :: LHsCmdTop Name -- Left operand; already rearranged
-- (e11 `op1` e12) `op2` e2
mkOpFormRn a1@(L loc (HsCmdTop (L _ (HsArrForm op1 (Just fix1) [a11,a12])) _ _ _))
op2 fix2 a2
| nofix_error = do
addErr (precParseErr (ppr_op op1,fix1) (ppr_op op2,fix2))
return (HsArrForm op2 (Just fix2) [a1, a2])
| associate_right = do
new_c <- mkOpFormRn a12 op2 fix2 a2
return (HsArrForm op1 (Just fix1)
[a11, L loc (HsCmdTop (L loc new_c) [] placeHolderType [])])
| nofix_error
= do precParseErr (get_op op1,fix1) (get_op op2,fix2)
return (HsArrForm op2 (Just fix2) [a1, a2])
| associate_right
= do new_c <- mkOpFormRn a12 op2 fix2 a2
return (HsArrForm op1 (Just fix1)
[a11, L loc (HsCmdTop (L loc new_c) [] placeHolderType [])])
-- TODO: locs are wrong
where
(nofix_error, associate_right) = compareFixity fix1 fix2
......@@ -413,7 +418,7 @@ mkConOpPatRn op2 fix2 p1@(L loc (ConPatIn op1 (InfixCon p11 p12))) p2
; let (nofix_error, associate_right) = compareFixity fix1 fix2
; if nofix_error then do
{ addErr (precParseErr (ppr_op op1,fix1) (ppr_op op2,fix2))
{ precParseErr (unLoc op1,fix1) (unLoc op2,fix2)
; return (ConPatIn op2 (InfixCon p1 p2)) }
else if associate_right then do
......@@ -462,11 +467,10 @@ checkPrec op (ConPatIn op1 (InfixCon _ _)) right = do
(op1_dir == InfixR && op_dir == InfixR && right ||
op1_dir == InfixL && op_dir == InfixL && not right))
info = (ppr_op op, op_fix)
info1 = (ppr_op op1, op1_fix)
info = (op, op_fix)
info1 = (unLoc op1, op1_fix)
(infol, infor) = if right then (info, info1) else (info1, info)
checkErr inf_ok (precParseErr infol infor)
unless inf_ok (precParseErr infol infor)
checkPrec _ _ _
= return ()
......@@ -479,41 +483,47 @@ checkSectionPrec :: FixityDirection -> HsExpr RdrName
-> LHsExpr Name -> LHsExpr Name -> RnM ()
checkSectionPrec direction section op arg
= case unLoc arg of
OpApp _ op fix _ -> go_for_it (ppr_op op) fix
NegApp _ _ -> go_for_it pp_prefix_minus negateFixity
OpApp _ op fix _ -> go_for_it (get_op op) fix
NegApp _ _ -> go_for_it negateName negateFixity
_ -> return ()
where
L _ (HsVar op_name) = op
go_for_it pp_arg_op arg_fix@(Fixity arg_prec assoc) = do
op_name = get_op op
go_for_it arg_op arg_fix@(Fixity arg_prec assoc) = do
op_fix@(Fixity op_prec _) <- lookupFixityRn op_name
checkErr (op_prec < arg_prec
|| op_prec == arg_prec && direction == assoc)
(sectionPrecErr (ppr_op op_name, op_fix)
(pp_arg_op, arg_fix) section)
unless (op_prec < arg_prec
|| (op_prec == arg_prec && direction == assoc))
(sectionPrecErr (op_name, op_fix)
(arg_op, arg_fix) section)
\end{code}
Precedence-related error messages
\begin{code}
precParseErr :: (SDoc, Fixity) -> (SDoc, Fixity) -> SDoc
precParseErr op1 op2
= hang (ptext (sLit "precedence parsing error"))
precParseErr :: (Name, Fixity) -> (Name, Fixity) -> RnM ()
precParseErr op1@(n1,_) op2@(n2,_)
| isUnboundName n1 || isUnboundName n2
= return () -- Avoid error cascade
| otherwise
= addErr $ hang (ptext (sLit "Precedence parsing error"))
4 (hsep [ptext (sLit "cannot mix"), ppr_opfix op1, ptext (sLit "and"),
ppr_opfix op2,
ptext (sLit "in the same infix expression")])
sectionPrecErr :: (SDoc, Fixity) -> (SDoc, Fixity) -> HsExpr RdrName -> SDoc
sectionPrecErr op arg_op section
= vcat [ptext (sLit "The operator") <+> ppr_opfix op <+> ptext (sLit "of a section"),
nest 4 (ptext (sLit "must have lower precedence than the operand") <+> ppr_opfix arg_op),
sectionPrecErr :: (Name, Fixity) -> (Name, Fixity) -> HsExpr RdrName -> RnM ()
sectionPrecErr op@(n1,_) arg_op@(n2,_) section
| isUnboundName n1 || isUnboundName n2
= return () -- Avoid error cascade
| otherwise
= addErr $ vcat [ptext (sLit "The operator") <+> ppr_opfix op <+> ptext (sLit "of a section"),
nest 4 (sep [ptext (sLit "must have lower precedence than that of the operand,"),
nest 2 (ptext (sLit "namely") <+> ppr_opfix arg_op)]),
nest 4 (ptext (sLit "in the section:") <+> quotes (ppr section))]
pp_prefix_minus :: SDoc
pp_prefix_minus = ptext (sLit "prefix `-'")
ppr_op :: Outputable a => a -> SDoc
ppr_op op = quotes (ppr op) -- Here, op can be a Name or a (Var n), where n is a Name
ppr_opfix :: (SDoc, Fixity) -> SDoc
ppr_opfix (pp_op, fixity) = pp_op <+> brackets (ppr fixity)
ppr_opfix :: (Name, Fixity) -> SDoc
ppr_opfix (op, fixity) = pp_op <+> brackets (ppr fixity)
where
pp_op | op == negateName = ptext (sLit "prefix `-'")
| otherwise = quotes (ppr op)
\end{code}
%*********************************************************
......
......@@ -15,7 +15,7 @@ module TypeRep (
Kind, ThetaType, -- Synonyms
funTyCon,
funTyCon, funTyConName,
-- Pretty-printing
pprType, pprParendType, pprTypeApp,
......
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