%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchExpected ) where
+module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
+ matchCtxt,
+ tcDoStmts, tcStmts, tcMDoStmt, tcGuardStmt, tcThingWithSig,
+ tcMatchPats,
+ TcMatchCtxt(..)
+ ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
+import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcCheckRho, tcInferRho, tcMonoExpr, tcCheckSigma )
-import HsSyn ( HsBinds(..), Match(..), GRHSsAndBinds(..), GRHS(..),
- HsExpr(..), MonoBinds(..),
- collectPatBinders, pprMatch, getMatchLoc
+import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ LPat, pprMatch, isIrrefutableHsPat,
+ pprMatchContext, pprStmtContext, pprMatchRhsContext,
+ collectPatsBinders, glueBindsOnGRHSs, noSyntaxExpr
)
-import RnHsSyn ( RenamedMatch )
-import TcHsSyn ( TcIdBndr, TcMatch )
-
-import TcMonad
-import Inst ( Inst, LIE, plusLIE )
-import TcEnv ( TcIdOcc(..), newMonoIds )
-import TcPat ( tcPat )
-import TcType ( TcType, TcMaybe, zonkTcType )
+import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) )
+
+import TcRnMonad
+import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) )
+import Inst ( tcInstCall, newMethodFromName )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv,
+ tcExtendTyVarEnv )
+import TcPat ( PatCtxt(..), tcPats )
+import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType )
+import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys,
+ tyVarsOfTypes, tidyOpenTypes, isSigmaTy,
+ liftedTypeKind, openTypeKind, mkFunTy, mkAppTy )
+import TcBinds ( tcBindsAndThen )
+import TcUnify ( Expected(..), zapExpectedType, readExpectedType,
+ unifyTauTy, subFunTys, unifyTyConApp,
+ checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen,
+ unifyAppTy, zapToListTy, zapToTyConApp )
import TcSimplify ( bindInstsOfLocalFuns )
-import Unify ( unifyTauTy, unifyTauTyList, unifyFunTy )
-import Name ( Name {- instance Outputable -} )
-
-import Kind ( Kind, mkTypeKind )
-import BasicTypes ( RecFlag(..) )
-import Type ( isTyVarTy, isTauTy, mkFunTy, splitFunTy_maybe )
-import Util
+import Name ( Name )
+import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy )
+import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName )
+import Id ( idType, mkLocalId )
+import TyCon ( TyCon )
+import CoreFVs ( idFreeTyVars )
+import VarSet
+import Util ( isSingleton )
import Outputable
-import SrcLoc (SrcLoc)
+import SrcLoc ( Located(..) )
+
+import List ( nub )
\end{code}
+%************************************************************************
+%* *
+\subsection{tcMatchesFun, tcMatchesCase}
+%* *
+%************************************************************************
+
@tcMatchesFun@ typechecks a @[Match]@ list which occurs in a
@FunMonoBind@. The second argument is the name of the function, which
is used in error messages. It checks that all the equations have the
\begin{code}
tcMatchesFun :: Name
- -> TcType s -- Expected type
- -> [RenamedMatch]
- -> TcM s ([TcMatch s], LIE s)
-
-tcMatchesFun fun_name expected_ty matches@(first_match:_)
- = -- Set the location to that of the first equation, so that
- -- any inter-equation error messages get some vaguely
- -- sensible location. Note: we have to do this odd
- -- ann-grabbing, because we don't always have annotations in
- -- hand when we call tcMatchesFun...
-
- tcAddSrcLoc (getMatchLoc first_match) (
-
- -- Check that they all have the same no of arguments
- checkTc (all_same (noOfArgs matches))
- (varyingArgsErr fun_name matches) `thenTc_`
+ -> MatchGroup Name
+ -> Expected TcRhoType -- Expected type of function
+ -> TcM (MatchGroup TcId) -- Returns type of body
+
+tcMatchesFun fun_name matches exp_ty
+ = do { -- Check that they all have the same no of arguments
+ -- Location is in the monad, set the caller so that
+ -- any inter-equation error messages get some vaguely
+ -- sensible location. Note: we have to do this odd
+ -- ann-grabbing, because we don't always have annotations in
+ -- hand when we call tcMatchesFun...
+ checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches)
-- ToDo: Don't use "expected" stuff if there ain't a type signature
-- because inconsistency between branches
-- may show up as something wrong with the (non-existent) type signature
- -- We need to substitute so that we can see as much about the type as possible
- zonkTcType expected_ty `thenNF_Tc` \ expected_ty' ->
- tcMatchesExpected expected_ty' (MFun fun_name) matches
-
- )
+ -- This is one of two places places we call subFunTys
+ -- The point is that if expected_y is a "hole", we want
+ -- to make pat_tys and rhs_ty as "holes" too.
+ ; exp_ty' <- zapExpectedBranches matches exp_ty
+ ; subFunTys matches exp_ty' $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty matches
+ }
where
- all_same :: [Int] -> Bool
- all_same [] = True -- Should never happen (ToDo: panic?)
- all_same [x] = True
- all_same (x:xs) = all ((==) x) xs
+ match_ctxt = MC { mc_what = FunRhs fun_name,
+ mc_body = tcMonoExpr }
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
parser guarantees that each equation has exactly one argument.
\begin{code}
-tcMatchesCase :: TcType s -> [RenamedMatch] -> TcM s ([TcMatch s], LIE s)
-tcMatchesCase expected_ty matches = tcMatchesExpected expected_ty MCase matches
+tcMatchesCase :: TcMatchCtxt -- Case context
+ -> TcRhoType -- Type of scrutinee
+ -> MatchGroup Name -- The case alternatives
+ -> Expected TcRhoType -- Type of whole case expressions
+ -> TcM (MatchGroup TcId) -- Translated alternatives
+
+tcMatchesCase ctxt scrut_ty matches exp_ty
+ = do { exp_ty' <- zapExpectedBranches matches exp_ty
+ ; tcMatches ctxt [Check scrut_ty] exp_ty' matches }
+
+tcMatchLambda :: MatchGroup Name -> Expected TcRhoType -> TcM (MatchGroup TcId)
+tcMatchLambda match exp_ty -- One branch so no unifyBranches needed
+ = subFunTys match exp_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty match
+ where
+ match_ctxt = MC { mc_what = LambdaExpr,
+ mc_body = tcMonoExpr }
\end{code}
+@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
\begin{code}
-data FunOrCase = MCase | MFun Name -- Records whether doing fun or case rhss;
- -- used to produced better error messages
-
-tcMatchesExpected :: TcType s
- -> FunOrCase
- -> [RenamedMatch]
- -> TcM s ([TcMatch s], LIE s)
-
-tcMatchesExpected expected_ty fun_or_case [match]
- = tcAddSrcLoc (getMatchLoc match) $
- tcAddErrCtxt (matchCtxt fun_or_case match) $
- tcMatchExpected [] expected_ty match `thenTc` \ (match', lie) ->
- returnTc ([match'], lie)
-
-tcMatchesExpected expected_ty fun_or_case (match1 : matches)
- = tcAddSrcLoc (getMatchLoc match1) (
- tcAddErrCtxt (matchCtxt fun_or_case match1) $
- tcMatchExpected [] expected_ty match1
- ) `thenTc` \ (match1', lie1) ->
- tcMatchesExpected expected_ty fun_or_case matches `thenTc` \ (matches', lie2) ->
- returnTc (match1' : matches', plusLIE lie1 lie2)
+tcGRHSsPat :: GRHSs Name
+ -> Expected TcRhoType
+ -> TcM (GRHSs TcId)
+tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty
+ where
+ match_ctxt = MC { mc_what = PatBindRhs,
+ mc_body = tcMonoExpr }
\end{code}
-\begin{code}
-tcMatchExpected
- :: [TcIdBndr s] -- Ids bound by enclosing matches
- -> TcType s -- This gives the expected
- -- result-type of the Match. Early unification
- -- with this guy gives better error messages
- -> RenamedMatch
- -> TcM s (TcMatch s,LIE s) -- NB No type returned, because it was passed
- -- in instead!
-
-tcMatchExpected matched_ids expected_ty the_match@(PatMatch pat match)
- = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) ->
-
- let binders = collectPatBinders pat
- in
- newMonoIds binders mkTypeKind (\ mono_ids ->
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- unifyTauTy pat_ty arg_ty `thenTc_`
- tcMatchExpected (mono_ids ++ matched_ids)
- rest_ty match `thenTc` \ (match', lie_match) ->
+%************************************************************************
+%* *
+\subsection{tcMatch}
+%* *
+%************************************************************************
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match)
- )
+\begin{code}
+tcMatches :: TcMatchCtxt
+ -> [Expected TcRhoType] -- Expected pattern types
+ -> Expected TcRhoType -- Expected result-type of the Match.
+ -> MatchGroup Name
+ -> TcM (MatchGroup TcId)
+
+data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module
+ = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is
+ mc_body :: LHsExpr Name -- Type checker for a body of an alternative
+ -> Expected TcRhoType
+ -> TcM (LHsExpr TcId) }
+
+tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _)
+ = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
+ ; pat_tys' <- mapM readExpectedType pat_tys
+ ; rhs_ty' <- readExpectedType rhs_ty
+ ; return (MatchGroup matches' (mkFunTys pat_tys' rhs_ty')) }
+
+-------------
+tcMatch :: TcMatchCtxt
+ -> [Expected TcRhoType] -- Expected pattern types
+ -> Expected TcRhoType -- Expected result-type of the Match.
+ -> LMatch Name
+ -> TcM (LMatch TcId)
+
+tcMatch ctxt pat_tys rhs_ty match
+ = wrapLocM (tc_match ctxt pat_tys rhs_ty) match
+
+tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $
+ do { (pats', grhss') <- tcMatchPats pats pat_tys rhs_ty $
+ tc_grhss ctxt maybe_rhs_sig grhss rhs_ty
+ ; returnM (Match pats' Nothing grhss') }
+
+
+-------------
+tc_grhss ctxt Nothing grhss rhs_ty
+ = tcGRHSs ctxt grhss rhs_ty -- No result signature
+
+tc_grhss ctxt (Just res_sig) grhss rhs_ty
+ = do { (sig_tvs, sig_ty) <- tcHsPatSigType ResSigCtxt res_sig
+ ; traceTc (text "tc_grhss" <+> ppr sig_tvs)
+ ; (co_fn, grhss') <- tcExtendTyVarEnv sig_tvs $
+ tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty
+
+ -- Push the coercion down to the right hand sides,
+ -- because there is no convenient place to hang it otherwise.
+ ; if isIdCoercion co_fn then
+ return grhss'
+ else
+ return (lift_grhss co_fn grhss') }
+
+-------------
+lift_grhss co_fn (GRHSs grhss binds)
+ = GRHSs (map (fmap lift_grhs) grhss) binds
+ where
+ lift_grhs (GRHS stmts rhs) = GRHS stmts (fmap (co_fn <$>) rhs)
+
+-------------
+tcGRHSs :: TcMatchCtxt -> GRHSs Name
+ -> Expected TcRhoType
+ -> TcM (GRHSs TcId)
+
+ -- Special case when there is just one equation with a degenerate
+ -- guard; then we pass in the full Expected type, so that we get
+ -- good inference from simple things like
+ -- f = \(x::forall a.a->a) -> <stuff>
+ -- This is a consequence of the fact that tcStmts takes a TcType,
+ -- not a Expected TcType, a decision we could revisit if necessary
+tcGRHSs ctxt (GRHSs [L loc1 (GRHS [] rhs)] binds) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ mc_body ctxt rhs exp_ty `thenM` \ rhs' ->
+ returnM (GRHSs [L loc1 (GRHS [] rhs')] [])
+
+tcGRHSs ctxt (GRHSs grhss binds) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ do { exp_ty' <- zapExpectedType exp_ty openTypeKind
+ -- Even if there is only one guard, we zap the RHS type to
+ -- a monotype. Reason: it makes tcStmts much easier,
+ -- and even a one-armed guard has a notional second arm
+
+ ; let match_ctxt = mc_what ctxt
+ stmt_ctxt = PatGuard match_ctxt
+ tc_grhs (GRHS guards rhs)
+ = do { (guards', rhs')
+ <- tcStmts stmt_ctxt (tcGuardStmt exp_ty') guards $
+ addErrCtxt (grhsCtxt match_ctxt rhs) $
+ tcCheckRho rhs exp_ty'
+ ; return (GRHS guards' rhs') }
+
+ ; grhss' <- mappM (wrapLocM tc_grhs) grhss
+ ; returnM (GRHSs grhss' []) }
+\end{code}
-tcMatchExpected matched_ids expected_ty (GRHSMatch grhss_and_binds)
- = -- Check that the remaining "expected type" is not a rank-2 type
- -- If it is it'll mess up the unifier when checking the RHS
- checkTc (isTauTy expected_ty)
- lurkingRank2SigErr `thenTc_`
- tcGRHSsAndBinds expected_ty grhss_and_binds `thenTc` \ (GRHSsAndBindsOut grhss binds ty, lie) ->
+\begin{code}
+tcThingWithSig :: TcSigmaType -- Type signature
+ -> (TcRhoType -> TcM r) -- How to type check the thing inside
+ -> Expected TcRhoType -- Overall expected result type
+ -> TcM (ExprCoFn, r)
+-- Used for expressions with a type signature, and for result type signatures
+
+tcThingWithSig sig_ty thing_inside res_ty
+ | not (isSigmaTy sig_ty)
+ = thing_inside sig_ty `thenM` \ result ->
+ tcSubExp res_ty sig_ty `thenM` \ co_fn ->
+ returnM (co_fn, result)
+
+ | otherwise -- The signature has some outer foralls
+ = -- Must instantiate the outer for-alls of sig_tc_ty
+ -- else we risk instantiating a ? res_ty to a forall-type
+ -- which breaks the invariant that tcMonoExpr only returns phi-types
+ tcGen sig_ty emptyVarSet thing_inside `thenM` \ (gen_fn, result) ->
+ tcInstCall InstSigOrigin sig_ty `thenM` \ (inst_fn, _, inst_sig_ty) ->
+ tcSubExp res_ty inst_sig_ty `thenM` \ co_fn ->
+ returnM (co_fn <.> inst_fn <.> gen_fn, result)
+ -- Note that we generalise, then instantiate. Ah well.
+\end{code}
- -- In case there are any polymorpic, overloaded binders in the pattern
- -- (which can happen in the case of rank-2 type signatures, or data constructors
- -- with polymorphic arguments), we must do a bindInstsOfLocalFns here
- bindInstsOfLocalFuns lie matched_ids `thenTc` \ (lie', inst_mbinds) ->
- let
- binds' = case inst_mbinds of
- EmptyMonoBinds -> binds -- The common case
- other -> MonoBind inst_mbinds [] Recursive `ThenBinds` binds
- in
- returnTc (GRHSMatch (GRHSsAndBindsOut grhss binds' ty), lie')
+
+%************************************************************************
+%* *
+\subsection{tcMatchPats}
+%* *
+%************************************************************************
+
+\begin{code}
+tcMatchPats :: [LPat Name]
+ -> [Expected TcSigmaType] -- Pattern types
+ -> Expected TcRhoType -- Result type;
+ -- used only to check existential escape
+ -> TcM a
+ -> TcM ([LPat TcId], a)
+-- Typecheck the patterns, extend the environment to bind the variables,
+-- do the thing inside, use any existentially-bound dictionaries to
+-- discharge parts of the returning LIE, and deal with pattern type
+-- signatures
+
+tcMatchPats pats tys body_ty thing_inside
+ = do { (pats', ex_tvs, res) <- tcPats LamPat pats tys thing_inside
+ ; tcCheckExistentialPat pats' ex_tvs tys body_ty
+ ; returnM (pats', res) }
+
+tcCheckExistentialPat :: [LPat TcId] -- Patterns (just for error message)
+ -> [TcTyVar] -- Existentially quantified tyvars bound by pattern
+ -> [Expected TcSigmaType] -- Types of the patterns
+ -> Expected TcRhoType -- Type of the body of the match
+ -- Tyvars in either of these must not escape
+ -> TcM ()
+ -- NB: we *must* pass "pats_tys" not just "body_ty" to tcCheckExistentialPat
+ -- For example, we must reject this program:
+ -- data C = forall a. C (a -> Int)
+ -- f (C g) x = g x
+ -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int).
+
+tcCheckExistentialPat pats [] pat_tys body_ty
+ = return () -- Short cut for case when there are no existentials
+
+tcCheckExistentialPat pats ex_tvs pat_tys body_ty
+ = do { tys <- mapM readExpectedType (body_ty : pat_tys)
+ ; addErrCtxtM (sigPatCtxt (collectPatsBinders pats) ex_tvs tys) $
+ checkSigTyVarsWrt (tyVarsOfTypes tys) ex_tvs }
\end{code}
-@noOfArgs@ takes a @[RenamedMatch]@ and returns a list telling how
-many arguments were used in each of the equations. This is used to
-report a sensible error message when different equations have
-different numbers of arguments.
+%************************************************************************
+%* *
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
+%* *
+%************************************************************************
\begin{code}
-noOfArgs :: [RenamedMatch] -> [Int]
+tcDoStmts :: HsStmtContext Name
+ -> [LStmt Name]
+ -> LHsExpr Name
+ -> Expected TcRhoType
+ -> TcM (HsExpr TcId) -- Returns a HsDo
+tcDoStmts ListComp stmts body res_ty
+ = do { elt_ty <- zapToListTy res_ty
+ ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon elt_ty) stmts $
+ addErrCtxt (doBodyCtxt ListComp body) $
+ tcCheckRho body elt_ty
+ ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) }
+
+tcDoStmts PArrComp stmts body res_ty
+ = do { [elt_ty] <- zapToTyConApp parrTyCon res_ty
+ ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon elt_ty) stmts $
+ addErrCtxt (doBodyCtxt PArrComp body) $
+ tcCheckRho body elt_ty
+ ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) }
+
+tcDoStmts DoExpr stmts body res_ty
+ = do { res_ty' <- zapExpectedType res_ty liftedTypeKind
+ ; (m_ty, _) <- unifyAppTy res_ty'
+ ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty res_ty') stmts $
+ addErrCtxt (doBodyCtxt DoExpr body) $
+ tcCheckRho body res_ty'
+ ; return (HsDo DoExpr stmts' body' res_ty') }
+
+tcDoStmts cxt@(MDoExpr _) stmts body res_ty
+ = do { res_ty' <- zapExpectedType res_ty liftedTypeKind
+ ; (m_ty, _) <- unifyAppTy res_ty'
+ ; let tc_rhs rhs = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; (n_ty, pat_ty) <- unifyAppTy rhs_ty
+ ; unifyTauTy m_ty n_ty
+ ; return (rhs', pat_ty) }
+
+ ; (stmts', body') <- tcStmts cxt (tcMDoStmt res_ty' tc_rhs) stmts $
+ addErrCtxt (doBodyCtxt cxt body) $
+ tcCheckRho body res_ty'
+
+ ; let names = [mfixName, bindMName, thenMName, returnMName, failMName]
+ ; insts <- mapM (newMethodFromName DoOrigin m_ty) names
+ ; return (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') }
+
+tcDoStmts ctxt stmts body res_ty = pprPanic "tcDoStmts" (pprStmtContext ctxt)
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{tcStmts}
+%* *
+%************************************************************************
-noOfArgs ms = map args_in_match ms
+\begin{code}
+type TcStmtChecker
+ = forall thing. HsStmtContext Name
+ -> Stmt Name
+ -> TcM thing
+ -> TcM (Stmt TcId, thing)
+
+tcStmts :: HsStmtContext Name
+ -> TcStmtChecker -- NB: higher-rank type
+ -> [LStmt Name]
+ -> TcM thing
+ -> TcM ([LStmt TcId], thing)
+
+-- Note the higher-rank type. stmt_chk is applied at different
+-- types in the equations for tcStmts
+
+tcStmts ctxt stmt_chk [] thing_inside
+ = do { thing <- thing_inside
+ ; return ([], thing) }
+
+-- LetStmts are handled uniformly, regardless of context
+tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) thing_inside
+ = tcBindsAndThen -- No error context, but a binding group is
+ glue_binds -- rather a large thing for an error context anyway
+ binds
+ (tcStmts ctxt stmt_chk stmts thing_inside)
+ where
+ glue_binds binds (stmts, thing) = (L loc (LetStmt [binds]) : stmts, thing)
+
+
+-- For the vanilla case, handle the location-setting part
+tcStmts ctxt stmt_chk (L loc stmt : stmts) thing_inside
+ = do { (stmt', (stmts', thing)) <-
+ setSrcSpan loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ stmt_chk ctxt stmt $
+ popErrCtxt $
+ tcStmts ctxt stmt_chk stmts $
+ thing_inside
+ ; return (L loc stmt' : stmts', thing) }
+
+--------------------------------
+-- Pattern guards
+tcGuardStmt :: TcType -> TcStmtChecker
+tcGuardStmt res_ty ctxt (ExprStmt guard _ _) thing_inside
+ = do { guard' <- tcCheckRho guard boolTy
+ ; thing <- thing_inside
+ ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) }
+
+tcGuardStmt res_ty ctxt (BindStmt pat rhs _ _) thing_inside
+ = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; (pat', thing) <- tcBindPat pat rhs_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcGuardStmt res_ty ctxt stmt thing_inside
+ = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
+
+
+--------------------------------
+-- List comprehensions and PArrays
+
+tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
+ -> TcType -- The element type of the list or PArray
+ -> TcStmtChecker
+
+-- A generator, pat <- rhs
+tcLcStmt m_tc elt_ty ctxt (BindStmt pat rhs _ _) thing_inside
+ = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; [pat_ty] <- unifyTyConApp m_tc rhs_ty
+ ; (pat', thing) <- tcBindPat pat pat_ty elt_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+-- A boolean guard
+tcLcStmt m_tc elt_ty ctxt (ExprStmt rhs _ _) thing_inside
+ = do { rhs' <- tcCheckRho rhs boolTy
+ ; thing <- thing_inside
+ ; return (ExprStmt rhs' noSyntaxExpr boolTy, thing) }
+
+-- A parallel set of comprehensions
+-- [ (g x, h x) | ... ; let g v = ...
+-- | ... ; let h v = ... ]
+--
+-- It's possible that g,h are overloaded, so we need to feed the LIE from the
+-- (g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns).
+-- Similarly if we had an existential pattern match:
+--
+-- data T = forall a. Show a => C a
+--
+-- [ (show x, show y) | ... ; C x <- ...
+-- | ... ; C y <- ... ]
+--
+-- Then we need the LIE from (show x, show y) to be simplified against
+-- the bindings for x and y.
+--
+-- It's difficult to do this in parallel, so we rely on the renamer to
+-- ensure that g,h and x,y don't duplicate, and simply grow the environment.
+-- So the binders of the first parallel group will be in scope in the second
+-- group. But that's fine; there's no shadowing to worry about.
+
+tcLcStmt m_tc elt_ty ctxt (ParStmt bndr_stmts_s) thing_inside
+ = do { (pairs', thing) <- loop bndr_stmts_s
+ ; return (ParStmt pairs', thing) }
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (GRHSMatch _) = 0
- args_in_match (PatMatch _ match) = 1 + args_in_match match
+ -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
+ loop [] = do { thing <- thing_inside
+ ; return ([], thing) }
+
+ loop ((stmts, names) : pairs)
+ = do { (stmts', (ids, pairs', thing))
+ <- tcStmts ctxt (tcLcStmt m_tc elt_ty) stmts $
+ do { ids <- tcLookupLocalIds names
+ ; (pairs', thing) <- loop pairs
+ ; return (ids, pairs', thing) }
+ ; return ( (stmts', ids) : pairs', thing ) }
+
+tcLcStmt m_tc elt_ty ctxt stmt thing_inside
+ = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Do-notation
+-- The main excitement here is dealing with rebindable syntax
+
+tcDoStmt :: TcType -- Monad type, m
+ -> TcType -- Result type, m b
+ -> TcStmtChecker
+ -- BindStmt
+tcDoStmt m_ty res_ty ctxt (BindStmt pat rhs bind_op fail_op) thing_inside
+ = do { -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b
+ ; (rhs', rhs_ty) <- tcInferRho rhs
+ -- We should use type *inference* for the RHS computations, becuase of GADTs.
+ -- do { pat <- rhs; <rest> }
+ -- is rather like
+ -- case rhs of { pat -> <rest> }
+ -- We do inference on rhs, so that information about its type can be refined
+ -- when type-checking the pattern.
+
+ ; (n_ty, pat_ty) <- unifyAppTy rhs_ty
+ ; unifyTauTy m_ty n_ty
+ ; let bind_ty = mkFunTys [rhs_ty, mkFunTy pat_ty res_ty] res_ty
+
+ ; (pat', thing) <- tcBindPat pat pat_ty res_ty thing_inside
+
+ -- Rebindable syntax stuff
+ ; bind_op' <- tcSyntaxOp DoOrigin bind_op bind_ty
+ -- If (but only if) the pattern can fail,
+ -- typecheck the 'fail' operator
+ ; fail_op' <- if isIrrefutableHsPat pat'
+ then return noSyntaxExpr
+ else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy res_ty)
+ ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
+
+
+tcDoStmt m_ty res_ty ctxt (ExprStmt rhs then_op _) thing_inside
+ = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b
+ a_ty <- newTyFlexiVarTy liftedTypeKind
+ ; let rhs_ty = mkAppTy m_ty a_ty
+ then_ty = mkFunTys [rhs_ty, res_ty] res_ty
+ ; then_op' <- tcSyntaxOp DoOrigin then_op then_ty
+ ; rhs' <- tcCheckSigma rhs rhs_ty
+ ; thing <- thing_inside
+ ; return (ExprStmt rhs' then_op' rhs_ty, thing) }
+
+tcDoStmt m_ty res_ty ctxt stmt thing_inside
+ = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Mdo-notation
+-- The distinctive features here are
+-- (a) RecStmts, and
+-- (b) no rebindable syntax
+
+tcMDoStmt :: TcType -- Result type, m b
+ -> (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
+ -> TcStmtChecker
+tcMDoStmt res_ty tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) thing_inside
+ = do { (rhs', pat_ty) <- tc_rhs rhs
+ ; (pat', thing) <- tcBindPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcMDoStmt res_ty tc_rhs ctxt (ExprStmt rhs then_op _) thing_inside
+ = do { (rhs', elt_ty) <- tc_rhs rhs
+ ; thing <- thing_inside
+ ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) }
+
+tcMDoStmt res_ty tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) thing_inside
+ = do { rec_tys <- newTyFlexiVarTys (length recNames) liftedTypeKind
+ ; let rec_ids = zipWith mkLocalId recNames rec_tys
+ ; tcExtendIdEnv rec_ids $ do
+ { (stmts', (later_ids, rec_rets))
+ <- tcStmts ctxt (tcMDoStmt res_ty tc_rhs) stmts $
+ -- ToDo: res_ty not really right
+ do { rec_rets <- zipWithM tc_ret recNames rec_tys
+ ; later_ids <- tcLookupLocalIds laterNames
+ ; return (later_ids, rec_rets) }
+
+ ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE thing_inside)
+ -- NB: The rec_ids for the recursive things
+ -- already scope over this part. This binding may shadow
+ -- some of them with polymorphic things with the same Name
+ -- (see note [RecStmt] in HsExpr)
+ ; lie_binds <- bindInstsOfLocalFuns lie later_ids
+
+ ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing)
+ }}
+ where
+ -- Unify the types of the "final" Ids with those of "knot-tied" Ids
+ tc_ret rec_name mono_ty
+ = tcLookupId rec_name `thenM` \ poly_id ->
+ -- poly_id may have a polymorphic type
+ -- but mono_ty is just a monomorphic type variable
+ tcSubExp (Check mono_ty) (idType poly_id) `thenM` \ co_fn ->
+ returnM (co_fn <$> HsVar poly_id)
+
+tcMDoStmt res_ty tc_rhs ctxt stmt thing_inside
+ = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
+
+-----------------
+tcBindPat :: LPat Name -> TcType
+ -> TcType -- Result type; used only to check existential escape
+ -> TcM a
+ -> TcM (LPat TcId, a)
+tcBindPat pat pat_ty res_ty thing_inside
+ = do { ([pat'],thing) <- tcMatchPats [pat] [Check pat_ty]
+ (Check res_ty) thing_inside
+ ; return (pat', thing) }
\end{code}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
-\begin{code}
-matchCtxt MCase match
- = hang (ptext SLIT("In a \"case\" branch:"))
- 4 (pprMatch True{-is_case-} match)
-matchCtxt (MFun fun) match
- = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr fun), char ':'])
- 4 (hcat [ppr fun, space, pprMatch False{-not case-} match])
-\end{code}
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
+@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
+number of args are used in each equation.
+
+\begin{code}
+sameNoOfArgs :: MatchGroup Name -> Bool
+sameNoOfArgs (MatchGroup matches _)
+ = isSingleton (nub (map args_in_match matches))
+ where
+ args_in_match :: LMatch Name -> Int
+ args_in_match (L _ (Match pats _ _)) = length pats
+\end{code}
\begin{code}
varyingArgsErr name matches
= sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
-lurkingRank2SigErr
- = ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type")
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
+
+grhsCtxt ctxt rhs = hang (ptext SLIT("In") <+> pprMatchRhsContext ctxt <> colon)
+ 4 (ppr rhs)
+
+doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc
+doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr body)
+
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr stmt)
+
+sigPatCtxt bound_ids bound_tvs tys tidy_env
+ = -- tys is (body_ty : pat_tys)
+ mapM zonkTcType tys `thenM` \ tys' ->
+ let
+ (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
+ (_env2, tidy_body_ty : tidy_pat_tys) = tidyOpenTypes env1 tys'
+ in
+ returnM (env1,
+ sep [ptext SLIT("When checking an existential match that binds"),
+ nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)),
+ ptext SLIT("The pattern(s) have type(s):") <+> vcat (map ppr tidy_pat_tys),
+ ptext SLIT("The body has type:") <+> ppr tidy_body_ty
+ ])
+ where
+ show_ids = filter is_interesting bound_ids
+ is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
+
+ ppr_id id ty = ppr id <+> dcolon <+> ppr ty
+ -- Don't zonk the types so we get the separate, un-unified versions
\end{code}
projects / ghc-hetmet.git / blobdiff