%
-% (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, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
+ matchCtxt,
+ tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig,
+ tcMatchPats,
+ TcStmtCtxt(..), TcMatchCtxt(..)
+ ) where
+
#include "HsVersions.h"
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where
-
-IMP_Ubiq()
-
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-#else
-import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
-#endif
-
-import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat,
- HsExpr, HsBinds, OutPat, Fake, Stmt,
- collectPatBinders, pprMatch )
-import RnHsSyn ( SYN_IE(RenamedMatch) )
-import TcHsSyn ( TcIdOcc(..), SYN_IE(TcMatch) )
-
-import TcMonad
-import Inst ( Inst, SYN_IE(LIE), plusLIE )
-import TcEnv ( newMonoIds )
-import TcPat ( tcPat )
-import TcType ( SYN_IE(TcType), TcMaybe, zonkTcType )
-import Unify ( unifyTauTy, unifyTauTyList )
-import Name ( Name {- instance Outputable -} )
-
-import Kind ( Kind, mkTypeKind )
-import Pretty
-import Type ( isTyVarTy, mkFunTy, getFunTy_maybe )
-import Util
+import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho, tcMonoExpr )
+
+import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ ReboundNames, LPat,
+ pprMatch, isDoExpr,
+ pprMatchContext, pprStmtContext, pprStmtResultContext,
+ collectPatsBinders, glueBindsOnGRHSs
+ )
+import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) )
+
+import TcRnMonad
+import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) )
+import Inst ( tcSyntaxName, tcInstCall )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv,
+ tcExtendTyVarEnv )
+import TcPat ( PatCtxt(..), tcPats )
+import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType, isRigidType )
+import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys,
+ tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkTyConApp,
+ liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy )
+import TcBinds ( tcBindsAndThen )
+import TcUnify ( Expected(..), zapExpectedType, readExpectedType,
+ unifyTauTy, subFunTys, unifyListTy, unifyTyConApp,
+ checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen,
+ unifyAppTy )
+import Name ( Name )
+import TysWiredIn ( boolTy, parrTyCon, listTyCon )
+import Id ( idType, mkLocalId )
+import CoreFVs ( idFreeTyVars )
+import VarSet
+import Util ( isSingleton, notNull )
import Outputable
-#if __GLASGOW_HASKELL__ >= 202
-import SrcLoc (SrcLoc)
-#endif
+import SrcLoc ( Located(..), noLoc )
+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 (get_Match_loc 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 (get_Match_loc 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 (get_Match_loc 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)
-
-tcMatches :: [RenamedMatch] -> TcM s ([TcMatch s], LIE s, [TcType s])
-
-tcMatches [match]
- = tcAddSrcLoc (get_Match_loc match) $
- tcMatch match `thenTc` \ (match', lie, ty) ->
- returnTc ([match'], lie, [ty])
-
-tcMatches (match1 : matches)
- = tcAddSrcLoc (get_Match_loc match1) (
- tcMatch match1
- ) `thenTc` \ (match1', lie1, match1_ty) ->
- tcMatches matches `thenTc` \ (matches', lie2, matches_ty) ->
- returnTc (match1' : matches', plusLIE lie1 lie2, match1_ty : matches_ty)
+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}
+
+%************************************************************************
+%* *
+\subsection{tcMatch}
+%* *
+%************************************************************************
+
\begin{code}
-tcMatchExpected
- :: 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 expected_ty the_match@(PatMatch pat match)
- = case getFunTy_maybe expected_ty of
-
- Nothing -> -- Not a function type (eg type variable)
- -- So use tcMatch instead
- tcMatch the_match `thenTc` \ (match', lie_match, match_ty) ->
- unifyTauTy expected_ty match_ty `thenTc_`
- returnTc (match', lie_match)
-
- Just (arg_ty,rest_ty) -> -- It's a function type!
- let binders = collectPatBinders pat
- in
- newMonoIds binders mkTypeKind (\ _ ->
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- unifyTauTy pat_ty arg_ty `thenTc_`
- tcMatchExpected rest_ty match `thenTc` \ (match', lie_match) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match)
- )
-
-tcMatchExpected expected_ty (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- unifyTauTy expected_ty grhss_ty `thenTc_`
- returnTc (GRHSMatch grhss_and_binds', lie)
-
-tcMatch :: RenamedMatch -> TcM s (TcMatch s, LIE s, TcType s)
-
-tcMatch (PatMatch pat match)
- = let binders = collectPatBinders pat
+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) = GRHS (map lift_stmt stmts)
+
+ lift_stmt (L loc (ResultStmt e)) = L loc (ResultStmt (fmap (co_fn <$>) e))
+ lift_stmt stmt = stmt
+
+-------------
+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 [L loc2 (ResultStmt rhs)])] binds) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ mc_body ctxt rhs exp_ty `thenM` \ rhs' ->
+ returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] [])
+
+tcGRHSs ctxt (GRHSs grhss binds) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' ->
+ -- 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
+ stmt_ctxt = SC { sc_what = PatGuard (mc_what ctxt),
+ sc_rhs = tcInferRho,
+ sc_body = sc_body,
+ sc_ty = exp_ty' }
+ sc_body body = mc_body ctxt body (Check exp_ty')
+
+ tc_grhs (GRHS guarded)
+ = tcStmts stmt_ctxt guarded `thenM` \ guarded' ->
+ returnM (GRHS guarded')
in
- newMonoIds binders mkTypeKind (\ _ ->
- -- NB TypeKind; lambda-bound variables are allowed
- -- to unify with unboxed types.
-
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- tcMatch match `thenTc` \ (match', lie_match, match_ty) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match,
- mkFunTy pat_ty match_ty)
- )
-
-tcMatch (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty)
+ mappM (wrapLocM tc_grhs) grhss `thenM` \ grhss' ->
+ returnM (GRHSs grhss' [])
\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.
-
\begin{code}
-noOfArgs :: [RenamedMatch] -> [Int]
+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}
-noOfArgs ms = map args_in_match ms
+
+%************************************************************************
+%* *
+\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 { do_refinement <- can_refine body_ty
+ ; (pats', ex_tvs, res) <- tcPats (LamPat do_refinement) pats tys thing_inside
+ ; tcCheckExistentialPat pats' ex_tvs tys body_ty
+ ; returnM (pats', res) }
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (GRHSMatch _) = 0
- args_in_match (PatMatch _ match) = 1 + args_in_match match
+ -- Do GADT refinement if we are doing checking (not inference)
+ -- and the body_ty is completely rigid
+ -- ToDo: explain why
+ can_refine (Infer _) = return False
+ can_refine (Check ty) = isRigidType ty
+
+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}
-@get_Match_loc@ takes a @RenamedMatch@ and returns the
-source-location gotten from the GRHS inside.
-THis is something of a nuisance, but no more.
+
+%************************************************************************
+%* *
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
+%* *
+%************************************************************************
\begin{code}
-get_Match_loc :: RenamedMatch -> SrcLoc
-
-get_Match_loc (PatMatch _ m) = get_Match_loc m
-get_Match_loc (GRHSMatch (GRHSsAndBindsIn (g:_) _))
- = get_GRHS_loc g
- where
- get_GRHS_loc (OtherwiseGRHS _ locn) = locn
- get_GRHS_loc (GRHS _ _ locn) = locn
+tcDoStmts :: HsStmtContext Name
+ -> [LStmt Name] -> ReboundNames Name
+ -> TcRhoType -- To keep it simple, we don't have an "expected" type here
+ -> TcM ([LStmt TcId], ReboundNames TcId)
+tcDoStmts PArrComp stmts method_names res_ty
+ = do { [elt_ty] <- unifyTyConApp parrTyCon res_ty
+ ; stmts' <- tcComprehension PArrComp parrTyCon elt_ty stmts
+ ; return (stmts', [{- unused -}]) }
+
+tcDoStmts ListComp stmts method_names res_ty
+ = unifyListTy res_ty ` thenM` \ elt_ty ->
+ tcComprehension ListComp listTyCon elt_ty stmts `thenM` \ stmts' ->
+ returnM (stmts', [{- unused -}])
+
+tcDoStmts do_or_mdo stmts method_names res_ty
+ = newTyFlexiVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty ->
+ newTyFlexiVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_`
+ let
+ ctxt = SC { sc_what = do_or_mdo,
+ sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; rhs_elt_ty <- unifyAppTy m_ty rhs_ty
+ ; return (rhs', rhs_elt_ty) },
+ sc_body = \ body -> tcCheckRho body res_ty,
+ sc_ty = res_ty }
+ in
+ tcStmts ctxt stmts `thenM` \ stmts' ->
+
+ -- Build the then and zero methods in case we need them
+ -- It's important that "then" and "return" appear just once in the final LIE,
+ -- not only for typechecker efficiency, but also because otherwise during
+ -- simplification we end up with silly stuff like
+ -- then = case d of (t,r) -> t
+ -- then = then
+ -- where the second "then" sees that it already exists in the "available" stuff.
+ mapM (tcSyntaxName DoOrigin m_ty) method_names `thenM` \ methods ->
+
+ returnM (stmts', methods)
+
+tcComprehension do_or_lc m_tycon elt_ty stmts
+ = tcStmts ctxt stmts
+ where
+ ctxt = SC { sc_what = do_or_lc,
+ sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; [rhs_elt_ty] <- unifyTyConApp m_tycon rhs_ty
+ ; return (rhs', rhs_elt_ty) },
+ sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no m_tycon here!
+ sc_ty = mkTyConApp m_tycon [elt_ty] }
\end{code}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
-\begin{code}
-matchCtxt MCase match sty
- = hang (ptext SLIT("In a \"case\" branch:"))
- 4 (pprMatch sty True{-is_case-} match)
-matchCtxt (MFun fun) match sty
- = hang (hcat [ptext SLIT("In an equation for function "), ppr sty fun, char ':'])
- 4 (pprQuote sty $ \sty -> hcat [ppr sty fun, space, pprMatch sty False{-not case-} match])
+%************************************************************************
+%* *
+\subsection{tcStmts}
+%* *
+%************************************************************************
+
+Typechecking statements is rendered a bit tricky by parallel list 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.
+
+\begin{code}
+tcStmts ctxt stmts
+ = ASSERT( notNull stmts )
+ tcStmtsAndThen (:) ctxt stmts (returnM [])
+
+data TcStmtCtxt
+ = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is
+ sc_rhs :: LHsExpr Name -> TcM (LHsExpr TcId, TcType), -- Type inference for RHS computations
+ sc_body :: LHsExpr Name -> TcM (LHsExpr TcId), -- Type checker for return computation
+ sc_ty :: TcType } -- Return type; used *only* to check
+ -- for escape in existential patterns
+ -- We 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.
+
+tcStmtsAndThen
+ :: (LStmt TcId -> thing -> thing) -- Combiner
+ -> TcStmtCtxt
+ -> [LStmt Name]
+ -> TcM thing
+ -> TcM thing
+
+ -- Base case
+tcStmtsAndThen combine ctxt [] thing_inside
+ = thing_inside
+
+tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside
+ = tcStmtAndThen combine ctxt stmt $
+ tcStmtsAndThen combine ctxt stmts $
+ thing_inside
+
+ -- LetStmt
+tcStmtAndThen combine ctxt (L _ (LetStmt binds)) thing_inside
+ = tcBindsAndThen -- No error context, but a binding group is
+ (glue_binds combine) -- rather a large thing for an error context anyway
+ binds
+ thing_inside
+
+ -- BindStmt
+tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside
+ = setSrcSpan src_loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ do { (exp', pat_ty) <- sc_rhs ctxt exp
+ ; ([pat'], thing) <- tcMatchPats [pat] [Check pat_ty] (Check (sc_ty ctxt)) $
+ popErrCtxt thing_inside
+ ; return (combine (L src_loc (BindStmt pat' exp')) thing) }
+
+ -- ExprStmt
+tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside
+ = setSrcSpan src_loc (
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ if isDoExpr (sc_what ctxt)
+ then -- do or mdo; the expression is a computation
+ sc_rhs ctxt exp `thenM` \ (exp', exp_ty) ->
+ returnM (L src_loc (ExprStmt exp' exp_ty))
+ else -- List comprehensions, pattern guards; expression is a boolean
+ tcCheckRho exp boolTy `thenM` \ exp' ->
+ returnM (L src_loc (ExprStmt exp' boolTy))
+ ) `thenM` \ stmt' ->
+
+ thing_inside `thenM` \ thing ->
+ returnM (combine stmt' thing)
+
+
+ -- ParStmt
+tcStmtAndThen combine ctxt (L src_loc (ParStmt bndr_stmts_s)) thing_inside
+ = loop bndr_stmts_s `thenM` \ (pairs', thing) ->
+ returnM (combine (L src_loc (ParStmt pairs')) thing)
+ where
+ loop [] = thing_inside `thenM` \ thing ->
+ returnM ([], thing)
+
+ loop ((stmts, bndrs) : pairs)
+ = tcStmtsAndThen combine_par ctxt stmts $
+ -- Notice we pass on ctxt; the result type is used only
+ -- to get escaping type variables for checkExistentialPat
+ tcLookupLocalIds bndrs `thenM` \ bndrs' ->
+ loop pairs `thenM` \ (pairs', thing) ->
+ returnM (([], bndrs') : pairs', thing)
+
+ combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing)
+
+ -- RecStmt
+tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thing_inside
+-- gaw 2004
+ = newTyFlexiVarTys (length recNames) liftedTypeKind `thenM` \ recTys ->
+ let
+ rec_ids = zipWith mkLocalId recNames recTys
+ in
+ tcExtendIdEnv rec_ids $
+ tcStmtsAndThen combine_rec ctxt stmts (
+ zipWithM tc_ret recNames recTys `thenM` \ rec_rets ->
+ tcLookupLocalIds laterNames `thenM` \ later_ids ->
+ returnM ([], (later_ids, rec_rets))
+ ) `thenM` \ (stmts', (later_ids, rec_rets)) ->
+
+ tcExtendIdEnv later_ids $
+ -- NB: The rec_ids for the recursive things
+ -- already scope over this part
+ thing_inside `thenM` \ thing ->
+
+ returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) thing)
+ where
+ combine_rec stmt (stmts, thing) = (stmt:stmts, thing)
+
+ -- 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 (L src_loc (co_fn <$> HsVar poly_id))
+
+ -- Result statements
+tcStmtAndThen combine ctxt (L src_loc stmt@(ResultStmt exp)) thing_inside
+ = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' ->
+ thing_inside `thenM` \ thing ->
+ returnM (combine (L src_loc (ResultStmt exp')) thing)
+
+
+------------------------------
+glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing
+ -- ToDo: fix the noLoc
\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}
-varyingArgsErr name matches sty
- = sep [ptext SLIT("Varying number of arguments for function"), ppr sty name]
+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)]
+
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
+
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) 4 (ppr stmt)
+ where
+ pp_ctxt = case stmt of
+ ResultStmt _ -> pprStmtResultContext
+ other -> pprStmtContext
+
+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