\begin{code}
module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
- matchCtxt,
- tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig,
- tcMatchPats,
- TcStmtCtxt(..), TcMatchCtxt(..)
+ matchCtxt, TcMatchCtxt(..),
+ tcStmts, tcDoStmts,
+ tcDoStmt, tcMDoStmt, tcGuardStmt
) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho, tcMonoExpr )
+import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr )
import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
Match(..), LMatch, GRHSs(..), GRHS(..),
Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
- ReboundNames, LPat, HsBindGroup(..),
- pprMatch, isDoExpr,
- pprMatchContext, pprStmtContext, pprStmtResultContext,
- collectPatsBinders, glueBindsOnGRHSs
- )
-import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) )
+ pprMatch, isIrrefutableHsPat, mkHsCoerce,
+ pprMatchContext, pprStmtContext,
+ noSyntaxExpr, matchGroupArity, pprMatches,
+ ExprCoFn )
import TcRnMonad
-import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) )
-import Inst ( tcSyntaxName, tcInstCall )
+import TcHsType ( tcPatSig, UserTypeCtxt(..) )
+import Inst ( 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, mkTyConApp,
- liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy )
-import TcBinds ( tcBindsAndThen )
-import TcUnify ( Expected(..), zapExpectedType, readExpectedType,
- unifyTauTy, subFunTys, unifyListTy, unifyTyConApp,
- checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen,
- unifyAppTy )
+ tcExtendTyVarEnv2 )
+import TcPat ( PatCtxt(..), tcPats, tcPat )
+import TcMType ( newFlexiTyVarTy, newFlexiTyVarTys )
+import TcType ( TcType, TcRhoType,
+ BoxySigmaType, BoxyRhoType,
+ mkFunTys, mkFunTy, mkAppTy, mkTyConApp,
+ liftedTypeKind )
+import TcBinds ( tcLocalBinds )
+import TcUnify ( boxySplitAppTy, boxySplitTyConApp, boxySplitListTy,
+ subFunTys, tcSubExp, withBox )
import TcSimplify ( bindInstsOfLocalFuns )
import Name ( Name )
-import TysWiredIn ( boolTy, parrTyCon, listTyCon )
+import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy )
+import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName )
import Id ( idType, mkLocalId )
-import CoreFVs ( idFreeTyVars )
-import VarSet
-import BasicTypes ( RecFlag(..) )
-import Util ( isSingleton, notNull )
+import TyCon ( TyCon )
import Outputable
-import SrcLoc ( Located(..), noLoc )
-
-import List ( nub )
+import SrcLoc ( Located(..), getLoc )
+import ErrUtils ( Message )
\end{code}
%************************************************************************
\begin{code}
tcMatchesFun :: Name
-> MatchGroup Name
- -> Expected TcRhoType -- Expected type of function
- -> TcM (MatchGroup TcId) -- Returns type of body
+ -> BoxyRhoType -- Expected type of function
+ -> TcM (ExprCoFn, MatchGroup TcId) -- Returns type of body
tcMatchesFun fun_name matches exp_ty
= do { -- Check that they all have the same no of arguments
-- 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)
+ checkArgs fun_name matches
-- ToDo: Don't use "expected" stuff if there ain't a type signature
-- because inconsistency between branches
-- 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 ->
+ ; subFunTys doc n_pats exp_ty $ \ pat_tys rhs_ty ->
tcMatches match_ctxt pat_tys rhs_ty matches
}
where
- match_ctxt = MC { mc_what = FunRhs fun_name,
- mc_body = tcMonoExpr }
+ doc = ptext SLIT("The equation(s) for") <+> quotes (ppr fun_name)
+ <+> ptext SLIT("have") <+> speakNOf n_pats (ptext SLIT("argument"))
+ n_pats = matchGroupArity matches
+ match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcPolyExpr }
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
tcMatchesCase :: TcMatchCtxt -- Case context
-> TcRhoType -- Type of scrutinee
-> MatchGroup Name -- The case alternatives
- -> Expected TcRhoType -- Type of whole case expressions
+ -> BoxyRhoType -- 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 }
+tcMatchesCase ctxt scrut_ty matches res_ty
+ = tcMatches ctxt [scrut_ty] res_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 ->
+tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (ExprCoFn, MatchGroup TcId)
+tcMatchLambda match res_ty
+ = subFunTys doc n_pats res_ty $ \ pat_tys rhs_ty ->
tcMatches match_ctxt pat_tys rhs_ty match
where
+ n_pats = matchGroupArity match
+ doc = sep [ ptext SLIT("The lambda expression")
+ <+> quotes (pprSetDepth 1 $ pprMatches LambdaExpr match),
+ -- The pprSetDepth makes the abstraction print briefly
+ ptext SLIT("has") <+> speakNOf n_pats (ptext SLIT("argument"))]
match_ctxt = MC { mc_what = LambdaExpr,
- mc_body = tcMonoExpr }
+ mc_body = tcPolyExpr }
\end{code}
@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
\begin{code}
-tcGRHSsPat :: GRHSs Name
- -> Expected TcRhoType
- -> TcM (GRHSs TcId)
-tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty
+tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
+tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty
where
match_ctxt = MC { mc_what = PatBindRhs,
- mc_body = tcMonoExpr }
+ mc_body = tcPolyExpr }
\end{code}
\begin{code}
tcMatches :: TcMatchCtxt
- -> [Expected TcRhoType] -- Expected pattern types
- -> Expected TcRhoType -- Expected result-type of the Match.
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- 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
+ -> BoxyRhoType
-> 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')) }
+ ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) }
-------------
tcMatch :: TcMatchCtxt
- -> [Expected TcRhoType] -- Expected pattern types
- -> Expected TcRhoType -- Expected result-type of the Match.
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- 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
+ where
+ tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $
+ do { (pats', grhss') <- tcPats LamPat pats pat_tys rhs_ty $
+ tc_grhss ctxt maybe_rhs_sig grhss
+ ; returnM (Match pats' Nothing grhss') }
-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 { (inner_ty, sig_tvs) <- tcPatSig ResSigCtxt res_sig rhs_ty
+ ; tcExtendTyVarEnv2 sig_tvs $
+ tcGRHSs ctxt grhss inner_ty }
-------------
-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') }
+tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
--------------
-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
+-- Notice that we pass in the full res_ty, so that we get
+-- good inference from simple things like
+-- f = \(x::forall a.a->a) -> <stuff>
+-- We used to force it to be a monotype when there was more than one guard
+-- but we don't need to do that any more
--------------
-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
- mappM (wrapLocM tc_grhs) grhss `thenM` \ grhss' ->
- returnM (GRHSs grhss' [])
-\end{code}
+tcGRHSs ctxt (GRHSs grhss binds) res_ty
+ = do { (binds', grhss') <- tcLocalBinds binds $
+ mappM (wrapLocM (tcGRHS ctxt res_ty)) grhss
+ ; returnM (GRHSs grhss' binds') }
-\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}
-
-
-%************************************************************************
-%* *
-\subsection{tcMatchPats}
-%* *
-%************************************************************************
+-------------
+tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId)
-\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) }
+tcGRHS ctxt res_ty (GRHS guards rhs)
+ = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $
+ mc_body ctxt rhs
+ ; return (GRHS guards' rhs') }
where
-
-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 }
+ stmt_ctxt = PatGuard (mc_what ctxt)
\end{code}
\begin{code}
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] }
+ -> [LStmt Name]
+ -> LHsExpr Name
+ -> BoxyRhoType
+ -> TcM (HsExpr TcId) -- Returns a HsDo
+tcDoStmts ListComp stmts body res_ty
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt ListComp body) body
+ ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) }
+
+tcDoStmts PArrComp stmts body res_ty
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt PArrComp body) body
+ ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) }
+
+tcDoStmts DoExpr stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty) stmts res_ty' $
+ tcBody (doBodyCtxt DoExpr body) body
+ ; return (HsDo DoExpr stmts' body' res_ty') }
+
+tcDoStmts ctxt@(MDoExpr _) stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+
+ ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $
+ tcBody (doBodyCtxt ctxt body) body
+
+ ; 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)
+
+tcBody :: Message -> LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId)
+tcBody ctxt body res_ty
+ = -- addErrCtxt ctxt $ -- This context adds little that is useful
+ tcPolyExpr body res_ty
\end{code}
%* *
%************************************************************************
-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
+type TcStmtChecker
+ = forall thing. HsStmtContext Name
+ -> Stmt Name
+ -> BoxyRhoType -- Result type for comprehension
+ -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt
+ -> TcM (Stmt TcId, thing)
+
+ -- The incoming BoxyRhoType may be refined by type refinements
+ -- before being passed to the thing_inside
+
+tcStmts :: HsStmtContext Name
+ -> TcStmtChecker -- NB: higher-rank type
-> [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)
+ -> BoxyRhoType
+ -> (BoxyRhoType -> 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 [] res_ty thing_inside
+ = do { thing <- thing_inside res_ty
+ ; return ([], thing) }
+
+-- LetStmts are handled uniformly, regardless of context
+tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside
+ = do { (binds', (stmts',thing)) <- tcLocalBinds binds $
+ tcStmts ctxt stmt_chk stmts res_ty thing_inside
+ ; return (L loc (LetStmt binds') : stmts', thing) }
+
+-- For the vanilla case, handle the location-setting part
+tcStmts ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside
+ = do { (stmt', (stmts', thing)) <-
+ setSrcSpan loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ stmt_chk ctxt stmt res_ty $ \ res_ty' ->
+ popErrCtxt $
+ tcStmts ctxt stmt_chk stmts res_ty' $
+ thing_inside
+ ; return (L loc stmt' : stmts', thing) }
+
+--------------------------------
+-- Pattern guards
+tcGuardStmt :: TcStmtChecker
+tcGuardStmt ctxt (ExprStmt guard _ _) res_ty thing_inside
+ = do { guard' <- tcMonoExpr guard boolTy
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) }
+
+tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; (pat', thing) <- tcPat LamPat pat rhs_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcGuardStmt ctxt stmt res_ty thing_inside
+ = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
+
+
+--------------------------------
+-- List comprehensions and PArrays
+
+tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
+ -> TcStmtChecker
+
+-- A generator, pat <- rhs
+tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty ->
+ tcMonoExpr rhs (mkTyConApp m_tc [ty])
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+-- A boolean guard
+tcLcStmt m_tc ctxt (ExprStmt rhs _ _) res_ty thing_inside
+ = do { rhs' <- tcMonoExpr rhs boolTy
+ ; thing <- thing_inside res_ty
+ ; 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 ctxt (ParStmt bndr_stmts_s) elt_ty thing_inside
+ = do { (pairs', thing) <- loop bndr_stmts_s
+ ; return (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
- = 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. This binding may shadow
- -- some of them with polymorphic things with the same Name
- -- (see note [RecStmt] in HsExpr)
- getLIE thing_inside `thenM` \ (thing, lie) ->
- bindInstsOfLocalFuns lie later_ids `thenM` \ lie_binds ->
+ -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
+ loop [] = do { thing <- thing_inside elt_ty -- No refinement from pattern
+ ; return ([], thing) } -- matching in the branches
+
+ loop ((stmts, names) : pairs)
+ = do { (stmts', (ids, pairs', thing))
+ <- tcStmts ctxt (tcLcStmt m_tc) stmts elt_ty $ \ elt_ty' ->
+ do { ids <- tcLookupLocalIds names
+ ; (pairs', thing) <- loop pairs
+ ; return (ids, pairs', thing) }
+ ; return ( (stmts', ids) : pairs', thing ) }
+
+tcLcStmt m_tc ctxt stmt elt_ty thing_inside
+ = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Do-notation
+-- The main excitement here is dealing with rebindable syntax
+
+tcDoStmt :: TcType -- Monad type, m
+ -> TcStmtChecker
+
+tcDoStmt m_ty ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+ -- 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.
+
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+
+ -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b
+ ; let bind_ty = mkFunTys [mkAppTy m_ty pat_ty,
+ mkFunTy pat_ty res_ty] res_ty
+ ; 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 ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b
+ a_ty <- newFlexiTyVarTy 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' <- tcPolyExpr rhs rhs_ty
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' then_op' rhs_ty, thing) }
+
+tcDoStmt m_ty ctxt stmt res_ty thing_inside
+ = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Mdo-notation
+-- The distinctive features here are
+-- (a) RecStmts, and
+-- (b) no rebindable syntax
+
+tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
+ -> TcStmtChecker
+tcMDoStmt tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- tc_rhs rhs
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcMDoStmt tc_rhs ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { (rhs', elt_ty) <- tc_rhs rhs
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) }
+
+tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) res_ty thing_inside
+ = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind
+ ; let rec_ids = zipWith mkLocalId recNames rec_tys
+ ; tcExtendIdEnv rec_ids $ do
+ { (stmts', (later_ids, rec_rets))
+ <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ res_ty' ->
+ -- 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 res_ty))
+ -- 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
- returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) $
- combine (L src_loc (LetStmt [HsBindGroup lie_binds [] Recursive])) $
- thing)
+ ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, 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 ->
+ = do { poly_id <- tcLookupId rec_name
-- 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)
+ ; co_fn <- tcSubExp (idType poly_id) mono_ty
+ ; return (mkHsCoerce co_fn (HsVar poly_id)) }
+tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside
+ = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
-------------------------------
-glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing
- -- ToDo: fix the noLoc
\end{code}
number of args are used in each equation.
\begin{code}
-sameNoOfArgs :: MatchGroup Name -> Bool
-sameNoOfArgs (MatchGroup matches _)
- = isSingleton (nub (map args_in_match matches))
+checkArgs :: Name -> MatchGroup Name -> TcM ()
+checkArgs fun (MatchGroup (match1:matches) _)
+ | null bad_matches = return ()
+ | otherwise
+ = failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+>
+ ptext SLIT("have different numbers of arguments"),
+ nest 2 (ppr (getLoc match1)),
+ nest 2 (ppr (getLoc (head bad_matches)))])
where
+ n_args1 = args_in_match match1
+ bad_matches = [m | m <- matches, args_in_match m /= n_args1]
+
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
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
+
+doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc
+doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr body)
- ppr_id id ty = ppr id <+> dcolon <+> ppr ty
- -- Don't zonk the types so we get the separate, un-unified versions
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr stmt)
\end{code}
projects / ghc-hetmet.git / blobdiff