\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcCheckSigma, tcCheckRho, tcInferRho,
- tcMonoExpr, tcExpr, tcSyntaxOp
- ) where
+module TcExpr ( tcPolyExpr, tcPolyExprNC,
+ tcMonoExpr, tcInferRho, tcSyntaxOp ) where
#include "HsVersions.h"
import qualified DsMeta
#endif
-import HsSyn ( HsExpr(..), LHsExpr, HsLit(..), ArithSeqInfo(..), recBindFields,
- HsMatchContext(..), HsRecordBinds, mkHsApp )
-import TcHsSyn ( hsLitType, (<$>) )
+import HsSyn ( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields,
+ HsMatchContext(..), HsRecordBinds, mkHsApp, mkHsDictApp, mkHsTyApp )
+import TcHsSyn ( hsLitType )
import TcRnMonad
-import TcUnify ( Expected(..), tcInfer, zapExpectedType, zapExpectedTo,
- tcSubExp, tcGen, tcSub,
- unifyFunTys, zapToListTy, zapToTyConApp )
-import BasicTypes ( isMarkedStrict )
-import Inst ( tcOverloadedLit, newMethodFromName, newIPDict,
- newDicts, newMethodWithGivenTy, tcInstStupidTheta, tcInstCall )
+import TcUnify ( tcInfer, tcSubExp, tcGen, boxyUnify, subFunTys, zapToMonotype, stripBoxyType,
+ boxySplitListTy, boxySplitTyConApp, wrapFunResCoercion, boxySubMatchType, unBox )
+import BasicTypes ( Arity, isMarkedStrict )
+import Inst ( newMethodFromName, newIPDict, instToId,
+ newDicts, newMethodWithGivenTy, tcInstStupidTheta )
import TcBinds ( tcLocalBinds )
import TcEnv ( tcLookup, tcLookupId,
tcLookupDataCon, tcLookupGlobalId
)
import TcArrows ( tcProc )
-import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcThingWithSig, TcMatchCtxt(..) )
+import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, TcMatchCtxt(..) )
import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
-import TcPat ( badFieldCon, refineTyVars )
-import TcMType ( tcInstTyVars, tcInstType, newTyFlexiVarTy, zonkTcType )
-import TcType ( TcTyVar, TcType, TcSigmaType, TcRhoType,
- tcSplitFunTys, mkTyVarTys,
- isSigmaTy, mkFunTy, mkTyConApp, tyVarsOfTypes, isLinearPred,
- tcSplitSigmaTy, tidyOpenType
+import TcPat ( tcOverloadedLit, badFieldCon )
+import TcMType ( tcInstTyVars, newFlexiTyVarTy, newBoxyTyVars, readFilledBox,
+ tcInstBoxyTyVar, tcInstTyVar, zonkTcType )
+import TcType ( TcType, TcSigmaType, TcRhoType,
+ BoxySigmaType, BoxyRhoType, ThetaType,
+ tcSplitFunTys, mkTyVarTys, mkFunTys,
+ tcMultiSplitSigmaTy, tcSplitFunTysN,
+ isSigmaTy, mkFunTy, mkTyConApp, isLinearPred,
+ exactTyVarsOfType, exactTyVarsOfTypes, mkTyVarTy,
+ tidyOpenType,
+ zipTopTvSubst, zipOpenTvSubst, substTys, substTyVar, lookupTyVar
)
-import Kind ( openTypeKind, liftedTypeKind, argTypeKind )
+import Kind ( argTypeKind )
-import Id ( idType, recordSelectorFieldLabel, isRecordSelector, isNaughtyRecordSelector )
-import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks,
+import Id ( idType, idName, recordSelectorFieldLabel, isRecordSelector,
+ isNaughtyRecordSelector, isDataConId_maybe )
+import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks, dataConSourceArity,
dataConWrapId, isVanillaDataCon, dataConTyVars, dataConOrigArgTys )
import Name ( Name )
import TyCon ( FieldLabel, tyConStupidTheta, tyConDataCons )
import Type ( substTheta, substTy )
-import Var ( tyVarKind )
-import VarSet ( emptyVarSet, elemVarSet )
+import Var ( TyVar, tyVarKind )
+import VarSet ( emptyVarSet, elemVarSet, unionVarSet )
import TysWiredIn ( boolTy, parrTyCon, tupleTyCon )
import PrelNames ( enumFromName, enumFromThenName,
enumFromToName, enumFromThenToName,
import DynFlags
import StaticFlags ( opt_NoMethodSharing )
import HscTypes ( TyThing(..) )
-import SrcLoc ( Located(..), unLoc, getLoc )
+import SrcLoc ( Located(..), unLoc, noLoc, getLoc )
import Util
import ListSetOps ( assocMaybe )
import Maybes ( catMaybes )
%************************************************************************
\begin{code}
--- tcCheckSigma does type *checking*; it's passed the expected type of the result
-tcCheckSigma :: LHsExpr Name -- Expession to type check
- -> TcSigmaType -- Expected type (could be a polytpye)
- -> TcM (LHsExpr TcId) -- Generalised expr with expected type
-
-tcCheckSigma expr expected_ty
- = -- traceTc (text "tcExpr" <+> (ppr expected_ty $$ ppr expr)) `thenM_`
- tc_expr' expr expected_ty
-
-tc_expr' expr sigma_ty
- | isSigmaTy sigma_ty
- = tcGen sigma_ty emptyVarSet (
- \ rho_ty -> tcCheckRho expr rho_ty
- ) `thenM` \ (gen_fn, expr') ->
- returnM (L (getLoc expr') (gen_fn <$> unLoc expr'))
-
-tc_expr' expr rho_ty -- Monomorphic case
- = tcCheckRho expr rho_ty
-\end{code}
-
-Typecheck expression which in most cases will be an Id.
-The expression can return a higher-ranked type, such as
- (forall a. a->a) -> Int
-so we must create a hole to pass in as the expected tyvar.
+tcPolyExpr, tcPolyExprNC
+ :: LHsExpr Name -- Expession to type check
+ -> BoxySigmaType -- Expected type (could be a polytpye)
+ -> TcM (LHsExpr TcId) -- Generalised expr with expected type
+
+-- tcPolyExpr is a convenient place (frequent but not too frequent) place
+-- to add context information.
+-- The NC version does not do so, usually because the caller wants
+-- to do so himself.
+
+tcPolyExpr expr res_ty
+ = addErrCtxt (exprCtxt (unLoc expr)) $
+ tcPolyExprNC expr res_ty
+
+tcPolyExprNC expr res_ty
+ | isSigmaTy res_ty
+ = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (tcPolyExprNC expr)
+ -- Note the recursive call to tcPolyExpr, because the
+ -- type may have multiple layers of for-alls
+ ; return (L (getLoc expr') (HsCoerce gen_fn (unLoc expr'))) }
+
+ | otherwise
+ = tcMonoExpr expr res_ty
+
+---------------
+tcPolyExprs :: [LHsExpr Name] -> [TcType] -> TcM [LHsExpr TcId]
+tcPolyExprs [] [] = returnM []
+tcPolyExprs (expr:exprs) (ty:tys)
+ = do { expr' <- tcPolyExpr expr ty
+ ; exprs' <- tcPolyExprs exprs tys
+ ; returnM (expr':exprs') }
+tcPolyExprs exprs tys = pprPanic "tcPolyExprs" (ppr exprs $$ ppr tys)
+
+---------------
+tcMonoExpr :: LHsExpr Name -- Expression to type check
+ -> BoxyRhoType -- Expected type (could be a type variable)
+ -- Definitely no foralls at the top
+ -- Can contain boxes, which will be filled in
+ -> TcM (LHsExpr TcId)
-\begin{code}
-tcCheckRho :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId)
-tcCheckRho expr rho_ty = tcMonoExpr expr (Check rho_ty)
+tcMonoExpr (L loc expr) res_ty
+ = ASSERT( not (isSigmaTy res_ty) )
+ setSrcSpan loc $
+ do { expr' <- tcExpr expr res_ty
+ ; return (L loc expr') }
+---------------
tcInferRho :: LHsExpr Name -> TcM (LHsExpr TcId, TcRhoType)
-tcInferRho (L loc (HsVar name)) = setSrcSpan loc $ do
- { (e,_,ty) <- tcId (OccurrenceOf name) name
- ; return (L loc e, ty) }
-tcInferRho expr = tcInfer (tcMonoExpr expr)
-
-tcSyntaxOp :: InstOrigin -> HsExpr Name -> TcType -> TcM (HsExpr TcId)
--- Typecheck a syntax operator, checking that it has the specified type
--- The operator is always a variable at this stage (i.e. renamer output)
-tcSyntaxOp orig (HsVar op) ty = do { (expr', _, id_ty) <- tcId orig op
- ; co_fn <- tcSub ty id_ty
- ; returnM (co_fn <$> expr') }
-tcSyntaxOp orig other ty = pprPanic "tcSyntaxOp" (ppr other)
+tcInferRho expr = tcInfer (tcMonoExpr expr)
\end{code}
%************************************************************************
%* *
-\subsection{The TAUT rules for variables}TcExpr
+ tcExpr: the main expression typechecker
%* *
%************************************************************************
\begin{code}
-tcMonoExpr :: LHsExpr Name -- Expession to type check
- -> Expected TcRhoType -- Expected type (could be a type variable)
- -- Definitely no foralls at the top
- -- Can be a 'hole'.
- -> TcM (LHsExpr TcId)
+tcExpr :: HsExpr Name -> BoxyRhoType -> TcM (HsExpr TcId)
+tcExpr (HsVar name) res_ty = tcId (OccurrenceOf name) name res_ty
-tcMonoExpr (L loc expr) res_ty
- = setSrcSpan loc (do { expr' <- tcExpr expr res_ty
- ; return (L loc expr') })
+tcExpr (HsLit lit) res_ty = do { boxyUnify (hsLitType lit) res_ty
+ ; return (HsLit lit) }
+
+tcExpr (HsPar expr) res_ty = do { expr' <- tcMonoExpr expr res_ty
+ ; return (HsPar expr') }
-tcExpr :: HsExpr Name -> Expected TcRhoType -> TcM (HsExpr TcId)
-tcExpr (HsVar name) res_ty
- = do { (expr', _, id_ty) <- tcId (OccurrenceOf name) name
- ; co_fn <- tcSubExp res_ty id_ty
- ; returnM (co_fn <$> expr') }
+tcExpr (HsSCC lbl expr) res_ty = do { expr' <- tcMonoExpr expr res_ty
+ ; returnM (HsSCC lbl expr') }
+
+tcExpr (HsCoreAnn lbl expr) res_ty -- hdaume: core annotation
+ = do { expr' <- tcMonoExpr expr res_ty
+ ; return (HsCoreAnn lbl expr') }
+
+tcExpr (HsOverLit lit) res_ty
+ = do { lit' <- tcOverloadedLit (LiteralOrigin lit) lit res_ty
+ ; return (HsOverLit lit') }
+
+tcExpr (NegApp expr neg_expr) res_ty
+ = do { neg_expr' <- tcSyntaxOp (OccurrenceOf negateName) neg_expr
+ (mkFunTy res_ty res_ty)
+ ; expr' <- tcMonoExpr expr res_ty
+ ; return (NegApp expr' neg_expr') }
tcExpr (HsIPVar ip) res_ty
- = -- Implicit parameters must have a *tau-type* not a
- -- type scheme. We enforce this by creating a fresh
- -- type variable as its type. (Because res_ty may not
- -- be a tau-type.)
- newTyFlexiVarTy argTypeKind `thenM` \ ip_ty ->
- -- argTypeKind: it can't be an unboxed tuple
- newIPDict (IPOccOrigin ip) ip ip_ty `thenM` \ (ip', inst) ->
- extendLIE inst `thenM_`
- tcSubExp res_ty ip_ty `thenM` \ co_fn ->
- returnM (co_fn <$> HsIPVar ip')
-\end{code}
+ = do { -- Implicit parameters must have a *tau-type* not a
+ -- type scheme. We enforce this by creating a fresh
+ -- type variable as its type. (Because res_ty may not
+ -- be a tau-type.)
+ ip_ty <- newFlexiTyVarTy argTypeKind -- argTypeKind: it can't be an unboxed tuple
+ ; co_fn <- tcSubExp ip_ty res_ty
+ ; (ip', inst) <- newIPDict (IPOccOrigin ip) ip ip_ty
+ ; extendLIE inst
+ ; return (HsCoerce co_fn (HsIPVar ip')) }
+tcExpr (HsApp e1 e2) res_ty
+ = go e1 [e2]
+ where
+ go :: LHsExpr Name -> [LHsExpr Name] -> TcM (HsExpr TcId)
+ go (L _ (HsApp e1 e2)) args = go e1 (e2:args)
+ go lfun@(L loc fun) args
+ = do { (fun', args') <- addErrCtxt (callCtxt lfun args) $
+ tcApp fun (length args) (tcArgs lfun args) res_ty
+ ; return (unLoc (foldl mkHsApp (L loc fun') args')) }
-%************************************************************************
-%* *
-\subsection{Expressions type signatures}
-%* *
-%************************************************************************
+tcExpr (HsLam match) res_ty
+ = do { (co_fn, match') <- tcMatchLambda match res_ty
+ ; return (HsCoerce co_fn (HsLam match')) }
-\begin{code}
-tcExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
- = addErrCtxt (exprCtxt in_expr) $
- tcHsSigType ExprSigCtxt poly_ty `thenM` \ sig_tc_ty ->
- tcThingWithSig sig_tc_ty (tcCheckRho expr) res_ty `thenM` \ (co_fn, expr') ->
- returnM (co_fn <$> ExprWithTySigOut expr' poly_ty)
+tcExpr in_expr@(ExprWithTySig expr sig_ty) res_ty
+ = do { sig_tc_ty <- tcHsSigType ExprSigCtxt sig_ty
+ ; expr' <- tcPolyExpr expr sig_tc_ty
+ ; co_fn <- tcSubExp sig_tc_ty res_ty
+ ; return (HsCoerce co_fn (ExprWithTySigOut expr' sig_ty)) }
tcExpr (HsType ty) res_ty
= failWithTc (text "Can't handle type argument:" <+> ppr ty)
%************************************************************************
%* *
-\subsection{Other expression forms}
+ Infix operators and sections
%* *
%************************************************************************
\begin{code}
-tcExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' ->
- returnM (HsPar expr')
-tcExpr (HsSCC lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' ->
- returnM (HsSCC lbl expr')
-tcExpr (HsCoreAnn lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> -- hdaume: core annotation
- returnM (HsCoreAnn lbl expr')
-
-tcExpr (HsLit lit) res_ty = tcLit lit res_ty
+tcExpr in_expr@(OpApp arg1 lop@(L loc op) fix arg2) res_ty
+ = do { (op', [arg1', arg2']) <- tcApp op 2 (tcArgs lop [arg1,arg2]) res_ty
+ ; return (OpApp arg1' (L loc op') fix arg2') }
-tcExpr (HsOverLit lit) res_ty
- = zapExpectedType res_ty liftedTypeKind `thenM` \ res_ty' ->
- -- Overloaded literals must have liftedTypeKind, because
- -- we're instantiating an overloaded function here,
- -- whereas res_ty might be openTypeKind. This was a bug in 6.2.2
- tcOverloadedLit (LiteralOrigin lit) lit res_ty' `thenM` \ lit' ->
- returnM (HsOverLit lit')
-
-tcExpr (NegApp expr neg_expr) res_ty
- = do { res_ty' <- zapExpectedType res_ty liftedTypeKind
- ; neg_expr' <- tcSyntaxOp (OccurrenceOf negateName) neg_expr
- (mkFunTy res_ty' res_ty')
- ; expr' <- tcCheckRho expr res_ty'
- ; return (NegApp expr' neg_expr') }
-
-tcExpr (HsLam match) res_ty
- = tcMatchLambda match res_ty `thenM` \ match' ->
- returnM (HsLam match')
-
-tcExpr (HsApp e1 e2) res_ty
- = tcApp e1 [e2] res_ty
-\end{code}
-
-Note that the operators in sections are expected to be binary, and
-a type error will occur if they aren't.
-
-\begin{code}
-- Left sections, equivalent to
-- \ x -> e op x,
-- or
-- \ x -> op e x,
-- or just
-- op e
+--
+-- We treat it as similar to the latter, so we don't
+-- actually require the function to take two arguments
+-- at all. For example, (x `not`) means (not x);
+-- you get postfix operators! Not really Haskell 98
+-- I suppose, but it's less work and kind of useful.
-tcExpr in_expr@(SectionL arg1 op) res_ty
- = tcInferRho op `thenM` \ (op', op_ty) ->
- unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' ->
- addErrCtxt (exprCtxt in_expr) $
- tcSubExp res_ty (mkFunTy arg2_ty op_res_ty) `thenM` \ co_fn ->
- returnM (co_fn <$> SectionL arg1' op')
+tcExpr in_expr@(SectionL arg1 lop@(L loc op)) res_ty
+ = do { (op', [arg1']) <- tcApp op 1 (tcArgs lop [arg1]) res_ty
+ ; return (SectionL arg1' (L loc op')) }
--- Right sections, equivalent to \ x -> x op expr, or
+-- Right sections, equivalent to \ x -> x `op` expr, or
-- \ x -> op x expr
-
-tcExpr in_expr@(SectionR op arg2) res_ty
- = tcInferRho op `thenM` \ (op', op_ty) ->
- unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' ->
- addErrCtxt (exprCtxt in_expr) $
- tcSubExp res_ty (mkFunTy arg1_ty op_res_ty) `thenM` \ co_fn ->
- returnM (co_fn <$> SectionR op' arg2')
-
--- equivalent to (op e1) e2:
-
-tcExpr in_expr@(OpApp arg1 op fix arg2) res_ty
- = tcInferRho op `thenM` \ (op', op_ty) ->
- unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' ->
- tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' ->
- addErrCtxt (exprCtxt in_expr) $
- tcSubExp res_ty op_res_ty `thenM` \ co_fn ->
- returnM (co_fn <$> OpApp arg1' op' fix arg2')
+
+tcExpr in_expr@(SectionR lop@(L loc op) arg2) res_ty
+ = do { (co_fn, (op', arg2')) <- subFunTys doc 1 res_ty $ \ [arg1_ty'] res_ty' ->
+ tcApp op 2 (tc_args arg1_ty') res_ty'
+ ; return (HsCoerce co_fn (SectionR (L loc op') arg2')) }
+ where
+ doc = ptext SLIT("The section") <+> quotes (ppr in_expr)
+ <+> ptext SLIT("takes one argument")
+ tc_args arg1_ty' [arg1_ty, arg2_ty]
+ = do { boxyUnify arg1_ty' arg1_ty
+ ; tcArg lop (arg2, arg2_ty, 2) }
\end{code}
\begin{code}
tcMonoExpr expr res_ty
; return (HsLet binds' expr') }
-tcExpr in_expr@(HsCase scrut matches) exp_ty
- = -- We used to typecheck the case alternatives first.
- -- The case patterns tend to give good type info to use
- -- when typechecking the scrutinee. For example
- -- case (map f) of
- -- (x:xs) -> ...
- -- will report that map is applied to too few arguments
- --
- -- But now, in the GADT world, we need to typecheck the scrutinee
- -- first, to get type info that may be refined in the case alternatives
- addErrCtxt (caseScrutCtxt scrut)
- (tcInferRho scrut) `thenM` \ (scrut', scrut_ty) ->
-
- addErrCtxt (caseCtxt in_expr) $
- tcMatchesCase match_ctxt scrut_ty matches exp_ty `thenM` \ matches' ->
- returnM (HsCase scrut' matches')
+tcExpr (HsCase scrut matches) exp_ty
+ = do { -- We used to typecheck the case alternatives first.
+ -- The case patterns tend to give good type info to use
+ -- when typechecking the scrutinee. For example
+ -- case (map f) of
+ -- (x:xs) -> ...
+ -- will report that map is applied to too few arguments
+ --
+ -- But now, in the GADT world, we need to typecheck the scrutinee
+ -- first, to get type info that may be refined in the case alternatives
+ (scrut', scrut_ty) <- addErrCtxt (caseScrutCtxt scrut)
+ (tcInferRho scrut)
+
+ ; traceTc (text "HsCase" <+> ppr scrut_ty)
+ ; matches' <- tcMatchesCase match_ctxt scrut_ty matches exp_ty
+ ; return (HsCase scrut' matches') }
where
match_ctxt = MC { mc_what = CaseAlt,
- mc_body = tcMonoExpr }
+ mc_body = tcPolyExpr }
tcExpr (HsIf pred b1 b2) res_ty
- = addErrCtxt (predCtxt pred)
- (tcCheckRho pred boolTy) `thenM` \ pred' ->
-
- zapExpectedType res_ty openTypeKind `thenM` \ res_ty' ->
- -- C.f. the call to zapToType in TcMatches.tcMatches
-
- tcCheckRho b1 res_ty' `thenM` \ b1' ->
- tcCheckRho b2 res_ty' `thenM` \ b2' ->
- returnM (HsIf pred' b1' b2')
+ = do { pred' <- addErrCtxt (predCtxt pred) $
+ tcMonoExpr pred boolTy
+ ; b1' <- tcMonoExpr b1 res_ty
+ ; b2' <- tcMonoExpr b2 res_ty
+ ; return (HsIf pred' b1' b2') }
tcExpr (HsDo do_or_lc stmts body _) res_ty
= tcDoStmts do_or_lc stmts body res_ty
tcExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list
- = zapToListTy res_ty `thenM` \ elt_ty ->
- mappM (tc_elt elt_ty) exprs `thenM` \ exprs' ->
- returnM (ExplicitList elt_ty exprs')
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; exprs' <- mappM (tc_elt elt_ty) exprs
+ ; return (ExplicitList elt_ty exprs') }
where
- tc_elt elt_ty expr
- = addErrCtxt (listCtxt expr) $
- tcCheckRho expr elt_ty
+ tc_elt elt_ty expr = tcPolyExpr expr elt_ty
tcExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
- = do { [elt_ty] <- zapToTyConApp parrTyCon res_ty
- ; exprs' <- mappM (tc_elt elt_ty) exprs
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; exprs' <- mappM (tc_elt elt_ty) exprs
+ ; ifM (null exprs) (zapToMonotype elt_ty)
+ -- If there are no expressions in the comprehension
+ -- we must still fill in the box
+ -- (Not needed for [] and () becuase they happen
+ -- to parse as data constructors.)
; return (ExplicitPArr elt_ty exprs') }
where
- tc_elt elt_ty expr
- = addErrCtxt (parrCtxt expr) (tcCheckRho expr elt_ty)
+ tc_elt elt_ty expr = tcPolyExpr expr elt_ty
tcExpr (ExplicitTuple exprs boxity) res_ty
- = do { arg_tys <- zapToTyConApp (tupleTyCon boxity (length exprs)) res_ty
- ; exprs' <- tcCheckRhos exprs arg_tys
+ = do { arg_tys <- boxySplitTyConApp (tupleTyCon boxity (length exprs)) res_ty
+ ; exprs' <- tcPolyExprs exprs arg_tys
; return (ExplicitTuple exprs' boxity) }
tcExpr (HsProc pat cmd) res_ty
- = tcProc pat cmd res_ty `thenM` \ (pat', cmd') ->
- returnM (HsProc pat' cmd')
+ = do { (pat', cmd') <- tcProc pat cmd res_ty
+ ; return (HsProc pat' cmd') }
tcExpr e@(HsArrApp _ _ _ _ _) _
= failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e),
\begin{code}
tcExpr expr@(RecordCon (L loc con_name) _ rbinds) res_ty
- = addErrCtxt (recordConCtxt expr) $
- do { (con_expr, _, con_tau) <- setSrcSpan loc $
- tcId (OccurrenceOf con_name) con_name
- ; data_con <- tcLookupDataCon con_name
+ = do { data_con <- tcLookupDataCon con_name
- ; let (arg_tys, record_ty) = tcSplitFunTys con_tau
- flds_w_tys = zipEqual "tcExpr RecordCon" (dataConFieldLabels data_con) arg_tys
-
- -- Make the result type line up
- ; zapExpectedTo res_ty record_ty
-
- -- Typecheck the record bindings
- ; rbinds' <- tcRecordBinds data_con flds_w_tys rbinds
-
-- Check for missing fields
; checkMissingFields data_con rbinds
+ ; let arity = dataConSourceArity data_con
+ check_fields arg_tys
+ = do { rbinds' <- tcRecordBinds data_con arg_tys rbinds
+ ; mapM unBox arg_tys
+ ; return rbinds' }
+ -- The unBox ensures that all the boxes in arg_tys are indeed
+ -- filled, which is the invariant expected by tcIdApp
+
+ ; (con_expr, rbinds') <- tcIdApp con_name arity check_fields res_ty
+
; returnM (RecordCon (L loc (dataConWrapId data_con)) con_expr rbinds') }
-- The main complication with RecordUpd is that we need to explicitly
tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty
- = addErrCtxt (recordUpdCtxt expr) $
-
- -- STEP 0
+ = -- STEP 0
-- Check that the field names are really field names
ASSERT( notNull rbinds )
let
-- it contains *all* the fields that are being updated
con1 = head relevant_cons -- A representative constructor
con1_tyvars = dataConTyVars con1
- con1_fld_tys = dataConFieldLabels con1 `zip` dataConOrigArgTys con1
- common_tyvars = tyVarsOfTypes [ty | (fld,ty) <- con1_fld_tys
- , not (fld `elem` upd_field_lbls) ]
+ con1_flds = dataConFieldLabels con1
+ con1_arg_tys = dataConOrigArgTys con1
+ common_tyvars = exactTyVarsOfTypes [ty | (fld,ty) <- con1_flds `zip` con1_arg_tys
+ , not (fld `elem` upd_field_lbls) ]
is_common_tv tv = tv `elemVarSet` common_tyvars
mk_inst_ty tv result_inst_ty
| is_common_tv tv = returnM result_inst_ty -- Same as result type
- | otherwise = newTyFlexiVarTy (tyVarKind tv) -- Fresh type, of correct kind
+ | otherwise = newFlexiTyVarTy (tyVarKind tv) -- Fresh type, of correct kind
in
tcInstTyVars con1_tyvars `thenM` \ (_, result_inst_tys, inst_env) ->
zipWithM mk_inst_ty con1_tyvars result_inst_tys `thenM` \ inst_tys ->
-- doesn't match the constructor.)
let
result_record_ty = mkTyConApp tycon result_inst_tys
- inst_fld_tys = [(fld, substTy inst_env ty) | (fld, ty) <- con1_fld_tys]
+ con1_arg_tys' = map (substTy inst_env) con1_arg_tys
in
- zapExpectedTo res_ty result_record_ty `thenM_`
- tcRecordBinds con1 inst_fld_tys rbinds `thenM` \ rbinds' ->
+ tcSubExp result_record_ty res_ty `thenM` \ co_fn ->
+ tcRecordBinds con1 con1_arg_tys' rbinds `thenM` \ rbinds' ->
-- STEP 5
-- Typecheck the expression to be updated
-- This is one place where the isVanilla check is important
-- So that inst_tys matches the tycon
in
- tcCheckRho record_expr record_ty `thenM` \ record_expr' ->
+ tcMonoExpr record_expr record_ty `thenM` \ record_expr' ->
-- STEP 6
-- Figure out the LIE we need. We have to generate some
extendLIEs dicts `thenM_`
-- Phew!
- returnM (RecordUpd record_expr' rbinds' record_ty result_record_ty)
+ returnM (HsCoerce co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty))
\end{code}
\begin{code}
tcExpr (ArithSeq _ seq@(From expr)) res_ty
- = zapToListTy res_ty `thenM` \ elt_ty ->
- tcCheckRho expr elt_ty `thenM` \ expr' ->
-
- newMethodFromName (ArithSeqOrigin seq)
- elt_ty enumFromName `thenM` \ enum_from ->
-
- returnM (ArithSeq (HsVar enum_from) (From expr'))
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; expr' <- tcPolyExpr expr elt_ty
+ ; enum_from <- newMethodFromName (ArithSeqOrigin seq)
+ elt_ty enumFromName
+ ; return (ArithSeq (HsVar enum_from) (From expr')) }
tcExpr in_expr@(ArithSeq _ seq@(FromThen expr1 expr2)) res_ty
- = addErrCtxt (arithSeqCtxt in_expr) $
- zapToListTy res_ty `thenM` \ elt_ty ->
- tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
- tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
- newMethodFromName (ArithSeqOrigin seq)
- elt_ty enumFromThenName `thenM` \ enum_from_then ->
-
- returnM (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2'))
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; expr1' <- tcPolyExpr expr1 elt_ty
+ ; expr2' <- tcPolyExpr expr2 elt_ty
+ ; enum_from_then <- newMethodFromName (ArithSeqOrigin seq)
+ elt_ty enumFromThenName
+ ; return (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2')) }
tcExpr in_expr@(ArithSeq _ seq@(FromTo expr1 expr2)) res_ty
- = addErrCtxt (arithSeqCtxt in_expr) $
- zapToListTy res_ty `thenM` \ elt_ty ->
- tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
- tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
- newMethodFromName (ArithSeqOrigin seq)
- elt_ty enumFromToName `thenM` \ enum_from_to ->
-
- returnM (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2'))
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; expr1' <- tcPolyExpr expr1 elt_ty
+ ; expr2' <- tcPolyExpr expr2 elt_ty
+ ; enum_from_to <- newMethodFromName (ArithSeqOrigin seq)
+ elt_ty enumFromToName
+ ; return (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
tcExpr in_expr@(ArithSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = addErrCtxt (arithSeqCtxt in_expr) $
- zapToListTy res_ty `thenM` \ elt_ty ->
- tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
- tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
- tcCheckRho expr3 elt_ty `thenM` \ expr3' ->
- newMethodFromName (ArithSeqOrigin seq)
- elt_ty enumFromThenToName `thenM` \ eft ->
-
- returnM (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3'))
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; expr1' <- tcPolyExpr expr1 elt_ty
+ ; expr2' <- tcPolyExpr expr2 elt_ty
+ ; expr3' <- tcPolyExpr expr3 elt_ty
+ ; eft <- newMethodFromName (ArithSeqOrigin seq)
+ elt_ty enumFromThenToName
+ ; return (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
tcExpr in_expr@(PArrSeq _ seq@(FromTo expr1 expr2)) res_ty
- = addErrCtxt (parrSeqCtxt in_expr) $
- zapToTyConApp parrTyCon res_ty `thenM` \ [elt_ty] ->
- tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
- tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
- newMethodFromName (PArrSeqOrigin seq)
- elt_ty enumFromToPName `thenM` \ enum_from_to ->
-
- returnM (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2'))
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; expr1' <- tcPolyExpr expr1 elt_ty
+ ; expr2' <- tcPolyExpr expr2 elt_ty
+ ; enum_from_to <- newMethodFromName (PArrSeqOrigin seq)
+ elt_ty enumFromToPName
+ ; return (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
tcExpr in_expr@(PArrSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = addErrCtxt (parrSeqCtxt in_expr) $
- zapToTyConApp parrTyCon res_ty `thenM` \ [elt_ty] ->
- tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
- tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
- tcCheckRho expr3 elt_ty `thenM` \ expr3' ->
- newMethodFromName (PArrSeqOrigin seq)
- elt_ty enumFromThenToPName `thenM` \ eft ->
-
- returnM (PArrSeq (HsVar eft) (FromThenTo expr1' expr2' expr3'))
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; expr1' <- tcPolyExpr expr1 elt_ty
+ ; expr2' <- tcPolyExpr expr2 elt_ty
+ ; expr3' <- tcPolyExpr expr3 elt_ty
+ ; eft <- newMethodFromName (PArrSeqOrigin seq)
+ elt_ty enumFromThenToPName
+ ; return (PArrSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
tcExpr (PArrSeq _ _) _
= panic "TcExpr.tcMonoExpr: Infinite parallel array!"
%************************************************************************
%* *
-\subsection{@tcApp@ typchecks an application}
+ Applications
%* *
%************************************************************************
\begin{code}
+---------------------------
+tcApp :: HsExpr Name -- Function
+ -> Arity -- Number of args reqd
+ -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker
+ -> BoxyRhoType -- Result type
+ -> TcM (HsExpr TcId, arg_results)
+
+-- (tcFun fun n_args arg_checker res_ty)
+-- The argument type checker, arg_checker, will be passed exactly n_args types
+
+tcApp (HsVar fun_name) n_args arg_checker res_ty
+ = tcIdApp fun_name n_args arg_checker res_ty
+
+tcApp fun n_args arg_checker res_ty -- The vanilla case (rula APP)
+ = do { arg_boxes <- newBoxyTyVars n_args
+ ; fun' <- tcExpr fun (mkFunTys (mkTyVarTys arg_boxes) res_ty)
+ ; arg_tys' <- mapM readFilledBox arg_boxes
+ ; args' <- arg_checker arg_tys'
+ ; return (fun', args') }
+
+---------------------------
+tcIdApp :: Name -- Function
+ -> Arity -- Number of args reqd
+ -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker
+ -- The arg-checker guarantees to fill all boxes in the arg types
+ -> BoxyRhoType -- Result type
+ -> TcM (HsExpr TcId, arg_results)
+
+-- Call (f e1 ... en) :: res_ty
+-- Type f :: forall a b c. theta => fa_1 -> ... -> fa_k -> fres
+-- (where k <= n; fres has the rest)
+-- NB: if k < n then the function doesn't have enough args, and
+-- presumably fres is a type variable that we are going to
+-- instantiate with a function type
+--
+-- Then fres <= bx_(k+1) -> ... -> bx_n -> res_ty
+
+tcIdApp fun_name n_args arg_checker res_ty
+ = do { fun_id <- lookupFun (OccurrenceOf fun_name) fun_name
+
+ -- Split up the function type
+ ; let (tv_theta_prs, rho) = tcMultiSplitSigmaTy (idType fun_id)
+ (fun_arg_tys, fun_res_ty) = tcSplitFunTysN rho n_args
+
+ qtvs = concatMap fst tv_theta_prs -- Quantified tyvars
+ arg_qtvs = exactTyVarsOfTypes fun_arg_tys
+ res_qtvs = exactTyVarsOfType fun_res_ty
+ -- NB: exactTyVarsOfType. See Note [Silly type synonyms in smart-app]
+ tau_qtvs = arg_qtvs `unionVarSet` res_qtvs
+ k = length fun_arg_tys -- k <= n_args
+ n_missing_args = n_args - k -- Always >= 0
+
+ -- Match the result type of the function with the
+ -- result type of the context, to get an inital substitution
+ ; extra_arg_boxes <- newBoxyTyVars n_missing_args
+ ; let extra_arg_tys' = mkTyVarTys extra_arg_boxes
+ res_ty' = mkFunTys extra_arg_tys' res_ty
+ subst = boxySubMatchType arg_qtvs fun_res_ty res_ty'
+ -- Only bind arg_qtvs, since only they will be
+ -- *definitely* be filled in by arg_checker
+ -- E.g. error :: forall a. String -> a
+ -- (error "foo") :: bx5
+ -- Don't make subst [a |-> bx5]
+ -- because then the result subsumption becomes
+ -- bx5 ~ bx5
+ -- and the unifer doesn't expect the
+ -- same box on both sides
+ inst_qtv tv | Just boxy_ty <- lookupTyVar subst tv = return boxy_ty
+ | tv `elemVarSet` tau_qtvs = do { tv' <- tcInstBoxyTyVar tv
+ ; return (mkTyVarTy tv') }
+ | otherwise = do { tv' <- tcInstTyVar tv
+ ; return (mkTyVarTy tv') }
+ -- The 'otherwise' case handles type variables that are
+ -- mentioned only in the constraints, not in argument or
+ -- result types. We'll make them tau-types
+
+ ; qtys' <- mapM inst_qtv qtvs
+ ; let arg_subst = zipOpenTvSubst qtvs qtys'
+ fun_arg_tys' = substTys arg_subst fun_arg_tys
+
+ -- Typecheck the arguments!
+ -- Doing so will fill arg_qtvs and extra_arg_tys'
+ ; args' <- arg_checker (fun_arg_tys' ++ extra_arg_tys')
+
+ ; let strip qtv qty' | qtv `elemVarSet` arg_qtvs = stripBoxyType qty'
+ | otherwise = return qty'
+ ; qtys'' <- zipWithM strip qtvs qtys'
+ ; extra_arg_tys'' <- mapM readFilledBox extra_arg_boxes
+
+ -- Result subsumption
+ ; let res_subst = zipOpenTvSubst qtvs qtys''
+ fun_res_ty'' = substTy res_subst fun_res_ty
+ res_ty'' = mkFunTys extra_arg_tys'' res_ty
+ ; co_fn <- addErrCtxtM (checkFunResCtxt fun_name res_ty fun_res_ty'') $
+ tcSubExp fun_res_ty'' res_ty''
+
+ -- And pack up the results
+ -- By applying the coercion just to the *function* we can make
+ -- tcFun work nicely for OpApp and Sections too
+ ; fun' <- instFun fun_id qtvs qtys'' tv_theta_prs
+ ; co_fn' <- wrapFunResCoercion fun_arg_tys' co_fn
+ ; return (HsCoerce co_fn' fun', args') }
+\end{code}
-tcApp :: LHsExpr Name -> [LHsExpr Name] -- Function and args
- -> Expected TcRhoType -- Expected result type of application
- -> TcM (HsExpr TcId) -- Translated fun and args
-
-tcApp (L _ (HsApp e1 e2)) args res_ty
- = tcApp e1 (e2:args) res_ty -- Accumulate the arguments
-
-tcApp fun args res_ty
- = do { let n_args = length args
- ; (fun', fun_tvs, fun_tau) <- tcFun fun -- Type-check the function
-
- -- Extract its argument types
- ; (expected_arg_tys, actual_res_ty)
- <- do { traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_tau))
- ; let msg = sep [ptext SLIT("The function") <+> quotes (ppr fun),
- ptext SLIT("is applied to")
- <+> speakN n_args <+> ptext SLIT("arguments")]
- ; unifyFunTys msg n_args fun_tau }
-
- ; case res_ty of
- Check _ -> do -- Connect to result type first
- -- See Note [Push result type in]
- { co_fn <- tcResult fun args res_ty actual_res_ty
- ; the_app' <- tcArgs fun fun' args expected_arg_tys
- ; traceTc (text "tcApp: check" <+> vcat [ppr fun <+> ppr args,
- ppr the_app', ppr actual_res_ty])
- ; returnM (co_fn <$> the_app') }
-
- Infer _ -> do -- Type check args first, then
- -- refine result type, then do tcResult
- { the_app' <- tcArgs fun fun' args expected_arg_tys
- ; subst <- refineTyVars fun_tvs
- ; let actual_res_ty' = substTy subst actual_res_ty
- ; co_fn <- tcResult fun args res_ty actual_res_ty'
- ; traceTc (text "tcApp: infer" <+> vcat [ppr fun <+> ppr args, ppr the_app',
- ppr actual_res_ty, ppr actual_res_ty'])
- ; returnM (co_fn <$> the_app') }
- }
+Note [Silly type synonyms in smart-app]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When we call sripBoxyType, all of the boxes should be filled
+in. But we need to be careful about type synonyms:
+ type T a = Int
+ f :: T a -> Int
+ ...(f x)...
+In the call (f x) we'll typecheck x, expecting it to have type
+(T box). Usually that would fill in the box, but in this case not;
+because 'a' is discarded by the silly type synonym T. So we must
+use exactTyVarsOfType to figure out which type variables are free
+in the argument type.
+
+\begin{code}
+-- tcId is a specialisation of tcIdApp when there are no arguments
+-- tcId f ty = do { (res, _) <- tcIdApp f [] (\[] -> return ()) ty
+-- ; return res }
+
+tcId :: InstOrigin
+ -> Name -- Function
+ -> BoxyRhoType -- Result type
+ -> TcM (HsExpr TcId)
+tcId orig fun_name res_ty
+ = do { traceTc (text "tcId" <+> ppr fun_name <+> ppr res_ty)
+ ; fun_id <- lookupFun orig fun_name
+
+ -- Split up the function type
+ ; let (tv_theta_prs, fun_tau) = tcMultiSplitSigmaTy (idType fun_id)
+ qtvs = concatMap fst tv_theta_prs -- Quantified tyvars
+ tau_qtvs = exactTyVarsOfType fun_tau -- Mentiond in the tau part
+ inst_qtv tv | tv `elemVarSet` tau_qtvs = do { tv' <- tcInstBoxyTyVar tv
+ ; return (mkTyVarTy tv') }
+ | otherwise = do { tv' <- tcInstTyVar tv
+ ; return (mkTyVarTy tv') }
+
+ -- Do the subsumption check wrt the result type
+ ; qtv_tys <- mapM inst_qtv qtvs
+ ; let res_subst = zipTopTvSubst qtvs qtv_tys
+ fun_tau' = substTy res_subst fun_tau
+
+ ; co_fn <- addErrCtxtM (checkFunResCtxt fun_name res_ty fun_tau') $
+ tcSubExp fun_tau' res_ty
+
+ -- And pack up the results
+ ; fun' <- instFun fun_id qtvs qtv_tys tv_theta_prs
+ ; return (HsCoerce co_fn fun') }
-- Note [Push result type in]
--
-- the signature is propagated into MkQ's argument. With the check
-- in the other order, the extra signature in f2 is reqd.]
-----------------
-tcFun :: LHsExpr Name -> TcM (LHsExpr TcId, [TcTyVar], TcRhoType)
--- Instantiate the function, returning the type variables used
--- If the function isn't simple, infer its type, and return no
--- type variables
-tcFun (L loc (HsVar f)) = setSrcSpan loc $ do
- { (fun', tvs, fun_tau) <- tcId (OccurrenceOf f) f
- ; return (L loc fun', tvs, fun_tau) }
-tcFun fun = do { (fun', fun_tau) <- tcInfer (tcMonoExpr fun)
- ; return (fun', [], fun_tau) }
+---------------------------
+tcSyntaxOp :: InstOrigin -> HsExpr Name -> TcType -> TcM (HsExpr TcId)
+-- Typecheck a syntax operator, checking that it has the specified type
+-- The operator is always a variable at this stage (i.e. renamer output)
+tcSyntaxOp orig (HsVar op) ty = tcId orig op ty
+tcSyntaxOp orig other ty = pprPanic "tcSyntaxOp" (ppr other)
-----------------
+---------------------------
+instFun :: TcId
+ -> [TyVar] -> [TcType] -- Quantified type variables and
+ -- their instantiating types
+ -> [([TyVar], ThetaType)] -- Stuff to instantiate
+ -> TcM (HsExpr TcId)
+instFun fun_id qtvs qtv_tys []
+ = return (HsVar fun_id) -- Common short cut
+
+instFun fun_id qtvs qtv_tys tv_theta_prs
+ = do { let subst = zipOpenTvSubst qtvs qtv_tys
+ ty_theta_prs' = map subst_pr tv_theta_prs
+ subst_pr (tvs, theta) = (map (substTyVar subst) tvs,
+ substTheta subst theta)
+
+ -- The ty_theta_prs' is always non-empty
+ ((tys1',theta1') : further_prs') = ty_theta_prs'
+
+ -- First, chuck in the constraints from
+ -- the "stupid theta" of a data constructor (sigh)
+ ; case isDataConId_maybe fun_id of
+ Just con -> tcInstStupidTheta con tys1'
+ Nothing -> return ()
+
+ ; if want_method_inst theta1'
+ then do { meth_id <- newMethodWithGivenTy orig fun_id tys1'
+ -- See Note [Multiple instantiation]
+ ; go (HsVar meth_id) further_prs' }
+ else go (HsVar fun_id) ty_theta_prs'
+ }
+ where
+ orig = OccurrenceOf (idName fun_id)
+
+ go fun [] = return fun
+
+ go fun ((tys, theta) : prs)
+ = do { dicts <- newDicts orig theta
+ ; extendLIEs dicts
+ ; let the_app = unLoc $ mkHsDictApp (mkHsTyApp (noLoc fun) tys)
+ (map instToId dicts)
+ ; go the_app prs }
+
+ -- Hack Alert (want_method_inst)!
+ -- See Note [No method sharing]
+ -- If f :: (%x :: T) => Int -> Int
+ -- Then if we have two separate calls, (f 3, f 4), we cannot
+ -- make a method constraint that then gets shared, thus:
+ -- let m = f %x in (m 3, m 4)
+ -- because that loses the linearity of the constraint.
+ -- The simplest thing to do is never to construct a method constraint
+ -- in the first place that has a linear implicit parameter in it.
+ want_method_inst theta = not (null theta) -- Overloaded
+ && not (any isLinearPred theta) -- Not linear
+ && not opt_NoMethodSharing
+ -- See Note [No method sharing] below
+\end{code}
+
+Note [Multiple instantiation]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We are careful never to make a MethodInst that has, as its meth_id, another MethodInst.
+For example, consider
+ f :: forall a. Eq a => forall b. Ord b => a -> b
+At a call to f, at say [Int, Bool], it's tempting to translate the call to
+
+ f_m1
+ where
+ f_m1 :: forall b. Ord b => Int -> b
+ f_m1 = f Int dEqInt
+
+ f_m2 :: Int -> Bool
+ f_m2 = f_m1 Bool dOrdBool
+
+But notice that f_m2 has f_m1 as its meth_id. Now the danger is that if we do
+a tcSimplCheck with a Given f_mx :: f Int dEqInt, we may make a binding
+ f_m1 = f_mx
+But it's entirely possible that f_m2 will continue to float out, because it
+mentions no type variables. Result, f_m1 isn't in scope.
+
+Here's a concrete example that does this (test tc200):
+
+ class C a where
+ f :: Eq b => b -> a -> Int
+ baz :: Eq a => Int -> a -> Int
+
+ instance C Int where
+ baz = f
+
+Current solution: only do the "method sharing" thing for the first type/dict
+application, not for the iterated ones. A horribly subtle point.
+
+Note [No method sharing]
+~~~~~~~~~~~~~~~~~~~~~~~~
+The -fno-method-sharing flag controls what happens so far as the LIE
+is concerned. The default case is that for an overloaded function we
+generate a "method" Id, and add the Method Inst to the LIE. So you get
+something like
+ f :: Num a => a -> a
+ f = /\a (d:Num a) -> let m = (+) a d in \ (x:a) -> m x x
+If you specify -fno-method-sharing, the dictionary application
+isn't shared, so we get
+ f :: Num a => a -> a
+ f = /\a (d:Num a) (x:a) -> (+) a d x x
+This gets a bit less sharing, but
+ a) it's better for RULEs involving overloaded functions
+ b) perhaps fewer separated lambdas
+
+\begin{code}
tcArgs :: LHsExpr Name -- The function (for error messages)
- -> LHsExpr TcId -- The function (to build into result)
-> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types
- -> TcM (HsExpr TcId) -- Resulting application
+ -> TcM [LHsExpr TcId] -- Resulting args
-tcArgs fun fun' args expected_arg_tys
- = do { args' <- mappM (tcArg fun) (zip3 args expected_arg_tys [1..])
- ; return (unLoc (foldl mkHsApp fun' args')) }
+tcArgs fun args expected_arg_tys
+ = mapM (tcArg fun) (zip3 args expected_arg_tys [1..])
tcArg :: LHsExpr Name -- The function (for error messages)
- -> (LHsExpr Name, TcSigmaType, Int) -- Actual argument and expected arg type
+ -> (LHsExpr Name, BoxySigmaType, Int) -- Actual argument and expected arg type
-> TcM (LHsExpr TcId) -- Resulting argument
-tcArg fun (arg, ty, arg_no) = addErrCtxt (funAppCtxt fun arg arg_no)
- (tcCheckSigma arg ty)
+tcArg fun (arg, ty, arg_no) = addErrCtxt (funAppCtxt fun arg arg_no) $
+ tcPolyExprNC arg ty
-----------------
-tcResult fun args res_ty actual_res_ty
- = addErrCtxtM (checkArgsCtxt fun args res_ty actual_res_ty)
- (tcSubExp res_ty actual_res_ty)
----------------
-- If an error happens we try to figure out whether the
-- function has been given too many or too few arguments,
-- and say so.
--- The ~(Check...) is because in the Infer case the tcSubExp
--- definitely won't fail, so we can be certain we're in the Check branch
-checkArgsCtxt fun args (Infer _) actual_res_ty tidy_env
- = return (tidy_env, ptext SLIT("Urk infer"))
-
-checkArgsCtxt fun args (Check expected_res_ty) actual_res_ty tidy_env
+checkFunResCtxt fun expected_res_ty actual_res_ty tidy_env
= zonkTcType expected_res_ty `thenM` \ exp_ty' ->
zonkTcType actual_res_ty `thenM` \ act_ty' ->
let
len_act_args = length act_args
len_exp_args = length exp_args
- message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun args
- | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun args
- | otherwise = appCtxt fun args
+ message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun
+ | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun
+ | otherwise = empty
in
returnM (env2, message)
-
-----------------
-unifyInfixTy :: LHsExpr Name -> HsExpr Name -> TcType
- -> TcM ([TcType], TcType)
--- This wrapper just prepares the error message for unifyFunTys
-unifyInfixTy op expr op_ty
- = unifyFunTys msg 2 op_ty
- where
- msg = sep [herald <+> quotes (ppr expr),
- ptext SLIT("requires") <+> quotes (ppr op)
- <+> ptext SLIT("to take two arguments")]
- herald = case expr of
- OpApp _ _ _ _ -> ptext SLIT("The infix expression")
- other -> ptext SLIT("The operator section")
\end{code}
%* *
%************************************************************************
-tcId instantiates an occurrence of an Id.
-The instantiate_it loop runs round instantiating the Id.
-It has to be a loop because we are now prepared to entertain
-types like
- f:: forall a. Eq a => forall b. Baz b => tau
-We want to instantiate this to
- f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
+\begin{code}
+lookupFun :: InstOrigin -> Name -> TcM TcId
+lookupFun orig id_name
+ = do { thing <- tcLookup id_name
+ ; case thing of
+ AGlobal (ADataCon con) -> return (dataConWrapId con)
+
+ AGlobal (AnId id)
+ | isNaughtyRecordSelector id -> failWithTc (naughtyRecordSel id)
+ | otherwise -> return id
+ -- A global cannot possibly be ill-staged
+ -- nor does it need the 'lifting' treatment
-The -fno-method-sharing flag controls what happens so far as the LIE
-is concerned. The default case is that for an overloaded function we
-generate a "method" Id, and add the Method Inst to the LIE. So you get
-something like
- f :: Num a => a -> a
- f = /\a (d:Num a) -> let m = (+) a d in \ (x:a) -> m x x
-If you specify -fno-method-sharing, the dictionary application
-isn't shared, so we get
- f :: Num a => a -> a
- f = /\a (d:Num a) (x:a) -> (+) a d x x
-This gets a bit less sharing, but
- a) it's better for RULEs involving overloaded functions
- b) perhaps fewer separated lambdas
+#ifndef GHCI
+ ATcId id th_level _ -> return id -- Non-TH case
+#else
+ ATcId id th_level _ -> do { use_stage <- getStage -- TH case
+ ; thLocalId orig id_name id th_level use_stage }
+#endif
-\begin{code}
-tcId :: InstOrigin -> Name -> TcM (HsExpr TcId, [TcTyVar], TcRhoType)
- -- Return the type variables at which the function
- -- is instantiated, as well as the translated variable and its type
-
-tcId orig id_name -- Look up the Id and instantiate its type
- = tcLookup id_name `thenM` \ thing ->
- case thing of {
- AGlobal (ADataCon con) -- Similar, but instantiate the stupid theta too
- -> do { (expr, tvs, tau) <- instantiate (dataConWrapId con)
- ; tcInstStupidTheta con (mkTyVarTys tvs)
- -- Remember to chuck in the constraints from the "silly context"
- ; return (expr, tvs, tau) }
-
- ; AGlobal (AnId id) | isNaughtyRecordSelector id
- -> failWithTc (naughtyRecordSel id)
- ; AGlobal (AnId id) -> instantiate id
- -- A global cannot possibly be ill-staged
- -- nor does it need the 'lifting' treatment
-
- ; ATcId id th_level -> tc_local_id id th_level
-
- ; other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected"))
+ other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected"))
}
- where
-#ifndef GHCI
- tc_local_id id th_bind_lvl -- Non-TH case
- = instantiate id
-
-#else /* GHCI and TH is on */
- tc_local_id id th_bind_lvl -- TH case
- = -- Check for cross-stage lifting
- getStage `thenM` \ use_stage ->
- case use_stage of
- Brack use_lvl ps_var lie_var
- | use_lvl > th_bind_lvl
- -> if isExternalName id_name then
- -- Top-level identifiers in this module,
- -- (which have External Names)
- -- are just like the imported case:
- -- no need for the 'lifting' treatment
- -- E.g. this is fine:
- -- f x = x
- -- g y = [| f 3 |]
- -- But we do need to put f into the keep-alive
- -- set, because after desugaring the code will
- -- only mention f's *name*, not f itself.
- keepAliveTc id_name `thenM_`
- instantiate id
-
- else -- Nested identifiers, such as 'x' in
- -- E.g. \x -> [| h x |]
- -- We must behave as if the reference to x was
- -- h $(lift x)
- -- We use 'x' itself as the splice proxy, used by
- -- the desugarer to stitch it all back together.
- -- If 'x' occurs many times we may get many identical
- -- bindings of the same splice proxy, but that doesn't
- -- matter, although it's a mite untidy.
- let
- id_ty = idType id
- in
- checkTc (isTauTy id_ty) (polySpliceErr id) `thenM_`
- -- If x is polymorphic, its occurrence sites might
- -- have different instantiations, so we can't use plain
- -- 'x' as the splice proxy name. I don't know how to
- -- solve this, and it's probably unimportant, so I'm
- -- just going to flag an error for now
+#ifdef GHCI /* GHCI and TH is on */
+--------------------------------------
+-- thLocalId : Check for cross-stage lifting
+thLocalId orig id_name id th_bind_lvl (Brack use_lvl ps_var lie_var)
+ | use_lvl > th_bind_lvl
+ = thBrackId orig id_name id ps_var lie_var
+thLocalId orig id_name id th_bind_lvl use_stage
+ = do { checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage
+ ; return id }
+
+--------------------------------------
+thBrackId orig id_name id ps_var lie_var
+ | isExternalName id_name
+ = -- Top-level identifiers in this module,
+ -- (which have External Names)
+ -- are just like the imported case:
+ -- no need for the 'lifting' treatment
+ -- E.g. this is fine:
+ -- f x = x
+ -- g y = [| f 3 |]
+ -- But we do need to put f into the keep-alive
+ -- set, because after desugaring the code will
+ -- only mention f's *name*, not f itself.
+ do { keepAliveTc id_name; return id }
+
+ | otherwise
+ = -- Nested identifiers, such as 'x' in
+ -- E.g. \x -> [| h x |]
+ -- We must behave as if the reference to x was
+ -- h $(lift x)
+ -- We use 'x' itself as the splice proxy, used by
+ -- the desugarer to stitch it all back together.
+ -- If 'x' occurs many times we may get many identical
+ -- bindings of the same splice proxy, but that doesn't
+ -- matter, although it's a mite untidy.
+ do { let id_ty = idType id
+ ; checkTc (isTauTy id_ty) (polySpliceErr id)
+ -- If x is polymorphic, its occurrence sites might
+ -- have different instantiations, so we can't use plain
+ -- 'x' as the splice proxy name. I don't know how to
+ -- solve this, and it's probably unimportant, so I'm
+ -- just going to flag an error for now
- setLIEVar lie_var (
- newMethodFromName orig id_ty DsMeta.liftName `thenM` \ lift ->
- -- Put the 'lift' constraint into the right LIE
+ ; setLIEVar lie_var $ do
+ { lift <- newMethodFromName orig id_ty DsMeta.liftName
+ -- Put the 'lift' constraint into the right LIE
-- Update the pending splices
- readMutVar ps_var `thenM` \ ps ->
- writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps) `thenM_`
-
- returnM (HsVar id, [], id_ty))
+ ; ps <- readMutVar ps_var
+ ; writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
- other ->
- checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage `thenM_`
- instantiate id
+ ; return id } }
#endif /* GHCI */
-
- instantiate :: TcId -> TcM (HsExpr TcId, [TcTyVar], TcRhoType)
- instantiate fun_id
- | not (want_method_inst fun_ty)
- = loop (HsVar fun_id) [] fun_ty
- | otherwise -- Make a MethodInst
- = tcInstType fun_ty `thenM` \ (tyvars, theta, tau) ->
- newMethodWithGivenTy orig fun_id
- (mkTyVarTys tyvars) theta tau `thenM` \ meth_id ->
- loop (HsVar meth_id) tyvars tau
- where
- fun_ty = idType fun_id
-
- -- See Note [Multiple instantiation]
- loop fun tvs fun_ty
- | isSigmaTy fun_ty
- = tcInstCall orig fun_ty `thenM` \ (inst_fn, new_tvs, tau) ->
- loop (inst_fn <$> fun) (tvs ++ new_tvs) tau
-
- | otherwise
- = returnM (fun, tvs, fun_ty)
-
- -- Hack Alert (want_method_inst)!
- -- If f :: (%x :: T) => Int -> Int
- -- Then if we have two separate calls, (f 3, f 4), we cannot
- -- make a method constraint that then gets shared, thus:
- -- let m = f %x in (m 3, m 4)
- -- because that loses the linearity of the constraint.
- -- The simplest thing to do is never to construct a method constraint
- -- in the first place that has a linear implicit parameter in it.
- want_method_inst fun_ty
- | opt_NoMethodSharing = False
- | otherwise = case tcSplitSigmaTy fun_ty of
- (_,[],_) -> False -- Not overloaded
- (_,theta,_) -> not (any isLinearPred theta)
\end{code}
Note [Multiple instantiation]
\begin{code}
tcRecordBinds
:: DataCon
- -> [(FieldLabel,TcType)] -- Expected type for each field
+ -> [TcType] -- Expected type for each field
-> HsRecordBinds Name
-> TcM (HsRecordBinds TcId)
-tcRecordBinds data_con flds_w_tys rbinds
+tcRecordBinds data_con arg_tys rbinds
= do { mb_binds <- mappM do_bind rbinds
; return (catMaybes mb_binds) }
where
+ flds_w_tys = zipEqual "tcRecordBinds" (dataConFieldLabels data_con) arg_tys
do_bind (L loc field_lbl, rhs)
| Just field_ty <- assocMaybe flds_w_tys field_lbl
= addErrCtxt (fieldCtxt field_lbl) $
- do { rhs' <- tcCheckSigma rhs field_ty
+ do { rhs' <- tcPolyExprNC rhs field_ty
; sel_id <- tcLookupId field_lbl
; ASSERT( isRecordSelector sel_id )
return (Just (L loc sel_id, rhs')) }
%************************************************************************
%* *
-\subsection{@tcCheckRhos@ typechecks a {\em list} of expressions}
-%* *
-%************************************************************************
-
-\begin{code}
-tcCheckRhos :: [LHsExpr Name] -> [TcType] -> TcM [LHsExpr TcId]
-
-tcCheckRhos [] [] = returnM []
-tcCheckRhos (expr:exprs) (ty:tys)
- = tcCheckRho expr ty `thenM` \ expr' ->
- tcCheckRhos exprs tys `thenM` \ exprs' ->
- returnM (expr':exprs')
-tcCheckRhos exprs tys = pprPanic "tcCheckRhos" (ppr exprs $$ ppr tys)
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Literals}
-%* *
-%************************************************************************
-
-Overloaded literals.
-
-\begin{code}
-tcLit :: HsLit -> Expected TcRhoType -> TcM (HsExpr TcId)
-tcLit lit res_ty
- = zapExpectedTo res_ty (hsLitType lit) `thenM_`
- returnM (HsLit lit)
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Errors and contexts}
%* *
%************************************************************************
Boring and alphabetical:
\begin{code}
-arithSeqCtxt expr
- = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
-
-parrSeqCtxt expr
- = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr)
-
-caseCtxt expr
- = hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
-
caseScrutCtxt expr
= hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
quotes (ppr fun) <> text ", namely"])
4 (quotes (ppr arg))
-listCtxt expr
- = hang (ptext SLIT("In the list element:")) 4 (ppr expr)
-
-parrCtxt expr
- = hang (ptext SLIT("In the parallel array element:")) 4 (ppr expr)
-
predCtxt expr
= hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
-appCtxt fun args
- = ptext SLIT("In the application") <+> quotes (ppr the_app)
- where
- the_app = foldl mkHsApp fun args -- Used in error messages
-
nonVanillaUpd tycon
= vcat [ptext SLIT("Record update for the non-Haskell-98 data type") <+> quotes (ppr tycon)
<+> ptext SLIT("is not (yet) supported"),
= hang (ptext SLIT("No constructor has all these fields:"))
4 (pprQuotedList (recBindFields rbinds))
-recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr
-recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr
-
naughtyRecordSel sel_id
= ptext SLIT("Cannot use record selector") <+> quotes (ppr sel_id) <+>
ptext SLIT("as a function due to escaped type variables") $$
= ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:")
<+> pprWithCommas ppr fields
-wrongArgsCtxt too_many_or_few fun args
- = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun)
- <+> ptext SLIT("is applied to") <+> text too_many_or_few
- <+> ptext SLIT("arguments in the call"))
- 4 (parens (ppr the_app))
- where
- the_app = foldl mkHsApp fun args -- Used in error messages
+callCtxt fun args
+ = ptext SLIT("In the call") <+> parens (ppr (foldl mkHsApp fun args))
+
+wrongArgsCtxt too_many_or_few fun
+ = ptext SLIT("Probable cause:") <+> quotes (ppr fun)
+ <+> ptext SLIT("is applied to") <+> text too_many_or_few
+ <+> ptext SLIT("arguments")
#ifdef GHCI
polySpliceErr :: Id -> SDoc
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