\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcExpr, tcMonoExpr, tcId ) where
+module TcExpr ( tcPolyExpr, tcPolyExprNC,
+ tcMonoExpr, tcInferRho, tcSyntaxOp ) where
#include "HsVersions.h"
-import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..),
- HsMatchContext(..), HsDoContext(..), mkMonoBind
+#ifdef GHCI /* Only if bootstrapped */
+import {-# SOURCE #-} TcSplice( tcSpliceExpr, tcBracket )
+import HsSyn ( nlHsVar )
+import Id ( Id )
+import Name ( isExternalName )
+import TcType ( isTauTy )
+import TcEnv ( checkWellStaged )
+import HsSyn ( nlHsApp )
+import qualified DsMeta
+#endif
+
+import HsSyn ( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields,
+ HsMatchContext(..), HsRecordBinds,
+ mkHsCoerce, mkHsApp, mkHsDictApp, mkHsTyApp )
+import TcHsSyn ( hsLitType )
+import TcRnMonad
+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 RnHsSyn ( RenamedHsExpr, RenamedRecordBinds )
-import TcHsSyn ( TcExpr, TcRecordBinds, simpleHsLitTy )
-
-import TcMonad
-import TcUnify ( tcSub, tcGen, (<$>),
- unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy,
- unifyTupleTy )
-import BasicTypes ( RecFlag(..), isMarkedStrict )
-import Inst ( InstOrigin(..),
- LIE, mkLIE, emptyLIE, unitLIE, plusLIE, plusLIEs,
- newOverloadedLit, newMethod, newIPDict,
- newDicts, newMethodWithGivenTy,
- instToId, tcInstCall
- )
-import TcBinds ( tcBindsAndThen )
-import TcEnv ( tcLookupClass, tcLookupGlobalId, tcLookupGlobal_maybe,
- tcLookupTyCon, tcLookupDataCon, tcLookupId
- )
-import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts )
-import TcMonoType ( tcHsSigType, UserTypeCtxt(..) )
-import TcPat ( badFieldCon )
-import TcSimplify ( tcSimplifyIPs )
-import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy,
- newTyVarTy, newTyVarTys, zonkTcType )
-import TcType ( TcType, TcSigmaType, TcPhiType,
- tcSplitFunTys, tcSplitTyConApp, mkTyVarTys,
- isSigmaTy, mkFunTy, mkAppTy, mkTyConTy,
- mkTyConApp, mkClassPred, tcFunArgTy,
- tyVarsOfTypes, isLinearPred,
- liftedTypeKind, openTypeKind, mkArrowKind,
- tcSplitSigmaTy, tcTyConAppTyCon,
- tidyOpenType
- )
-import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
-import Id ( idType, recordSelectorFieldLabel, isRecordSelector )
-import DataCon ( dataConFieldLabels, dataConSig,
- dataConStrictMarks
+import TcArrows ( tcProc )
+import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, TcMatchCtxt(..) )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
+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 ( argTypeKind )
+
+import Id ( idType, idName, recordSelectorFieldLabel, isRecordSelector,
+ isNaughtyRecordSelector, isDataConId_maybe )
+import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks, dataConSourceArity,
+ dataConWrapId, isVanillaDataCon, dataConTyVars, dataConOrigArgTys )
import Name ( Name )
-import TyCon ( TyCon, tyConTyVars, isAlgTyCon, tyConDataCons )
-import Subst ( mkTopTyVarSubst, substTheta, substTy )
-import VarSet ( emptyVarSet, elemVarSet )
-import TysWiredIn ( boolTy, mkListTy, mkPArrTy, listTyCon, parrTyCon )
-import PrelNames ( cCallableClassName,
- cReturnableClassName,
- enumFromName, enumFromThenName,
+import TyCon ( FieldLabel, tyConStupidTheta, tyConDataCons )
+import Type ( substTheta, substTy )
+import Var ( TyVar, tyVarKind )
+import VarSet ( emptyVarSet, elemVarSet, unionVarSet )
+import TysWiredIn ( boolTy, parrTyCon, tupleTyCon )
+import PrelNames ( enumFromName, enumFromThenName,
enumFromToName, enumFromThenToName,
- enumFromToPName, enumFromThenToPName,
- thenMName, failMName, returnMName, ioTyConName
+ enumFromToPName, enumFromThenToPName, negateName
)
-import Outputable
-import ListSetOps ( minusList )
-import Util
-import CmdLineOpts
+import DynFlags
+import StaticFlags ( opt_NoMethodSharing )
import HscTypes ( TyThing(..) )
+import SrcLoc ( Located(..), unLoc, noLoc, getLoc )
+import Util
+import ListSetOps ( assocMaybe )
+import Maybes ( catMaybes )
+import Outputable
+import FastString
+#ifdef DEBUG
+import TyCon ( tyConArity )
+#endif
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-tcExpr :: RenamedHsExpr -- Expession to type check
- -> TcSigmaType -- Expected type (could be a polytpye)
- -> TcM (TcExpr, LIE) -- Generalised expr with expected type, and LIE
-
-tcExpr expr expected_ty
- | not (isSigmaTy expected_ty) -- Monomorphic case
- = tcMonoExpr expr expected_ty
+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') (mkHsCoerce gen_fn (unLoc expr'))) }
| otherwise
- = tcGen expected_ty emptyVarSet (
- tcMonoExpr expr
- ) `thenTc` \ (gen_fn, expr', lie) ->
- returnTc (gen_fn <$> expr', lie)
+ = 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)
+
+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 expr = tcInfer (tcMonoExpr expr)
\end{code}
-%************************************************************************
-%* *
-\subsection{The TAUT rules for variables}
-%* *
-%************************************************************************
-
-\begin{code}
-tcMonoExpr :: RenamedHsExpr -- Expession to type check
- -> TcPhiType -- Expected type (could be a type variable)
- -- Definitely no foralls at the top
- -- Can be a 'hole'.
- -> TcM (TcExpr, LIE)
-
-tcMonoExpr (HsVar name) res_ty
- = tcId name `thenNF_Tc` \ (expr', lie1, id_ty) ->
- tcSub res_ty id_ty `thenTc` \ (co_fn, lie2) ->
- returnTc (co_fn <$> expr', lie1 `plusLIE` lie2)
-
-tcMonoExpr (HsIPVar ip) res_ty
- = -- Implicit parameters must have a *tau-type* not a
- -- type scheme. We enforce this by creating a fresh
- -- type variable as its type. (Because res_ty may not
- -- be a tau-type.)
- newTyVarTy openTypeKind `thenNF_Tc` \ ip_ty ->
- newIPDict (IPOcc ip) ip ip_ty `thenNF_Tc` \ (ip', inst) ->
- tcSub res_ty ip_ty `thenTc` \ (co_fn, lie) ->
- returnNF_Tc (co_fn <$> HsIPVar ip', lie `plusLIE` unitLIE inst)
-\end{code}
-
%************************************************************************
%* *
-\subsection{Expressions type signatures}
+ tcExpr: the main expression typechecker
%* *
%************************************************************************
\begin{code}
-tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
- = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty ->
- tcExpr expr sig_tc_ty `thenTc` \ (expr', lie1) ->
-
- -- 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
- tcAddErrCtxt (exprSigCtxt in_expr) $
- tcInstCall SignatureOrigin sig_tc_ty `thenNF_Tc` \ (inst_fn, lie2, inst_sig_ty) ->
- tcSub res_ty inst_sig_ty `thenTc` \ (co_fn, lie3) ->
-
- returnTc (co_fn <$> inst_fn expr', lie1 `plusLIE` lie2 `plusLIE` lie3)
+tcExpr :: HsExpr Name -> BoxyRhoType -> TcM (HsExpr TcId)
+tcExpr (HsVar name) res_ty = tcId (OccurrenceOf name) name res_ty
+
+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 (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
+ = 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 (mkHsCoerce 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')) }
+
+tcExpr (HsLam match) res_ty
+ = do { (co_fn, match') <- tcMatchLambda match res_ty
+ ; return (mkHsCoerce co_fn (HsLam match')) }
+
+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 (mkHsCoerce co_fn (ExprWithTySigOut expr' sig_ty)) }
+
+tcExpr (HsType ty) res_ty
+ = failWithTc (text "Can't handle type argument:" <+> ppr ty)
+ -- This is the syntax for type applications that I was planning
+ -- but there are difficulties (e.g. what order for type args)
+ -- so it's not enabled yet.
+ -- Can't eliminate it altogether from the parser, because the
+ -- same parser parses *patterns*.
\end{code}
%************************************************************************
%* *
-\subsection{Other expression forms}
+ Infix operators and sections
%* *
%************************************************************************
\begin{code}
-tcMonoExpr (HsLit lit) res_ty = tcLit lit res_ty
-tcMonoExpr (HsOverLit lit) res_ty = newOverloadedLit (LiteralOrigin lit) lit res_ty
-tcMonoExpr (HsPar expr) res_ty = tcMonoExpr expr 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') }
-tcMonoExpr (NegApp expr neg_name) res_ty
- = tcMonoExpr (HsApp (HsVar neg_name) expr) res_ty
-
-tcMonoExpr (HsLam match) res_ty
- = tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
- returnTc (HsLam match', lie)
-
-tcMonoExpr (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.
-tcMonoExpr in_expr@(SectionL arg1 op) res_ty
- = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
- split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2) ->
- tcAddErrCtxt (exprCtxt in_expr) $
- tcSub res_ty (mkFunTy arg2_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
- returnTc (co_fn <$> SectionL arg1' op', lie1 `plusLIE` lie2 `plusLIE` lie3)
+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
-
-tcMonoExpr in_expr@(SectionR op arg2) res_ty
- = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
- split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2) ->
- tcAddErrCtxt (exprCtxt in_expr) $
- tcSub res_ty (mkFunTy arg1_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
- returnTc (co_fn <$> SectionR op' arg2', lie1 `plusLIE` lie2 `plusLIE` lie3)
-
--- equivalent to (op e1) e2:
-
-tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty
- = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
- split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2a) ->
- tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2b) ->
- tcAddErrCtxt (exprCtxt in_expr) $
- tcSub res_ty op_res_ty `thenTc` \ (co_fn, lie3) ->
- returnTc (OpApp arg1' op' fix arg2',
- lie1 `plusLIE` lie2a `plusLIE` lie2b `plusLIE` lie3)
+
+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 (mkHsCoerce 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}
-The interesting thing about @ccall@ is that it is just a template
-which we instantiate by filling in details about the types of its
-argument and result (ie minimal typechecking is performed). So, the
-basic story is that we allocate a load of type variables (to hold the
-arg/result types); unify them with the args/result; and store them for
-later use.
-
\begin{code}
-tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty
-
- = getDOptsTc `thenNF_Tc` \ dflags ->
-
- checkTc (not (is_casm && dopt_HscLang dflags /= HscC))
- (vcat [text "_casm_ is only supported when compiling via C (-fvia-C).",
- text "Either compile with -fvia-C, or, better, rewrite your code",
- text "to use the foreign function interface. _casm_s are deprecated",
- text "and support for them may one day disappear."])
- `thenTc_`
+tcExpr (HsLet binds expr) res_ty
+ = do { (binds', expr') <- tcLocalBinds binds $
+ tcMonoExpr expr res_ty
+ ; return (HsLet binds' expr') }
+
+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 = tcPolyExpr }
+
+tcExpr (HsIf pred b1 b2) res_ty
+ = 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
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; exprs' <- mappM (tc_elt elt_ty) exprs
+ ; return (ExplicitList elt_ty exprs') }
+ where
+ tc_elt elt_ty expr = tcPolyExpr expr elt_ty
+
+tcExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
+ = 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 = tcPolyExpr expr elt_ty
- -- Get the callable and returnable classes.
- tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
- tcLookupClass cReturnableClassName `thenNF_Tc` \ cReturnableClass ->
- tcLookupTyCon ioTyConName `thenNF_Tc` \ ioTyCon ->
- let
- new_arg_dict (arg, arg_ty)
- = newDicts (CCallOrigin (_UNPK_ lbl) (Just arg))
- [mkClassPred cCallableClass [arg_ty]] `thenNF_Tc` \ arg_dicts ->
- returnNF_Tc arg_dicts -- Actually a singleton bag
+tcExpr (ExplicitTuple exprs boxity) res_ty
+ = do { arg_tys <- boxySplitTyConApp (tupleTyCon boxity (length exprs)) res_ty
+ ; exprs' <- tcPolyExprs exprs arg_tys
+ ; return (ExplicitTuple exprs' boxity) }
- result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -}
- in
+tcExpr (HsProc pat cmd) res_ty
+ = do { (pat', cmd') <- tcProc pat cmd res_ty
+ ; return (HsProc pat' cmd') }
- -- Arguments
- let tv_idxs | null args = []
- | otherwise = [1..length args]
- in
- newTyVarTys (length tv_idxs) openTypeKind `thenNF_Tc` \ arg_tys ->
- tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
+tcExpr e@(HsArrApp _ _ _ _ _) _
+ = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e),
+ ptext SLIT("was found where an expression was expected")])
- -- The argument types can be unlifted or lifted; the result
- -- type must, however, be lifted since it's an argument to the IO
- -- type constructor.
- newTyVarTy liftedTypeKind `thenNF_Tc` \ result_ty ->
- let
- io_result_ty = mkTyConApp ioTyCon [result_ty]
- in
- unifyTauTy res_ty io_result_ty `thenTc_`
-
- -- Construct the extra insts, which encode the
- -- constraints on the argument and result types.
- mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
- newDicts result_origin [mkClassPred cReturnableClass [result_ty]] `thenNF_Tc` \ ccres_dict ->
- returnTc (HsCCall lbl args' may_gc is_casm io_result_ty,
- mkLIE (ccres_dict ++ concat ccarg_dicts_s) `plusLIE` args_lie)
+tcExpr e@(HsArrForm _ _ _) _
+ = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e),
+ ptext SLIT("was found where an expression was expected")])
\end{code}
-\begin{code}
-tcMonoExpr (HsSCC lbl expr) res_ty
- = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
- returnTc (HsSCC lbl expr', lie)
-
-tcMonoExpr (HsLet binds expr) res_ty
- = tcBindsAndThen
- combiner
- binds -- Bindings to check
- tc_expr `thenTc` \ (expr', lie) ->
- returnTc (expr', lie)
- where
- tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
- returnTc (expr', lie)
- combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr
-
-tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (caseCtxt in_expr) $
-
- -- 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
- --
- -- Not only that, but it's better to check the matches on their
- -- own, so that we get the expected results for scoped type variables.
- -- f x = case x of
- -- (p::a, q::b) -> (q,p)
- -- The above should work: the match (p,q) -> (q,p) is polymorphic as
- -- claimed by the pattern signatures. But if we typechecked the
- -- match with x in scope and x's type as the expected type, we'd be hosed.
-
- tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) ->
-
- tcAddErrCtxt (caseScrutCtxt scrut) (
- tcMonoExpr scrut scrut_ty
- ) `thenTc` \ (scrut',lie1) ->
-
- returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
-
-tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (predCtxt pred) (
- tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
-
- tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
- tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
- returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
-\end{code}
+%************************************************************************
+%* *
+ Record construction and update
+%* *
+%************************************************************************
\begin{code}
-tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
- = tcDoStmts do_or_lc stmts src_loc res_ty
-\end{code}
+tcExpr expr@(RecordCon (L loc con_name) _ rbinds) res_ty
+ = do { data_con <- tcLookupDataCon con_name
-\begin{code}
-tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list
- = unifyListTy res_ty `thenTc` \ elt_ty ->
- mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
- returnTc (ExplicitList elt_ty exprs', plusLIEs lies)
- where
- tc_elt elt_ty expr
- = tcAddErrCtxt (listCtxt expr) $
- tcMonoExpr expr elt_ty
-
-tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
- = unifyPArrTy res_ty `thenTc` \ elt_ty ->
- mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
- returnTc (ExplicitPArr elt_ty exprs', plusLIEs lies)
- where
- tc_elt elt_ty expr
- = tcAddErrCtxt (parrCtxt expr) $
- tcMonoExpr expr elt_ty
-
-tcMonoExpr (ExplicitTuple exprs boxity) res_ty
- = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys ->
- mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
- (exprs `zip` arg_tys) -- we know they're of equal length.
- `thenTc` \ (exprs', lies) ->
- returnTc (ExplicitTuple exprs' boxity, plusLIEs lies)
-
-tcMonoExpr expr@(RecordCon con_name rbinds) res_ty
- = tcAddErrCtxt (recordConCtxt expr) $
- tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
- let
- (_, record_ty) = tcSplitFunTys con_tau
- (tycon, ty_args) = tcSplitTyConApp record_ty
- in
- ASSERT( isAlgTyCon tycon )
- unifyTauTy res_ty record_ty `thenTc_`
+ -- Check for missing fields
+ ; checkMissingFields data_con rbinds
- -- Check that the record bindings match the constructor
- -- con_name is syntactically constrained to be a data constructor
- tcLookupDataCon con_name `thenTc` \ data_con ->
- let
- bad_fields = badFields rbinds data_con
- in
- if not (null bad_fields) then
- mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_`
- failTc -- Fail now, because tcRecordBinds will crash on a bad field
- else
+ ; 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
- -- Typecheck the record bindings
- tcRecordBinds tycon ty_args rbinds `thenTc` \ (rbinds', rbinds_lie) ->
-
- let
- (missing_s_fields, missing_fields) = missingFields rbinds data_con
- in
- checkTcM (null missing_s_fields)
- (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_`
- returnNF_Tc ()) `thenNF_Tc_`
- doptsTc Opt_WarnMissingFields `thenNF_Tc` \ warn ->
- checkTcM (not (warn && not (null missing_fields)))
- (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_`
- returnNF_Tc ()) `thenNF_Tc_`
+ ; (con_expr, rbinds') <- tcIdApp con_name arity check_fields res_ty
- returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie)
+ ; returnM (RecordCon (L loc (dataConWrapId data_con)) con_expr rbinds') }
-- The main complication with RecordUpd is that we need to explicitly
-- handle the *non-updated* fields. Consider:
-- its RHS is simply an error, so it doesn't impose any type constraints
--
-- All this is done in STEP 4 below.
+--
+-- Note about GADTs
+-- ~~~~~~~~~~~~~~~~
+-- For record update we require that every constructor involved in the
+-- update (i.e. that has all the specified fields) is "vanilla". I
+-- don't know how to do the update otherwise.
-tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty
- = tcAddErrCtxt (recordUpdCtxt expr) $
- -- STEP 0
+tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty
+ = -- STEP 0
-- Check that the field names are really field names
- ASSERT( not (null rbinds) )
+ ASSERT( notNull rbinds )
let
- field_names = [field_name | (field_name, _, _) <- rbinds]
+ field_names = map fst rbinds
in
- mapNF_Tc tcLookupGlobal_maybe field_names `thenNF_Tc` \ maybe_sel_ids ->
+ mappM (tcLookupGlobalId.unLoc) field_names `thenM` \ sel_ids ->
+ -- The renamer has already checked that they
+ -- are all in scope
let
- bad_guys = [ addErrTc (notSelector field_name)
- | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
- case maybe_sel_id of
- Just (AnId sel_id) -> not (isRecordSelector sel_id)
- other -> True
+ bad_guys = [ setSrcSpan loc $ addErrTc (notSelector field_name)
+ | (L loc field_name, sel_id) <- field_names `zip` sel_ids,
+ not (isRecordSelector sel_id) -- Excludes class ops
]
in
- checkTcM (null bad_guys) (listNF_Tc bad_guys `thenNF_Tc_` failTc) `thenTc_`
+ checkM (null bad_guys) (sequenceM bad_guys `thenM_` failM) `thenM_`
-- STEP 1
-- Figure out the tycon and data cons from the first field name
let
-- It's OK to use the non-tc splitters here (for a selector)
- (Just (AnId sel_id) : _) = maybe_sel_ids
- (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded
- -- when the data type has a context
- data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector
- tycon = tcTyConAppTyCon data_ty
- data_cons = tyConDataCons tycon
- (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons)
+ upd_field_lbls = recBindFields rbinds
+ sel_id : _ = sel_ids
+ (tycon, _) = recordSelectorFieldLabel sel_id -- We've failed already if
+ data_cons = tyConDataCons tycon -- it's not a field label
+ relevant_cons = filter is_relevant data_cons
+ is_relevant con = all (`elem` dataConFieldLabels con) upd_field_lbls
in
- tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
-- STEP 2
-- Check that at least one constructor has all the named fields
-- i.e. has an empty set of bad fields returned by badFields
- checkTc (any (null . badFields rbinds) data_cons)
- (badFieldsUpd rbinds) `thenTc_`
+ checkTc (not (null relevant_cons))
+ (badFieldsUpd rbinds) `thenM_`
- -- STEP 3
- -- Typecheck the update bindings.
- -- (Do this after checking for bad fields in case there's a field that
- -- doesn't match the constructor.)
- let
- result_record_ty = mkTyConApp tycon result_inst_tys
- in
- unifyTauTy res_ty result_record_ty `thenTc_`
- tcRecordBinds tycon result_inst_tys rbinds `thenTc` \ (rbinds', rbinds_lie) ->
+ -- Check that all relevant data cons are vanilla. Doing record updates on
+ -- GADTs and/or existentials is more than my tiny brain can cope with today
+ checkTc (all isVanillaDataCon relevant_cons)
+ (nonVanillaUpd tycon) `thenM_`
-- STEP 4
-- Use the un-updated fields to find a vector of booleans saying
-- WARNING: this code assumes that all data_cons in a common tycon
-- have FieldLabels abstracted over the same tyvars.
let
- upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds']
- con_field_lbls_s = map dataConFieldLabels data_cons
-
-- A constructor is only relevant to this process if
- -- it contains all the fields that are being updated
- relevant_field_lbls_s = filter is_relevant con_field_lbls_s
- is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls
-
- non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls
- common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls)
+ -- it contains *all* the fields that are being updated
+ con1 = head relevant_cons -- A representative constructor
+ con1_tyvars = dataConTyVars con1
+ 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 = 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 ->
- mk_inst_ty (tyvar, result_inst_ty)
- | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
- | otherwise = newTyVarTy liftedTypeKind -- Fresh type
+ -- STEP 3
+ -- Typecheck the update bindings.
+ -- (Do this after checking for bad fields in case there's a field that
+ -- doesn't match the constructor.)
+ let
+ result_record_ty = mkTyConApp tycon result_inst_tys
+ con1_arg_tys' = map (substTy inst_env) con1_arg_tys
in
- mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
+ 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
let
- record_ty = mkTyConApp tycon inst_tys
+ record_ty = ASSERT( length inst_tys == tyConArity tycon )
+ mkTyConApp tycon inst_tys
+ -- This is one place where the isVanilla check is important
+ -- So that inst_tys matches the tycon
in
- tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
+ tcMonoExpr record_expr record_ty `thenM` \ record_expr' ->
-- STEP 6
-- Figure out the LIE we need. We have to generate some
-- dictionaries for the data type context, since we are going to
- -- do some construction.
+ -- do pattern matching over the data cons.
--
- -- What dictionaries do we need? For the moment we assume that all
- -- data constructors have the same context, and grab it from the first
- -- constructor. If they have varying contexts then we'd have to
- -- union the ones that could participate in the update.
+ -- What dictionaries do we need?
+ -- We just take the context of the first data constructor
+ -- This isn't right, but I just can't bear to union up all the relevant ones
let
- (tyvars, theta, _, _, _, _) = dataConSig (head data_cons)
- inst_env = mkTopTyVarSubst tyvars result_inst_tys
- theta' = substTheta inst_env theta
+ theta' = substTheta inst_env (tyConStupidTheta tycon)
in
- newDicts RecordUpdOrigin theta' `thenNF_Tc` \ dicts ->
+ newDicts RecordUpdOrigin theta' `thenM` \ dicts ->
+ extendLIEs dicts `thenM_`
-- Phew!
- returnTc (RecordUpdOut record_expr' record_ty result_record_ty (map instToId dicts) rbinds',
- mkLIE dicts `plusLIE` record_lie `plusLIE` rbinds_lie)
-
-tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
- = unifyListTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
-
- tcLookupGlobalId enumFromName `thenNF_Tc` \ sel_id ->
- newMethod (ArithSeqOrigin seq)
- sel_id [elt_ty] `thenNF_Tc` \ enum_from ->
-
- returnTc (ArithSeqOut (HsVar (instToId enum_from)) (From expr'),
- lie1 `plusLIE` unitLIE enum_from)
-
-tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
- = tcAddErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcLookupGlobalId enumFromThenName `thenNF_Tc` \ sel_id ->
- newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_then ->
-
- returnTc (ArithSeqOut (HsVar (instToId enum_from_then))
- (FromThen expr1' expr2'),
- lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_then)
-
-tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
- = tcAddErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcLookupGlobalId enumFromToName `thenNF_Tc` \ sel_id ->
- newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to ->
-
- returnTc (ArithSeqOut (HsVar (instToId enum_from_to))
- (FromTo expr1' expr2'),
- lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to)
-
-tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = tcAddErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
- tcLookupGlobalId enumFromThenToName `thenNF_Tc` \ sel_id ->
- newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft ->
-
- returnTc (ArithSeqOut (HsVar (instToId eft))
- (FromThenTo expr1' expr2' expr3'),
- lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
-
-tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty
- = tcAddErrCtxt (parrSeqCtxt in_expr) $
- unifyPArrTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcLookupGlobalId enumFromToPName `thenNF_Tc` \ sel_id ->
- newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to ->
-
- returnTc (PArrSeqOut (HsVar (instToId enum_from_to))
- (FromTo expr1' expr2'),
- lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to)
-
-tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = tcAddErrCtxt (parrSeqCtxt in_expr) $
- unifyPArrTy res_ty `thenTc` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
- tcLookupGlobalId enumFromThenToPName `thenNF_Tc` \ sel_id ->
- newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft ->
-
- returnTc (PArrSeqOut (HsVar (instToId eft))
- (FromThenTo expr1' expr2' expr3'),
- lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
-
-tcMonoExpr (PArrSeqIn _) _
- = panic "TcExpr.tcMonoExpr: Infinite parallel array!"
- -- the parser shouldn't have generated it and the renamer shouldn't have
- -- let it through
+ returnM (mkHsCoerce co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty))
\end{code}
+
%************************************************************************
%* *
-\subsection{Implicit Parameter bindings}
+ Arithmetic sequences e.g. [a,b..]
+ and their parallel-array counterparts e.g. [: a,b.. :]
+
%* *
%************************************************************************
\begin{code}
-tcMonoExpr (HsWith expr binds) res_ty
- = tcMonoExpr expr res_ty `thenTc` \ (expr', expr_lie) ->
- mapAndUnzip3Tc tcIPBind binds `thenTc` \ (avail_ips, binds', bind_lies) ->
-
- -- If the binding binds ?x = E, we must now
- -- discharge any ?x constraints in expr_lie
- tcSimplifyIPs avail_ips expr_lie `thenTc` \ (expr_lie', dict_binds) ->
- let
- expr'' = HsLet (mkMonoBind dict_binds [] Recursive) expr'
- in
- returnTc (HsWith expr'' binds', expr_lie' `plusLIE` plusLIEs bind_lies)
-
-tcIPBind (ip, expr)
- = newTyVarTy openTypeKind `thenTc` \ ty ->
- tcGetSrcLoc `thenTc` \ loc ->
- newIPDict (IPBind ip) ip ty `thenNF_Tc` \ (ip', ip_inst) ->
- tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
- returnTc (ip_inst, (ip', expr'), lie)
+tcExpr (ArithSeq _ seq@(From expr)) res_ty
+ = 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
+ = 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
+ = 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
+ = 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
+ = 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
+ = 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!"
+ -- the parser shouldn't have generated it and the renamer shouldn't have
+ -- let it through
\end{code}
+
%************************************************************************
%* *
-\subsection{@tcApp@ typchecks an application}
+ Template Haskell
%* *
%************************************************************************
\begin{code}
+#ifdef GHCI /* Only if bootstrapped */
+ -- Rename excludes these cases otherwise
+tcExpr (HsSpliceE splice) res_ty = tcSpliceExpr splice res_ty
+tcExpr (HsBracket brack) res_ty = do { e <- tcBracket brack res_ty
+ ; return (unLoc e) }
+#endif /* GHCI */
+\end{code}
-tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
- -> TcType -- Expected result type of application
- -> TcM (TcExpr, LIE) -- Translated fun and args
-tcApp (HsApp e1 e2) args res_ty
- = tcApp e1 (e2:args) res_ty -- Accumulate the arguments
+%************************************************************************
+%* *
+ Catch-all
+%* *
+%************************************************************************
-tcApp fun args res_ty
- = -- First type-check the function
- tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
+\begin{code}
+tcExpr other _ = pprPanic "tcMonoExpr" (ppr other)
+\end{code}
- tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
- split_fun_ty fun_ty (length args)
- ) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
- -- Now typecheck the args
- mapAndUnzipTc (tcArg fun)
- (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
+%************************************************************************
+%* *
+ Applications
+%* *
+%************************************************************************
- -- Unify with expected result after type-checking the args
- -- so that the info from args percolates to actual_result_ty.
- -- This is when we might detect a too-few args situation.
- -- (One can think of cases when the opposite order would give
- -- a better error message.)
- tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty)
- (tcSub res_ty actual_result_ty) `thenTc` \ (co_fn, lie_res) ->
+\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 (replicate n_args argTypeKind)
+ ; 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 (replicate n_missing_args argTypeKind)
+ ; 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 (mkHsCoerce co_fn' fun', args') }
+\end{code}
- returnTc (co_fn <$> foldl HsApp fun' args',
- lie_res `plusLIE` lie_fun `plusLIE` plusLIEs lie_args_s)
+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 (mkHsCoerce co_fn fun') }
+
+-- Note [Push result type in]
+--
+-- Unify with expected result before (was: after) type-checking the args
+-- so that the info from res_ty (was: args) percolates to args (was actual_res_ty).
+-- This is when we might detect a too-few args situation.
+-- (One can think of cases when the opposite order would give
+-- a better error message.)
+-- [March 2003: I'm experimenting with putting this first. Here's an
+-- example where it actually makes a real difference
+-- class C t a b | t a -> b
+-- instance C Char a Bool
+--
+-- data P t a = forall b. (C t a b) => MkP b
+-- data Q t = MkQ (forall a. P t a)
--- If an error happens we try to figure out whether the
--- function has been given too many or too few arguments,
--- and say so
-checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
- = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' ->
- zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' ->
- let
- (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
- (env2, act_ty'') = tidyOpenType env1 act_ty'
- (exp_args, _) = tcSplitFunTys exp_ty''
- (act_args, _) = tcSplitFunTys act_ty''
+-- f1, f2 :: Q Char;
+-- f1 = MkQ (MkP True)
+-- f2 = MkQ (MkP True :: forall a. P Char a)
+--
+-- With the change, f1 will type-check, because the 'Char' info from
+-- the signature is propagated into MkQ's argument. With the check
+-- in the other order, the extra signature in f2 is reqd.]
+
+---------------------------
+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)
- len_act_args = length act_args
- len_exp_args = length exp_args
+ go fun [] = return fun
- 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
- in
- returnNF_Tc (env2, message)
+ 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}
-split_fun_ty :: TcType -- The type of the function
- -> Int -- Number of arguments
- -> TcM ([TcType], -- Function argument types
- TcType) -- Function result types
+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
-split_fun_ty fun_ty 0
- = returnTc ([], fun_ty)
+ f_m1
+ where
+ f_m1 :: forall b. Ord b => Int -> b
+ f_m1 = f Int dEqInt
-split_fun_ty fun_ty n
- = -- Expect the function to have type A->B
- unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) ->
- split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) ->
- returnTc (arg_ty:arg_tys, final_res_ty)
-\end{code}
+ f_m2 :: Int -> Bool
+ f_m2 = f_m1 Bool dOrdBool
-\begin{code}
-tcArg :: RenamedHsExpr -- The function (for error messages)
- -> (RenamedHsExpr, TcSigmaType, Int) -- Actual argument and expected arg type
- -> TcM (TcExpr, LIE) -- Resulting argument and LIE
+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.
-tcArg the_fun (arg, expected_arg_ty, arg_no)
- = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
- tcExpr arg expected_arg_ty
-\end{code}
+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
-%************************************************************************
-%* *
-\subsection{@tcId@ typchecks an identifier occurrence}
-%* *
-%************************************************************************
+ instance C Int where
+ baz = f
-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)}
+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
b) perhaps fewer separated lambdas
\begin{code}
-tcId :: Name -> NF_TcM (TcExpr, LIE, TcType)
-tcId name -- Look up the Id and instantiate its type
- = tcLookupId name `thenNF_Tc` \ id ->
- loop (OccurrenceOf id) (HsVar id) emptyLIE (idType id)
- where
- loop orig (HsVar fun_id) lie fun_ty
- | want_method_inst fun_ty
- = tcInstType fun_ty `thenNF_Tc` \ (tyvars, theta, tau) ->
- newMethodWithGivenTy orig fun_id
- (mkTyVarTys tyvars) theta tau `thenNF_Tc` \ meth ->
- loop orig (HsVar (instToId meth))
- (unitLIE meth `plusLIE` lie) tau
-
- loop orig fun lie fun_ty
- | isSigmaTy fun_ty
- = tcInstCall orig fun_ty `thenNF_Tc` \ (inst_fn, inst_lie, tau) ->
- loop orig (inst_fn fun) (inst_lie `plusLIE` lie) tau
-
- | otherwise
- = returnNF_Tc (fun, lie, fun_ty)
-
- want_method_inst fun_ty
- | opt_NoMethodSharing = False
- | otherwise = case tcSplitSigmaTy fun_ty of
- (_,[],_) -> False -- Not overloaded
- (_,theta,_) -> not (any isLinearPred theta)
- -- This is a slight hack.
- -- 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.
-\end{code}
+tcArgs :: LHsExpr Name -- The function (for error messages)
+ -> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types
+ -> TcM [LHsExpr TcId] -- Resulting args
-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 HoleTyVarTy to pass in as the expected tyvar.
+tcArgs fun args expected_arg_tys
+ = mapM (tcArg fun) (zip3 args expected_arg_tys [1..])
-\begin{code}
-tcExpr_id :: RenamedHsExpr -> TcM (TcExpr, LIE, TcType)
-tcExpr_id (HsVar name) = tcId name
-tcExpr_id expr = newHoleTyVarTy `thenNF_Tc` \ id_ty ->
- tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) ->
- returnTc (expr', lie_id, id_ty)
+tcArg :: LHsExpr Name -- The function (for error messages)
+ -> (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) $
+ tcPolyExprNC arg 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.
+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
+ (env1, exp_ty'') = tidyOpenType tidy_env exp_ty'
+ (env2, act_ty'') = tidyOpenType env1 act_ty'
+ (exp_args, _) = tcSplitFunTys exp_ty''
+ (act_args, _) = tcSplitFunTys act_ty''
+
+ len_act_args = length act_args
+ len_exp_args = length exp_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)
\end{code}
%************************************************************************
%* *
-\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
+\subsection{@tcId@ typchecks an identifier occurrence}
%* *
%************************************************************************
\begin{code}
--- I don't like this lumping together of do expression and list/array
--- comprehensions; creating the monad instances is entirely pointless in the
--- latter case; I'll leave the list case as it is for the moment, but handle
--- arrays extra (would be better to handle arrays and lists together, though)
--- -=chak
---
-tcDoStmts PArrComp stmts src_loc res_ty
- =
- ASSERT( not (null stmts) )
- tcAddSrcLoc src_loc $
-
- unifyPArrTy res_ty `thenTc` \elt_ty ->
- let tc_ty = mkTyConTy parrTyCon
- m_ty = (mkPArrTy, elt_ty)
- in
- tcStmts (DoCtxt PArrComp) m_ty stmts `thenTc` \(stmts', stmts_lie) ->
- returnTc (HsDoOut PArrComp stmts'
- undefined undefined undefined -- don't touch!
- res_ty src_loc,
- stmts_lie)
-
-tcDoStmts do_or_lc stmts src_loc res_ty
- = -- get the Monad and MonadZero classes
- -- create type consisting of a fresh monad tyvar
- ASSERT( not (null stmts) )
- tcAddSrcLoc src_loc $
-
- -- If it's a comprehension we're dealing with,
- -- force it to be a list comprehension.
- -- (as of Haskell 98, monad comprehensions are no more.)
- -- Similarily, array comprehensions must involve parallel arrays types
- -- -=chak
- (case do_or_lc of
- ListComp -> unifyListTy res_ty `thenTc` \ elt_ty ->
- returnNF_Tc (mkTyConTy listTyCon, (mkListTy, elt_ty))
-
- PArrComp -> panic "TcExpr.tcDoStmts: How did we get here?!?"
-
- _ -> newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenNF_Tc` \ m_ty ->
- newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty ->
- unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenTc_`
- returnNF_Tc (m_ty, (mkAppTy m_ty, elt_ty))
- ) `thenNF_Tc` \ (tc_ty, m_ty) ->
-
- tcStmts (DoCtxt do_or_lc) m_ty stmts `thenTc` \ (stmts', stmts_lie) ->
-
- -- 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.
- --
- tcLookupGlobalId returnMName `thenNF_Tc` \ return_sel_id ->
- tcLookupGlobalId thenMName `thenNF_Tc` \ then_sel_id ->
- tcLookupGlobalId failMName `thenNF_Tc` \ fail_sel_id ->
- newMethod DoOrigin return_sel_id [tc_ty] `thenNF_Tc` \ return_inst ->
- newMethod DoOrigin then_sel_id [tc_ty] `thenNF_Tc` \ then_inst ->
- newMethod DoOrigin fail_sel_id [tc_ty] `thenNF_Tc` \ fail_inst ->
- let
- monad_lie = mkLIE [return_inst, then_inst, fail_inst]
- in
- returnTc (HsDoOut do_or_lc stmts'
- (instToId return_inst) (instToId then_inst) (instToId fail_inst)
- res_ty src_loc,
- stmts_lie `plusLIE` monad_lie)
+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
+
+#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
+
+ other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected"))
+ }
+
+#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
+
+ ; id_ty' <- zapToMonotype id_ty
+ -- The id_ty might have an OpenTypeKind, but we
+ -- can't instantiate the Lift class at that kind,
+ -- so we zap it to a LiftedTypeKind monotype
+ -- C.f. the call in TcPat.newLitInst
+
+ ; setLIEVar lie_var $ do
+ { lift <- newMethodFromName orig id_ty' DsMeta.liftName
+ -- Put the 'lift' constraint into the right LIE
+
+ -- Update the pending splices
+ ; ps <- readMutVar ps_var
+ ; writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
+
+ ; return id } }
+#endif /* GHCI */
\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.
+
%************************************************************************
%* *
\begin{code}
tcRecordBinds
- :: TyCon -- Type constructor for the record
- -> [TcType] -- Args of this type constructor
- -> RenamedRecordBinds
- -> TcM (TcRecordBinds, LIE)
-
-tcRecordBinds tycon ty_args rbinds
- = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) ->
- returnTc (rbinds', plusLIEs lies)
- where
- tenv = mkTopTyVarSubst (tyConTyVars tycon) ty_args
-
- do_bind (field_lbl_name, rhs, pun_flag)
- = tcLookupGlobalId field_lbl_name `thenNF_Tc` \ sel_id ->
- let
- field_lbl = recordSelectorFieldLabel sel_id
- field_ty = substTy tenv (fieldLabelType field_lbl)
- in
- ASSERT( isRecordSelector sel_id )
- -- This lookup and assertion will surely succeed, because
- -- we check that the fields are indeed record selectors
- -- before calling tcRecordBinds
- ASSERT2( fieldLabelTyCon field_lbl == tycon, ppr field_lbl )
- -- The caller of tcRecordBinds has already checked
- -- that all the fields come from the same type
-
- tcExpr rhs field_ty `thenTc` \ (rhs', lie) ->
-
- returnTc ((sel_id, rhs', pun_flag), lie)
-
-badFields rbinds data_con
- = [field_name | (field_name, _, _) <- rbinds,
- not (field_name `elem` field_names)
- ]
+ :: DataCon
+ -> [TcType] -- Expected type for each field
+ -> HsRecordBinds Name
+ -> TcM (HsRecordBinds TcId)
+
+tcRecordBinds data_con arg_tys rbinds
+ = do { mb_binds <- mappM do_bind rbinds
+ ; return (catMaybes mb_binds) }
where
- field_names = map fieldLabelName (dataConFieldLabels data_con)
+ 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' <- tcPolyExprNC rhs field_ty
+ ; sel_id <- tcLookupId field_lbl
+ ; ASSERT( isRecordSelector sel_id )
+ return (Just (L loc sel_id, rhs')) }
+ | otherwise
+ = do { addErrTc (badFieldCon data_con field_lbl)
+ ; return Nothing }
+
+checkMissingFields :: DataCon -> HsRecordBinds Name -> TcM ()
+checkMissingFields data_con rbinds
+ | null field_labels -- Not declared as a record;
+ -- But C{} is still valid if no strict fields
+ = if any isMarkedStrict field_strs then
+ -- Illegal if any arg is strict
+ addErrTc (missingStrictFields data_con [])
+ else
+ returnM ()
+
+ | otherwise -- A record
+ = checkM (null missing_s_fields)
+ (addErrTc (missingStrictFields data_con missing_s_fields)) `thenM_`
+
+ doptM Opt_WarnMissingFields `thenM` \ warn ->
+ checkM (not (warn && notNull missing_ns_fields))
+ (warnTc True (missingFields data_con missing_ns_fields))
-missingFields rbinds data_con
- | null field_labels = ([], []) -- Not declared as a record;
- -- But C{} is still valid
- | otherwise
- = (missing_strict_fields, other_missing_fields)
where
- missing_strict_fields
+ missing_s_fields
= [ fl | (fl, str) <- field_info,
isMarkedStrict str,
- not (fieldLabelName fl `elem` field_names_used)
+ not (fl `elem` field_names_used)
]
- other_missing_fields
+ missing_ns_fields
= [ fl | (fl, str) <- field_info,
not (isMarkedStrict str),
- not (fieldLabelName fl `elem` field_names_used)
+ not (fl `elem` field_names_used)
]
- field_names_used = [ field_name | (field_name, _, _) <- rbinds ]
+ field_names_used = recBindFields rbinds
field_labels = dataConFieldLabels data_con
field_info = zipEqual "missingFields"
field_labels
- (dropList ex_theta (dataConStrictMarks data_con))
- -- The 'drop' is because dataConStrictMarks
- -- includes the existential dictionaries
- (_, _, _, ex_theta, _, _) = dataConSig data_con
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
-%* *
-%************************************************************************
-
-\begin{code}
-tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM ([TcExpr], LIE)
-
-tcMonoExprs [] [] = returnTc ([], emptyLIE)
-tcMonoExprs (expr:exprs) (ty:tys)
- = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
- tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
- returnTc (expr':exprs', lie1 `plusLIE` lie2)
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{Literals}
-%* *
-%************************************************************************
+ field_strs
-Overloaded literals.
-
-\begin{code}
-tcLit :: HsLit -> TcType -> TcM (TcExpr, LIE)
-tcLit (HsLitLit s _) res_ty
- = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
- newDicts (LitLitOrigin (_UNPK_ s))
- [mkClassPred cCallableClass [res_ty]] `thenNF_Tc` \ dicts ->
- returnTc (HsLit (HsLitLit s res_ty), mkLIE dicts)
-
-tcLit lit res_ty
- = unifyTauTy res_ty (simpleHsLitTy lit) `thenTc_`
- returnTc (HsLit lit, emptyLIE)
+ field_strs = dataConStrictMarks data_con
\end{code}
-
%************************************************************************
%* *
\subsection{Errors and contexts}
%* *
%************************************************************************
-Mini-utils:
-
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)
-exprSigCtxt expr
- = hang (ptext SLIT("When checking the type signature of the expression:"))
- 4 (ppr expr)
-
-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)
-
exprCtxt expr
= hang (ptext SLIT("In the expression:")) 4 (ppr expr)
+fieldCtxt field_name
+ = ptext SLIT("In the") <+> quotes (ppr field_name) <+> ptext SLIT("field of a record")
+
funAppCtxt fun arg arg_no
= hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
quotes (ppr fun) <> text ", namely"])
4 (quotes (ppr arg))
-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 HsApp fun args -- Used in error messages
-
-appCtxt fun args
- = ptext SLIT("In the application") <+> quotes (ppr the_app)
- where
- the_app = foldl HsApp fun args -- Used in error messages
-
-lurkingRank2Err fun fun_ty
- = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)])
- 4 (vcat [ptext SLIT("It is applied to too few arguments"),
- ptext SLIT("so that the result type has for-alls in it:") <+> ppr fun_ty])
+predCtxt expr
+ = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
+nonVanillaUpd tycon
+ = vcat [ptext SLIT("Record update for the non-Haskell-98 data type") <+> quotes (ppr tycon)
+ <+> ptext SLIT("is not (yet) supported"),
+ ptext SLIT("Use pattern-matching instead")]
badFieldsUpd rbinds
= hang (ptext SLIT("No constructor has all these fields:"))
- 4 (pprQuotedList fields)
- where
- fields = [field | (field, _, _) <- rbinds]
+ 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("Probably fix: use pattern-matching syntax instead")
notSelector field
= hsep [quotes (ppr field), ptext SLIT("is not a record selector")]
-missingStrictFieldCon :: Name -> FieldLabel -> SDoc
-missingStrictFieldCon con field
- = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
- ptext SLIT("does not have the required strict field"), quotes (ppr field)]
-
-missingFieldCon :: Name -> FieldLabel -> SDoc
-missingFieldCon con field
- = hsep [ptext SLIT("Field") <+> quotes (ppr field),
- ptext SLIT("is not initialised")]
+missingStrictFields :: DataCon -> [FieldLabel] -> SDoc
+missingStrictFields con fields
+ = header <> rest
+ where
+ rest | null fields = empty -- Happens for non-record constructors
+ -- with strict fields
+ | otherwise = colon <+> pprWithCommas ppr fields
+
+ header = ptext SLIT("Constructor") <+> quotes (ppr con) <+>
+ ptext SLIT("does not have the required strict field(s)")
+
+missingFields :: DataCon -> [FieldLabel] -> SDoc
+missingFields con fields
+ = ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:")
+ <+> pprWithCommas ppr fields
+
+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
+polySpliceErr id
+ = ptext SLIT("Can't splice the polymorphic local variable") <+> quotes (ppr id)
+#endif
\end{code}
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