import TcRnMonad
import Inst ( InstOrigin(..), newDictsAtLoc, newIPDict, instToId )
-import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2, newLocalName, tcLookupLocalIds )
+import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
+ newLocalName, tcLookupLocalIds, pprBinders )
import TcUnify ( Expected(..), tcInfer, checkSigTyVars, sigCtxt )
import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
tcSimplifyToDicts, tcSimplifyIPs )
-- TODO: location a bit awkward, but the mbinds have been
-- dependency analysed and may no longer be adjacent
addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
- generalise is_unres mono_bind_infos tc_ty_sigs lie_req
+ generalise top_lvl is_unres mono_bind_infos tc_ty_sigs lie_req
-- FINALISE THE QUANTIFIED TYPE VARIABLES
-- The quantified type variables often include meta type variables
\end{code}
\begin{code}
-generalise :: Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst]
+generalise :: TopLevelFlag -> Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst]
-> TcM ([TcTyVar], TcDictBinds, [TcId])
-generalise is_unrestricted mono_infos sigs lie_req
+generalise top_lvl is_unrestricted mono_infos sigs lie_req
| not is_unrestricted -- RESTRICTED CASE
= -- Check signature contexts are empty
do { checkTc (all is_mono_sig sigs)
-- Now simplify with exactly that set of tyvars
-- We have to squash those Methods
- ; (qtvs, binds) <- tcSimplifyRestricted doc tau_tvs lie_req
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndr_names
+ tau_tvs lie_req
-- Check that signature type variables are OK
; final_qtvs <- checkSigsTyVars qtvs sigs
genCtxt binder_names
= ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
-
--- Used in error messages
--- Use quotes for a single one; they look a bit "busy" for several
-pprBinders [bndr] = quotes (ppr bndr)
-pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
tcLookup, tcLookupLocated, tcLookupLocalIds,
tcLookupId, tcLookupTyVar,
lclEnvElts, getInLocalScope, findGlobals,
- wrongThingErr,
+ wrongThingErr, pprBinders,
tcExtendRecEnv, -- For knot-tying
import HsSyn ( LRuleDecl, LHsBinds, LSig, pprLHsBinds )
import TcIface ( tcImportDecl )
+import TcRnTypes ( pprTcTyThingCategory )
import TcRnMonad
import TcMType ( zonkTcType, zonkTcTyVarsAndFV )
import TcType ( Type, TcKind, TcTyVar, TcTyVarSet, TcType,
tyVarsOfType, tyVarsOfTypes, tcSplitDFunTy, mkGenTyConApp,
getDFunTyKey, tcTyConAppTyCon, tcGetTyVar, mkTyVarTy,
- tidyOpenType, pprTyThingCategory
+ tidyOpenType
)
import qualified Type ( getTyVar_maybe )
import Id ( idName, isLocalId )
%************************************************************************
\begin{code}
+pprBinders :: [Name] -> SDoc
+-- Used in error messages
+-- Use quotes for a single one; they look a bit "busy" for several
+pprBinders [bndr] = quotes (ppr bndr)
+pprBinders bndrs = pprWithCommas ppr bndrs
+
notFound name
= failWithTc (ptext SLIT("GHC internal error:") <+> quotes (ppr name) <+>
ptext SLIT("is not in scope"))
wrongThingErr expected thing name
- = failWithTc (pp_thing thing <+> quotes (ppr name) <+>
+ = failWithTc (pprTcTyThingCategory thing <+> quotes (ppr name) <+>
ptext SLIT("used as a") <+> text expected)
- where
- pp_thing (AGlobal thing) = pprTyThingCategory thing
- pp_thing (ATyVar _ _) = ptext SLIT("Type variable")
- pp_thing (ATcId _ _ _) = ptext SLIT("Local identifier")
\end{code}
WhereFrom(..), mkModDeps,
-- Typechecker types
- TcTyThing(..), GadtRefinement,
+ TcTyThing(..), pprTcTyThingCategory, GadtRefinement,
-- Template Haskell
ThStage(..), topStage, topSpliceStage,
GenAvailInfo(..), AvailInfo, HscSource(..),
availName, IsBootInterface, Deprecations )
import Packages ( PackageId )
-import Type ( Type, TvSubstEnv, pprParendType )
+import Type ( Type, TvSubstEnv, pprParendType, pprTyThingCategory )
import TcType ( TcTyVarSet, TcType, TcTauType, TcThetaType, SkolemInfo,
TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes )
import InstEnv ( DFunId, InstEnv )
ifPprDebug (brackets (ppr g <> comma <> ppr tl <> comma <> ppr pl))
ppr (ATyVar tv ty) = text "Type variable" <+> quotes (ppr tv) <+> pprParendType ty
ppr (AThing k) = text "AThing" <+> ppr k
+
+pprTcTyThingCategory :: TcTyThing -> SDoc
+pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
+pprTcTyThingCategory (ATyVar _ _) = ptext SLIT("Type variable")
+pprTcTyThingCategory (ATcId _ _ _) = ptext SLIT("Local identifier")
+pprTcTyThingCategory (AThing _) = ptext SLIT("Kinded thing")
\end{code}
\begin{code}
Inst, pprInsts, pprDictsInFull, pprInstInFull, tcGetInstEnvs,
isInheritableInst, pprDFuns, pprDictsTheta
)
-import TcEnv ( tcGetGlobalTyVars, tcLookupId, findGlobals )
+import TcEnv ( tcGetGlobalTyVars, tcLookupId, findGlobals, pprBinders )
import InstEnv ( lookupInstEnv, classInstances )
import TcMType ( zonkTcTyVarsAndFV, tcInstTyVars, checkAmbiguity )
import TcType ( TcTyVar, TcTyVarSet, ThetaType,
tyVarsOfPred, tcEqType, pprPred )
import Id ( idType, mkUserLocal )
import Var ( TyVar )
-import Name ( getOccName, getSrcLoc )
+import Name ( Name, getOccName, getSrcLoc )
import NameSet ( NameSet, mkNameSet, elemNameSet )
import Class ( classBigSig, classKey )
import FunDeps ( oclose, grow, improve, pprEquationDoc )
import Type ( zipTopTvSubst, substTheta, substTy )
import TysWiredIn ( pairTyCon, doubleTy )
import ErrUtils ( Message )
+import BasicTypes ( TopLevelFlag, isNotTopLevel )
import VarSet
import VarEnv ( TidyEnv )
import FiniteMap
we follow the argument of Question 2 and generalise over ?y.
+Question 4: top level
+~~~~~~~~~~~~~~~~~~~~~
+At the top level, monomorhism makes no sense at all.
+
+ module Main where
+ main = let ?x = 5 in print foo
+
+ foo = woggle 3
+
+ woggle :: (?x :: Int) => Int -> Int
+ woggle y = ?x + y
+
+We definitely don't want (foo :: Int) with a top-level implicit parameter
+(?x::Int) becuase there is no way to bind it.
+
Possible choices
~~~~~~~~~~~~~~~~
tcSimplifyRestricted -- Used for restricted binding groups
-- i.e. ones subject to the monomorphism restriction
:: SDoc
+ -> TopLevelFlag
+ -> [Name] -- Things bound in this group
-> TcTyVarSet -- Free in the type of the RHSs
-> [Inst] -- Free in the RHSs
-> TcM ([TcTyVar], -- Tyvars to quantify (zonked)
-- quantify over; by definition there are none.
-- They are all thrown back in the LIE
-tcSimplifyRestricted doc tau_tvs wanteds
+tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds
-- Zonk everything in sight
= mappM zonkInst wanteds `thenM` \ wanteds' ->
zonkTcTyVarsAndFV (varSetElems tau_tvs) `thenM` \ tau_tvs' ->
constrained_tvs = tyVarsOfInsts constrained_dicts
qtvs = (tau_tvs' `minusVarSet` oclose (fdPredsOfInsts constrained_dicts) gbl_tvs')
`minusVarSet` constrained_tvs
- try_me inst | isFreeWrtTyVars qtvs inst = Free
- | otherwise = ReduceMe
in
traceTc (text "tcSimplifyRestricted" <+> vcat [
pprInsts wanteds, pprInsts _frees, pprInsts constrained_dicts,
-- Remember that we may need to do *some* simplification, to
-- (for example) squash {Monad (ST s)} into {}. It's not enough
-- just to float all constraints
+ --
+ -- At top level, we *do* squash methods becuase we want to
+ -- expose implicit parameters to the test that follows
+ let
+ is_nested_group = isNotTopLevel top_lvl
+ try_me inst | isFreeWrtTyVars qtvs inst,
+ (is_nested_group || isDict inst) = Free
+ | otherwise = ReduceMe
+ in
reduceContextWithoutImprovement
doc try_me wanteds' `thenM` \ (frees, binds, irreds) ->
ASSERT( null irreds )
- extendLIEs frees `thenM_`
- returnM (varSetElems qtvs, binds)
+
+ -- See "Notes on implicit parameters, Question 4: top level"
+ if is_nested_group then
+ extendLIEs frees `thenM_`
+ returnM (varSetElems qtvs, binds)
+ else
+ let
+ (non_ips, bad_ips) = partition isClassDict frees
+ in
+ addTopIPErrs bndrs bad_ips `thenM_`
+ extendLIEs non_ips `thenM_`
+ returnM (varSetElems qtvs, binds)
\end{code}
-- Report definite errors
groupErrs (addNoInstanceErrs Nothing []) no_insts `thenM_`
- addTopIPErrs bad_ips `thenM_`
+ strangeTopIPErrs bad_ips `thenM_`
-- Deal with ambiguity errors, but only if
-- if there has not been an error so far; errors often
plural [x] = empty
plural xs = char 's'
-addTopIPErrs dicts
+addTopIPErrs :: [Name] -> [Inst] -> TcM ()
+addTopIPErrs bndrs []
+ = return ()
+addTopIPErrs bndrs ips
+ = addErrTcM (tidy_env, mk_msg tidy_ips)
+ where
+ (tidy_env, tidy_ips) = tidyInsts ips
+ mk_msg ips = vcat [sep [ptext SLIT("Implicit parameters escape from the monomorphic top-level binding(s) of"),
+ pprBinders bndrs <> colon],
+ nest 2 (vcat (map ppr_ip ips)),
+ ptext SLIT("Probably fix: add type signatures for the top-level binding(s)")]
+ ppr_ip ip = pprPred (dictPred ip) <+> pprInstLoc (instLoc ip)
+
+strangeTopIPErrs :: [Inst] -> TcM ()
+strangeTopIPErrs dicts -- Strange, becuase addTopIPErrs should have caught them all
= groupErrs report tidy_dicts
where
(tidy_env, tidy_dicts) = tidyInsts dicts
projects / ghc-hetmet.git / commitdiff