\section[TcBinds]{TcBinds}
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
--- for details
-
module TcBinds ( tcLocalBinds, tcTopBinds,
- tcHsBootSigs, tcMonoBinds,
- TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
- TcSigInfo(..), TcSigFun, mkTcSigFun,
- badBootDeclErr ) where
-
-#include "HsVersions.h"
+ tcHsBootSigs, tcPolyBinds,
+ PragFun, tcSpecPrags, mkPragFun,
+ TcSigInfo(..), SigFun, mkSigFun,
+ badBootDeclErr ) where
import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
import {-# SOURCE #-} TcExpr ( tcMonoExpr )
import DynFlags
import HsSyn
-import TcHsSyn
import TcRnMonad
-import Inst
import TcEnv
import TcUnify
import TcSimplify
import TcPat
import TcMType
import TcType
-import {- Kind parts of -} Type
+import RnBinds( misplacedSigErr )
import Coercion
-import VarEnv
import TysPrim
import Id
-import IdInfo
-import Var ( TyVar )
+import Var
import Name
import NameSet
import NameEnv
import ErrUtils
import Digraph
import Maybes
-import List
import Util
import BasicTypes
import Outputable
+import FastString
+
+import Data.List( partition )
+import Control.Monad
+
+#include "HsVersions.h"
\end{code}
%************************************************************************
-%* *
+%* *
\subsection{Type-checking bindings}
-%* *
+%* *
%************************************************************************
@tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
dictionaries, which we resolve at the module level.
\begin{code}
-tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
- -- Note: returning the TcLclEnv is more than we really
- -- want. The bit we care about is the local bindings
- -- and the free type variables thereof
+tcTopBinds :: HsValBinds Name
+ -> TcM ( LHsBinds TcId -- Typechecked bindings
+ , [LTcSpecPrag] -- SPECIALISE prags for imported Ids
+ , TcLclEnv) -- Augmented environment
+
+ -- Note: returning the TcLclEnv is more than we really
+ -- want. The bit we care about is the local bindings
+ -- and the free type variables thereof
tcTopBinds binds
- = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
- ; return (foldr (unionBags . snd) emptyBag prs, env) }
- -- The top level bindings are flattened into a giant
- -- implicitly-mutually-recursive LHsBinds
+ = do { (ValBindsOut prs sigs, env) <- tcValBinds TopLevel binds getLclEnv
+ ; let binds = foldr (unionBags . snd) emptyBag prs
+ ; specs <- tcImpPrags sigs
+ ; return (binds, specs, env) }
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive LHsBinds
tcHsBootSigs :: HsValBinds Name -> TcM [Id]
-- A hs-boot file has only one BindGroup, and it only has type
-- signatures in it. The renamer checked all this
tcHsBootSigs (ValBindsOut binds sigs)
- = do { checkTc (null binds) badBootDeclErr
- ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
+ = do { checkTc (null binds) badBootDeclErr
+ ; mapM (addLocM tc_boot_sig) (filter isTypeLSig sigs) }
where
tc_boot_sig (TypeSig (L _ name) ty)
= do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
- ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
- -- Notice that we make GlobalIds, not LocalIds
+ ; return (mkVanillaGlobal name sigma_ty) }
+ -- Notice that we make GlobalIds, not LocalIds
+ tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
badBootDeclErr :: Message
-badBootDeclErr = ptext SLIT("Illegal declarations in an hs-boot file")
+badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
------------------------
tcLocalBinds :: HsLocalBinds Name -> TcM thing
- -> TcM (HsLocalBinds TcId, thing)
+ -> TcM (HsLocalBinds TcId, thing)
tcLocalBinds EmptyLocalBinds thing_inside
- = do { thing <- thing_inside
- ; return (EmptyLocalBinds, thing) }
+ = do { thing <- thing_inside
+ ; return (EmptyLocalBinds, thing) }
tcLocalBinds (HsValBinds binds) thing_inside
- = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
- ; return (HsValBinds binds', thing) }
+ = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
+ ; return (HsValBinds binds', thing) }
tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
- = do { (thing, lie) <- getLIE thing_inside
- ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
+ = do { (given_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
- -- If the binding binds ?x = E, we must now
- -- discharge any ?x constraints in expr_lie
- ; dict_binds <- tcSimplifyIPs avail_ips lie
- ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ -- See Note [Implicit parameter untouchables]
+ ; (ev_binds, result) <- checkConstraints (IPSkol ips)
+ [] given_ips thing_inside
+
+ ; return (HsIPBinds (IPBinds ip_binds' ev_binds), result) }
where
- -- I wonder if we should do these one at at time
- -- Consider ?x = 4
- -- ?y = ?x + 1
- tc_ip_bind (IPBind ip expr)
- = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
- newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
- tcMonoExpr expr ty `thenM` \ expr' ->
- returnM (ip_inst, (IPBind ip' expr'))
+ ips = [ip | L _ (IPBind ip _) <- ip_binds]
+
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (IPBind ip expr)
+ = do { ty <- newFlexiTyVarTy argTypeKind
+ ; ip_id <- newIP ip ty
+ ; expr' <- tcMonoExpr expr ty
+ ; return (ip_id, (IPBind (IPName ip_id) expr')) }
+\end{code}
-------------------------
+Note [Implicit parameter untouchables]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We add the type variables in the types of the implicit parameters
+as untouchables, not so much because we really must not unify them,
+but rather because we otherwise end up with constraints like this
+ Num alpha, Implic { wanted = alpha ~ Int }
+The constraint solver solves alpha~Int by unification, but then
+doesn't float that solved constraint out (it's not an unsolved
+wanted. Result disaster: the (Num alpha) is again solved, this
+time by defaulting. No no no.
+
+However [Oct 10] this is all handled automatically by the
+untouchable-range idea.
+
+\begin{code}
tcValBinds :: TopLevelFlag
- -> HsValBinds Name -> TcM thing
- -> TcM (HsValBinds TcId, thing)
+ -> HsValBinds Name -> TcM thing
+ -> TcM (HsValBinds TcId, thing)
-tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside
+tcValBinds _ (ValBindsIn binds _) _
= pprPanic "tcValBinds" (ppr binds)
tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
- = do { -- Typecheck the signature
- ; let { prag_fn = mkPragFun sigs
- ; ty_sigs = filter isVanillaLSig sigs
- ; sig_fn = mkTcSigFun ty_sigs }
-
- ; poly_ids <- mapM tcTySig ty_sigs
- -- No recovery from bad signatures, because the type sigs
- -- may bind type variables, so proceeding without them
- -- can lead to a cascade of errors
- -- ToDo: this means we fall over immediately if any type sig
- -- is wrong, which is over-conservative, see Trac bug #745
-
- -- Extend the envt right away with all
- -- the Ids declared with type signatures
- ; poly_rec <- doptM Opt_RelaxedPolyRec
- ; (binds', thing) <- tcExtendIdEnv poly_ids $
- tc_val_binds poly_rec top_lvl sig_fn prag_fn
- binds thing_inside
-
- ; return (ValBindsOut binds' sigs, thing) }
+ = do { -- Typecheck the signature
+ ; let { prag_fn = mkPragFun sigs (foldr (unionBags . snd) emptyBag binds)
+ ; ty_sigs = filter isTypeLSig sigs
+ ; sig_fn = mkSigFun ty_sigs }
+
+ ; poly_ids <- checkNoErrs (mapAndRecoverM tcTySig ty_sigs)
+ -- No recovery from bad signatures, because the type sigs
+ -- may bind type variables, so proceeding without them
+ -- can lead to a cascade of errors
+ -- ToDo: this means we fall over immediately if any type sig
+ -- is wrong, which is over-conservative, see Trac bug #745
+
+ -- Extend the envt right away with all
+ -- the Ids declared with type signatures
+ ; (binds', thing) <- tcExtendIdEnv poly_ids $
+ tcBindGroups top_lvl sig_fn prag_fn
+ binds thing_inside
+
+ ; return (ValBindsOut binds' sigs, thing) }
------------------------
-tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
- -> [(RecFlag, LHsBinds Name)] -> TcM thing
- -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+tcBindGroups :: TopLevelFlag -> SigFun -> PragFun
+ -> [(RecFlag, LHsBinds Name)] -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
-- Typecheck a whole lot of value bindings,
-- one strongly-connected component at a time
+-- Here a "strongly connected component" has the strightforward
+-- meaning of a group of bindings that mention each other,
+-- ignoring type signatures (that part comes later)
-tc_val_binds poly_rec top_lvl sig_fn prag_fn [] thing_inside
- = do { thing <- thing_inside
- ; return ([], thing) }
+tcBindGroups _ _ _ [] thing_inside
+ = do { thing <- thing_inside
+ ; return ([], thing) }
-tc_val_binds poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside
- = do { (group', (groups', thing))
- <- tc_group poly_rec top_lvl sig_fn prag_fn group $
- tc_val_binds poly_rec top_lvl sig_fn prag_fn groups thing_inside
- ; return (group' ++ groups', thing) }
+tcBindGroups top_lvl sig_fn prag_fn (group : groups) thing_inside
+ = do { (group', (groups', thing))
+ <- tc_group top_lvl sig_fn prag_fn group $
+ tcBindGroups top_lvl sig_fn prag_fn groups thing_inside
+ ; return (group' ++ groups', thing) }
------------------------
-tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
- -> (RecFlag, LHsBinds Name) -> TcM thing
- -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+tc_group :: forall thing.
+ TopLevelFlag -> SigFun -> PragFun
+ -> (RecFlag, LHsBinds Name) -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
-- Typecheck one strongly-connected component of the original program.
-- We get a list of groups back, because there may
-- be specialisations etc as well
-tc_group poly_rec top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
- -- A single non-recursive binding
- -- We want to keep non-recursive things non-recursive
+tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
+ -- A single non-recursive binding
+ -- We want to keep non-recursive things non-recursive
-- so that we desugar unlifted bindings correctly
- = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside
- ; return ([(NonRecursive, b) | b <- binds], thing) }
-
-tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
- | not poly_rec -- Recursive group, normal Haskell 98 route
- = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
- ; return ([(Recursive, unionManyBags binds1)], thing) }
-
- | otherwise -- Recursive group, with gla-exts
- = -- To maximise polymorphism (with -fglasgow-exts), we do a new
- -- strongly-connected-component analysis, this time omitting
- -- any references to variables with type signatures.
- --
- -- Notice that the bindInsts thing covers *all* the bindings in the original
- -- group at once; an earlier one may use a later one!
- do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
- ; (binds1,thing) <- bindLocalInsts top_lvl $
- go (stronglyConnComp (mkEdges sig_fn binds))
- ; return ([(Recursive, unionManyBags binds1)], thing) }
- -- Rec them all together
+ = do { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn NonRecursive NonRecursive
+ (bagToList binds)
+ ; thing <- tcExtendIdEnv ids thing_inside
+ ; return ( [(NonRecursive, binds1)], thing) }
+
+tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
+ = -- To maximise polymorphism (assumes -XRelaxedPolyRec), we do a new
+ -- strongly-connected-component analysis, this time omitting
+ -- any references to variables with type signatures.
+ do { traceTc "tc_group rec" (pprLHsBinds binds)
+ ; (binds1, _ids, thing) <- go sccs
+ -- Here is where we should do bindInstsOfLocalFuns
+ -- if we start having Methods again
+ ; return ([(Recursive, binds1)], thing) }
+ -- Rec them all together
where
--- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing)
- go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
- ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
- ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
- go [] = do { thing <- thing_inside; return ([], [], thing) }
+ sccs :: [SCC (LHsBind Name)]
+ sccs = stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds)
- tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
- tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
+ go :: [SCC (LHsBind Name)] -> TcM (LHsBinds TcId, [TcId], thing)
+ go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
+ ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
+ ; return (binds1 `unionBags` binds2, ids1 ++ ids2, thing) }
+ go [] = do { thing <- thing_inside; return (emptyBag, [], thing) }
+
+ tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive [bind]
+ tc_scc (CyclicSCC binds) = tc_sub_group Recursive binds
tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
-tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
- = bindLocalInsts top_lvl $ do
- { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
- ; thing <- tcExtendIdEnv ids thing_inside
- ; return (binds1, ids, thing) }
------------------------
-bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
+{-
+bindLocalInsts :: TopLevelFlag
+ -> TcM (LHsBinds TcId, [TcId], a)
+ -> TcM (LHsBinds TcId, TcEvBinds, a)
bindLocalInsts top_lvl thing_inside
- | isTopLevel top_lvl = do { (binds, ids, thing) <- thing_inside; return (binds, thing) }
- -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
- -- All the top level things are rec'd together anyway, so it's fine to
- -- leave them to the tcSimplifyTop, and quite a bit faster too
-
- | otherwise -- Nested case
- = do { ((binds, ids, thing), lie) <- getLIE thing_inside
- ; lie_binds <- bindInstsOfLocalFuns lie ids
- ; return (binds ++ [lie_binds], thing) }
+ | isTopLevel top_lvl
+ = do { (binds, _, thing) <- thing_inside; return (binds, emptyBag, thing) }
+ -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
+ -- All the top level things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+
+ | otherwise -- Nested case
+ = do { ((binds, ids, thing), lie) <- captureConstraints thing_inside
+ ; lie_binds <- bindLocalMethods lie ids
+ ; return (binds, lie_binds, thing) }
+-}
------------------------
-mkEdges :: TcSigFun -> LHsBinds Name
- -> [(LHsBind Name, BKey, [BKey])]
+mkEdges :: SigFun -> LHsBinds Name
+ -> [(LHsBind Name, BKey, [BKey])]
type BKey = Int -- Just number off the bindings
mkEdges sig_fn binds
= [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
- Just key <- [lookupNameEnv key_map n], no_sig n ])
+ Just key <- [lookupNameEnv key_map n], no_sig n ])
| (bind, key) <- keyd_binds
]
where
keyd_binds = bagToList binds `zip` [0::BKey ..]
- key_map :: NameEnv BKey -- Which binding it comes from
+ key_map :: NameEnv BKey -- Which binding it comes from
key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
- , bndr <- bindersOfHsBind bind ]
+ , bndr <- bindersOfHsBind bind ]
bindersOfHsBind :: HsBind Name -> [Name]
bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
+bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
+bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
------------------------
-tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
- -> RecFlag -- Whether the group is really recursive
- -> RecFlag -- Whether it's recursive after breaking
- -- dependencies based on type signatures
- -> LHsBinds Name
- -> TcM ([LHsBinds TcId], [TcId])
+tcPolyBinds :: TopLevelFlag -> SigFun -> PragFun
+ -> RecFlag -- Whether the group is really recursive
+ -> RecFlag -- Whether it's recursive after breaking
+ -- dependencies based on type signatures
+ -> [LHsBind Name]
+ -> TcM (LHsBinds TcId, [TcId])
-- Typechecks a single bunch of bindings all together,
-- and generalises them. The bunch may be only part of a recursive
--
-- Knows nothing about the scope of the bindings
-tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
- = let
- bind_list = bagToList binds
- binder_names = collectHsBindBinders binds
- loc = getLoc (head bind_list)
- -- TODO: location a bit awkward, but the mbinds have been
- -- dependency analysed and may no longer be adjacent
- in
- -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
- setSrcSpan loc $
- recoverM (recoveryCode binder_names sig_fn) $ do
-
- { traceTc (ptext SLIT("------------------------------------------------"))
- ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
-
- -- TYPECHECK THE BINDINGS
- ; ((binds', mono_bind_infos), lie_req)
- <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
- ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req))
-
- -- CHECK FOR UNLIFTED BINDINGS
- -- These must be non-recursive etc, and are not generalised
- -- They desugar to a case expression in the end
- ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
- ; is_strict <- checkStrictBinds top_lvl rec_group binds'
- zonked_mono_tys mono_bind_infos
- ; if is_strict then
- do { extendLIEs lie_req
- ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
- mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
- mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, [])
- -- ToDo: prags for unlifted bindings
-
- ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
- [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
-
- else do -- The normal lifted case: GENERALISE
- { dflags <- getDOpts
- ; (tyvars_to_gen, dicts, dict_binds)
- <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
- generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
-
- -- BUILD THE POLYMORPHIC RESULT IDs
- ; let dict_ids = map instToId dicts
- ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map idType dict_ids))
- mono_bind_infos
-
- ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
- ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
-
- ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
- dict_ids exports
- (dict_binds `unionBags` binds')
-
- ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
- } }
+tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc bind_list
+ = setSrcSpan loc $
+ recoverM (recoveryCode binder_names sig_fn) $ do
+ -- Set up main recoer; take advantage of any type sigs
+
+ { traceTc "------------------------------------------------" empty
+ ; traceTc "Bindings for" (ppr binder_names)
+
+ ; tc_sig_fn <- tcInstSigs sig_fn binder_names
+
+ ; dflags <- getDOpts
+ ; let plan = decideGeneralisationPlan dflags top_lvl binder_names bind_list tc_sig_fn
+ ; traceTc "Generalisation plan" (ppr plan)
+ ; (binds, poly_ids) <- case plan of
+ NoGen -> tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
+ InferGen mono -> tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_tc bind_list
+ CheckGen sig -> tcPolyCheck sig prag_fn rec_tc bind_list
+
+ -- Check whether strict bindings are ok
+ -- These must be non-recursive etc, and are not generalised
+ -- They desugar to a case expression in the end
+ ; checkStrictBinds top_lvl rec_group bind_list poly_ids
+
+ ; return (binds, poly_ids) }
+ where
+ binder_names = collectHsBindListBinders bind_list
+ loc = getLoc (head bind_list)
+ -- TODO: location a bit awkward, but the mbinds have been
+ -- dependency analysed and may no longer be adjacent
+
+------------------
+tcPolyNoGen
+ :: TcSigFun -> PragFun
+ -> RecFlag -- Whether it's recursive after breaking
+ -- dependencies based on type signatures
+ -> [LHsBind Name]
+ -> TcM (LHsBinds TcId, [TcId])
+-- No generalisation whatsoever
+
+tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
+ = do { (binds', mono_infos) <- tcMonoBinds tc_sig_fn (LetGblBndr prag_fn)
+ rec_tc bind_list
+ ; mono_ids' <- mapM tc_mono_info mono_infos
+ ; return (binds', mono_ids') }
+ where
+ tc_mono_info (name, _, mono_id)
+ = do { mono_ty' <- zonkTcTypeCarefully (idType mono_id)
+ -- Zonk, mainly to expose unboxed types to checkStrictBinds
+ ; let mono_id' = setIdType mono_id mono_ty'
+ ; _specs <- tcSpecPrags mono_id' (prag_fn name)
+ ; return mono_id' }
+ -- NB: tcPrags generates error messages for
+ -- specialisation pragmas for non-overloaded sigs
+ -- Indeed that is why we call it here!
+ -- So we can safely ignore _specs
+
+------------------
+tcPolyCheck :: TcSigInfo -> PragFun
+ -> RecFlag -- Whether it's recursive after breaking
+ -- dependencies based on type signatures
+ -> [LHsBind Name]
+ -> TcM (LHsBinds TcId, [TcId])
+-- There is just one binding,
+-- it binds a single variable,
+-- it has a signature,
+tcPolyCheck sig@(TcSigInfo { sig_id = id, sig_tvs = tvs, sig_scoped = scoped
+ , sig_theta = theta, sig_loc = loc })
+ prag_fn rec_tc bind_list
+ = do { ev_vars <- newEvVars theta
+
+ ; let skol_info = SigSkol (FunSigCtxt (idName id))
+ ; (ev_binds, (binds', [mono_info]))
+ <- checkConstraints skol_info tvs ev_vars $
+ tcExtendTyVarEnv2 (scoped `zip` mkTyVarTys tvs) $
+ tcMonoBinds (\_ -> Just sig) LetLclBndr rec_tc bind_list
+
+ ; export <- mkExport prag_fn tvs theta mono_info
+
+ ; let (_, poly_id, _, _) = export
+ abs_bind = L loc $ AbsBinds
+ { abs_tvs = tvs
+ , abs_ev_vars = ev_vars, abs_ev_binds = ev_binds
+ , abs_exports = [export], abs_binds = binds' }
+ ; return (unitBag abs_bind, [poly_id]) }
+
+------------------
+tcPolyInfer
+ :: TopLevelFlag
+ -> Bool -- True <=> apply the monomorphism restriction
+ -> TcSigFun -> PragFun
+ -> RecFlag -- Whether it's recursive after breaking
+ -- dependencies based on type signatures
+ -> [LHsBind Name]
+ -> TcM (LHsBinds TcId, [TcId])
+tcPolyInfer top_lvl mono sig_fn prag_fn rec_tc bind_list
+ = do { ((binds', mono_infos), wanted)
+ <- captureConstraints $
+ tcMonoBinds sig_fn LetLclBndr rec_tc bind_list
+
+ ; unifyCtxts [sig | (_, Just sig, _) <- mono_infos]
+
+ ; let get_tvs | isTopLevel top_lvl = tyVarsOfType
+ | otherwise = exactTyVarsOfType
+ -- See Note [Silly type synonym] in TcType
+ tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
+
+ ; (qtvs, givens, ev_binds) <- simplifyInfer mono tau_tvs wanted
+
+ ; exports <- mapM (mkExport prag_fn qtvs (map evVarPred givens))
+ mono_infos
+
+ ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
+ ; traceTc "Binding:" (ppr (poly_ids `zip` map idType poly_ids))
+
+ ; loc <- getSrcSpanM
+ ; let abs_bind = L loc $ AbsBinds { abs_tvs = qtvs
+ , abs_ev_vars = givens, abs_ev_binds = ev_binds
+ , abs_exports = exports, abs_binds = binds' }
+
+ ; return (unitBag abs_bind, poly_ids) -- poly_ids are guaranteed zonked by mkExport
+ }
--------------
-mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType]
- -> MonoBindInfo
- -> TcM ([TyVar], Id, Id, [LPrag])
+mkExport :: PragFun -> [TyVar] -> TcThetaType
+ -> MonoBindInfo
+ -> TcM ([TyVar], Id, Id, TcSpecPrags)
-- mkExport generates exports with
--- zonked type variables,
--- zonked poly_ids
+-- zonked type variables,
+-- zonked poly_ids
-- The former is just because no further unifications will change
-- the quantified type variables, so we can fix their final form
-- right now.
-- Pre-condition: the inferred_tvs are already zonked
-mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
- = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs
- ; let warn = isTopLevel top_lvl && warn_missing_sigs
- ; (tvs, poly_id) <- mk_poly_id warn mb_sig
+mkExport prag_fn inferred_tvs theta
+ (poly_name, mb_sig, mono_id)
+ = do { (tvs, poly_id) <- mk_poly_id mb_sig
+ -- poly_id has a zonked type
- ; poly_id' <- zonkId poly_id
- ; prags <- tcPrags poly_id' (prag_fn poly_name)
- -- tcPrags requires a zonked poly_id
+ ; poly_id' <- addInlinePrags poly_id prag_sigs
- ; return (tvs, poly_id', mono_id, prags) }
+ ; spec_prags <- tcSpecPrags poly_id prag_sigs
+ -- tcPrags requires a zonked poly_id
+
+ ; return (tvs, poly_id', mono_id, SpecPrags spec_prags) }
where
- poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
+ prag_sigs = prag_fn poly_name
+ poly_ty = mkSigmaTy inferred_tvs theta (idType mono_id)
- mk_poly_id warn Nothing = do { missingSigWarn warn poly_name poly_ty
- ; return (inferred_tvs, mkLocalId poly_name poly_ty) }
- mk_poly_id warn (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
- ; return (tvs, sig_id sig) }
+ mk_poly_id Nothing = do { poly_ty' <- zonkTcTypeCarefully poly_ty
+ ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
+ mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
+ ; return (tvs, sig_id sig) }
zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
------------------------
-type TcPragFun = Name -> [LSig Name]
-
-mkPragFun :: [LSig Name] -> TcPragFun
-mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
- where
- prs = [(expectJust "mkPragFun" (sigName sig), sig)
- | sig <- sigs, isPragLSig sig]
- env = foldl add emptyNameEnv prs
- add env (n,p) = extendNameEnv_Acc (:) singleton env n p
-
-tcPrags :: Id -> [LSig Name] -> TcM [LPrag]
-tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags
- where
- tc_prag prag = addErrCtxt (pragSigCtxt prag) $
- tcPrag poly_id prag
+type PragFun = Name -> [LSig Name]
-pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
-
-tcPrag :: TcId -> Sig Name -> TcM Prag
+mkPragFun :: [LSig Name] -> LHsBinds Name -> PragFun
+mkPragFun sigs binds = \n -> lookupNameEnv prag_env n `orElse` []
+ where
+ prs = mapCatMaybes get_sig sigs
+
+ get_sig :: LSig Name -> Maybe (Located Name, LSig Name)
+ get_sig (L l (SpecSig nm ty inl)) = Just (nm, L l $ SpecSig nm ty (add_arity nm inl))
+ get_sig (L l (InlineSig nm inl)) = Just (nm, L l $ InlineSig nm (add_arity nm inl))
+ get_sig _ = Nothing
+
+ add_arity (L _ n) inl_prag -- Adjust inl_sat field to match visible arity of function
+ | Just ar <- lookupNameEnv ar_env n,
+ Inline <- inl_inline inl_prag = inl_prag { inl_sat = Just ar }
+ -- add arity only for real INLINE pragmas, not INLINABLE
+ | otherwise = inl_prag
+
+ prag_env :: NameEnv [LSig Name]
+ prag_env = foldl add emptyNameEnv prs
+ add env (L _ n,p) = extendNameEnv_Acc (:) singleton env n p
+
+ -- ar_env maps a local to the arity of its definition
+ ar_env :: NameEnv Arity
+ ar_env = foldrBag lhsBindArity emptyNameEnv binds
+
+lhsBindArity :: LHsBind Name -> NameEnv Arity -> NameEnv Arity
+lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env
+ = extendNameEnv env (unLoc id) (matchGroupArity ms)
+lhsBindArity _ env = env -- PatBind/VarBind
+
+------------------
+tcSpecPrags :: Id -> [LSig Name]
+ -> TcM [LTcSpecPrag]
+-- Add INLINE and SPECIALSE pragmas
+-- INLINE prags are added to the (polymorphic) Id directly
+-- SPECIALISE prags are passed to the desugarer via TcSpecPrags
-- Pre-condition: the poly_id is zonked
-- Reason: required by tcSubExp
-tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl
-tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
-tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl)
-
-
-tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
-tcSpecPrag poly_id hs_ty inl
- = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
- ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
- ; extendLIEs lie
- ; let const_dicts = map instToId lie
- ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
- -- Most of the work of specialisation is done by
- -- the desugarer, guided by the SpecPrag
-
+tcSpecPrags poly_id prag_sigs
+ = do { unless (null bad_sigs) warn_discarded_sigs
+ ; mapAndRecoverM (wrapLocM (tcSpec poly_id)) spec_sigs }
+ where
+ spec_sigs = filter isSpecLSig prag_sigs
+ bad_sigs = filter is_bad_sig prag_sigs
+ is_bad_sig s = not (isSpecLSig s || isInlineLSig s)
+
+ warn_discarded_sigs = warnPrags poly_id bad_sigs $
+ ptext (sLit "Discarding unexpected pragmas for")
+
+
+--------------
+tcSpec :: TcId -> Sig Name -> TcM TcSpecPrag
+tcSpec poly_id prag@(SpecSig _ hs_ty inl)
+ -- The Name in the SpecSig may not be the same as that of the poly_id
+ -- Example: SPECIALISE for a class method: the Name in the SpecSig is
+ -- for the selector Id, but the poly_id is something like $cop
+ = addErrCtxt (spec_ctxt prag) $
+ do { spec_ty <- tcHsSigType sig_ctxt hs_ty
+ ; checkTc (isOverloadedTy poly_ty)
+ (ptext (sLit "Discarding pragma for non-overloaded function") <+> quotes (ppr poly_id))
+ ; wrap <- tcSubType origin skol_info (idType poly_id) spec_ty
+ ; return (SpecPrag poly_id wrap inl) }
+ where
+ name = idName poly_id
+ poly_ty = idType poly_id
+ origin = SpecPragOrigin name
+ sig_ctxt = FunSigCtxt name
+ skol_info = SigSkol sig_ctxt
+ spec_ctxt prag = hang (ptext (sLit "In the SPECIALISE pragma")) 2 (ppr prag)
+
+tcSpec _ prag = pprPanic "tcSpec" (ppr prag)
+
+--------------
+tcImpPrags :: [LSig Name] -> TcM [LTcSpecPrag]
+tcImpPrags prags
+ = do { this_mod <- getModule
+ ; let is_imp prag
+ = case sigName prag of
+ Nothing -> False
+ Just name -> not (nameIsLocalOrFrom this_mod name)
+ (spec_prags, others) = partition isSpecLSig $
+ filter is_imp prags
+ ; mapM_ misplacedSigErr others
+ -- Messy that this misplaced-sig error comes here
+ -- but the others come from the renamer
+ ; mapAndRecoverM (wrapLocM tcImpSpec) spec_prags }
+
+tcImpSpec :: Sig Name -> TcM TcSpecPrag
+tcImpSpec prag@(SpecSig (L _ name) _ _)
+ = do { id <- tcLookupId name
+ ; checkTc (isInlinePragma (idInlinePragma id))
+ (impSpecErr name)
+ ; tcSpec id prag }
+tcImpSpec p = pprPanic "tcImpSpec" (ppr p)
+
+impSpecErr :: Name -> SDoc
+impSpecErr name
+ = hang (ptext (sLit "You cannot SPECIALISE") <+> quotes (ppr name))
+ 2 (ptext (sLit "because its definition has no INLINE/INLINABLE pragma"))
+
--------------
-- If typechecking the binds fails, then return with each
-- signature-less binder given type (forall a.a), to minimise
-- subsequent error messages
+recoveryCode :: [Name] -> SigFun -> TcM (LHsBinds TcId, [Id])
recoveryCode binder_names sig_fn
- = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
- ; poly_ids <- mapM mk_dummy binder_names
- ; return ([], poly_ids) }
+ = do { traceTc "tcBindsWithSigs: error recovery" (ppr binder_names)
+ ; poly_ids <- mapM mk_dummy binder_names
+ ; return (emptyBag, poly_ids) }
where
mk_dummy name
- | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
- | otherwise = return (mkLocalId name forall_a_a) -- No signature
+ | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
+ | otherwise = return (mkLocalId name forall_a_a) -- No signature
forall_a_a :: TcType
-forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
-
-
--- Check that non-overloaded unlifted bindings are
--- a) non-recursive,
--- b) not top level,
--- c) not a multiple-binding group (more or less implied by (a))
-
-checkStrictBinds :: TopLevelFlag -> RecFlag
- -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
- -> TcM Bool
-checkStrictBinds top_lvl rec_group mbind mono_tys infos
- | unlifted || bang_pat
- = do { checkTc (isNotTopLevel top_lvl)
- (strictBindErr "Top-level" unlifted mbind)
- ; checkTc (isNonRec rec_group)
- (strictBindErr "Recursive" unlifted mbind)
- ; checkTc (isSingletonBag mbind)
- (strictBindErr "Multiple" unlifted mbind)
- ; mapM_ check_sig infos
- ; return True }
- | otherwise
- = return False
- where
- unlifted = any isUnLiftedType mono_tys
- bang_pat = anyBag (isBangHsBind . unLoc) mbind
- check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
- (badStrictSig unlifted sig)
- check_sig other = return ()
-
-strictBindErr flavour unlifted mbind
- = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:"))
- 4 (pprLHsBinds mbind)
- where
- msg | unlifted = ptext SLIT("bindings for unlifted types")
- | otherwise = ptext SLIT("bang-pattern bindings")
-
-badStrictSig unlifted sig
- = hang (ptext SLIT("Illegal polymorphic signature in") <+> msg)
- 4 (ppr sig)
- where
- msg | unlifted = ptext SLIT("an unlifted binding")
- | otherwise = ptext SLIT("a bang-pattern binding")
+forall_a_a = mkForAllTy openAlphaTyVar (mkTyVarTy openAlphaTyVar)
\end{code}
%************************************************************************
-%* *
+%* *
\subsection{tcMonoBind}
-%* *
+%* *
%************************************************************************
@tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
The signatures have been dealt with already.
\begin{code}
-tcMonoBinds :: [LHsBind Name]
- -> TcSigFun
- -> RecFlag -- Whether the binding is recursive for typechecking purposes
- -- i.e. the binders are mentioned in their RHSs, and
- -- we are not resuced by a type signature
- -> TcM (LHsBinds TcId, [MonoBindInfo])
-
-tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
- fun_matches = matches, bind_fvs = fvs })]
- sig_fn -- Single function binding,
- NonRecursive -- binder isn't mentioned in RHS,
- | Nothing <- sig_fn name -- ...with no type signature
- = -- In this very special case we infer the type of the
- -- right hand side first (it may have a higher-rank type)
- -- and *then* make the monomorphic Id for the LHS
- -- e.g. f = \(x::forall a. a->a) -> <body>
- -- We want to infer a higher-rank type for f
- setSrcSpan b_loc $
- do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
-
- -- Check for an unboxed tuple type
- -- f = (# True, False #)
- -- Zonk first just in case it's hidden inside a meta type variable
- -- (This shows up as a (more obscure) kind error
- -- in the 'otherwise' case of tcMonoBinds.)
- ; zonked_rhs_ty <- zonkTcType rhs_ty
- ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
- (unboxedTupleErr name zonked_rhs_ty)
-
- ; mono_name <- newLocalName name
- ; let mono_id = mkLocalId mono_name zonked_rhs_ty
- ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
- fun_matches = matches', bind_fvs = fvs,
- fun_co_fn = co_fn, fun_tick = Nothing })),
- [(name, Nothing, mono_id)]) }
-
-tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
- fun_matches = matches, bind_fvs = fvs })]
- sig_fn -- Single function binding
- non_rec
- | Just scoped_tvs <- sig_fn name -- ...with a type signature
- = -- When we have a single function binding, with a type signature
- -- we can (a) use genuine, rigid skolem constants for the type variables
- -- (b) bring (rigid) scoped type variables into scope
- setSrcSpan b_loc $
- do { tc_sig <- tcInstSig True name scoped_tvs
- ; mono_name <- newLocalName name
- ; let mono_ty = sig_tau tc_sig
- mono_id = mkLocalId mono_name mono_ty
- rhs_tvs = [ (name, mkTyVarTy tv)
- | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
-
- ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
- tcMatchesFun mono_name inf matches mono_ty
-
- ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
- fun_infix = inf, fun_matches = matches',
- bind_fvs = placeHolderNames, fun_co_fn = co_fn,
- fun_tick = Nothing }
- ; return (unitBag (L b_loc fun_bind'),
- [(name, Just tc_sig, mono_id)]) }
-
-tcMonoBinds binds sig_fn non_rec
- = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
-
- -- Bring the monomorphic Ids, into scope for the RHSs
- ; let mono_info = getMonoBindInfo tc_binds
- rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
- -- A monomorphic binding for each term variable that lacks
- -- a type sig. (Ones with a sig are already in scope.)
-
- ; binds' <- tcExtendIdEnv2 rhs_id_env $
- traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
- | (n,id) <- rhs_id_env]) `thenM_`
- mapM (wrapLocM tcRhs) tc_binds
- ; return (listToBag binds', mono_info) }
+tcMonoBinds :: TcSigFun -> LetBndrSpec
+ -> RecFlag -- Whether the binding is recursive for typechecking purposes
+ -- i.e. the binders are mentioned in their RHSs, and
+ -- we are not resuced by a type signature
+ -> [LHsBind Name]
+ -> TcM (LHsBinds TcId, [MonoBindInfo])
+
+tcMonoBinds sig_fn no_gen is_rec
+ [ L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
+ fun_matches = matches, bind_fvs = fvs })]
+ -- Single function binding,
+ | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS
+ , Nothing <- sig_fn name -- ...with no type signature
+ = -- In this very special case we infer the type of the
+ -- right hand side first (it may have a higher-rank type)
+ -- and *then* make the monomorphic Id for the LHS
+ -- e.g. f = \(x::forall a. a->a) -> <body>
+ -- We want to infer a higher-rank type for f
+ setSrcSpan b_loc $
+ do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
+
+ ; mono_id <- newNoSigLetBndr no_gen name rhs_ty
+ ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
+ fun_matches = matches', bind_fvs = fvs,
+ fun_co_fn = co_fn, fun_tick = Nothing })),
+ [(name, Nothing, mono_id)]) }
+
+tcMonoBinds sig_fn no_gen _ binds
+ = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn no_gen)) binds
+
+ -- Bring the monomorphic Ids, into scope for the RHSs
+ ; let mono_info = getMonoBindInfo tc_binds
+ rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
+ -- A monomorphic binding for each term variable that lacks
+ -- a type sig. (Ones with a sig are already in scope.)
+
+ ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
+ traceTc "tcMonoBinds" $ vcat [ ppr n <+> ppr id <+> ppr (idType id)
+ | (n,id) <- rhs_id_env]
+ mapM (wrapLocM tcRhs) tc_binds
+ ; return (listToBag binds', mono_info) }
------------------------
-- tcLhs typechecks the LHS of the bindings, to construct the environment in which
-- we typecheck the RHSs. Basically what we are doing is this: for each binder:
--- if there's a signature for it, use the instantiated signature type
--- otherwise invent a type variable
+-- if there's a signature for it, use the instantiated signature type
+-- otherwise invent a type variable
-- You see that quite directly in the FunBind case.
--
-- But there's a complication for pattern bindings:
--- data T = MkT (forall a. a->a)
--- MkT f = e
+-- data T = MkT (forall a. a->a)
+-- MkT f = e
-- Here we can guess a type variable for the entire LHS (which will be refined to T)
-- but we want to get (f::forall a. a->a) as the RHS environment.
-- The simplest way to do this is to typecheck the pattern, and then look up the
-- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
-- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
-data TcMonoBind -- Half completed; LHS done, RHS not done
- = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
+data TcMonoBind -- Half completed; LHS done, RHS not done
+ = TcFunBind MonoBindInfo SrcSpan Bool (MatchGroup Name)
| TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
- -- Type signature (if any), and
- -- the monomorphic bound things
-
-bndrNames :: [MonoBindInfo] -> [Name]
-bndrNames mbi = [n | (n,_,_) <- mbi]
+ -- Type signature (if any), and
+ -- the monomorphic bound things
getMonoType :: MonoBindInfo -> TcTauType
getMonoType (_,_,mono_id) = idType mono_id
-tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
-tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
- = do { mb_sig <- tcInstSig_maybe sig_fn name
- ; mono_name <- newLocalName name
- ; mono_ty <- mk_mono_ty mb_sig
- ; let mono_id = mkLocalId mono_name mono_ty
- ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
- where
- mk_mono_ty (Just sig) = return (sig_tau sig)
- mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
-
-tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
- = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
- ; mono_pat_binds <- doptM Opt_MonoPatBinds
- -- With -fmono-pat-binds, we do no generalisation of pattern bindings
- -- But the signature can still be polymoprhic!
- -- data T = MkT (forall a. a->a)
- -- x :: forall a. a->a
- -- MkT x = <rhs>
- -- The function get_sig_ty decides whether the pattern-bound variables
- -- should have exactly the type in the type signature (-fmono-pat-binds),
- -- or the instantiated version (-fmono-pat-binds)
-
- ; let nm_sig_prs = names `zip` mb_sigs
- get_sig_ty | mono_pat_binds = idType . sig_id
- | otherwise = sig_tau
- tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
- | (name, Just sig) <- nm_sig_prs]
- sig_tau_fn = lookupNameEnv tau_sig_env
-
- tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
- mapM lookup_info nm_sig_prs
-
- -- After typechecking the pattern, look up the binder
- -- names, which the pattern has brought into scope.
- lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
- lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
- ; return (name, mb_sig, mono_id) }
-
- ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
- tcInfer tc_pat
-
- ; return (TcPatBind infos pat' grhss pat_ty) }
- where
- names = collectPatBinders pat
+tcLhs :: TcSigFun -> LetBndrSpec -> HsBind Name -> TcM TcMonoBind
+tcLhs sig_fn no_gen (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
+ | Just sig <- sig_fn name
+ = do { mono_id <- newSigLetBndr no_gen name sig
+ ; return (TcFunBind (name, Just sig, mono_id) nm_loc inf matches) }
+ | otherwise
+ = do { mono_ty <- newFlexiTyVarTy argTypeKind
+ ; mono_id <- newNoSigLetBndr no_gen name mono_ty
+ ; return (TcFunBind (name, Nothing, mono_id) nm_loc inf matches) }
+
+tcLhs sig_fn no_gen (PatBind { pat_lhs = pat, pat_rhs = grhss })
+ = do { let tc_pat exp_ty = tcLetPat sig_fn no_gen pat exp_ty $
+ mapM lookup_info (collectPatBinders pat)
+ -- After typechecking the pattern, look up the binder
+ -- names, which the pattern has brought into scope.
+ lookup_info :: Name -> TcM MonoBindInfo
+ lookup_info name = do { mono_id <- tcLookupId name
+ ; return (name, sig_fn name, mono_id) }
-tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
- -- AbsBind, VarBind impossible
+ ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
+ tcInfer tc_pat
+
+ ; return (TcPatBind infos pat' grhss pat_ty) }
+
+tcLhs _ _ other_bind = pprPanic "tcLhs" (ppr other_bind)
+ -- AbsBind, VarBind impossible
-------------------
tcRhs :: TcMonoBind -> TcM (HsBind TcId)
-tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
- = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
- matches (idType mono_id)
- ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
- bind_fvs = placeHolderNames, fun_co_fn = co_fn,
- fun_tick = Nothing }) }
-
-tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
- = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
- tcGRHSsPat grhss pat_ty
- ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
- bind_fvs = placeHolderNames }) }
+-- When we are doing pattern bindings, or multiple function bindings at a time
+-- we *don't* bring any scoped type variables into scope
+-- Wny not? They are not completely rigid.
+-- That's why we have the special case for a single FunBind in tcMonoBinds
+tcRhs (TcFunBind (_,_,mono_id) loc inf matches)
+ = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
+ matches (idType mono_id)
+ ; return (FunBind { fun_id = L loc mono_id, fun_infix = inf
+ , fun_matches = matches'
+ , fun_co_fn = co_fn
+ , bind_fvs = placeHolderNames, fun_tick = Nothing }) }
+
+tcRhs (TcPatBind _ pat' grhss pat_ty)
+ = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
+ tcGRHSsPat grhss pat_ty
+ ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty
+ , bind_fvs = placeHolderNames }) }
---------------------
%************************************************************************
-%* *
- Generalisation
-%* *
+%* *
+ Generalisation
+%* *
%************************************************************************
-\begin{code}
-generalise :: DynFlags -> TopLevelFlag
- -> [LHsBind Name] -> TcSigFun
- -> [MonoBindInfo] -> [Inst]
- -> TcM ([TyVar], [Inst], TcDictBinds)
--- The returned [TyVar] are all ready to quantify
-
-generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
- | isMonoGroup dflags bind_list
- = do { extendLIEs lie_req
- ; return ([], [], emptyBag) }
-
- | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
- = -- Check signature contexts are empty
- do { checkTc (all is_mono_sig sigs)
- (restrictedBindCtxtErr bndrs)
-
- -- Now simplify with exactly that set of tyvars
- -- We have to squash those Methods
- ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
- tau_tvs lie_req
-
- -- Check that signature type variables are OK
- ; final_qtvs <- checkSigsTyVars qtvs sigs
-
- ; return (final_qtvs, [], binds) }
-
- | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
- = tcSimplifyInfer doc tau_tvs lie_req
-
- | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
- = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked
- ; let -- The "sig_avails" is the stuff available. We get that from
- -- the context of the type signature, BUT ALSO the lie_avail
- -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
- local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
- sig_avails = sig_lie ++ local_meths
- loc = sig_loc (head sigs)
-
- -- Check that the needed dicts can be
- -- expressed in terms of the signature ones
- ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req
-
- -- Check that signature type variables are OK
- ; final_qtvs <- checkSigsTyVars qtvs sigs
-
- ; returnM (final_qtvs, sig_lie, binds) }
- where
- bndrs = bndrNames mono_infos
- sigs = [sig | (_, Just sig, _) <- mono_infos]
- tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos
- -- NB: exactTyVarsOfType; see Note [Silly type synonym]
- -- near defn of TcType.exactTyVarsOfType
- is_mono_sig sig = null (sig_theta sig)
- doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs
-
- mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
- sig_theta = theta, sig_loc = loc }) mono_id
- = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs,
- tci_theta = theta, tci_loc = loc}
-\end{code}
-
unifyCtxts checks that all the signature contexts are the same
The type signatures on a mutually-recursive group of definitions
must all have the same context (or none).
might not otherwise be related. This is a rather subtle issue.
\begin{code}
-unifyCtxts :: [TcSigInfo] -> TcM [Inst]
+unifyCtxts :: [TcSigInfo] -> TcM ()
-- Post-condition: the returned Insts are full zonked
-unifyCtxts (sig1 : sigs) -- Argument is always non-empty
- = do { mapM unify_ctxt sigs
- ; theta <- zonkTcThetaType (sig_theta sig1)
- ; newDictBndrs (sig_loc sig1) theta }
+unifyCtxts [] = return ()
+unifyCtxts (sig1 : sigs)
+ = do { traceTc "unifyCtxts" (ppr (sig1 : sigs))
+ ; mapM_ unify_ctxt sigs }
where
theta1 = sig_theta sig1
unify_ctxt :: TcSigInfo -> TcM ()
unify_ctxt sig@(TcSigInfo { sig_theta = theta })
- = setSrcSpan (instLocSpan (sig_loc sig)) $
- addErrCtxt (sigContextsCtxt sig1 sig) $
- do { cois <- unifyTheta theta1 theta
- ; -- Check whether all coercions are identity coercions
- -- That can happen if we have, say
- -- f :: C [a] => ...
- -- g :: C (F a) => ...
- -- where F is a type function and (F a ~ [a])
- -- Then unification might succeed with a coercion. But it's much
- -- much simpler to require that such signatures have identical contexts
- checkTc (all isIdentityCoercion cois)
- (ptext SLIT("Mutually dependent functions have syntactically distinct contexts"))
- }
-
-checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
-checkSigsTyVars qtvs sigs
- = do { gbl_tvs <- tcGetGlobalTyVars
- ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
-
- ; let -- Sigh. Make sure that all the tyvars in the type sigs
- -- appear in the returned ty var list, which is what we are
- -- going to generalise over. Reason: we occasionally get
- -- silly types like
- -- type T a = () -> ()
- -- f :: T a
- -- f () = ()
- -- Here, 'a' won't appear in qtvs, so we have to add it
- sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
- all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
- ; returnM all_tvs }
- where
- check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
- sig_theta = theta, sig_tau = tau})
- = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
- addErrCtxtM (sigCtxt id tvs theta tau) $
- do { tvs' <- checkDistinctTyVars tvs
- ; ifM (any (`elemVarSet` gbl_tvs) tvs')
- (bleatEscapedTvs gbl_tvs tvs tvs')
- ; return tvs' }
-
-checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
--- (checkDistinctTyVars tvs) checks that the tvs from one type signature
--- are still all type variables, and all distinct from each other.
--- It returns a zonked set of type variables.
--- For example, if the type sig is
--- f :: forall a b. a -> b -> b
--- we want to check that 'a' and 'b' haven't
--- (a) been unified with a non-tyvar type
--- (b) been unified with each other (all distinct)
-
-checkDistinctTyVars sig_tvs
- = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
- ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
- ; return zonked_tvs }
- where
- check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
- -- The TyVarEnv maps each zonked type variable back to its
- -- corresponding user-written signature type variable
- check_dup acc (sig_tv, zonked_tv)
- = case lookupVarEnv acc zonked_tv of
- Just sig_tv' -> bomb_out sig_tv sig_tv'
-
- Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
-
- bomb_out sig_tv1 sig_tv2
- = do { env0 <- tcInitTidyEnv
- ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
- (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
- msg = ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
- <+> ptext SLIT("is unified with another quantified type variable")
- <+> quotes (ppr tidy_tv2)
- ; failWithTcM (env2, msg) }
- where
+ = setSrcSpan (sig_loc sig) $
+ addErrCtxt (sigContextsCtxt sig1 sig) $
+ do { cois <- unifyTheta theta1 theta
+ ; -- Check whether all coercions are identity coercions
+ -- That can happen if we have, say
+ -- f :: C [a] => ...
+ -- g :: C (F a) => ...
+ -- where F is a type function and (F a ~ [a])
+ -- Then unification might succeed with a coercion. But it's much
+ -- much simpler to require that such signatures have identical contexts
+ checkTc (all isIdentityCoI cois)
+ (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
+ }
\end{code}
*Don't* simplify dicts at this point, because we aren't going
to generalise over these dicts. By the time we do simplify them
we may well know more. For example (this actually came up)
- f :: Array Int Int
- f x = array ... xs where xs = [1,2,3,4,5]
+ f :: Array Int Int
+ f x = array ... xs where xs = [1,2,3,4,5]
We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
stuff. If we simplify only at the f-binding (not the xs-binding)
we'll know that the literals are all Ints, and we can just produce
generalise. We must be careful about doing this:
(a) If we fail to generalise a tyvar which is not actually
- constrained, then it will never, ever get bound, and lands
- up printed out in interface files! Notorious example:
- instance Eq a => Eq (Foo a b) where ..
- Here, b is not constrained, even though it looks as if it is.
- Another, more common, example is when there's a Method inst in
- the LIE, whose type might very well involve non-overloaded
- type variables.
+ constrained, then it will never, ever get bound, and lands
+ up printed out in interface files! Notorious example:
+ instance Eq a => Eq (Foo a b) where ..
+ Here, b is not constrained, even though it looks as if it is.
+ Another, more common, example is when there's a Method inst in
+ the LIE, whose type might very well involve non-overloaded
+ type variables.
[NOTE: Jan 2001: I don't understand the problem here so I'm doing
- the simple thing instead]
+ the simple thing instead]
(b) On the other hand, we mustn't generalise tyvars which are constrained,
- because we are going to pass on out the unmodified LIE, with those
- tyvars in it. They won't be in scope if we've generalised them.
+ because we are going to pass on out the unmodified LIE, with those
+ tyvars in it. They won't be in scope if we've generalised them.
So we are careful, and do a complete simplification just to find the
constrained tyvars. We don't use any of the results, except to
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The game plan for polymorphic recursion in the code above is
- * Bind any variable for which we have a type signature
- to an Id with a polymorphic type. Then when type-checking
- the RHSs we'll make a full polymorphic call.
+ * Bind any variable for which we have a type signature
+ to an Id with a polymorphic type. Then when type-checking
+ the RHSs we'll make a full polymorphic call.
This fine, but if you aren't a bit careful you end up with a horrendous
amount of partial application and (worse) a huge space leak. For example:
- f :: Eq a => [a] -> [a]
- f xs = ...f...
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
If we don't take care, after typechecking we get
- f = /\a -> \d::Eq a -> let f' = f a d
- in
- \ys:[a] -> ...f'...
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
Notice the the stupid construction of (f a d), which is of course
identical to the function we're executing. In this case, the
This can lead to a massive space leak, from the following top-level defn
(post-typechecking)
- ff :: [Int] -> [Int]
- ff = f Int dEqInt
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
f' is another thunk which evaluates to the same thing... and you end
up with a chain of identical values all hung onto by the CAF ff.
- ff = f Int dEqInt
+ ff = f Int dEqInt
- = let f' = f Int dEqInt in \ys. ...f'...
+ = let f' = f Int dEqInt in \ys. ...f'...
- = let f' = let f' = f Int dEqInt in \ys. ...f'...
- in \ys. ...f'...
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
Etc.
Then we get
- f = /\a -> \d::Eq a -> letrec
- fm = \ys:[a] -> ...fm...
- in
- fm
-
-
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
%************************************************************************
-%* *
- Signatures
-%* *
+%* *
+ Signatures
+%* *
%************************************************************************
Type signatures are tricky. See Note [Signature skolems] in TcType
the variable's type, and after that checked to see whether they've
been instantiated.
+Note [Scoped tyvars]
+~~~~~~~~~~~~~~~~~~~~
+The -XScopedTypeVariables flag brings lexically-scoped type variables
+into scope for any explicitly forall-quantified type variables:
+ f :: forall a. a -> a
+ f x = e
+Then 'a' is in scope inside 'e'.
+
+However, we do *not* support this
+ - For pattern bindings e.g
+ f :: forall a. a->a
+ (f,g) = e
+
+ - For multiple function bindings, unless Opt_RelaxedPolyRec is on
+ f :: forall a. a -> a
+ f = g
+ g :: forall b. b -> b
+ g = ...f...
+ Reason: we use mutable variables for 'a' and 'b', since they may
+ unify to each other, and that means the scoped type variable would
+ not stand for a completely rigid variable.
+
+ Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
+
+
+Note [More instantiated than scoped]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+There may be more instantiated type variables than lexically-scoped
+ones. For example:
+ type T a = forall b. b -> (a,b)
+ f :: forall c. T c
+Here, the signature for f will have one scoped type variable, c,
+but two instantiated type variables, c' and b'.
+
+We assume that the scoped ones are at the *front* of sig_tvs,
+and remember the names from the original HsForAllTy in the TcSigFun.
+
+Note [Signature skolems]
+~~~~~~~~~~~~~~~~~~~~~~~~
+When instantiating a type signature, we do so with either skolems or
+SigTv meta-type variables depending on the use_skols boolean. This
+variable is set True when we are typechecking a single function
+binding; and False for pattern bindings and a group of several
+function bindings.
+
+Reason: in the latter cases, the "skolems" can be unified together,
+ so they aren't properly rigid in the type-refinement sense.
+NB: unless we are doing H98, each function with a sig will be done
+ separately, even if it's mutually recursive, so use_skols will be True
+
+
+Note [Only scoped tyvars are in the TyVarEnv]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We are careful to keep only the *lexically scoped* type variables in
+the type environment. Why? After all, the renamer has ensured
+that only legal occurrences occur, so we could put all type variables
+into the type env.
+
+But we want to check that two distinct lexically scoped type variables
+do not map to the same internal type variable. So we need to know which
+the lexically-scoped ones are... and at the moment we do that by putting
+only the lexically scoped ones into the environment.
+
+Note [Instantiate sig with fresh variables]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It's vital to instantiate a type signature with fresh variables.
+For example:
+ type T = forall a. [a] -> [a]
+ f :: T;
+ f = g where { g :: T; g = <rhs> }
+
+ We must not use the same 'a' from the defn of T at both places!!
+(Instantiation is only necessary because of type synonyms. Otherwise,
+it's all cool; each signature has distinct type variables from the renamer.)
+
\begin{code}
-type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
- -- type variables brought into scope
- -- by its type signature.
- -- Nothing => no type signature
+type SigFun = Name -> Maybe ([Name], SrcSpan)
+ -- Maps a let-binder to the list of
+ -- type variables brought into scope
+ -- by its type signature, plus location
+ -- Nothing => no type signature
-mkTcSigFun :: [LSig Name] -> TcSigFun
+mkSigFun :: [LSig Name] -> SigFun
-- Search for a particular type signature
-- Precondition: the sigs are all type sigs
-- Precondition: no duplicates
-mkTcSigFun sigs = lookupNameEnv env
+mkSigFun sigs = lookupNameEnv env
where
- env = mkNameEnv [(name, hsExplicitTvs lhs_ty)
- | L span (TypeSig (L _ name) lhs_ty) <- sigs]
- -- The scoped names are the ones explicitly mentioned
- -- in the HsForAll. (There may be more in sigma_ty, because
- -- of nested type synonyms. See Note [Scoped] with TcSigInfo.)
- -- See Note [Only scoped tyvars are in the TyVarEnv]
-
----------------
-data TcSigInfo
- = TcSigInfo {
- sig_id :: TcId, -- *Polymorphic* binder for this value...
-
- sig_scoped :: [Name], -- Names for any scoped type variables
- -- Invariant: correspond 1-1 with an initial
- -- segment of sig_tvs (see Note [Scoped])
-
- sig_tvs :: [TcTyVar], -- Instantiated type variables
- -- See Note [Instantiate sig]
-
- sig_theta :: TcThetaType, -- Instantiated theta
- sig_tau :: TcTauType, -- Instantiated tau
- sig_loc :: InstLoc -- The location of the signature
- }
-
-
--- Note [Only scoped tyvars are in the TyVarEnv]
--- We are careful to keep only the *lexically scoped* type variables in
--- the type environment. Why? After all, the renamer has ensured
--- that only legal occurrences occur, so we could put all type variables
--- into the type env.
---
--- But we want to check that two distinct lexically scoped type variables
--- do not map to the same internal type variable. So we need to know which
--- the lexically-scoped ones are... and at the moment we do that by putting
--- only the lexically scoped ones into the environment.
-
-
--- Note [Scoped]
--- There may be more instantiated type variables than scoped
--- ones. For example:
--- type T a = forall b. b -> (a,b)
--- f :: forall c. T c
--- Here, the signature for f will have one scoped type variable, c,
--- but two instantiated type variables, c' and b'.
---
--- We assume that the scoped ones are at the *front* of sig_tvs,
--- and remember the names from the original HsForAllTy in sig_scoped
-
--- Note [Instantiate sig]
--- It's vital to instantiate a type signature with fresh variables.
--- For example:
--- type S = forall a. a->a
--- f,g :: S
--- f = ...
--- g = ...
--- Here, we must use distinct type variables when checking f,g's right hand sides.
--- (Instantiation is only necessary because of type synonyms. Otherwise,
--- it's all cool; each signature has distinct type variables from the renamer.)
-
-instance Outputable TcSigInfo where
- ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
- = ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
+ env = mkNameEnv (mapCatMaybes mk_pair sigs)
+ mk_pair (L loc (TypeSig (L _ name) lhs_ty)) = Just (name, (hsExplicitTvs lhs_ty, loc))
+ mk_pair (L loc (IdSig id)) = Just (idName id, ([], loc))
+ mk_pair _ = Nothing
+ -- The scoped names are the ones explicitly mentioned
+ -- in the HsForAll. (There may be more in sigma_ty, because
+ -- of nested type synonyms. See Note [More instantiated than scoped].)
+ -- See Note [Only scoped tyvars are in the TyVarEnv]
\end{code}
\begin{code}
tcTySig :: LSig Name -> TcM TcId
tcTySig (L span (TypeSig (L _ name) ty))
- = setSrcSpan span $
- do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
- ; return (mkLocalId name sigma_ty) }
+ = setSrcSpan span $
+ do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkLocalId name sigma_ty) }
+tcTySig (L _ (IdSig id))
+ = return id
+tcTySig s = pprPanic "tcTySig" (ppr s)
-------------------
-tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
--- Instantiate with *meta* type variables;
--- this signature is part of a multi-signature group
-tcInstSig_maybe sig_fn name
- = case sig_fn name of
- Nothing -> return Nothing
- Just tvs -> do { tc_sig <- tcInstSig False name tvs
- ; return (Just tc_sig) }
-
-tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo
--- Instantiate the signature, with either skolems or meta-type variables
--- depending on the use_skols boolean. This variable is set True
--- when we are typechecking a single function binding; and False for
--- pattern bindings and a group of several function bindings.
--- Reason: in the latter cases, the "skolems" can be unified together,
--- so they aren't properly rigid in the type-refinement sense.
--- NB: unless we are doing H98, each function with a sig will be done
--- separately, even if it's mutually recursive, so use_skols will be True
---
--- We always instantiate with fresh uniques,
--- although we keep the same print-name
---
--- type T = forall a. [a] -> [a]
--- f :: T;
--- f = g where { g :: T; g = <rhs> }
+tcInstSigs :: SigFun -> [Name] -> TcM TcSigFun
+tcInstSigs sig_fn bndrs
+ = do { prs <- mapMaybeM (tcInstSig sig_fn use_skols) bndrs
+ ; return (lookupNameEnv (mkNameEnv prs)) }
+ where
+ use_skols = isSingleton bndrs -- See Note [Signature skolems]
+
+tcInstSig :: SigFun -> Bool -> Name -> TcM (Maybe (Name, TcSigInfo))
+-- For use_skols :: Bool see Note [Signature skolems]
--
--- We must not use the same 'a' from the defn of T at both places!!
-
-tcInstSig use_skols name scoped_names
- = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
- -- scope when starting the binding group
- ; let skol_info = SigSkol (FunSigCtxt name)
- inst_tyvars = tcInstSigTyVars use_skols skol_info
- ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
- ; loc <- getInstLoc (SigOrigin skol_info)
- ; return (TcSigInfo { sig_id = poly_id,
- sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
- sig_scoped = final_scoped_names, sig_loc = loc }) }
- -- Note that the scoped_names and the sig_tvs will have
- -- different Names. That's quite ok; when we bring the
- -- scoped_names into scope, we just bind them to the sig_tvs
+-- We must instantiate with fresh uniques,
+-- (see Note [Instantiate sig with fresh variables])
+-- although we keep the same print-name.
+
+tcInstSig sig_fn use_skols name
+ | Just (scoped_tvs, loc) <- sig_fn name
+ = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
+ -- scope when starting the binding group
+ ; (tvs, theta, tau) <- tcInstSigType use_skols name (idType poly_id)
+ ; let sig = TcSigInfo { sig_id = poly_id
+ , sig_scoped = scoped_tvs
+ , sig_tvs = tvs, sig_theta = theta, sig_tau = tau
+ , sig_loc = loc }
+ ; return (Just (name, sig)) }
+ | otherwise
+ = return Nothing
+
+-------------------------------
+data GeneralisationPlan
+ = NoGen -- No generalisation, no AbsBinds
+ | InferGen Bool -- Implicit generalisation; there is an AbsBinds
+ -- True <=> apply the MR; generalise only unconstrained type vars
+ | CheckGen TcSigInfo -- Explicit generalisation; there is an AbsBinds
+
+-- A consequence of the no-AbsBinds choice (NoGen) is that there is
+-- no "polymorphic Id" and "monmomorphic Id"; there is just the one
+
+instance Outputable GeneralisationPlan where
+ ppr NoGen = ptext (sLit "NoGen")
+ ppr (InferGen b) = ptext (sLit "InferGen") <+> ppr b
+ ppr (CheckGen s) = ptext (sLit "CheckGen") <+> ppr s
+
+decideGeneralisationPlan
+ :: DynFlags -> TopLevelFlag -> [Name] -> [LHsBind Name] -> TcSigFun -> GeneralisationPlan
+decideGeneralisationPlan dflags top_lvl _bndrs binds sig_fn
+ | mono_pat_binds = NoGen
+ | Just sig <- one_funbind_with_sig binds = if null (sig_tvs sig) && null (sig_theta sig)
+ then NoGen -- Optimise common case
+ else CheckGen sig
+ | (xopt Opt_MonoLocalBinds dflags
+ && isNotTopLevel top_lvl) = NoGen
+ | otherwise = InferGen mono_restriction
+
where
- -- We also only have scoped type variables when we are instantiating
- -- with true skolems
- final_scoped_names | use_skols = scoped_names
- | otherwise = []
+ mono_pat_binds = xopt Opt_MonoPatBinds dflags
+ && any (is_pat_bind . unLoc) binds
+
+ mono_restriction = xopt Opt_MonomorphismRestriction dflags
+ && any (restricted . unLoc) binds
+
+ no_sig n = isNothing (sig_fn n)
+
+ -- With OutsideIn, all nested bindings are monomorphic
+ -- except a single function binding with a signature
+ one_funbind_with_sig [L _ FunBind { fun_id = v }] = sig_fn (unLoc v)
+ one_funbind_with_sig _ = Nothing
+
+ -- The Haskell 98 monomorphism resetriction
+ restricted (PatBind {}) = True
+ restricted (VarBind { var_id = v }) = no_sig v
+ restricted (FunBind { fun_id = v, fun_matches = m }) = restricted_match m
+ && no_sig (unLoc v)
+ restricted (AbsBinds {}) = panic "isRestrictedGroup/unrestricted AbsBinds"
+
+ restricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = True
+ restricted_match _ = False
+ -- No args => like a pattern binding
+ -- Some args => a function binding
+
+ is_pat_bind (PatBind {}) = True
+ is_pat_bind _ = False
-------------------
-isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
--- No generalisation at all
-isMonoGroup dflags binds
- = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
+checkStrictBinds :: TopLevelFlag -> RecFlag
+ -> [LHsBind Name] -> [Id]
+ -> TcM ()
+-- Check that non-overloaded unlifted bindings are
+-- a) non-recursive,
+-- b) not top level,
+-- c) not a multiple-binding group (more or less implied by (a))
+
+checkStrictBinds top_lvl rec_group binds poly_ids
+ | unlifted || bang_pat
+ = do { checkTc (isNotTopLevel top_lvl)
+ (strictBindErr "Top-level" unlifted binds)
+ ; checkTc (isNonRec rec_group)
+ (strictBindErr "Recursive" unlifted binds)
+ ; checkTc (isSingleton binds)
+ (strictBindErr "Multiple" unlifted binds)
+ -- This should be a checkTc, not a warnTc, but as of GHC 6.11
+ -- the versions of alex and happy available have non-conforming
+ -- templates, so the GHC build fails if it's an error:
+ ; warnUnlifted <- doptM Opt_WarnLazyUnliftedBindings
+ ; warnTc (warnUnlifted && not bang_pat)
+ (unliftedMustBeBang binds) }
+ | otherwise
+ = return ()
where
- is_pat_bind (L _ (PatBind {})) = True
- is_pat_bind other = False
+ unlifted = any is_unlifted poly_ids
+ bang_pat = any (isBangHsBind . unLoc) binds
+ is_unlifted id = case tcSplitForAllTys (idType id) of
+ (_, rho) -> isUnLiftedType rho
+
+unliftedMustBeBang :: [LHsBind Name] -> SDoc
+unliftedMustBeBang binds
+ = hang (text "Bindings containing unlifted types should use an outermost bang pattern:")
+ 2 (pprBindList binds)
+
+strictBindErr :: String -> Bool -> [LHsBind Name] -> SDoc
+strictBindErr flavour unlifted binds
+ = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
+ 2 (pprBindList binds)
+ where
+ msg | unlifted = ptext (sLit "bindings for unlifted types")
+ | otherwise = ptext (sLit "bang-pattern bindings")
--------------------
-isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
-isRestrictedGroup dflags binds sig_fn
- = mono_restriction && not all_unrestricted
- where
- mono_restriction = dopt Opt_MonomorphismRestriction dflags
- all_unrestricted = all (unrestricted . unLoc) binds
- has_sig n = isJust (sig_fn n)
-
- unrestricted (PatBind {}) = False
- unrestricted (VarBind { var_id = v }) = has_sig v
- unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
- || has_sig (unLoc v)
-
- unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
- -- No args => like a pattern binding
- unrestricted_match other = True
- -- Some args => a function binding
+pprBindList :: [LHsBind Name] -> SDoc
+pprBindList binds = vcat (map ppr binds)
\end{code}
%************************************************************************
-%* *
+%* *
\subsection[TcBinds-errors]{Error contexts and messages}
-%* *
+%* *
%************************************************************************
\begin{code}
-- This one is called on LHS, when pat and grhss are both Name
-- and on RHS, when pat is TcId and grhss is still Name
+patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
patMonoBindsCtxt pat grhss
- = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
+ = hang (ptext (sLit "In a pattern binding:")) 2 (pprPatBind pat grhss)
-----------------------------------------------
+sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
sigContextsCtxt sig1 sig2
- = vcat [ptext SLIT("When matching the contexts of the signatures for"),
- nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
- ppr id2 <+> dcolon <+> ppr (idType id2)]),
- ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
+ = vcat [ptext (sLit "When matching the contexts of the signatures for"),
+ nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
+ ppr id2 <+> dcolon <+> ppr (idType id2)]),
+ ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]
where
id1 = sig_id sig1
id2 = sig_id sig2
-
-
------------------------------------------------
-unboxedTupleErr name ty
- = hang (ptext SLIT("Illegal binding of unboxed tuple"))
- 4 (ppr name <+> dcolon <+> ppr ty)
-
------------------------------------------------
-restrictedBindCtxtErr binder_names
- = hang (ptext SLIT("Illegal overloaded type signature(s)"))
- 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
- ptext SLIT("that falls under the monomorphism restriction")])
-
-genCtxt binder_names
- = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
-
-missingSigWarn False name ty = return ()
-missingSigWarn True name ty
- = do { env0 <- tcInitTidyEnv
- ; let (env1, tidy_ty) = tidyOpenType env0 ty
- ; addWarnTcM (env1, mk_msg tidy_ty) }
- where
- mk_msg ty = vcat [ptext SLIT("Definition but no type signature for") <+> quotes (ppr name),
- sep [ptext SLIT("Inferred type:") <+> ppr name <+> dcolon <+> ppr ty]]
\end{code}
projects / ghc-hetmet.git / blobdiff