%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-#include "HsVersions.h"
-
-module TcInstDcls (
- tcInstDecls1, tcInstDecls2,
- tcSpecInstSigs,
- buildInstanceEnvs, processInstBinds,
- mkInstanceRelatedIds,
- InstInfo(..)
- ) where
+module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
-IMPORT_Trace -- ToDo:rm debugging
-import Outputable
-import Pretty
+#include "HsVersions.h"
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( newDicts, newMethod, newLocalWithGivenTy,
- newClassOpLocals, copyTyVars,
- applyTcSubstAndCollectTyVars
- )
-import AbsSyn -- the stuff being typechecked
-import AbsPrel ( pAT_ERROR_ID )
-import AbsUniType
-import BackSubst ( applyTcSubstToBinds )
-import Bag ( emptyBag, unitBag, unionBags, bagToList )
-import CE ( lookupCE, CE(..) )
-import CmdLineOpts ( GlobalSwitch(..) )
-import GenSpecEtc ( checkSigTyVars, SignatureInfo )
-import E ( mkE, getE_CE, getE_TCE, growE_LVE, tvOfE, LVE(..), E )
-import Errors ( dupInstErr, derivingWhenInstanceExistsErr,
- preludeInstanceErr, nonBoxedPrimCCallErr,
- specInstUnspecInstNotFoundErr,
- Error(..), UnifyErrContext(..)
+import HsSyn
+import TcBinds ( mkPragFun, tcPrags, badBootDeclErr )
+import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr,
+ tcClassDecl2, getGenericInstances )
+import TcRnMonad
+import TcMType ( tcSkolSigType, checkValidTheta, checkValidInstHead,
+ checkInstTermination, instTypeErr,
+ checkAmbiguity, SourceTyCtxt(..) )
+import TcType ( mkClassPred, tyVarsOfType,
+ tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys,
+ SkolemInfo(InstSkol), tcSplitDFunTy, pprClassPred )
+import Inst ( tcInstClassOp, newDicts, instToId, showLIE,
+ getOverlapFlag, tcExtendLocalInstEnv )
+import InstEnv ( mkLocalInstance, instanceDFunId )
+import TcDeriv ( tcDeriving )
+import TcEnv ( InstInfo(..), InstBindings(..),
+ newDFunName, tcExtendIdEnv
)
-import HsPragmas -- ****** NEED TO SEE CONSTRUCTORS ******
-import Id -- lots of things
-import IdInfo -- ditto
-import Inst ( Inst, InstOrigin(..) )
-import InstEnv
-import Maybes ( catMaybes, mkLookupFun, maybeToBool, Maybe(..) )
-import Name ( getTagFromClassOpName )
-import NameTypes ( fromPrelude )
-import PlainCore ( escErrorMsg )
-import LIE ( nullLIE, mkLIE, unMkLIE, plusLIE, LIE )
+import TcHsType ( kcHsSigType, tcHsKindedType )
+import TcUnify ( checkSigTyVars )
+import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses )
+import Type ( zipOpenTvSubst, substTheta, substTys )
+import DataCon ( classDataCon )
+import Class ( classBigSig )
+import Var ( Id, idName, idType )
+import MkId ( mkDictFunId, rUNTIME_ERROR_ID )
+import FunDeps ( checkInstFDs )
+import Name ( Name, getSrcLoc )
+import Maybe ( catMaybes )
+import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart )
import ListSetOps ( minusList )
-import TCE ( TCE(..), UniqFM )
-import TVE ( mkTVE, TVE(..) )
-import Spec ( specTy )
-import TcContext ( tcContext )
-import TcBinds ( tcSigs, doSpecPragma )
-import TcGRHSs ( tcGRHSsAndBinds )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcInstanceType )
-import TcPragmas ( tcDictFunPragmas, tcGenPragmas )
-import TcSimplify ( tcSimplifyAndCheck, tcSimplifyThetas )
-import Unify ( unifyTauTy )
-import Unique ( cCallableClassKey, cReturnableClassKey )
-import Util
+import Outputable
+import Bag
+import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) )
+import FastString
\end{code}
Typechecking instance declarations is done in two passes. The first
-pass, made by @tcInstDecls1@,
-collects information to be used in the second pass.
+pass, made by @tcInstDecls1@, collects information to be used in the
+second pass.
This pre-processed info includes the as-yet-unprocessed bindings
inside the instance declaration. These are type-checked in the second
all the instance and value decls. Indeed that's the reason we need
two passes over the instance decls.
- instance c => k (t tvs) where b
-
-\begin{code}
-data InstInfo
- = InstInfo
- Class -- Class, k
- [TyVarTemplate] -- Type variables, tvs
- UniType -- The type at which the class is being
- -- instantiated
- ThetaType -- inst_decl_theta: the original context from the
- -- instance declaration. It constrains (some of)
- -- the TyVarTemplates above
- ThetaType -- dfun_theta: the inst_decl_theta, plus one
- -- element for each superclass; the "Mark
- -- Jones optimisation"
- Id -- The dfun id
- [Id] -- Constant methods (either all or none)
- RenamedMonoBinds -- Bindings, b
- Bool -- True <=> local instance decl
- FAST_STRING -- Name of module where this instance was
- -- defined.
- SrcLoc -- Source location assoc'd with this instance's defn
- [RenamedSig] -- User pragmas recorded for generating specialised methods
-\end{code}
+Here is the overall algorithm.
+Assume that we have an instance declaration
-Here is the overall algorithm. Assume that
+ instance c => k (t tvs) where b
\begin{enumerate}
\item
and $dbinds_super$ bind the superclass dictionaries sd1 \ldots sdm.
\end{enumerate}
-\begin{code}
-tcInstDecls1 :: E -> CE -> TCE -> [RenamedInstDecl] -> NF_TcM (Bag InstInfo)
-
-tcInstDecls1 e ce tce [] = returnNF_Tc emptyBag
-
-tcInstDecls1 e ce tce (inst_decl : rest)
- = tc_inst_1 inst_decl `thenNF_Tc` \ infos1 ->
- tcInstDecls1 e ce tce rest `thenNF_Tc` \ infos2 ->
- returnNF_Tc (infos1 `unionBags` infos2)
- where
- tc_inst_1 (InstDecl context class_name ty binds from_here modname imod uprags pragmas src_loc)
- =
- -- Prime error recovery and substitution pruning
- recoverTc emptyBag (
- addSrcLocTc src_loc (
-
- let
- clas = lookupCE ce class_name -- Renamer ensures this can't fail
-
- for_ccallable_or_creturnable
- = class_name == cCallableClass || class_name == cReturnableClass
- where
- cCallableClass = PreludeClass cCallableClassKey bottom
- cReturnableClass = PreludeClass cReturnableClassKey bottom
- bottom = panic "for_ccallable_etc"
-
- -- Make some new type variables, named as in the instance type
- ty_names = extractMonoTyNames (==) ty
- (tve,inst_tyvars,_) = mkTVE ty_names
- in
- -- Check the instance type, including its syntactic constraints
- babyTcMtoTcM (tcInstanceType ce tce tve from_here src_loc ty)
- `thenTc` \ inst_ty ->
-
- -- DEAL WITH THE INSTANCE CONTEXT
- babyTcMtoTcM (tcContext ce tce tve context) `thenTc` \ theta ->
-
- -- SOME BORING AND TURGID CHECKING:
- let
- inst_for_function_type = isFunType inst_ty
- -- sigh; it happens; must avoid tickling inst_tycon
-
- inst_tycon_maybe = getUniDataTyCon_maybe inst_ty
-
- inst_tycon = case inst_tycon_maybe of
- Just (xx,_,_) -> xx
- Nothing -> panic "tcInstDecls1:inst_tycon"
- in
- -------------------------------------------------------------
- -- It is illegal for a normal user's module to declare an
- -- instance for a Prelude-class/Prelude-type instance:
- checkTc (from_here -- really an inst decl in this module
- && fromPreludeCore clas -- prelude class
- && (inst_for_function_type -- prelude type
- || fromPreludeCore inst_tycon)
- && not (fromPrelude modname) -- we aren't compiling a Prelude mod
- )
- (preludeInstanceErr clas inst_ty src_loc) `thenTc_`
-
- -------------------------------------------------------------
- -- It is obviously illegal to have an explicit instance
- -- for something that we are also planning to `derive'.
- -- Note that an instance decl coming in from outside
- -- is probably just telling us about the derived instance
- -- (ToDo: actually check, if possible), so we mustn't flag
- -- it as an error.
- checkTc (from_here
- && not inst_for_function_type
- && clas `derivedFor` inst_tycon)
- (derivingWhenInstanceExistsErr clas inst_tycon) `thenTc_`
-
- -------------------------------------------------------------
- -- A user declaration of a _CCallable/_CReturnable instance
- -- must be for a "boxed primitive" type.
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- checkTc (for_ccallable_or_creturnable
- && from_here -- instance defined here
- && not (sw_chkr CompilingPrelude) -- which allows anything
- && (inst_for_function_type || -- a *function*??? hah!
- not (maybeToBool (maybeBoxedPrimType inst_ty)))) -- naughty, naughty
- (nonBoxedPrimCCallErr clas inst_ty src_loc) `thenTc_`
-
- -- END OF TURGIDITY; back to real fun
- -------------------------------------------------------------
-
- if (not inst_for_function_type && clas `derivedFor` inst_tycon) then
- -- Don't use this InstDecl; tcDeriv will make the
- -- InstInfo to be used in later processing.
- returnTc emptyBag
-
- else
- -- Make the dfun id and constant-method ids
- mkInstanceRelatedIds e
- from_here modname pragmas src_loc
- clas inst_tyvars inst_ty theta uprags
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- returnTc ( unitBag (
- InstInfo clas inst_tyvars inst_ty theta
- dfun_theta dfun_id const_meth_ids
- binds from_here modname src_loc uprags
- ))
- ))
-\end{code}
-
-
-Common bit of code shared with @tcDeriving@:
-\begin{code}
-mkInstanceRelatedIds e
- from_here modname inst_pragmas locn
- clas
- inst_tyvars inst_ty inst_decl_theta uprags
- = getUniqueTc `thenNF_Tc` \ uniq ->
- let
- (class_tyvar, super_classes, _, class_ops, _, _) = getClassBigSig clas
-
- super_class_theta = super_classes `zip` (repeat inst_ty)
-
-
- dfun_theta = case inst_decl_theta of
-
- [] -> [] -- If inst_decl_theta is empty, then we don't
- -- want to have any dict arguments, so that we can
- -- expose the constant methods.
-
- other -> inst_decl_theta ++ super_class_theta
- -- Otherwise we pass the superclass dictionaries to
- -- the dictionary function; the Mark Jones optimisation.
-
- dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_ty)
- in
- fixNF_Tc ( \ rec_dfun_id ->
- babyTcMtoNF_TcM (
- tcDictFunPragmas e dfun_ty rec_dfun_id inst_pragmas
- ) `thenNF_Tc` \ dfun_pragma_info ->
- let
- dfun_specenv = mkInstSpecEnv clas inst_ty inst_tyvars dfun_theta
- dfun_info = dfun_pragma_info `addInfo` dfun_specenv
- in
- returnNF_Tc (mkDictFunId uniq clas inst_ty dfun_ty from_here modname dfun_info)
- ) `thenNF_Tc` \ dfun_id ->
-
- -- Make the constant-method ids, if there are no type variables involved
- (if not (null inst_tyvars) -- ToDo: could also do this if theta is null...
- then
- returnNF_Tc []
- else
- let
- inline_mes = [ getTagFromClassOpName v | (InlineSig v _ _) <- uprags ]
-
- mk_const_meth op uniq
- = mkConstMethodId
- uniq
- clas op inst_ty
- meth_ty from_here modname info
- where
- is_elem = isIn "mkInstanceRelatedIds"
-
- info = if tag `is_elem` inline_mes
- then noIdInfo `addInfo_UF` (iWantToBeINLINEd UnfoldAlways)
- else noIdInfo
-
- tenv = [(class_tyvar, inst_ty)]
- tag = getClassOpTag op
- op_ty = getClassOpLocalType op
- meth_ty = instantiateTy tenv op_ty
- -- If you move to a null-theta version, you need a
- -- mkForallTy inst_tyvars here
-
- mk_constm_w_info (op, u, (name, prags)) -- ToDo: chk name?
- = fixNF_Tc ( \ rec_constm_id ->
-
- babyTcMtoNF_TcM (tcGenPragmas e (Just meth_ty) rec_constm_id prags)
- `thenNF_Tc` \ id_info ->
-
- returnNF_Tc (mkConstMethodId u clas op inst_ty meth_ty
- from_here modname id_info)
- )
- where
- tenv = [(class_tyvar, inst_ty)]
- op_ty = getClassOpLocalType op
- meth_ty = instantiateTy tenv op_ty
-
- in
- getUniquesTc (length class_ops) `thenNF_Tc` \ constm_uniqs ->
- (case inst_pragmas of
- ConstantInstancePragma _ name_pragma_pairs ->
- mapNF_Tc mk_constm_w_info (zip3 class_ops constm_uniqs name_pragma_pairs)
-
- other_inst_pragmas ->
- returnNF_Tc (zipWith mk_const_meth class_ops constm_uniqs)
- )
- ) `thenNF_Tc` \ const_meth_ids ->
-
- returnTc (dfun_id, dfun_theta, const_meth_ids)
-\end{code}
-
%************************************************************************
%* *
-\subsection{Converting instance info into suitable InstEnvs}
+\subsection{Extracting instance decls}
%* *
%************************************************************************
-\begin{code}
-buildInstanceEnvs :: Bag InstInfo
- -> TcM InstanceMapper
+Gather up the instance declarations from their various sources
-buildInstanceEnvs info
- = let
- cmp :: InstInfo -> InstInfo -> TAG_
- (InstInfo c1 _ _ _ _ _ _ _ _ _ _ _) `cmp` (InstInfo c2 _ _ _ _ _ _ _ _ _ _ _)
- = if c1 == c2 then EQ_ else if c1 < c2 then LT_ else GT_
+\begin{code}
+tcInstDecls1 -- Deal with both source-code and imported instance decls
+ :: [LTyClDecl Name] -- For deriving stuff
+ -> [LInstDecl Name] -- Source code instance decls
+ -> TcM (TcGblEnv, -- The full inst env
+ [InstInfo], -- Source-code instance decls to process;
+ -- contains all dfuns for this module
+ HsValBinds Name) -- Supporting bindings for derived instances
+
+tcInstDecls1 tycl_decls inst_decls
+ = checkNoErrs $
+ -- Stop if addInstInfos etc discovers any errors
+ -- (they recover, so that we get more than one error each round)
+
+ -- (1) Do the ordinary instance declarations
+ mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos ->
- info_by_class = equivClasses cmp (bagToList info)
- in
- mapTc buildInstanceEnv info_by_class `thenTc` \ inst_env_entries ->
let
- class_lookup_maybe_fn
- :: Class
- -> Maybe (ClassInstEnv, (ClassOp -> SpecEnv))
- class_lookup_fn
- :: InstanceMapper
-
- class_lookup_maybe_fn = mkLookupFun (==) inst_env_entries
-
- class_lookup_fn c
- = case class_lookup_maybe_fn c of
- Nothing -> (nullMEnv, \ o -> nullSpecEnv)
- Just xx -> xx
+ local_inst_info = catMaybes local_inst_infos
+ clas_decls = filter (isClassDecl.unLoc) tycl_decls
in
- returnTc class_lookup_fn
-\end{code}
+ -- (2) Instances from generic class declarations
+ getGenericInstances clas_decls `thenM` \ generic_inst_info ->
+
+ -- Next, construct the instance environment so far, consisting of
+ -- a) local instance decls
+ -- b) generic instances
+ addInsts local_inst_info $
+ addInsts generic_inst_info $
+
+ -- (3) Compute instances from "deriving" clauses;
+ -- This stuff computes a context for the derived instance decl, so it
+ -- needs to know about all the instances possible; hence inst_env4
+ tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) ->
+ addInsts deriv_inst_info $
+
+ getGblEnv `thenM` \ gbl_env ->
+ returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_inst_info,
+ deriv_binds)
+
+addInsts :: [InstInfo] -> TcM a -> TcM a
+addInsts infos thing_inside
+ = tcExtendLocalInstEnv (map iSpec infos) thing_inside
+\end{code}
\begin{code}
-buildInstanceEnv :: [InstInfo] -- Non-empty, and all for same class
- -> TcM (Class, (ClassInstEnv, (ClassOp -> SpecEnv)))
-
-buildInstanceEnv inst_infos@(info_for_one@(InstInfo clas _ _ _ _ _ _ _ _ _ _ _) : rest)
- = let
- ops = getClassOps clas
- no_of_ops = length ops
- in
- foldlTc addClassInstance
- (nullMEnv, nOfThem no_of_ops nullSpecEnv)
- inst_infos `thenTc` \ (class_inst_env, op_inst_envs) ->
+tcLocalInstDecl1 :: LInstDecl Name
+ -> TcM (Maybe InstInfo) -- Nothing if there was an error
+ -- A source-file instance declaration
+ -- Type-check all the stuff before the "where"
+ --
+ -- We check for respectable instance type, and context
+tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags))
+ = -- Prime error recovery, set source location
+ recoverM (returnM Nothing) $
+ setSrcSpan loc $
+ addErrCtxt (instDeclCtxt1 poly_ty) $
+
+ -- Typecheck the instance type itself. We can't use
+ -- tcHsSigType, because it's not a valid user type.
+ kcHsSigType poly_ty `thenM` \ kinded_ty ->
+ tcHsKindedType kinded_ty `thenM` \ poly_ty' ->
let
- class_op_maybe_fn :: ClassOp -> Maybe SpecEnv
- class_op_fn :: ClassOp -> SpecEnv
-
- class_op_maybe_fn = mkLookupFun (==) (ops `zip` op_inst_envs)
- -- They compare by ClassOp tags
- class_op_fn op
- = case class_op_maybe_fn op of
- Nothing -> nullSpecEnv
- Just xx -> xx
+ (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
+ in
+ checkValidTheta InstThetaCtxt theta `thenM_`
+ checkAmbiguity tyvars theta (tyVarsOfType tau) `thenM_`
+ checkValidInstHead tau `thenM` \ (clas,inst_tys) ->
+ checkInstTermination theta inst_tys `thenM_`
+ checkTc (checkInstFDs theta clas inst_tys)
+ (instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
+ newDFunName clas inst_tys (srcSpanStart loc) `thenM` \ dfun_name ->
+ getOverlapFlag `thenM` \ overlap_flag ->
+ let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys
+ ispec = mkLocalInstance dfun overlap_flag
in
- returnTc (clas, (class_inst_env, class_op_fn))
-\end{code}
-\begin{code}
-addClassInstance
- :: (ClassInstEnv, [SpecEnv])
- -> InstInfo
- -> TcM (ClassInstEnv, [SpecEnv]) -- One SpecEnv for each class op
-
-addClassInstance
- (class_inst_env, op_spec_envs)
- (InstInfo clas inst_tyvars inst_ty inst_decl_theta dfun_theta dfun_id const_meth_ids _ _ _ src_loc _)
- = getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- -- We anly add specialised/overlapped instances
- -- if we are specialising the overloading
---
--- ToDo ... This causes getConstMethodId errors!
---
--- if is_plain_instance inst_ty || sw_chkr SpecialiseOverloaded
--- then
-
- -- Insert into the class_inst_env first
- checkMaybeErrTc (addClassInst clas class_inst_env inst_ty dfun_id inst_tyvars dfun_theta src_loc)
- dupInstErr `thenTc` \ class_inst_env' ->
- let
- -- Adding the classop instances can't fail if the class instance itself didn't
- op_spec_envs' = case const_meth_ids of
- [] -> op_spec_envs
- other -> zipWith add_const_meth op_spec_envs const_meth_ids
- in
- returnTc (class_inst_env', op_spec_envs')
-
--- else
--- -- Drop this specialised/overlapped instance
--- returnTc (class_inst_env, op_spec_envs)
+ tcIsHsBoot `thenM` \ is_boot ->
+ checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags))
+ badBootDeclErr `thenM_`
+ returnM (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags }))
where
- add_const_meth spec_env meth_id
- = addOneToSpecEnv spec_env (SpecInfo (Just inst_ty:nothings) 1 meth_id)
- where
- (const_meth_tyvars,_) = splitForalls (getIdUniType meth_id)
- nothings = [Nothing | _ <- const_meth_tyvars]
- -- This only works if the constant method id only has its local polymorphism.
- -- If you want to have constant methods for
- -- instance Foo (a,b,c) where
- -- op x = ...
- -- then the constant method will be polymorphic in a,b,c, and
- -- the SpecInfo will need to be elaborated.
-
+ msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
+
%************************************************************************
%* *
\subsection{Type-checking instance declarations, pass 2}
%************************************************************************
\begin{code}
-tcInstDecls2 :: E
- -> Bag InstInfo
- -> NF_TcM (LIE, TypecheckedBinds)
-
-tcInstDecls2 e inst_decls
- = let
- -- Get type variables free in environment. Sadly, there may be
- -- some, because of the dreaded monomorphism restriction
- free_tyvars = tvOfE e
- in
- tcInstDecls2_help e free_tyvars (bagToList inst_decls)
-
-tcInstDecls2_help e free_tyvars [] = returnNF_Tc (nullLIE, EmptyBinds)
-
-tcInstDecls2_help e free_tyvars (inst_decl:inst_decls)
- = tcInstDecl2 e free_tyvars inst_decl `thenNF_Tc` \ (lie1, binds1) ->
- tcInstDecls2_help e free_tyvars inst_decls `thenNF_Tc` \ (lie2, binds2) ->
- returnNF_Tc (lie1 `plusLIE` lie2, binds1 `ThenBinds` binds2)
+tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo]
+ -> TcM (LHsBinds Id, TcLclEnv)
+-- (a) From each class declaration,
+-- generate any default-method bindings
+-- (b) From each instance decl
+-- generate the dfun binding
+
+tcInstDecls2 tycl_decls inst_decls
+ = do { -- (a) Default methods from class decls
+ (dm_binds_s, dm_ids_s) <- mapAndUnzipM tcClassDecl2 $
+ filter (isClassDecl.unLoc) tycl_decls
+ ; tcExtendIdEnv (concat dm_ids_s) $ do
+
+ -- (b) instance declarations
+ ; inst_binds_s <- mappM tcInstDecl2 inst_decls
+
+ -- Done
+ ; let binds = unionManyBags dm_binds_s `unionBags`
+ unionManyBags inst_binds_s
+ ; tcl_env <- getLclEnv -- Default method Ids in here
+ ; returnM (binds, tcl_env) }
\end{code}
-
======= New documentation starts here (Sept 92) ==============
-The main purpose of @tcInstDecl2@ is to return a @Binds@ which defines
+The main purpose of @tcInstDecl2@ is to return a @HsBinds@ which defines
the dictionary function for this instance declaration. For example
\begin{verbatim}
instance Foo a => Foo [a] where
Dict [op1, op2]
\end{verbatim}
-HOWEVER, if the instance decl has no type variables, then it returns a
-bigger @Binds@ with declarations for each method. For example
+HOWEVER, if the instance decl has no context, then it returns a
+bigger @HsBinds@ with declarations for each method. For example
\begin{verbatim}
- instance Foo Int where
+ instance Foo [a] where
op1 x = ...
op2 y = ...
\end{verbatim}
might produce
\begin{verbatim}
- dfun.Foo.Int = Dict [Foo.op1.Int, Foo.op2.Int]
- Foo.op1.Int x = ...
- Foo.op2.Int y = ...
+ dfun.Foo.List a = Dict [Foo.op1.List a, Foo.op2.List a]
+ const.Foo.op1.List a x = ...
+ const.Foo.op2.List a y = ...
\end{verbatim}
This group may be mutually recursive, because (for example) there may
be no method supplied for op2 in which case we'll get
\begin{verbatim}
- Foo.op2.Int = default.Foo.op2 dfun.Foo.Int
+ const.Foo.op2.List a = default.Foo.op2 (dfun.Foo.List a)
\end{verbatim}
that is, the default method applied to the dictionary at this type.
-\begin{code}
-tcInstDecl2 :: E
- -> [TyVar] -- Free in the environment
- -> InstInfo
- -> NF_TcM (LIE, TypecheckedBinds)
-\end{code}
+What we actually produce in either case is:
-First comes the easy case of a non-local instance decl.
+ AbsBinds [a] [dfun_theta_dicts]
+ [(dfun.Foo.List, d)] ++ (maybe) [(const.Foo.op1.List, op1), ...]
+ { d = (sd1,sd2, ..., op1, op2, ...)
+ op1 = ...
+ op2 = ...
+ }
-\begin{code}
-tcInstDecl2 e free_tyvars (InstInfo _ _ _ _ _ _ _ _ False{-not this module-} _ _ _)
- = returnNF_Tc (nullLIE, EmptyBinds)
-\end{code}
+The "maybe" says that we only ask AbsBinds to make global constant methods
+if the dfun_theta is empty.
-Now the case of a general local instance. For an instance declaration, say,
+
+For an instance declaration, say,
instance (C1 a, C2 b) => C (T a b) where
...
is the ``Mark Jones optimisation''. The stuff before the "=>" here
is the @dfun_theta@ below.
+First comes the easy case of a non-local instance decl.
+
+
\begin{code}
-tcInstDecl2
- e free_tyvars
- (InstInfo clas template_tyvars inst_ty_tmpl inst_decl_theta dfun_theta
- dfun_id const_meth_ids monobinds True{-from here-} inst_mod locn uprags)
- = let
- origin = InstanceDeclOrigin locn
- in
- recoverTc (nullLIE, EmptyBinds) (
- addSrcLocTc locn (
- pruneSubstTc free_tyvars (
-
- -- Get the class signature
- let (class_tyvar,
- super_classes, sc_sel_ids,
- class_ops, op_sel_ids, defm_ids) = getClassBigSig clas
- in
- -- Prime error recovery and substitution pruning. Instantiate
- -- dictionaries from the specified instance context. These
- -- dicts will be passed into the dictionary-construction
- -- function.
- copyTyVars template_tyvars `thenNF_Tc` \ (inst_env, inst_tyvars, inst_tyvar_tys) ->
- let
- inst_ty = instantiateTy inst_env inst_ty_tmpl
-
- inst_decl_theta' = instantiateThetaTy inst_env inst_decl_theta
- dfun_theta' = instantiateThetaTy inst_env dfun_theta
- sc_theta' = super_classes `zip` (repeat inst_ty)
- in
- newDicts origin sc_theta' `thenNF_Tc` \ sc_dicts' ->
- newDicts origin dfun_theta' `thenNF_Tc` \ dfun_arg_dicts' ->
- newDicts origin inst_decl_theta' `thenNF_Tc` \ inst_decl_dicts' ->
- let
- sc_dicts'_ids = map mkInstId sc_dicts'
- dfun_arg_dicts'_ids = map mkInstId dfun_arg_dicts'
- in
- -- Instantiate the dictionary being constructed
- -- and the dictionary-construction function
- newDicts origin [(clas,inst_ty)] `thenNF_Tc` \ [this_dict] ->
- let
- this_dict_id = mkInstId this_dict
- in
- -- Instantiate method variables
- listNF_Tc [ newMethodId sel_id inst_ty origin locn
- | sel_id <- op_sel_ids
- ] `thenNF_Tc` \ method_ids ->
- let
- method_insts = catMaybes (map isInstId_maybe method_ids)
- -- Extract Insts from those method ids which have them (most do)
- -- See notes on newMethodId
- in
- -- Collect available dictionaries
- let avail_insts = -- These insts are in scope; quite a few, eh?
- [this_dict] ++
- method_insts ++
- dfun_arg_dicts'
- in
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- let
- mk_method_expr
- = if sw_chkr OmitDefaultInstanceMethods then
- makeInstanceDeclNoDefaultExpr origin clas method_ids defm_ids inst_mod inst_ty
- else
- makeInstanceDeclDefaultMethodExpr origin this_dict_id class_ops defm_ids inst_ty
- in
- processInstBinds e free_tyvars mk_method_expr
- inst_tyvars avail_insts method_ids monobinds
- `thenTc` \ (insts_needed, method_mbinds) ->
- let
- -- Create the dict and method binds
- dict_bind
- = VarMonoBind this_dict_id (Dictionary sc_dicts'_ids method_ids)
+tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
- dict_and_method_binds
- = dict_bind `AndMonoBinds` method_mbinds
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+ = let
+ dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol dfun_id
+ inst_ty = idType dfun_id
in
- -- Check the overloading constraints of the methods and superclasses
- -- The global tyvars must be a fixed point of the substitution
- applyTcSubstAndCollectTyVars free_tyvars `thenNF_Tc` \ real_free_tyvars ->
- tcSimplifyAndCheck
- True -- Top level
- real_free_tyvars -- Global tyvars
- inst_tyvars -- Local tyvars
- avail_insts
- (sc_dicts' ++ insts_needed) -- Need to get defns for all these
- (BindSigCtxt method_ids)
- `thenTc` \ (const_insts, super_binds) ->
-
- -- Check that we *could* construct the superclass dictionaries,
- -- even though we are *actually* going to pass the superclass dicts in;
- -- the check ensures that the caller will never have a problem building
- -- them.
- tcSimplifyAndCheck
- False -- Doesn't matter; more efficient this way
- real_free_tyvars -- Global tyvars
- inst_tyvars -- Local tyvars
- inst_decl_dicts' -- The instance dictionaries available
- sc_dicts' -- The superclass dicationaries reqd
- SuperClassSigCtxt
- `thenTc_`
- -- Ignore the result; we're only doing
- -- this to make sure it can be done.
-
- -- Now process any SPECIALIZE pragmas for the methods
+ -- Prime error recovery
+ recoverM (returnM emptyLHsBinds) $
+ setSrcSpan (srcLocSpan (getSrcLoc dfun_id)) $
+ addErrCtxt (instDeclCtxt2 (idType dfun_id)) $
+
+ -- Instantiate the instance decl with skolem constants
+ tcSkolSigType rigid_info inst_ty `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
+ -- These inst_tyvars' scope over the 'where' part
+ -- Those tyvars are inside the dfun_id's type, which is a bit
+ -- bizarre, but OK so long as you realise it!
let
- spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ]
+ (clas, inst_tys') = tcSplitDFunHead inst_head'
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
- get_const_method_id name
- = const_meth_ids !! ((getTagFromClassOpName name) - 1)
- in
- tcSigs e [] spec_sigs `thenTc` \ sig_info ->
-
- mapAndUnzipTc (doSpecPragma e get_const_method_id) sig_info
- `thenTc` \ (spec_binds_s, spec_lie_s) ->
- let
- spec_lie = foldr plusLIE nullLIE spec_lie_s
- spec_binds = foldr AndMonoBinds EmptyMonoBinds spec_binds_s
-
- -- Complete the binding group, adding any spec_binds
- inst_binds
- = AbsBinds
- inst_tyvars
- dfun_arg_dicts'_ids
- ((this_dict_id,dfun_id) : (method_ids `zip` const_meth_ids))
- -- const_meth_ids will often be empty
- super_binds
- (RecBind dict_and_method_binds)
-
- `ThenBinds`
- SingleBind (NonRecBind spec_binds)
+ -- Instantiate the super-class context with inst_tys
+ sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta
+ origin = SigOrigin rigid_info
in
- -- Back-substitute
- applyTcSubstToBinds inst_binds `thenNF_Tc` \ final_inst_binds ->
-
- returnTc (mkLIE const_insts `plusLIE` spec_lie,
- final_inst_binds)
- )))
-\end{code}
-
-@mkMethodId@ manufactures an id for a local method.
-It's rather turgid stuff, because there are two cases:
-
- (a) For methods with no local polymorphism, we can make an Inst of the
- class-op selector function and a corresp InstId;
- which is good because then other methods which call
- this one will do so directly.
-
- (b) For methods with local polymorphism, we can't do this. For example,
-
- class Foo a where
- op :: (Num b) => a -> b -> a
-
- Here the type of the class-op-selector is
-
- forall a b. (Foo a, Num b) => a -> b -> a
-
- The locally defined method at (say) type Float will have type
-
- forall b. (Num b) => Float -> b -> Float
-
- and the one is not an instance of the other.
-
- So for these we just make a local (non-Inst) id with a suitable type.
-
-How disgusting.
-
-\begin{code}
-newMethodId sel_id inst_ty origin loc
- = let (sel_tyvars,sel_theta,sel_tau) = splitType (getIdUniType sel_id)
- (_:meth_theta) = sel_theta -- The local theta is all except the
- -- first element of the context
- in
- case sel_tyvars of
- -- Ah! a selector for a class op with no local polymorphism
- -- Build an Inst for this
- [clas_tyvar] -> newMethod origin sel_id [inst_ty] `thenNF_Tc` \ inst ->
- returnNF_Tc (mkInstId inst)
-
- -- Ho! a selector for a class op with local polymorphism.
- -- Just make a suitably typed local id for this
- (clas_tyvar:local_tyvars) ->
- let
- method_ty = instantiateTy [(clas_tyvar,inst_ty)]
- (mkSigmaTy local_tyvars meth_theta sel_tau)
- in
- getUniqueTc `thenNF_Tc` \ uniq ->
- returnNF_Tc (mkUserLocal (getOccurrenceName sel_id) uniq method_ty loc)
-\end{code}
-
-This function makes a default method which calls the global default method, at
-the appropriate instance type.
-
-See the notes under default decls in TcClassDcl.lhs.
-
-\begin{code}
-makeInstanceDeclDefaultMethodExpr
- :: InstOrigin
- -> Id
- -> [ClassOp]
- -> [Id]
- -> UniType
- -> Int
- -> NF_TcM TypecheckedExpr
-
-makeInstanceDeclDefaultMethodExpr origin this_dict_id class_ops defm_ids inst_ty tag
- = let
- (tyvar_tmpls, local_theta, _) = splitType (getClassOpLocalType class_op)
+ -- Create dictionary Ids from the specified instance contexts.
+ newDicts InstScOrigin sc_theta' `thenM` \ sc_dicts ->
+ newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts ->
+ newDicts origin [mkClassPred clas inst_tys'] `thenM` \ [this_dict] ->
+ -- Default-method Ids may be mentioned in synthesised RHSs,
+ -- but they'll already be in the environment.
+
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
in
- copyTyVars tyvar_tmpls `thenNF_Tc` \ (inst_env, tyvars, tys) ->
+ tcMethods origin clas inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
+
+ -- Figure out bindings for the superclass context
+ -- Don't include this_dict in the 'givens', else
+ -- sc_dicts get bound by just selecting from this_dict!!
+ addErrCtxt superClassCtxt
+ (tcSimplifySuperClasses inst_tyvars'
+ dfun_arg_dicts
+ sc_dicts) `thenM` \ sc_binds ->
+
+ -- It's possible that the superclass stuff might unified one
+ -- of the inst_tyavars' with something in the envt
+ checkSigTyVars inst_tyvars' `thenM_`
+
+ -- Deal with 'SPECIALISE instance' pragmas
let
- inst_theta = instantiateThetaTy inst_env local_theta
+ specs = case binds of
+ VanillaInst _ prags -> filter isSpecInstLSig prags
+ other -> []
in
- newDicts origin inst_theta `thenNF_Tc` \ local_dict_insts ->
+ tcPrags dfun_id specs `thenM` \ prags ->
+
+ -- Create the result bindings
let
- local_dicts = map mkInstId local_dict_insts
+ dict_constr = classDataCon clas
+ scs_and_meths = map instToId sc_dicts ++ meth_ids
+ this_dict_id = instToId this_dict
+ inline_prag | null dfun_arg_dicts = []
+ | otherwise = [InlinePrag (Inline AlwaysActive True)]
+ -- Always inline the dfun; this is an experimental decision
+ -- because it makes a big performance difference sometimes.
+ -- Often it means we can do the method selection, and then
+ -- inline the method as well. Marcin's idea; see comments below.
+ --
+ -- BUT: don't inline it if it's a constant dictionary;
+ -- we'll get all the benefit without inlining, and we get
+ -- a **lot** of code duplication if we inline it
+ --
+ -- See Note [Inline dfuns] below
+
+ dict_rhs
+ = mkHsConApp dict_constr inst_tys' (map HsVar scs_and_meths)
+ -- We don't produce a binding for the dict_constr; instead we
+ -- rely on the simplifier to unfold this saturated application
+ -- We do this rather than generate an HsCon directly, because
+ -- it means that the special cases (e.g. dictionary with only one
+ -- member) are dealt with by the common MkId.mkDataConWrapId code rather
+ -- than needing to be repeated here.
+
+ where
+ msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas)
+
+ dict_bind = noLoc (VarBind this_dict_id dict_rhs)
+ all_binds = dict_bind `consBag` (sc_binds `unionBags` meth_binds)
+
+ main_bind = noLoc $ AbsBinds
+ inst_tyvars'
+ (map instToId dfun_arg_dicts)
+ [(inst_tyvars', dfun_id, this_dict_id,
+ inline_prag ++ prags)]
+ all_binds
in
- returnNF_Tc (
- mkTyLam tyvars (
- mkDictLam local_dicts (
- mkDictApp (mkTyApp (Var defm_id)
- (inst_ty : tys))
- (this_dict_id:local_dicts)))
- )
- where
- idx = tag - 1
- class_op = class_ops !! idx
- defm_id = defm_ids !! idx
-
-
-makeInstanceDeclNoDefaultExpr
- :: InstOrigin
- -> Class
- -> [Id]
- -> [Id]
- -> FAST_STRING
- -> UniType
- -> Int
- -> NF_TcM TypecheckedExpr
-
-makeInstanceDeclNoDefaultExpr origin clas method_ids defm_ids inst_mod inst_ty tag
- = specTy origin (getIdUniType method_id) `thenNF_Tc` \ (tyvars, dicts, tau) ->
-
- (if not err_defm then
- pprTrace "Warning: "
- (ppCat [ppStr "Omitted default method for",
- ppr PprForUser clas_op, ppStr "in instance",
- ppPStr clas_name, pprParendUniType PprForUser inst_ty])
- else id) (
-
- returnNF_Tc (mkTyLam tyvars (
- mkDictLam (map mkInstId dicts) (
- App (mkTyApp (Var pAT_ERROR_ID) [tau])
- (Lit (StringLit (_PK_ error_msg))))))
- )
- where
- idx = tag - 1
- clas_op = (getClassOps clas) !! idx
- method_id = method_ids !! idx
- defm_id = defm_ids !! idx
-
- Just (_, _, err_defm) = isDefaultMethodId_maybe defm_id
-
- error_msg = "%E" -- => No explicit method for \"
- ++ escErrorMsg error_str
-
- error_str = _UNPK_ inst_mod ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser inst_ty)) ++ "."
- ++ (ppShow 80 (ppr PprForUser clas_op)) ++ "\""
-
- (_, clas_name) = getOrigName clas
-\end{code}
+ showLIE (text "instance") `thenM_`
+ returnM (unitBag main_bind)
-%************************************************************************
-%* *
-\subsection{Processing each method}
-%* *
-%************************************************************************
-
-@processInstBinds@ returns a @MonoBinds@ which binds
-all the method ids (which are passed in). It is used
- - both for instance decls,
- - and to compile the default-method declarations in a class decl.
-
-Any method ids which don't have a binding have a suitable default
-binding created for them. The actual right-hand side used is
-created using a function which is passed in, because the right thing to
-do differs between instance and class decls.
-
-\begin{code}
-processInstBinds
- :: E
- -> [TyVar] -- Free in envt
-
- -> (Int -> NF_TcM TypecheckedExpr) -- Function to make
- -- default method
-
- -> [TyVar] -- Tyvars for this instance decl
-
- -> [Inst] -- available Insts
-
- -> [Id] -- Local method ids
- -- (instance tyvars are free
- -- in their types),
- -- in tag order
- -> RenamedMonoBinds
-
- -> TcM ([Inst], -- These are required
- TypecheckedMonoBinds)
-
-processInstBinds e free_tyvars mk_method_expr inst_tyvars
- avail_insts method_ids monobinds
- =
- -- Process the explicitly-given method bindings
- processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids monobinds
- `thenTc` (\ (tags, insts_needed_in_methods, method_binds) ->
-
- -- Find the methods not handled, and make default method bindings for them.
- let unmentioned_tags = [1.. length method_ids] `minusList` tags
+tcMethods origin clas inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (VanillaInst monobinds uprags)
+ = -- Check that all the method bindings come from this class
+ let
+ sel_names = [idName sel_id | (sel_id, _) <- op_items]
+ bad_bndrs = collectHsBindBinders monobinds `minusList` sel_names
in
- makeDefaultMethods mk_method_expr unmentioned_tags method_ids
- `thenNF_Tc` (\ default_monobinds ->
-
- returnTc (insts_needed_in_methods,
- method_binds `AndMonoBinds` default_monobinds)
- ))
-\end{code}
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
-\begin{code}
-processInstBinds1
- :: E
- -> [TyVar] -- Global free tyvars
- -> [TyVar] -- Tyvars for this instance decl
- -> [Inst] -- available Insts
- -> [Id] -- Local method ids (instance tyvars are free),
- -- in tag order
- -> RenamedMonoBinds
- -> TcM ([Int], -- Class-op tags accounted for
- [Inst], -- These are required
- TypecheckedMonoBinds)
-
-processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids EmptyMonoBinds
- = returnTc ([], [], EmptyMonoBinds)
-
-processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids (AndMonoBinds mb1 mb2)
- = processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids mb1
- `thenTc` \ (op_tags1,dicts1,method_binds1) ->
- processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids mb2
- `thenTc` \ (op_tags2,dicts2,method_binds2) ->
- returnTc (op_tags1 ++ op_tags2,
- dicts1 ++ dicts2,
- AndMonoBinds method_binds1 method_binds2)
-\end{code}
-
-\begin{code}
-processInstBinds1 e free_tyvars inst_tyvars avail_insts method_ids mbind
- =
- -- Find what class op is being defined here. The complication is
- -- that we could have a PatMonoBind or a FunMonoBind. If the
- -- former, it should only bind a single variable, or else we're in
- -- trouble (I'm not sure what the static semantics of methods
- -- defined in a pattern binding with multiple patterns is!)
- -- Renamer has reduced us to these two cases.
+ -- Make the method bindings
let
- (op,locn) = case mbind of
- FunMonoBind op _ locn -> (op, locn)
- PatMonoBind (VarPatIn op) _ locn -> (op, locn)
-
- origin = InstanceDeclOrigin locn
+ mk_method_bind = mkMethodBind origin clas inst_tys' monobinds
in
- addSrcLocTc locn (
-
- -- Make a method id for the method
- let tag = getTagFromClassOpName op
- method_id = method_ids !! (tag-1)
- method_ty = getIdUniType method_id
+ mapAndUnzipM mk_method_bind op_items `thenM` \ (meth_insts, meth_infos) ->
+
+ -- And type check them
+ -- It's really worth making meth_insts available to the tcMethodBind
+ -- Consider instance Monad (ST s) where
+ -- {-# INLINE (>>) #-}
+ -- (>>) = ...(>>=)...
+ -- If we don't include meth_insts, we end up with bindings like this:
+ -- rec { dict = MkD then bind ...
+ -- then = inline_me (... (GHC.Base.>>= dict) ...)
+ -- bind = ... }
+ -- The trouble is that (a) 'then' and 'dict' are mutually recursive,
+ -- and (b) the inline_me prevents us inlining the >>= selector, which
+ -- would unravel the loop. Result: (>>) ends up as a loop breaker, and
+ -- is not inlined across modules. Rather ironic since this does not
+ -- happen without the INLINE pragma!
+ --
+ -- Solution: make meth_insts available, so that 'then' refers directly
+ -- to the local 'bind' rather than going via the dictionary.
+ --
+ -- BUT WATCH OUT! If the method type mentions the class variable, then
+ -- this optimisation is not right. Consider
+ -- class C a where
+ -- op :: Eq a => a
+ --
+ -- instance C Int where
+ -- op = op
+ -- The occurrence of 'op' on the rhs gives rise to a constraint
+ -- op at Int
+ -- The trouble is that the 'meth_inst' for op, which is 'available', also
+ -- looks like 'op at Int'. But they are not the same.
+ let
+ prag_fn = mkPragFun uprags
+ all_insts = avail_insts ++ catMaybes meth_insts
+ tc_method_bind = tcMethodBind inst_tyvars' dfun_theta' all_insts prag_fn
+ meth_ids = [meth_id | (_,meth_id,_) <- meth_infos]
in
- specTy origin method_ty `thenNF_Tc` \ (method_tyvars, method_dicts, method_tau) ->
-
- -- Build the result
- case (method_tyvars, method_dicts) of
-
- ([],[]) -> -- The simple case; no local polymorphism or overloading in the method
- -- Type check the method itself
- tcMethodBind e method_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
+ mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
+
+ returnM (meth_ids, unionManyBags meth_binds_s)
- -- Make sure that the instance tyvars havn't been
- -- unified with each other or with the method tyvars.
- -- The global tyvars must be a fixed point of the substitution
- applyTcSubstAndCollectTyVars free_tyvars `thenNF_Tc` \ real_free_tyvars ->
- checkSigTyVars real_free_tyvars inst_tyvars method_tau method_tau
- (MethodSigCtxt op method_tau) `thenTc_`
- returnTc ([tag], unMkLIE lieIop, mbind')
-
- other -> -- It's a locally-polymorphic and/or overloaded method; UGH!
-
- -- Make a new id for (a) the local, non-overloaded method
- -- and (b) the locally-overloaded method
- -- The latter is needed just so we can return an AbsBinds wrapped
- -- up inside a MonoBinds.
- newLocalWithGivenTy op method_tau `thenNF_Tc` \ local_meth_id ->
- newLocalWithGivenTy op method_ty `thenNF_Tc` \ copy_meth_id ->
+-- Derived newtype instances
+tcMethods origin clas inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (NewTypeDerived rep_tys)
+ = getInstLoc origin `thenM` \ inst_loc ->
+ mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) ->
+
+ tcSimplifyCheck
+ (ptext SLIT("newtype derived instance"))
+ inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds ->
- -- Typecheck the method
- tcMethodBind e local_meth_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
+ -- I don't think we have to do the checkSigTyVars thing
- -- Make sure that the instance tyvars haven't been
- -- unified with each other or with the method tyvars.
- -- The global tyvars must be a fixed point of the substitution
- applyTcSubstAndCollectTyVars free_tyvars `thenNF_Tc` \ real_free_tyvars ->
- checkSigTyVars real_free_tyvars (method_tyvars ++ inst_tyvars) method_tau method_tau
- (MethodSigCtxt op method_tau) `thenTc_`
+ returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds)
- -- Check the overloading part of the signature.
- -- Simplify everything fully, even though some
- -- constraints could "really" be left to the next
- -- level out. The case which forces this is
- --
- -- class Foo a where { op :: Bar a => a -> a }
- --
- -- Here we must simplify constraints on "a" to catch all
- -- the Bar-ish things.
- tcSimplifyAndCheck
- False -- Not top level
- real_free_tyvars
- (inst_tyvars ++ method_tyvars)
- (method_dicts ++ avail_insts)
- (unMkLIE lieIop)
- (MethodSigCtxt op method_ty) `thenTc` \ (f_dicts, dict_binds) ->
-
- returnTc ([tag],
- f_dicts,
- VarMonoBind method_id
- (Let
- (AbsBinds
- method_tyvars
- (map mkInstId method_dicts)
- [(local_meth_id, copy_meth_id)]
- dict_binds
- (NonRecBind mbind'))
- (Var copy_meth_id)))
- )
-\end{code}
-
-\begin{code}
-tcMethodBind :: E -> Id -> UniType -> RenamedMonoBinds
- -> TcM (TypecheckedMonoBinds, LIE)
-
-tcMethodBind e meth_id meth_ty (FunMonoBind name matches locn)
- = addSrcLocTc locn (
- tcMatchesFun e name meth_ty matches `thenTc` \ (rhs', lie) ->
- returnTc (FunMonoBind meth_id rhs' locn, lie)
- )
-
-tcMethodBind e meth_id meth_ty (PatMonoBind pat grhss_and_binds locn)
- -- pat is sure to be a (VarPatIn op)
- = addSrcLocTc locn (
- tcGRHSsAndBinds e grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) ->
- unifyTauTy meth_ty rhs_ty (PatMonoBindsCtxt pat grhss_and_binds) `thenTc_`
- returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie)
- )
+ where
+ do_one inst_loc (sel_id, _)
+ = -- The binding is like "op @ NewTy = op @ RepTy"
+ -- Make the *binder*, like in mkMethodBind
+ tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst ->
+
+ -- Make the *occurrence on the rhs*
+ tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst ->
+ let
+ meth_id = instToId meth_inst
+ in
+ return (meth_id, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst)
+
+ -- Instantiate rep_tys with the relevant type variables
+ -- This looks a bit odd, because inst_tyvars' are the skolemised version
+ -- of the type variables in the instance declaration; but rep_tys doesn't
+ -- have the skolemised version, so we substitute them in here
+ rep_tys' = substTys subst rep_tys
+ subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars')
\end{code}
-Creates bindings for the default methods, being the application of the
-appropriate global default method to the type of this instance decl.
+ ------------------------------
+ [Inline dfuns] Inlining dfuns unconditionally
+ ------------------------------
+
+The code above unconditionally inlines dict funs. Here's why.
+Consider this program:
+
+ test :: Int -> Int -> Bool
+ test x y = (x,y) == (y,x) || test y x
+ -- Recursive to avoid making it inline.
+
+This needs the (Eq (Int,Int)) instance. If we inline that dfun
+the code we end up with is good:
+
+ Test.$wtest =
+ \r -> case ==# [ww ww1] of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True ->
+ case ==# [ww1 ww] of wild1 {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+ };
+ Test.test = \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+If we don't inline the dfun, the code is not nearly as good:
+
+ (==) = case PrelTup.$fEq(,) PrelBase.$fEqInt PrelBase.$fEqInt of tpl {
+ PrelBase.:DEq tpl1 tpl2 -> tpl2;
+ };
+
+ Test.$wtest =
+ \r [ww ww1]
+ let { y = PrelBase.I#! [ww1]; } in
+ let { x = PrelBase.I#! [ww]; } in
+ let { sat_slx = PrelTup.(,)! [y x]; } in
+ let { sat_sly = PrelTup.(,)! [x y];
+ } in
+ case == sat_sly sat_slx of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+
+ Test.test =
+ \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+Why doesn't GHC inline $fEq? Because it looks big:
+
+ PrelTup.zdfEqZ1T{-rcX-}
+ = \ @ a{-reT-} :: * @ b{-reS-} :: *
+ zddEq{-rf6-} _Ks :: {PrelBase.Eq{-23-} a{-reT-}}
+ zddEq1{-rf7-} _Ks :: {PrelBase.Eq{-23-} b{-reS-}} ->
+ let {
+ zeze{-rf0-} _Kl :: (b{-reS-} -> b{-reS-} -> PrelBase.Bool{-3c-})
+ zeze{-rf0-} = PrelBase.zeze{-01L-}@ b{-reS-} zddEq1{-rf7-} } in
+ let {
+ zeze1{-rf3-} _Kl :: (a{-reT-} -> a{-reT-} -> PrelBase.Bool{-3c-})
+ zeze1{-rf3-} = PrelBase.zeze{-01L-} @ a{-reT-} zddEq{-rf6-} } in
+ let {
+ zeze2{-reN-} :: ((a{-reT-}, b{-reS-}) -> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ zeze2{-reN-} = \ ds{-rf5-} _Ks :: (a{-reT-}, b{-reS-})
+ ds1{-rf4-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ case ds{-rf5-}
+ of wild{-reW-} _Kd { (a1{-rf2-} _Ks, a2{-reZ-} _Ks) ->
+ case ds1{-rf4-}
+ of wild1{-reX-} _Kd { (b1{-rf1-} _Ks, b2{-reY-} _Ks) ->
+ PrelBase.zaza{-r4e-}
+ (zeze1{-rf3-} a1{-rf2-} b1{-rf1-})
+ (zeze{-rf0-} a2{-reZ-} b2{-reY-})
+ }
+ } } in
+ let {
+ a1{-reR-} :: ((a{-reT-}, b{-reS-})-> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ a1{-reR-} = \ a2{-reV-} _Ks :: (a{-reT-}, b{-reS-})
+ b1{-reU-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ PrelBase.not{-r6I-} (zeze2{-reN-} a2{-reV-} b1{-reU-})
+ } in
+ PrelBase.zdwZCDEq{-r8J-} @ (a{-reT-}, b{-reS-}) a1{-reR-} zeze2{-reN-})
+
+and it's not as bad as it seems, because it's further dramatically
+simplified: only zeze2 is extracted and its body is simplified.
-\begin{code}
-makeDefaultMethods
- :: (Int -> NF_TcM TypecheckedExpr) -- Function to make
- -- default method
- -> [Int] -- Tags for methods required
- -> [Id] -- Method names to bind, in tag order
- -> NF_TcM TypecheckedMonoBinds
-
-
-makeDefaultMethods mk_method_expr [] method_ids
- = returnNF_Tc EmptyMonoBinds
-
-makeDefaultMethods mk_method_expr (tag:tags) method_ids
- = mk_method_expr tag `thenNF_Tc` \ rhs ->
- makeDefaultMethods mk_method_expr tags method_ids `thenNF_Tc` \ meth_binds ->
-
- returnNF_Tc ((VarMonoBind method_id rhs) `AndMonoBinds` meth_binds)
- where
- method_id = method_ids !! (tag-1)
-\end{code}
%************************************************************************
%* *
-\subsection{Type-checking specialise instance pragmas}
+\subsection{Error messages}
%* *
%************************************************************************
\begin{code}
-tcSpecInstSigs :: E -> CE -> TCE
- -> Bag InstInfo -- inst decls seen (declared and derived)
- -> [RenamedSpecialisedInstanceSig] -- specialise instance upragmas
- -> TcM (Bag InstInfo) -- new, overlapped, inst decls
-
-tcSpecInstSigs e ce tce inst_infos []
- = returnTc emptyBag
-
-tcSpecInstSigs e ce tce inst_infos sigs
- = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos ->
- returnTc spec_inst_infos
+instDeclCtxt1 hs_inst_ty
+ = inst_decl_ctxt (case unLoc hs_inst_ty of
+ HsForAllTy _ _ _ (L _ (HsPredTy pred)) -> ppr pred
+ HsPredTy pred -> ppr pred
+ other -> ppr hs_inst_ty) -- Don't expect this
+instDeclCtxt2 dfun_ty
+ = inst_decl_ctxt (ppr (mkClassPred cls tys))
where
- tc_inst_spec_sigs inst_mapper []
- = returnNF_Tc emptyBag
- tc_inst_spec_sigs inst_mapper (sig:sigs)
- = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs ->
- returnNF_Tc (info_sig `unionBags` info_sigs)
-
-tcSpecInstSig :: E -> CE -> TCE
- -> Bag InstInfo
- -> InstanceMapper
- -> RenamedSpecialisedInstanceSig
- -> NF_TcM (Bag InstInfo)
-
-tcSpecInstSig e ce tce inst_infos inst_mapper (InstSpecSig class_name ty src_loc)
- = recoverTc emptyBag (
- addSrcLocTc src_loc (
- let
- clas = lookupCE ce class_name -- Renamer ensures this can't fail
-
- -- Make some new type variables, named as in the specialised instance type
- ty_names = extractMonoTyNames (==) ty
- (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names
- in
- babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty)
- `thenTc` \ inst_ty ->
- let
- maybe_tycon = case getUniDataTyCon_maybe inst_ty of
- Just (tc,_,_) -> Just tc
- Nothing -> Nothing
-
- maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos
- in
- -- Check that we have a local instance declaration to specialise
- checkMaybeTc maybe_unspec_inst
- (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_`
-
- -- Create tvs to substitute for tmpls while simplifying the context
- copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) ->
- let
- Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta
- _ _ _ binds True{-from here-} mod _ uprag) = maybe_unspec_inst
-
- subst = case matchTy unspec_inst_ty inst_ty of
- Just subst -> subst
- Nothing -> panic "tcSpecInstSig:matchTy"
-
- subst_theta = instantiateThetaTy subst unspec_theta
- subst_tv_theta = instantiateThetaTy tv_e subst_theta
-
- mk_spec_origin clas ty
- = InstanceSpecOrigin inst_mapper clas ty src_loc
- in
- tcSimplifyThetas mk_spec_origin subst_tv_theta
- `thenTc` \ simpl_tv_theta ->
- let
- simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ]
-
- tv_tmpl_map = inst_tv_tys `zipEqual` inst_tmpl_tys
- tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv
- in
- mkInstanceRelatedIds e True{-from here-} mod NoInstancePragmas src_loc
- clas inst_tmpls inst_ty simpl_theta uprag
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- (if sw_chkr SpecialiseTrace then
- pprTrace "Specialised Instance: "
- (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta,
- if null simpl_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendUniType PprDebug inst_ty],
- ppCat [ppStr " derived from:",
- if null unspec_theta then ppNil else ppr PprDebug unspec_theta,
- if null unspec_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendUniType PprDebug unspec_inst_ty]])
- else id) (
-
- returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta
- dfun_theta dfun_id const_meth_ids
- binds True{-from here-} mod src_loc uprag))
- )))
-
-
-lookup_unspec_inst clas maybe_tycon inst_infos
- = case filter (match_info match_inst_ty) (bagToList inst_infos) of
- [] -> Nothing
- (info:_) -> Just info
- where
- match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _)
- = from_here && clas == inst_clas &&
- match_ty inst_ty && is_plain_instance inst_ty
-
- match_inst_ty = case maybe_tycon of
- Just tycon -> match_tycon tycon
- Nothing -> match_fun
-
- match_tycon tycon inst_ty = case (getUniDataTyCon_maybe inst_ty) of
- Just (inst_tc,_,_) -> tycon == inst_tc
- Nothing -> False
-
- match_fun inst_ty = isFunType inst_ty
+ (_,_,cls,tys) = tcSplitDFunTy dfun_ty
+inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc
-is_plain_instance inst_ty
- = case (getUniDataTyCon_maybe inst_ty) of
- Just (_,tys,_) -> all isTyVarTemplateTy tys
- Nothing -> case maybeUnpackFunTy inst_ty of
- Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res
- Nothing -> error "TcInstDecls:is_plain_instance"
+superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration")
\end{code}
projects / ghc-hetmet.git / blobdiff