%
-% (c) The University of Glasgow 2006
+% (c) The University of Glasgow 2011
%
\begin{code}
-{-# OPTIONS -fno-warn-incomplete-patterns #-}
--- 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/Commentary/CodingStyle#Warnings
--- for details
-
-module Generics ( canDoGenerics, mkTyConGenericBinds,
- mkGenericRhs,
- validGenericInstanceType, validGenericMethodType
+
+module Generics ( canDoGenerics,
+ mkBindsRep, tc_mkRepTyCon, mkBindsMetaD,
+ MetaTyCons(..), metaTyCons2TyCons
) where
import DataCon
import TyCon
-import Name
+import Name hiding (varName)
+import Module (moduleName, moduleNameString)
import RdrName
import BasicTypes
-import Var
-import VarSet
-import Id
import TysWiredIn
import PrelNames
-
+
+-- For generation of representation types
+import TcEnv (tcLookupTyCon)
+import TcRnMonad
+import HscTypes
+import BuildTyCl
+
import SrcLoc
-import Util
import Bag
import Outputable
import FastString
#include "HsVersions.h"
\end{code}
-Roadmap of what's where in the Generics work.
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Parser
-No real checks.
-
-RnSource.rnHsType
- Checks that HsNumTy has a "1" in it.
-
-TcInstDcls.mkGenericInstance:
- Checks for invalid type patterns, such as f {| Int |}
-
-TcClassDcl.tcClassSig
- Checks for a method type that is too complicated;
- e.g. has for-alls or lists in it
- We could lift this restriction
-
-TcClassDecl.mkDefMethRhs
- Checks that the instance type is simple, in an instance decl
- where we let the compiler fill in a generic method.
- e.g. instance C (T Int)
- is not valid if C has generic methods.
-
-TcClassDecl.checkGenericClassIsUnary
- Checks that we don't have generic methods in a multi-parameter class
-
-TcClassDecl.checkDefaultBinds
- Checks that all the equations for a method in a class decl
- are generic, or all are non-generic
-
-
-
-Checking that the type constructors which are present in Generic
-patterns (not Unit, this is done differently) is done in mk_inst_info
-(TcInstDecls) in a call to tcHsType (TcMonoBinds). This means that
-HsOpTy is tied to Generic definitions which is not a very good design
-feature, indeed a bug. However, the check is easy to move from
-tcHsType back to mk_inst_info and everything will be fine. Also see
-bug #5. [I don't think that this is the case anymore after SPJ's latest
-changes in that regard. Delete this comment? -=chak/7Jun2]
-
-Generics.lhs
-
-Making generic information to put into a tycon. Constructs the
-representation type, which, I think, are not used later. Perhaps it is
-worth removing them from the GI datatype. Although it does get used in
-the construction of conversion functions (internally).
-
-TyCon.lhs
-
-Just stores generic information, accessible by tyConGenInfo or tyConGenIds.
-
-TysWiredIn.lhs
-
-Defines generic and other type and data constructors.
-
-This is sadly incomplete, but will be added to.
-
-
-Bugs & shortcomings of existing implementation:
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-2. Another pretty big bug I dscovered at the last minute when I was
-testing the code is that at the moment the type variable of the class
-is scoped over the entire declaration, including the patterns. For
-instance, if I have the following code,
-
-class Er a where
- ...
- er {| Plus a b |} (Inl x) (Inl y) = er x y
- er {| Plus a b |} (Inr x) (Inr y) = er x y
- er {| Plus a b |} _ _ = False
-
-and I print out the types of the generic patterns, I get the
-following. Note that all the variable names for "a" are the same,
-while for "b" they are all different.
-
-check_ty
- [std.Generics.Plus{-33u,i-} a{-r6Z-} b{-r7g-},
- std.Generics.Plus{-33u,i-} a{-r6Z-} b{-r7m-},
- std.Generics.Plus{-33u,i-} a{-r6Z-} b{-r7p-}]
-
-This is a bug as if I change the code to
-
- er {| Plus c b |} (Inl x) (Inl y) = er x y
-
-all the names come out to be different.
-
-Thus, all the types (Plus a b) come out to be different, so I cannot
-compare them and test whether they are all the same and thus cannot
-return an error if the type variables are different.
-
-Temporary fix/hack. I am not checking for this, I just assume they are
-the same, see line "check_ty = True" in TcInstDecls. When we resolve
-the issue with variables, though - I assume that we will make them to
-be the same in all the type patterns, jus uncomment the check and
-everything should work smoothly.
-
-Hence, I have also left the rather silly construction of:
-* extracting all the type variables from all the types
-* putting them *all* into the environment
-* typechecking all the types
-* selecting one of them and using it as the instance_ty.
-
-(the alternative is to make sure that all the types are the same,
-taking one, extracting its variables, putting them into the environment,
-type checking it, using it as the instance_ty)
-
-6. What happens if we do not supply all of the generic patterns? At
-the moment, the compiler crashes with an error message "Non-exhaustive
-patterns in a generic declaration"
-
-
-What has not been addressed:
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Contexts. In the generated instance declarations for the 3 primitive
-type constructors, we need contexts. It is unclear what those should
-be. At the moment, we always say eg. (Eq a, Eq b) => Eq (Plus a b)
-
-Type application. We have type application in expressions
-(essentially) on the lhs of an equation. Do we want to allow it on the
-RHS?
-
-Scoping of type variables in a generic definition. At the moment, (see
-TcInstDecls) we extract the type variables inside the type patterns
-and add them to the environment. See my bug #2 above. This seems pretty
-important.
-
-
-
-%************************************************************************
-%* *
-\subsection{Getting the representation type out}
-%* *
-%************************************************************************
-
-\begin{code}
-validGenericInstanceType :: Type -> Bool
- -- Checks for validity of the type pattern in a generic
- -- declaration. It's ok to have
- -- f {| a + b |} ...
- -- but it's not OK to have
- -- f {| a + Int |}
-
-validGenericInstanceType inst_ty
- = case tcSplitTyConApp_maybe inst_ty of
- Just (tycon, tys) -> all isTyVarTy tys && tyConName tycon `elem` genericTyConNames
- Nothing -> False
-
-validGenericMethodType :: Type -> Bool
- -- At the moment we only allow method types built from
- -- * type variables
- -- * function arrow
- -- * boxed tuples
- -- * lists
- -- * an arbitrary type not involving the class type variables
- -- e.g. this is ok: forall b. Ord b => [b] -> a
- -- where a is the class variable
-validGenericMethodType ty
- = valid tau
- where
- (local_tvs, _, tau) = tcSplitSigmaTy ty
-
- valid ty
- | not (isTauTy ty) = False -- Note [Higher ramk methods]
- | isTyVarTy ty = True
- | no_tyvars_in_ty = True
- | otherwise = case tcSplitTyConApp_maybe ty of
- Just (tc,tys) -> valid_tycon tc && all valid tys
- Nothing -> False
- where
- no_tyvars_in_ty = all (`elem` local_tvs) (varSetElems (tyVarsOfType ty))
-
- valid_tycon tc = tc == funTyCon || tc == listTyCon || isBoxedTupleTyCon tc
- -- Compare bimapApp, below
-\end{code}
-
-
%************************************************************************
%* *
\subsection{Generating representation types}
%************************************************************************
\begin{code}
-canDoGenerics :: [DataCon] -> Bool
+canDoGenerics :: TyCon -> Maybe SDoc
-- Called on source-code data types, to see if we should generate
--- generic functions for them. (This info is recorded in the interface file for
--- imported data types.)
-
-canDoGenerics data_cons
- = not (any bad_con data_cons) -- See comment below
- && not (null data_cons) -- No values of the type
+-- generic functions for them.
+-- Nothing == yes
+-- Just s == no, because of `s`
+
+canDoGenerics tycon
+ = mergeErrors (
+ -- We do not support datatypes with context
+ (if (not (null (tyConStupidTheta tycon)))
+ then (Just (ppr tycon <+> text "must not have a datatype context"))
+ else Nothing)
+ -- We don't like type families
+ : (if (isFamilyTyCon tycon)
+ then (Just (ppr tycon <+> text "must not be a family instance"))
+ else Nothing)
+ -- See comment below
+ : (map bad_con (tyConDataCons tycon)))
where
- bad_con dc = any bad_arg_type (dataConOrigArgTys dc) || not (isVanillaDataCon dc)
- -- If any of the constructor has an unboxed type as argument,
- -- then we can't build the embedding-projection pair, because
- -- it relies on instantiating *polymorphic* sum and product types
- -- at the argument types of the constructors
+ -- If any of the constructor has an unboxed type as argument,
+ -- then we can't build the embedding-projection pair, because
+ -- it relies on instantiating *polymorphic* sum and product types
+ -- at the argument types of the constructors
+ bad_con dc = if (any bad_arg_type (dataConOrigArgTys dc))
+ then (Just (ppr dc <+> text "must not have unlifted or polymorphic arguments"))
+ else (if (not (isVanillaDataCon dc))
+ then (Just (ppr dc <+> text "must be a vanilla data constructor"))
+ else Nothing)
+
-- Nor can we do the job if it's an existential data constructor,
-- Nor if the args are polymorphic types (I don't think)
bad_arg_type ty = isUnLiftedType ty || not (isTauTy ty)
+
+ mergeErrors :: [Maybe SDoc] -> Maybe SDoc
+ mergeErrors [] = Nothing
+ mergeErrors ((Just s):t) = case mergeErrors t of
+ Nothing -> Just s
+ Just s' -> Just (s <> text ", and" $$ s')
+ mergeErrors (Nothing :t) = mergeErrors t
\end{code}
%************************************************************************
\begin{code}
type US = Int -- Local unique supply, just a plain Int
-type FromAlt = (LPat RdrName, LHsExpr RdrName)
+type Alt = (LPat RdrName, LHsExpr RdrName)
-mkTyConGenericBinds :: TyCon -> LHsBinds RdrName
-mkTyConGenericBinds tycon
- = unitBag (L loc (mkFunBind (L loc from_RDR) from_matches))
- `unionBags`
+-- Bindings for the Generic instance
+mkBindsRep :: TyCon -> LHsBinds RdrName
+mkBindsRep tycon =
+ unitBag (L loc (mkFunBind (L loc from_RDR) from_matches))
+ `unionBags`
unitBag (L loc (mkFunBind (L loc to_RDR) to_matches))
+ where
+ from_matches = [mkSimpleHsAlt pat rhs | (pat,rhs) <- from_alts]
+ to_matches = [mkSimpleHsAlt pat rhs | (pat,rhs) <- to_alts ]
+ loc = srcLocSpan (getSrcLoc tycon)
+ datacons = tyConDataCons tycon
+
+ -- Recurse over the sum first
+ from_alts, to_alts :: [Alt]
+ (from_alts, to_alts) = mkSum (1 :: US) tycon datacons
+
+--------------------------------------------------------------------------------
+-- The type instance synonym and synonym
+-- type instance Rep (D a b) = Rep_D a b
+-- type Rep_D a b = ...representation type for D ...
+--------------------------------------------------------------------------------
+
+tc_mkRepTyCon :: TyCon -- The type to generate representation for
+ -> MetaTyCons -- Metadata datatypes to refer to
+ -> TcM TyCon -- Generated representation0 type
+tc_mkRepTyCon tycon metaDts =
+-- Consider the example input tycon `D`, where data D a b = D_ a
+ do { -- `rep0` = GHC.Generics.Rep (type family)
+ rep0 <- tcLookupTyCon repTyConName
+
+ -- `rep0Ty` = D1 ... (C1 ... (S1 ... (Rec0 a))) :: * -> *
+ ; rep0Ty <- tc_mkRepTy tycon metaDts
+
+ -- `rep_name` is a name we generate for the synonym
+ ; rep_name <- newImplicitBinder (tyConName tycon) mkGenR
+ ; let -- `tyvars` = [a,b]
+ tyvars = tyConTyVars tycon
+
+ -- rep0Ty has kind * -> *
+ rep_kind = liftedTypeKind `mkArrowKind` liftedTypeKind
+
+ -- `appT` = D a b
+ appT = [mkTyConApp tycon (mkTyVarTys tyvars)]
+
+ ; buildSynTyCon rep_name tyvars (SynonymTyCon rep0Ty) rep_kind
+ NoParentTyCon (Just (rep0, appT)) }
+
+--------------------------------------------------------------------------------
+-- Type representation
+--------------------------------------------------------------------------------
+
+tc_mkRepTy :: -- The type to generate representation for
+ TyCon
+ -- Metadata datatypes to refer to
+ -> MetaTyCons
+ -- Generated representation0 type
+ -> TcM Type
+tc_mkRepTy tycon metaDts =
+ do
+ d1 <- tcLookupTyCon d1TyConName
+ c1 <- tcLookupTyCon c1TyConName
+ s1 <- tcLookupTyCon s1TyConName
+ nS1 <- tcLookupTyCon noSelTyConName
+ rec0 <- tcLookupTyCon rec0TyConName
+ par0 <- tcLookupTyCon par0TyConName
+ u1 <- tcLookupTyCon u1TyConName
+ v1 <- tcLookupTyCon v1TyConName
+ plus <- tcLookupTyCon sumTyConName
+ times <- tcLookupTyCon prodTyConName
+
+ let mkSum' a b = mkTyConApp plus [a,b]
+ mkProd a b = mkTyConApp times [a,b]
+ mkRec0 a = mkTyConApp rec0 [a]
+ mkPar0 a = mkTyConApp par0 [a]
+ mkD a = mkTyConApp d1 [metaDTyCon, sumP (tyConDataCons a)]
+ mkC i d a = mkTyConApp c1 [d, prod i (dataConOrigArgTys a)
+ (null (dataConFieldLabels a))]
+ -- This field has no label
+ mkS True _ a = mkTyConApp s1 [mkTyConTy nS1, a]
+ -- This field has a label
+ mkS False d a = mkTyConApp s1 [d, a]
+
+ sumP [] = mkTyConTy v1
+ sumP l = ASSERT (length metaCTyCons == length l)
+ foldBal mkSum' [ mkC i d a
+ | (d,(a,i)) <- zip metaCTyCons (zip l [0..])]
+ -- The Bool is True if this constructor has labelled fields
+ prod :: Int -> [Type] -> Bool -> Type
+ prod i [] _ = ASSERT (length metaSTyCons > i)
+ ASSERT (length (metaSTyCons !! i) == 0)
+ mkTyConTy u1
+ prod i l b = ASSERT (length metaSTyCons > i)
+ ASSERT (length l == length (metaSTyCons !! i))
+ foldBal mkProd [ arg d t b
+ | (d,t) <- zip (metaSTyCons !! i) l ]
+
+ arg :: Type -> Type -> Bool -> Type
+ arg d t b = mkS b d (recOrPar t (getTyVar_maybe t))
+ -- Argument is not a type variable, use Rec0
+ recOrPar t Nothing = mkRec0 t
+ -- Argument is a type variable, use Par0
+ recOrPar t (Just _) = mkPar0 t
+
+ metaDTyCon = mkTyConTy (metaD metaDts)
+ metaCTyCons = map mkTyConTy (metaC metaDts)
+ metaSTyCons = map (map mkTyConTy) (metaS metaDts)
+
+ return (mkD tycon)
+
+--------------------------------------------------------------------------------
+-- Meta-information
+--------------------------------------------------------------------------------
+
+data MetaTyCons = MetaTyCons { -- One meta datatype per dataype
+ metaD :: TyCon
+ -- One meta datatype per constructor
+ , metaC :: [TyCon]
+ -- One meta datatype per selector per constructor
+ , metaS :: [[TyCon]] }
+
+instance Outputable MetaTyCons where
+ ppr (MetaTyCons d c s) = ppr d <+> ppr c <+> ppr s
+
+metaTyCons2TyCons :: MetaTyCons -> [TyCon]
+metaTyCons2TyCons (MetaTyCons d c s) = d : c ++ concat s
+
+
+-- Bindings for Datatype, Constructor, and Selector instances
+mkBindsMetaD :: FixityEnv -> TyCon
+ -> ( LHsBinds RdrName -- Datatype instance
+ , [LHsBinds RdrName] -- Constructor instances
+ , [[LHsBinds RdrName]]) -- Selector instances
+mkBindsMetaD fix_env tycon = (dtBinds, allConBinds, allSelBinds)
+ where
+ mkBag l = foldr1 unionBags
+ [ unitBag (L loc (mkFunBind (L loc name) matches))
+ | (name, matches) <- l ]
+ dtBinds = mkBag [ (datatypeName_RDR, dtName_matches)
+ , (moduleName_RDR, moduleName_matches)]
+
+ allConBinds = map conBinds datacons
+ conBinds c = mkBag ( [ (conName_RDR, conName_matches c)]
+ ++ ifElseEmpty (dataConIsInfix c)
+ [ (conFixity_RDR, conFixity_matches c) ]
+ ++ ifElseEmpty (length (dataConFieldLabels c) > 0)
+ [ (conIsRecord_RDR, conIsRecord_matches c) ]
+ )
+
+ ifElseEmpty p x = if p then x else []
+ fixity c = case lookupFixity fix_env (dataConName c) of
+ Fixity n InfixL -> buildFix n leftAssocDataCon_RDR
+ Fixity n InfixR -> buildFix n rightAssocDataCon_RDR
+ Fixity n InfixN -> buildFix n notAssocDataCon_RDR
+ buildFix n assoc = nlHsApps infixDataCon_RDR [nlHsVar assoc
+ , nlHsIntLit (toInteger n)]
+
+ allSelBinds = map (map selBinds) datasels
+ selBinds s = mkBag [(selName_RDR, selName_matches s)]
+
+ loc = srcLocSpan (getSrcLoc tycon)
+ mkStringLHS s = [mkSimpleHsAlt nlWildPat (nlHsLit (mkHsString s))]
+ datacons = tyConDataCons tycon
+ datasels = map dataConFieldLabels datacons
+
+ dtName_matches = mkStringLHS . showPpr . nameOccName . tyConName
+ $ tycon
+ moduleName_matches = mkStringLHS . moduleNameString . moduleName
+ . nameModule . tyConName $ tycon
+
+ conName_matches c = mkStringLHS . showPpr . nameOccName
+ . dataConName $ c
+ conFixity_matches c = [mkSimpleHsAlt nlWildPat (fixity c)]
+ conIsRecord_matches _ = [mkSimpleHsAlt nlWildPat (nlHsVar true_RDR)]
+
+ selName_matches s = mkStringLHS (showPpr (nameOccName s))
+
+
+--------------------------------------------------------------------------------
+-- Dealing with sums
+--------------------------------------------------------------------------------
+
+mkSum :: US -- Base for generating unique names
+ -> TyCon -- The type constructor
+ -> [DataCon] -- The data constructors
+ -> ([Alt], -- Alternatives for the T->Trep "from" function
+ [Alt]) -- Alternatives for the Trep->T "to" function
+
+-- Datatype without any constructors
+mkSum _us tycon [] = ([from_alt], [to_alt])
+ where
+ from_alt = (nlWildPat, mkM1_E (makeError errMsgFrom))
+ to_alt = (mkM1_P nlWildPat, makeError errMsgTo)
+ -- These M1s are meta-information for the datatype
+ makeError s = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString s))
+ errMsgFrom = "No generic representation for empty datatype " ++ showPpr tycon
+ errMsgTo = "No values for empty datatype " ++ showPpr tycon
+
+-- Datatype with at least one constructor
+mkSum us _tycon datacons =
+ unzip [ mk1Sum us i (length datacons) d | (d,i) <- zip datacons [1..] ]
+
+-- Build the sum for a particular constructor
+mk1Sum :: US -- Base for generating unique names
+ -> Int -- The index of this constructor
+ -> Int -- Total number of constructors
+ -> DataCon -- The data constructor
+ -> (Alt, -- Alternative for the T->Trep "from" function
+ Alt) -- Alternative for the Trep->T "to" function
+mk1Sum us i n datacon = (from_alt, to_alt)
where
- from_matches = [mkSimpleHsAlt pat rhs | (pat,rhs) <- from_alts]
- to_matches = [mkSimpleHsAlt to_pat to_body]
- loc = srcLocSpan (getSrcLoc tycon)
- datacons = tyConDataCons tycon
- (from_RDR, to_RDR) = mkGenericNames tycon
-
- -- Recurse over the sum first
- from_alts :: [FromAlt]
- (from_alts, to_pat, to_body) = mk_sum_stuff init_us datacons
- init_us = 1::Int -- Unique supply
-
-----------------------------------------------------
--- Dealing with sums
-----------------------------------------------------
-
-mk_sum_stuff :: US -- Base for generating unique names
- -> [DataCon] -- The data constructors
- -> ([FromAlt], -- Alternatives for the T->Trep "from" function
- InPat RdrName, LHsExpr RdrName) -- Arg and body of the Trep->T "to" function
-
--- For example, given
--- data T = C | D Int Int Int
---
--- mk_sum_stuff v [C,D] = ([C -> Inl Unit, D a b c -> Inr (a :*: (b :*: c))],
--- case cd of { Inl u -> C;
--- Inr abc -> case abc of { a :*: bc ->
--- case bc of { b :*: c ->
--- D a b c }} },
--- cd)
-
-mk_sum_stuff us [datacon]
- = ([from_alt], to_pat, to_body_fn app_exp)
- where
- n_args = dataConSourceArity datacon -- Existentials already excluded
-
- datacon_vars = map mkGenericLocal [us .. us+n_args-1]
- us' = us + n_args
-
- datacon_rdr = getRdrName datacon
- app_exp = nlHsVarApps datacon_rdr datacon_vars
- from_alt = (nlConVarPat datacon_rdr datacon_vars, from_alt_rhs)
-
- (_, from_alt_rhs, to_pat, to_body_fn) = mk_prod_stuff us' datacon_vars
-
-mk_sum_stuff us datacons
- = (wrap inlDataCon_RDR l_from_alts ++ wrap inrDataCon_RDR r_from_alts,
- nlVarPat to_arg,
- noLoc (HsCase (nlHsVar to_arg)
- (mkMatchGroup [mkSimpleHsAlt (nlConPat inlDataCon_RDR [l_to_pat]) l_to_body,
- mkSimpleHsAlt (nlConPat inrDataCon_RDR [r_to_pat]) r_to_body])))
+ n_args = dataConSourceArity datacon -- Existentials already excluded
+
+ datacon_vars = map mkGenericLocal [us .. us+n_args-1]
+ us' = us + n_args
+
+ datacon_rdr = getRdrName datacon
+ app_exp = nlHsVarApps datacon_rdr datacon_vars
+
+ from_alt = (nlConVarPat datacon_rdr datacon_vars, from_alt_rhs)
+ from_alt_rhs = mkM1_E (genLR_E i n (mkProd_E us' datacon_vars))
+
+ to_alt = (mkM1_P (genLR_P i n (mkProd_P us' datacon_vars)), to_alt_rhs)
+ -- These M1s are meta-information for the datatype
+ to_alt_rhs = app_exp
+
+-- Generates the L1/R1 sum pattern
+genLR_P :: Int -> Int -> LPat RdrName -> LPat RdrName
+genLR_P i n p
+ | n == 0 = error "impossible"
+ | n == 1 = p
+ | i <= div n 2 = nlConPat l1DataCon_RDR [genLR_P i (div n 2) p]
+ | otherwise = nlConPat r1DataCon_RDR [genLR_P (i-m) (n-m) p]
+ where m = div n 2
+
+-- Generates the L1/R1 sum expression
+genLR_E :: Int -> Int -> LHsExpr RdrName -> LHsExpr RdrName
+genLR_E i n e
+ | n == 0 = error "impossible"
+ | n == 1 = e
+ | i <= div n 2 = nlHsVar l1DataCon_RDR `nlHsApp` genLR_E i (div n 2) e
+ | otherwise = nlHsVar r1DataCon_RDR `nlHsApp` genLR_E (i-m) (n-m) e
+ where m = div n 2
+
+--------------------------------------------------------------------------------
+-- Dealing with products
+--------------------------------------------------------------------------------
+
+-- Build a product expression
+mkProd_E :: US -- Base for unique names
+ -> [RdrName] -- List of variables matched on the lhs
+ -> LHsExpr RdrName -- Resulting product expression
+mkProd_E _ [] = mkM1_E (nlHsVar u1DataCon_RDR)
+mkProd_E _ vars = mkM1_E (foldBal prod appVars)
+ -- These M1s are meta-information for the constructor
where
- (l_datacons, r_datacons) = splitInHalf datacons
- (l_from_alts, l_to_pat, l_to_body) = mk_sum_stuff us' l_datacons
- (r_from_alts, r_to_pat, r_to_body) = mk_sum_stuff us' r_datacons
-
- to_arg = mkGenericLocal us
- us' = us+1
-
- wrap :: RdrName -> [FromAlt] -> [FromAlt]
- -- Wrap an application of the Inl or Inr constructor round each alternative
- wrap dc alts = [(pat, noLoc (HsApp (nlHsVar dc) rhs)) | (pat,rhs) <- alts]
-
-
-----------------------------------------------------
--- Dealing with products
-----------------------------------------------------
-mk_prod_stuff :: US -- Base for unique names
- -> [RdrName] -- arg-ids; args of the original user-defined constructor
- -- They are bound enclosing from_rhs
- -- Please bind these in the to_body_fn
- -> (US, -- Depleted unique-name supply
- LHsExpr RdrName, -- from-rhs: puts together the representation from the arg_ids
- InPat RdrName, -- to_pat:
- LHsExpr RdrName -> LHsExpr RdrName) -- to_body_fn: takes apart the representation
-
--- For example:
--- mk_prod_stuff abc [a,b,c] = ( a :*: (b :*: c),
--- abc,
--- \<body-code> -> case abc of { a :*: bc ->
--- case bc of { b :*: c ->
--- <body-code> )
-
--- We need to use different uniques in the branches
--- because the returned to_body_fns are nested.
--- Hence the returned unqique-name supply
-
-mk_prod_stuff us [] -- Unit case
- = (us+1,
- nlHsVar genUnitDataCon_RDR,
- noLoc (SigPatIn (nlVarPat (mkGenericLocal us))
- (noLoc (HsTyVar (getRdrName genUnitTyConName)))),
- -- Give a signature to the pattern so we get
- -- data S a = Nil | S a
- -- toS = \x -> case x of { Inl (g :: Unit) -> Nil
- -- Inr x -> S x }
- -- The (:: Unit) signature ensures that we'll infer the right
- -- type for toS. If we leave it out, the type is too polymorphic
-
- \x -> x)
-
-mk_prod_stuff us [arg_var] -- Singleton case
- = (us, nlHsVar arg_var, nlVarPat arg_var, \x -> x)
-
-mk_prod_stuff us arg_vars -- Two or more
- = (us'',
- nlHsApps crossDataCon_RDR [l_alt_rhs, r_alt_rhs],
- nlVarPat to_arg,
--- gaw 2004 FIX?
- \x -> noLoc (HsCase (nlHsVar to_arg)
- (mkMatchGroup [mkSimpleHsAlt pat (l_to_body_fn (r_to_body_fn x))])))
+ appVars = map wrapArg_E vars
+ prod a b = prodDataCon_RDR `nlHsApps` [a,b]
+
+wrapArg_E :: RdrName -> LHsExpr RdrName
+wrapArg_E v = mkM1_E (k1DataCon_RDR `nlHsVarApps` [v])
+ -- This M1 is meta-information for the selector
+
+-- Build a product pattern
+mkProd_P :: US -- Base for unique names
+ -> [RdrName] -- List of variables to match
+ -> LPat RdrName -- Resulting product pattern
+mkProd_P _ [] = mkM1_P (nlNullaryConPat u1DataCon_RDR)
+mkProd_P _ vars = mkM1_P (foldBal prod appVars)
+ -- These M1s are meta-information for the constructor
where
- to_arg = mkGenericLocal us
- (l_arg_vars, r_arg_vars) = splitInHalf arg_vars
- (us', l_alt_rhs, l_to_pat, l_to_body_fn) = mk_prod_stuff (us+1) l_arg_vars
- (us'', r_alt_rhs, r_to_pat, r_to_body_fn) = mk_prod_stuff us' r_arg_vars
- pat = nlConPat crossDataCon_RDR [l_to_pat, r_to_pat]
-
-splitInHalf :: [a] -> ([a],[a])
-splitInHalf list = (left, right)
- where
- half = length list `div` 2
- left = take half list
- right = drop half list
+ appVars = map wrapArg_P vars
+ prod a b = prodDataCon_RDR `nlConPat` [a,b]
+
+wrapArg_P :: RdrName -> LPat RdrName
+wrapArg_P v = mkM1_P (k1DataCon_RDR `nlConVarPat` [v])
+ -- This M1 is meta-information for the selector
mkGenericLocal :: US -> RdrName
mkGenericLocal u = mkVarUnqual (mkFastString ("g" ++ show u))
-mkGenericNames :: TyCon -> (RdrName, RdrName)
-mkGenericNames tycon
- = (from_RDR, to_RDR)
- where
- tc_name = tyConName tycon
- tc_occ = nameOccName tc_name
- tc_mod = ASSERT( isExternalName tc_name ) nameModule tc_name
- from_RDR = mkOrig tc_mod (mkGenOcc1 tc_occ)
- to_RDR = mkOrig tc_mod (mkGenOcc2 tc_occ)
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Generating the RHS of a generic default method}
-%* *
-%************************************************************************
-
-Generating the Generic default method. Uses the bimaps to generate the
-actual method. All of this is rather incomplete, but it would be nice
-to make even this work. Example
-
- class Foo a where
- op :: Op a
-
- instance Foo T
-
-Then we fill in the RHS for op, RenamedHsExpr, by calling mkGenericRhs:
-
- instance Foo T where
- op = <mkGenericRhs op a T>
-
-To do this, we generate a pair of RenamedHsExprs (EP toOp fromOp), where
-
- toOp :: Op Trep -> Op T
- fromOp :: Op T -> Op Trep
-
-(the bimap) and then fill in the RHS with
-
- instance Foo T where
- op = toOp op
-
-Remember, we're generating a RenamedHsExpr, so the result of all this
-will be fed to the type checker. So the 'op' on the RHS will be
-at the representation type for T, Trep.
+mkM1_E :: LHsExpr RdrName -> LHsExpr RdrName
+mkM1_E e = nlHsVar m1DataCon_RDR `nlHsApp` e
+mkM1_P :: LPat RdrName -> LPat RdrName
+mkM1_P p = m1DataCon_RDR `nlConPat` [p]
-Note [Polymorphic methods]
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-Suppose the class op is polymorphic:
+-- | Variant of foldr1 for producing balanced lists
+foldBal :: (a -> a -> a) -> [a] -> a
+foldBal op = foldBal' op (error "foldBal: empty list")
- class Baz a where
- op :: forall b. Ord b => a -> b -> b
+foldBal' :: (a -> a -> a) -> a -> [a] -> a
+foldBal' _ x [] = x
+foldBal' _ _ [y] = y
+foldBal' op x l = let (a,b) = splitAt (length l `div` 2) l
+ in foldBal' op x a `op` foldBal' op x b
-Then we can still generate a bimap with
-
- toOP :: forall b. (Trep -> b -> b) -> (T -> b -> b)
-
-and fill in the instance decl thus
-
- instance Foo T where
- op = toOp op
-
-By the time the type checker has done its stuff we'll get
-
- instance Foo T where
- op = \b. \dict::Ord b. toOp b (op Trep b dict)
-
-Note [Higher rank methods]
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-Higher-rank method types don't work, because we'd generate a bimap that
-needs impredicative polymorphism. In principle that should be possible
-(with boxy types and all) but it would take a bit of working out. Here's
-an example:
- class ChurchEncode k where
- match :: k -> z
- -> (forall a b z. a -> b -> z) {- product -}
- -> (forall a z. a -> z) {- left -}
- -> (forall a z. a -> z) {- right -}
- -> z
-
- match {| Unit |} Unit unit prod left right = unit
- match {| a :*: b |} (x :*: y) unit prod left right = prod x y
- match {| a :+: b |} (Inl l) unit prod left right = left l
- match {| a :+: b |} (Inr r) unit prod left right = right r
-
-\begin{code}
-mkGenericRhs :: Id -> TyVar -> TyCon -> LHsExpr RdrName
-mkGenericRhs sel_id tyvar tycon
- = ASSERT( isSingleton ctxt ) -- Checks shape of selector-id context
--- pprTrace "mkGenericRhs" (vcat [ppr sel_id, ppr (idType sel_id), ppr tyvar, ppr tycon, ppr local_tvs, ppr final_ty]) $
- mkHsApp (toEP bimap) (nlHsVar (getRdrName sel_id))
- where
- -- Initialising the "Environment" with the from/to functions
- -- on the datatype (actually tycon) in question
- (from_RDR, to_RDR) = mkGenericNames tycon
-
- -- Instantiate the selector type, and strip off its class context
- (ctxt, op_ty) = tcSplitPhiTy (applyTy (idType sel_id) (mkTyVarTy tyvar))
-
- -- Do it again! This deals with the case where the method type
- -- is polymorphic -- see Note [Polymorphic methods] above
- (local_tvs,_,final_ty) = tcSplitSigmaTy op_ty
-
- -- Now we probably have a tycon in front
- -- of us, quite probably a FunTyCon.
- ep = EP (nlHsVar from_RDR) (nlHsVar to_RDR)
- bimap = generate_bimap (tyvar, ep, local_tvs) final_ty
-
-type EPEnv = (TyVar, -- The class type variable
- EP (LHsExpr RdrName), -- The EP it maps to
- [TyVar] -- Other in-scope tyvars; they have an identity EP
- )
-
--------------------
-generate_bimap :: EPEnv
- -> Type
- -> EP (LHsExpr RdrName)
--- Top level case - splitting the TyCon.
-generate_bimap env@(tv,ep,local_tvs) ty
- | all (`elem` local_tvs) (varSetElems (tyVarsOfType ty))
- = idEP -- A constant type
-
- | Just tv1 <- getTyVar_maybe ty
- = ASSERT( tv == tv1 ) ep -- The class tyvar
-
- | Just (tycon, ty_args) <- tcSplitTyConApp_maybe ty
- = bimapTyCon tycon (map (generate_bimap env) ty_args)
-
- | otherwise
- = pprPanic "generate_bimap" (ppr ty)
-
--------------------
-bimapTyCon :: TyCon -> [EP (LHsExpr RdrName)] -> EP (LHsExpr RdrName)
-bimapTyCon tycon arg_eps
- | tycon == funTyCon = bimapArrow arg_eps
- | tycon == listTyCon = bimapList arg_eps
- | isBoxedTupleTyCon tycon = bimapTuple arg_eps
- | otherwise = pprPanic "bimapTyCon" (ppr tycon)
-
--------------------
--- bimapArrow :: [EP a a', EP b b'] -> EP (a->b) (a'->b')
-bimapArrow :: [EP (LHsExpr RdrName)] -> EP (LHsExpr RdrName)
-bimapArrow [ep1, ep2]
- = EP { fromEP = mkHsLam [nlVarPat a_RDR, nlVarPat b_RDR] from_body,
- toEP = mkHsLam [nlVarPat a_RDR, nlVarPat b_RDR] to_body }
- where
- from_body = fromEP ep2 `mkHsApp` (mkHsPar $ nlHsVar a_RDR `mkHsApp` (mkHsPar $ toEP ep1 `mkHsApp` nlHsVar b_RDR))
- to_body = toEP ep2 `mkHsApp` (mkHsPar $ nlHsVar a_RDR `mkHsApp` (mkHsPar $ fromEP ep1 `mkHsApp` nlHsVar b_RDR))
-
--------------------
--- bimapTuple :: [EP a1 b1, ... EP an bn] -> EP (a1,...an) (b1,..bn)
-bimapTuple :: [EP (LHsExpr RdrName)] -> EP (LHsExpr RdrName)
-bimapTuple eps
- = EP { fromEP = mkHsLam [noLoc tuple_pat] from_body,
- toEP = mkHsLam [noLoc tuple_pat] to_body }
- where
- names = takeList eps gs_RDR
- tuple_pat = TuplePat (map nlVarPat names) Boxed placeHolderType
- eps_w_names = eps `zip` names
- to_body = mkLHsTupleExpr [toEP ep `mkHsApp` nlHsVar g | (ep,g) <- eps_w_names]
- from_body = mkLHsTupleExpr [fromEP ep `mkHsApp` nlHsVar g | (ep,g) <- eps_w_names]
-
--------------------
--- bimapList :: EP a b -> EP [a] [b]
-bimapList :: [EP (LHsExpr RdrName)] -> EP (LHsExpr RdrName)
-bimapList [ep]
- = EP { fromEP = nlHsApp (nlHsVar map_RDR) (fromEP ep),
- toEP = nlHsApp (nlHsVar map_RDR) (toEP ep) }
-
--------------------
-a_RDR, b_RDR :: RdrName
-a_RDR = mkVarUnqual (fsLit "a")
-b_RDR = mkVarUnqual (fsLit "b")
-
-gs_RDR :: [RdrName]
-gs_RDR = [ mkVarUnqual (mkFastString ("g"++show i)) | i <- [(1::Int) .. ] ]
-
-idEP :: EP (LHsExpr RdrName)
-idEP = EP idexpr idexpr
- where
- idexpr = mkHsLam [nlVarPat a_RDR] (nlHsVar a_RDR)
\end{code}
projects / ghc-hetmet.git / blobdiff