singletons-2.3: src/Data/Singletons/Promote.hs
{- Data/Singletons/Promote.hs
(c) Richard Eisenberg 2013
rae@cs.brynmawr.edu
This file contains functions to promote term-level constructs to the
type level. It is an internal module to the singletons package.
-}
{-# LANGUAGE TemplateHaskell, MultiWayIf, LambdaCase, TupleSections #-}
module Data.Singletons.Promote where
import Language.Haskell.TH hiding ( Q, cxt )
import Language.Haskell.TH.Syntax ( Quasi(..) )
import Language.Haskell.TH.Desugar
import Data.Singletons.Names
import Data.Singletons.Promote.Monad
import Data.Singletons.Promote.Eq
import Data.Singletons.Promote.Defun
import Data.Singletons.Promote.Type
import Data.Singletons.Deriving.Ord
import Data.Singletons.Deriving.Bounded
import Data.Singletons.Deriving.Enum
import Data.Singletons.Partition
import Data.Singletons.Util
import Data.Singletons.Syntax
import Prelude hiding (exp)
import Control.Monad
import qualified Data.Map.Strict as Map
import Data.Map.Strict ( Map )
import Data.Maybe
-- | Generate promoted definitions from a type that is already defined.
-- This is generally only useful with classes.
genPromotions :: DsMonad q => [Name] -> q [Dec]
genPromotions names = do
checkForRep names
infos <- mapM reifyWithWarning names
dinfos <- mapM dsInfo infos
ddecs <- promoteM_ [] $ mapM_ promoteInfo dinfos
return $ decsToTH ddecs
-- | Promote every declaration given to the type level, retaining the originals.
promote :: DsMonad q => q [Dec] -> q [Dec]
promote qdec = do
decls <- qdec
ddecls <- withLocalDeclarations decls $ dsDecs decls
promDecls <- promoteM_ decls $ promoteDecs ddecls
return $ decls ++ decsToTH promDecls
-- | Promote each declaration, discarding the originals. Note that a promoted
-- datatype uses the same definition as an original datatype, so this will
-- not work with datatypes. Classes, instances, and functions are all fine.
promoteOnly :: DsMonad q => q [Dec] -> q [Dec]
promoteOnly qdec = do
decls <- qdec
ddecls <- dsDecs decls
promDecls <- promoteM_ decls $ promoteDecs ddecls
return $ decsToTH promDecls
-- | Generate defunctionalization symbols for existing type family
genDefunSymbols :: DsMonad q => [Name] -> q [Dec]
genDefunSymbols names = do
checkForRep names
infos <- mapM (dsInfo <=< reifyWithWarning) names
decs <- promoteMDecs [] $ concatMapM defunInfo infos
return $ decsToTH decs
-- | Produce instances for '(:==)' (type-level equality) from the given types
promoteEqInstances :: DsMonad q => [Name] -> q [Dec]
promoteEqInstances = concatMapM promoteEqInstance
-- | Produce instances for 'POrd' from the given types
promoteOrdInstances :: DsMonad q => [Name] -> q [Dec]
promoteOrdInstances = concatMapM promoteOrdInstance
-- | Produce an instance for 'POrd' from the given type
promoteOrdInstance :: DsMonad q => Name -> q [Dec]
promoteOrdInstance = promoteInstance mkOrdInstance "Ord"
-- | Produce instances for 'PBounded' from the given types
promoteBoundedInstances :: DsMonad q => [Name] -> q [Dec]
promoteBoundedInstances = concatMapM promoteBoundedInstance
-- | Produce an instance for 'PBounded' from the given type
promoteBoundedInstance :: DsMonad q => Name -> q [Dec]
promoteBoundedInstance = promoteInstance mkBoundedInstance "Bounded"
-- | Produce instances for 'PEnum' from the given types
promoteEnumInstances :: DsMonad q => [Name] -> q [Dec]
promoteEnumInstances = concatMapM promoteEnumInstance
-- | Produce an instance for 'PEnum' from the given type
promoteEnumInstance :: DsMonad q => Name -> q [Dec]
promoteEnumInstance = promoteInstance mkEnumInstance "Enum"
-- | Produce an instance for '(:==)' (type-level equality) from the given type
promoteEqInstance :: DsMonad q => Name -> q [Dec]
promoteEqInstance name = do
(_tvbs, cons) <- getDataD "I cannot make an instance of (:==) for it." name
cons' <- concatMapM dsCon cons
vars <- replicateM (length _tvbs) (qNewName "k")
kind <- promoteType (foldType (DConT name) (map DVarT vars))
inst_decs <- mkEqTypeInstance kind cons'
return $ decsToTH inst_decs
promoteInstance :: DsMonad q => (DType -> [DCon] -> q UInstDecl)
-> String -> Name -> q [Dec]
promoteInstance mk_inst class_name name = do
(tvbs, cons) <- getDataD ("I cannot make an instance of " ++ class_name
++ " for it.") name
cons' <- concatMapM dsCon cons
tvbs' <- mapM dsTvb tvbs
raw_inst <- mk_inst (foldType (DConT name) (map tvbToType tvbs')) cons'
decs <- promoteM_ [] $ void $ promoteInstanceDec Map.empty raw_inst
return $ decsToTH decs
promoteInfo :: DInfo -> PrM ()
promoteInfo (DTyConI dec _instances) = promoteDecs [dec]
promoteInfo (DPrimTyConI _name _numArgs _unlifted) =
fail "Promotion of primitive type constructors not supported"
promoteInfo (DVarI _name _ty _mdec) =
fail "Promotion of individual values not supported"
promoteInfo (DTyVarI _name _ty) =
fail "Promotion of individual type variables not supported"
promoteInfo (DPatSynI {}) =
fail "Promotion of pattern synonyms not supported"
-- Note [Promoting declarations in two stages]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
--
-- It is necessary to know the types of things when promoting. So,
-- we promote in two stages: first, we build a LetDecEnv, which allows
-- for easy lookup. Then, we go through the actual elements of the LetDecEnv,
-- performing the promotion.
--
-- Why do we need the types? For kind annotations on the type family. We also
-- need to have both the types and the actual function definition at the same
-- time, because the function definition tells us how many patterns are
-- matched. Note that an eta-contracted function needs to return a TyFun,
-- not a proper type-level function.
--
-- Consider this example:
--
-- foo :: Nat -> Bool -> Bool
-- foo Zero = id
-- foo _ = not
--
-- Here the first parameter to foo is non-uniform, because it is
-- inspected in a pattern and can be different in each defining
-- equation of foo. The second parameter to foo, specified in the type
-- signature as Bool, is a uniform parameter - it is not inspected and
-- each defining equation of foo uses it the same way. The foo
-- function will be promoted to a type familty Foo like this:
--
-- type family Foo (n :: Nat) :: TyFun Bool Bool -> * where
-- Foo Zero = Id
-- Foo a = Not
--
-- To generate type signature for Foo type family we must first learn
-- what is the actual number of patterns used in defining cequations
-- of foo. In this case there is only one so we declare Foo to take
-- one argument and have return type of Bool -> Bool.
-- Promote a list of top-level declarations.
promoteDecs :: [DDec] -> PrM ()
promoteDecs raw_decls = do
decls <- expand raw_decls -- expand type synonyms
checkForRepInDecls decls
PDecs { pd_let_decs = let_decs
, pd_class_decs = classes
, pd_instance_decs = insts
, pd_data_decs = datas } <- partitionDecs decls
-- promoteLetDecs returns LetBinds, which we don't need at top level
_ <- promoteLetDecs noPrefix let_decs
mapM_ promoteClassDec classes
let all_meth_sigs = foldMap (lde_types . cd_lde) classes
mapM_ (promoteInstanceDec all_meth_sigs) insts
promoteDataDecs datas
promoteDataDecs :: [DataDecl] -> PrM ()
promoteDataDecs data_decs = do
rec_selectors <- concatMapM extract_rec_selectors data_decs
_ <- promoteLetDecs noPrefix rec_selectors
mapM_ promoteDataDec data_decs
where
extract_rec_selectors :: DataDecl -> PrM [DLetDec]
extract_rec_selectors (DataDecl _nd data_name tvbs cons _derivings) =
let arg_ty = foldType (DConT data_name)
(map tvbToType tvbs)
in
getRecordSelectors arg_ty cons
-- curious about ALetDecEnv? See the LetDecEnv module for an explanation.
promoteLetDecs :: (String, String) -- (alpha, symb) prefixes to use
-> [DLetDec] -> PrM ([LetBind], ALetDecEnv)
-- See Note [Promoting declarations in two stages]
promoteLetDecs prefixes decls = do
let_dec_env <- buildLetDecEnv decls
all_locals <- allLocals
let binds = [ (name, foldType (DConT sym) (map DVarT all_locals))
| name <- Map.keys $ lde_defns let_dec_env
, let proName = promoteValNameLhsPrefix prefixes name
sym = promoteTySym proName (length all_locals) ]
(decs, let_dec_env') <- letBind binds $ promoteLetDecEnv prefixes let_dec_env
emitDecs decs
return (binds, let_dec_env' { lde_proms = Map.fromList binds })
-- Promotion of data types to kinds is automatic (see "Ginving Haskell a
-- Promotion" paper for more details). Here we "plug into" the promotion
-- mechanism to add some extra stuff to the promotion:
--
-- * if data type derives Eq we generate a type family that implements the
-- equality test for the data type.
--
-- * for each data constructor with arity greater than 0 we generate type level
-- symbols for use with Apply type family. In this way promoted data
-- constructors and promoted functions can be used in a uniform way at the
-- type level in the same way they can be used uniformly at the type level.
--
-- * for each nullary data constructor we generate a type synonym
promoteDataDec :: DataDecl -> PrM ()
promoteDataDec (DataDecl _nd name tvbs ctors derivings) = do
-- deriving Eq instance
kvs <- replicateM (length tvbs) (qNewName "k")
kind <- promoteType (foldType (DConT name) (map DVarT kvs))
when (any (\case DConPr n -> n == eqName
_ -> False) derivings) $ do
eq_decs <- mkEqTypeInstance kind ctors
emitDecs eq_decs
ctorSyms <- buildDefunSymsDataD name tvbs ctors
emitDecs ctorSyms
-- Note [CUSKification]
-- ~~~~~~~~~~~~~~~~~~~~
-- GHC #12928 means that sometimes, this TH code will produce a declaration
-- that has a kind signature even when we want kind inference to work. There
-- seems to be no way to avoid this, so we embrace it:
--
-- * If a class type variable has no explicit kind, we make no effort to
-- guess it and default to *. This is OK because before TypeInType we were
-- limited by KProxy anyway.
--
-- * If a class type variable has an explicit kind, it is preserved.
--
-- This way, we always get proper CUSKs where we need them.
promoteClassDec :: UClassDecl
-> PrM AClassDecl
promoteClassDec decl@(ClassDecl { cd_cxt = cxt
, cd_name = cls_name
, cd_tvbs = tvbs'
, cd_fds = fundeps
, cd_lde = lde@LetDecEnv
{ lde_defns = defaults
, lde_types = meth_sigs
, lde_infix = infix_decls } }) = do
let
-- a workaround for GHC Trac #12928; see Note [CUSKification]
cuskify :: DTyVarBndr -> DTyVarBndr
cuskify (DPlainTV tvname) = DKindedTV tvname DStarT
cuskify tv = tv
tvbs = map cuskify tvbs'
let pClsName = promoteClassName cls_name
pCxt <- mapM promote_superclass_pred cxt
sig_decs <- mapM (uncurry promote_sig) (Map.toList meth_sigs)
let defaults_list = Map.toList defaults
defaults_names = map fst defaults_list
(default_decs, ann_rhss, prom_rhss)
<- mapAndUnzip3M (promoteMethod Nothing meth_sigs) defaults_list
let infix_decls' = catMaybes $ map (uncurry promoteInfixDecl) infix_decls
-- no need to do anything to the fundeps. They work as is!
emitDecs [DClassD pCxt pClsName tvbs fundeps
(sig_decs ++ default_decs ++ infix_decls')]
let defaults_list' = zip defaults_names ann_rhss
proms = zip defaults_names prom_rhss
return (decl { cd_lde = lde { lde_defns = Map.fromList defaults_list'
, lde_proms = Map.fromList proms } })
where
promote_sig :: Name -> DType -> PrM DDec
promote_sig name ty = do
let proName = promoteValNameLhs name
(argKs, resK) <- promoteUnraveled ty
args <- mapM (const $ qNewName "arg") argKs
emitDecsM $ defunctionalize proName (map Just argKs) (Just resK)
return $ DOpenTypeFamilyD (DTypeFamilyHead proName
(zipWith DKindedTV args argKs)
(DKindSig resK)
Nothing)
promote_superclass_pred :: DPred -> PrM DPred
promote_superclass_pred = go
where
go (DAppPr pr ty) = DAppPr <$> go pr <*> promoteType ty
go (DSigPr pr _k) = go pr -- just ignore the kind; it can't matter
go (DVarPr name) = fail $ "Cannot promote ConstraintKinds variables like "
++ show name
go (DConPr name) = return $ DConPr (promoteClassName name)
go DWildCardPr = return DWildCardPr
-- returns (unpromoted method name, ALetDecRHS) pairs
promoteInstanceDec :: Map Name DType -> UInstDecl -> PrM AInstDecl
promoteInstanceDec meth_sigs
decl@(InstDecl { id_name = cls_name
, id_arg_tys = inst_tys
, id_meths = meths }) = do
cls_tvb_names <- lookup_cls_tvb_names
inst_kis <- mapM promoteType inst_tys
let subst = Map.fromList $ zip cls_tvb_names inst_kis
(meths', ann_rhss, _) <- mapAndUnzip3M (promoteMethod (Just subst) meth_sigs) meths
emitDecs [DInstanceD Nothing [] (foldType (DConT pClsName)
inst_kis) meths']
return (decl { id_meths = zip (map fst meths) ann_rhss })
where
pClsName = promoteClassName cls_name
lookup_cls_tvb_names :: PrM [Name]
lookup_cls_tvb_names = do
mb_info <- dsReify pClsName
case mb_info of
Just (DTyConI (DClassD _ _ tvbs _ _) _) -> return (map extractTvbName tvbs)
_ -> do
mb_info' <- dsReify cls_name
case mb_info' of
Just (DTyConI (DClassD _ _ tvbs _ _) _) -> return (map extractTvbName tvbs)
_ -> fail $ "Cannot find class declaration annotation for " ++ show cls_name
-- promoteMethod needs to substitute in a method's kind because GHC does not do
-- enough kind checking of associated types. See GHC#9063. When that bug is fixed,
-- the substitution code can be removed.
-- Bug is fixed, but only in HEAD, naturally. When we stop supporting 7.8,
-- this can be rewritten more cleanly, I imagine.
-- UPDATE: GHC 7.10.2 didn't fully solve GHC#9063. Urgh.
promoteMethod :: Maybe (Map Name DKind)
-- ^ instantiations for class tyvars (Nothing for default decls)
-> Map Name DType -- method types
-> (Name, ULetDecRHS)
-> PrM (DDec, ALetDecRHS, DType)
-- returns (type instance, ALetDecRHS, promoted RHS)
promoteMethod m_subst sigs_map (meth_name, meth_rhs) = do
(arg_kis, res_ki) <- lookup_meth_ty
((_, _, _, eqns), _defuns, ann_rhs)
<- promoteLetDecRHS (Just (arg_kis, res_ki)) sigs_map noPrefix meth_name meth_rhs
meth_arg_tvs <- mapM (const $ qNewName "a") arg_kis
let do_subst = maybe id substKind m_subst
meth_arg_kis' = map do_subst arg_kis
meth_res_ki' = do_subst res_ki
helperNameBase = case nameBase proName of
first:_ | not (isHsLetter first) -> "TFHelper"
alpha -> alpha
family_args
-- GHC 8 requires bare tyvars to the left of a type family default
| Nothing <- m_subst
= map DVarT meth_arg_tvs
| otherwise
= zipWith (DSigT . DVarT) meth_arg_tvs meth_arg_kis'
helperName <- newUniqueName helperNameBase
emitDecs [DClosedTypeFamilyD (DTypeFamilyHead
helperName
(zipWith DKindedTV meth_arg_tvs meth_arg_kis')
(DKindSig meth_res_ki')
Nothing)
eqns]
emitDecsM (defunctionalize helperName (map Just meth_arg_kis') (Just meth_res_ki'))
return ( DTySynInstD
proName
(DTySynEqn family_args
(foldApply (promoteValRhs helperName) (map DVarT meth_arg_tvs)))
, ann_rhs
, DConT (promoteTySym helperName 0) )
where
proName = promoteValNameLhs meth_name
lookup_meth_ty :: PrM ([DKind], DKind)
lookup_meth_ty = case Map.lookup meth_name sigs_map of
Nothing -> do
mb_info <- dsReify proName
case mb_info of
Just (DTyConI (DOpenTypeFamilyD (DTypeFamilyHead _ tvbs mb_res_ki _)) _)
-> let arg_kis = map (default_to_star . extractTvbKind) tvbs
res_ki = default_to_star (resultSigToMaybeKind mb_res_ki)
in return (arg_kis, res_ki)
_ -> fail $ "Cannot find type annotation for " ++ show proName
Just ty -> promoteUnraveled ty
default_to_star Nothing = DStarT
default_to_star (Just k) = k
promoteLetDecEnv :: (String, String) -> ULetDecEnv -> PrM ([DDec], ALetDecEnv)
promoteLetDecEnv prefixes (LetDecEnv { lde_defns = value_env
, lde_types = type_env
, lde_infix = infix_decls }) = do
let infix_decls' = catMaybes $ map (uncurry promoteInfixDecl) infix_decls
-- promote all the declarations, producing annotated declarations
let (names, rhss) = unzip $ Map.toList value_env
(payloads, defun_decss, ann_rhss)
<- fmap unzip3 $ zipWithM (promoteLetDecRHS Nothing type_env prefixes) names rhss
emitDecs $ concat defun_decss
let decs = map payload_to_dec payloads ++ infix_decls'
-- build the ALetDecEnv
let let_dec_env' = LetDecEnv { lde_defns = Map.fromList $ zip names ann_rhss
, lde_types = type_env
, lde_infix = infix_decls
, lde_proms = Map.empty } -- filled in promoteLetDecs
return (decs, let_dec_env')
where
payload_to_dec (name, tvbs, m_ki, eqns) = DClosedTypeFamilyD
(DTypeFamilyHead name tvbs sig Nothing)
eqns
where
sig = maybe DNoSig DKindSig m_ki
promoteInfixDecl :: Fixity -> Name -> Maybe DDec
promoteInfixDecl fixity name
| isUpcase name = Nothing -- no need to promote the decl
| otherwise = Just $ DLetDec $ DInfixD fixity (promoteValNameLhs name)
-- This function is used both to promote class method defaults and normal
-- let bindings. Thus, it can't quite do all the work locally and returns
-- an intermediate structure. Perhaps a better design is available.
promoteLetDecRHS :: Maybe ([DKind], DKind) -- the promoted type of the RHS (if known)
-- needed to fix #136
-> Map Name DType -- local type env't
-> (String, String) -- let-binding prefixes
-> Name -- name of the thing being promoted
-> ULetDecRHS -- body of the thing
-> PrM ( (Name, [DTyVarBndr], Maybe DKind, [DTySynEqn]) -- "type family"
, [DDec] -- defunctionalization
, ALetDecRHS ) -- annotated RHS
promoteLetDecRHS m_rhs_ki type_env prefixes name (UValue exp) = do
(res_kind, num_arrows)
<- case m_rhs_ki of
Just (arg_kis, res_ki) -> return ( Just (ravelTyFun (arg_kis ++ [res_ki]))
, length arg_kis )
_ | Just ty <- Map.lookup name type_env
-> do ki <- promoteType ty
return (Just ki, countArgs ty)
| otherwise
-> return (Nothing, 0)
case num_arrows of
0 -> do
all_locals <- allLocals
(exp', ann_exp) <- promoteExp exp
let proName = promoteValNameLhsPrefix prefixes name
defuns <- defunctionalize proName (map (const Nothing) all_locals) res_kind
return ( ( proName, map DPlainTV all_locals, res_kind
, [DTySynEqn (map DVarT all_locals) exp'] )
, defuns
, AValue (foldType (DConT proName) (map DVarT all_locals))
num_arrows ann_exp )
_ -> do
names <- replicateM num_arrows (newUniqueName "a")
let pats = map DVarPa names
newArgs = map DVarE names
promoteLetDecRHS m_rhs_ki type_env prefixes name
(UFunction [DClause pats (foldExp exp newArgs)])
promoteLetDecRHS m_rhs_ki type_env prefixes name (UFunction clauses) = do
numArgs <- count_args clauses
(m_argKs, m_resK, ty_num_args) <- case m_rhs_ki of
Just (arg_kis, res_ki) -> return (map Just arg_kis, Just res_ki, length arg_kis)
_ | Just ty <- Map.lookup name type_env
-> do
-- promoteType turns arrows into TyFun. So, we unravel first to
-- avoid this behavior. Note the use of ravelTyFun in resultK
-- to make the return kind work out
(argKs, resultK) <- promoteUnraveled ty
-- invariant: countArgs ty == length argKs
return (map Just argKs, Just resultK, length argKs)
| otherwise
-> return (replicate numArgs Nothing, Nothing, numArgs)
let proName = promoteValNameLhsPrefix prefixes name
all_locals <- allLocals
defun_decs <- defunctionalize proName
(map (const Nothing) all_locals ++ m_argKs) m_resK
let local_tvbs = map DPlainTV all_locals
tyvarNames <- mapM (const $ qNewName "a") m_argKs
expClauses <- mapM (etaExpand (ty_num_args - numArgs)) clauses
(eqns, ann_clauses) <- mapAndUnzipM promoteClause expClauses
prom_fun <- lookupVarE name
let args = zipWith inferMaybeKindTV tyvarNames m_argKs
all_args = local_tvbs ++ args
return ( (proName, all_args, m_resK, eqns)
, defun_decs
, AFunction prom_fun ty_num_args ann_clauses )
where
etaExpand :: Int -> DClause -> PrM DClause
etaExpand n (DClause pats exp) = do
names <- replicateM n (newUniqueName "a")
let newPats = map DVarPa names
newArgs = map DVarE names
return $ DClause (pats ++ newPats) (foldExp exp newArgs)
count_args (DClause pats _ : _) = return $ length pats
count_args _ = fail $ "Impossible! A function without clauses."
promoteClause :: DClause -> PrM (DTySynEqn, ADClause)
promoteClause (DClause pats exp) = do
-- promoting the patterns creates variable bindings. These are passed
-- to the function promoted the RHS
(types, new_vars) <- evalForPair $ mapM promotePat pats
(ty, ann_exp) <- lambdaBind new_vars $ promoteExp exp
all_locals <- allLocals -- these are bound *outside* of this clause
return ( DTySynEqn (map DVarT all_locals ++ types) ty
, ADClause new_vars pats ann_exp )
promoteMatch :: DMatch -> PrM (DTySynEqn, ADMatch)
promoteMatch (DMatch pat exp) = do
-- promoting the patterns creates variable bindings. These are passed
-- to the function promoted the RHS
(ty, new_vars) <- evalForPair $ promotePat pat
(rhs, ann_exp) <- lambdaBind new_vars $ promoteExp exp
all_locals <- allLocals
return $ ( DTySynEqn (map DVarT all_locals ++ [ty]) rhs
, ADMatch new_vars pat ann_exp)
-- promotes a term pattern into a type pattern, accumulating bound variable names
promotePat :: DPat -> QWithAux VarPromotions PrM DType
promotePat (DLitPa lit) = do
lit' <- promoteLitPat lit
return lit'
promotePat (DVarPa name) = do
-- term vars can be symbols... type vars can't!
tyName <- mkTyName name
addElement (name, tyName)
return $ DVarT tyName
promotePat (DConPa name pats) = do
types <- mapM promotePat pats
let name' = unboxed_tuple_to_tuple name
return $ foldType (DConT name') types
where
unboxed_tuple_to_tuple n
| Just deg <- unboxedTupleNameDegree_maybe n = tupleDataName deg
| otherwise = n
promotePat (DTildePa pat) = do
qReportWarning "Lazy pattern converted into regular pattern in promotion"
promotePat pat
promotePat (DBangPa pat) = do
qReportWarning "Strict pattern converted into regular pattern in promotion"
promotePat pat
promotePat (DSigPa pat ty) = do
promoted <- promotePat pat
ki <- promoteType ty
return $ DSigT promoted ki
promotePat DWildPa = do
name <- newUniqueName "_z"
tyName <- mkTyName name
return $ DVarT tyName
promoteExp :: DExp -> PrM (DType, ADExp)
promoteExp (DVarE name) = fmap (, ADVarE name) $ lookupVarE name
promoteExp (DConE name) = return $ (promoteValRhs name, ADConE name)
promoteExp (DLitE lit) = fmap (, ADLitE lit) $ promoteLitExp lit
promoteExp (DAppE exp1 exp2) = do
(exp1', ann_exp1) <- promoteExp exp1
(exp2', ann_exp2) <- promoteExp exp2
return (apply exp1' exp2', ADAppE ann_exp1 ann_exp2)
-- Until we get visible kind applications, this is the best we can do.
promoteExp (DAppTypeE exp _) = do
qReportWarning "Visible type applications are ignored by `singletons`."
promoteExp exp
promoteExp (DLamE names exp) = do
lambdaName <- newUniqueName "Lambda"
tyNames <- mapM mkTyName names
let var_proms = zip names tyNames
(rhs, ann_exp) <- lambdaBind var_proms $ promoteExp exp
tyFamLamTypes <- mapM (const $ qNewName "t") names
all_locals <- allLocals
let all_args = all_locals ++ tyFamLamTypes
tvbs = map DPlainTV all_args
emitDecs [DClosedTypeFamilyD (DTypeFamilyHead
lambdaName
tvbs
DNoSig
Nothing)
[DTySynEqn (map DVarT (all_locals ++ tyNames))
rhs]]
emitDecsM $ defunctionalize lambdaName (map (const Nothing) all_args) Nothing
let promLambda = foldl apply (DConT (promoteTySym lambdaName 0))
(map DVarT all_locals)
return (promLambda, ADLamE tyNames promLambda names ann_exp)
promoteExp (DCaseE exp matches) = do
caseTFName <- newUniqueName "Case"
all_locals <- allLocals
let prom_case = foldType (DConT caseTFName) (map DVarT all_locals)
(exp', ann_exp) <- promoteExp exp
(eqns, ann_matches) <- mapAndUnzipM promoteMatch matches
tyvarName <- qNewName "t"
let all_args = all_locals ++ [tyvarName]
tvbs = map DPlainTV all_args
emitDecs [DClosedTypeFamilyD (DTypeFamilyHead caseTFName tvbs DNoSig Nothing) eqns]
-- See Note [Annotate case return type] in Single
let applied_case = prom_case `DAppT` exp'
return ( applied_case
, ADCaseE ann_exp ann_matches applied_case )
promoteExp (DLetE decs exp) = do
unique <- qNewUnique
let letPrefixes = uniquePrefixes "Let" ":<<<" unique
(binds, ann_env) <- promoteLetDecs letPrefixes decs
(exp', ann_exp) <- letBind binds $ promoteExp exp
return (exp', ADLetE ann_env ann_exp)
promoteExp (DSigE exp ty) = do
(exp', ann_exp) <- promoteExp exp
ty' <- promoteType ty
return (DSigT exp' ty', ADSigE ann_exp ty)
promoteExp e@(DStaticE _) = fail ("Static expressions cannot be promoted: " ++ show e)
promoteLitExp :: Monad m => Lit -> m DType
promoteLitExp (IntegerL n)
| n >= 0 = return $ (DConT tyFromIntegerName `DAppT` DLitT (NumTyLit n))
| otherwise = return $ (DConT tyNegateName `DAppT`
(DConT tyFromIntegerName `DAppT` DLitT (NumTyLit (-n))))
promoteLitExp (StringL str) = return $ DLitT (StrTyLit str)
promoteLitExp lit =
fail ("Only string and natural number literals can be promoted: " ++ show lit)
promoteLitPat :: Monad m => Lit -> m DType
promoteLitPat (IntegerL n)
| n >= 0 = return $ (DLitT (NumTyLit n))
| otherwise =
fail $ "Negative literal patterns are not allowed,\n" ++
"because literal patterns are promoted to natural numbers."
promoteLitPat (StringL str) = return $ DLitT (StrTyLit str)
promoteLitPat lit =
fail ("Only string and natural number literals can be promoted: " ++ show lit)