idris-1.1.0: src/Idris/Core/CaseTree.hs
{-|
Module : Idris.Core.CaseTree
Description : Module to define and interact with case trees.
Copyright :
License : BSD3
Maintainer : The Idris Community.
Note: The case-tree elaborator only produces (Case n alts)-cases;
in other words, it never inspects anything else than variables.
ProjCase is a special powerful case construct that allows inspection
of compound terms. Occurrences of ProjCase arise no earlier than
in the function `prune` as a means of optimisation
of already built case trees.
While the intermediate representation (follows in the pipeline, named LExp)
allows casing on arbitrary terms, here we choose to maintain the distinction
in order to allow for better optimisation opportunities.
-}
{-# LANGUAGE DeriveFunctor, DeriveGeneric, FlexibleContexts, FlexibleInstances,
PatternGuards, TypeSynonymInstances #-}
module Idris.Core.CaseTree (
CaseDef(..), SC, SC'(..), CaseAlt, CaseAlt'(..), ErasureInfo
, Phase(..), CaseTree, CaseType(..)
, simpleCase, small, namesUsed, findCalls, findCalls', findUsedArgs
, substSC, substAlt, mkForce
) where
import Idris.Core.TT
import Control.Applicative hiding (Const)
import Control.Monad.Reader
import Control.Monad.State
import Data.List hiding (partition)
import qualified Data.List (partition)
import Data.Maybe
import qualified Data.Set as S
import Debug.Trace
import GHC.Generics (Generic)
data CaseDef = CaseDef [Name] !SC [Term]
deriving Show
data SC' t = Case CaseType Name [CaseAlt' t] -- ^ invariant: lowest tags first
| ProjCase t [CaseAlt' t] -- ^ special case for projections/thunk-forcing before inspection
| STerm !t
| UnmatchedCase String -- ^ error message
| ImpossibleCase -- ^ already checked to be impossible
deriving (Eq, Ord, Functor, Generic)
{-!
deriving instance Binary SC'
!-}
data CaseType = Updatable | Shared
deriving (Eq, Ord, Show, Generic)
type SC = SC' Term
data CaseAlt' t = ConCase Name Int [Name] !(SC' t)
| FnCase Name [Name] !(SC' t) -- ^ reflection function
| ConstCase Const !(SC' t)
| SucCase Name !(SC' t)
| DefaultCase !(SC' t)
deriving (Show, Eq, Ord, Functor, Generic)
{-!
deriving instance Binary CaseAlt'
!-}
type CaseAlt = CaseAlt' Term
instance Show t => Show (SC' t) where
show sc = show' 1 sc
where
show' i (Case up n alts) = "case" ++ u ++ show n ++ " of\n" ++ indent i ++
showSep ("\n" ++ indent i) (map (showA i) alts)
where u = case up of
Updatable -> "! "
Shared -> " "
show' i (ProjCase tm alts) = "case " ++ show tm ++ " of " ++
showSep ("\n" ++ indent i) (map (showA i) alts)
show' i (STerm tm) = show tm
show' i (UnmatchedCase str) = "error " ++ show str
show' i ImpossibleCase = "impossible"
indent i = concat $ take i (repeat " ")
showA i (ConCase n t args sc)
= show n ++ "(" ++ showSep (", ") (map show args) ++ ") => "
++ show' (i+1) sc
showA i (FnCase n args sc)
= "FN " ++ show n ++ "(" ++ showSep (", ") (map show args) ++ ") => "
++ show' (i+1) sc
showA i (ConstCase t sc)
= show t ++ " => " ++ show' (i+1) sc
showA i (SucCase n sc)
= show n ++ "+1 => " ++ show' (i+1) sc
showA i (DefaultCase sc)
= "_ => " ++ show' (i+1) sc
type CaseTree = SC
type Clause = ([Pat], (Term, Term))
type CS = ([Term], Int, [(Name, Type)])
instance TermSize SC where
termsize n (Case _ n' as) = termsize n as
termsize n (ProjCase n' as) = termsize n as
termsize n (STerm t) = termsize n t
termsize n _ = 1
instance TermSize CaseAlt where
termsize n (ConCase _ _ _ s) = termsize n s
termsize n (FnCase _ _ s) = termsize n s
termsize n (ConstCase _ s) = termsize n s
termsize n (SucCase _ s) = termsize n s
termsize n (DefaultCase s) = termsize n s
-- simple terms can be inlined trivially - good for primitives in particular
-- To avoid duplicating work, don't inline something which uses one
-- of its arguments in more than one place
small :: Name -> [Name] -> SC -> Bool
small n args t = let as = findAllUsedArgs t args in
length as == length (nub as) &&
termsize n t < 10
namesUsed :: SC -> [Name]
namesUsed sc = nub $ nu' [] sc where
nu' ps (Case _ n alts) = nub (concatMap (nua ps) alts) \\ [n]
nu' ps (ProjCase t alts) = nub $ nut ps t ++ concatMap (nua ps) alts
nu' ps (STerm t) = nub $ nut ps t
nu' ps _ = []
nua ps (ConCase n i args sc) = nub (nu' (ps ++ args) sc) \\ args
nua ps (FnCase n args sc) = nub (nu' (ps ++ args) sc) \\ args
nua ps (ConstCase _ sc) = nu' ps sc
nua ps (SucCase _ sc) = nu' ps sc
nua ps (DefaultCase sc) = nu' ps sc
nut ps (P _ n _) | n `elem` ps = []
| otherwise = [n]
nut ps (App _ f a) = nut ps f ++ nut ps a
nut ps (Proj t _) = nut ps t
nut ps (Bind n (Let t v) sc) = nut ps v ++ nut (n:ps) sc
nut ps (Bind n b sc) = nut (n:ps) sc
nut ps _ = []
-- | Return all called functions, and which arguments are used
-- in each argument position for the call, in order to help reduce
-- compilation time, and trace all unused arguments
findCalls :: SC -> [Name] -> [(Name, [[Name]])]
findCalls = findCalls' False
findCalls' :: Bool -> SC -> [Name] -> [(Name, [[Name]])]
findCalls' ignoreasserts sc topargs = S.toList $ nu' topargs sc where
nu' ps (Case _ n alts) = S.unions $ map (nua (n : ps)) alts
nu' ps (ProjCase t alts) = S.unions $ nut ps t : map (nua ps) alts
nu' ps (STerm t) = nut ps t
nu' ps _ = S.empty
nua ps (ConCase n i args sc) = nu' (ps ++ args) sc
nua ps (FnCase n args sc) = nu' (ps ++ args) sc
nua ps (ConstCase _ sc) = nu' ps sc
nua ps (SucCase _ sc) = nu' ps sc
nua ps (DefaultCase sc) = nu' ps sc
nut ps (P _ n _) | n `elem` ps = S.empty
| otherwise = S.singleton (n, [])
nut ps fn@(App _ f a)
| (P _ n _, args) <- unApply fn
= if ignoreasserts && n == sUN "assert_total"
then S.empty
else if n `elem` ps
then S.union (nut ps f) (nut ps a)
else S.insert (n, map argNames args)
(S.unions $ map (nut ps) args)
| (P (TCon _ _) n _, _) <- unApply fn = S.empty
| otherwise = S.union (nut ps f) (nut ps a)
nut ps (Bind n (Let t v) sc) = S.union (nut ps v) (nut (n:ps) sc)
nut ps (Proj t _) = nut ps t
nut ps (Bind n b sc) = nut (n:ps) sc
nut ps _ = S.empty
argNames tm = let ns = directUse tm in
filter (\x -> x `elem` ns) topargs
-- Find names which are used directly (i.e. not in a function call) in a term
directUse :: TT Name -> [Name]
directUse (P _ n _) = [n]
directUse (Bind n (Let t v) sc) = nub $ directUse v ++ (directUse sc \\ [n])
++ directUse t
directUse (Bind n b sc) = nub $ directUse (binderTy b) ++ (directUse sc \\ [n])
directUse fn@(App _ f a)
| (P Ref (UN pfk) _, [App _ e w]) <- unApply fn,
pfk == txt "prim_fork"
= directUse e ++ directUse w -- HACK so that fork works
| (P Ref (UN fce) _, [_, _, a]) <- unApply fn,
fce == txt "Force"
= directUse a -- forcing a value counts as a use
| (P Ref n _, args) <- unApply fn = [] -- need to know what n does with them
| (P (TCon _ _) n _, args) <- unApply fn = [] -- type constructors not used at runtime
| otherwise = nub $ directUse f ++ directUse a
directUse (Proj x i) = nub $ directUse x
directUse _ = []
-- Find all directly used arguments (i.e. used but not in function calls)
findUsedArgs :: SC -> [Name] -> [Name]
findUsedArgs sc topargs = nub (findAllUsedArgs sc topargs)
findAllUsedArgs sc topargs = filter (\x -> x `elem` topargs) (nu' sc) where
nu' (Case _ n alts) = n : concatMap nua alts
nu' (ProjCase t alts) = directUse t ++ concatMap nua alts
nu' (STerm t) = directUse t
nu' _ = []
nua (ConCase n i args sc) = nu' sc
nua (FnCase n args sc) = nu' sc
nua (ConstCase _ sc) = nu' sc
nua (SucCase _ sc) = nu' sc
nua (DefaultCase sc) = nu' sc
-- Return whether name is used anywhere in a case tree
isUsed :: SC -> Name -> Bool
isUsed sc n = used sc where
used (Case _ n' alts) = n == n' || any usedA alts
used (ProjCase t alts) = n `elem` freeNames t || any usedA alts
used (STerm t) = n `elem` freeNames t
used _ = False
usedA (ConCase _ _ args sc) = used sc
usedA (FnCase _ args sc) = used sc
usedA (ConstCase _ sc) = used sc
usedA (SucCase _ sc) = used sc
usedA (DefaultCase sc) = used sc
type ErasureInfo = Name -> [Int] -- name to list of inaccessible arguments; empty list if name not found
type CaseBuilder a = ReaderT ErasureInfo (State CS) a
runCaseBuilder :: ErasureInfo -> CaseBuilder a -> (CS -> (a, CS))
runCaseBuilder ei bld = runState $ runReaderT bld ei
data Phase = CoverageCheck [Int] -- list of positions explicitly given
| CompileTime
| RunTime
deriving (Show, Eq)
-- Generate a simple case tree
-- Work Right to Left
simpleCase :: Bool -> SC -> Bool ->
Phase -> FC ->
-- Following two can be empty lists when Phase = CoverageCheck
[Int] -> -- Inaccessible argument positions
[(Type, Bool)] -> -- (Argument type, whether it's canonical)
[([Name], Term, Term)] ->
ErasureInfo ->
TC CaseDef
simpleCase tc defcase reflect phase fc inacc argtys cs erInfo
= sc' tc defcase phase fc (filter (\(_, _, r) ->
case r of
Impossible -> False
_ -> True) cs)
where
sc' tc defcase phase fc []
= return $ CaseDef [] (UnmatchedCase (show fc ++ ":No pattern clauses")) []
sc' tc defcase phase fc cs
= let proj = phase == RunTime
vnames = fstT (head cs)
pats = map (\ (avs, l, r) ->
(avs, toPats reflect tc l, (l, r))) cs
chkPats = mapM chkAccessible pats in
case chkPats of
OK pats ->
let numargs = length (fst (head pats))
ns = take numargs args
(ns', ps') = order phase [(n, i `elem` inacc) | (i,n) <- zip [0..] ns] pats (map snd argtys)
(tree, st) = runCaseBuilder erInfo
(match ns' ps' defcase)
([], numargs, [])
t = CaseDef ns (prune proj (depatt ns' tree)) (fstT st) in
if proj then return (stripLambdas t)
else return t
Error err -> Error (At fc err)
where args = map (\i -> sMN i "e") [0..]
defaultCase True = STerm Erased
defaultCase False = UnmatchedCase "Error"
fstT (x, _, _) = x
lstT (_, _, x) = x
-- Check that all pattern variables are reachable by a case split
-- Otherwise, they won't make sense on the RHS.
chkAccessible (avs, l, c)
| phase /= CompileTime || reflect = return (l, c)
| otherwise = do mapM_ (acc l) avs
return (l, c)
acc [] n = Error (Inaccessible n)
acc (PV x t : xs) n | x == n = OK ()
acc (PCon _ _ _ ps : xs) n = acc (ps ++ xs) n
acc (PSuc p : xs) n = acc (p : xs) n
acc (_ : xs) n = acc xs n
-- For each 'Case', make sure every choice is in the same type family,
-- as directed by the variable type (i.e. there is no implicit type casing
-- going on).
checkSameTypes :: [(Name, Type)] -> SC -> Bool
checkSameTypes tys (Case _ n alts)
= case lookup n tys of
Just t -> and (map (checkAlts t) alts)
_ -> and (map ((checkSameTypes tys).getSC) alts)
where
checkAlts t (ConCase n _ _ sc) = isType n t && checkSameTypes tys sc
checkAlts (Constant t) (ConstCase c sc) = isConstType c t && checkSameTypes tys sc
checkAlts _ (ConstCase c sc) = False
checkAlts _ _ = True
getSC (ConCase _ _ _ sc) = sc
getSC (FnCase _ _ sc) = sc
getSC (ConstCase _ sc) = sc
getSC (SucCase _ sc) = sc
getSC (DefaultCase sc) = sc
checkSameTypes _ _ = True
-- FIXME: All we're actually doing here is checking that we haven't arrived
-- at a specific constructor for a polymorphic argument. I *think* this
-- is sufficient, but if it turns out not to be, fix it!
--
-- Issue #1718 on the issue tracker: https://github.com/idris-lang/Idris-dev/issues/1718
isType n t | (P (TCon _ _) _ _, _) <- unApply t = True
isType n t | (P Ref _ _, _) <- unApply t = True
isType n t = False
isConstType (I _) (AType (ATInt ITNative)) = True
isConstType (BI _) (AType (ATInt ITBig)) = True
isConstType (Fl _) (AType ATFloat) = True
isConstType (Ch _) (AType (ATInt ITChar)) = True
isConstType (Str _) StrType = True
isConstType (B8 _) (AType (ATInt _)) = True
isConstType (B16 _) (AType (ATInt _)) = True
isConstType (B32 _) (AType (ATInt _)) = True
isConstType (B64 _) (AType (ATInt _)) = True
isConstType _ _ = False
data Pat = PCon Bool Name Int [Pat]
| PConst Const
| PInferred Pat
| PV Name Type
| PSuc Pat -- special case for n+1 on Integer
| PReflected Name [Pat]
| PAny
| PTyPat -- typecase, not allowed, inspect last
deriving Show
-- If there are repeated variables, take the *last* one (could be name shadowing
-- in a where clause, so take the most recent).
toPats :: Bool -> Bool -> Term -> [Pat]
toPats reflect tc f = reverse (toPat reflect tc (getArgs f)) where
getArgs (App _ f a) = a : getArgs f
getArgs _ = []
toPat :: Bool -> Bool -> [Term] -> [Pat]
toPat reflect tc = map $ toPat' []
where
toPat' [_,_,arg] (P (DCon t a uniq) nm@(UN n) _)
| n == txt "Delay"
= PCon uniq nm t [PAny, PAny, toPat' [] arg]
toPat' args (P (DCon t a uniq) nm@(NS (UN n) [own]) _)
| n == txt "Read" && own == txt "Ownership"
= PCon False nm t (map shareCons (map (toPat' []) args))
where shareCons (PCon _ n i ps) = PCon False n i (map shareCons ps)
shareCons p = p
toPat' args (P (DCon t a uniq) n _)
= PCon uniq n t $ map (toPat' []) args
-- n + 1
toPat' [p, Constant (BI 1)] (P _ (UN pabi) _)
| pabi == txt "prim__addBigInt"
= PSuc $ toPat' [] p
toPat' [] (P Bound n ty) = PV n ty
toPat' args (App _ f a) = toPat' (a : args) f
toPat' args (Inferred tm) = PInferred (toPat' args tm)
toPat' [] (Constant x) | isTypeConst x = PTyPat
| otherwise = PConst x
toPat' [] (Bind n (Pi _ _ t _) sc)
| reflect && noOccurrence n sc
= PReflected (sUN "->") [toPat' [] t, toPat' [] sc]
toPat' args (P _ n _)
| reflect
= PReflected n $ map (toPat' []) args
toPat' _ t = PAny
fixedN IT8 = "Bits8"
fixedN IT16 = "Bits16"
fixedN IT32 = "Bits32"
fixedN IT64 = "Bits64"
data Partition = Cons [Clause]
| Vars [Clause]
deriving Show
isVarPat (PV _ _ : ps , _) = True
isVarPat (PAny : ps , _) = True
isVarPat (PTyPat : ps , _) = True
isVarPat _ = False
isConPat (PCon _ _ _ _ : ps, _) = True
isConPat (PReflected _ _ : ps, _) = True
isConPat (PSuc _ : ps, _) = True
isConPat (PConst _ : ps, _) = True
isConPat _ = False
partition :: [Clause] -> [Partition]
partition [] = []
partition ms@(m : _)
| isVarPat m = let (vars, rest) = span isVarPat ms in
Vars vars : partition rest
| isConPat m = let (cons, rest) = span isConPat ms in
Cons cons : partition rest
partition xs = error $ "Partition " ++ show xs
-- reorder the patterns so that the one with most distinct names
-- comes next. Take rightmost first, otherwise (i.e. pick value rather
-- than dependency)
--
-- The first argument means [(Name, IsInaccessible)].
order :: Phase -> [(Name, Bool)] -> [Clause] -> [Bool] -> ([Name], [Clause])
-- do nothing at compile time: FIXME (EB): Put this in after checking
-- implications for Franck's reflection work... see issue 3233
-- order CompileTime ns cs _ = (map fst ns, cs)
order _ [] cs cans = ([], cs)
order _ ns' [] cans = (map fst ns', [])
order (CoverageCheck pos) ns' cs cans
= let ns_out = pick 0 [] (map fst ns')
cs_out = map pickClause cs in
(ns_out, cs_out)
where
pickClause (pats, def) = (pick 0 [] pats, def)
-- Order the list so that things in a position in 'pos' are in the first
-- part, then all the other things later. Otherwise preserve order.
pick i skipped [] = reverse skipped
pick i skipped (x : xs)
| i `elem` pos = x : pick (i + 1) skipped xs
| otherwise = pick (i + 1) (x : skipped) xs
order phase ns' cs cans
= let patnames = transpose (map (zip ns') (map (zip cans) (map fst cs)))
-- only sort the arguments where there is no clash in
-- constructor tags between families, the argument type is canonical,
-- and no constructor/constant
-- clash, because otherwise we can't reliable make the
-- case distinction on evaluation
(patnames_ord, patnames_rest)
= Data.List.partition (noClash . map snd) patnames
patnames_ord' = case phase of
CompileTime -> patnames_ord
-- reversing tends to make better case trees
-- and helps erasure
RunTime -> reverse patnames_ord
pats' = transpose (sortBy moreDistinct patnames_ord'
++ patnames_rest) in
(getNOrder pats', zipWith rebuild pats' cs)
where
getNOrder [] = error $ "Failed order on " ++ show (map fst ns', cs)
getNOrder (c : _) = map (fst . fst) c
rebuild patnames clause = (map (snd . snd) patnames, snd clause)
noClash [] = True
noClash ((can, p) : ps) = can && not (any (clashPat p) (map snd ps))
&& noClash ps
clashPat (PCon _ _ _ _) (PConst _) = True
clashPat (PConst _) (PCon _ _ _ _) = True
clashPat (PCon _ _ _ _) (PSuc _) = True
clashPat (PSuc _) (PCon _ _ _ _) = True
clashPat (PCon _ n i _) (PCon _ n' i' _) | i == i' = n /= n'
clashPat _ _ = False
-- this compares (+isInaccessible, -numberOfCases)
moreDistinct xs ys
= compare (snd . fst . head $ xs, numNames [] (map snd ys))
(snd . fst . head $ ys, numNames [] (map snd xs))
numNames xs ((_, PCon _ n _ _) : ps)
| not (Left n `elem` xs) = numNames (Left n : xs) ps
numNames xs ((_, PConst c) : ps)
| not (Right c `elem` xs) = numNames (Right c : xs) ps
numNames xs (_ : ps) = numNames xs ps
numNames xs [] = length xs
-- Reorder the patterns in the clause so that the PInferred patterns come
-- last. Also strip 'PInferred' from the top level patterns so that we can
-- go ahead and match.
orderByInf :: [Name] -> [Clause] -> ([Name], [Clause])
orderByInf vs cs = let alwaysInf = getInf cs in
(selectInf alwaysInf vs,
map deInf (map (selectExp alwaysInf) cs))
where
getInf [] = []
getInf [(pats, def)] = infPos 0 pats
getInf ((pats, def) : cs) = infPos 0 pats `intersect` getInf cs
selectExp :: [Int] -> Clause -> Clause
selectExp infs (pats, def)
= let (notInf, inf) = splitPats 0 infs [] [] pats in
(notInf ++ inf, def)
selectInf :: [Int] -> [a] -> [a]
selectInf infs ns = let (notInf, inf) = splitPats 0 infs [] [] ns in
notInf ++ inf
splitPats i infpos notInf inf [] = (reverse notInf, reverse inf)
splitPats i infpos notInf inf (p : ps)
| i `elem` infpos = splitPats (i + 1) infpos notInf (p : inf) ps
| otherwise = splitPats (i + 1) infpos (p : notInf) inf ps
infPos i [] = []
infPos i (PInferred p : ps) = i : infPos (i + 1) ps
infPos i (_ : ps) = infPos (i + 1) ps
deInf (pats, def) = (map deInfPat pats, def)
deInfPat (PInferred p) = p
deInfPat p = p
match :: [Name] -> [Clause] -> SC -- error case
-> CaseBuilder SC
match [] (([], ret) : xs) err
= do (ts, v, ntys) <- get
put (ts ++ (map (fst.snd) xs), v, ntys)
case snd ret of
Impossible -> return ImpossibleCase
tm -> return $ STerm tm -- run out of arguments
match vs cs err = do let (vs', de_inf) = orderByInf vs cs
ps = partition de_inf
mixture vs' ps err
mixture :: [Name] -> [Partition] -> SC -> CaseBuilder SC
mixture vs [] err = return err
mixture vs (Cons ms : ps) err = do fallthrough <- mixture vs ps err
conRule vs ms fallthrough
mixture vs (Vars ms : ps) err = do fallthrough <- mixture vs ps err
varRule vs ms fallthrough
-- Return the list of inaccessible arguments of a data constructor.
inaccessibleArgs :: Name -> CaseBuilder [Int]
inaccessibleArgs n = do
getInaccessiblePositions <- ask -- this function is the only thing in the environment
return $ getInaccessiblePositions n
data ConType = CName Name Int -- named constructor
| CFn Name -- reflected function name
| CSuc -- n+1
| CConst Const -- constant, not implemented yet
deriving (Show, Eq)
data Group = ConGroup Bool -- Uniqueness flag
ConType -- Constructor
[([Pat], Clause)] -- arguments and rest of alternative
deriving Show
conRule :: [Name] -> [Clause] -> SC -> CaseBuilder SC
conRule (v:vs) cs err = do groups <- groupCons cs
caseGroups (v:vs) groups err
caseGroups :: [Name] -> [Group] -> SC -> CaseBuilder SC
caseGroups (v:vs) gs err = do g <- altGroups gs
return $ Case (getShared gs) v (sort g)
where
getShared (ConGroup True _ _ : _) = Updatable
getShared _ = Shared
altGroups [] = return [DefaultCase err]
altGroups (ConGroup _ (CName n i) args : cs)
= (:) <$> altGroup n i args <*> altGroups cs
altGroups (ConGroup _ (CFn n) args : cs)
= (:) <$> altFnGroup n args <*> altGroups cs
altGroups (ConGroup _ CSuc args : cs)
= (:) <$> altSucGroup args <*> altGroups cs
altGroups (ConGroup _ (CConst c) args : cs)
= (:) <$> altConstGroup c args <*> altGroups cs
altGroup n i args
= do inacc <- inaccessibleArgs n
(newVars, accVars, inaccVars, nextCs) <- argsToAlt inacc args
matchCs <- match (accVars ++ vs ++ inaccVars) nextCs err
return $ ConCase n i newVars matchCs
altFnGroup n args = do (newVars, _, [], nextCs) <- argsToAlt [] args
matchCs <- match (newVars ++ vs) nextCs err
return $ FnCase n newVars matchCs
altSucGroup args = do ([newVar], _, [], nextCs) <- argsToAlt [] args
matchCs <- match (newVar:vs) nextCs err
return $ SucCase newVar matchCs
altConstGroup n args = do (_, _, [], nextCs) <- argsToAlt [] args
matchCs <- match vs nextCs err
return $ ConstCase n matchCs
-- Returns:
-- * names of all variables arising from match
-- * names of accessible variables (subset of all variables)
-- * names of inaccessible variables (subset of all variables)
-- * clauses corresponding to (accVars ++ origVars ++ inaccVars)
argsToAlt :: [Int] -> [([Pat], Clause)] -> CaseBuilder ([Name], [Name], [Name], [Clause])
argsToAlt _ [] = return ([], [], [], [])
argsToAlt inacc rs@((r, m) : rest) = do
newVars <- getNewVars r
let (accVars, inaccVars) = partitionAcc newVars
return (newVars, accVars, inaccVars, addRs rs)
where
-- Create names for new variables arising from the given patterns.
getNewVars :: [Pat] -> CaseBuilder [Name]
getNewVars [] = return []
getNewVars ((PV n t) : ns) = do v <- getVar "e"
nsv <- getNewVars ns
-- Record the type of the variable.
--
-- It seems that the ordering is not important
-- and we can put (v,t) always in front of "ntys"
-- (the varName-type pairs seem to represent a mapping).
--
-- The code that reads this is currently
-- commented out, anyway.
(cs, i, ntys) <- get
put (cs, i, (v, t) : ntys)
return (v : nsv)
getNewVars (PAny : ns) = (:) <$> getVar "i" <*> getNewVars ns
getNewVars (PTyPat : ns) = (:) <$> getVar "t" <*> getNewVars ns
getNewVars (_ : ns) = (:) <$> getVar "e" <*> getNewVars ns
-- Partition a list of things into (accessible, inaccessible) things,
-- according to the list of inaccessible indices.
partitionAcc xs =
( [x | (i,x) <- zip [0..] xs, i `notElem` inacc]
, [x | (i,x) <- zip [0..] xs, i `elem` inacc]
)
addRs [] = []
addRs ((r, (ps, res)) : rs) = ((acc++ps++inacc, res) : addRs rs)
where
(acc, inacc) = partitionAcc r
uniq i (UN n) = MN i n
uniq i n = n
getVar :: String -> CaseBuilder Name
getVar b = do (t, v, ntys) <- get; put (t, v+1, ntys); return (sMN v b)
groupCons :: [Clause] -> CaseBuilder [Group]
groupCons cs = gc [] cs
where
gc acc [] = return acc
gc acc ((p : ps, res) : cs) =
do acc' <- addGroup p ps res acc
gc acc' cs
addGroup p ps res acc = case p of
PCon uniq con i args -> return $ addg uniq (CName con i) args (ps, res) acc
PConst cval -> return $ addConG cval (ps, res) acc
PSuc n -> return $ addg False CSuc [n] (ps, res) acc
PReflected fn args -> return $ addg False (CFn fn) args (ps, res) acc
pat -> fail $ show pat ++ " is not a constructor or constant (can't happen)"
addg uniq c conargs res []
= [ConGroup uniq c [(conargs, res)]]
addg uniq c conargs res (g@(ConGroup _ c' cs):gs)
| c == c' = ConGroup uniq c (cs ++ [(conargs, res)]) : gs
| otherwise = g : addg uniq c conargs res gs
addConG con res [] = [ConGroup False (CConst con) [([], res)]]
addConG con res (g@(ConGroup False (CConst n) cs) : gs)
| con == n = ConGroup False (CConst n) (cs ++ [([], res)]) : gs
-- | otherwise = g : addConG con res gs
addConG con res (g : gs) = g : addConG con res gs
varRule :: [Name] -> [Clause] -> SC -> CaseBuilder SC
varRule (v : vs) alts err =
do alts' <- mapM (repVar v) alts
match vs alts' err
where
repVar v (PV p ty : ps , (lhs, res))
= do (cs, i, ntys) <- get
put (cs, i, (v, ty) : ntys)
return (ps, (lhs, subst p (P Bound v ty) res))
repVar v (PAny : ps , res) = return (ps, res)
repVar v (PTyPat : ps , res) = return (ps, res)
-- fix: case e of S k -> f (S k) ==> case e of S k -> f e
depatt :: [Name] -> SC -> SC
depatt ns tm = dp [] tm
where
dp ms (STerm tm) = STerm (applyMaps ms tm)
dp ms (Case up x alts) = Case up x (map (dpa ms x) alts)
dp ms sc = sc
dpa ms x (ConCase n i args sc)
= ConCase n i args (dp ((x, (n, args)) : ms) sc)
dpa ms x (FnCase n args sc)
= FnCase n args (dp ((x, (n, args)) : ms) sc)
dpa ms x (ConstCase c sc) = ConstCase c (dp ms sc)
dpa ms x (SucCase n sc) = SucCase n (dp ms sc)
dpa ms x (DefaultCase sc) = DefaultCase (dp ms sc)
applyMaps ms f@(App _ _ _)
| (P nt cn pty, args) <- unApply f
= let args' = map (applyMaps ms) args in
applyMap ms nt cn pty args'
where
applyMap [] nt cn pty args' = mkApp (P nt cn pty) args'
applyMap ((x, (n, args)) : ms) nt cn pty args'
| and ((length args == length args') :
(n == cn) : zipWith same args args') = P Ref x Erased
| otherwise = applyMap ms nt cn pty args'
same n (P _ n' _) = n == n'
same _ _ = False
applyMaps ms (App s f a) = App s (applyMaps ms f) (applyMaps ms a)
applyMaps ms t = t
-- FIXME: Do this for SucCase too
-- Issue #1719 on the issue tracker: https://github.com/idris-lang/Idris-dev/issues/1719
prune :: Bool -- ^ Convert single branches to projections (only useful at runtime)
-> SC -> SC
prune proj (Case up n alts) = case alts' of
[] -> ImpossibleCase
-- Projection transformations prevent us from seeing some uses of ctor fields
-- because they delete information about which ctor is being used.
-- Consider:
-- f (X x) = ... x ...
-- vs.
-- f x = ... x!0 ...
--
-- Hence, we disable this step.
-- TODO: re-enable this in toIR
--
-- as@[ConCase cn i args sc]
-- | proj -> mkProj n 0 args (prune proj sc)
-- mkProj n i xs sc = foldr (\x -> projRep x n i) sc xs
-- If none of the args are used in the sc, however, we can just replace it
-- with sc
as@[ConCase cn i args sc]
| proj -> let sc' = prune proj sc in
if any (isUsed sc') args
then Case up n [ConCase cn i args sc']
else sc'
[SucCase cn sc]
| proj
-> projRep cn n (-1) $ prune proj sc
[ConstCase _ sc]
-> prune proj sc
-- Bit of a hack here! The default case will always be 0, make sure
-- it gets caught first.
[s@(SucCase _ _), DefaultCase dc]
-> Case up n [ConstCase (BI 0) dc, s]
as -> Case up n as
where
alts' = filter (not . erased) $ map pruneAlt alts
pruneAlt (ConCase cn i ns sc) = ConCase cn i ns (prune proj sc)
pruneAlt (FnCase cn ns sc) = FnCase cn ns (prune proj sc)
pruneAlt (ConstCase c sc) = ConstCase c (prune proj sc)
pruneAlt (SucCase n sc) = SucCase n (prune proj sc)
pruneAlt (DefaultCase sc) = DefaultCase (prune proj sc)
erased (DefaultCase (STerm Erased)) = True
erased (DefaultCase ImpossibleCase) = True
erased _ = False
projRep :: Name -> Name -> Int -> SC -> SC
projRep arg n i (Case up x alts) | x == arg
= ProjCase (Proj (P Bound n Erased) i) $ map (projRepAlt arg n i) alts
projRep arg n i (Case up x alts)
= Case up x (map (projRepAlt arg n i) alts)
projRep arg n i (ProjCase t alts)
= ProjCase (projRepTm arg n i t) $ map (projRepAlt arg n i) alts
projRep arg n i (STerm t) = STerm (projRepTm arg n i t)
projRep arg n i c = c
projRepAlt arg n i (ConCase cn t args rhs)
= ConCase cn t args (projRep arg n i rhs)
projRepAlt arg n i (FnCase cn args rhs)
= FnCase cn args (projRep arg n i rhs)
projRepAlt arg n i (ConstCase t rhs)
= ConstCase t (projRep arg n i rhs)
projRepAlt arg n i (SucCase sn rhs)
= SucCase sn (projRep arg n i rhs)
projRepAlt arg n i (DefaultCase rhs)
= DefaultCase (projRep arg n i rhs)
projRepTm arg n i t = subst arg (Proj (P Bound n Erased) i) t
prune _ t = t
stripLambdas :: CaseDef -> CaseDef
stripLambdas (CaseDef ns (STerm (Bind x (Lam _ _) sc)) tm)
= stripLambdas (CaseDef (ns ++ [x]) (STerm (instantiate (P Bound x Erased) sc)) tm)
stripLambdas x = x
substSC :: Name -> Name -> SC -> SC
substSC n repl (Case up n' alts)
| n == n' = Case up repl (map (substAlt n repl) alts)
| otherwise = Case up n' (map (substAlt n repl) alts)
substSC n repl (STerm t) = STerm $ subst n (P Bound repl Erased) t
substSC n repl (UnmatchedCase errmsg) = UnmatchedCase errmsg
substSC n repl ImpossibleCase = ImpossibleCase
substSC n repl sc = error $ "unsupported in substSC: " ++ show sc
substAlt :: Name -> Name -> CaseAlt -> CaseAlt
substAlt n repl (ConCase cn a ns sc) = ConCase cn a ns (substSC n repl sc)
substAlt n repl (FnCase fn ns sc) = FnCase fn ns (substSC n repl sc)
substAlt n repl (ConstCase c sc) = ConstCase c (substSC n repl sc)
substAlt n repl (SucCase n' sc)
| n == n' = SucCase n (substSC n repl sc)
| otherwise = SucCase n' (substSC n repl sc)
substAlt n repl (DefaultCase sc) = DefaultCase (substSC n repl sc)
-- mkForce n' n t updates the tree t under the assumption that
-- n' = force n (so basically updating n to n')
mkForce :: Name -> Name -> SC -> SC
mkForce = mkForceSC
where
mkForceSC n arg (Case up x alts) | x == arg
= Case up n $ map (mkForceAlt n arg) alts
mkForceSC n arg (Case up x alts)
= Case up x (map (mkForceAlt n arg) alts)
mkForceSC n arg (ProjCase t alts)
= ProjCase t $ map (mkForceAlt n arg) alts
mkForceSC n arg c = c
mkForceAlt n arg (ConCase cn t args rhs)
= ConCase cn t args (mkForceSC n arg rhs)
mkForceAlt n arg (FnCase cn args rhs)
= FnCase cn args (mkForceSC n arg rhs)
mkForceAlt n arg (ConstCase t rhs)
= ConstCase t (mkForceSC n arg rhs)
mkForceAlt n arg (SucCase sn rhs)
= SucCase sn (mkForceSC n arg rhs)
mkForceAlt n arg (DefaultCase rhs)
= DefaultCase (mkForceSC n arg rhs)
forceTm n arg t = subst n arg t