{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE TupleSections #-}

{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998


Desugaring arrow commands
-}

module GHC.HsToCore.Arrows ( dsProcExpr ) where

import GHC.Prelude

import GHC.HsToCore.Match
import GHC.HsToCore.Utils
import GHC.HsToCore.Monad

import GHC.Hs
import GHC.Hs.Syn.Type

-- NB: The desugarer, which straddles the source and Core worlds, sometimes
--     needs to see source types (newtypes etc), and sometimes not
--     So WATCH OUT; check each use of split*Ty functions.
-- Sigh.  This is a pain.

import {-# SOURCE #-} GHC.HsToCore.Expr ( dsExpr, dsLExpr, dsLocalBinds,
                                          dsSyntaxExpr )

import GHC.Tc.Utils.TcType
import GHC.Core.Multiplicity
import GHC.Tc.Types.Evidence
import GHC.Core
import GHC.Core.FVs
import GHC.Core.Utils
import GHC.Core.Make
import GHC.HsToCore.Binds (dsHsWrapper)


import GHC.Types.Id
import GHC.Core.ConLike
import GHC.Builtin.Types
import GHC.Types.Basic
import GHC.Builtin.Names
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Types.Var.Set
import GHC.Types.SrcLoc
import GHC.Data.List.SetOps( assocMaybe )
import Data.Foldable (toList)
import Data.List (mapAccumL)
import Data.List.NonEmpty (NonEmpty(..), nonEmpty)
import GHC.Utils.Misc
import GHC.Types.Unique.DSet

data DsCmdEnv = DsCmdEnv {
        DsCmdEnv -> CoreExpr
arr_id, DsCmdEnv -> CoreExpr
compose_id, DsCmdEnv -> CoreExpr
first_id, DsCmdEnv -> CoreExpr
app_id, DsCmdEnv -> CoreExpr
choice_id, DsCmdEnv -> CoreExpr
loop_id :: CoreExpr
    }

mkCmdEnv :: CmdSyntaxTable GhcTc -> DsM ([CoreBind], DsCmdEnv)
-- See Note [CmdSyntaxTable] in GHC.Hs.Expr
mkCmdEnv :: CmdSyntaxTable (GhcPass 'Typechecked) -> DsM ([CoreBind], DsCmdEnv)
mkCmdEnv CmdSyntaxTable (GhcPass 'Typechecked)
tc_meths
  = do { (meth_binds, prs) <- ((Name, HsExpr (GhcPass 'Typechecked))
 -> IOEnv (Env DsGblEnv DsLclEnv) (CoreBind, (Name, Id)))
-> CmdSyntaxTable (GhcPass 'Typechecked)
-> IOEnv (Env DsGblEnv DsLclEnv) ([CoreBind], [(Name, Id)])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (Name, HsExpr (GhcPass 'Typechecked))
-> IOEnv (Env DsGblEnv DsLclEnv) (CoreBind, (Name, Id))
forall {a}.
(a, HsExpr (GhcPass 'Typechecked))
-> IOEnv (Env DsGblEnv DsLclEnv) (CoreBind, (a, Id))
mk_bind CmdSyntaxTable (GhcPass 'Typechecked)
tc_meths

       -- NB: Some of these lookups might fail, but that's OK if the
       -- symbol is never used. That's why we use Maybe first and then
       -- panic. An eager panic caused trouble in typecheck/should_compile/tc192
       ; let the_arr_id     = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
arrAName
             the_compose_id = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
composeAName
             the_first_id   = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
firstAName
             the_app_id     = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
appAName
             the_choice_id  = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
choiceAName
             the_loop_id    = [(Name, Id)] -> Name -> Maybe Id
forall a b. Eq a => Assoc a b -> a -> Maybe b
assocMaybe [(Name, Id)]
prs Name
loopAName

       ; return (meth_binds, DsCmdEnv {
               arr_id     = Var (unmaybe the_arr_id arrAName),
               compose_id = Var (unmaybe the_compose_id composeAName),
               first_id   = Var (unmaybe the_first_id firstAName),
               app_id     = Var (unmaybe the_app_id appAName),
               choice_id  = Var (unmaybe the_choice_id choiceAName),
               loop_id    = Var (unmaybe the_loop_id loopAName)
             }) }
  where
    mk_bind :: (a, HsExpr (GhcPass 'Typechecked))
-> IOEnv (Env DsGblEnv DsLclEnv) (CoreBind, (a, Id))
mk_bind (a
std_name, HsExpr (GhcPass 'Typechecked)
expr)
      = do { rhs <- HsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsExpr HsExpr (GhcPass 'Typechecked)
expr
           ; id <- newSysLocalMDs (exprType rhs)
           -- no check needed; these are functions
           ; return (NonRec id rhs, (std_name, id)) }

    unmaybe :: Maybe a -> a -> a
unmaybe Maybe a
Nothing a
name = String -> SDoc -> a
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"mkCmdEnv" (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Not found:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> a -> SDoc
forall a. Outputable a => a -> SDoc
ppr a
name)
    unmaybe (Just a
id) a
_  = a
id

-- arr :: forall b c. (b -> c) -> a b c
do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr DsCmdEnv
ids Type
b_ty Type
c_ty CoreExpr
f = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
arr_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty, CoreExpr
f]

-- (>>>) :: forall b c d. a b c -> a c d -> a b d
do_compose :: DsCmdEnv -> Type -> Type -> Type ->
                CoreExpr -> CoreExpr -> CoreExpr
do_compose :: DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_compose DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty CoreExpr
f CoreExpr
g
  = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
compose_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
d_ty, CoreExpr
f, CoreExpr
g]

-- first :: forall b c d. a b c -> a (b,d) (c,d)
do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_first DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty CoreExpr
f
  = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
first_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
d_ty, CoreExpr
f]

-- app :: forall b c. a (a b c, b) c
do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
do_app DsCmdEnv
ids Type
b_ty Type
c_ty = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
app_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty]

-- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
-- note the swapping of d and c
do_choice :: DsCmdEnv -> Type -> Type -> Type ->
                CoreExpr -> CoreExpr -> CoreExpr
do_choice :: DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_choice DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty CoreExpr
f CoreExpr
g
  = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
choice_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
d_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty, CoreExpr
f, CoreExpr
g]

-- loop :: forall b d c. a (b,d) (c,d) -> a b c
-- note the swapping of d and c
do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_loop DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty CoreExpr
f
  = CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (DsCmdEnv -> CoreExpr
loop_id DsCmdEnv
ids) [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
b_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
d_ty, Type -> CoreExpr
forall b. Type -> Expr b
Type Type
c_ty, CoreExpr
f]

-- premap :: forall b c d. (b -> c) -> a c d -> a b d
-- premap f g = arr f >>> g
do_premap :: DsCmdEnv -> Type -> Type -> Type ->
                CoreExpr -> CoreExpr -> CoreExpr
do_premap :: DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_premap DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty CoreExpr
f CoreExpr
g
   = DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_compose DsCmdEnv
ids Type
b_ty Type
c_ty Type
d_ty (DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr DsCmdEnv
ids Type
b_ty Type
c_ty CoreExpr
f) CoreExpr
g

-- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> a
mkFstExpr :: Type -> Type -> DsM CoreExpr
mkFstExpr :: Type -> Type -> DsM CoreExpr
mkFstExpr Type
a_ty Type
b_ty = do
    a_var <- Type -> DsM Id
newSysLocalMDs Type
a_ty
    b_var <- newSysLocalMDs b_ty
    pair_var <- newSysLocalMDs (mkCorePairTy a_ty b_ty)
    return (Lam pair_var
               (coreCasePair pair_var a_var b_var (Var a_var)))

-- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
mkSndExpr :: Type -> Type -> DsM CoreExpr
mkSndExpr :: Type -> Type -> DsM CoreExpr
mkSndExpr Type
a_ty Type
b_ty = do
    a_var <- Type -> DsM Id
newSysLocalMDs Type
a_ty
    b_var <- newSysLocalMDs b_ty
    pair_var <- newSysLocalMDs (mkCorePairTy a_ty b_ty)
    return (Lam pair_var
               (coreCasePair pair_var a_var b_var (Var b_var)))

{-
Build case analysis of a tuple.  This cannot be done in the DsM monad,
because the list of variables is typically not yet defined.
-}

-- coreCaseTuple [u1..] v [x1..xn] body
--      = case v of v { (x1, .., xn) -> body }
-- But the matching may be nested if the tuple is very big

coreCaseTuple :: Id -> [Id] -> CoreExpr -> DsM CoreExpr
coreCaseTuple :: Id -> [Id] -> CoreExpr -> DsM CoreExpr
coreCaseTuple Id
scrut_var [Id]
vars CoreExpr
body
  = [Id] -> CoreExpr -> CoreExpr -> DsM CoreExpr
forall (m :: * -> *).
MonadUnique m =>
[Id] -> CoreExpr -> CoreExpr -> m CoreExpr
mkBigTupleCase [Id]
vars CoreExpr
body (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
scrut_var)

coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
coreCasePair Id
scrut_var Id
var1 Id
var2 CoreExpr
body
  = CoreExpr -> Id -> Type -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Type -> [Alt b] -> Expr b
Case (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
scrut_var) Id
scrut_var (HasDebugCallStack => CoreExpr -> Type
CoreExpr -> Type
exprType CoreExpr
body)
         [AltCon -> [Id] -> CoreExpr -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt (DataCon -> AltCon
DataAlt (Boxity -> Int -> DataCon
tupleDataCon Boxity
Boxed Int
2)) [Id
var1, Id
var2] CoreExpr
body]

mkCorePairTy :: Type -> Type -> Type
mkCorePairTy :: Type -> Type -> Type
mkCorePairTy Type
t1 Type
t2 = [Type] -> Type
mkBoxedTupleTy [Type
t1, Type
t2]

mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr CoreExpr
e1 CoreExpr
e2 = [CoreExpr] -> CoreExpr
mkCoreTup [CoreExpr
e1, CoreExpr
e2]

mkCoreUnitExpr :: CoreExpr
mkCoreUnitExpr :: CoreExpr
mkCoreUnitExpr = [CoreExpr] -> CoreExpr
mkCoreTup []

{- Note [Environment and stack]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The input is divided into

* A local environment, which is a flat tuple (unless it's too big)
  The elements of the local environment can be
  - of kind Type (for ordinary variables), or
  - of kind Constraint (for dictionaries bound by patterns)

* A stack, which is a right-nested pair.
  The elements on the stack are always of kind Type.

So in general, the input has the form

        ((x1,...,xn), (s1,...(sk,())...))

where xi are the environment values, and si the ones on the stack,
with s1 being the "top", the first one to be matched with a lambda.
-}

envStackType :: [Id] -> Type -> Type
envStackType :: [Id] -> Type -> Type
envStackType [Id]
ids Type
stack_ty = Type -> Type -> Type
mkCorePairTy ([Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
ids) Type
stack_ty

-- splitTypeAt n (t1,... (tn,t)...) = ([t1, ..., tn], t)
splitTypeAt :: Int -> Type -> ([Type], Type)
splitTypeAt :: Int -> Type -> ([Type], Type)
splitTypeAt Int
n Type
ty
  | Int
n Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0 = ([], Type
ty)
  | Bool
otherwise = case Type -> [Type]
tcTyConAppArgs Type
ty of
      [Type
t, Type
ty'] -> let ([Type]
ts, Type
ty_r) = Int -> Type -> ([Type], Type)
splitTypeAt (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
-Int
1) Type
ty' in (Type
tType -> [Type] -> [Type]
forall a. a -> [a] -> [a]
:[Type]
ts, Type
ty_r)
      [Type]
_ -> String -> SDoc -> ([Type], Type)
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"splitTypeAt" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty)

----------------------------------------------
--              buildEnvStack
--
--      ((x1,...,xn),stk)

buildEnvStack :: [Id] -> Id -> CoreExpr
buildEnvStack :: [Id] -> Id -> CoreExpr
buildEnvStack [Id]
env_ids Id
stack_id
  = CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
env_ids) (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
stack_id)

----------------------------------------------
--              matchEnvStack
--
--      \ ((x1,...,xn),stk) -> body
--      =>
--      \ pair ->
--      case pair of (tup,stk) ->
--      case tup of (x1,...,xn) ->
--      body

matchEnvStack   :: [Id]         -- x1..xn
                -> Id           -- stk
                -> CoreExpr     -- e
                -> DsM CoreExpr
matchEnvStack :: [Id] -> Id -> CoreExpr -> DsM CoreExpr
matchEnvStack [Id]
env_ids Id
stack_id CoreExpr
body = do
    tup_var <- Type -> DsM Id
newSysLocalMDs ([Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids)
    match_env <- coreCaseTuple tup_var env_ids body
    pair_id <- newSysLocalMDs (mkCorePairTy (idType tup_var) (idType stack_id))
    return (Lam pair_id (coreCasePair pair_id tup_var stack_id match_env))

----------------------------------------------
--              matchEnv
--
--      \ (x1,...,xn) -> body
--      =>
--      \ tup ->
--      case tup of (x1,...,xn) ->
--      body

matchEnv :: [Id]        -- x1..xn
         -> CoreExpr    -- e
         -> DsM CoreExpr
matchEnv :: [Id] -> CoreExpr -> DsM CoreExpr
matchEnv [Id]
env_ids CoreExpr
body = do
    tup_id <- Type -> DsM Id
newSysLocalMDs ([Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids)
    tup_case <- coreCaseTuple tup_id env_ids body
    return (Lam tup_id tup_case)

----------------------------------------------
--              matchVarStack
--
--      case (x1, ...(xn, s)...) -> e
--      =>
--      case z0 of (x1,z1) ->
--      case zn-1 of (xn,s) ->
--      e
matchVarStack :: [Id] -> Id -> CoreExpr -> DsM (Id, CoreExpr)
matchVarStack :: [Id] -> Id -> CoreExpr -> DsM (Id, CoreExpr)
matchVarStack [] Id
stack_id CoreExpr
body = (Id, CoreExpr) -> DsM (Id, CoreExpr)
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Id
stack_id, CoreExpr
body)
matchVarStack (Id
param_id:[Id]
param_ids) Id
stack_id CoreExpr
body = do
    (tail_id, tail_code) <- [Id] -> Id -> CoreExpr -> DsM (Id, CoreExpr)
matchVarStack [Id]
param_ids Id
stack_id CoreExpr
body
    pair_id <- newSysLocalMDs (mkCorePairTy (idType param_id) (idType tail_id))
    return (pair_id, coreCasePair pair_id param_id tail_id tail_code)

mkHsEnvStackExpr :: [Id] -> Id -> LHsExpr GhcTc
mkHsEnvStackExpr :: [Id] -> Id -> LHsExpr (GhcPass 'Typechecked)
mkHsEnvStackExpr [Id]
env_ids Id
stack_id
  = [LHsExpr (GhcPass 'Typechecked)]
-> XExplicitTuple (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
forall (p :: Pass).
[LHsExpr (GhcPass p)]
-> XExplicitTuple (GhcPass p) -> LHsExpr (GhcPass p)
mkLHsTupleExpr [[IdP (GhcPass 'Typechecked)]
-> XExplicitTuple (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
forall (p :: Pass) a.
IsSrcSpanAnn p a =>
[IdP (GhcPass p)]
-> XExplicitTuple (GhcPass p) -> LHsExpr (GhcPass p)
mkLHsVarTuple [IdP (GhcPass 'Typechecked)]
[Id]
env_ids XExplicitTuple (GhcPass 'Typechecked)
NoExtField
noExtField, IdP (GhcPass 'Typechecked) -> LHsExpr (GhcPass 'Typechecked)
forall (p :: Pass) a.
IsSrcSpanAnn p a =>
IdP (GhcPass p) -> LHsExpr (GhcPass p)
nlHsVar IdP (GhcPass 'Typechecked)
Id
stack_id]
                   XExplicitTuple (GhcPass 'Typechecked)
NoExtField
noExtField

-- Translation of arrow abstraction

-- D; xs |-a c : () --> t'      ---> c'
-- --------------------------
-- D |- proc p -> c :: a t t'   ---> premap (\ p -> ((xs),())) c'
--
--              where (xs) is the tuple of variables bound by p

dsProcExpr
        :: LPat GhcTc
        -> LHsCmdTop GhcTc
        -> DsM CoreExpr
dsProcExpr :: LPat (GhcPass 'Typechecked)
-> LHsCmdTop (GhcPass 'Typechecked) -> DsM CoreExpr
dsProcExpr LPat (GhcPass 'Typechecked)
pat (L EpAnnCO
_ (HsCmdTop (CmdTopTc Type
_unitTy Type
cmd_ty CmdSyntaxTable (GhcPass 'Typechecked)
ids) LHsCmd (GhcPass 'Typechecked)
cmd)) = do
    (meth_binds, meth_ids) <- CmdSyntaxTable (GhcPass 'Typechecked) -> DsM ([CoreBind], DsCmdEnv)
mkCmdEnv CmdSyntaxTable (GhcPass 'Typechecked)
ids
    let locals = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> LPat (GhcPass 'Typechecked) -> [IdP (GhcPass 'Typechecked)]
forall p. CollectPass p => CollectFlag p -> LPat p -> [IdP p]
collectPatBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders LPat (GhcPass 'Typechecked)
pat)
    (core_cmd, _free_vars, env_ids)
       <- dsfixCmd meth_ids locals unitTy cmd_ty cmd
    let env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
    let env_stk_ty = Type -> Type -> Type
mkCorePairTy Type
env_ty Type
unitTy
    let env_stk_expr = CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
env_ids) CoreExpr
mkCoreUnitExpr
    fail_expr <- mkFailExpr (ArrowMatchCtxt ProcExpr) env_stk_ty
    var <- selectSimpleMatchVarL ManyTy pat
    match_code <- matchSimply (Var var) (ArrowMatchCtxt ProcExpr) ManyTy pat env_stk_expr fail_expr
    let pat_ty = LPat (GhcPass 'Typechecked) -> Type
hsLPatType LPat (GhcPass 'Typechecked)
pat
    let proc_code = DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_premap DsCmdEnv
meth_ids Type
pat_ty Type
env_stk_ty Type
cmd_ty
                    (Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
var CoreExpr
match_code)
                    CoreExpr
core_cmd
    return (mkLets meth_binds proc_code)

{-
Translation of a command judgement of the form

        D; xs |-a c : stk --> t

to an expression e such that

        D |- e :: a (xs, stk) t
-}

dsLCmd :: DsCmdEnv -> IdSet -> Type -> Type -> LHsCmd GhcTc -> [Id]
       -> DsM (CoreExpr, DIdSet)
dsLCmd :: DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsLCmd DsCmdEnv
ids VarSet
local_vars Type
stk_ty Type
res_ty LHsCmd (GhcPass 'Typechecked)
cmd [Id]
env_ids
  = DsCmdEnv
-> VarSet
-> Type
-> Type
-> HsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmd DsCmdEnv
ids VarSet
local_vars Type
stk_ty Type
res_ty (LocatedA (HsCmd (GhcPass 'Typechecked))
-> HsCmd (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc LHsCmd (GhcPass 'Typechecked)
LocatedA (HsCmd (GhcPass 'Typechecked))
cmd) [Id]
env_ids

dsCmd   :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this command
        -> Type                 -- type of the stack (right-nested tuple)
        -> Type                 -- return type of the command
        -> HsCmd GhcTc           -- command to desugar
        -> [Id]           -- list of vars in the input to this command
                                -- This is typically fed back,
                                -- so don't pull on it too early
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet)         -- subset of local vars that occur free

-- D |- fun :: a t1 t2
-- D, xs |- arg :: t1
-- -----------------------------
-- D; xs |-a fun -< arg : stk --> t2
--
--              ---> premap (\ ((xs), _stk) -> arg) fun

dsCmd :: DsCmdEnv
-> VarSet
-> Type
-> Type
-> HsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty
        (HsCmdArrApp XCmdArrApp (GhcPass 'Typechecked)
arrow_ty LHsExpr (GhcPass 'Typechecked)
arrow LHsExpr (GhcPass 'Typechecked)
arg HsArrAppType
HsFirstOrderApp Bool
_)
        [Id]
env_ids = do
    let
        (Type
a_arg_ty, Type
_res_ty') = Type -> (Type, Type)
tcSplitAppTy XCmdArrApp (GhcPass 'Typechecked)
Type
arrow_ty
        (Type
_a_ty, Type
arg_ty) = Type -> (Type, Type)
tcSplitAppTy Type
a_arg_ty
    core_arrow <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr LHsExpr (GhcPass 'Typechecked)
arrow
    core_arg   <- dsLExpr arg
    stack_id   <- newSysLocalMDs stack_ty
    core_make_arg <- matchEnvStack env_ids stack_id core_arg
    return (do_premap ids
              (envStackType env_ids stack_ty)
              arg_ty
              res_ty
              core_make_arg
              core_arrow,
            exprFreeIdsDSet core_arg `uniqDSetIntersectUniqSet` local_vars)

-- D, xs |- fun :: a t1 t2
-- D, xs |- arg :: t1
-- ------------------------------
-- D; xs |-a fun -<< arg : stk --> t2
--
--              ---> premap (\ ((xs), _stk) -> (fun, arg)) app

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty
        (HsCmdArrApp XCmdArrApp (GhcPass 'Typechecked)
arrow_ty LHsExpr (GhcPass 'Typechecked)
arrow LHsExpr (GhcPass 'Typechecked)
arg HsArrAppType
HsHigherOrderApp Bool
_)
        [Id]
env_ids = do
    let
        (Type
a_arg_ty, Type
_res_ty') = Type -> (Type, Type)
tcSplitAppTy XCmdArrApp (GhcPass 'Typechecked)
Type
arrow_ty
        (Type
_a_ty, Type
arg_ty) = Type -> (Type, Type)
tcSplitAppTy Type
a_arg_ty

    core_arrow <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr LHsExpr (GhcPass 'Typechecked)
arrow
    core_arg   <- dsLExpr arg
    stack_id   <- newSysLocalMDs stack_ty
    core_make_pair <- matchEnvStack env_ids stack_id
          (mkCorePairExpr core_arrow core_arg)

    return (do_premap ids
              (envStackType env_ids stack_ty)
              (mkCorePairTy arrow_ty arg_ty)
              res_ty
              core_make_pair
              (do_app ids arg_ty res_ty),
            (exprsFreeIdsDSet [core_arrow, core_arg])
              `uniqDSetIntersectUniqSet` local_vars)

-- D; ys |-a cmd : (t,stk) --> t'
-- D, xs |-  exp :: t
-- ------------------------
-- D; xs |-a cmd exp : stk --> t'
--
--              ---> premap (\ ((xs),stk) -> ((ys),(e,stk))) cmd

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdApp XCmdApp (GhcPass 'Typechecked)
_ LHsCmd (GhcPass 'Typechecked)
cmd LHsExpr (GhcPass 'Typechecked)
arg) [Id]
env_ids = do
    core_arg <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr LHsExpr (GhcPass 'Typechecked)
arg
    let
        arg_ty = HasDebugCallStack => CoreExpr -> Type
CoreExpr -> Type
exprType CoreExpr
core_arg
        stack_ty' = Type -> Type -> Type
mkCorePairTy Type
arg_ty Type
stack_ty
    (core_cmd, free_vars, env_ids')
             <- dsfixCmd ids local_vars stack_ty' res_ty cmd
    stack_id <- newSysLocalMDs stack_ty
    arg_id <- newSysLocalMDs arg_ty
    -- push the argument expression onto the stack
    let
        stack' = CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
arg_id) (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
stack_id)
        core_body = HasDebugCallStack => Id -> CoreExpr -> CoreExpr -> CoreExpr
Id -> CoreExpr -> CoreExpr -> CoreExpr
bindNonRec Id
arg_id CoreExpr
core_arg
                        (CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
env_ids') CoreExpr
stack')

    -- match the environment and stack against the input
    core_map <- matchEnvStack env_ids stack_id core_body
    return (do_premap ids
                      (envStackType env_ids stack_ty)
                      (envStackType env_ids' stack_ty')
                      res_ty
                      core_map
                      core_cmd,
            free_vars `unionDVarSet`
              (exprFreeIdsDSet core_arg `uniqDSetIntersectUniqSet` local_vars))

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdPar XCmdPar (GhcPass 'Typechecked)
_ LHsCmd (GhcPass 'Typechecked)
cmd) [Id]
env_ids
  = DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsLCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty LHsCmd (GhcPass 'Typechecked)
cmd [Id]
env_ids

-- D, xs |- e :: Bool
-- D; xs1 |-a c1 : stk --> t
-- D; xs2 |-a c2 : stk --> t
-- ----------------------------------------
-- D; xs |-a if e then c1 else c2 : stk --> t
--
--              ---> premap (\ ((xs),stk) ->
--                       if e then Left ((xs1),stk) else Right ((xs2),stk))
--                     (c1 ||| c2)

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdIf XCmdIf (GhcPass 'Typechecked)
_ SyntaxExpr (GhcPass 'Typechecked)
mb_fun LHsExpr (GhcPass 'Typechecked)
cond LHsCmd (GhcPass 'Typechecked)
then_cmd LHsCmd (GhcPass 'Typechecked)
else_cmd)
        [Id]
env_ids = do
    core_cond <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr LHsExpr (GhcPass 'Typechecked)
cond
    (core_then, fvs_then, then_ids)
       <- dsfixCmd ids local_vars stack_ty res_ty then_cmd
    (core_else, fvs_else, else_ids)
       <- dsfixCmd ids local_vars stack_ty res_ty else_cmd
    stack_id   <- newSysLocalMDs stack_ty
    either_con <- dsLookupTyCon eitherTyConName
    left_con   <- dsLookupDataCon leftDataConName
    right_con  <- dsLookupDataCon rightDataConName

    let mk_left_expr Type
ty1 Type
ty2 CoreExpr
e = DataCon -> [CoreExpr] -> CoreExpr
mkCoreConApps DataCon
left_con   [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty1,Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty2, CoreExpr
e]
        mk_right_expr Type
ty1 Type
ty2 CoreExpr
e = DataCon -> [CoreExpr] -> CoreExpr
mkCoreConApps DataCon
right_con [Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty1,Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty2, CoreExpr
e]

        in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty
        then_ty = [Id] -> Type -> Type
envStackType [Id]
then_ids Type
stack_ty
        else_ty = [Id] -> Type -> Type
envStackType [Id]
else_ids Type
stack_ty
        sum_ty = TyCon -> [Type] -> Type
mkTyConApp TyCon
either_con [Type
then_ty, Type
else_ty]
        fvs_cond = CoreExpr -> DIdSet
exprFreeIdsDSet CoreExpr
core_cond
                   DIdSet -> VarSet -> DIdSet
forall a. UniqDSet a -> UniqSet a -> UniqDSet a
`uniqDSetIntersectUniqSet` VarSet
local_vars

        core_left  = Type -> Type -> CoreExpr -> CoreExpr
mk_left_expr  Type
then_ty Type
else_ty
                       ([Id] -> Id -> CoreExpr
buildEnvStack [Id]
then_ids Id
stack_id)
        core_right = Type -> Type -> CoreExpr -> CoreExpr
mk_right_expr Type
then_ty Type
else_ty
                       ([Id] -> Id -> CoreExpr
buildEnvStack [Id]
else_ids Id
stack_id)

    core_if <- case mb_fun of
       SyntaxExpr (GhcPass 'Typechecked)
SyntaxExprTc
NoSyntaxExprTc  -> [Id] -> Id -> CoreExpr -> DsM CoreExpr
matchEnvStack [Id]
env_ids Id
stack_id (CoreExpr -> DsM CoreExpr) -> CoreExpr -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$
                          CoreExpr -> CoreExpr -> CoreExpr -> CoreExpr
mkIfThenElse CoreExpr
core_cond CoreExpr
core_left CoreExpr
core_right
       SyntaxExpr (GhcPass 'Typechecked)
_ -> do { fun_apps <- SyntaxExpr (GhcPass 'Typechecked) -> [CoreExpr] -> DsM CoreExpr
dsSyntaxExpr SyntaxExpr (GhcPass 'Typechecked)
mb_fun
                                      [CoreExpr
core_cond, CoreExpr
core_left, CoreExpr
core_right]
               ; matchEnvStack env_ids stack_id fun_apps }

    return (do_premap ids in_ty sum_ty res_ty
                core_if
                (do_choice ids then_ty else_ty res_ty core_then core_else),
        fvs_cond `unionDVarSet` fvs_then `unionDVarSet` fvs_else)

{-
Note [Desugaring HsCmdCase]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Case commands are treated in much the same way as if commands
(see above) except that there are more alternatives.  For example

        case e of { p1 -> c1; p2 -> c2; p3 -> c3 }

is translated to

        premap (\ ((xs)*ts) -> case e of
                p1 -> (Left (Left (xs1)*ts))
                p2 -> Left ((Right (xs2)*ts))
                p3 -> Right ((xs3)*ts))
        ((c1 ||| c2) ||| c3)

The idea is to extract the commands from the case, build a balanced tree
of choices, and replace the commands with expressions that build tagged
tuples, obtaining a case expression that can be desugared normally.
To build all this, we use triples describing segments of the list of
case bodies, containing the following fields:
 * a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
   into the case replacing the commands
 * a sum type that is the common type of these expressions, and also the
   input type of the arrow
 * a CoreExpr for an arrow built by combining the translated command
   bodies with |||.
-}

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdCase XCmdCase (GhcPass 'Typechecked)
_ LHsExpr (GhcPass 'Typechecked)
exp MatchGroup (GhcPass 'Typechecked) (LHsCmd (GhcPass 'Typechecked))
match) [Id]
env_ids = do
    stack_id <- Type -> DsM Id
newSysLocalMDs Type
stack_ty
    (match', core_choices)
      <- dsCases ids local_vars stack_id stack_ty res_ty match
    let MG{ mg_ext = MatchGroupTc _ sum_ty _ } = match'
        in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty

    core_body <- dsExpr (HsCase (ArrowMatchCtxt ArrowCaseAlt) exp match')

    core_matches <- matchEnvStack env_ids stack_id core_body
    return (do_premap ids in_ty sum_ty res_ty core_matches core_choices,
            exprFreeIdsDSet core_body `uniqDSetIntersectUniqSet` local_vars)

{-
\cases and \case are desugared analogously to a case command (see above).
For example

        \cases {p1 q1 -> c1; p2 q2 -> c2; p3 q3 -> c3 }

is translated to

        premap (\ ((xs), (e1, (e2,stk))) -> cases e1 e2 of
                  p1 q1 -> (Left (Left (xs1), stk))
                  p2 q2 -> Left ((Right (xs2), stk))
                  p3 q3 -> Right ((xs3), stk))
        ((c1 ||| c2) ||| c3)

(cases...of is hypothetical notation that works like case...of but with
multiple scrutinees)

-}
dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty
        (HsCmdLam XCmdLamCase (GhcPass 'Typechecked)
_ HsLamVariant
LamSingle (MG { mg_alts :: forall p body. MatchGroup p body -> XRec p [LMatch p body]
mg_alts
          = (L SrcSpanAnnLW
_ [L SrcSpanAnnA
_ (Match { m_pats :: forall p body. Match p body -> XRec p [LPat p]
m_pats  = L EpaLocation
_ [GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))]
pats
                             , m_grhss :: forall p body. Match p body -> GRHSs p body
m_grhss = GRHSs XCGRHSs
  (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked)))
_ [L EpAnnCO
_ (GRHS XCGRHS
  (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked)))
_ [] LocatedA (HsCmd (GhcPass 'Typechecked))
body)] HsLocalBinds (GhcPass 'Typechecked)
_ })]) }))
        [Id]
env_ids
  = DsCmdEnv
-> VarSet
-> Type
-> Type
-> [LPat (GhcPass 'Typechecked)]
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdLam DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty [LPat (GhcPass 'Typechecked)]
[GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))]
pats LHsCmd (GhcPass 'Typechecked)
LocatedA (HsCmd (GhcPass 'Typechecked))
body [Id]
env_ids

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty
      (HsCmdLam XCmdLamCase (GhcPass 'Typechecked)
_ HsLamVariant
lam_variant match :: MatchGroup (GhcPass 'Typechecked) (LHsCmd (GhcPass 'Typechecked))
match@MG { mg_ext :: forall p body. MatchGroup p body -> XMG p body
mg_ext = MatchGroupTc {mg_arg_tys :: MatchGroupTc -> [Scaled Type]
mg_arg_tys = [Scaled Type]
arg_tys} } )
      [Id]
env_ids = do
    arg_ids <- [Scaled Type] -> DsM [Id]
newSysLocalsDs [Scaled Type]
arg_tys

    let match_ctxt = HsLamVariant -> HsArrowMatchContext
ArrowLamAlt HsLamVariant
lam_variant
        pat_vars = [Id] -> VarSet
mkVarSet [Id]
arg_ids
        local_vars' = VarSet
pat_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars
        (pat_tys, stack_ty') = splitTypeAt (length arg_tys) stack_ty

    -- construct and desugar a case expression with multiple scrutinees
    (core_body, free_vars, env_ids') <- trimInput \[Id]
env_ids -> do
      stack_id <- Type -> DsM Id
newSysLocalMDs Type
stack_ty'
      (match', core_choices)
        <- dsCases ids local_vars' stack_id stack_ty' res_ty match

      let MG{ mg_ext = MatchGroupTc _ sum_ty _ } = match'
          in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty'
          discrims = (Id -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> [Id] -> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
forall a b. (a -> b) -> [a] -> [b]
map IdP (GhcPass 'Typechecked) -> LHsExpr (GhcPass 'Typechecked)
Id -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall (p :: Pass) a.
IsSrcSpanAnn p a =>
IdP (GhcPass p) -> LHsExpr (GhcPass p)
nlHsVar [Id]
arg_ids
      (discrim_vars, matching_code)
        <- matchWrapper (ArrowMatchCtxt match_ctxt) (Just discrims) match'
      core_body <- flip (bind_vars discrim_vars) matching_code <$>
        traverse dsLExpr discrims

      core_matches <- matchEnvStack env_ids stack_id core_body
      return (do_premap ids in_ty sum_ty res_ty core_matches core_choices,
              exprFreeIdsDSet core_body `uniqDSetIntersectUniqSet` local_vars')

    param_ids <- newSysLocalsMDs pat_tys
    stack_id' <- newSysLocalMDs stack_ty'

    -- the expression is built from the inside out, so the actions
    -- are presented in reverse order

    let -- build a new environment, plus what's left of the stack
        core_expr = [Id] -> Id -> CoreExpr
buildEnvStack [Id]
env_ids' Id
stack_id'
        in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty
        in_ty' = [Id] -> Type -> Type
envStackType [Id]
env_ids' Type
stack_ty'

    -- bind the scrutinees to the parameters
    let match_code = [Id] -> [CoreExpr] -> CoreExpr -> CoreExpr
bind_vars [Id]
arg_ids ((Id -> CoreExpr) -> [Id] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map Id -> CoreExpr
forall b. Id -> Expr b
Var [Id]
param_ids) CoreExpr
core_expr

    -- match the parameters against the top of the old stack
    (stack_id, param_code) <- matchVarStack param_ids stack_id' match_code
    -- match the old environment and stack against the input
    select_code <- matchEnvStack env_ids stack_id param_code
    return (do_premap ids in_ty in_ty' res_ty select_code core_body,
            free_vars `uniqDSetMinusUniqSet` pat_vars)
    where
      bind_vars :: [Id] -> [CoreExpr] -> CoreExpr -> CoreExpr
bind_vars [Id]
vars [CoreExpr]
exprs CoreExpr
expr = ((Id, CoreExpr) -> CoreExpr -> CoreExpr)
-> CoreExpr -> [(Id, CoreExpr)] -> CoreExpr
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ((Id -> CoreExpr -> CoreExpr -> CoreExpr)
-> (Id, CoreExpr) -> CoreExpr -> CoreExpr
forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry HasDebugCallStack => Id -> CoreExpr -> CoreExpr -> CoreExpr
Id -> CoreExpr -> CoreExpr -> CoreExpr
bindNonRec) CoreExpr
expr ([(Id, CoreExpr)] -> CoreExpr) -> [(Id, CoreExpr)] -> CoreExpr
forall a b. (a -> b) -> a -> b
$ [Id] -> [CoreExpr] -> [(Id, CoreExpr)]
forall a b. [a] -> [b] -> [(a, b)]
zip [Id]
vars [CoreExpr]
exprs

-- D; ys |-a cmd : stk --> t
-- ----------------------------------
-- D; xs |-a let binds in cmd : stk --> t
--
--              ---> premap (\ ((xs),stk) -> let binds in ((ys),stk)) c

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdLet XCmdLet (GhcPass 'Typechecked)
_ lbinds :: HsLocalBinds (GhcPass 'Typechecked)
lbinds@HsLocalBinds (GhcPass 'Typechecked)
binds LHsCmd (GhcPass 'Typechecked)
body) [Id]
env_ids = do
    let
        defined_vars :: VarSet
defined_vars = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> HsLocalBinds (GhcPass 'Typechecked)
-> [IdP (GhcPass 'Typechecked)]
forall (idL :: Pass) (idR :: Pass).
CollectPass (GhcPass idL) =>
CollectFlag (GhcPass idL)
-> HsLocalBindsLR (GhcPass idL) (GhcPass idR)
-> [IdP (GhcPass idL)]
collectLocalBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders HsLocalBinds (GhcPass 'Typechecked)
binds)
        local_vars' :: VarSet
local_vars' = VarSet
defined_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars

    (core_body, _free_vars, env_ids')
       <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids VarSet
local_vars' Type
stack_ty Type
res_ty LHsCmd (GhcPass 'Typechecked)
body
    stack_id <- newSysLocalMDs stack_ty
    -- build a new environment, plus the stack, using the let bindings
    core_binds <- dsLocalBinds lbinds (buildEnvStack env_ids' stack_id)
    -- match the old environment and stack against the input
    core_map <- matchEnvStack env_ids stack_id core_binds
    return (do_premap ids
                        (envStackType env_ids stack_ty)
                        (envStackType env_ids' stack_ty)
                        res_ty
                        core_map
                        core_body,
        exprFreeIdsDSet core_binds `uniqDSetIntersectUniqSet` local_vars)

-- D; xs |-a ss : t
-- ----------------------------------
-- D; xs |-a do { ss } : () --> t
--
--              ---> premap (\ (env,stk) -> env) c

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (HsCmdDo XCmdDo (GhcPass 'Typechecked)
_ (L SrcSpanAnnLW
_ [GenLocated
   SrcSpanAnnA
   (StmtLR
      (GhcPass 'Typechecked)
      (GhcPass 'Typechecked)
      (LocatedA (HsCmd (GhcPass 'Typechecked))))]
stmts)) [Id]
env_ids = do
    (core_stmts, env_ids') <- DsCmdEnv
-> VarSet
-> Type
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdDo DsCmdEnv
ids VarSet
local_vars Type
res_ty [CmdLStmt (GhcPass 'Typechecked)]
[GenLocated
   SrcSpanAnnA
   (StmtLR
      (GhcPass 'Typechecked)
      (GhcPass 'Typechecked)
      (LocatedA (HsCmd (GhcPass 'Typechecked))))]
stmts [Id]
env_ids
    let env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
    core_fst <- mkFstExpr env_ty stack_ty
    return (do_premap ids
                (mkCorePairTy env_ty stack_ty)
                env_ty
                res_ty
                core_fst
                core_stmts,
        env_ids')

-- D |- e :: forall e. a1 (e,stk1) t1 -> ... an (e,stkn) tn -> a (e,stk) t
-- D; xs |-a ci :: stki --> ti
-- -----------------------------------
-- D; xs |-a (|e c1 ... cn|) :: stk --> t       ---> e [t_xs] c1 ... cn

dsCmd DsCmdEnv
_ VarSet
local_vars Type
_stack_ty Type
_res_ty (HsCmdArrForm XCmdArrForm (GhcPass 'Typechecked)
_ LHsExpr (GhcPass 'Typechecked)
op LexicalFixity
_ [LHsCmdTop (GhcPass 'Typechecked)]
args) [Id]
env_ids = do
    let env_ty :: Type
env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
    core_op <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr LHsExpr (GhcPass 'Typechecked)
op
    (core_args, fv_sets) <- mapAndUnzipM (dsTrimCmdArg local_vars env_ids) args
    return (mkApps (App core_op (Type env_ty)) core_args,
            unionDVarSets fv_sets)

dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty (XCmd (HsWrap HsWrapper
wrap HsCmd (GhcPass 'Typechecked)
cmd)) [Id]
env_ids = do
    (core_cmd, env_ids') <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> HsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmd DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty HsCmd (GhcPass 'Typechecked)
cmd [Id]
env_ids
    dsHsWrapper wrap $ \CoreExpr -> CoreExpr
core_wrap ->
      (CoreExpr, DIdSet) -> DsM (CoreExpr, DIdSet)
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> CoreExpr
core_wrap CoreExpr
core_cmd, DIdSet
env_ids')

-- D; ys |-a c : stk --> t      (ys <= xs)
-- ---------------------
-- D; xs |-a c : stk --> t      ---> premap (\ ((xs),stk) -> ((ys),stk)) c

dsTrimCmdArg
        :: IdSet                -- set of local vars available to this command
        -> [Id]           -- list of vars in the input to this command
        -> LHsCmdTop GhcTc       -- command argument to desugar
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet)         -- subset of local vars that occur free
dsTrimCmdArg :: VarSet
-> [Id]
-> LHsCmdTop (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet)
dsTrimCmdArg VarSet
local_vars [Id]
env_ids
                       (L EpAnnCO
_ (HsCmdTop
                                 (CmdTopTc Type
stack_ty Type
cmd_ty CmdSyntaxTable (GhcPass 'Typechecked)
ids) LHsCmd (GhcPass 'Typechecked)
cmd )) = do
    (meth_binds, meth_ids) <- CmdSyntaxTable (GhcPass 'Typechecked) -> DsM ([CoreBind], DsCmdEnv)
mkCmdEnv CmdSyntaxTable (GhcPass 'Typechecked)
ids
    (core_cmd, free_vars, env_ids')
       <- dsfixCmd meth_ids local_vars stack_ty cmd_ty cmd
    stack_id <- newSysLocalMDs stack_ty
    trim_code
      <- matchEnvStack env_ids stack_id (buildEnvStack env_ids' stack_id)
    let
        in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty
        in_ty' = [Id] -> Type -> Type
envStackType [Id]
env_ids' Type
stack_ty
        arg_code = if [Id]
env_ids' [Id] -> [Id] -> Bool
forall a. Eq a => a -> a -> Bool
== [Id]
env_ids then CoreExpr
core_cmd else
                DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_premap DsCmdEnv
meth_ids Type
in_ty Type
in_ty' Type
cmd_ty CoreExpr
trim_code CoreExpr
core_cmd
    return (mkLets meth_binds arg_code, free_vars)

-- Given D; xs |-a c : stk --> t, builds c with xs fed back.
-- Typically needs to be prefixed with arr (\(p, stk) -> ((xs),stk))

dsfixCmd
        :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this command
        -> Type                 -- type of the stack (right-nested tuple)
        -> Type                 -- return type of the command
        -> LHsCmd GhcTc         -- command to desugar
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet,         -- subset of local vars that occur free
                [Id])           -- the same local vars as a list, fed back
dsfixCmd :: DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids VarSet
local_vars Type
stk_ty Type
cmd_ty LHsCmd (GhcPass 'Typechecked)
cmd
  = ([Id] -> DsM (CoreExpr, DIdSet)) -> DsM (CoreExpr, DIdSet, [Id])
trimInput (DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsLCmd DsCmdEnv
ids VarSet
local_vars Type
stk_ty Type
cmd_ty LHsCmd (GhcPass 'Typechecked)
cmd)

-- Feed back the list of local variables actually used a command,
-- for use as the input tuple of the generated arrow.

trimInput
        :: ([Id] -> DsM (CoreExpr, DIdSet))
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet,         -- subset of local vars that occur free
                [Id])           -- same local vars as a list, fed back to
                                -- the inner function to form the tuple of
                                -- inputs to the arrow.
trimInput :: ([Id] -> DsM (CoreExpr, DIdSet)) -> DsM (CoreExpr, DIdSet, [Id])
trimInput [Id] -> DsM (CoreExpr, DIdSet)
build_arrow
  = ((CoreExpr, DIdSet, [Id]) -> DsM (CoreExpr, DIdSet, [Id]))
-> DsM (CoreExpr, DIdSet, [Id])
forall a. (a -> DsM a) -> DsM a
fixDs (\ ~(CoreExpr
_,DIdSet
_,[Id]
env_ids) -> do
        (core_cmd, free_vars) <- [Id] -> DsM (CoreExpr, DIdSet)
build_arrow [Id]
env_ids
        return (core_cmd, free_vars, dVarSetElems free_vars))

-- Desugaring for both HsCmdLam
--
-- D; ys |-a cmd : stk t'
-- -----------------------------------------------
-- D; xs |-a \ p1 ... pk -> cmd : (t1,...(tk,stk)...) t'
--
--              ---> premap (\ ((xs), (p1, ... (pk,stk)...)) -> ((ys),stk)) cmd
dsCmdLam :: DsCmdEnv            -- arrow combinators
         -> IdSet               -- set of local vars available to this command
         -> Type                -- type of the stack (right-nested tuple)
         -> Type                -- return type of the command
         -> [LPat GhcTc]        -- argument patterns to desugar
         -> LHsCmd GhcTc        -- body to desugar
         -> [Id]                -- list of vars in the input to this command
                                -- This is typically fed back,
                                -- so don't pull on it too early
         -> DsM (CoreExpr,      -- desugared expression
                 DIdSet)        -- subset of local vars that occur free
dsCmdLam :: DsCmdEnv
-> VarSet
-> Type
-> Type
-> [LPat (GhcPass 'Typechecked)]
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdLam DsCmdEnv
ids VarSet
local_vars Type
stack_ty Type
res_ty [LPat (GhcPass 'Typechecked)]
pats LHsCmd (GhcPass 'Typechecked)
body [Id]
env_ids = do
    let pat_vars :: VarSet
pat_vars = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> [LPat (GhcPass 'Typechecked)] -> [IdP (GhcPass 'Typechecked)]
forall p. CollectPass p => CollectFlag p -> [LPat p] -> [IdP p]
collectPatsBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders [LPat (GhcPass 'Typechecked)]
pats)
    let local_vars' :: VarSet
local_vars' = VarSet
pat_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars
        ([Type]
pat_tys, Type
stack_ty') = Int -> Type -> ([Type], Type)
splitTypeAt ([GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [LPat (GhcPass 'Typechecked)]
[GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))]
pats) Type
stack_ty
    (core_body, free_vars, env_ids')
       <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids VarSet
local_vars' Type
stack_ty' Type
res_ty LHsCmd (GhcPass 'Typechecked)
body
    param_ids <- newSysLocalsMDs pat_tys
    stack_id' <- newSysLocalMDs stack_ty'

    -- the expression is built from the inside out, so the actions
    -- are presented in reverse order

    let -- build a new environment, plus what's left of the stack
        core_expr = [Id] -> Id -> CoreExpr
buildEnvStack [Id]
env_ids' Id
stack_id'
        in_ty = [Id] -> Type -> Type
envStackType [Id]
env_ids Type
stack_ty
        in_ty' = [Id] -> Type -> Type
envStackType [Id]
env_ids' Type
stack_ty'
        lam_cxt = HsArrowMatchContext -> HsMatchContext fn
forall fn. HsArrowMatchContext -> HsMatchContext fn
ArrowMatchCtxt (HsLamVariant -> HsArrowMatchContext
ArrowLamAlt HsLamVariant
LamSingle)

    fail_expr <- mkFailExpr lam_cxt in_ty'
    -- match the patterns against the parameters
    match_code <- matchSimplys (map Var param_ids) lam_cxt pats core_expr
                    fail_expr
    -- match the parameters against the top of the old stack
    (stack_id, param_code) <- matchVarStack param_ids stack_id' match_code
    -- match the old environment and stack against the input
    select_code <- matchEnvStack env_ids stack_id param_code
    return (do_premap ids in_ty in_ty' res_ty select_code core_body,
            free_vars `uniqDSetMinusUniqSet` pat_vars)

-- Used for case and \case(s)
-- See Note [Desugaring HsCmdCase]
dsCases :: DsCmdEnv                               -- arrow combinators
        -> IdSet                                  -- set of local vars available to this command
        -> Id                                     -- stack id
        -> Type                                   -- type of the stack (right-nested tuple)
        -> Type                                   -- return type of the command
        -> MatchGroup GhcTc (LHsCmd GhcTc)        -- match group to desugar
        -> DsM (MatchGroup GhcTc (LHsExpr GhcTc), -- match group with choice tree
                CoreExpr)                         -- desugared choices
dsCases :: DsCmdEnv
-> VarSet
-> Id
-> Type
-> Type
-> MatchGroup
     (GhcPass 'Typechecked) (LHsCmd (GhcPass 'Typechecked))
-> DsM
     (MatchGroup
        (GhcPass 'Typechecked) (LHsExpr (GhcPass 'Typechecked)),
      CoreExpr)
dsCases DsCmdEnv
ids VarSet
local_vars Id
stack_id Type
stack_ty Type
res_ty
        (MG { mg_alts :: forall p body. MatchGroup p body -> XRec p [LMatch p body]
mg_alts = L SrcSpanAnnLW
l [GenLocated
   SrcSpanAnnA
   (Match
      (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked))))]
matches
            , mg_ext :: forall p body. MatchGroup p body -> XMG p body
mg_ext = MatchGroupTc [Scaled Type]
arg_tys Type
_ Origin
origin
            }) = do

  -- Extract and desugar the leaf commands in the case, building tuple
  -- expressions that will (after tagging) replace these leaves

  let leaves :: [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
leaves = (GenLocated
   SrcSpanAnnA
   (Match
      (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked))))
 -> [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)])
-> [GenLocated
      SrcSpanAnnA
      (Match
         (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked))))]
-> [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
forall (t :: * -> *) a b. Foldable t => (a -> [b]) -> t a -> [b]
concatMap LMatch
  (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked)))
-> [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
GenLocated
  SrcSpanAnnA
  (Match
     (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked))))
-> [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
forall (body :: * -> *).
LMatch
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> [(LocatedA (body (GhcPass 'Typechecked)), VarSet)]
leavesMatch [GenLocated
   SrcSpanAnnA
   (Match
      (GhcPass 'Typechecked) (LocatedA (HsCmd (GhcPass 'Typechecked))))]
matches
      make_branch :: (LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
make_branch (LocatedA (HsCmd (GhcPass 'Typechecked))
leaf, VarSet
bound_vars) = do
          (core_leaf, _fvs, leaf_ids)
             <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids (VarSet
bound_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars) Type
stack_ty
                  Type
res_ty LHsCmd (GhcPass 'Typechecked)
LocatedA (HsCmd (GhcPass 'Typechecked))
leaf
          return ([mkHsEnvStackExpr leaf_ids stack_id],
                  envStackType leaf_ids stack_ty,
                  core_leaf)

  branches <- ((LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
       CoreExpr))
-> [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     [([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
       CoreExpr)]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
make_branch [(LocatedA (HsCmd (GhcPass 'Typechecked)), VarSet)]
leaves
  either_con <- dsLookupTyCon eitherTyConName
  left_con <- dsLookupDataCon leftDataConName
  right_con <- dsLookupDataCon rightDataConName
  void_ty <- mkTyConTy <$> dsLookupTyCon voidTyConName
  let
      left_id  = ConLike -> HsExpr (GhcPass 'Typechecked)
mkConLikeTc (DataCon -> ConLike
RealDataCon DataCon
left_con)
      right_id = ConLike -> HsExpr (GhcPass 'Typechecked)
mkConLikeTc (DataCon -> ConLike
RealDataCon DataCon
right_con)
      left_expr  Type
ty1 Type
ty2 GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
e = HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (HsExpr (GhcPass 'Typechecked)
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$ XApp (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
-> HsExpr (GhcPass 'Typechecked)
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp (GhcPass 'Typechecked)
NoExtField
noExtField
                         (HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (HsExpr (GhcPass 'Typechecked)
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$ HsWrapper
-> HsExpr (GhcPass 'Typechecked) -> HsExpr (GhcPass 'Typechecked)
mkHsWrap ([Type] -> HsWrapper
mkWpTyApps [Type
ty1, Type
ty2]) HsExpr (GhcPass 'Typechecked)
left_id ) LHsExpr (GhcPass 'Typechecked)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
e
      right_expr Type
ty1 Type
ty2 GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
e = HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (HsExpr (GhcPass 'Typechecked)
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$ XApp (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
-> LHsExpr (GhcPass 'Typechecked)
-> HsExpr (GhcPass 'Typechecked)
forall p. XApp p -> LHsExpr p -> LHsExpr p -> HsExpr p
HsApp XApp (GhcPass 'Typechecked)
NoExtField
noExtField
                         (HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA (HsExpr (GhcPass 'Typechecked)
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> HsExpr (GhcPass 'Typechecked)
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$ HsWrapper
-> HsExpr (GhcPass 'Typechecked) -> HsExpr (GhcPass 'Typechecked)
mkHsWrap ([Type] -> HsWrapper
mkWpTyApps [Type
ty1, Type
ty2]) HsExpr (GhcPass 'Typechecked)
right_id) LHsExpr (GhcPass 'Typechecked)
GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
e

      -- Prefix each tuple with a distinct series of Left's and Right's,
      -- in a balanced way, keeping track of the types.

      merge_branches :: ([LHsExpr GhcTc], Type, CoreExpr)
                    -> ([LHsExpr GhcTc], Type, CoreExpr)
                    -> ([LHsExpr GhcTc], Type, CoreExpr) -- AZ
      merge_branches ([LHsExpr (GhcPass 'Typechecked)]
builds1, Type
in_ty1, CoreExpr
core_exp1)
                     ([LHsExpr (GhcPass 'Typechecked)]
builds2, Type
in_ty2, CoreExpr
core_exp2)
        = ((GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
forall a b. (a -> b) -> [a] -> [b]
map (Type
-> Type
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
left_expr Type
in_ty1 Type
in_ty2) [LHsExpr (GhcPass 'Typechecked)]
[GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
builds1 [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
forall a. [a] -> [a] -> [a]
++
              (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
 -> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
-> [GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
forall a b. (a -> b) -> [a] -> [b]
map (Type
-> Type
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
-> GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))
right_expr Type
in_ty1 Type
in_ty2) [LHsExpr (GhcPass 'Typechecked)]
[GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))]
builds2,
           TyCon -> [Type] -> Type
mkTyConApp TyCon
either_con [Type
in_ty1, Type
in_ty2],
           DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_choice DsCmdEnv
ids Type
in_ty1 Type
in_ty2 Type
res_ty CoreExpr
core_exp1 CoreExpr
core_exp2)
  (leaves', sum_ty, core_choices) <- case nonEmpty branches of
    Just NonEmpty
  ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
   CoreExpr)
bs -> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
 CoreExpr)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
  CoreExpr)
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
       CoreExpr))
-> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
    CoreExpr)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
forall a b. (a -> b) -> a -> b
$ (([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
  CoreExpr)
 -> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
     CoreExpr)
 -> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
     CoreExpr))
-> NonEmpty
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
-> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
    CoreExpr)
forall a. (a -> a -> a) -> NonEmpty a -> a
foldb ([LHsExpr (GhcPass 'Typechecked)], Type, CoreExpr)
-> ([LHsExpr (GhcPass 'Typechecked)], Type, CoreExpr)
-> ([LHsExpr (GhcPass 'Typechecked)], Type, CoreExpr)
([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
 CoreExpr)
-> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
    CoreExpr)
-> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
    CoreExpr)
merge_branches NonEmpty
  ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
   CoreExpr)
bs
    -- when the case command has no alternatives, the sum type from
    -- Note [Desugaring HsCmdCase] becomes the empty sum type,
    -- i.e. Void. The choices then effectively become `arr absurd`,
    -- implemented as `arr \case {}`.
    Maybe
  (NonEmpty
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr))
Nothing -> ([], Type
void_ty,) (CoreExpr
 -> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
     CoreExpr))
-> (CoreExpr -> CoreExpr)
-> CoreExpr
-> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
    CoreExpr)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr DsCmdEnv
ids Type
void_ty Type
res_ty (CoreExpr
 -> ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
     CoreExpr))
-> DsM CoreExpr
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     ([GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))], Type,
      CoreExpr)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$>
      HsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsExpr (XLam (GhcPass 'Typechecked)
-> HsLamVariant
-> MatchGroup
     (GhcPass 'Typechecked) (LHsExpr (GhcPass 'Typechecked))
-> HsExpr (GhcPass 'Typechecked)
forall p.
XLam p -> HsLamVariant -> MatchGroup p (LHsExpr p) -> HsExpr p
HsLam XLam (GhcPass 'Typechecked)
EpAnnLam
forall a. NoAnn a => a
noAnn HsLamVariant
LamCase
        (MG { mg_alts :: XRec
  (GhcPass 'Typechecked)
  [LMatch
     (GhcPass 'Typechecked)
     (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))]
mg_alts = [GenLocated
   (Anno
      (Match
         (GhcPass 'Typechecked)
         (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))))
   (Match
      (GhcPass 'Typechecked)
      (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))))]
-> GenLocated
     (Anno
        [GenLocated
           (Anno
              (Match
                 (GhcPass 'Typechecked)
                 (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))))
           (Match
              (GhcPass 'Typechecked)
              (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))))])
     [GenLocated
        (Anno
           (Match
              (GhcPass 'Typechecked)
              (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))))
        (Match
           (GhcPass 'Typechecked)
           (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked))))]
forall e a. HasAnnotation e => a -> GenLocated e a
noLocA []
            , mg_ext :: XMG
  (GhcPass 'Typechecked)
  (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))
mg_ext = [Scaled Type] -> Type -> Origin -> MatchGroupTc
MatchGroupTc [Type -> Type -> Scaled Type
forall a. Type -> a -> Scaled a
Scaled Type
ManyTy Type
void_ty] Type
res_ty (GenReason -> DoPmc -> Origin
Generated GenReason
OtherExpansion DoPmc
SkipPmc)
            }))

      -- Replace the commands in the case with these tagged tuples,
      -- yielding a HsExpr Id we can feed to dsExpr.

  let (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches

  -- Note that we replace the MatchGroup result type by sum_ty,
  -- which is the type of matches'
  return (MG { mg_alts = L l matches'
             , mg_ext = MatchGroupTc arg_tys sum_ty origin
             },
          core_choices)

{-
Translation of command judgements of the form

        D |-a do { ss } : t
-}

dsCmdDo :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this statement
        -> Type                 -- return type of the statement
        -> [CmdLStmt GhcTc]     -- statements to desugar
        -> [Id]                 -- list of vars in the input to this statement
                                -- This is typically fed back,
                                -- so don't pull on it too early
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet)         -- subset of local vars that occur free

dsCmdDo :: DsCmdEnv
-> VarSet
-> Type
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdDo DsCmdEnv
_ VarSet
_ Type
_ [] [Id]
_ = String -> DsM (CoreExpr, DIdSet)
forall a. HasCallStack => String -> a
panic String
"dsCmdDo"

-- D; xs |-a c : () --> t
-- --------------------------
-- D; xs |-a do { c } : t
--
--              ---> premap (\ (xs) -> ((xs), ())) c

dsCmdDo DsCmdEnv
ids VarSet
local_vars Type
res_ty [L SrcSpanAnnA
_ (LastStmt XLastStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LocatedA (HsCmd (GhcPass 'Typechecked)))
_ LocatedA (HsCmd (GhcPass 'Typechecked))
body Maybe Bool
_ SyntaxExpr (GhcPass 'Typechecked)
_)] [Id]
env_ids = do
    (core_body, env_ids') <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsLCmd DsCmdEnv
ids VarSet
local_vars Type
unitTy Type
res_ty LHsCmd (GhcPass 'Typechecked)
LocatedA (HsCmd (GhcPass 'Typechecked))
body [Id]
env_ids
    let env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
    env_var <- newSysLocalMDs env_ty
    let core_map = Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
env_var (CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
env_var) CoreExpr
mkCoreUnitExpr)
    return (do_premap ids
                        env_ty
                        (mkCorePairTy env_ty unitTy)
                        res_ty
                        core_map
                        core_body,
        env_ids')

dsCmdDo DsCmdEnv
ids VarSet
local_vars Type
res_ty (CmdLStmt (GhcPass 'Typechecked)
stmt:[CmdLStmt (GhcPass 'Typechecked)]
stmts) [Id]
env_ids = do
    let bound_vars :: VarSet
bound_vars  = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> LStmtLR
     (GhcPass 'Typechecked)
     (GhcPass 'Typechecked)
     (LocatedA (HsCmd (GhcPass 'Typechecked)))
-> [IdP (GhcPass 'Typechecked)]
forall (idL :: Pass) (idR :: Pass) body.
(IsPass idL, IsPass idR, CollectPass (GhcPass idL)) =>
CollectFlag (GhcPass idL)
-> LStmtLR (GhcPass idL) (GhcPass idR) body -> [IdP (GhcPass idL)]
collectLStmtBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders CmdLStmt (GhcPass 'Typechecked)
LStmtLR
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LocatedA (HsCmd (GhcPass 'Typechecked)))
stmt)
    let local_vars' :: VarSet
local_vars' = VarSet
bound_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars
    (core_stmts, _, env_ids') <- ([Id] -> DsM (CoreExpr, DIdSet)) -> DsM (CoreExpr, DIdSet, [Id])
trimInput (DsCmdEnv
-> VarSet
-> Type
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdDo DsCmdEnv
ids VarSet
local_vars' Type
res_ty [CmdLStmt (GhcPass 'Typechecked)]
stmts)
    (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids' stmt env_ids
    return (do_compose ids
                (mkBigCoreVarTupTy env_ids)
                (mkBigCoreVarTupTy env_ids')
                res_ty
                core_stmt
                core_stmts,
              fv_stmt)

{-
A statement maps one local environment to another, and is represented
as an arrow from one tuple type to another.  A statement sequence is
translated to a composition of such arrows.
-}

dsCmdLStmt :: DsCmdEnv -> IdSet -> [Id] -> CmdLStmt GhcTc -> [Id]
           -> DsM (CoreExpr, DIdSet)
dsCmdLStmt :: DsCmdEnv
-> VarSet
-> [Id]
-> CmdLStmt (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdLStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids CmdLStmt (GhcPass 'Typechecked)
cmd [Id]
env_ids
  = DsCmdEnv
-> VarSet
-> [Id]
-> CmdStmt (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids (GenLocated
  SrcSpanAnnA
  (StmtLR
     (GhcPass 'Typechecked)
     (GhcPass 'Typechecked)
     (LocatedA (HsCmd (GhcPass 'Typechecked))))
-> StmtLR
     (GhcPass 'Typechecked)
     (GhcPass 'Typechecked)
     (LocatedA (HsCmd (GhcPass 'Typechecked)))
forall l e. GenLocated l e -> e
unLoc CmdLStmt (GhcPass 'Typechecked)
GenLocated
  SrcSpanAnnA
  (StmtLR
     (GhcPass 'Typechecked)
     (GhcPass 'Typechecked)
     (LocatedA (HsCmd (GhcPass 'Typechecked))))
cmd) [Id]
env_ids

dsCmdStmt
        :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this statement
        -> [Id]                 -- list of vars in the output of this statement
        -> CmdStmt GhcTc        -- statement to desugar
        -> [Id]                 -- list of vars in the input to this statement
                                -- This is typically fed back,
                                -- so don't pull on it too early
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet)         -- subset of local vars that occur free

-- D; xs1 |-a c : () --> t
-- D; xs' |-a do { ss } : t'
-- ------------------------------
-- D; xs  |-a do { c; ss } : t'
--
--              ---> premap (\ ((xs)) -> (((xs1),()),(xs')))
--                      (first c >>> arr snd) >>> ss

dsCmdStmt :: DsCmdEnv
-> VarSet
-> [Id]
-> CmdStmt (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids (BodyStmt XBodyStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LHsCmd (GhcPass 'Typechecked))
c_ty LHsCmd (GhcPass 'Typechecked)
cmd SyntaxExpr (GhcPass 'Typechecked)
_ SyntaxExpr (GhcPass 'Typechecked)
_) [Id]
env_ids = do
    (core_cmd, fv_cmd, env_ids1) <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids VarSet
local_vars Type
unitTy XBodyStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LHsCmd (GhcPass 'Typechecked))
Type
c_ty LHsCmd (GhcPass 'Typechecked)
cmd
    core_mux <- matchEnv env_ids
        (mkCorePairExpr
            (mkCorePairExpr (mkBigCoreVarTup env_ids1) mkCoreUnitExpr)
            (mkBigCoreVarTup out_ids))
    let
        in_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
        in_ty1 = Type -> Type -> Type
mkCorePairTy ([Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids1) Type
unitTy
        out_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
out_ids
        before_c_ty = Type -> Type -> Type
mkCorePairTy Type
in_ty1 Type
out_ty
        after_c_ty = Type -> Type -> Type
mkCorePairTy XBodyStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LHsCmd (GhcPass 'Typechecked))
Type
c_ty Type
out_ty
    snd_fn <- mkSndExpr c_ty out_ty
    return (do_premap ids in_ty before_c_ty out_ty core_mux $
                do_compose ids before_c_ty after_c_ty out_ty
                        (do_first ids in_ty1 c_ty out_ty core_cmd) $
                do_arr ids after_c_ty out_ty snd_fn,
              extendDVarSetList fv_cmd out_ids)

-- D; xs1 |-a c : () --> t
-- D; xs' |-a do { ss } : t'            xs2 = xs' - defs(p)
-- -----------------------------------
-- D; xs  |-a do { p <- c; ss } : t'
--
--              ---> premap (\ (xs) -> (((xs1),()),(xs2)))
--                      (first c >>> arr (\ (p, (xs2)) -> (xs'))) >>> ss
--
-- It would be simpler and more consistent to do this using second,
-- but that's likely to be defined in terms of first.

dsCmdStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids (BindStmt XBindStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LHsCmd (GhcPass 'Typechecked))
_ LPat (GhcPass 'Typechecked)
pat LHsCmd (GhcPass 'Typechecked)
cmd) [Id]
env_ids = do
    let pat_ty :: Type
pat_ty = LPat (GhcPass 'Typechecked) -> Type
hsLPatType LPat (GhcPass 'Typechecked)
pat
    (core_cmd, fv_cmd, env_ids1) <- DsCmdEnv
-> VarSet
-> Type
-> Type
-> LHsCmd (GhcPass 'Typechecked)
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmd DsCmdEnv
ids VarSet
local_vars Type
unitTy Type
pat_ty LHsCmd (GhcPass 'Typechecked)
cmd
    let pat_vars = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> LPat (GhcPass 'Typechecked) -> [IdP (GhcPass 'Typechecked)]
forall p. CollectPass p => CollectFlag p -> LPat p -> [IdP p]
collectPatBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders LPat (GhcPass 'Typechecked)
pat)
    let
        env_ids2 = (Id -> Bool) -> [Id] -> [Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut (Id -> VarSet -> Bool
`elemVarSet` VarSet
pat_vars) [Id]
out_ids
        env_ty2 = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids2

    -- multiplexing function
    --          \ (xs) -> (((xs1),()),(xs2))

    core_mux <- matchEnv env_ids
        (mkCorePairExpr
            (mkCorePairExpr (mkBigCoreVarTup env_ids1) mkCoreUnitExpr)
            (mkBigCoreVarTup env_ids2))

    -- projection function
    --          \ (p, (xs2)) -> (zs)

    env_id <- newSysLocalMDs env_ty2
    let
       after_c_ty = Type -> Type -> Type
mkCorePairTy Type
pat_ty Type
env_ty2
       out_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
out_ids
    body_expr <- coreCaseTuple env_id env_ids2 (mkBigCoreVarTup out_ids)

    fail_expr <- mkFailExpr (StmtCtxt (HsDoStmt (DoExpr Nothing))) out_ty
    pat_id    <- selectSimpleMatchVarL ManyTy pat
    match_code
      <- matchSimply (Var pat_id) (StmtCtxt (HsDoStmt (DoExpr Nothing))) ManyTy pat body_expr fail_expr
    pair_id   <- newSysLocalMDs after_c_ty
    let
        proj_expr = Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
pair_id (Id -> Id -> Id -> CoreExpr -> CoreExpr
coreCasePair Id
pair_id Id
pat_id Id
env_id CoreExpr
match_code)

    -- put it all together
    let
        in_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
        in_ty1 = Type -> Type -> Type
mkCorePairTy ([Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids1) Type
unitTy
        in_ty2 = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids2
        before_c_ty = Type -> Type -> Type
mkCorePairTy Type
in_ty1 Type
in_ty2
    return (do_premap ids in_ty before_c_ty out_ty core_mux $
                do_compose ids before_c_ty after_c_ty out_ty
                        (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
                do_arr ids after_c_ty out_ty proj_expr,
              fv_cmd `unionDVarSet` (mkDVarSet out_ids
                                     `uniqDSetMinusUniqSet` pat_vars))

-- D; xs' |-a do { ss } : t
-- --------------------------------------
-- D; xs  |-a do { let binds; ss } : t
--
--              ---> arr (\ (xs) -> let binds in (xs')) >>> ss

dsCmdStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids (LetStmt XLetStmt
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LHsCmd (GhcPass 'Typechecked))
_ HsLocalBinds (GhcPass 'Typechecked)
binds) [Id]
env_ids = do
    -- build a new environment using the let bindings
    core_binds <- HsLocalBinds (GhcPass 'Typechecked) -> CoreExpr -> DsM CoreExpr
dsLocalBinds HsLocalBinds (GhcPass 'Typechecked)
binds ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
out_ids)
    -- match the old environment against the input
    core_map <- matchEnv env_ids core_binds
    return (do_arr ids
                        (mkBigCoreVarTupTy env_ids)
                        (mkBigCoreVarTupTy out_ids)
                        core_map,
            exprFreeIdsDSet core_binds `uniqDSetIntersectUniqSet` local_vars)

-- D; ys  |-a do { ss; returnA -< ((xs1), (ys2)) } : ...
-- D; xs' |-a do { ss' } : t
-- ------------------------------------
-- D; xs  |-a do { rec ss; ss' } : t
--
--                      xs1 = xs' /\ defs(ss)
--                      xs2 = xs' - defs(ss)
--                      ys1 = ys - defs(ss)
--                      ys2 = ys /\ defs(ss)
--
--              ---> arr (\(xs) -> ((ys1),(xs2))) >>>
--                      first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
--                      arr (\((xs1),(xs2)) -> (xs')) >>> ss'

dsCmdStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids
        (RecStmt { recS_stmts :: forall idL idR body.
StmtLR idL idR body -> XRec idR [LStmtLR idL idR body]
recS_stmts = L SrcSpanAnnLW
_ [GenLocated
   SrcSpanAnnA
   (StmtLR
      (GhcPass 'Typechecked)
      (GhcPass 'Typechecked)
      (LocatedA (HsCmd (GhcPass 'Typechecked))))]
stmts
                 , recS_later_ids :: forall idL idR body. StmtLR idL idR body -> [IdP idR]
recS_later_ids = [IdP (GhcPass 'Typechecked)]
later_ids, recS_rec_ids :: forall idL idR body. StmtLR idL idR body -> [IdP idR]
recS_rec_ids = [IdP (GhcPass 'Typechecked)]
rec_ids
                 , recS_ext :: forall idL idR body. StmtLR idL idR body -> XRecStmt idL idR body
recS_ext = RecStmtTc { recS_later_rets :: RecStmtTc -> [HsExpr (GhcPass 'Typechecked)]
recS_later_rets = [HsExpr (GhcPass 'Typechecked)]
later_rets
                                        , recS_rec_rets :: RecStmtTc -> [HsExpr (GhcPass 'Typechecked)]
recS_rec_rets = [HsExpr (GhcPass 'Typechecked)]
rec_rets } })
        [Id]
env_ids = do
    let
        later_ids_set :: VarSet
later_ids_set = [Id] -> VarSet
mkVarSet [IdP (GhcPass 'Typechecked)]
[Id]
later_ids
        env2_ids :: [Id]
env2_ids = (Id -> Bool) -> [Id] -> [Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut (Id -> VarSet -> Bool
`elemVarSet` VarSet
later_ids_set) [Id]
out_ids
        env2_id_set :: DIdSet
env2_id_set = [Id] -> DIdSet
mkDVarSet [Id]
env2_ids
        env2_ty :: Type
env2_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env2_ids

    -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)

    env2_id <- Type -> DsM Id
newSysLocalMDs Type
env2_ty
    let
        later_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [IdP (GhcPass 'Typechecked)]
[Id]
later_ids
        post_pair_ty = Type -> Type -> Type
mkCorePairTy Type
later_ty Type
env2_ty
    post_loop_body <- coreCaseTuple env2_id env2_ids (mkBigCoreVarTup out_ids)

    post_loop_fn <- matchEnvStack later_ids env2_id post_loop_body

    --- loop (...)

    (core_loop, env1_id_set, env1_ids)
               <- dsRecCmd ids local_vars stmts later_ids later_rets rec_ids rec_rets

    -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))

    let
        env1_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env1_ids
        pre_pair_ty = Type -> Type -> Type
mkCorePairTy Type
env1_ty Type
env2_ty
        pre_loop_body = CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
env1_ids)
                                        ([Id] -> CoreExpr
mkBigCoreVarTup [Id]
env2_ids)

    pre_loop_fn <- matchEnv env_ids pre_loop_body

    -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn

    let
        env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
        out_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
out_ids
        core_body = DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_premap DsCmdEnv
ids Type
env_ty Type
pre_pair_ty Type
out_ty
                CoreExpr
pre_loop_fn
                (DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_compose DsCmdEnv
ids Type
pre_pair_ty Type
post_pair_ty Type
out_ty
                        (DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_first DsCmdEnv
ids Type
env1_ty Type
later_ty Type
env2_ty
                                CoreExpr
core_loop)
                        (DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr DsCmdEnv
ids Type
post_pair_ty Type
out_ty
                                CoreExpr
post_loop_fn))

    return (core_body, env1_id_set `unionDVarSet` env2_id_set)

dsCmdStmt DsCmdEnv
_ VarSet
_ [Id]
_ CmdStmt (GhcPass 'Typechecked)
_ [Id]
s = String -> SDoc -> DsM (CoreExpr, DIdSet)
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"dsCmdStmt" ([Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
s)

--      loop (premap (\ ((env1_ids), ~(rec_ids)) -> (env_ids))
--            (ss >>> arr (\ (out_ids) -> ((later_rets),(rec_rets))))) >>>

dsRecCmd
        :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this statement
        -> [CmdLStmt GhcTc]     -- list of statements inside the RecCmd
        -> [Id]                 -- list of vars defined here and used later
        -> [HsExpr GhcTc]       -- expressions corresponding to later_ids
        -> [Id]                 -- list of vars fed back through the loop
        -> [HsExpr GhcTc]       -- expressions corresponding to rec_ids
        -> DsM (CoreExpr,       -- desugared statement
                DIdSet,         -- subset of local vars that occur free
                [Id])           -- same local vars as a list

dsRecCmd :: DsCmdEnv
-> VarSet
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> [HsExpr (GhcPass 'Typechecked)]
-> [Id]
-> [HsExpr (GhcPass 'Typechecked)]
-> DsM (CoreExpr, DIdSet, [Id])
dsRecCmd DsCmdEnv
ids VarSet
local_vars [CmdLStmt (GhcPass 'Typechecked)]
stmts [Id]
later_ids [HsExpr (GhcPass 'Typechecked)]
later_rets [Id]
rec_ids [HsExpr (GhcPass 'Typechecked)]
rec_rets = do
    let
        later_id_set :: VarSet
later_id_set = [Id] -> VarSet
mkVarSet [Id]
later_ids
        rec_id_set :: VarSet
rec_id_set = [Id] -> VarSet
mkVarSet [Id]
rec_ids
        local_vars' :: VarSet
local_vars' = VarSet
rec_id_set VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
later_id_set VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars

    -- mk_pair_fn = \ (out_ids) -> ((later_rets),(rec_rets))

    core_later_rets <- (HsExpr (GhcPass 'Typechecked) -> DsM CoreExpr)
-> [HsExpr (GhcPass 'Typechecked)]
-> IOEnv (Env DsGblEnv DsLclEnv) [CoreExpr]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM HsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsExpr [HsExpr (GhcPass 'Typechecked)]
later_rets
    core_rec_rets <- mapM dsExpr rec_rets
    let
        -- possibly polymorphic version of vars of later_ids and rec_ids
        out_ids = [CoreExpr] -> [Id]
exprsFreeIdsList ([CoreExpr]
core_later_rets [CoreExpr] -> [CoreExpr] -> [CoreExpr]
forall a. [a] -> [a] -> [a]
++ [CoreExpr]
core_rec_rets)
        out_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
out_ids

        later_tuple = [CoreExpr] -> CoreExpr
mkBigCoreTup [CoreExpr]
core_later_rets
        later_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
later_ids

        rec_tuple = [CoreExpr] -> CoreExpr
mkBigCoreTup [CoreExpr]
core_rec_rets
        rec_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
rec_ids

        out_pair = CoreExpr -> CoreExpr -> CoreExpr
mkCorePairExpr CoreExpr
later_tuple CoreExpr
rec_tuple
        out_pair_ty = Type -> Type -> Type
mkCorePairTy Type
later_ty Type
rec_ty

    mk_pair_fn <- matchEnv out_ids out_pair

    -- ss

    (core_stmts, fv_stmts, env_ids) <- dsfixCmdStmts ids local_vars' out_ids stmts

    -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)

    rec_id <- newSysLocalMDs rec_ty
    let
        env1_id_set = DIdSet
fv_stmts DIdSet -> VarSet -> DIdSet
forall a. UniqDSet a -> UniqSet a -> UniqDSet a
`uniqDSetMinusUniqSet` VarSet
rec_id_set
        env1_ids = DIdSet -> [Id]
dVarSetElems DIdSet
env1_id_set
        env1_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env1_ids
        in_pair_ty = Type -> Type -> Type
mkCorePairTy Type
env1_ty Type
rec_ty
        core_body = [CoreExpr] -> CoreExpr
mkBigCoreTup ((Id -> CoreExpr) -> [Id] -> [CoreExpr]
forall a b. (a -> b) -> [a] -> [b]
map Id -> CoreExpr
selectVar [Id]
env_ids)
          where
            selectVar :: Id -> CoreExpr
selectVar Id
v
                | Id
v Id -> VarSet -> Bool
`elemVarSet` VarSet
rec_id_set
                  = [Id] -> Id -> Id -> CoreExpr -> CoreExpr
mkBigTupleSelector [Id]
rec_ids Id
v Id
rec_id (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
rec_id)
                | Bool
otherwise = Id -> CoreExpr
forall b. Id -> Expr b
Var Id
v

    squash_pair_fn <- matchEnvStack env1_ids rec_id core_body

    -- loop (premap squash_pair_fn (ss >>> arr mk_pair_fn))

    let
        env_ty = [Id] -> Type
HasDebugCallStack => [Id] -> Type
mkBigCoreVarTupTy [Id]
env_ids
        core_loop = DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
do_loop DsCmdEnv
ids Type
env1_ty Type
later_ty Type
rec_ty
                (DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_premap DsCmdEnv
ids Type
in_pair_ty Type
env_ty Type
out_pair_ty
                        CoreExpr
squash_pair_fn
                        (DsCmdEnv
-> Type -> Type -> Type -> CoreExpr -> CoreExpr -> CoreExpr
do_compose DsCmdEnv
ids Type
env_ty Type
out_ty Type
out_pair_ty
                                CoreExpr
core_stmts
                                (DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
do_arr DsCmdEnv
ids Type
out_ty Type
out_pair_ty CoreExpr
mk_pair_fn)))

    return (core_loop, env1_id_set, env1_ids)

{-
A sequence of statements (as in a rec) is desugared to an arrow between
two environments (no stack)
-}

dsfixCmdStmts
        :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this statement
        -> [Id]                 -- output vars of these statements
        -> [CmdLStmt GhcTc]     -- statements to desugar
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet,         -- subset of local vars that occur free
                [Id])           -- same local vars as a list

dsfixCmdStmts :: DsCmdEnv
-> VarSet
-> [Id]
-> [CmdLStmt (GhcPass 'Typechecked)]
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmdStmts DsCmdEnv
ids VarSet
local_vars [Id]
out_ids [CmdLStmt (GhcPass 'Typechecked)]
stmts
  = ([Id] -> DsM (CoreExpr, DIdSet)) -> DsM (CoreExpr, DIdSet, [Id])
trimInput (DsCmdEnv
-> VarSet
-> [Id]
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdStmts DsCmdEnv
ids VarSet
local_vars [Id]
out_ids [CmdLStmt (GhcPass 'Typechecked)]
stmts)
   -- TODO: Add representation polymorphism check for the resulting expression.
   -- But I (Richard E.) don't know enough about arrows to do so.

dsCmdStmts
        :: DsCmdEnv             -- arrow combinators
        -> IdSet                -- set of local vars available to this statement
        -> [Id]                 -- output vars of these statements
        -> [CmdLStmt GhcTc]     -- statements to desugar
        -> [Id]                 -- list of vars in the input to these statements
        -> DsM (CoreExpr,       -- desugared expression
                DIdSet)         -- subset of local vars that occur free

dsCmdStmts :: DsCmdEnv
-> VarSet
-> [Id]
-> [CmdLStmt (GhcPass 'Typechecked)]
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdStmts DsCmdEnv
ids VarSet
local_vars [Id]
out_ids [CmdLStmt (GhcPass 'Typechecked)
stmt] [Id]
env_ids
  = DsCmdEnv
-> VarSet
-> [Id]
-> CmdLStmt (GhcPass 'Typechecked)
-> [Id]
-> DsM (CoreExpr, DIdSet)
dsCmdLStmt DsCmdEnv
ids VarSet
local_vars [Id]
out_ids CmdLStmt (GhcPass 'Typechecked)
stmt [Id]
env_ids

dsCmdStmts DsCmdEnv
ids VarSet
local_vars [Id]
out_ids (CmdLStmt (GhcPass 'Typechecked)
stmt:[CmdLStmt (GhcPass 'Typechecked)]
stmts) [Id]
env_ids = do
    let bound_vars :: VarSet
bound_vars  = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> LStmtLR
     (GhcPass 'Typechecked)
     (GhcPass 'Typechecked)
     (LocatedA (HsCmd (GhcPass 'Typechecked)))
-> [IdP (GhcPass 'Typechecked)]
forall (idL :: Pass) (idR :: Pass) body.
(IsPass idL, IsPass idR, CollectPass (GhcPass idL)) =>
CollectFlag (GhcPass idL)
-> LStmtLR (GhcPass idL) (GhcPass idR) body -> [IdP (GhcPass idL)]
collectLStmtBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders CmdLStmt (GhcPass 'Typechecked)
LStmtLR
  (GhcPass 'Typechecked)
  (GhcPass 'Typechecked)
  (LocatedA (HsCmd (GhcPass 'Typechecked)))
stmt)
    let local_vars' :: VarSet
local_vars' = VarSet
bound_vars VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
local_vars
    (core_stmts, _fv_stmts, env_ids') <- DsCmdEnv
-> VarSet
-> [Id]
-> [CmdLStmt (GhcPass 'Typechecked)]
-> DsM (CoreExpr, DIdSet, [Id])
dsfixCmdStmts DsCmdEnv
ids VarSet
local_vars' [Id]
out_ids [CmdLStmt (GhcPass 'Typechecked)]
stmts
    (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids' stmt env_ids
    return (do_compose ids
                (mkBigCoreVarTupTy env_ids)
                (mkBigCoreVarTupTy env_ids')
                (mkBigCoreVarTupTy out_ids)
                core_stmt
                core_stmts,
              fv_stmt)

dsCmdStmts DsCmdEnv
_ VarSet
_ [Id]
_ [] [Id]
_ = String -> DsM (CoreExpr, DIdSet)
forall a. HasCallStack => String -> a
panic String
"dsCmdStmts []"

-- Match a list of expressions against a list of patterns, left-to-right.

matchSimplys :: [CoreExpr]              -- Scrutinees
             -> HsMatchContextRn        -- Match kind
             -> [LPat GhcTc]            -- Patterns they should match
             -> CoreExpr                -- Return this if they all match
             -> CoreExpr                -- Return this if they don't
             -> DsM CoreExpr
matchSimplys :: [CoreExpr]
-> HsMatchContextRn
-> [LPat (GhcPass 'Typechecked)]
-> CoreExpr
-> CoreExpr
-> DsM CoreExpr
matchSimplys [] HsMatchContextRn
_ctxt [] CoreExpr
result_expr CoreExpr
_fail_expr = CoreExpr -> DsM CoreExpr
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
result_expr
matchSimplys (CoreExpr
exp:[CoreExpr]
exps) HsMatchContextRn
ctxt (LPat (GhcPass 'Typechecked)
pat:[LPat (GhcPass 'Typechecked)]
pats) CoreExpr
result_expr CoreExpr
fail_expr = do
    match_code <- [CoreExpr]
-> HsMatchContextRn
-> [LPat (GhcPass 'Typechecked)]
-> CoreExpr
-> CoreExpr
-> DsM CoreExpr
matchSimplys [CoreExpr]
exps HsMatchContextRn
ctxt [LPat (GhcPass 'Typechecked)]
pats CoreExpr
result_expr CoreExpr
fail_expr
    matchSimply exp ctxt ManyTy pat match_code fail_expr
matchSimplys [CoreExpr]
_ HsMatchContextRn
_ [LPat (GhcPass 'Typechecked)]
_ CoreExpr
_ CoreExpr
_ = String -> DsM CoreExpr
forall a. HasCallStack => String -> a
panic String
"matchSimplys"

-- List of leaf expressions, with set of variables bound in each

leavesMatch :: LMatch GhcTc (LocatedA (body GhcTc))
            -> [(LocatedA (body GhcTc), IdSet)]
leavesMatch :: forall (body :: * -> *).
LMatch
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> [(LocatedA (body (GhcPass 'Typechecked)), VarSet)]
leavesMatch (L Anno
  (Match
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
_ (Match { m_pats :: forall p body. Match p body -> XRec p [LPat p]
m_pats = L EpaLocation
_ [GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))]
pats
                        , m_grhss :: forall p body. Match p body -> GRHSs p body
m_grhss = GRHSs XCGRHSs
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
_ [LGRHS
   (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))]
grhss HsLocalBinds (GhcPass 'Typechecked)
binds }))
  = let
        defined_vars :: VarSet
defined_vars = [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> [LPat (GhcPass 'Typechecked)] -> [IdP (GhcPass 'Typechecked)]
forall p. CollectPass p => CollectFlag p -> [LPat p] -> [IdP p]
collectPatsBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders [LPat (GhcPass 'Typechecked)]
[GenLocated SrcSpanAnnA (Pat (GhcPass 'Typechecked))]
pats)
                        VarSet -> VarSet -> VarSet
`unionVarSet`
                       [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> HsLocalBinds (GhcPass 'Typechecked)
-> [IdP (GhcPass 'Typechecked)]
forall (idL :: Pass) (idR :: Pass).
CollectPass (GhcPass idL) =>
CollectFlag (GhcPass idL)
-> HsLocalBindsLR (GhcPass idL) (GhcPass idR)
-> [IdP (GhcPass idL)]
collectLocalBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders HsLocalBinds (GhcPass 'Typechecked)
binds)
    in
    [(LocatedA (body (GhcPass 'Typechecked))
body,
      [Id] -> VarSet
mkVarSet (CollectFlag (GhcPass 'Typechecked)
-> [LStmtLR
      (GhcPass 'Typechecked)
      (GhcPass 'Typechecked)
      (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))]
-> [IdP (GhcPass 'Typechecked)]
forall (idL :: Pass) (idR :: Pass) body.
(IsPass idL, IsPass idR, CollectPass (GhcPass idL)) =>
CollectFlag (GhcPass idL)
-> [LStmtLR (GhcPass idL) (GhcPass idR) body]
-> [IdP (GhcPass idL)]
collectLStmtsBinders CollectFlag (GhcPass 'Typechecked)
CollWithDictBinders [GuardLStmt (GhcPass 'Typechecked)]
[LStmtLR
   (GhcPass 'Typechecked)
   (GhcPass 'Typechecked)
   (GenLocated SrcSpanAnnA (HsExpr (GhcPass 'Typechecked)))]
stmts)
        VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
defined_vars)
    | L Anno
  (GRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
_ (GRHS XCGRHS
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
_ [GuardLStmt (GhcPass 'Typechecked)]
stmts LocatedA (body (GhcPass 'Typechecked))
body) <- [LGRHS
   (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))]
[GenLocated
   (Anno
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))]
grhss]

-- Replace the leaf commands in a match

replaceLeavesMatch
        :: ( Anno (Match GhcTc (LocatedA (body' GhcTc))) ~ Anno (Match GhcTc (LocatedA (body GhcTc)))
           , Anno (GRHS GhcTc (LocatedA (body' GhcTc))) ~ Anno (GRHS GhcTc (LocatedA (body GhcTc))))
        => Type                                 -- new result type
        -> [LocatedA (body' GhcTc)] -- replacement leaf expressions of that type
        -> LMatch GhcTc (LocatedA (body GhcTc))  -- the matches of a case command
        -> ([LocatedA (body' GhcTc)],            -- remaining leaf expressions
            LMatch GhcTc (LocatedA (body' GhcTc))) -- updated match
replaceLeavesMatch :: forall (body' :: * -> *) (body :: * -> *).
(Anno
   (Match
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (Match
        (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))),
 Anno
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (GRHS
        (GhcPass 'Typechecked)
        (LocatedA (body (GhcPass 'Typechecked))))) =>
Type
-> [LocatedA (body' (GhcPass 'Typechecked))]
-> LMatch
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    LMatch
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
replaceLeavesMatch Type
_res_ty [LocatedA (body' (GhcPass 'Typechecked))]
leaves
                        (L Anno
  (Match
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
loc
                          match :: Match
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
match@(Match { m_grhss :: forall p body. Match p body -> GRHSs p body
m_grhss = GRHSs XCGRHSs
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
x [LGRHS
   (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))]
grhss HsLocalBinds (GhcPass 'Typechecked)
binds }))
  = let
        ([LocatedA (body' (GhcPass 'Typechecked))]
leaves', [GenLocated
   (Anno
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))]
grhss') = ([LocatedA (body' (GhcPass 'Typechecked))]
 -> GenLocated
      (Anno
         (GRHS
            (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
 -> ([LocatedA (body' (GhcPass 'Typechecked))],
     GenLocated
       (Anno
          (GRHS
             (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
       (GRHS
          (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))))
-> [LocatedA (body' (GhcPass 'Typechecked))]
-> [GenLocated
      (Anno
         (GRHS
            (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))]
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    [GenLocated
       (Anno
          (GRHS
             (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
       (GRHS
          (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL [LocatedA (body' (GhcPass 'Typechecked))]
-> LGRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    LGRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
[LocatedA (body' (GhcPass 'Typechecked))]
-> GenLocated
     (Anno
        (GRHS
           (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
     (GRHS
        (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    GenLocated
      (Anno
         (GRHS
            (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))))
forall (body' :: * -> *) (body :: * -> *).
(Anno
   (Match
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (Match
        (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))),
 Anno
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (GRHS
        (GhcPass 'Typechecked)
        (LocatedA (body (GhcPass 'Typechecked))))) =>
[LocatedA (body' (GhcPass 'Typechecked))]
-> LGRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    LGRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
replaceLeavesGRHS [LocatedA (body' (GhcPass 'Typechecked))]
leaves [LGRHS
   (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))]
[GenLocated
   (Anno
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))]
grhss
    in
    ([LocatedA (body' (GhcPass 'Typechecked))]
leaves', Anno
  (Match
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
-> Match
     (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))
-> GenLocated
     (Anno
        (Match
           (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
     (Match
        (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
forall l e. l -> e -> GenLocated l e
L Anno
  (Match
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
loc (Match
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
match { m_ext = noExtField, m_grhss = GRHSs x grhss' binds }))

replaceLeavesGRHS
        :: ( Anno (Match GhcTc (LocatedA (body' GhcTc))) ~ Anno (Match GhcTc (LocatedA (body GhcTc)))
           , Anno (GRHS GhcTc (LocatedA (body' GhcTc))) ~ Anno (GRHS GhcTc (LocatedA (body GhcTc))))
        => [LocatedA (body' GhcTc)]  -- replacement leaf expressions of that type
        -> LGRHS GhcTc (LocatedA (body GhcTc))     -- rhss of a case command
        -> ([LocatedA (body' GhcTc)],              -- remaining leaf expressions
            LGRHS GhcTc (LocatedA (body' GhcTc)))  -- updated GRHS
replaceLeavesGRHS :: forall (body' :: * -> *) (body :: * -> *).
(Anno
   (Match
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (Match
        (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))),
 Anno
   (GRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
 ~ Anno
     (GRHS
        (GhcPass 'Typechecked)
        (LocatedA (body (GhcPass 'Typechecked))))) =>
[LocatedA (body' (GhcPass 'Typechecked))]
-> LGRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    LGRHS
      (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
replaceLeavesGRHS (LocatedA (body' (GhcPass 'Typechecked))
leaf:[LocatedA (body' (GhcPass 'Typechecked))]
leaves) (L Anno
  (GRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
loc (GRHS XCGRHS
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
x [GuardLStmt (GhcPass 'Typechecked)]
stmts LocatedA (body (GhcPass 'Typechecked))
_))
  = ([LocatedA (body' (GhcPass 'Typechecked))]
leaves, Anno
  (GRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
-> GRHS
     (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))
-> GenLocated
     (Anno
        (GRHS
           (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
     (GRHS
        (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked))))
forall l e. l -> e -> GenLocated l e
L Anno
  (GRHS
     (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked))))
loc (XCGRHS
  (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))
-> [GuardLStmt (GhcPass 'Typechecked)]
-> LocatedA (body' (GhcPass 'Typechecked))
-> GRHS
     (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))
forall p body.
XCGRHS p body -> [GuardLStmt p] -> body -> GRHS p body
GRHS XCGRHS
  (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))
XCGRHS
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
x [GuardLStmt (GhcPass 'Typechecked)]
stmts LocatedA (body' (GhcPass 'Typechecked))
leaf))
replaceLeavesGRHS [] LGRHS
  (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))
_ = String
-> ([LocatedA (body' (GhcPass 'Typechecked))],
    GenLocated
      (Anno
         (GRHS
            (GhcPass 'Typechecked) (LocatedA (body (GhcPass 'Typechecked)))))
      (GRHS
         (GhcPass 'Typechecked) (LocatedA (body' (GhcPass 'Typechecked)))))
forall a. HasCallStack => String -> a
panic String
"replaceLeavesGRHS []"

-- Balanced fold of a non-empty list.

foldb :: (a -> a -> a) -> NonEmpty a -> a
foldb :: forall a. (a -> a -> a) -> NonEmpty a -> a
foldb a -> a -> a
_ (a
x:|[]) = a
x
foldb a -> a -> a
f NonEmpty a
xs = (a -> a -> a) -> NonEmpty a -> a
forall a. (a -> a -> a) -> NonEmpty a -> a
foldb a -> a -> a
f (NonEmpty a -> NonEmpty a
fold_pairs NonEmpty a
xs)
  where
    fold_pairs :: NonEmpty a -> NonEmpty a
fold_pairs (a
x1:|a
x2:[a]
xs) = a -> a -> a
f a
x1 a
x2 a -> [a] -> NonEmpty a
forall a. a -> [a] -> NonEmpty a
:| (NonEmpty a -> NonEmpty a) -> [a] -> [a]
forall a. (NonEmpty a -> NonEmpty a) -> [a] -> [a]
keep_empty NonEmpty a -> NonEmpty a
fold_pairs [a]
xs
    fold_pairs NonEmpty a
xs          = NonEmpty a
xs

    keep_empty :: (NonEmpty a -> NonEmpty a) -> [a] -> [a]
    keep_empty :: forall a. (NonEmpty a -> NonEmpty a) -> [a] -> [a]
keep_empty NonEmpty a -> NonEmpty a
f = [a] -> (NonEmpty a -> [a]) -> Maybe (NonEmpty a) -> [a]
forall b a. b -> (a -> b) -> Maybe a -> b
maybe [] (NonEmpty a -> [a]
forall a. NonEmpty a -> [a]
forall (t :: * -> *) a. Foldable t => t a -> [a]
toList (NonEmpty a -> [a])
-> (NonEmpty a -> NonEmpty a) -> NonEmpty a -> [a]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. NonEmpty a -> NonEmpty a
f) (Maybe (NonEmpty a) -> [a])
-> ([a] -> Maybe (NonEmpty a)) -> [a] -> [a]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. [a] -> Maybe (NonEmpty a)
forall a. [a] -> Maybe (NonEmpty a)
nonEmpty