{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeFamilies #-}

{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

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


Pattern-matching bindings (HsBinds and MonoBinds)

Handles @HsBinds@; those at the top level require different handling,
in that the @Rec@/@NonRec@/etc structure is thrown away (whereas at
lower levels it is preserved with @let@/@letrec@s).
-}

module GHC.HsToCore.Binds
   ( dsTopLHsBinds, dsLHsBinds, decomposeRuleLhs, dsSpec
   , dsHsWrapper, dsEvTerm, dsTcEvBinds, dsTcEvBinds_s, dsEvBinds, dsMkUserRule
   )
where

#include "HsVersions.h"

import GHC.Prelude

import {-# SOURCE #-}   GHC.HsToCore.Expr  ( dsLExpr )
import {-# SOURCE #-}   GHC.HsToCore.Match ( matchWrapper )

import GHC.HsToCore.Monad
import GHC.HsToCore.GuardedRHSs
import GHC.HsToCore.Utils
import GHC.HsToCore.Pmc ( addTyCs, pmcGRHSs )

import GHC.Hs             -- lots of things
import GHC.Core           -- lots of things
import GHC.Core.SimpleOpt    ( simpleOptExpr )
import GHC.Core.Opt.OccurAnal ( occurAnalyseExpr )
import GHC.Core.Make
import GHC.Core.Utils
import GHC.Core.Opt.Arity     ( etaExpand )
import GHC.Core.Unfold.Make
import GHC.Core.FVs
import GHC.Data.Graph.Directed
import GHC.Core.Predicate

import GHC.Builtin.Names
import GHC.Core.TyCon
import GHC.Tc.Types.Evidence
import GHC.Tc.Utils.TcType
import GHC.Core.Type
import GHC.Core.Coercion
import GHC.Core.Multiplicity
import GHC.Builtin.Types ( naturalTy, typeSymbolKind, charTy )
import GHC.Types.Id
import GHC.Types.Name
import GHC.Types.Var.Set
import GHC.Core.Rules
import GHC.Types.Var.Env
import GHC.Types.Var( EvVar )
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Unit.Module
import GHC.Types.SrcLoc
import GHC.Data.Maybe
import GHC.Data.OrdList
import GHC.Data.Bag
import GHC.Types.Basic
import GHC.Driver.Session
import GHC.Driver.Ppr
import GHC.Driver.Config
import GHC.Data.FastString
import GHC.Utils.Misc
import GHC.Types.Unique.Set( nonDetEltsUniqSet )
import GHC.Utils.Monad
import qualified GHC.LanguageExtensions as LangExt
import Control.Monad

{-**********************************************************************
*                                                                      *
           Desugaring a MonoBinds
*                                                                      *
**********************************************************************-}

-- | Desugar top level binds, strict binds are treated like normal
-- binds since there is no good time to force before first usage.
dsTopLHsBinds :: LHsBinds GhcTc -> DsM (OrdList (Id,CoreExpr))
dsTopLHsBinds :: LHsBinds GhcTc -> DsM (OrdList (EvVar, CoreExpr))
dsTopLHsBinds LHsBinds GhcTc
binds
     -- see Note [Strict binds checks]
  | Bool -> Bool
not (forall a. Bag a -> Bool
isEmptyBag Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
unlifted_binds) Bool -> Bool -> Bool
|| Bool -> Bool
not (forall a. Bag a -> Bool
isEmptyBag Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
bang_binds)
  = do { forall (m :: * -> *) a b. Monad m => (a -> m b) -> Bag a -> m ()
mapBagM_ (forall {a} {a}.
Outputable a =>
String -> GenLocated (SrcSpanAnn' a) a -> DsM ()
top_level_err String
"bindings for unlifted types") Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
unlifted_binds
       ; forall (m :: * -> *) a b. Monad m => (a -> m b) -> Bag a -> m ()
mapBagM_ (forall {a} {a}.
Outputable a =>
String -> GenLocated (SrcSpanAnn' a) a -> DsM ()
top_level_err String
"strict bindings")             Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
bang_binds
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a. OrdList a
nilOL }

  | Bool
otherwise
  = do { ([EvVar]
force_vars, [(EvVar, CoreExpr)]
prs) <- LHsBinds GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBinds LHsBinds GhcTc
binds
       ; forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
debugIsOn forall a b. (a -> b) -> a -> b
$
         do { Bool
xstrict <- forall gbl lcl. Extension -> TcRnIf gbl lcl Bool
xoptM Extension
LangExt.Strict
            ; MASSERT2( null force_vars || xstrict, ppr binds $$ ppr force_vars ) }
              -- with -XStrict, even top-level vars are listed as force vars.

       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. [a] -> OrdList a
toOL [(EvVar, CoreExpr)]
prs) }

  where
    unlifted_binds :: Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
unlifted_binds = forall a. (a -> Bool) -> Bag a -> Bag a
filterBag (HsBind GhcTc -> Bool
isUnliftedHsBind forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) LHsBinds GhcTc
binds
    bang_binds :: Bag (GenLocated SrcSpanAnnA (HsBind GhcTc))
bang_binds     = forall a. (a -> Bool) -> Bag a -> Bag a
filterBag (HsBind GhcTc -> Bool
isBangedHsBind   forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) LHsBinds GhcTc
binds

    top_level_err :: String -> GenLocated (SrcSpanAnn' a) a -> DsM ()
top_level_err String
desc (L SrcSpanAnn' a
loc a
bind)
      = forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs (forall a. SrcSpanAnn' a -> SrcSpan
locA SrcSpanAnn' a
loc) forall a b. (a -> b) -> a -> b
$
        SDoc -> DsM ()
errDs (SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"Top-level" SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
desc SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"aren't allowed:")
                  Arity
2 (forall a. Outputable a => a -> SDoc
ppr a
bind))


-- | Desugar all other kind of bindings, Ids of strict binds are returned to
-- later be forced in the binding group body, see Note [Desugar Strict binds]
dsLHsBinds :: LHsBinds GhcTc -> DsM ([Id], [(Id,CoreExpr)])
dsLHsBinds :: LHsBinds GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBinds LHsBinds GhcTc
binds
  = do { Bag ([EvVar], [(EvVar, CoreExpr)])
ds_bs <- forall (m :: * -> *) a b.
Monad m =>
(a -> m b) -> Bag a -> m (Bag b)
mapBagM LHsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBind LHsBinds GhcTc
binds
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall r a. (r -> r -> r) -> (a -> r) -> r -> Bag a -> r
foldBag (\([EvVar]
a, [(EvVar, CoreExpr)]
a') ([EvVar]
b, [(EvVar, CoreExpr)]
b') -> ([EvVar]
a forall a. [a] -> [a] -> [a]
++ [EvVar]
b, [(EvVar, CoreExpr)]
a' forall a. [a] -> [a] -> [a]
++ [(EvVar, CoreExpr)]
b'))
                         forall a. a -> a
id ([], []) Bag ([EvVar], [(EvVar, CoreExpr)])
ds_bs) }

------------------------
dsLHsBind :: LHsBind GhcTc
          -> DsM ([Id], [(Id,CoreExpr)])
dsLHsBind :: LHsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBind (L SrcSpanAnnA
loc HsBind GhcTc
bind) = do DynFlags
dflags <- forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
                            forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs (forall a. SrcSpanAnn' a -> SrcSpan
locA SrcSpanAnnA
loc) forall a b. (a -> b) -> a -> b
$ DynFlags -> HsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsHsBind DynFlags
dflags HsBind GhcTc
bind

-- | Desugar a single binding (or group of recursive binds).
dsHsBind :: DynFlags
         -> HsBind GhcTc
         -> DsM ([Id], [(Id,CoreExpr)])
         -- ^ The Ids of strict binds, to be forced in the body of the
         -- binding group see Note [Desugar Strict binds] and all
         -- bindings and their desugared right hand sides.

dsHsBind :: DynFlags -> HsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsHsBind DynFlags
dflags (VarBind { var_id :: forall idL idR. HsBindLR idL idR -> IdP idL
var_id = IdP GhcTc
var
                         , var_rhs :: forall idL idR. HsBindLR idL idR -> LHsExpr idR
var_rhs = LHsExpr GhcTc
expr })
  = do  { CoreExpr
core_expr <- LHsExpr GhcTc -> DsM CoreExpr
dsLExpr LHsExpr GhcTc
expr
                -- Dictionary bindings are always VarBinds,
                -- so we only need do this here
        ; let core_bind :: (EvVar, CoreExpr)
core_bind@(EvVar
id,CoreExpr
_) = DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags IdP GhcTc
var Bool
False Arity
0 CoreExpr
core_expr
              force_var :: [EvVar]
force_var = if Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags
                          then [EvVar
id]
                          else []
        ; forall (m :: * -> *) a. Monad m => a -> m a
return ([EvVar]
force_var, [(EvVar, CoreExpr)
core_bind]) }

dsHsBind DynFlags
dflags b :: HsBind GhcTc
b@(FunBind { fun_id :: forall idL idR. HsBindLR idL idR -> LIdP idL
fun_id = L SrcSpanAnnN
loc EvVar
fun
                           , fun_matches :: forall idL idR. HsBindLR idL idR -> MatchGroup idR (LHsExpr idR)
fun_matches = MatchGroup GhcTc (LHsExpr GhcTc)
matches
                           , fun_ext :: forall idL idR. HsBindLR idL idR -> XFunBind idL idR
fun_ext = XFunBind GhcTc GhcTc
co_fn
                           , fun_tick :: forall idL idR. HsBindLR idL idR -> [CoreTickish]
fun_tick = [CoreTickish]
tick })
 = do   { ([EvVar]
args, CoreExpr
body) <- forall a. Origin -> Bag EvVar -> DsM a -> DsM a
addTyCs Origin
FromSource (HsWrapper -> Bag EvVar
hsWrapDictBinders XFunBind GhcTc GhcTc
co_fn) forall a b. (a -> b) -> a -> b
$
                          -- FromSource might not be accurate (we don't have any
                          -- origin annotations for things in this module), but at
                          -- worst we do superfluous calls to the pattern match
                          -- oracle.
                          -- addTyCs: Add type evidence to the refinement type
                          --            predicate of the coverage checker
                          -- See Note [Long-distance information] in "GHC.HsToCore.Pmc"
                          HsMatchContext GhcRn
-> Maybe (LHsExpr GhcTc)
-> MatchGroup GhcTc (LHsExpr GhcTc)
-> DsM ([EvVar], CoreExpr)
matchWrapper
                           (forall p. LIdP p -> HsMatchContext p
mkPrefixFunRhs (forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
loc (EvVar -> Name
idName EvVar
fun)))
                           forall a. Maybe a
Nothing MatchGroup GhcTc (LHsExpr GhcTc)
matches

        ; CoreExpr -> CoreExpr
core_wrap <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper XFunBind GhcTc GhcTc
co_fn
        ; let body' :: CoreExpr
body' = [CoreTickish] -> CoreExpr -> CoreExpr
mkOptTickBox [CoreTickish]
tick CoreExpr
body
              rhs :: CoreExpr
rhs   = CoreExpr -> CoreExpr
core_wrap (forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
args CoreExpr
body')
              core_binds :: (EvVar, CoreExpr)
core_binds@(EvVar
id,CoreExpr
_) = DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags EvVar
fun Bool
False Arity
0 CoreExpr
rhs
              force_var :: [EvVar]
force_var
                  -- Bindings are strict when -XStrict is enabled
                | Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags
                , forall (id :: Pass) body. MatchGroup (GhcPass id) body -> Arity
matchGroupArity MatchGroup GhcTc (LHsExpr GhcTc)
matches forall a. Eq a => a -> a -> Bool
== Arity
0 -- no need to force lambdas
                = [EvVar
id]
                | HsBind GhcTc -> Bool
isBangedHsBind HsBind GhcTc
b
                = [EvVar
id]
                | Bool
otherwise
                = []
        ; --pprTrace "dsHsBind" (vcat [ ppr fun <+> ppr (idInlinePragma fun)
          --                          , ppr (mg_alts matches)
          --                          , ppr args, ppr core_binds, ppr body']) $
          forall (m :: * -> *) a. Monad m => a -> m a
return ([EvVar]
force_var, [(EvVar, CoreExpr)
core_binds]) }

dsHsBind DynFlags
dflags (PatBind { pat_lhs :: forall idL idR. HsBindLR idL idR -> LPat idL
pat_lhs = LPat GhcTc
pat, pat_rhs :: forall idL idR. HsBindLR idL idR -> GRHSs idR (LHsExpr idR)
pat_rhs = GRHSs GhcTc (LHsExpr GhcTc)
grhss
                         , pat_ext :: forall idL idR. HsBindLR idL idR -> XPatBind idL idR
pat_ext = XPatBind GhcTc GhcTc
ty
                         , pat_ticks :: forall idL idR.
HsBindLR idL idR -> ([CoreTickish], [[CoreTickish]])
pat_ticks = ([CoreTickish]
rhs_tick, [[CoreTickish]]
var_ticks) })
  = do  { NonEmpty Nablas
rhss_nablas <- HsMatchContext GhcRn
-> GRHSs GhcTc (LHsExpr GhcTc) -> DsM (NonEmpty Nablas)
pmcGRHSs forall p. HsMatchContext p
PatBindGuards GRHSs GhcTc (LHsExpr GhcTc)
grhss
        ; CoreExpr
body_expr <- GRHSs GhcTc (LHsExpr GhcTc)
-> Type -> NonEmpty Nablas -> DsM CoreExpr
dsGuarded GRHSs GhcTc (LHsExpr GhcTc)
grhss XPatBind GhcTc GhcTc
ty NonEmpty Nablas
rhss_nablas
        ; let body' :: CoreExpr
body' = [CoreTickish] -> CoreExpr -> CoreExpr
mkOptTickBox [CoreTickish]
rhs_tick CoreExpr
body_expr
              pat' :: LPat GhcTc
pat'  = DynFlags -> LPat GhcTc -> LPat GhcTc
decideBangHood DynFlags
dflags LPat GhcTc
pat
        ; (EvVar
force_var,[(EvVar, CoreExpr)]
sel_binds) <- [[CoreTickish]]
-> LPat GhcTc -> CoreExpr -> DsM (EvVar, [(EvVar, CoreExpr)])
mkSelectorBinds [[CoreTickish]]
var_ticks LPat GhcTc
pat CoreExpr
body'
          -- We silently ignore inline pragmas; no makeCorePair
          -- Not so cool, but really doesn't matter
        ; let force_var' :: [EvVar]
force_var' = if forall (p :: Pass). LPat (GhcPass p) -> Bool
isBangedLPat LPat GhcTc
pat'
                           then [EvVar
force_var]
                           else []
        ; forall (m :: * -> *) a. Monad m => a -> m a
return ([EvVar]
force_var', [(EvVar, CoreExpr)]
sel_binds) }

dsHsBind DynFlags
dflags (AbsBinds { abs_tvs :: forall idL idR. HsBindLR idL idR -> [EvVar]
abs_tvs = [EvVar]
tyvars, abs_ev_vars :: forall idL idR. HsBindLR idL idR -> [EvVar]
abs_ev_vars = [EvVar]
dicts
                          , abs_exports :: forall idL idR. HsBindLR idL idR -> [ABExport idL]
abs_exports = [ABExport GhcTc]
exports
                          , abs_ev_binds :: forall idL idR. HsBindLR idL idR -> [TcEvBinds]
abs_ev_binds = [TcEvBinds]
ev_binds
                          , abs_binds :: forall idL idR. HsBindLR idL idR -> LHsBinds idL
abs_binds = LHsBinds GhcTc
binds, abs_sig :: forall idL idR. HsBindLR idL idR -> Bool
abs_sig = Bool
has_sig })
  = do { ([EvVar], [(EvVar, CoreExpr)])
ds_binds <- forall a. Origin -> Bag EvVar -> DsM a -> DsM a
addTyCs Origin
FromSource (forall a. [a] -> Bag a
listToBag [EvVar]
dicts) forall a b. (a -> b) -> a -> b
$
                     LHsBinds GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBinds LHsBinds GhcTc
binds
             -- addTyCs: push type constraints deeper
             --            for inner pattern match check
             -- See Check, Note [Long-distance information]

       ; [CoreBind]
ds_ev_binds <- [TcEvBinds] -> DsM [CoreBind]
dsTcEvBinds_s [TcEvBinds]
ev_binds

       -- dsAbsBinds does the hard work
       ; DynFlags
-> [EvVar]
-> [EvVar]
-> [ABExport GhcTc]
-> [CoreBind]
-> ([EvVar], [(EvVar, CoreExpr)])
-> Bool
-> DsM ([EvVar], [(EvVar, CoreExpr)])
dsAbsBinds DynFlags
dflags [EvVar]
tyvars [EvVar]
dicts [ABExport GhcTc]
exports [CoreBind]
ds_ev_binds ([EvVar], [(EvVar, CoreExpr)])
ds_binds Bool
has_sig }

dsHsBind DynFlags
_ (PatSynBind{}) = forall a. String -> a
panic String
"dsHsBind: PatSynBind"

-----------------------
dsAbsBinds :: DynFlags
           -> [TyVar] -> [EvVar] -> [ABExport GhcTc]
           -> [CoreBind]                -- Desugared evidence bindings
           -> ([Id], [(Id,CoreExpr)])   -- Desugared value bindings
           -> Bool                      -- Single binding with signature
           -> DsM ([Id], [(Id,CoreExpr)])

dsAbsBinds :: DynFlags
-> [EvVar]
-> [EvVar]
-> [ABExport GhcTc]
-> [CoreBind]
-> ([EvVar], [(EvVar, CoreExpr)])
-> Bool
-> DsM ([EvVar], [(EvVar, CoreExpr)])
dsAbsBinds DynFlags
dflags [EvVar]
tyvars [EvVar]
dicts [ABExport GhcTc]
exports
           [CoreBind]
ds_ev_binds ([EvVar]
force_vars, [(EvVar, CoreExpr)]
bind_prs) Bool
has_sig

    -- A very important common case: one exported variable
    -- Non-recursive bindings come through this way
    -- So do self-recursive bindings
  | [ABExport GhcTc
export] <- [ABExport GhcTc]
exports
  , ABE { abe_poly :: forall p. ABExport p -> IdP p
abe_poly = IdP GhcTc
global_id, abe_mono :: forall p. ABExport p -> IdP p
abe_mono = IdP GhcTc
local_id
        , abe_wrap :: forall p. ABExport p -> HsWrapper
abe_wrap = HsWrapper
wrap, abe_prags :: forall p. ABExport p -> TcSpecPrags
abe_prags = TcSpecPrags
prags } <- ABExport GhcTc
export
  , Just [EvVar]
force_vars' <- case [EvVar]
force_vars of
                           []                  -> forall a. a -> Maybe a
Just []
                           [EvVar
v] | EvVar
v forall a. Eq a => a -> a -> Bool
== IdP GhcTc
local_id -> forall a. a -> Maybe a
Just [IdP GhcTc
global_id]
                           [EvVar]
_                   -> forall a. Maybe a
Nothing
       -- If there is a variable to force, it's just the
       -- single variable we are binding here
  = do { CoreExpr -> CoreExpr
core_wrap <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
wrap -- Usually the identity

       ; let rhs :: CoreExpr
rhs = CoreExpr -> CoreExpr
core_wrap forall a b. (a -> b) -> a -> b
$
                   forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars forall a b. (a -> b) -> a -> b
$ forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts forall a b. (a -> b) -> a -> b
$
                   [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds forall a b. (a -> b) -> a -> b
$
                   CoreExpr
body

             body :: CoreExpr
body | Bool
has_sig
                  , [(EvVar
_, CoreExpr
lrhs)] <- [(EvVar, CoreExpr)]
bind_prs
                  = CoreExpr
lrhs
                  | Bool
otherwise
                  = forall b. [(b, Expr b)] -> Expr b -> Expr b
mkLetRec [(EvVar, CoreExpr)]
bind_prs (forall b. EvVar -> Expr b
Var IdP GhcTc
local_id)

       ; (OrdList (EvVar, CoreExpr)
spec_binds, [CoreRule]
rules) <- CoreExpr
-> TcSpecPrags -> DsM (OrdList (EvVar, CoreExpr), [CoreRule])
dsSpecs CoreExpr
rhs TcSpecPrags
prags

       ; let global_id' :: EvVar
global_id' = EvVar -> [CoreRule] -> EvVar
addIdSpecialisations IdP GhcTc
global_id [CoreRule]
rules
             main_bind :: (EvVar, CoreExpr)
main_bind  = DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags EvVar
global_id'
                                       (TcSpecPrags -> Bool
isDefaultMethod TcSpecPrags
prags)
                                       ([EvVar] -> Arity
dictArity [EvVar]
dicts) CoreExpr
rhs

       ; forall (m :: * -> *) a. Monad m => a -> m a
return ([EvVar]
force_vars', (EvVar, CoreExpr)
main_bind forall a. a -> [a] -> [a]
: forall a. OrdList a -> [a]
fromOL OrdList (EvVar, CoreExpr)
spec_binds) }

    -- Another common case: no tyvars, no dicts
    -- In this case we can have a much simpler desugaring
  | forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
tyvars, forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
dicts

  = do { let mk_bind :: ABExport GhcTc -> IOEnv (Env DsGblEnv DsLclEnv) (EvVar, CoreExpr)
mk_bind (ABE { abe_wrap :: forall p. ABExport p -> HsWrapper
abe_wrap = HsWrapper
wrap
                          , abe_poly :: forall p. ABExport p -> IdP p
abe_poly = IdP GhcTc
global
                          , abe_mono :: forall p. ABExport p -> IdP p
abe_mono = IdP GhcTc
local
                          , abe_prags :: forall p. ABExport p -> TcSpecPrags
abe_prags = TcSpecPrags
prags })
              = do { CoreExpr -> CoreExpr
core_wrap <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
wrap
                   ; forall (m :: * -> *) a. Monad m => a -> m a
return (DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags IdP GhcTc
global
                                          (TcSpecPrags -> Bool
isDefaultMethod TcSpecPrags
prags)
                                          Arity
0 (CoreExpr -> CoreExpr
core_wrap (forall b. EvVar -> Expr b
Var IdP GhcTc
local))) }
       ; [(EvVar, CoreExpr)]
main_binds <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ABExport GhcTc -> IOEnv (Env DsGblEnv DsLclEnv) (EvVar, CoreExpr)
mk_bind [ABExport GhcTc]
exports

       ; forall (m :: * -> *) a. Monad m => a -> m a
return ([EvVar]
force_vars, forall b. [Bind b] -> [(b, Expr b)]
flattenBinds [CoreBind]
ds_ev_binds forall a. [a] -> [a] -> [a]
++ [(EvVar, CoreExpr)]
bind_prs forall a. [a] -> [a] -> [a]
++ [(EvVar, CoreExpr)]
main_binds) }

    -- The general case
    -- See Note [Desugaring AbsBinds]
  | Bool
otherwise
  = do { let core_bind :: CoreBind
core_bind = forall b. [(b, Expr b)] -> Bind b
Rec [ DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags (EvVar -> EvVar
add_inline EvVar
lcl_id) Bool
False Arity
0 CoreExpr
rhs
                              | (EvVar
lcl_id, CoreExpr
rhs) <- [(EvVar, CoreExpr)]
bind_prs ]
                -- Monomorphic recursion possible, hence Rec
             new_force_vars :: [EvVar]
new_force_vars = forall {t :: * -> *}. Foldable t => t EvVar -> [EvVar]
get_new_force_vars [EvVar]
force_vars
             locals :: [EvVar]
locals       = forall a b. (a -> b) -> [a] -> [b]
map forall p. ABExport p -> IdP p
abe_mono [ABExport GhcTc]
exports
             all_locals :: [EvVar]
all_locals   = [EvVar]
locals forall a. [a] -> [a] -> [a]
++ [EvVar]
new_force_vars
             tup_expr :: CoreExpr
tup_expr     = [EvVar] -> CoreExpr
mkBigCoreVarTup [EvVar]
all_locals
             tup_ty :: Type
tup_ty       = CoreExpr -> Type
exprType CoreExpr
tup_expr
       ; let poly_tup_rhs :: CoreExpr
poly_tup_rhs = forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars forall a b. (a -> b) -> a -> b
$ forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts forall a b. (a -> b) -> a -> b
$
                            [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds forall a b. (a -> b) -> a -> b
$
                            forall b. Bind b -> Expr b -> Expr b
mkLet CoreBind
core_bind forall a b. (a -> b) -> a -> b
$
                            CoreExpr
tup_expr

       ; EvVar
poly_tup_id <- Type -> Type -> DsM EvVar
newSysLocalDs Type
Many (CoreExpr -> Type
exprType CoreExpr
poly_tup_rhs)

        -- Find corresponding global or make up a new one: sometimes
        -- we need to make new export to desugar strict binds, see
        -- Note [Desugar Strict binds]
       ; ([EvVar]
exported_force_vars, [ABExport GhcTc]
extra_exports) <- [EvVar] -> DsM ([EvVar], [ABExport GhcTc])
get_exports [EvVar]
force_vars

       ; let mk_bind :: ABExport GhcTc -> IOEnv (Env DsGblEnv DsLclEnv) [(EvVar, CoreExpr)]
mk_bind (ABE { abe_wrap :: forall p. ABExport p -> HsWrapper
abe_wrap = HsWrapper
wrap
                          , abe_poly :: forall p. ABExport p -> IdP p
abe_poly = IdP GhcTc
global
                          , abe_mono :: forall p. ABExport p -> IdP p
abe_mono = IdP GhcTc
local, abe_prags :: forall p. ABExport p -> TcSpecPrags
abe_prags = TcSpecPrags
spec_prags })
                          -- See Note [AbsBinds wrappers] in "GHC.Hs.Binds"
                = do { EvVar
tup_id  <- Type -> Type -> DsM EvVar
newSysLocalDs Type
Many Type
tup_ty
                     ; CoreExpr -> CoreExpr
core_wrap <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
wrap
                     ; let rhs :: CoreExpr
rhs = CoreExpr -> CoreExpr
core_wrap forall a b. (a -> b) -> a -> b
$ forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars forall a b. (a -> b) -> a -> b
$ forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts forall a b. (a -> b) -> a -> b
$
                                 [EvVar] -> EvVar -> EvVar -> CoreExpr -> CoreExpr
mkTupleSelector [EvVar]
all_locals IdP GhcTc
local EvVar
tup_id forall a b. (a -> b) -> a -> b
$
                                 forall b. Expr b -> [EvVar] -> Expr b
mkVarApps (forall b. EvVar -> Expr b
Var EvVar
poly_tup_id) ([EvVar]
tyvars forall a. [a] -> [a] -> [a]
++ [EvVar]
dicts)
                           rhs_for_spec :: CoreExpr
rhs_for_spec = forall b. Bind b -> Expr b -> Expr b
Let (forall b. b -> Expr b -> Bind b
NonRec EvVar
poly_tup_id CoreExpr
poly_tup_rhs) CoreExpr
rhs
                     ; (OrdList (EvVar, CoreExpr)
spec_binds, [CoreRule]
rules) <- CoreExpr
-> TcSpecPrags -> DsM (OrdList (EvVar, CoreExpr), [CoreRule])
dsSpecs CoreExpr
rhs_for_spec TcSpecPrags
spec_prags
                     ; let global' :: EvVar
global' = (IdP GhcTc
global EvVar -> InlinePragma -> EvVar
`setInlinePragma` InlinePragma
defaultInlinePragma)
                                             EvVar -> [CoreRule] -> EvVar
`addIdSpecialisations` [CoreRule]
rules
                           -- Kill the INLINE pragma because it applies to
                           -- the user written (local) function.  The global
                           -- Id is just the selector.  Hmm.
                     ; forall (m :: * -> *) a. Monad m => a -> m a
return ((EvVar
global', CoreExpr
rhs) forall a. a -> [a] -> [a]
: forall a. OrdList a -> [a]
fromOL OrdList (EvVar, CoreExpr)
spec_binds) }

       ; [[(EvVar, CoreExpr)]]
export_binds_s <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ABExport GhcTc -> IOEnv (Env DsGblEnv DsLclEnv) [(EvVar, CoreExpr)]
mk_bind ([ABExport GhcTc]
exports forall a. [a] -> [a] -> [a]
++ [ABExport GhcTc]
extra_exports)

       ; forall (m :: * -> *) a. Monad m => a -> m a
return ( [EvVar]
exported_force_vars
                , (EvVar
poly_tup_id, CoreExpr
poly_tup_rhs) forall a. a -> [a] -> [a]
:
                   forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[(EvVar, CoreExpr)]]
export_binds_s) }
  where
    inline_env :: IdEnv Id -- Maps a monomorphic local Id to one with
                             -- the inline pragma from the source
                             -- The type checker put the inline pragma
                             -- on the *global* Id, so we need to transfer it
    inline_env :: IdEnv EvVar
inline_env
      = forall a. [(EvVar, a)] -> VarEnv a
mkVarEnv [ (IdP GhcTc
lcl_id, EvVar -> InlinePragma -> EvVar
setInlinePragma IdP GhcTc
lcl_id InlinePragma
prag)
                 | ABE { abe_mono :: forall p. ABExport p -> IdP p
abe_mono = IdP GhcTc
lcl_id, abe_poly :: forall p. ABExport p -> IdP p
abe_poly = IdP GhcTc
gbl_id } <- [ABExport GhcTc]
exports
                 , let prag :: InlinePragma
prag = EvVar -> InlinePragma
idInlinePragma IdP GhcTc
gbl_id ]

    add_inline :: Id -> Id    -- tran
    add_inline :: EvVar -> EvVar
add_inline EvVar
lcl_id = forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv IdEnv EvVar
inline_env EvVar
lcl_id
                        forall a. Maybe a -> a -> a
`orElse` EvVar
lcl_id

    global_env :: IdEnv Id -- Maps local Id to its global exported Id
    global_env :: IdEnv EvVar
global_env =
      forall a. [(EvVar, a)] -> VarEnv a
mkVarEnv [ (IdP GhcTc
local, IdP GhcTc
global)
               | ABE { abe_mono :: forall p. ABExport p -> IdP p
abe_mono = IdP GhcTc
local, abe_poly :: forall p. ABExport p -> IdP p
abe_poly = IdP GhcTc
global } <- [ABExport GhcTc]
exports
               ]

    -- find variables that are not exported
    get_new_force_vars :: t EvVar -> [EvVar]
get_new_force_vars t EvVar
lcls =
      forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (\EvVar
lcl [EvVar]
acc -> case forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv IdEnv EvVar
global_env EvVar
lcl of
                           Just EvVar
_ -> [EvVar]
acc
                           Maybe EvVar
Nothing -> EvVar
lclforall a. a -> [a] -> [a]
:[EvVar]
acc)
            [] t EvVar
lcls

    -- find exports or make up new exports for force variables
    get_exports :: [Id] -> DsM ([Id], [ABExport GhcTc])
    get_exports :: [EvVar] -> DsM ([EvVar], [ABExport GhcTc])
get_exports [EvVar]
lcls =
      forall (t :: * -> *) (m :: * -> *) b a.
(Foldable t, Monad m) =>
(b -> a -> m b) -> b -> t a -> m b
foldM (\([EvVar]
glbls, [ABExport GhcTc]
exports) EvVar
lcl ->
              case forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv IdEnv EvVar
global_env EvVar
lcl of
                Just EvVar
glbl -> forall (m :: * -> *) a. Monad m => a -> m a
return (EvVar
glblforall a. a -> [a] -> [a]
:[EvVar]
glbls, [ABExport GhcTc]
exports)
                Maybe EvVar
Nothing   -> do ABExport GhcTc
export <- EvVar -> IOEnv (Env DsGblEnv DsLclEnv) (ABExport GhcTc)
mk_export EvVar
lcl
                                let glbl :: IdP GhcTc
glbl = forall p. ABExport p -> IdP p
abe_poly ABExport GhcTc
export
                                forall (m :: * -> *) a. Monad m => a -> m a
return (IdP GhcTc
glblforall a. a -> [a] -> [a]
:[EvVar]
glbls, ABExport GhcTc
exportforall a. a -> [a] -> [a]
:[ABExport GhcTc]
exports))
            ([],[]) [EvVar]
lcls

    mk_export :: EvVar -> IOEnv (Env DsGblEnv DsLclEnv) (ABExport GhcTc)
mk_export EvVar
local =
      do EvVar
global <- Type -> Type -> DsM EvVar
newSysLocalDs Type
Many
                     (CoreExpr -> Type
exprType (forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars (forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts (forall b. EvVar -> Expr b
Var EvVar
local))))
         forall (m :: * -> *) a. Monad m => a -> m a
return (ABE { abe_ext :: XABE GhcTc
abe_ext   = NoExtField
noExtField
                     , abe_poly :: IdP GhcTc
abe_poly  = EvVar
global
                     , abe_mono :: IdP GhcTc
abe_mono  = EvVar
local
                     , abe_wrap :: HsWrapper
abe_wrap  = HsWrapper
WpHole
                     , abe_prags :: TcSpecPrags
abe_prags = [LTcSpecPrag] -> TcSpecPrags
SpecPrags [] })

-- | This is where we apply INLINE and INLINABLE pragmas. All we need to
-- do is to attach the unfolding information to the Id.
--
-- Other decisions about whether to inline are made in
-- `calcUnfoldingGuidance` but the decision about whether to then expose
-- the unfolding in the interface file is made in `GHC.Iface.Tidy.addExternal`
-- using this information.
------------------------
makeCorePair :: DynFlags -> Id -> Bool -> Arity -> CoreExpr
             -> (Id, CoreExpr)
makeCorePair :: DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags EvVar
gbl_id Bool
is_default_method Arity
dict_arity CoreExpr
rhs
  | Bool
is_default_method    -- Default methods are *always* inlined
                         -- See Note [INLINE and default methods] in GHC.Tc.TyCl.Instance
  = (EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` SimpleOpts -> CoreExpr -> Unfolding
mkCompulsoryUnfolding SimpleOpts
simpl_opts CoreExpr
rhs, CoreExpr
rhs)

  | Bool
otherwise
  = case InlinePragma -> InlineSpec
inlinePragmaSpec InlinePragma
inline_prag of
          InlineSpec
NoUserInlinePrag -> (EvVar
gbl_id, CoreExpr
rhs)
          InlineSpec
NoInline         -> (EvVar
gbl_id, CoreExpr
rhs)
          InlineSpec
Inlinable        -> (EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` Unfolding
inlinable_unf, CoreExpr
rhs)
          InlineSpec
Inline           -> (EvVar, CoreExpr)
inline_pair

  where
    simpl_opts :: SimpleOpts
simpl_opts    = DynFlags -> SimpleOpts
initSimpleOpts DynFlags
dflags
    inline_prag :: InlinePragma
inline_prag   = EvVar -> InlinePragma
idInlinePragma EvVar
gbl_id
    inlinable_unf :: Unfolding
inlinable_unf = SimpleOpts -> CoreExpr -> Unfolding
mkInlinableUnfolding SimpleOpts
simpl_opts CoreExpr
rhs
    inline_pair :: (EvVar, CoreExpr)
inline_pair
       | Just Arity
arity <- InlinePragma -> Maybe Arity
inlinePragmaSat InlinePragma
inline_prag
        -- Add an Unfolding for an INLINE (but not for NOINLINE)
        -- And eta-expand the RHS; see Note [Eta-expanding INLINE things]
       , let real_arity :: Arity
real_arity = Arity
dict_arity forall a. Num a => a -> a -> a
+ Arity
arity
        -- NB: The arity in the InlineRule takes account of the dictionaries
       = ( EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` Arity -> SimpleOpts -> CoreExpr -> Unfolding
mkInlineUnfoldingWithArity Arity
real_arity SimpleOpts
simpl_opts CoreExpr
rhs
         , Arity -> CoreExpr -> CoreExpr
etaExpand Arity
real_arity CoreExpr
rhs)

       | Bool
otherwise
       = forall a. String -> SDoc -> a -> a
pprTrace String
"makeCorePair: arity missing" (forall a. Outputable a => a -> SDoc
ppr EvVar
gbl_id) forall a b. (a -> b) -> a -> b
$
         (EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` SimpleOpts -> CoreExpr -> Unfolding
mkInlineUnfolding SimpleOpts
simpl_opts CoreExpr
rhs, CoreExpr
rhs)

dictArity :: [Var] -> Arity
-- Don't count coercion variables in arity
dictArity :: [EvVar] -> Arity
dictArity [EvVar]
dicts = forall a. (a -> Bool) -> [a] -> Arity
count EvVar -> Bool
isId [EvVar]
dicts

{-
Note [Desugaring AbsBinds]
~~~~~~~~~~~~~~~~~~~~~~~~~~
In the general AbsBinds case we desugar the binding to this:

       tup a (d:Num a) = let fm = ...gm...
                             gm = ...fm...
                         in (fm,gm)
       f a d = case tup a d of { (fm,gm) -> fm }
       g a d = case tup a d of { (fm,gm) -> fm }

Note [Rules and inlining]
~~~~~~~~~~~~~~~~~~~~~~~~~
Common special case: no type or dictionary abstraction
This is a bit less trivial than you might suppose
The naive way would be to desugar to something like
        f_lcl = ...f_lcl...     -- The "binds" from AbsBinds
        M.f = f_lcl             -- Generated from "exports"
But we don't want that, because if M.f isn't exported,
it'll be inlined unconditionally at every call site (its rhs is
trivial).  That would be ok unless it has RULES, which would
thereby be completely lost.  Bad, bad, bad.

Instead we want to generate
        M.f = ...f_lcl...
        f_lcl = M.f
Now all is cool. The RULES are attached to M.f (by SimplCore),
and f_lcl is rapidly inlined away.

This does not happen in the same way to polymorphic binds,
because they desugar to
        M.f = /\a. let f_lcl = ...f_lcl... in f_lcl
Although I'm a bit worried about whether full laziness might
float the f_lcl binding out and then inline M.f at its call site

Note [Specialising in no-dict case]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Even if there are no tyvars or dicts, we may have specialisation pragmas.
Class methods can generate
      AbsBinds [] [] [( ... spec-prag]
         { AbsBinds [tvs] [dicts] ...blah }
So the overloading is in the nested AbsBinds. A good example is in GHC.Float:

  class  (Real a, Fractional a) => RealFrac a  where
    round :: (Integral b) => a -> b

  instance  RealFrac Float  where
    {-# SPECIALIZE round :: Float -> Int #-}

The top-level AbsBinds for $cround has no tyvars or dicts (because the
instance does not).  But the method is locally overloaded!

Note [Abstracting over tyvars only]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When abstracting over type variable only (not dictionaries), we don't really need to
built a tuple and select from it, as we do in the general case. Instead we can take

        AbsBinds [a,b] [ ([a,b], fg, fl, _),
                         ([b],   gg, gl, _) ]
                { fl = e1
                  gl = e2
                   h = e3 }

and desugar it to

        fg = /\ab. let B in e1
        gg = /\b. let a = () in let B in S(e2)
        h  = /\ab. let B in e3

where B is the *non-recursive* binding
        fl = fg a b
        gl = gg b
        h  = h a b    -- See (b); note shadowing!

Notice (a) g has a different number of type variables to f, so we must
             use the mkArbitraryType thing to fill in the gaps.
             We use a type-let to do that.

         (b) The local variable h isn't in the exports, and rather than
             clone a fresh copy we simply replace h by (h a b), where
             the two h's have different types!  Shadowing happens here,
             which looks confusing but works fine.

         (c) The result is *still* quadratic-sized if there are a lot of
             small bindings.  So if there are more than some small
             number (10), we filter the binding set B by the free
             variables of the particular RHS.  Tiresome.

Why got to this trouble?  It's a common case, and it removes the
quadratic-sized tuple desugaring.  Less clutter, hopefully faster
compilation, especially in a case where there are a *lot* of
bindings.


Note [Eta-expanding INLINE things]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   foo :: Eq a => a -> a
   {-# INLINE foo #-}
   foo x = ...

If (foo d) ever gets floated out as a common sub-expression (which can
happen as a result of method sharing), there's a danger that we never
get to do the inlining, which is a Terribly Bad thing given that the
user said "inline"!

To avoid this we pre-emptively eta-expand the definition, so that foo
has the arity with which it is declared in the source code.  In this
example it has arity 2 (one for the Eq and one for x). Doing this
should mean that (foo d) is a PAP and we don't share it.

Note [Nested arities]
~~~~~~~~~~~~~~~~~~~~~
For reasons that are not entirely clear, method bindings come out looking like
this:

  AbsBinds [] [] [$cfromT <= [] fromT]
    $cfromT [InlPrag=INLINE] :: T Bool -> Bool
    { AbsBinds [] [] [fromT <= [] fromT_1]
        fromT :: T Bool -> Bool
        { fromT_1 ((TBool b)) = not b } } }

Note the nested AbsBind.  The arity for the InlineRule on $cfromT should be
gotten from the binding for fromT_1.

It might be better to have just one level of AbsBinds, but that requires more
thought!


Note [Desugar Strict binds]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
See https://gitlab.haskell.org/ghc/ghc/wikis/strict-pragma

Desugaring strict variable bindings looks as follows (core below ==>)

  let !x = rhs
  in  body
==>
  let x = rhs
  in x `seq` body -- seq the variable

and if it is a pattern binding the desugaring looks like

  let !pat = rhs
  in body
==>
  let x = rhs -- bind the rhs to a new variable
      pat = x
  in x `seq` body -- seq the new variable

if there is no variable in the pattern desugaring looks like

  let False = rhs
  in body
==>
  let x = case rhs of {False -> (); _ -> error "Match failed"}
  in x `seq` body

In order to force the Ids in the binding group they are passed around
in the dsHsBind family of functions, and later seq'ed in GHC.HsToCore.Expr.ds_val_bind.

Consider a recursive group like this

  letrec
     f : g = rhs[f,g]
  in <body>

Without `Strict`, we get a translation like this:

  let t = /\a. letrec tm = rhs[fm,gm]
                      fm = case t of fm:_ -> fm
                      gm = case t of _:gm -> gm
                in
                (fm,gm)

  in let f = /\a. case t a of (fm,_) -> fm
  in let g = /\a. case t a of (_,gm) -> gm
  in <body>

Here `tm` is the monomorphic binding for `rhs`.

With `Strict`, we want to force `tm`, but NOT `fm` or `gm`.
Alas, `tm` isn't in scope in the `in <body>` part.

The simplest thing is to return it in the polymorphic
tuple `t`, thus:

  let t = /\a. letrec tm = rhs[fm,gm]
                      fm = case t of fm:_ -> fm
                      gm = case t of _:gm -> gm
                in
                (tm, fm, gm)

  in let f = /\a. case t a of (_,fm,_) -> fm
  in let g = /\a. case t a of (_,_,gm) -> gm
  in let tm = /\a. case t a of (tm,_,_) -> tm
  in tm `seq` <body>


See https://gitlab.haskell.org/ghc/ghc/wikis/strict-pragma for a more
detailed explanation of the desugaring of strict bindings.

Note [Strict binds checks]
~~~~~~~~~~~~~~~~~~~~~~~~~~
There are several checks around properly formed strict bindings. They
all link to this Note. These checks must be here in the desugarer because
we cannot know whether or not a type is unlifted until after zonking, due
to levity polymorphism. These checks all used to be handled in the typechecker
in checkStrictBinds (before Jan '17).

We define an "unlifted bind" to be any bind that binds an unlifted id. Note that

  x :: Char
  (# True, x #) = blah

is *not* an unlifted bind. Unlifted binds are detected by GHC.Hs.Utils.isUnliftedHsBind.

Define a "banged bind" to have a top-level bang. Detected by GHC.Hs.Pat.isBangedHsBind.
Define a "strict bind" to be either an unlifted bind or a banged bind.

The restrictions are:
  1. Strict binds may not be top-level. Checked in dsTopLHsBinds.

  2. Unlifted binds must also be banged. (There is no trouble to compile an unbanged
     unlifted bind, but an unbanged bind looks lazy, and we don't want users to be
     surprised by the strictness of an unlifted bind.) Checked in first clause
     of GHC.HsToCore.Expr.ds_val_bind.

  3. Unlifted binds may not have polymorphism (#6078). (That is, no quantified type
     variables or constraints.) Checked in first clause
     of GHC.HsToCore.Expr.ds_val_bind.

  4. Unlifted binds may not be recursive. Checked in second clause of ds_val_bind.

-}

------------------------
dsSpecs :: CoreExpr     -- Its rhs
        -> TcSpecPrags
        -> DsM ( OrdList (Id,CoreExpr)  -- Binding for specialised Ids
               , [CoreRule] )           -- Rules for the Global Ids
-- See Note [Handling SPECIALISE pragmas] in GHC.Tc.Gen.Bind
dsSpecs :: CoreExpr
-> TcSpecPrags -> DsM (OrdList (EvVar, CoreExpr), [CoreRule])
dsSpecs CoreExpr
_ TcSpecPrags
IsDefaultMethod = forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. OrdList a
nilOL, [])
dsSpecs CoreExpr
poly_rhs (SpecPrags [LTcSpecPrag]
sps)
  = do { [(OrdList (EvVar, CoreExpr), CoreRule)]
pairs <- forall (m :: * -> *) a b.
Applicative m =>
(a -> m (Maybe b)) -> [a] -> m [b]
mapMaybeM (Maybe CoreExpr
-> LTcSpecPrag -> DsM (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
dsSpec (forall a. a -> Maybe a
Just CoreExpr
poly_rhs)) [LTcSpecPrag]
sps
       ; let ([OrdList (EvVar, CoreExpr)]
spec_binds_s, [CoreRule]
rules) = forall a b. [(a, b)] -> ([a], [b])
unzip [(OrdList (EvVar, CoreExpr), CoreRule)]
pairs
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. [OrdList a] -> OrdList a
concatOL [OrdList (EvVar, CoreExpr)]
spec_binds_s, [CoreRule]
rules) }

dsSpec :: Maybe CoreExpr        -- Just rhs => RULE is for a local binding
                                -- Nothing => RULE is for an imported Id
                                --            rhs is in the Id's unfolding
       -> Located TcSpecPrag
       -> DsM (Maybe (OrdList (Id,CoreExpr), CoreRule))
dsSpec :: Maybe CoreExpr
-> LTcSpecPrag -> DsM (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
dsSpec Maybe CoreExpr
mb_poly_rhs (L SrcSpan
loc (SpecPrag EvVar
poly_id HsWrapper
spec_co InlinePragma
spec_inl))
  | forall a. Maybe a -> Bool
isJust (EvVar -> Maybe Class
isClassOpId_maybe EvVar
poly_id)
  = forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc forall a b. (a -> b) -> a -> b
$
    do { WarnReason -> SDoc -> DsM ()
warnDs WarnReason
NoReason (String -> SDoc
text String
"Ignoring useless SPECIALISE pragma for class method selector"
                          SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr EvVar
poly_id))
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing  }  -- There is no point in trying to specialise a class op
                            -- Moreover, classops don't (currently) have an inl_sat arity set
                            -- (it would be Just 0) and that in turn makes makeCorePair bleat

  | Bool
no_act_spec Bool -> Bool -> Bool
&& Activation -> Bool
isNeverActive Activation
rule_act
  = forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc forall a b. (a -> b) -> a -> b
$
    do { WarnReason -> SDoc -> DsM ()
warnDs WarnReason
NoReason (String -> SDoc
text String
"Ignoring useless SPECIALISE pragma for NOINLINE function:"
                          SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr EvVar
poly_id))
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing  }  -- Function is NOINLINE, and the specialisation inherits that
                            -- See Note [Activation pragmas for SPECIALISE]

  | Bool
otherwise
  = forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc forall a b. (a -> b) -> a -> b
$
    do { Unique
uniq <- forall gbl lcl. TcRnIf gbl lcl Unique
newUnique
       ; let poly_name :: Name
poly_name = EvVar -> Name
idName EvVar
poly_id
             spec_occ :: OccName
spec_occ  = OccName -> OccName
mkSpecOcc (forall a. NamedThing a => a -> OccName
getOccName Name
poly_name)
             spec_name :: Name
spec_name = Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
uniq OccName
spec_occ (forall a. NamedThing a => a -> SrcSpan
getSrcSpan Name
poly_name)
             ([EvVar]
spec_bndrs, HsWrapper
spec_app) = HsWrapper -> ([EvVar], HsWrapper)
collectHsWrapBinders HsWrapper
spec_co
               -- spec_co looks like
               --         \spec_bndrs. [] spec_args
               -- perhaps with the body of the lambda wrapped in some WpLets
               -- E.g. /\a \(d:Eq a). let d2 = $df d in [] (Maybe a) d2

       ; CoreExpr -> CoreExpr
core_app <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
spec_app

       ; let ds_lhs :: CoreExpr
ds_lhs  = CoreExpr -> CoreExpr
core_app (forall b. EvVar -> Expr b
Var EvVar
poly_id)
             spec_ty :: Type
spec_ty = [EvVar] -> Type -> Type
mkLamTypes [EvVar]
spec_bndrs (CoreExpr -> Type
exprType CoreExpr
ds_lhs)
       ; -- pprTrace "dsRule" (vcat [ text "Id:" <+> ppr poly_id
         --                         , text "spec_co:" <+> ppr spec_co
         --                         , text "ds_rhs:" <+> ppr ds_lhs ]) $
         DynFlags
dflags <- forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; case DynFlags
-> [EvVar] -> CoreExpr -> Either SDoc ([EvVar], EvVar, [CoreExpr])
decomposeRuleLhs DynFlags
dflags [EvVar]
spec_bndrs CoreExpr
ds_lhs of {
           Left SDoc
msg -> do { WarnReason -> SDoc -> DsM ()
warnDs WarnReason
NoReason SDoc
msg; forall (m :: * -> *) a. Monad m => a -> m a
return forall a. Maybe a
Nothing } ;
           Right ([EvVar]
rule_bndrs, EvVar
_fn, [CoreExpr]
rule_lhs_args) -> do

       { Module
this_mod <- forall (m :: * -> *). HasModule m => m Module
getModule
       ; let fn_unf :: Unfolding
fn_unf    = EvVar -> Unfolding
realIdUnfolding EvVar
poly_id
             simpl_opts :: SimpleOpts
simpl_opts = DynFlags -> SimpleOpts
initSimpleOpts DynFlags
dflags
             spec_unf :: Unfolding
spec_unf   = SimpleOpts
-> [EvVar]
-> (CoreExpr -> CoreExpr)
-> [CoreExpr]
-> Unfolding
-> Unfolding
specUnfolding SimpleOpts
simpl_opts [EvVar]
spec_bndrs CoreExpr -> CoreExpr
core_app [CoreExpr]
rule_lhs_args Unfolding
fn_unf
             spec_id :: EvVar
spec_id    = HasDebugCallStack => Name -> Type -> Type -> EvVar
mkLocalId Name
spec_name Type
Many Type
spec_ty -- Specialised binding is toplevel, hence Many.
                            EvVar -> InlinePragma -> EvVar
`setInlinePragma` InlinePragma
inl_prag
                            EvVar -> Unfolding -> EvVar
`setIdUnfolding`  Unfolding
spec_unf

       ; CoreRule
rule <- Module
-> Bool
-> RuleName
-> Activation
-> Name
-> [EvVar]
-> [CoreExpr]
-> CoreExpr
-> DsM CoreRule
dsMkUserRule Module
this_mod Bool
is_local_id
                        (String -> RuleName
mkFastString (String
"SPEC " forall a. [a] -> [a] -> [a]
++ forall a. Outputable a => DynFlags -> a -> String
showPpr DynFlags
dflags Name
poly_name))
                        Activation
rule_act Name
poly_name
                        [EvVar]
rule_bndrs [CoreExpr]
rule_lhs_args
                        (forall b. Expr b -> [EvVar] -> Expr b
mkVarApps (forall b. EvVar -> Expr b
Var EvVar
spec_id) [EvVar]
spec_bndrs)

       ; let spec_rhs :: CoreExpr
spec_rhs = forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
spec_bndrs (CoreExpr -> CoreExpr
core_app CoreExpr
poly_rhs)

-- Commented out: see Note [SPECIALISE on INLINE functions]
--       ; when (isInlinePragma id_inl)
--              (warnDs $ text "SPECIALISE pragma on INLINE function probably won't fire:"
--                        <+> quotes (ppr poly_name))

       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall a. a -> Maybe a
Just (forall a. a -> OrdList a
unitOL (EvVar
spec_id, CoreExpr
spec_rhs), CoreRule
rule))
            -- NB: do *not* use makeCorePair on (spec_id,spec_rhs), because
            --     makeCorePair overwrites the unfolding, which we have
            --     just created using specUnfolding
       } } }
  where
    is_local_id :: Bool
is_local_id = forall a. Maybe a -> Bool
isJust Maybe CoreExpr
mb_poly_rhs
    poly_rhs :: CoreExpr
poly_rhs | Just CoreExpr
rhs <-  Maybe CoreExpr
mb_poly_rhs
             = CoreExpr
rhs          -- Local Id; this is its rhs
             | Just CoreExpr
unfolding <- Unfolding -> Maybe CoreExpr
maybeUnfoldingTemplate (EvVar -> Unfolding
realIdUnfolding EvVar
poly_id)
             = CoreExpr
unfolding    -- Imported Id; this is its unfolding
                            -- Use realIdUnfolding so we get the unfolding
                            -- even when it is a loop breaker.
                            -- We want to specialise recursive functions!
             | Bool
otherwise = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"dsImpSpecs" (forall a. Outputable a => a -> SDoc
ppr EvVar
poly_id)
                            -- The type checker has checked that it *has* an unfolding

    id_inl :: InlinePragma
id_inl = EvVar -> InlinePragma
idInlinePragma EvVar
poly_id

    -- See Note [Activation pragmas for SPECIALISE]
    inl_prag :: InlinePragma
inl_prag | Bool -> Bool
not (InlinePragma -> Bool
isDefaultInlinePragma InlinePragma
spec_inl)    = InlinePragma
spec_inl
             | Bool -> Bool
not Bool
is_local_id  -- See Note [Specialising imported functions]
                                 -- in OccurAnal
             , OccInfo -> Bool
isStrongLoopBreaker (EvVar -> OccInfo
idOccInfo EvVar
poly_id) = InlinePragma
neverInlinePragma
             | Bool
otherwise                               = InlinePragma
id_inl
     -- Get the INLINE pragma from SPECIALISE declaration, or,
     -- failing that, from the original Id

    spec_prag_act :: Activation
spec_prag_act = InlinePragma -> Activation
inlinePragmaActivation InlinePragma
spec_inl

    -- See Note [Activation pragmas for SPECIALISE]
    -- no_act_spec is True if the user didn't write an explicit
    -- phase specification in the SPECIALISE pragma
    no_act_spec :: Bool
no_act_spec = case InlinePragma -> InlineSpec
inlinePragmaSpec InlinePragma
spec_inl of
                    InlineSpec
NoInline -> Activation -> Bool
isNeverActive  Activation
spec_prag_act
                    InlineSpec
_        -> Activation -> Bool
isAlwaysActive Activation
spec_prag_act
    rule_act :: Activation
rule_act | Bool
no_act_spec = InlinePragma -> Activation
inlinePragmaActivation InlinePragma
id_inl   -- Inherit
             | Bool
otherwise   = Activation
spec_prag_act                   -- Specified by user


dsMkUserRule :: Module -> Bool -> RuleName -> Activation
       -> Name -> [CoreBndr] -> [CoreExpr] -> CoreExpr -> DsM CoreRule
dsMkUserRule :: Module
-> Bool
-> RuleName
-> Activation
-> Name
-> [EvVar]
-> [CoreExpr]
-> CoreExpr
-> DsM CoreRule
dsMkUserRule Module
this_mod Bool
is_local RuleName
name Activation
act Name
fn [EvVar]
bndrs [CoreExpr]
args CoreExpr
rhs = do
    let rule :: CoreRule
rule = Module
-> Bool
-> Bool
-> RuleName
-> Activation
-> Name
-> [EvVar]
-> [CoreExpr]
-> CoreExpr
-> CoreRule
mkRule Module
this_mod Bool
False Bool
is_local RuleName
name Activation
act Name
fn [EvVar]
bndrs [CoreExpr]
args CoreExpr
rhs
    DynFlags
dflags <- forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
    forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (IsOrphan -> Bool
isOrphan (CoreRule -> IsOrphan
ru_orphan CoreRule
rule) Bool -> Bool -> Bool
&& WarningFlag -> DynFlags -> Bool
wopt WarningFlag
Opt_WarnOrphans DynFlags
dflags) forall a b. (a -> b) -> a -> b
$
        WarnReason -> SDoc -> DsM ()
warnDs (WarningFlag -> WarnReason
Reason WarningFlag
Opt_WarnOrphans) (CoreRule -> SDoc
ruleOrphWarn CoreRule
rule)
    forall (m :: * -> *) a. Monad m => a -> m a
return CoreRule
rule

ruleOrphWarn :: CoreRule -> SDoc
ruleOrphWarn :: CoreRule -> SDoc
ruleOrphWarn CoreRule
rule = String -> SDoc
text String
"Orphan rule:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CoreRule
rule

{- Note [SPECIALISE on INLINE functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We used to warn that using SPECIALISE for a function marked INLINE
would be a no-op; but it isn't!  Especially with worker/wrapper split
we might have
   {-# INLINE f #-}
   f :: Ord a => Int -> a -> ...
   f d x y = case x of I# x' -> $wf d x' y

We might want to specialise 'f' so that we in turn specialise '$wf'.
We can't even /name/ '$wf' in the source code, so we can't specialise
it even if we wanted to.  #10721 is a case in point.

Note [Activation pragmas for SPECIALISE]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From a user SPECIALISE pragma for f, we generate
  a) A top-level binding    spec_fn = rhs
  b) A RULE                 f dOrd = spec_fn

We need two pragma-like things:

* spec_fn's inline pragma: inherited from f's inline pragma (ignoring
                           activation on SPEC), unless overridden by SPEC INLINE

* Activation of RULE: from SPECIALISE pragma (if activation given)
                      otherwise from f's inline pragma

This is not obvious (see #5237)!

Examples      Rule activation   Inline prag on spec'd fn
---------------------------------------------------------------------
SPEC [n] f :: ty            [n]   Always, or NOINLINE [n]
                                  copy f's prag

NOINLINE f
SPEC [n] f :: ty            [n]   NOINLINE
                                  copy f's prag

NOINLINE [k] f
SPEC [n] f :: ty            [n]   NOINLINE [k]
                                  copy f's prag

INLINE [k] f
SPEC [n] f :: ty            [n]   INLINE [k]
                                  copy f's prag

SPEC INLINE [n] f :: ty     [n]   INLINE [n]
                                  (ignore INLINE prag on f,
                                  same activation for rule and spec'd fn)

NOINLINE [k] f
SPEC f :: ty                [n]   INLINE [k]


************************************************************************
*                                                                      *
\subsection{Adding inline pragmas}
*                                                                      *
************************************************************************
-}

decomposeRuleLhs :: DynFlags -> [Var] -> CoreExpr
                 -> Either SDoc ([Var], Id, [CoreExpr])
-- (decomposeRuleLhs bndrs lhs) takes apart the LHS of a RULE,
-- The 'bndrs' are the quantified binders of the rules, but decomposeRuleLhs
-- may add some extra dictionary binders (see Note [Free dictionaries])
--
-- Returns an error message if the LHS isn't of the expected shape
-- Note [Decomposing the left-hand side of a RULE]
decomposeRuleLhs :: DynFlags
-> [EvVar] -> CoreExpr -> Either SDoc ([EvVar], EvVar, [CoreExpr])
decomposeRuleLhs DynFlags
dflags [EvVar]
orig_bndrs CoreExpr
orig_lhs
  | Bool -> Bool
not (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
unbound)    -- Check for things unbound on LHS
                          -- See Note [Unused spec binders]
  = forall a b. a -> Either a b
Left ([SDoc] -> SDoc
vcat (forall a b. (a -> b) -> [a] -> [b]
map EvVar -> SDoc
dead_msg [EvVar]
unbound))
  | Var EvVar
funId <- CoreExpr
fun2
  , Just DataCon
con <- EvVar -> Maybe DataCon
isDataConId_maybe EvVar
funId
  = forall a b. a -> Either a b
Left (forall a. Outputable a => a -> SDoc
constructor_msg DataCon
con) -- See Note [No RULES on datacons]
  | Just (EvVar
fn_id, [CoreExpr]
args) <- CoreExpr -> [CoreExpr] -> Maybe (EvVar, [CoreExpr])
decompose CoreExpr
fun2 [CoreExpr]
args2
  , let extra_bndrs :: [EvVar]
extra_bndrs = EvVar -> [CoreExpr] -> [EvVar]
mk_extra_bndrs EvVar
fn_id [CoreExpr]
args
  = -- pprTrace "decomposeRuleLhs" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
    --                                  , text "orig_lhs:" <+> ppr orig_lhs
    --                                  , text "lhs1:"     <+> ppr lhs1
    --                                  , text "extra_bndrs:" <+> ppr extra_bndrs
    --                                  , text "fn_id:" <+> ppr fn_id
    --                                  , text "args:"   <+> ppr args]) $
    forall a b. b -> Either a b
Right ([EvVar]
orig_bndrs forall a. [a] -> [a] -> [a]
++ [EvVar]
extra_bndrs, EvVar
fn_id, [CoreExpr]
args)

  | Bool
otherwise
  = forall a b. a -> Either a b
Left SDoc
bad_shape_msg
 where
   simpl_opts :: SimpleOpts
simpl_opts   = DynFlags -> SimpleOpts
initSimpleOpts DynFlags
dflags
   lhs1 :: CoreExpr
lhs1         = CoreExpr -> CoreExpr
drop_dicts CoreExpr
orig_lhs
   lhs2 :: CoreExpr
lhs2         = HasDebugCallStack => SimpleOpts -> CoreExpr -> CoreExpr
simpleOptExpr SimpleOpts
simpl_opts CoreExpr
lhs1  -- See Note [Simplify rule LHS]
   (CoreExpr
fun2,[CoreExpr]
args2) = forall b. Expr b -> (Expr b, [Expr b])
collectArgs CoreExpr
lhs2

   lhs_fvs :: VarSet
lhs_fvs    = CoreExpr -> VarSet
exprFreeVars CoreExpr
lhs2
   unbound :: [EvVar]
unbound    = forall a. (a -> Bool) -> [a] -> [a]
filterOut (EvVar -> VarSet -> Bool
`elemVarSet` VarSet
lhs_fvs) [EvVar]
orig_bndrs

   orig_bndr_set :: VarSet
orig_bndr_set = [EvVar] -> VarSet
mkVarSet [EvVar]
orig_bndrs

        -- Add extra tyvar binders: Note [Free tyvars in rule LHS]
        -- and extra dict binders: Note [Free dictionaries in rule LHS]
   mk_extra_bndrs :: EvVar -> [CoreExpr] -> [EvVar]
mk_extra_bndrs EvVar
fn_id [CoreExpr]
args
     = [EvVar] -> [EvVar]
scopedSort [EvVar]
unbound_tvs forall a. [a] -> [a] -> [a]
++ [EvVar]
unbound_dicts
     where
       unbound_tvs :: [EvVar]
unbound_tvs   = [ EvVar
v | EvVar
v <- [EvVar]
unbound_vars, EvVar -> Bool
isTyVar EvVar
v ]
       unbound_dicts :: [EvVar]
unbound_dicts = [ HasDebugCallStack => Name -> Type -> Type -> EvVar
mkLocalId (Name -> Name
localiseName (EvVar -> Name
idName EvVar
d)) Type
Many (EvVar -> Type
idType EvVar
d)
                       | EvVar
d <- [EvVar]
unbound_vars, EvVar -> Bool
isDictId EvVar
d ]
       unbound_vars :: [EvVar]
unbound_vars  = [ EvVar
v | EvVar
v <- [CoreExpr] -> [EvVar]
exprsFreeVarsList [CoreExpr]
args
                           , Bool -> Bool
not (EvVar
v EvVar -> VarSet -> Bool
`elemVarSet` VarSet
orig_bndr_set)
                           , Bool -> Bool
not (EvVar
v forall a. Eq a => a -> a -> Bool
== EvVar
fn_id) ]
         -- fn_id: do not quantify over the function itself, which may
         -- itself be a dictionary (in pathological cases, #10251)

   decompose :: CoreExpr -> [CoreExpr] -> Maybe (EvVar, [CoreExpr])
decompose (Var EvVar
fn_id) [CoreExpr]
args
      | Bool -> Bool
not (EvVar
fn_id EvVar -> VarSet -> Bool
`elemVarSet` VarSet
orig_bndr_set)
      = forall a. a -> Maybe a
Just (EvVar
fn_id, [CoreExpr]
args)

   decompose CoreExpr
_ [CoreExpr]
_ = forall a. Maybe a
Nothing

   bad_shape_msg :: SDoc
bad_shape_msg = SDoc -> Arity -> SDoc -> SDoc
hang (String -> SDoc
text String
"RULE left-hand side too complicated to desugar")
                      Arity
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Optimised lhs:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CoreExpr
lhs2
                              , String -> SDoc
text String
"Orig lhs:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CoreExpr
orig_lhs])
   dead_msg :: EvVar -> SDoc
dead_msg EvVar
bndr = SDoc -> Arity -> SDoc -> SDoc
hang ([SDoc] -> SDoc
sep [ String -> SDoc
text String
"Forall'd" SDoc -> SDoc -> SDoc
<+> EvVar -> SDoc
pp_bndr EvVar
bndr
                             , String -> SDoc
text String
"is not bound in RULE lhs"])
                      Arity
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Orig bndrs:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr [EvVar]
orig_bndrs
                              , String -> SDoc
text String
"Orig lhs:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CoreExpr
orig_lhs
                              , String -> SDoc
text String
"optimised lhs:" SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr CoreExpr
lhs2 ])
   pp_bndr :: EvVar -> SDoc
pp_bndr EvVar
bndr
    | EvVar -> Bool
isTyVar EvVar
bndr = String -> SDoc
text String
"type variable" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr EvVar
bndr)
    | EvVar -> Bool
isEvVar EvVar
bndr = String -> SDoc
text String
"constraint"    SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr (EvVar -> Type
varType EvVar
bndr))
    | Bool
otherwise    = String -> SDoc
text String
"variable"      SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (forall a. Outputable a => a -> SDoc
ppr EvVar
bndr)

   constructor_msg :: a -> SDoc
constructor_msg a
con = [SDoc] -> SDoc
vcat
     [ String -> SDoc
text String
"A constructor," SDoc -> SDoc -> SDoc
<+> forall a. Outputable a => a -> SDoc
ppr a
con SDoc -> SDoc -> SDoc
<>
         String -> SDoc
text String
", appears as outermost match in RULE lhs."
     , String -> SDoc
text String
"This rule will be ignored." ]

   drop_dicts :: CoreExpr -> CoreExpr
   drop_dicts :: CoreExpr -> CoreExpr
drop_dicts CoreExpr
e
       = VarSet -> [(EvVar, CoreExpr)] -> CoreExpr -> CoreExpr
wrap_lets VarSet
needed [(EvVar, CoreExpr)]
bnds CoreExpr
body
     where
       needed :: VarSet
needed = VarSet
orig_bndr_set VarSet -> VarSet -> VarSet
`minusVarSet` CoreExpr -> VarSet
exprFreeVars CoreExpr
body
       ([(EvVar, CoreExpr)]
bnds, CoreExpr
body) = CoreExpr -> ([(EvVar, CoreExpr)], CoreExpr)
split_lets (CoreExpr -> CoreExpr
occurAnalyseExpr CoreExpr
e)
           -- The occurAnalyseExpr drops dead bindings which is
           -- crucial to ensure that every binding is used later;
           -- which in turn makes wrap_lets work right

   split_lets :: CoreExpr -> ([(DictId,CoreExpr)], CoreExpr)
   split_lets :: CoreExpr -> ([(EvVar, CoreExpr)], CoreExpr)
split_lets (Let (NonRec EvVar
d CoreExpr
r) CoreExpr
body)
     | EvVar -> Bool
isDictId EvVar
d
     = ((EvVar
d,CoreExpr
r)forall a. a -> [a] -> [a]
:[(EvVar, CoreExpr)]
bs, CoreExpr
body')
     where ([(EvVar, CoreExpr)]
bs, CoreExpr
body') = CoreExpr -> ([(EvVar, CoreExpr)], CoreExpr)
split_lets CoreExpr
body

    -- handle "unlifted lets" too, needed for "map/coerce"
   split_lets (Case CoreExpr
r EvVar
d Type
_ [Alt AltCon
DEFAULT [EvVar]
_ CoreExpr
body])
     | EvVar -> Bool
isCoVar EvVar
d
     = ((EvVar
d,CoreExpr
r)forall a. a -> [a] -> [a]
:[(EvVar, CoreExpr)]
bs, CoreExpr
body')
     where ([(EvVar, CoreExpr)]
bs, CoreExpr
body') = CoreExpr -> ([(EvVar, CoreExpr)], CoreExpr)
split_lets CoreExpr
body

   split_lets CoreExpr
e = ([], CoreExpr
e)

   wrap_lets :: VarSet -> [(DictId,CoreExpr)] -> CoreExpr -> CoreExpr
   wrap_lets :: VarSet -> [(EvVar, CoreExpr)] -> CoreExpr -> CoreExpr
wrap_lets VarSet
_ [] CoreExpr
body = CoreExpr
body
   wrap_lets VarSet
needed ((EvVar
d, CoreExpr
r) : [(EvVar, CoreExpr)]
bs) CoreExpr
body
     | VarSet
rhs_fvs VarSet -> VarSet -> Bool
`intersectsVarSet` VarSet
needed = CoreBind -> CoreExpr -> CoreExpr
mkCoreLet (forall b. b -> Expr b -> Bind b
NonRec EvVar
d CoreExpr
r) (VarSet -> [(EvVar, CoreExpr)] -> CoreExpr -> CoreExpr
wrap_lets VarSet
needed' [(EvVar, CoreExpr)]
bs CoreExpr
body)
     | Bool
otherwise                         = VarSet -> [(EvVar, CoreExpr)] -> CoreExpr -> CoreExpr
wrap_lets VarSet
needed [(EvVar, CoreExpr)]
bs CoreExpr
body
     where
       rhs_fvs :: VarSet
rhs_fvs = CoreExpr -> VarSet
exprFreeVars CoreExpr
r
       needed' :: VarSet
needed' = (VarSet
needed VarSet -> VarSet -> VarSet
`minusVarSet` VarSet
rhs_fvs) VarSet -> EvVar -> VarSet
`extendVarSet` EvVar
d

{-
Note [Decomposing the left-hand side of a RULE]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are several things going on here.
* drop_dicts: see Note [Drop dictionary bindings on rule LHS]
* simpleOptExpr: see Note [Simplify rule LHS]
* extra_dict_bndrs: see Note [Free dictionaries]

Note [Free tyvars on rule LHS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
  data T a = C

  foo :: T a -> Int
  foo C = 1

  {-# RULES "myrule"  foo C = 1 #-}

After type checking the LHS becomes (foo alpha (C alpha)), where alpha
is an unbound meta-tyvar.  The zonker in GHC.Tc.Utils.Zonk is careful not to
turn the free alpha into Any (as it usually does).  Instead it turns it
into a TyVar 'a'.  See Note [Zonking the LHS of a RULE] in "GHC.Tc.Utils.Zonk".

Now we must quantify over that 'a'.  It's /really/ inconvenient to do that
in the zonker, because the HsExpr data type is very large.  But it's /easy/
to do it here in the desugarer.

Moreover, we have to do something rather similar for dictionaries;
see Note [Free dictionaries on rule LHS].   So that's why we look for
type variables free on the LHS, and quantify over them.

Note [Free dictionaries on rule LHS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When the LHS of a specialisation rule, (/\as\ds. f es) has a free dict,
which is presumably in scope at the function definition site, we can quantify
over it too.  *Any* dict with that type will do.

So for example when you have
        f :: Eq a => a -> a
        f = <rhs>
        ... SPECIALISE f :: Int -> Int ...

Then we get the SpecPrag
        SpecPrag (f Int dInt)

And from that we want the rule

        RULE forall dInt. f Int dInt = f_spec
        f_spec = let f = <rhs> in f Int dInt

But be careful!  That dInt might be GHC.Base.$fOrdInt, which is an External
Name, and you can't bind them in a lambda or forall without getting things
confused.   Likewise it might have an InlineRule or something, which would be
utterly bogus. So we really make a fresh Id, with the same unique and type
as the old one, but with an Internal name and no IdInfo.

Note [Drop dictionary bindings on rule LHS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drop_dicts drops dictionary bindings on the LHS where possible.
   E.g.  let d:Eq [Int] = $fEqList $fEqInt in f d
     --> f d
   Reasoning here is that there is only one d:Eq [Int], and so we can
   quantify over it. That makes 'd' free in the LHS, but that is later
   picked up by extra_dict_bndrs (Note [Dead spec binders]).

   NB 1: We can only drop the binding if the RHS doesn't bind
         one of the orig_bndrs, which we assume occur on RHS.
         Example
            f :: (Eq a) => b -> a -> a
            {-# SPECIALISE f :: Eq a => b -> [a] -> [a] #-}
         Here we want to end up with
            RULE forall d:Eq a.  f ($dfEqList d) = f_spec d
         Of course, the ($dfEqlist d) in the pattern makes it less likely
         to match, but there is no other way to get d:Eq a

   NB 2: We do drop_dicts *before* simplOptEpxr, so that we expect all
         the evidence bindings to be wrapped around the outside of the
         LHS.  (After simplOptExpr they'll usually have been inlined.)
         dsHsWrapper does dependency analysis, so that civilised ones
         will be simple NonRec bindings.  We don't handle recursive
         dictionaries!

    NB3: In the common case of a non-overloaded, but perhaps-polymorphic
         specialisation, we don't need to bind *any* dictionaries for use
         in the RHS. For example (#8331)
             {-# SPECIALIZE INLINE useAbstractMonad :: ReaderST s Int #-}
             useAbstractMonad :: MonadAbstractIOST m => m Int
         Here, deriving (MonadAbstractIOST (ReaderST s)) is a lot of code
         but the RHS uses no dictionaries, so we want to end up with
             RULE forall s (d :: MonadAbstractIOST (ReaderT s)).
                useAbstractMonad (ReaderT s) d = $suseAbstractMonad s

   #8848 is a good example of where there are some interesting
   dictionary bindings to discard.

The drop_dicts algorithm is based on these observations:

  * Given (let d = rhs in e) where d is a DictId,
    matching 'e' will bind e's free variables.

  * So we want to keep the binding if one of the needed variables (for
    which we need a binding) is in fv(rhs) but not already in fv(e).

  * The "needed variables" are simply the orig_bndrs.  Consider
       f :: (Eq a, Show b) => a -> b -> String
       ... SPECIALISE f :: (Show b) => Int -> b -> String ...
    Then orig_bndrs includes the *quantified* dictionaries of the type
    namely (dsb::Show b), but not the one for Eq Int

So we work inside out, applying the above criterion at each step.


Note [Simplify rule LHS]
~~~~~~~~~~~~~~~~~~~~~~~~
simplOptExpr occurrence-analyses and simplifies the LHS:

   (a) Inline any remaining dictionary bindings (which hopefully
       occur just once)

   (b) Substitute trivial lets, so that they don't get in the way.
       Note that we substitute the function too; we might
       have this as a LHS:  let f71 = M.f Int in f71

   (c) Do eta reduction.  To see why, consider the fold/build rule,
       which without simplification looked like:
          fold k z (build (/\a. g a))  ==>  ...
       This doesn't match unless you do eta reduction on the build argument.
       Similarly for a LHS like
         augment g (build h)
       we do not want to get
         augment (\a. g a) (build h)
       otherwise we don't match when given an argument like
          augment (\a. h a a) (build h)

Note [Unused spec binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
        f :: a -> a
        ... SPECIALISE f :: Eq a => a -> a ...
It's true that this *is* a more specialised type, but the rule
we get is something like this:
        f_spec d = f
        RULE: f = f_spec d
Note that the rule is bogus, because it mentions a 'd' that is
not bound on the LHS!  But it's a silly specialisation anyway, because
the constraint is unused.  We could bind 'd' to (error "unused")
but it seems better to reject the program because it's almost certainly
a mistake.  That's what the isDeadBinder call detects.

Note [No RULES on datacons]
~~~~~~~~~~~~~~~~~~~~~~~~~~~

Previously, `RULES` like

    "JustNothing" forall x . Just x = Nothing

were allowed. Simon Peyton Jones says this seems to have been a
mistake, that such rules have never been supported intentionally,
and that he doesn't know if they can break in horrible ways.
Furthermore, Ben Gamari and Reid Barton are considering trying to
detect the presence of "static data" that the simplifier doesn't
need to traverse at all. Such rules do not play well with that.
So for now, we ban them altogether as requested by #13290. See also #7398.


************************************************************************
*                                                                      *
                Desugaring evidence
*                                                                      *
************************************************************************

-}

dsHsWrapper :: HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper :: HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
WpHole            = forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr
e
dsHsWrapper (WpTyApp Type
ty)      = forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> forall b. Expr b -> Expr b -> Expr b
App CoreExpr
e (forall b. Type -> Expr b
Type Type
ty)
dsHsWrapper (WpEvLam EvVar
ev)      = forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall b. b -> Expr b -> Expr b
Lam EvVar
ev
dsHsWrapper (WpTyLam EvVar
tv)      = forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall b. b -> Expr b -> Expr b
Lam EvVar
tv
dsHsWrapper (WpLet TcEvBinds
ev_binds)  = do { [CoreBind]
bs <- TcEvBinds -> DsM [CoreBind]
dsTcEvBinds TcEvBinds
ev_binds
                                   ; forall (m :: * -> *) a. Monad m => a -> m a
return ([CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
bs) }
dsHsWrapper (WpCompose HsWrapper
c1 HsWrapper
c2) = do { CoreExpr -> CoreExpr
w1 <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
c1
                                   ; CoreExpr -> CoreExpr
w2 <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
c2
                                   ; forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> CoreExpr
w1 forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoreExpr -> CoreExpr
w2) }
 -- See comments on WpFun in GHC.Tc.Types.Evidence for an explanation of what
 -- the specification of this clause is
dsHsWrapper (WpFun HsWrapper
c1 HsWrapper
c2 (Scaled Type
w Type
t1) SDoc
doc)
                              = do { EvVar
x <- Type -> Type -> DsM EvVar
newSysLocalDsNoLP Type
w Type
t1
                                   ; CoreExpr -> CoreExpr
w1 <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
c1
                                   ; CoreExpr -> CoreExpr
w2 <- HsWrapper -> DsM (CoreExpr -> CoreExpr)
dsHsWrapper HsWrapper
c2
                                   ; let app :: CoreExpr -> CoreExpr -> CoreExpr
app CoreExpr
f CoreExpr
a = SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreAppDs (String -> SDoc
text String
"dsHsWrapper") CoreExpr
f CoreExpr
a
                                         arg :: CoreExpr
arg     = CoreExpr -> CoreExpr
w1 (forall b. EvVar -> Expr b
Var EvVar
x)
                                   ; (()
_, Bool
ok) <- forall a. DsM a -> DsM (a, Bool)
askNoErrsDs forall a b. (a -> b) -> a -> b
$ CoreExpr -> SDoc -> DsM ()
dsNoLevPolyExpr CoreExpr
arg SDoc
doc
                                   ; if Bool
ok
                                     then forall (m :: * -> *) a. Monad m => a -> m a
return (\CoreExpr
e -> (forall b. b -> Expr b -> Expr b
Lam EvVar
x (CoreExpr -> CoreExpr
w2 (CoreExpr -> CoreExpr -> CoreExpr
app CoreExpr
e CoreExpr
arg))))
                                     else forall (m :: * -> *) a. Monad m => a -> m a
return forall a. a -> a
id }  -- this return is irrelevant
dsHsWrapper (WpCast TcCoercionR
co)       = ASSERT(coercionRole co == Representational)
                                forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr -> TcCoercionR -> CoreExpr
mkCastDs CoreExpr
e TcCoercionR
co
dsHsWrapper (WpEvApp EvTerm
tm)      = do { CoreExpr
core_tm <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
tm
                                   ; forall (m :: * -> *) a. Monad m => a -> m a
return (\CoreExpr
e -> forall b. Expr b -> Expr b -> Expr b
App CoreExpr
e CoreExpr
core_tm) }
  -- See Note [Wrapper returned from tcSubMult] in GHC.Tc.Utils.Unify.
dsHsWrapper (WpMultCoercion TcCoercionR
co) = do { forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Bool -> Bool
not (TcCoercionR -> Bool
isReflexiveCo TcCoercionR
co)) forall a b. (a -> b) -> a -> b
$
                                         SDoc -> DsM ()
errDs (String -> SDoc
text String
"Multiplicity coercions are currently not supported")
                                     ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr
e }
--------------------------------------
dsTcEvBinds_s :: [TcEvBinds] -> DsM [CoreBind]
dsTcEvBinds_s :: [TcEvBinds] -> DsM [CoreBind]
dsTcEvBinds_s []       = forall (m :: * -> *) a. Monad m => a -> m a
return []
dsTcEvBinds_s (TcEvBinds
b:[TcEvBinds]
rest) = ASSERT( null rest )  -- Zonker ensures null
                         TcEvBinds -> DsM [CoreBind]
dsTcEvBinds TcEvBinds
b

dsTcEvBinds :: TcEvBinds -> DsM [CoreBind]
dsTcEvBinds :: TcEvBinds -> DsM [CoreBind]
dsTcEvBinds (TcEvBinds {}) = forall a. String -> a
panic String
"dsEvBinds"    -- Zonker has got rid of this
dsTcEvBinds (EvBinds Bag EvBind
bs)   = Bag EvBind -> DsM [CoreBind]
dsEvBinds Bag EvBind
bs

dsEvBinds :: Bag EvBind -> DsM [CoreBind]
dsEvBinds :: Bag EvBind -> DsM [CoreBind]
dsEvBinds Bag EvBind
bs
  = do { Bag (EvVar, CoreExpr)
ds_bs <- forall (m :: * -> *) a b.
Monad m =>
(a -> m b) -> Bag a -> m (Bag b)
mapBagM EvBind -> IOEnv (Env DsGblEnv DsLclEnv) (EvVar, CoreExpr)
dsEvBind Bag EvBind
bs
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (Bag (EvVar, CoreExpr) -> [CoreBind]
mk_ev_binds Bag (EvVar, CoreExpr)
ds_bs) }

mk_ev_binds :: Bag (Id,CoreExpr) -> [CoreBind]
-- We do SCC analysis of the evidence bindings, /after/ desugaring
-- them. This is convenient: it means we can use the GHC.Core
-- free-variable functions rather than having to do accurate free vars
-- for EvTerm.
mk_ev_binds :: Bag (EvVar, CoreExpr) -> [CoreBind]
mk_ev_binds Bag (EvVar, CoreExpr)
ds_binds
  = forall a b. (a -> b) -> [a] -> [b]
map forall {b}. SCC (b, Expr b) -> Bind b
ds_scc (forall key payload.
Uniquable key =>
[Node key payload] -> [SCC payload]
stronglyConnCompFromEdgedVerticesUniq [Node EvVar (EvVar, CoreExpr)]
edges)
  where
    edges :: [ Node EvVar (EvVar,CoreExpr) ]
    edges :: [Node EvVar (EvVar, CoreExpr)]
edges = forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ((:) forall b c a. (b -> c) -> (a -> b) -> a -> c
. (EvVar, CoreExpr) -> Node EvVar (EvVar, CoreExpr)
mk_node) [] Bag (EvVar, CoreExpr)
ds_binds

    mk_node :: (Id, CoreExpr) -> Node EvVar (EvVar,CoreExpr)
    mk_node :: (EvVar, CoreExpr) -> Node EvVar (EvVar, CoreExpr)
mk_node b :: (EvVar, CoreExpr)
b@(EvVar
var, CoreExpr
rhs)
      = DigraphNode { node_payload :: (EvVar, CoreExpr)
node_payload = (EvVar, CoreExpr)
b
                    , node_key :: EvVar
node_key = EvVar
var
                    , node_dependencies :: [EvVar]
node_dependencies = forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet forall a b. (a -> b) -> a -> b
$
                                          CoreExpr -> VarSet
exprFreeVars CoreExpr
rhs VarSet -> VarSet -> VarSet
`unionVarSet`
                                          Type -> VarSet
coVarsOfType (EvVar -> Type
varType EvVar
var) }
      -- It's OK to use nonDetEltsUniqSet here as stronglyConnCompFromEdgedVertices
      -- is still deterministic even if the edges are in nondeterministic order
      -- as explained in Note [Deterministic SCC] in GHC.Data.Graph.Directed.

    ds_scc :: SCC (b, Expr b) -> Bind b
ds_scc (AcyclicSCC (b
v,Expr b
r)) = forall b. b -> Expr b -> Bind b
NonRec b
v Expr b
r
    ds_scc (CyclicSCC [(b, Expr b)]
prs)    = forall b. [(b, Expr b)] -> Bind b
Rec [(b, Expr b)]
prs

dsEvBind :: EvBind -> DsM (Id, CoreExpr)
dsEvBind :: EvBind -> IOEnv (Env DsGblEnv DsLclEnv) (EvVar, CoreExpr)
dsEvBind (EvBind { eb_lhs :: EvBind -> EvVar
eb_lhs = EvVar
v, eb_rhs :: EvBind -> EvTerm
eb_rhs = EvTerm
r}) = forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM ((,) EvVar
v) (EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
r)


{-**********************************************************************
*                                                                      *
           Desugaring EvTerms
*                                                                      *
**********************************************************************-}

dsEvTerm :: EvTerm -> DsM CoreExpr
dsEvTerm :: EvTerm -> DsM CoreExpr
dsEvTerm (EvExpr CoreExpr
e)          = forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
e
dsEvTerm (EvTypeable Type
ty EvTypeable
ev)  = Type -> EvTypeable -> DsM CoreExpr
dsEvTypeable Type
ty EvTypeable
ev
dsEvTerm (EvFun { et_tvs :: EvTerm -> [EvVar]
et_tvs = [EvVar]
tvs, et_given :: EvTerm -> [EvVar]
et_given = [EvVar]
given
                , et_binds :: EvTerm -> TcEvBinds
et_binds = TcEvBinds
ev_binds, et_body :: EvTerm -> EvVar
et_body = EvVar
wanted_id })
  = do { [CoreBind]
ds_ev_binds <- TcEvBinds -> DsM [CoreBind]
dsTcEvBinds TcEvBinds
ev_binds
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ (forall b. [b] -> Expr b -> Expr b
mkLams ([EvVar]
tvs forall a. [a] -> [a] -> [a]
++ [EvVar]
given) forall a b. (a -> b) -> a -> b
$
                   [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds forall a b. (a -> b) -> a -> b
$
                   forall b. EvVar -> Expr b
Var EvVar
wanted_id) }


{-**********************************************************************
*                                                                      *
           Desugaring Typeable dictionaries
*                                                                      *
**********************************************************************-}

dsEvTypeable :: Type -> EvTypeable -> DsM CoreExpr
-- Return a CoreExpr :: Typeable ty
-- This code is tightly coupled to the representation
-- of TypeRep, in base library Data.Typeable.Internal
dsEvTypeable :: Type -> EvTypeable -> DsM CoreExpr
dsEvTypeable Type
ty EvTypeable
ev
  = do { TyCon
tyCl <- Name -> DsM TyCon
dsLookupTyCon Name
typeableClassName    -- Typeable
       ; let kind :: Type
kind = HasDebugCallStack => Type -> Type
typeKind Type
ty
             Just DataCon
typeable_data_con
                 = TyCon -> Maybe DataCon
tyConSingleDataCon_maybe TyCon
tyCl    -- "Data constructor"
                                                    -- for Typeable

       ; CoreExpr
rep_expr <- Type -> EvTypeable -> DsM CoreExpr
ds_ev_typeable Type
ty EvTypeable
ev           -- :: TypeRep a

       -- Package up the method as `Typeable` dictionary
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall b. DataCon -> [Arg b] -> Arg b
mkConApp DataCon
typeable_data_con [forall b. Type -> Expr b
Type Type
kind, forall b. Type -> Expr b
Type Type
ty, CoreExpr
rep_expr] }

type TypeRepExpr = CoreExpr

-- | Returns a @CoreExpr :: TypeRep ty@
ds_ev_typeable :: Type -> EvTypeable -> DsM CoreExpr
ds_ev_typeable :: Type -> EvTypeable -> DsM CoreExpr
ds_ev_typeable Type
ty (EvTypeableTyCon TyCon
tc [EvTerm]
kind_ev)
  = do { EvVar
mkTrCon <- Name -> DsM EvVar
dsLookupGlobalId Name
mkTrConName
                    -- mkTrCon :: forall k (a :: k). TyCon -> TypeRep k -> TypeRep a
       ; TyCon
someTypeRepTyCon <- Name -> DsM TyCon
dsLookupTyCon Name
someTypeRepTyConName
       ; DataCon
someTypeRepDataCon <- Name -> DsM DataCon
dsLookupDataCon Name
someTypeRepDataConName
                    -- SomeTypeRep :: forall k (a :: k). TypeRep a -> SomeTypeRep

       ; CoreExpr
tc_rep <- TyCon -> DsM CoreExpr
tyConRep TyCon
tc                      -- :: TyCon
       ; let ks :: [Type]
ks = Type -> [Type]
tyConAppArgs Type
ty
             -- Construct a SomeTypeRep
             toSomeTypeRep :: Type -> EvTerm -> DsM CoreExpr
             toSomeTypeRep :: Type -> EvTerm -> DsM CoreExpr
toSomeTypeRep Type
t EvTerm
ev = do
                 CoreExpr
rep <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev Type
t
                 forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ DataCon -> [CoreExpr] -> CoreExpr
mkCoreConApps DataCon
someTypeRepDataCon [forall b. Type -> Expr b
Type (HasDebugCallStack => Type -> Type
typeKind Type
t), forall b. Type -> Expr b
Type Type
t, CoreExpr
rep]
       ; [CoreExpr]
kind_arg_reps <- forall (t :: * -> *) (m :: * -> *) a.
(Traversable t, Monad m) =>
t (m a) -> m (t a)
sequence forall a b. (a -> b) -> a -> b
$ forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith Type -> EvTerm -> DsM CoreExpr
toSomeTypeRep [Type]
ks [EvTerm]
kind_ev   -- :: TypeRep t
       ; let -- :: [SomeTypeRep]
             kind_args :: CoreExpr
kind_args = Type -> [CoreExpr] -> CoreExpr
mkListExpr (TyCon -> Type
mkTyConTy TyCon
someTypeRepTyCon) [CoreExpr]
kind_arg_reps

         -- Note that we use the kind of the type, not the TyCon from which it
         -- is constructed since the latter may be kind polymorphic whereas the
         -- former we know is not (we checked in the solver).
       ; let expr :: CoreExpr
expr = forall b. Expr b -> [Expr b] -> Expr b
mkApps (forall b. EvVar -> Expr b
Var EvVar
mkTrCon) [ forall b. Type -> Expr b
Type (HasDebugCallStack => Type -> Type
typeKind Type
ty)
                                         , forall b. Type -> Expr b
Type Type
ty
                                         , CoreExpr
tc_rep
                                         , CoreExpr
kind_args ]
       -- ; pprRuntimeTrace "Trace mkTrTyCon" (ppr expr) expr
       ; forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
expr
       }

ds_ev_typeable Type
ty (EvTypeableTyApp EvTerm
ev1 EvTerm
ev2)
  | Just (Type
t1,Type
t2) <- Type -> Maybe (Type, Type)
splitAppTy_maybe Type
ty
  = do { CoreExpr
e1  <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev1 Type
t1
       ; CoreExpr
e2  <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev2 Type
t2
       ; EvVar
mkTrApp <- Name -> DsM EvVar
dsLookupGlobalId Name
mkTrAppName
                    -- mkTrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1).
                    --            TypeRep a -> TypeRep b -> TypeRep (a b)
       ; let (Type
_, Type
k1, Type
k2) = Type -> (Type, Type, Type)
splitFunTy (HasDebugCallStack => Type -> Type
typeKind Type
t1)  -- drop the multiplicity,
                                                     -- since it's a kind
       ; let expr :: CoreExpr
expr =  forall b. Expr b -> [Expr b] -> Expr b
mkApps (forall b. Expr b -> [Type] -> Expr b
mkTyApps (forall b. EvVar -> Expr b
Var EvVar
mkTrApp) [ Type
k1, Type
k2, Type
t1, Type
t2 ])
                            [ CoreExpr
e1, CoreExpr
e2 ]
       -- ; pprRuntimeTrace "Trace mkTrApp" (ppr expr) expr
       ; forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
expr
       }

ds_ev_typeable Type
ty (EvTypeableTrFun EvTerm
evm EvTerm
ev1 EvTerm
ev2)
  | Just (Type
m,Type
t1,Type
t2) <- Type -> Maybe (Type, Type, Type)
splitFunTy_maybe Type
ty
  = do { CoreExpr
e1 <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev1 Type
t1
       ; CoreExpr
e2 <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev2 Type
t2
       ; CoreExpr
em <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
evm Type
m
       ; EvVar
mkTrFun <- Name -> DsM EvVar
dsLookupGlobalId Name
mkTrFunName
                    -- mkTrFun :: forall (m :: Multiplicity) r1 r2 (a :: TYPE r1) (b :: TYPE r2).
                    --            TypeRep m -> TypeRep a -> TypeRep b -> TypeRep (a # m -> b)
       ; let r1 :: Type
r1 = HasDebugCallStack => Type -> Type
getRuntimeRep Type
t1
             r2 :: Type
r2 = HasDebugCallStack => Type -> Type
getRuntimeRep Type
t2
       ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall b. Expr b -> [Expr b] -> Expr b
mkApps (forall b. Expr b -> [Type] -> Expr b
mkTyApps (forall b. EvVar -> Expr b
Var EvVar
mkTrFun) [Type
m, Type
r1, Type
r2, Type
t1, Type
t2])
                         [ CoreExpr
em, CoreExpr
e1, CoreExpr
e2 ]
       }

ds_ev_typeable Type
ty (EvTypeableTyLit EvTerm
ev)
  = -- See Note [Typeable for Nat and Symbol] in GHC.Tc.Solver.Interact
    do { EvVar
fun  <- Name -> DsM EvVar
dsLookupGlobalId Name
tr_fun
       ; CoreExpr
dict <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
ev       -- Of type KnownNat/KnownSymbol
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall b. Expr b -> [Expr b] -> Expr b
mkApps (forall b. Expr b -> [Type] -> Expr b
mkTyApps (forall b. EvVar -> Expr b
Var EvVar
fun) [Type
ty]) [ CoreExpr
dict ]) }
  where
    ty_kind :: Type
ty_kind = HasDebugCallStack => Type -> Type
typeKind Type
ty

    -- tr_fun is the Name of
    --       typeNatTypeRep    :: KnownNat    a => TypeRep a
    -- of    typeSymbolTypeRep :: KnownSymbol a => TypeRep a
    tr_fun :: Name
tr_fun | Type
ty_kind Type -> Type -> Bool
`eqType` Type
naturalTy      = Name
typeNatTypeRepName
           | Type
ty_kind Type -> Type -> Bool
`eqType` Type
typeSymbolKind = Name
typeSymbolTypeRepName
           | Type
ty_kind Type -> Type -> Bool
`eqType` Type
charTy         = Name
typeCharTypeRepName
           | Bool
otherwise = forall a. String -> a
panic String
"dsEvTypeable: unknown type lit kind"

ds_ev_typeable Type
ty EvTypeable
ev
  = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"dsEvTypeable" (forall a. Outputable a => a -> SDoc
ppr Type
ty SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr EvTypeable
ev)

getRep :: EvTerm          -- ^ EvTerm for @Typeable ty@
       -> Type            -- ^ The type @ty@
       -> DsM TypeRepExpr -- ^ Return @CoreExpr :: TypeRep ty@
                          -- namely @typeRep# dict@
-- Remember that
--   typeRep# :: forall k (a::k). Typeable k a -> TypeRep a
getRep :: EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev Type
ty
  = do { CoreExpr
typeable_expr <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
ev
       ; EvVar
typeRepId     <- Name -> DsM EvVar
dsLookupGlobalId Name
typeRepIdName
       ; let ty_args :: [Type]
ty_args = [HasDebugCallStack => Type -> Type
typeKind Type
ty, Type
ty]
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall b. Expr b -> [Expr b] -> Expr b
mkApps (forall b. Expr b -> [Type] -> Expr b
mkTyApps (forall b. EvVar -> Expr b
Var EvVar
typeRepId) [Type]
ty_args) [ CoreExpr
typeable_expr ]) }

tyConRep :: TyCon -> DsM CoreExpr
-- Returns CoreExpr :: TyCon
tyConRep :: TyCon -> DsM CoreExpr
tyConRep TyCon
tc
  | Just Name
tc_rep_nm <- TyCon -> Maybe Name
tyConRepName_maybe TyCon
tc
  = do { EvVar
tc_rep_id <- Name -> DsM EvVar
dsLookupGlobalId Name
tc_rep_nm
       ; forall (m :: * -> *) a. Monad m => a -> m a
return (forall b. EvVar -> Expr b
Var EvVar
tc_rep_id) }
  | Bool
otherwise
  = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tyConRep" (forall a. Outputable a => a -> SDoc
ppr TyCon
tc)