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

{-
(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, dsHsWrappers
   , dsEvTerm, dsTcEvBinds, dsTcEvBinds_s, dsEvBinds
   , dsWarnOrphanRule
   )
where

import GHC.Prelude

import GHC.Driver.DynFlags
import GHC.Driver.Config
import qualified GHC.LanguageExtensions as LangExt
import GHC.Unit.Module

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

import GHC.HsToCore.Pmc.Utils( tracePm )

import GHC.HsToCore.Monad
import GHC.HsToCore.Errors.Types
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.InstEnv ( CanonicalEvidence(..) )
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.Core.Predicate
import GHC.Core.TyCon
import GHC.Core.Type
import GHC.Core.Coercion
import GHC.Core.Rules
import GHC.Core.TyCo.Compare( eqType )

import GHC.Builtin.Names
import GHC.Builtin.Types ( naturalTy, typeSymbolKind, charTy )

import GHC.Tc.Types.Evidence

import GHC.Types.Id
import GHC.Types.Name
import GHC.Types.Var.Set
import GHC.Types.Var.Env
import GHC.Types.Var( EvVar )
import GHC.Types.SrcLoc
import GHC.Types.Basic
import GHC.Types.Unique.Set( nonDetEltsUniqSet )

import GHC.Data.Maybe
import GHC.Data.OrdList
import GHC.Data.Graph.Directed
import GHC.Data.Bag
import qualified Data.Set as S

import GHC.Utils.Constants (debugIsOn)
import GHC.Utils.Misc
import GHC.Utils.Monad
import GHC.Utils.Outputable
import GHC.Utils.Panic

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 ([GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
unlifted_binds) Bool -> Bool -> Bool
|| Bool -> Bool
not ([GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
bang_binds)
  = do { (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
 -> IOEnv (Env DsGblEnv DsLclEnv) ())
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (BindsType
-> GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall {a}.
HasLoc a =>
BindsType
-> GenLocated a (HsBindLR GhcTc GhcTc)
-> IOEnv (Env DsGblEnv DsLclEnv) ()
top_level_err BindsType
UnliftedTypeBinds) [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
unlifted_binds
       ; (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
 -> IOEnv (Env DsGblEnv DsLclEnv) ())
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall (t :: * -> *) (m :: * -> *) a b.
(Foldable t, Monad m) =>
(a -> m b) -> t a -> m ()
mapM_ (BindsType
-> GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall {a}.
HasLoc a =>
BindsType
-> GenLocated a (HsBindLR GhcTc GhcTc)
-> IOEnv (Env DsGblEnv DsLclEnv) ()
top_level_err BindsType
StrictBinds)       [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
bang_binds
       ; OrdList (EvVar, CoreExpr) -> DsM (OrdList (EvVar, CoreExpr))
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return OrdList (EvVar, CoreExpr)
forall a. OrdList a
nilOL }

  | Bool
otherwise
  = do { (force_vars, prs) <- LHsBinds GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBinds LHsBinds GhcTc
binds
       ; when debugIsOn $
         do { xstrict <- xoptM LangExt.Strict
            ; massertPpr (null force_vars || xstrict) (ppr binds $$ ppr force_vars) }
              -- with -XStrict, even top-level vars are listed as force vars.

       ; return (toOL prs) }

  where
    unlifted_binds :: [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
unlifted_binds = (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc) -> Bool)
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
forall a. (a -> Bool) -> [a] -> [a]
filter (HsBindLR GhcTc GhcTc -> Bool
isUnliftedHsBind (HsBindLR GhcTc GhcTc -> Bool)
-> (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
    -> HsBindLR GhcTc GhcTc)
-> GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> HsBindLR GhcTc GhcTc
forall l e. GenLocated l e -> e
unLoc) LHsBinds GhcTc
[GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
binds
    bang_binds :: [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
bang_binds     = (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc) -> Bool)
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
forall a. (a -> Bool) -> [a] -> [a]
filter (HsBindLR GhcTc GhcTc -> Bool
isBangedHsBind   (HsBindLR GhcTc GhcTc -> Bool)
-> (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
    -> HsBindLR GhcTc GhcTc)
-> GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> HsBindLR GhcTc GhcTc
forall l e. GenLocated l e -> e
unLoc) LHsBinds GhcTc
[GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
binds

    top_level_err :: BindsType
-> GenLocated a (HsBindLR GhcTc GhcTc)
-> IOEnv (Env DsGblEnv DsLclEnv) ()
top_level_err BindsType
bindsType (L a
loc HsBindLR GhcTc GhcTc
bind)
      = SrcSpan
-> IOEnv (Env DsGblEnv DsLclEnv) ()
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs (a -> SrcSpan
forall a. HasLoc a => a -> SrcSpan
locA a
loc) (IOEnv (Env DsGblEnv DsLclEnv) ()
 -> IOEnv (Env DsGblEnv DsLclEnv) ())
-> IOEnv (Env DsGblEnv DsLclEnv) ()
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall a b. (a -> b) -> a -> b
$
        DsMessage -> IOEnv (Env DsGblEnv DsLclEnv) ()
diagnosticDs (BindsType -> HsBindLR GhcTc GhcTc -> DsMessage
DsTopLevelBindsNotAllowed BindsType
bindsType HsBindLR GhcTc GhcTc
bind)
{-
Note [Return non-recursive bindings in dependency order]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For recursive bindings, the desugarer has no choice: it returns a single big
Rec{...} group.

But for /non-recursive/ bindings, the desugarer guarantees to desugar them to
a sequence of non-recurive Core bindings, in dependency order.

Why is this important?  Partly it saves a bit of work in the first run of the
occurrence analyser. But more importantly, for linear types, non-recursive lets
can be linear whereas recursive-let can't. Since we check the output of the
desugarer for linearity (see also Note [Linting linearity]), desugaring
non-recursive lets to recursive lets would break linearity checks. An
alternative is to refine the typing rule for recursive lets so that we don't
have to care (see in particular #23218 and #18694), but the outcome of this line
of work is still unclear. In the meantime, being a little precise in the
desugarer is cheap. (paragraph written on 2023-06-09)

In dsLHSBinds (and dependencies), a single binding can be desugared to multiple
bindings. For instance because the source binding has the {-# SPECIALIZE #-}
pragma. In:

f _ = …
 where
  {-# SPECIALIZE g :: F Int -> F Int #-}
  g :: C a => F a -> F a
  g _ = …

The g binding desugars to

let {
  $sg = … } in

  g
  [RULES: "SPEC g" g @Int $dC = $sg]
  g = …

In order to avoid generating a letrec that will immediately be reordered, we
make sure to return the binding in dependency order [$sg, g].

-}

-- | 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]
--
-- Invariant: the desugared bindings are returned in dependency order,
-- see Note [Return non-recursive bindings in dependency order]
dsLHsBinds :: LHsBinds GhcTc -> DsM ([Id], [(Id,CoreExpr)])
dsLHsBinds :: LHsBinds GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBinds LHsBinds GhcTc
binds
  = do { ds_bs <- (GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
 -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> [GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
-> IOEnv (Env DsGblEnv DsLclEnv) [([EvVar], [(EvVar, 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 LHsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)
-> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBind LHsBinds GhcTc
[GenLocated SrcSpanAnnA (HsBindLR GhcTc GhcTc)]
binds
       ; return (foldr (\([EvVar]
a, [(EvVar, CoreExpr)]
a') ([EvVar]
b, [(EvVar, CoreExpr)]
b') -> ([EvVar]
a [EvVar] -> [EvVar] -> [EvVar]
forall a. [a] -> [a] -> [a]
++ [EvVar]
b, [(EvVar, CoreExpr)]
a' [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
forall a. [a] -> [a] -> [a]
++ [(EvVar, CoreExpr)]
b'))
                         ([], []) ds_bs) }

------------------------
dsLHsBind :: LHsBind GhcTc
          -> DsM ([Id], [(Id,CoreExpr)])
dsLHsBind :: LHsBind GhcTc -> DsM ([EvVar], [(EvVar, CoreExpr)])
dsLHsBind (L SrcSpanAnnA
loc HsBindLR GhcTc GhcTc
bind) = do dflags <- IOEnv (Env DsGblEnv DsLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
                            putSrcSpanDs (locA loc) $ dsHsBind dflags bind

-- | Desugar a single binding (or group of recursive binds).
--
-- Invariant: the desugared bindings are returned in dependency order,
-- see Note [Return non-recursive bindings in dependency order]
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
-> HsBindLR GhcTc 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  { 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@(id,_) = makeCorePair dflags var False 0 core_expr
              force_var = if Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags
                          then [EvVar
id]
                          else []
        ; return (force_var, [core_bind]) }

dsHsBind DynFlags
dflags b :: HsBindLR GhcTc 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 = (HsWrapper
co_fn, [CoreTickish]
tick)
                           })
 = HsWrapper
-> ((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> DsM ([EvVar], [(EvVar, CoreExpr)])
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper HsWrapper
co_fn (((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
 -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> ((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> DsM ([EvVar], [(EvVar, CoreExpr)])
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
core_wrap ->
   do { (args, body) <- HsMatchContextRn
-> Maybe [LHsExpr GhcTc]
-> MatchGroup GhcTc (LHsExpr GhcTc)
-> DsM ([EvVar], CoreExpr)
matchWrapper (GenLocated SrcSpanAnnN Name
-> AnnFunRhs -> HsMatchContext (GenLocated SrcSpanAnnN Name)
forall fn. fn -> AnnFunRhs -> HsMatchContext fn
mkPrefixFunRhs (SrcSpanAnnN -> Name -> GenLocated SrcSpanAnnN Name
forall l e. l -> e -> GenLocated l e
L SrcSpanAnnN
loc (EvVar -> Name
idName EvVar
fun)) AnnFunRhs
forall a. NoAnn a => a
noAnn) Maybe [LHsExpr GhcTc]
Maybe [GenLocated SrcSpanAnnA (HsExpr GhcTc)]
forall a. Maybe a
Nothing MatchGroup GhcTc (LHsExpr GhcTc)
matches

      ; let body' = [CoreTickish] -> CoreExpr -> CoreExpr
mkOptTickBox [CoreTickish]
tick CoreExpr
body
            rhs   = CoreExpr -> CoreExpr
core_wrap ([EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
args CoreExpr
body')
            core_binds@(id,_) = makeCorePair dflags fun False 0 rhs
            force_var
                -- Bindings are strict when -XStrict is enabled
              | Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags
              , MatchGroup GhcTc (GenLocated SrcSpanAnnA (HsExpr GhcTc)) -> Arity
forall (id :: Pass) body. MatchGroup (GhcPass id) body -> Arity
matchGroupArity MatchGroup GhcTc (LHsExpr GhcTc)
MatchGroup GhcTc (GenLocated SrcSpanAnnA (HsExpr GhcTc))
matches Arity -> Arity -> Bool
forall a. Eq a => a -> a -> Bool
== Arity
0 -- no need to force lambdas
              = [EvVar
id]
              | HsBindLR GhcTc GhcTc -> Bool
isBangedHsBind HsBindLR GhcTc 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']) $
        return (force_var, [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 = (Type
ty, ([CoreTickish]
rhs_tick, [[CoreTickish]]
var_ticks))
                         })
  = do  { rhss_nablas <- HsMatchContextRn
-> GRHSs GhcTc (LHsExpr GhcTc) -> DsM (NonEmpty Nablas)
pmcGRHSs HsMatchContextRn
HsMatchContext (GenLocated SrcSpanAnnN Name)
forall fn. HsMatchContext fn
PatBindGuards GRHSs GhcTc (LHsExpr GhcTc)
grhss
        ; body_expr <- dsGuarded grhss ty rhss_nablas
        ; let body' = [CoreTickish] -> CoreExpr -> CoreExpr
mkOptTickBox [CoreTickish]
rhs_tick CoreExpr
body_expr
              pat'  = DynFlags -> LPat GhcTc -> LPat GhcTc
decideBangHood DynFlags
dflags LPat GhcTc
pat
        ; (force_var,sel_binds) <- mkSelectorBinds var_ticks pat PatBindRhs body'
          -- We silently ignore inline pragmas; no makeCorePair
          -- Not so cool, but really doesn't matter
        ; let force_var' = if LPat GhcTc -> Bool
forall (p :: Pass). LPat (GhcPass p) -> Bool
isBangedLPat LPat GhcTc
pat'
                           then [EvVar
force_var]
                           else []
        ; return (force_var', sel_binds) }

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

dsHsBind DynFlags
_ (PatSynBind{}) = String -> DsM ([EvVar], [(EvVar, CoreExpr)])
forall a. HasCallStack => String -> a
panic String
"dsHsBind: PatSynBind"

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

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

    -- A very important common case: one exported variable
    -- Non-recursive bindings come through this way
    -- So do self-recursive bindings
    --    gbl_id = wrap (/\tvs \dicts. let ev_binds
    --                                 letrec bind_prs
    --                                 in lcl_id)
  | [ABExport
export] <- [ABExport]
exports
  , ABE { abe_poly :: ABExport -> EvVar
abe_poly = EvVar
global_id, abe_mono :: ABExport -> EvVar
abe_mono = EvVar
local_id
        , abe_wrap :: ABExport -> HsWrapper
abe_wrap = HsWrapper
wrap, abe_prags :: ABExport -> TcSpecPrags
abe_prags = TcSpecPrags
prags } <- ABExport
export
  , Just [EvVar]
force_vars' <- case [EvVar]
force_vars of
                           []                  -> [EvVar] -> Maybe [EvVar]
forall a. a -> Maybe a
Just []
                           [EvVar
v] | EvVar
v EvVar -> EvVar -> Bool
forall a. Eq a => a -> a -> Bool
== EvVar
local_id -> [EvVar] -> Maybe [EvVar]
forall a. a -> Maybe a
Just [EvVar
global_id]
                           [EvVar]
_                   -> Maybe [EvVar]
forall a. Maybe a
Nothing
       -- If there is a variable to force, it's just the
       -- single variable we are binding here
  = do { HsWrapper
-> ((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> DsM ([EvVar], [(EvVar, CoreExpr)])
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper HsWrapper
wrap (((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
 -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> ((CoreExpr -> CoreExpr) -> DsM ([EvVar], [(EvVar, CoreExpr)]))
-> DsM ([EvVar], [(EvVar, CoreExpr)])
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
core_wrap -> do -- Usually the identity
       { let rhs :: CoreExpr
rhs = CoreExpr -> CoreExpr
core_wrap (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                   [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                   [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
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
                  = [(EvVar, CoreExpr)] -> CoreExpr -> CoreExpr
forall b. [(b, Expr b)] -> Expr b -> Expr b
mkLetRec [(EvVar, CoreExpr)]
bind_prs (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
local_id)

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

       ; let global_id' = EvVar -> [CoreRule] -> EvVar
addIdSpecialisations EvVar
global_id [CoreRule]
rules
             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

       ; return (force_vars', fromOL spec_binds ++ [main_bind]) } }

    -- Another common case: no tyvars, no dicts
    -- In this case we can have a much simpler desugaring
    --    lcl_id{inl-prag} = rhs  -- Auxiliary binds
    --    gbl_id = lcl_id |> co   -- Main binds
    --
    -- See Note [The no-tyvar no-dict case]
  | [EvVar] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
tyvars, [EvVar] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
dicts
  = do { let wrap_first_bind :: (b -> b) -> [(a, b)] -> [(a, b)]
wrap_first_bind b -> b
f ((a
main, b
main_rhs):[(a, b)]
other_binds) =
               ((a
main, b -> b
f b
main_rhs)(a, b) -> [(a, b)] -> [(a, b)]
forall a. a -> [a] -> [a]
:[(a, b)]
other_binds)
             wrap_first_bind b -> b
_ [] = String -> [(a, b)]
forall a. HasCallStack => String -> a
panic String
"dsAbsBinds received an empty binding list"

             mk_main :: ABExport -> DsM (Id, CoreExpr)
             mk_main :: ABExport -> DsM (EvVar, CoreExpr)
mk_main (ABE { abe_poly :: ABExport -> EvVar
abe_poly = EvVar
gbl_id, abe_mono :: ABExport -> EvVar
abe_mono = EvVar
lcl_id
                          , abe_wrap :: ABExport -> HsWrapper
abe_wrap = HsWrapper
wrap })
                     -- No SpecPrags (no dicts)
                     -- Can't be a default method (default methods are singletons)
               = do { HsWrapper
-> ((CoreExpr -> CoreExpr) -> DsM (EvVar, CoreExpr))
-> DsM (EvVar, CoreExpr)
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper HsWrapper
wrap (((CoreExpr -> CoreExpr) -> DsM (EvVar, CoreExpr))
 -> DsM (EvVar, CoreExpr))
-> ((CoreExpr -> CoreExpr) -> DsM (EvVar, CoreExpr))
-> DsM (EvVar, CoreExpr)
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
core_wrap -> do
                    { (EvVar, CoreExpr) -> DsM (EvVar, CoreExpr)
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ( EvVar
gbl_id EvVar -> InlinePragma -> EvVar
`setInlinePragma` InlinePragma
defaultInlinePragma
                             , CoreExpr -> CoreExpr
core_wrap (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
lcl_id)) } }
       ; main_prs <- (ABExport -> DsM (EvVar, CoreExpr))
-> [ABExport] -> IOEnv (Env DsGblEnv DsLclEnv) [(EvVar, 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 ABExport -> DsM (EvVar, CoreExpr)
mk_main [ABExport]
exports
       ; let bind_prs' = ((EvVar, CoreExpr) -> (EvVar, CoreExpr))
-> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
forall a b. (a -> b) -> [a] -> [b]
map (EvVar, CoreExpr) -> (EvVar, CoreExpr)
mk_aux_bind [(EvVar, CoreExpr)]
bind_prs
             -- When there's a single source binding, we wrap the evidence binding in a
             -- separate let-rec (DSB1) inside the first desugared binding (DSB2).
             -- See Note [The no-tyvar no-dict case].
             final_prs | Bool
is_singleton = (CoreExpr -> CoreExpr)
-> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
forall {b} {a}. (b -> b) -> [(a, b)] -> [(a, b)]
wrap_first_bind ([CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds) [(EvVar, CoreExpr)]
bind_prs'
                       | Bool
otherwise = [CoreBind] -> [(EvVar, CoreExpr)]
forall b. [Bind b] -> [(b, Expr b)]
flattenBinds [CoreBind]
ds_ev_binds [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
forall a. [a] -> [a] -> [a]
++ [(EvVar, CoreExpr)]
bind_prs'
       ; return (force_vars, final_prs ++ main_prs ) }

    -- The general case
    -- See Note [Desugaring AbsBinds]
  | Bool
otherwise
  = do { let aux_binds :: CoreBind
aux_binds = [(EvVar, CoreExpr)] -> CoreBind
forall b. [(b, Expr b)] -> Bind b
Rec (((EvVar, CoreExpr) -> (EvVar, CoreExpr))
-> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
forall a b. (a -> b) -> [a] -> [b]
map (EvVar, CoreExpr) -> (EvVar, CoreExpr)
mk_aux_bind [(EvVar, CoreExpr)]
bind_prs)
                -- Monomorphic recursion possible, hence Rec

             new_force_vars :: [EvVar]
new_force_vars = [EvVar] -> [EvVar]
forall {t :: * -> *}. Foldable t => t EvVar -> [EvVar]
get_new_force_vars [EvVar]
force_vars
             locals :: [EvVar]
locals       = (ABExport -> EvVar) -> [ABExport] -> [EvVar]
forall a b. (a -> b) -> [a] -> [b]
map ABExport -> EvVar
abe_mono [ABExport]
exports
             all_locals :: [EvVar]
all_locals   = [EvVar]
locals [EvVar] -> [EvVar] -> [EvVar]
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       = HasDebugCallStack => CoreExpr -> Type
CoreExpr -> Type
exprType CoreExpr
tup_expr
       ; let poly_tup_rhs :: CoreExpr
poly_tup_rhs = [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                            [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                            CoreBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
mkLet CoreBind
aux_binds (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                            CoreExpr
tup_expr

       ; poly_tup_id <- Type -> DsM EvVar
newSysLocalMDs (HasDebugCallStack => CoreExpr -> Type
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]
       ; (exported_force_vars, extra_exports) <- get_exports force_vars

       ; let mk_bind (ABE { abe_wrap :: ABExport -> HsWrapper
abe_wrap = HsWrapper
wrap
                          , abe_poly :: ABExport -> EvVar
abe_poly = EvVar
global
                          , abe_mono :: ABExport -> EvVar
abe_mono = EvVar
local, abe_prags :: ABExport -> TcSpecPrags
abe_prags = TcSpecPrags
spec_prags })
                          -- See Note [ABExport wrapper] in "GHC.Hs.Binds"
                = do { tup_id  <- Type -> DsM EvVar
newSysLocalMDs Type
tup_ty
                     ; dsHsWrapper wrap $ \CoreExpr -> CoreExpr
core_wrap -> do
                     { let rhs :: CoreExpr
rhs = CoreExpr -> CoreExpr
core_wrap (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                                 [EvVar] -> EvVar -> EvVar -> CoreExpr -> CoreExpr
mkBigTupleSelector [EvVar]
all_locals EvVar
local EvVar
tup_id (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                                 CoreExpr -> [EvVar] -> CoreExpr
forall b. Expr b -> [EvVar] -> Expr b
mkVarApps (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
poly_tup_id) ([EvVar]
tyvars [EvVar] -> [EvVar] -> [EvVar]
forall a. [a] -> [a] -> [a]
++ [EvVar]
dicts)
                           rhs_for_spec :: CoreExpr
rhs_for_spec = CoreBind -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let (EvVar -> CoreExpr -> CoreBind
forall b. b -> Expr b -> Bind b
NonRec EvVar
poly_tup_id CoreExpr
poly_tup_rhs) CoreExpr
rhs
                     ; (spec_binds, rules) <- CoreExpr
-> TcSpecPrags -> DsM (OrdList (EvVar, CoreExpr), [CoreRule])
dsSpecs CoreExpr
rhs_for_spec TcSpecPrags
spec_prags
                     ; let global' = (EvVar
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.
                     ; return (fromOL spec_binds ++ [(global', rhs)]) } }

       ; export_binds_s <- mapM mk_bind (exports ++ extra_exports)

       ; return ( exported_force_vars
                , (poly_tup_id, poly_tup_rhs) :
                   concat export_binds_s) }
  where
    mk_aux_bind :: (Id,CoreExpr) -> (Id,CoreExpr)
    mk_aux_bind :: (EvVar, CoreExpr) -> (EvVar, CoreExpr)
mk_aux_bind (EvVar
lcl_id, CoreExpr
rhs) = let lcl_w_inline :: EvVar
lcl_w_inline = VarEnv EvVar -> EvVar -> Maybe EvVar
forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv VarEnv EvVar
inline_env EvVar
lcl_id
                                                   Maybe EvVar -> EvVar -> EvVar
forall a. Maybe a -> a -> a
`orElse` EvVar
lcl_id
                                 in
                                 DynFlags -> EvVar -> Bool -> Arity -> CoreExpr -> (EvVar, CoreExpr)
makeCorePair DynFlags
dflags EvVar
lcl_w_inline Bool
False Arity
0 CoreExpr
rhs

    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 :: VarEnv EvVar
inline_env
      = [(EvVar, EvVar)] -> VarEnv EvVar
forall a. [(EvVar, a)] -> VarEnv a
mkVarEnv [ (EvVar
lcl_id, EvVar -> InlinePragma -> EvVar
setInlinePragma EvVar
lcl_id InlinePragma
prag)
                 | ABE { abe_mono :: ABExport -> EvVar
abe_mono = EvVar
lcl_id, abe_poly :: ABExport -> EvVar
abe_poly = EvVar
gbl_id } <- [ABExport]
exports
                 , let prag :: InlinePragma
prag = EvVar -> InlinePragma
idInlinePragma EvVar
gbl_id ]

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

    -- find variables that are not exported
    get_new_force_vars :: t EvVar -> [EvVar]
get_new_force_vars t EvVar
lcls =
      (EvVar -> [EvVar] -> [EvVar]) -> [EvVar] -> t EvVar -> [EvVar]
forall a b. (a -> b -> b) -> b -> t a -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (\EvVar
lcl [EvVar]
acc -> case VarEnv EvVar -> EvVar -> Maybe EvVar
forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv VarEnv EvVar
global_env EvVar
lcl of
                           Just EvVar
_ -> [EvVar]
acc
                           Maybe EvVar
Nothing -> EvVar
lclEvVar -> [EvVar] -> [EvVar]
forall 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])
    get_exports :: [EvVar] -> DsM ([EvVar], [ABExport])
get_exports [EvVar]
lcls =
      (([EvVar], [ABExport]) -> EvVar -> DsM ([EvVar], [ABExport]))
-> ([EvVar], [ABExport]) -> [EvVar] -> DsM ([EvVar], [ABExport])
forall (t :: * -> *) (m :: * -> *) b a.
(Foldable t, Monad m) =>
(b -> a -> m b) -> b -> t a -> m b
foldM (\([EvVar]
glbls, [ABExport]
exports) EvVar
lcl ->
              case VarEnv EvVar -> EvVar -> Maybe EvVar
forall a. VarEnv a -> EvVar -> Maybe a
lookupVarEnv VarEnv EvVar
global_env EvVar
lcl of
                Just EvVar
glbl -> ([EvVar], [ABExport]) -> DsM ([EvVar], [ABExport])
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (EvVar
glblEvVar -> [EvVar] -> [EvVar]
forall a. a -> [a] -> [a]
:[EvVar]
glbls, [ABExport]
exports)
                Maybe EvVar
Nothing   -> do export <- EvVar -> IOEnv (Env DsGblEnv DsLclEnv) ABExport
mk_export EvVar
lcl
                                let glbl = ABExport -> EvVar
abe_poly ABExport
export
                                return (glbl:glbls, export:exports))
            ([],[]) [EvVar]
lcls

    mk_export :: EvVar -> IOEnv (Env DsGblEnv DsLclEnv) ABExport
mk_export EvVar
local =
      do global <- Type -> DsM EvVar
newSysLocalMDs
                     (HasDebugCallStack => CoreExpr -> Type
CoreExpr -> Type
exprType ([EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
tyvars ([EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
dicts (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
local))))
         return (ABE { abe_poly  = global
                     , abe_mono  = local
                     , abe_wrap  = WpHole
                     , abe_prags = 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)
          NoInline  {}     -> (EvVar
gbl_id, CoreExpr
rhs)
          Opaque    {}     -> (EvVar
gbl_id, CoreExpr
rhs)
          Inlinable {}     -> (EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` Unfolding
inlinable_unf, CoreExpr
rhs)
          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 -> UnfoldingSource -> CoreExpr -> Unfolding
mkInlinableUnfolding SimpleOpts
simpl_opts UnfoldingSource
StableUserSrc 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 Arity -> Arity -> Arity
forall a. Num a => a -> a -> a
+ Arity
arity
        -- NB: The arity passed to mkInlineUnfoldingWithArity
        --     must take account of the dictionaries
       = ( EvVar
gbl_id EvVar -> Unfolding -> EvVar
`setIdUnfolding` SimpleOpts -> UnfoldingSource -> Arity -> CoreExpr -> Unfolding
mkInlineUnfoldingWithArity SimpleOpts
simpl_opts UnfoldingSource
StableUserSrc Arity
real_arity CoreExpr
rhs
         , Arity -> CoreExpr -> CoreExpr
etaExpand Arity
real_arity CoreExpr
rhs)

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

dictArity :: [Var] -> Arity
-- Don't count coercion variables in arity
dictArity :: [EvVar] -> Arity
dictArity [EvVar]
dicts = (EvVar -> Bool) -> [EvVar] -> Arity
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 [The no-tyvar no-dict case]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we are desugaring
    AbsBinds { tyvars   = []
             , dicts    = []
             , exports  = [ ABE f fm, ABE g gm ]
             , binds    = B
             , ev_binds = EB }
That is: no type variables or dictionary abstractions.  Here, `f` and `fm` are
the polymorphic and monomorphic versions of `f`; in this special case they will
both have the same type.

Specialising Note [Desugaring AbsBinds] for this case gives the desugaring

    tup = letrec EB' in letrec B' in (fm,gm)
    f = case tup of { (fm,gm) -> fm }
    g = case tup of { (fm,gm) -> fm }

where B' is the result of desugaring B. This desugaring is a little silly: we
don't need the intermediate tuple (contrast with the general case where fm and f
have different types). So instead, in this case, we desugar to

    EB'; B'; f=fm; g=gm

This is done in the `null tyvars, null dicts` case of `dsAbsBinds`.

But there is a wrinkle (DSB1).  If the original binding group was
/non-recursive/, we want to return a bunch of non-recursive bindings in
dependency order: see Note [Return non-recursive bindings in dependency order].

But there is no guarantee that EB', the desugared evidence bindings, will be
non-recursive.  Happily, in the non-recursive case, B will have just a single
binding (f = rhs), so we can wrap EB' around its RHS, thus:

   fm = letrec EB' in rhs; f = fm

There is a sub-wrinkle (DSB2).  If B is a /pattern/ bindings, it will desugar to
a "main" binding followed by a bunch of selectors. The main binding always
comes first, so we can pick it out and wrap EB' around its RHS.  For example

    AbsBinds { tyvars   = []
             , dicts    = []
             , exports  = [ ABE p pm, ABE q qm ]
             , binds    = PatBind (pm, Just qm) rhs
             , ev_binds = EB }

can desguar to

   pt = let EB' in
        case rhs of
          (pm,Just qm) -> (pm,qm)
   pm = case pt of (pm,qm) -> pm
   qm = case pt of (pm,qm) -> qm

   p = pm
   q = qm

The first three bindings come from desugaring the PatBind, and subsequently
wrapping the RHS of the main binding in EB'.

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 preemptively 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 unfolding 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.

Wrinkle 1: forcing linear variables

Consider

  let %1 !x = rhs in <body>
==>
  let x = rhs in x `seq` <body>

In the desugared version x is used in both arguments of seq. This isn't
recognised a linear. So we can't strictly speaking use seq. Instead, the code is
really desugared as

  let x = rhs in case x of x { _ -> <body> }

The shadowing with the case-binder is crucial. The linear linter (see
Note [Linting linearity] in GHC.Core.Lint) understands this as linear. This is
what the seqVar function does.

To be more precise, suppose x has multiplicity p, the fully annotated seqVar (in
Core, p is really stored inside x) is

  case x of %p x { _ -> <body> }

In linear Core, case u of %p y { _ -> v } consumes u with multiplicity p, and
makes y available with multiplicity p in v. Which is exactly what we want.

Wrinkle 2: linear patterns

Consider the following linear binding (linear lets are always non-recursive):

  let
     %1 f : g = rhs
  in <body>

The general case would desugar it to

  let t = let tm = rhs
              fm = case tm of fm:_ -> fm
              gm = case tm of _:gm -> gm
           in
           (tm, fm, gm)

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

But all the case expression drop variables, which is prohibited by
linearity. But because this is a non-recursive let (in particular we're
desugaring a single binding), we can (and do) desugar the binding as a simple
case-expression instead:

  case rhs of {
    (f:g) -> <body>
  }

This is handled by the special case: a non-recursive PatBind in
GHC.HsToCore.Expr.ds_val_bind.

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 representation 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 = (OrdList (EvVar, CoreExpr), [CoreRule])
-> DsM (OrdList (EvVar, CoreExpr), [CoreRule])
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (OrdList (EvVar, CoreExpr)
forall a. OrdList a
nilOL, [])
dsSpecs CoreExpr
poly_rhs (SpecPrags [LTcSpecPrag]
sps)
  = do { pairs <- (LTcSpecPrag
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      (Maybe (OrdList (EvVar, CoreExpr), CoreRule)))
-> [LTcSpecPrag]
-> IOEnv
     (Env DsGblEnv DsLclEnv) [(OrdList (EvVar, CoreExpr), CoreRule)]
forall (m :: * -> *) a b.
Applicative m =>
(a -> m (Maybe b)) -> [a] -> m [b]
mapMaybeM (Maybe CoreExpr
-> LTcSpecPrag
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
dsSpec (CoreExpr -> Maybe CoreExpr
forall a. a -> Maybe a
Just CoreExpr
poly_rhs)) [LTcSpecPrag]
sps
       ; let (spec_binds_s, rules) = unzip pairs
       ; return (concatOL spec_binds_s, 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
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
dsSpec Maybe CoreExpr
mb_poly_rhs (L SrcSpan
loc (SpecPrag EvVar
poly_id HsWrapper
spec_co InlinePragma
spec_inl))
  | Maybe Class -> Bool
forall a. Maybe a -> Bool
isJust (EvVar -> Maybe Class
isClassOpId_maybe EvVar
poly_id)
  = SrcSpan
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc (IOEnv
   (Env DsGblEnv DsLclEnv)
   (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      (Maybe (OrdList (EvVar, CoreExpr), CoreRule)))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a b. (a -> b) -> a -> b
$
    do { DsMessage -> IOEnv (Env DsGblEnv DsLclEnv) ()
diagnosticDs (EvVar -> DsMessage
DsUselessSpecialiseForClassMethodSelector EvVar
poly_id)
       ; Maybe (OrdList (EvVar, CoreExpr), CoreRule)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (OrdList (EvVar, CoreExpr), CoreRule)
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
  = SrcSpan
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc (IOEnv
   (Env DsGblEnv DsLclEnv)
   (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      (Maybe (OrdList (EvVar, CoreExpr), CoreRule)))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a b. (a -> b) -> a -> b
$
    do { DsMessage -> IOEnv (Env DsGblEnv DsLclEnv) ()
diagnosticDs (EvVar -> DsMessage
DsUselessSpecialiseForNoInlineFunction EvVar
poly_id)
       ; Maybe (OrdList (EvVar, CoreExpr), CoreRule)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (OrdList (EvVar, CoreExpr), CoreRule)
forall a. Maybe a
Nothing  }  -- Function is NOINLINE, and the specialisation inherits that
                            -- See Note [Activation pragmas for SPECIALISE]

  | Bool
otherwise
  = SrcSpan
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. SrcSpan -> DsM a -> DsM a
putSrcSpanDs SrcSpan
loc (IOEnv
   (Env DsGblEnv DsLclEnv)
   (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
 -> IOEnv
      (Env DsGblEnv DsLclEnv)
      (Maybe (OrdList (EvVar, CoreExpr), CoreRule)))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a b. (a -> b) -> a -> b
$
    do { uniq <- TcRnIf DsGblEnv DsLclEnv Unique
forall gbl lcl. TcRnIf gbl lcl Unique
newUnique
       ; let poly_name = EvVar -> Name
idName EvVar
poly_id
             spec_occ  = OccName -> OccName
mkSpecOcc (Name -> OccName
forall a. NamedThing a => a -> OccName
getOccName Name
poly_name)
             spec_name = Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
uniq OccName
spec_occ (Name -> SrcSpan
forall a. NamedThing a => a -> SrcSpan
getSrcSpan Name
poly_name)
             (spec_bndrs, spec_app) = collectHsWrapBinders 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

       ; dsHsWrapper spec_app $ \CoreExpr -> CoreExpr
core_app -> do

       { let ds_lhs :: CoreExpr
ds_lhs  = CoreExpr -> CoreExpr
core_app (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
poly_id)
             spec_ty :: Type
spec_ty = [EvVar] -> Type -> Type
mkLamTypes [EvVar]
spec_bndrs (HasDebugCallStack => CoreExpr -> Type
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 ]) $
         dflags <- IOEnv (Env DsGblEnv DsLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; case decomposeRuleLhs dflags spec_bndrs ds_lhs (mkVarSet spec_bndrs) of {
           Left DsMessage
msg -> do { DsMessage -> IOEnv (Env DsGblEnv DsLclEnv) ()
diagnosticDs DsMessage
msg; Maybe (OrdList (EvVar, CoreExpr), CoreRule)
-> IOEnv
     (Env DsGblEnv DsLclEnv)
     (Maybe (OrdList (EvVar, CoreExpr), CoreRule))
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (OrdList (EvVar, CoreExpr), CoreRule)
forall a. Maybe a
Nothing } ;
           Right ([EvVar]
rule_bndrs, EvVar
_fn, [CoreExpr]
rule_lhs_args) -> do

       { this_mod <- IOEnv (Env DsGblEnv DsLclEnv) Module
forall (m :: * -> *). HasModule m => m Module
getModule
       ; let fn_unf    = EvVar -> Unfolding
realIdUnfolding EvVar
poly_id
             simpl_opts = DynFlags -> SimpleOpts
initSimpleOpts DynFlags
dflags
             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    = HasDebugCallStack => Name -> Type -> Type -> EvVar
Name -> Type -> Type -> EvVar
mkLocalId Name
spec_name Type
ManyTy Type
spec_ty -- Specialised binding is toplevel, hence Many.
                            EvVar -> InlinePragma -> EvVar
`setInlinePragma` InlinePragma
inl_prag
                            EvVar -> Unfolding -> EvVar
`setIdUnfolding`  Unfolding
spec_unf

             rule = DynFlags
-> Module
-> Bool
-> Activation
-> SDoc
-> EvVar
-> [EvVar]
-> [CoreExpr]
-> CoreExpr
-> CoreRule
mkSpecRule DynFlags
dflags Module
this_mod Bool
False Activation
rule_act (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"USPEC")
                               EvVar
poly_id [EvVar]
rule_bndrs [CoreExpr]
rule_lhs_args
                               (CoreExpr -> [EvVar] -> CoreExpr
forall b. Expr b -> [EvVar] -> Expr b
mkVarApps (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
spec_id) [EvVar]
spec_bndrs)
             spec_rhs = [EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams [EvVar]
spec_bndrs (CoreExpr -> CoreExpr
core_app CoreExpr
poly_rhs)

       ; dsWarnOrphanRule rule

       ; tracePm "dsSpec" (vcat
            [ text "fun:" <+> ppr poly_id
            , text "spec_co:" <+> ppr spec_co
            , text "spec_bndrs:" <+>  ppr spec_bndrs
            , text "ds_lhs:" <+> ppr ds_lhs
            , text "args:" <+>  ppr rule_lhs_args ])
       ; return (Just (unitOL (spec_id, spec_rhs), 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 = Maybe CoreExpr -> Bool
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 = String -> SDoc -> CoreExpr
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"dsImpSpecs" (EvVar -> SDoc
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
                    NoInline SourceText
_   -> Activation -> Bool
isNeverActive  Activation
spec_prag_act
                    Opaque SourceText
_     -> 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


dsWarnOrphanRule :: CoreRule -> DsM ()
dsWarnOrphanRule :: CoreRule -> IOEnv (Env DsGblEnv DsLclEnv) ()
dsWarnOrphanRule CoreRule
rule
  = Bool
-> IOEnv (Env DsGblEnv DsLclEnv) ()
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (CoreRule -> Bool
ruleIsOrphan CoreRule
rule) (IOEnv (Env DsGblEnv DsLclEnv) ()
 -> IOEnv (Env DsGblEnv DsLclEnv) ())
-> IOEnv (Env DsGblEnv DsLclEnv) ()
-> IOEnv (Env DsGblEnv DsLclEnv) ()
forall a b. (a -> b) -> a -> b
$
    DsMessage -> IOEnv (Env DsGblEnv DsLclEnv) ()
diagnosticDs (CoreRule -> DsMessage
DsOrphanRule 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
                 -> VarSet   -- Free vars of the RHS
                 -> Either DsMessage ([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 on rule LHS])
--
-- 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
-> VarSet
-> Either DsMessage ([EvVar], EvVar, [CoreExpr])
decomposeRuleLhs DynFlags
dflags [EvVar]
orig_bndrs CoreExpr
orig_lhs VarSet
rhs_fvs
  | Var EvVar
funId <- CoreExpr
fun2
  , Just DataCon
con <- EvVar -> Maybe DataCon
isDataConId_maybe EvVar
funId
  = DsMessage -> Either DsMessage ([EvVar], EvVar, [CoreExpr])
forall a b. a -> Either a b
Left (DataCon -> DsMessage
DsRuleIgnoredDueToConstructor DataCon
con) -- See Note [No RULES on datacons]

  | Bool
otherwise = case CoreExpr -> [CoreExpr] -> Maybe (EvVar, [CoreExpr])
decompose CoreExpr
fun2 [CoreExpr]
args2 of
        Maybe (EvVar, [CoreExpr])
Nothing -> -- pprTrace "decomposeRuleLhs 3" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
                   --                                    , text "orig_lhs:" <+> ppr orig_lhs
                   --                                    , text "rhs_fvs:" <+> ppr rhs_fvs
                   --                                    , text "orig_lhs:" <+> ppr orig_lhs
                   --                                    , text "lhs1:" <+> ppr lhs1
                   --                                    , text "lhs2:" <+> ppr lhs2
                   --                                    , text "fun2:" <+> ppr fun2
                   --                                    , text "args2:" <+> ppr args2
                   --                                    ]) $
                   DsMessage -> Either DsMessage ([EvVar], EvVar, [CoreExpr])
forall a b. a -> Either a b
Left (CoreExpr -> CoreExpr -> DsMessage
DsRuleLhsTooComplicated CoreExpr
orig_lhs CoreExpr
lhs2)
        Just (EvVar
fn_id, [CoreExpr]
args)
          | Bool -> Bool
not ([EvVar] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [EvVar]
unbound) ->
            -- Check for things unbound on LHS
            -- See Note [Unused spec binders]
            -- pprTrace "decomposeRuleLhs 1" (vcat [ text "orig_bndrs:" <+> ppr orig_bndrs
            --                                     , text "orig_lhs:" <+> ppr orig_lhs
            --                                     , text "lhs_fvs:" <+> ppr lhs_fvs
            --                                     , text "rhs_fvs:" <+> ppr rhs_fvs
            --                                     , text "unbound:" <+> ppr unbound
            --                                     ]) $
            DsMessage -> Either DsMessage ([EvVar], EvVar, [CoreExpr])
forall a b. a -> Either a b
Left ([EvVar] -> [EvVar] -> CoreExpr -> CoreExpr -> DsMessage
DsRuleBindersNotBound [EvVar]
unbound [EvVar]
orig_bndrs CoreExpr
orig_lhs CoreExpr
lhs2)
          | Bool
otherwise ->
            -- pprTrace "decomposeRuleLhs 2" (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
            --                                    , text "args fvs:" <+> ppr (exprsFreeVarsList args)
            --                                    ]) $
            ([EvVar], EvVar, [CoreExpr])
-> Either DsMessage ([EvVar], EvVar, [CoreExpr])
forall a b. b -> Either a b
Right ([EvVar]
trimmed_bndrs [EvVar] -> [EvVar] -> [EvVar]
forall a. [a] -> [a] -> [a]
++ [EvVar]
extra_bndrs, EvVar
fn_id, [CoreExpr]
args)

          where -- See Note [Variables unbound on the LHS]
                lhs_fvs :: VarSet
lhs_fvs = [CoreExpr] -> VarSet
exprsFreeVars [CoreExpr]
args
                all_fvs :: VarSet
all_fvs       = VarSet
lhs_fvs VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
rhs_fvs
                trimmed_bndrs :: [EvVar]
trimmed_bndrs = (EvVar -> Bool) -> [EvVar] -> [EvVar]
forall a. (a -> Bool) -> [a] -> [a]
filter (EvVar -> VarSet -> Bool
`elemVarSet` VarSet
all_fvs) [EvVar]
orig_bndrs
                unbound :: [EvVar]
unbound       = (EvVar -> Bool) -> [EvVar] -> [EvVar]
forall a. (a -> Bool) -> [a] -> [a]
filterOut (EvVar -> VarSet -> Bool
`elemVarSet` VarSet
lhs_fvs) [EvVar]
trimmed_bndrs
                    -- Needed on RHS but not bound on LHS

                -- Add extra tyvar binders: Note [Free tyvars on rule LHS]
                -- and extra dict binders: Note [Free dictionaries on rule LHS]
                extra_bndrs :: [EvVar]
extra_bndrs = [EvVar] -> [EvVar]
scopedSort [EvVar]
extra_tvs [EvVar] -> [EvVar] -> [EvVar]
forall a. [a] -> [a] -> [a]
++ [EvVar]
extra_dicts
                  where
                    extra_tvs :: [EvVar]
extra_tvs   = [ EvVar
v | EvVar
v <- [EvVar]
extra_vars, EvVar -> Bool
isTyVar EvVar
v ]

                -- isEvVar: this includes coercions, matching what
                --          happens in `split_lets` (isDictId, isCoVar)
                extra_dicts :: [EvVar]
extra_dicts =
                  [ HasDebugCallStack => Name -> Type -> Type -> EvVar
Name -> Type -> Type -> EvVar
mkLocalIdOrCoVar (Name -> Name
localiseName (EvVar -> Name
idName EvVar
d)) Type
ManyTy (EvVar -> Type
idType EvVar
d)
                    | EvVar
d <- [EvVar]
extra_vars, EvVar -> Bool
isEvVar EvVar
d ]
                extra_vars :: [EvVar]
extra_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 EvVar -> EvVar -> Bool
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)

 where
   simpl_opts :: SimpleOpts
simpl_opts    = DynFlags -> SimpleOpts
initSimpleOpts DynFlags
dflags
   orig_bndr_set :: VarSet
orig_bndr_set = [EvVar] -> VarSet
mkVarSet [EvVar]
orig_bndrs

   lhs1 :: CoreExpr
lhs1         = CoreExpr -> CoreExpr
drop_dicts CoreExpr
orig_lhs
   lhs2 :: CoreExpr
lhs2         = HasDebugCallStack => SimpleOpts -> CoreExpr -> CoreExpr
SimpleOpts -> CoreExpr -> CoreExpr
simpleOptExpr SimpleOpts
simpl_opts CoreExpr
lhs1  -- See Note [Simplify rule LHS]
   (CoreExpr
fun2,[CoreExpr]
args2) = CoreExpr -> (CoreExpr, [CoreExpr])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs CoreExpr
lhs2

   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)
      = (EvVar, [CoreExpr]) -> Maybe (EvVar, [CoreExpr])
forall a. a -> Maybe a
Just (EvVar
fn_id, [CoreExpr]
args)

   decompose CoreExpr
_ [CoreExpr]
_ = Maybe (EvVar, [CoreExpr])
forall a. Maybe a
Nothing

   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  -- Catches dictionaries, yes, but also catches dictionary
                   -- /functions/ arising from solving a
                   -- quantified contraint (#24370)
     = ((EvVar
d,CoreExpr
r)(EvVar, CoreExpr) -> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
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)(EvVar, CoreExpr) -> [(EvVar, CoreExpr)] -> [(EvVar, CoreExpr)]
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 (EvVar -> CoreExpr -> CoreBind
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 [Variables unbound on the LHS]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We obviously want to complain about
   RULE   forall x. f True = not x
because the forall'd variable `x` is not bound on the LHS.

It can be a bit delicate when dictionaries are involved.
Consider #22471
  {-# RULES "foo" forall (f :: forall a. [a] -> Int).
                  foo (\xs. 1 + f xs) = 2 + foo f #-}

We get two dicts on the LHS, one from `1` and one from `+`.
For reasons described in Note [The SimplifyRule Plan] in
GHC.Tc.Gen.Rule, we quantify separately over those dictionaries:
   forall f (d1::Num Int) (d2 :: Num Int).
   foo (\xs. (+) d1 (fromInteger d2 1) xs) = ...

Now the desugarer shortcircuits (fromInteger d2 1) to (I# 1); so d2 is
not mentioned at all (on LHS or RHS)! We don't want to complain about
and unbound d2.  Hence the trimmed_bndrs.

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 on rule LHS]

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.Zonk.Type 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.Zonk.Type".

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.

This relies on there not being any in-scope tyvars, which is true for
user-defined RULEs, which are always top-level.

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 a stable unfolding 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 (see Note [Unused 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
*                                                                      *
************************************************************************

Note [Desugaring WpFun]
~~~~~~~~~~~~~~~~~~~~~~~
See comments on WpFun in GHC.Tc.Types.Evidence for what WpFun means.
Roughly:

  (WpFun w_arg w_res)[ e ] = \x. w_res[ e w_arg[x] ]

This eta-expansion risk duplicating work, if `e` is not in HNF.
At one stage I thought we could avoid that by desugaring to
      let f = e in \x. w_res[ f w_arg[x] ]
But that /fundamentally/ doesn't work, because `w_res` may bind
evidence that is used in `e`.

This question arose when thinking about deep subsumption; see
https://github.com/ghc-proposals/ghc-proposals/pull/287#issuecomment-1125419649).
-}

dsHsWrappers :: [HsWrapper] -> ([CoreExpr -> CoreExpr] -> DsM a) -> DsM a
dsHsWrappers :: forall a. [HsWrapper] -> ([CoreExpr -> CoreExpr] -> DsM a) -> DsM a
dsHsWrappers (HsWrapper
wp:[HsWrapper]
wps) [CoreExpr -> CoreExpr] -> DsM a
k = HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper HsWrapper
wp (((CoreExpr -> CoreExpr) -> DsM a) -> DsM a)
-> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
wrap -> [HsWrapper] -> ([CoreExpr -> CoreExpr] -> DsM a) -> DsM a
forall a. [HsWrapper] -> ([CoreExpr -> CoreExpr] -> DsM a) -> DsM a
dsHsWrappers [HsWrapper]
wps (([CoreExpr -> CoreExpr] -> DsM a) -> DsM a)
-> ([CoreExpr -> CoreExpr] -> DsM a) -> DsM a
forall a b. (a -> b) -> a -> b
$ \[CoreExpr -> CoreExpr]
wraps -> [CoreExpr -> CoreExpr] -> DsM a
k (CoreExpr -> CoreExpr
wrap(CoreExpr -> CoreExpr)
-> [CoreExpr -> CoreExpr] -> [CoreExpr -> CoreExpr]
forall a. a -> [a] -> [a]
:[CoreExpr -> CoreExpr]
wraps)
dsHsWrappers []       [CoreExpr -> CoreExpr] -> DsM a
k = [CoreExpr -> CoreExpr] -> DsM a
k []

dsHsWrapper :: HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper :: forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
dsHsWrapper HsWrapper
hs_wrap (CoreExpr -> CoreExpr) -> DsM a
thing_inside
  = HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
ds_hs_wrapper HsWrapper
hs_wrap (((CoreExpr -> CoreExpr) -> DsM a) -> DsM a)
-> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
forall a b. (a -> b) -> a -> b
$ \ CoreExpr -> CoreExpr
core_wrap ->
    Origin -> Bag EvVar -> DsM a -> DsM a
forall a. Origin -> Bag EvVar -> DsM a -> DsM a
addTyCs Origin
FromSource (HsWrapper -> Bag EvVar
hsWrapDictBinders HsWrapper
hs_wrap) (DsM a -> DsM a) -> DsM a -> DsM a
forall a b. (a -> b) -> a -> b
$
       -- addTyCs: Add type evidence to the refinement type
       --            predicate of the coverage checker
       --   See Note [Long-distance information] in "GHC.HsToCore.Pmc"
       -- 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.
    (CoreExpr -> CoreExpr) -> DsM a
thing_inside CoreExpr -> CoreExpr
core_wrap

ds_hs_wrapper :: HsWrapper
              -> ((CoreExpr -> CoreExpr) -> DsM a)
              -> DsM a
ds_hs_wrapper :: forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
ds_hs_wrapper HsWrapper
wrap = HsWrapper
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) a)
-> IOEnv (Env DsGblEnv DsLclEnv) a
forall a. HsWrapper -> ((CoreExpr -> CoreExpr) -> DsM a) -> DsM a
go HsWrapper
wrap
  where
    go :: HsWrapper
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
go HsWrapper
WpHole            (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr
e
    go (WpTyApp Type
ty)      (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr -> CoreExpr -> CoreExpr
forall b. Expr b -> Expr b -> Expr b
App CoreExpr
e (Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty)
    go (WpEvLam EvVar
ev)      (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ EvVar -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam EvVar
ev
    go (WpTyLam EvVar
tv)      (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ EvVar -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam EvVar
tv
    go (WpCast TcCoercionR
co)       (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = Bool
-> IOEnv (Env DsGblEnv DsLclEnv) b
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a. HasCallStack => Bool -> a -> a
assert (TcCoercionR -> Role
coercionRole TcCoercionR
co Role -> Role -> Bool
forall a. Eq a => a -> a -> Bool
== Role
Representational) (IOEnv (Env DsGblEnv DsLclEnv) b
 -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$
                             (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr
e -> CoreExpr -> TcCoercionR -> CoreExpr
mkCastDs CoreExpr
e TcCoercionR
co
    go (WpEvApp EvTerm
tm)      (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = do { core_tm <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
tm
                                ; k $ \CoreExpr
e -> CoreExpr
e CoreExpr -> CoreExpr -> CoreExpr
forall b. Expr b -> Expr b -> Expr b
`App` CoreExpr
core_tm }
    go (WpLet TcEvBinds
ev_binds)  (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = TcEvBinds
-> ([CoreBind] -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a. TcEvBinds -> ([CoreBind] -> DsM a) -> DsM a
dsTcEvBinds TcEvBinds
ev_binds (([CoreBind] -> IOEnv (Env DsGblEnv DsLclEnv) b)
 -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> ([CoreBind] -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \[CoreBind]
bs ->
                             (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k ([CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
bs)
    go (WpCompose HsWrapper
c1 HsWrapper
c2) (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = HsWrapper
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
go HsWrapper
c1 (((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
 -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
w1 ->
                             HsWrapper
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
go HsWrapper
c2 (((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
 -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
w2 ->
                             (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k (CoreExpr -> CoreExpr
w1 (CoreExpr -> CoreExpr)
-> (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoreExpr -> CoreExpr
w2)
    go (WpFun HsWrapper
c1 HsWrapper
c2 Scaled Type
st)  (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k = -- See Note [Desugaring WpFun]
                             do { x <- Scaled Type -> DsM EvVar
newSysLocalDs Scaled Type
st
                                ; go c1 $ \CoreExpr -> CoreExpr
w1 ->
                                  HsWrapper
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
go HsWrapper
c2 (((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
 -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> ((CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b)
-> IOEnv (Env DsGblEnv DsLclEnv) b
forall a b. (a -> b) -> a -> b
$ \CoreExpr -> CoreExpr
w2 ->
                                  let app :: CoreExpr -> CoreExpr -> CoreExpr
app CoreExpr
f CoreExpr
a = SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreApp (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"dsHsWrapper") CoreExpr
f CoreExpr
a
                                      arg :: CoreExpr
arg     = CoreExpr -> CoreExpr
w1 (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
x)
                                  in (CoreExpr -> CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) b
k (\CoreExpr
e -> (EvVar -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam EvVar
x (CoreExpr -> CoreExpr
w2 (CoreExpr -> CoreExpr -> CoreExpr
app CoreExpr
e CoreExpr
arg)))) }

--------------------------------------
dsTcEvBinds_s :: [TcEvBinds] -> ([CoreBind] -> DsM a) -> DsM a
dsTcEvBinds_s :: forall a. [TcEvBinds] -> ([CoreBind] -> DsM a) -> DsM a
dsTcEvBinds_s []       [CoreBind] -> DsM a
k = [CoreBind] -> DsM a
k []
dsTcEvBinds_s (TcEvBinds
b:[TcEvBinds]
rest) [CoreBind] -> DsM a
k = Bool -> DsM a -> DsM a
forall a. HasCallStack => Bool -> a -> a
assert ([TcEvBinds] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcEvBinds]
rest) (DsM a -> DsM a) -> DsM a -> DsM a
forall a b. (a -> b) -> a -> b
$  -- Zonker ensures null
                           TcEvBinds -> ([CoreBind] -> DsM a) -> DsM a
forall a. TcEvBinds -> ([CoreBind] -> DsM a) -> DsM a
dsTcEvBinds TcEvBinds
b [CoreBind] -> DsM a
k

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

--   * Desugars the ev_binds, sorts them into dependency order, and
--     passes the resulting [CoreBind] to thing_inside
--   * Extends the DsM (dsl_unspecable field) with specialisability information
--     for each binder in ev_binds, before invoking thing_inside
dsEvBinds :: Bag EvBind -> ([CoreBind] -> DsM a) -> DsM a
dsEvBinds :: forall a. Bag EvBind -> ([CoreBind] -> DsM a) -> DsM a
dsEvBinds Bag EvBind
ev_binds [CoreBind] -> DsM a
thing_inside
  = do { ds_binds <- (EvBind
 -> IOEnv
      (Env DsGblEnv DsLclEnv) (EvVar, CanonicalEvidence, CoreExpr))
-> Bag EvBind
-> IOEnv
     (Env DsGblEnv DsLclEnv) (Bag (EvVar, CanonicalEvidence, CoreExpr))
forall (m :: * -> *) a b.
Monad m =>
(a -> m b) -> Bag a -> m (Bag b)
mapBagM EvBind
-> IOEnv
     (Env DsGblEnv DsLclEnv) (EvVar, CanonicalEvidence, CoreExpr)
dsEvBind Bag EvBind
ev_binds
       ; let comps = Bag (EvVar, CanonicalEvidence, CoreExpr)
-> [SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
sort_ev_binds Bag (EvVar, CanonicalEvidence, CoreExpr)
ds_binds
       ; go comps thing_inside }
  where
    go ::[SCC (Node EvVar (CanonicalEvidence, CoreExpr))] -> ([CoreBind] -> DsM a) -> DsM a
    go :: forall a.
[SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
-> ([CoreBind] -> DsM a) -> DsM a
go (SCC (Node EvVar (CanonicalEvidence, CoreExpr))
comp:[SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
comps) [CoreBind] -> DsM a
thing_inside
      = do { unspecables <- DsM (Set EvVar)
getUnspecables
           ; let (core_bind, new_unspecables) = ds_component unspecables comp
           ; addUnspecables new_unspecables $ go comps $ \ [CoreBind]
core_binds ->
               [CoreBind] -> DsM a
thing_inside (CoreBind
core_bindCoreBind -> [CoreBind] -> [CoreBind]
forall a. a -> [a] -> [a]
:[CoreBind]
core_binds) }
    go [] [CoreBind] -> DsM a
thing_inside = [CoreBind] -> DsM a
thing_inside []

    ds_component :: Set a
-> SCC (Node a (CanonicalEvidence, Expr a)) -> (Bind a, Set a)
ds_component Set a
unspecables (AcyclicSCC Node a (CanonicalEvidence, Expr a)
node) = (a -> Expr a -> Bind a
forall b. b -> Expr b -> Bind b
NonRec a
v Expr a
rhs, Set a
new_unspecables)
      where
        ((a
v, Expr a
rhs), (CanonicalEvidence
this_canonical, [a]
deps)) = Node a (CanonicalEvidence, Expr a)
-> ((a, Expr a), (CanonicalEvidence, [a]))
forall {a} {a} {b}. Node a (a, b) -> ((a, b), (a, [a]))
unpack_node Node a (CanonicalEvidence, Expr a)
node
        transitively_unspecable :: Bool
transitively_unspecable = CanonicalEvidence -> Bool
is_unspecable CanonicalEvidence
this_canonical Bool -> Bool -> Bool
|| (a -> Bool) -> [a] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any a -> Bool
is_unspecable_dep [a]
deps
        is_unspecable_dep :: a -> Bool
is_unspecable_dep a
dep = a
dep a -> Set a -> Bool
forall a. Ord a => a -> Set a -> Bool
`S.member` Set a
unspecables
        new_unspecables :: Set a
new_unspecables
            | Bool
transitively_unspecable = a -> Set a
forall a. a -> Set a
S.singleton a
v
            | Bool
otherwise = Set a
forall a. Monoid a => a
mempty
    ds_component Set a
unspecables (CyclicSCC [Node a (CanonicalEvidence, Expr a)]
nodes) = ([(a, Expr a)] -> Bind a
forall b. [(b, Expr b)] -> Bind b
Rec [(a, Expr a)]
pairs, Set a
new_unspecables)
      where
        ([(a, Expr a)]
pairs, [(CanonicalEvidence, [a])]
direct_canonicity) = [((a, Expr a), (CanonicalEvidence, [a]))]
-> ([(a, Expr a)], [(CanonicalEvidence, [a])])
forall a b. [(a, b)] -> ([a], [b])
unzip ([((a, Expr a), (CanonicalEvidence, [a]))]
 -> ([(a, Expr a)], [(CanonicalEvidence, [a])]))
-> [((a, Expr a), (CanonicalEvidence, [a]))]
-> ([(a, Expr a)], [(CanonicalEvidence, [a])])
forall a b. (a -> b) -> a -> b
$ (Node a (CanonicalEvidence, Expr a)
 -> ((a, Expr a), (CanonicalEvidence, [a])))
-> [Node a (CanonicalEvidence, Expr a)]
-> [((a, Expr a), (CanonicalEvidence, [a]))]
forall a b. (a -> b) -> [a] -> [b]
map Node a (CanonicalEvidence, Expr a)
-> ((a, Expr a), (CanonicalEvidence, [a]))
forall {a} {a} {b}. Node a (a, b) -> ((a, b), (a, [a]))
unpack_node [Node a (CanonicalEvidence, Expr a)]
nodes

        is_unspecable_remote :: a -> Bool
is_unspecable_remote a
dep = a
dep a -> Set a -> Bool
forall a. Ord a => a -> Set a -> Bool
`S.member` Set a
unspecables
        transitively_unspecable :: Bool
transitively_unspecable = [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [ CanonicalEvidence -> Bool
is_unspecable CanonicalEvidence
this_canonical Bool -> Bool -> Bool
|| (a -> Bool) -> [a] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any a -> Bool
is_unspecable_remote [a]
deps
                                     | (CanonicalEvidence
this_canonical, [a]
deps) <- [(CanonicalEvidence, [a])]
direct_canonicity ]
            -- Bindings from a given SCC are transitively specialisable if
            -- all are specialisable and all their remote dependencies are
            -- also specialisable; see Note [Desugaring non-canonical evidence]

        new_unspecables :: Set a
new_unspecables
            | Bool
transitively_unspecable = [a] -> Set a
forall a. Ord a => [a] -> Set a
S.fromList [ a
v | (a
v, Expr a
_) <- [(a, Expr a)]
pairs]
            | Bool
otherwise = Set a
forall a. Monoid a => a
mempty

    unpack_node :: Node a (a, b) -> ((a, b), (a, [a]))
unpack_node DigraphNode { node_key :: forall key payload. Node key payload -> key
node_key = a
v, node_payload :: forall key payload. Node key payload -> payload
node_payload = (a
canonical, b
rhs), node_dependencies :: forall key payload. Node key payload -> [key]
node_dependencies = [a]
deps }
       = ((a
v, b
rhs), (a
canonical, [a]
deps))

    is_unspecable :: CanonicalEvidence -> Bool
    is_unspecable :: CanonicalEvidence -> Bool
is_unspecable CanonicalEvidence
EvNonCanonical = Bool
True
    is_unspecable CanonicalEvidence
EvCanonical    = Bool
False

sort_ev_binds :: Bag (Id, CanonicalEvidence, CoreExpr) -> [SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
-- 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.
sort_ev_binds :: Bag (EvVar, CanonicalEvidence, CoreExpr)
-> [SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
sort_ev_binds Bag (EvVar, CanonicalEvidence, CoreExpr)
ds_binds = [Node EvVar (CanonicalEvidence, CoreExpr)]
-> [SCC (Node EvVar (CanonicalEvidence, CoreExpr))]
forall key payload.
Uniquable key =>
[Node key payload] -> [SCC (Node key payload)]
stronglyConnCompFromEdgedVerticesUniqR [Node EvVar (CanonicalEvidence, CoreExpr)]
edges
  where
    edges :: [ Node EvVar (CanonicalEvidence, CoreExpr) ]
    edges :: [Node EvVar (CanonicalEvidence, CoreExpr)]
edges = ((EvVar, CanonicalEvidence, CoreExpr)
 -> [Node EvVar (CanonicalEvidence, CoreExpr)]
 -> [Node EvVar (CanonicalEvidence, CoreExpr)])
-> [Node EvVar (CanonicalEvidence, CoreExpr)]
-> Bag (EvVar, CanonicalEvidence, CoreExpr)
-> [Node EvVar (CanonicalEvidence, CoreExpr)]
forall a b. (a -> b -> b) -> b -> Bag a -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ((:) (Node EvVar (CanonicalEvidence, CoreExpr)
 -> [Node EvVar (CanonicalEvidence, CoreExpr)]
 -> [Node EvVar (CanonicalEvidence, CoreExpr)])
-> ((EvVar, CanonicalEvidence, CoreExpr)
    -> Node EvVar (CanonicalEvidence, CoreExpr))
-> (EvVar, CanonicalEvidence, CoreExpr)
-> [Node EvVar (CanonicalEvidence, CoreExpr)]
-> [Node EvVar (CanonicalEvidence, CoreExpr)]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (EvVar, CanonicalEvidence, CoreExpr)
-> Node EvVar (CanonicalEvidence, CoreExpr)
mk_node) [] Bag (EvVar, CanonicalEvidence, CoreExpr)
ds_binds

    mk_node :: (Id, CanonicalEvidence, CoreExpr) -> Node EvVar (CanonicalEvidence, CoreExpr)
    mk_node :: (EvVar, CanonicalEvidence, CoreExpr)
-> Node EvVar (CanonicalEvidence, CoreExpr)
mk_node (EvVar
var, CanonicalEvidence
canonical, CoreExpr
rhs)
      = DigraphNode { node_payload :: (CanonicalEvidence, CoreExpr)
node_payload = (CanonicalEvidence
canonical, CoreExpr
rhs)
                    , node_key :: EvVar
node_key = EvVar
var
                    , node_dependencies :: [EvVar]
node_dependencies = VarSet -> [EvVar]
forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet (VarSet -> [EvVar]) -> VarSet -> [EvVar]
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 graphFromEdgedVerticesUniq
      -- is still deterministic even if the edges are in nondeterministic order
      -- as explained in Note [Deterministic SCC] in GHC.Data.Graph.Directed.

dsEvBind :: EvBind -> DsM (Id, CanonicalEvidence, CoreExpr)
dsEvBind :: EvBind
-> IOEnv
     (Env DsGblEnv DsLclEnv) (EvVar, CanonicalEvidence, CoreExpr)
dsEvBind (EvBind { eb_lhs :: EvBind -> EvVar
eb_lhs = EvVar
v, eb_rhs :: EvBind -> EvTerm
eb_rhs = EvTerm
r, eb_info :: EvBind -> EvBindInfo
eb_info = EvBindInfo
info }) = do
    e <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
r
    let canonical = case EvBindInfo
info of
            EvBindGiven{} -> CanonicalEvidence
EvCanonical
            EvBindWanted{ ebi_canonical :: EvBindInfo -> CanonicalEvidence
ebi_canonical = CanonicalEvidence
canonical } -> CanonicalEvidence
canonical
    return (v, canonical, e)


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

dsEvTerm :: EvTerm -> DsM CoreExpr
dsEvTerm :: EvTerm -> DsM CoreExpr
dsEvTerm (EvExpr CoreExpr
e)          = CoreExpr -> DsM CoreExpr
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
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 { TcEvBinds -> ([CoreBind] -> DsM CoreExpr) -> DsM CoreExpr
forall a. TcEvBinds -> ([CoreBind] -> DsM a) -> DsM a
dsTcEvBinds TcEvBinds
ev_binds (([CoreBind] -> DsM CoreExpr) -> DsM CoreExpr)
-> ([CoreBind] -> DsM CoreExpr) -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ \[CoreBind]
ds_ev_binds -> do
       { CoreExpr -> DsM CoreExpr
forall a. a -> IOEnv (Env DsGblEnv DsLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> DsM CoreExpr) -> CoreExpr -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ ([EvVar] -> CoreExpr -> CoreExpr
forall b. [b] -> Expr b -> Expr b
mkLams ([EvVar]
tvs [EvVar] -> [EvVar] -> [EvVar]
forall a. [a] -> [a] -> [a]
++ [EvVar]
given) (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                   [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_ev_binds (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                   EvVar -> CoreExpr
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 { tyCl <- Name -> DsM TyCon
dsLookupTyCon Name
typeableClassName    -- Typeable
       ; let kind = HasDebugCallStack => Type -> Type
Type -> Type
typeKind Type
ty
             typeable_data_con = TyCon -> DataCon
tyConSingleDataCon TyCon
tyCl  -- "Data constructor"
                                                    -- for Typeable

       ; rep_expr <- ds_ev_typeable ty ev           -- :: TypeRep a

       -- Package up the method as `Typeable` dictionary
       ; return $ mkConApp typeable_data_con [Type kind, Type ty, 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 { mkTrCon <- Name -> DsM EvVar
dsLookupGlobalId Name
mkTrConName
                    -- mkTrCon :: forall k (a :: k). TyCon -> TypeRep k -> TypeRep a
       ; someTypeRepTyCon <- dsLookupTyCon someTypeRepTyConName
       ; someTypeRepDataCon <- dsLookupDataCon someTypeRepDataConName
                    -- SomeTypeRep :: forall k (a :: k). TypeRep a -> SomeTypeRep

       ; tc_rep <- tyConRep tc                      -- :: TyCon
       ; let ks = HasDebugCallStack => Type -> [Type]
Type -> [Type]
tyConAppArgs Type
ty
             -- Construct a SomeTypeRep
             toSomeTypeRep :: Type -> EvTerm -> DsM CoreExpr
             toSomeTypeRep Type
t EvTerm
ev = do
                 rep <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev Type
t
                 return $ mkCoreConApps someTypeRepDataCon [Type (typeKind t), Type t, rep]
       ; kind_arg_reps <- sequence $ zipWith toSomeTypeRep ks kind_ev   -- :: TypeRep t
       ; let -- :: [SomeTypeRep]
             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 -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (EvVar -> CoreExpr
forall b. EvVar -> Expr b
Var EvVar
mkTrCon) [ Type -> CoreExpr
forall b. Type -> Expr b
Type (HasDebugCallStack => Type -> Type
Type -> Type
typeKind Type
ty)
                                         , Type -> CoreExpr
forall b. Type -> Expr b
Type Type
ty
                                         , CoreExpr
tc_rep
                                         , CoreExpr
kind_args ]
       -- ; pprRuntimeTrace "Trace mkTrTyCon" (ppr expr) expr
       ; return 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 { e1  <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev1 Type
t1
       ; e2  <- getRep ev2 t2
       ; mkTrApp <- dsLookupGlobalId mkTrAppName
                    -- mkTrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1).
                    --            TypeRep a -> TypeRep b -> TypeRep (a b)
       ; let (_, k1, k2) = splitFunTy (typeKind t1)  -- drop the multiplicity,
                                                     -- since it's a kind
       ; let expr =  CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (CoreExpr -> [Type] -> CoreExpr
forall b. Expr b -> [Type] -> Expr b
mkTyApps (EvVar -> CoreExpr
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
       ; return expr
       }

ds_ev_typeable Type
ty (EvTypeableTrFun EvTerm
evm EvTerm
ev1 EvTerm
ev2)
  | Just (FunTyFlag
_af,Type
m,Type
t1,Type
t2) <- Type -> Maybe (FunTyFlag, Type, Type, Type)
splitFunTy_maybe Type
ty
  = do { e1 <- EvTerm -> Type -> DsM CoreExpr
getRep EvTerm
ev1 Type
t1
       ; e2 <- getRep ev2 t2
       ; em <- getRep evm m
       ; mkTrFun <- dsLookupGlobalId 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 = HasDebugCallStack => Type -> Type
Type -> Type
getRuntimeRep Type
t1
             r2 = HasDebugCallStack => Type -> Type
Type -> Type
getRuntimeRep Type
t2
       ; return $ mkApps (mkTyApps (Var mkTrFun) [m, r1, r2, t1, t2])
                         [ em, e1, e2 ]
       }

ds_ev_typeable Type
ty (EvTypeableTyLit EvTerm
ev)
  = -- See Note [Typeable for Nat and Symbol] in GHC.Tc.Instance.Class
    do { fun  <- Name -> DsM EvVar
dsLookupGlobalId Name
tr_fun
       ; dict <- dsEvTerm ev       -- Of type KnownNat/KnownSymbol
       ; return (mkApps (mkTyApps (Var fun) [ty]) [ dict ]) }
  where
    ty_kind :: Type
ty_kind = HasDebugCallStack => Type -> Type
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 HasCallStack => Type -> Type -> Bool
Type -> Type -> Bool
`eqType` Type
naturalTy      = Name
typeNatTypeRepName
           | Type
ty_kind HasCallStack => Type -> Type -> Bool
Type -> Type -> Bool
`eqType` Type
typeSymbolKind = Name
typeSymbolTypeRepName
           | Type
ty_kind HasCallStack => Type -> Type -> Bool
Type -> Type -> Bool
`eqType` Type
charTy         = Name
typeCharTypeRepName
           | Bool
otherwise = String -> Name
forall a. HasCallStack => String -> a
panic String
"dsEvTypeable: unknown type lit kind"

ds_ev_typeable Type
ty EvTypeable
ev
  = String -> SDoc -> DsM CoreExpr
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"dsEvTypeable" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$ EvTypeable -> 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 { typeable_expr <- EvTerm -> DsM CoreExpr
dsEvTerm EvTerm
ev
       ; typeRepId     <- dsLookupGlobalId typeRepIdName
       ; let ty_args = [HasDebugCallStack => Type -> Type
Type -> Type
typeKind Type
ty, Type
ty]
       ; return (mkApps (mkTyApps (Var typeRepId) ty_args) [ 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 { tc_rep_id <- Name -> DsM EvVar
dsLookupGlobalId Name
tc_rep_nm
       ; return (Var tc_rep_id) }
  | Bool
otherwise
  = String -> SDoc -> DsM CoreExpr
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"tyConRep" (TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc)