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


Utilities for desugaring

This module exports some utility functions of no great interest.
-}

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

-- | Utility functions for constructing Core syntax, principally for desugaring
module GHC.HsToCore.Utils (
        EquationInfo(..),
        firstPat, shiftEqns,

        MatchResult (..), CaseAlt(..),
        cantFailMatchResult, alwaysFailMatchResult,
        extractMatchResult, combineMatchResults,
        adjustMatchResultDs,
        shareFailureHandler,
        mkCoLetMatchResult, mkViewMatchResult, mkGuardedMatchResult,
        matchCanFail, mkEvalMatchResult,
        mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult, mkCoSynCaseMatchResult,
        wrapBind, wrapBinds,

        mkErrorAppDs, mkCoreAppDs, mkCoreAppsDs, mkCastDs,

        seqVar,

        -- LHs tuples
        mkLHsPatTup, mkVanillaTuplePat,
        mkBigLHsVarTupId, mkBigLHsTupId, mkBigLHsVarPatTupId, mkBigLHsPatTupId,

        mkSelectorBinds,

        selectSimpleMatchVarL, selectMatchVars, selectMatchVar,
        mkOptTickBox, mkBinaryTickBox, decideBangHood,
        isTrueLHsExpr
    ) where

#include "HsVersions.h"

import GHC.Prelude

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

import GHC.Hs
import GHC.Tc.Utils.Zonk
import GHC.Tc.Utils.TcType( tcSplitTyConApp )
import GHC.Core
import GHC.HsToCore.Monad

import GHC.Core.Utils
import GHC.Core.Make
import GHC.Types.Id.Make
import GHC.Types.Id
import GHC.Types.Literal
import GHC.Core.TyCon
import GHC.Core.DataCon
import GHC.Core.PatSyn
import GHC.Core.Type
import GHC.Core.Coercion
import GHC.Builtin.Types.Prim
import GHC.Builtin.Types
import GHC.Types.Basic
import GHC.Core.ConLike
import GHC.Types.Unique.Set
import GHC.Types.Unique.Supply
import GHC.Unit.Module
import GHC.Builtin.Names
import GHC.Types.Name( isInternalName )
import GHC.Utils.Outputable
import GHC.Types.SrcLoc
import GHC.Utils.Misc
import GHC.Driver.Session
import GHC.Data.FastString
import qualified GHC.LanguageExtensions as LangExt

import GHC.Tc.Types.Evidence

import Control.Monad    ( zipWithM )
import Data.List.NonEmpty (NonEmpty(..))
import Data.Maybe (maybeToList)
import qualified Data.List.NonEmpty as NEL

{-
************************************************************************
*                                                                      *
\subsection{ Selecting match variables}
*                                                                      *
************************************************************************

We're about to match against some patterns.  We want to make some
@Ids@ to use as match variables.  If a pattern has an @Id@ readily at
hand, which should indeed be bound to the pattern as a whole, then use it;
otherwise, make one up. The multiplicity argument is chosen as the multiplicity
of the variable if it is made up.
-}

selectSimpleMatchVarL :: Mult -> LPat GhcTc -> DsM Id
-- Postcondition: the returned Id has an Internal Name
selectSimpleMatchVarL :: Mult -> XRec (GhcPass 'Typechecked) Pat -> DsM Id
selectSimpleMatchVarL Mult
w XRec (GhcPass 'Typechecked) Pat
pat = Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar Mult
w (GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Pat (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
pat)

-- (selectMatchVars ps tys) chooses variables of type tys
-- to use for matching ps against.  If the pattern is a variable,
-- we try to use that, to save inventing lots of fresh variables.
--
-- OLD, but interesting note:
--    But even if it is a variable, its type might not match.  Consider
--      data T a where
--        T1 :: Int -> T Int
--        T2 :: a   -> T a
--
--      f :: T a -> a -> Int
--      f (T1 i) (x::Int) = x
--      f (T2 i) (y::a)   = 0
--    Then we must not choose (x::Int) as the matching variable!
-- And nowadays we won't, because the (x::Int) will be wrapped in a CoPat

selectMatchVars :: [(Mult, Pat GhcTc)] -> DsM [Id]
-- Postcondition: the returned Ids have Internal Names
selectMatchVars :: [(Mult, Pat (GhcPass 'Typechecked))] -> DsM [Id]
selectMatchVars [(Mult, Pat (GhcPass 'Typechecked))]
ps = ((Mult, Pat (GhcPass 'Typechecked)) -> DsM Id)
-> [(Mult, Pat (GhcPass 'Typechecked))] -> DsM [Id]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ((Mult -> Pat (GhcPass 'Typechecked) -> DsM Id)
-> (Mult, Pat (GhcPass 'Typechecked)) -> DsM Id
forall a b c. (a -> b -> c) -> (a, b) -> c
uncurry Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar) [(Mult, Pat (GhcPass 'Typechecked))]
ps

selectMatchVar :: Mult -> Pat GhcTc -> DsM Id
-- Postcondition: the returned Id has an Internal Name
selectMatchVar :: Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar Mult
w (BangPat XBangPat (GhcPass 'Typechecked)
_ XRec (GhcPass 'Typechecked) Pat
pat) = Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar Mult
w (GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Pat (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
pat)
selectMatchVar Mult
w (LazyPat XLazyPat (GhcPass 'Typechecked)
_ XRec (GhcPass 'Typechecked) Pat
pat) = Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar Mult
w (GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Pat (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
pat)
selectMatchVar Mult
w (ParPat XParPat (GhcPass 'Typechecked)
_ XRec (GhcPass 'Typechecked) Pat
pat)  = Mult -> Pat (GhcPass 'Typechecked) -> DsM Id
selectMatchVar Mult
w (GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Pat (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
pat)
selectMatchVar Mult
_w (VarPat XVarPat (GhcPass 'Typechecked)
_ Located (IdP (GhcPass 'Typechecked))
var)  = Id -> DsM Id
forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> Id
localiseId (GenLocated SrcSpan Id -> Id
forall l e. GenLocated l e -> e
unLoc GenLocated SrcSpan Id
Located (IdP (GhcPass 'Typechecked))
var))
                                  -- Note [Localise pattern binders]
                                  --
                                  -- Remark: when the pattern is a variable (or
                                  -- an @-pattern), then w is the same as the
                                  -- multiplicity stored within the variable
                                  -- itself. It's easier to pull it from the
                                  -- variable, so we ignore the multiplicity.
selectMatchVar Mult
_w (AsPat XAsPat (GhcPass 'Typechecked)
_ Located (IdP (GhcPass 'Typechecked))
var XRec (GhcPass 'Typechecked) Pat
_) = ASSERT( isManyDataConTy _w ) (return (unLoc var))
selectMatchVar Mult
w Pat (GhcPass 'Typechecked)
other_pat     = Mult -> Mult -> DsM Id
newSysLocalDsNoLP Mult
w (Pat (GhcPass 'Typechecked) -> Mult
hsPatType Pat (GhcPass 'Typechecked)
other_pat)

{- Note [Localise pattern binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider     module M where
               [Just a] = e
After renaming it looks like
             module M where
               [Just M.a] = e

We don't generalise, since it's a pattern binding, monomorphic, etc,
so after desugaring we may get something like
             M.a = case e of (v:_) ->
                   case v of Just M.a -> M.a
Notice the "M.a" in the pattern; after all, it was in the original
pattern.  However, after optimisation those pattern binders can become
let-binders, and then end up floated to top level.  They have a
different *unique* by then (the simplifier is good about maintaining
proper scoping), but it's BAD to have two top-level bindings with the
External Name M.a, because that turns into two linker symbols for M.a.
It's quite rare for this to actually *happen* -- the only case I know
of is tc003 compiled with the 'hpc' way -- but that only makes it
all the more annoying.

To avoid this, we craftily call 'localiseId' in the desugarer, which
simply turns the External Name for the Id into an Internal one, but
doesn't change the unique.  So the desugarer produces this:
             M.a{r8} = case e of (v:_) ->
                       case v of Just a{r8} -> M.a{r8}
The unique is still 'r8', but the binding site in the pattern
is now an Internal Name.  Now the simplifier's usual mechanisms
will propagate that Name to all the occurrence sites, as well as
un-shadowing it, so we'll get
             M.a{r8} = case e of (v:_) ->
                       case v of Just a{s77} -> a{s77}
In fact, even GHC.Core.Subst.simplOptExpr will do this, and simpleOptExpr
runs on the output of the desugarer, so all is well by the end of
the desugaring pass.

See also Note [MatchIds] in GHC.HsToCore.Match

************************************************************************
*                                                                      *
* type synonym EquationInfo and access functions for its pieces        *
*                                                                      *
************************************************************************
\subsection[EquationInfo-synonym]{@EquationInfo@: a useful synonym}

The ``equation info'' used by @match@ is relatively complicated and
worthy of a type synonym and a few handy functions.
-}

firstPat :: EquationInfo -> Pat GhcTc
firstPat :: EquationInfo -> Pat (GhcPass 'Typechecked)
firstPat EquationInfo
eqn = ASSERT( notNull (eqn_pats eqn) ) head (eqn_pats eqn)

shiftEqns :: Functor f => f EquationInfo -> f EquationInfo
-- Drop the first pattern in each equation
shiftEqns :: forall (f :: * -> *). Functor f => f EquationInfo -> f EquationInfo
shiftEqns = (EquationInfo -> EquationInfo) -> f EquationInfo -> f EquationInfo
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap ((EquationInfo -> EquationInfo)
 -> f EquationInfo -> f EquationInfo)
-> (EquationInfo -> EquationInfo)
-> f EquationInfo
-> f EquationInfo
forall a b. (a -> b) -> a -> b
$ \EquationInfo
eqn -> EquationInfo
eqn { eqn_pats :: [Pat (GhcPass 'Typechecked)]
eqn_pats = [Pat (GhcPass 'Typechecked)] -> [Pat (GhcPass 'Typechecked)]
forall a. [a] -> [a]
tail (EquationInfo -> [Pat (GhcPass 'Typechecked)]
eqn_pats EquationInfo
eqn) }

-- Functions on MatchResult CoreExprs

matchCanFail :: MatchResult a -> Bool
matchCanFail :: forall a. MatchResult a -> Bool
matchCanFail (MR_Fallible {})  = Bool
True
matchCanFail (MR_Infallible {}) = Bool
False

alwaysFailMatchResult :: MatchResult CoreExpr
alwaysFailMatchResult :: MatchResult CoreExpr
alwaysFailMatchResult = (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr)
-> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail -> CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
fail

cantFailMatchResult :: CoreExpr -> MatchResult CoreExpr
cantFailMatchResult :: CoreExpr -> MatchResult CoreExpr
cantFailMatchResult CoreExpr
expr = DsM CoreExpr -> MatchResult CoreExpr
forall a. DsM a -> MatchResult a
MR_Infallible (DsM CoreExpr -> MatchResult CoreExpr)
-> DsM CoreExpr -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return CoreExpr
expr

extractMatchResult :: MatchResult CoreExpr -> CoreExpr -> DsM CoreExpr
extractMatchResult :: MatchResult CoreExpr -> CoreExpr -> DsM CoreExpr
extractMatchResult MatchResult CoreExpr
match_result CoreExpr
failure_expr =
  CoreExpr -> MatchResult CoreExpr -> DsM CoreExpr
forall a. CoreExpr -> MatchResult a -> DsM a
runMatchResult
    CoreExpr
failure_expr
    (MatchResult CoreExpr -> MatchResult CoreExpr
shareFailureHandler MatchResult CoreExpr
match_result)

combineMatchResults :: MatchResult CoreExpr -> MatchResult CoreExpr -> MatchResult CoreExpr
combineMatchResults :: MatchResult CoreExpr
-> MatchResult CoreExpr -> MatchResult CoreExpr
combineMatchResults match_result1 :: MatchResult CoreExpr
match_result1@(MR_Infallible DsM CoreExpr
_) MatchResult CoreExpr
_
  = MatchResult CoreExpr
match_result1
combineMatchResults MatchResult CoreExpr
match_result1 MatchResult CoreExpr
match_result2 =
  -- if the first pattern needs a failure handler (i.e. if it is fallible),
  -- make it let-bind it bind it with `shareFailureHandler`.
  case MatchResult CoreExpr -> MatchResult CoreExpr
shareFailureHandler MatchResult CoreExpr
match_result1 of
    MR_Infallible DsM CoreExpr
_ -> MatchResult CoreExpr
match_result1
    MR_Fallible CoreExpr -> DsM CoreExpr
body_fn1 -> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr)
-> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail_expr ->
      -- Before actually failing, try the next match arm.
      CoreExpr -> DsM CoreExpr
body_fn1 (CoreExpr -> DsM CoreExpr) -> DsM CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< CoreExpr -> MatchResult CoreExpr -> DsM CoreExpr
forall a. CoreExpr -> MatchResult a -> DsM a
runMatchResult CoreExpr
fail_expr MatchResult CoreExpr
match_result2

adjustMatchResultDs :: (a -> DsM b) -> MatchResult a -> MatchResult b
adjustMatchResultDs :: forall a b. (a -> DsM b) -> MatchResult a -> MatchResult b
adjustMatchResultDs a -> DsM b
encl_fn = \case
  MR_Infallible DsM a
body_fn -> DsM b -> MatchResult b
forall a. DsM a -> MatchResult a
MR_Infallible (DsM b -> MatchResult b) -> DsM b -> MatchResult b
forall a b. (a -> b) -> a -> b
$
    a -> DsM b
encl_fn (a -> DsM b) -> DsM a -> DsM b
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< DsM a
body_fn
  MR_Fallible CoreExpr -> DsM a
body_fn -> (CoreExpr -> DsM b) -> MatchResult b
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM b) -> MatchResult b)
-> (CoreExpr -> DsM b) -> MatchResult b
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail ->
    a -> DsM b
encl_fn (a -> DsM b) -> DsM a -> DsM b
forall (m :: * -> *) a b. Monad m => (a -> m b) -> m a -> m b
=<< CoreExpr -> DsM a
body_fn CoreExpr
fail

wrapBinds :: [(Var,Var)] -> CoreExpr -> CoreExpr
wrapBinds :: [(Id, Id)] -> CoreExpr -> CoreExpr
wrapBinds [] CoreExpr
e = CoreExpr
e
wrapBinds ((Id
new,Id
old):[(Id, Id)]
prs) CoreExpr
e = Id -> Id -> CoreExpr -> CoreExpr
wrapBind Id
new Id
old ([(Id, Id)] -> CoreExpr -> CoreExpr
wrapBinds [(Id, Id)]
prs CoreExpr
e)

wrapBind :: Var -> Var -> CoreExpr -> CoreExpr
wrapBind :: Id -> Id -> CoreExpr -> CoreExpr
wrapBind Id
new Id
old CoreExpr
body   -- NB: this function must deal with term
  | Id
newId -> Id -> Bool
forall a. Eq a => a -> a -> Bool
==Id
old    = CoreExpr
body  -- variables, type variables or coercion variables
  | Bool
otherwise   = Bind Id -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let (Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
new (Id -> CoreExpr
forall b. Id -> Expr b
varToCoreExpr Id
old)) CoreExpr
body

seqVar :: Var -> CoreExpr -> CoreExpr
seqVar :: Id -> CoreExpr -> CoreExpr
seqVar Id
var CoreExpr
body = CoreExpr -> Id -> CoreExpr -> CoreExpr
mkDefaultCase (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var) Id
var CoreExpr
body

mkCoLetMatchResult :: CoreBind -> MatchResult CoreExpr -> MatchResult CoreExpr
mkCoLetMatchResult :: Bind Id -> MatchResult CoreExpr -> MatchResult CoreExpr
mkCoLetMatchResult Bind Id
bind = (CoreExpr -> CoreExpr)
-> MatchResult CoreExpr -> MatchResult CoreExpr
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap (Bind Id -> CoreExpr -> CoreExpr
mkCoreLet Bind Id
bind)

-- (mkViewMatchResult var' viewExpr mr) makes the expression
-- let var' = viewExpr in mr
mkViewMatchResult :: Id -> CoreExpr -> MatchResult CoreExpr -> MatchResult CoreExpr
mkViewMatchResult :: Id -> CoreExpr -> MatchResult CoreExpr -> MatchResult CoreExpr
mkViewMatchResult Id
var' CoreExpr
viewExpr = (CoreExpr -> CoreExpr)
-> MatchResult CoreExpr -> MatchResult CoreExpr
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap ((CoreExpr -> CoreExpr)
 -> MatchResult CoreExpr -> MatchResult CoreExpr)
-> (CoreExpr -> CoreExpr)
-> MatchResult CoreExpr
-> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ Bind Id -> CoreExpr -> CoreExpr
mkCoreLet (Bind Id -> CoreExpr -> CoreExpr)
-> Bind Id -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$ Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
var' CoreExpr
viewExpr

mkEvalMatchResult :: Id -> Type -> MatchResult CoreExpr -> MatchResult CoreExpr
mkEvalMatchResult :: Id -> Mult -> MatchResult CoreExpr -> MatchResult CoreExpr
mkEvalMatchResult Id
var Mult
ty = (CoreExpr -> CoreExpr)
-> MatchResult CoreExpr -> MatchResult CoreExpr
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap ((CoreExpr -> CoreExpr)
 -> MatchResult CoreExpr -> MatchResult CoreExpr)
-> (CoreExpr -> CoreExpr)
-> MatchResult CoreExpr
-> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ \CoreExpr
e ->
  CoreExpr -> Id -> Mult -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Mult -> [Alt b] -> Expr b
Case (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var) Id
var Mult
ty [(AltCon
DEFAULT, [], CoreExpr
e)]

mkGuardedMatchResult :: CoreExpr -> MatchResult CoreExpr -> MatchResult CoreExpr
mkGuardedMatchResult :: CoreExpr -> MatchResult CoreExpr -> MatchResult CoreExpr
mkGuardedMatchResult CoreExpr
pred_expr MatchResult CoreExpr
mr = (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr)
-> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail -> do
  CoreExpr
body <- CoreExpr -> MatchResult CoreExpr -> DsM CoreExpr
forall a. CoreExpr -> MatchResult a -> DsM a
runMatchResult CoreExpr
fail MatchResult CoreExpr
mr
  CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> CoreExpr -> CoreExpr -> CoreExpr
mkIfThenElse CoreExpr
pred_expr CoreExpr
body CoreExpr
fail)

mkCoPrimCaseMatchResult :: Id                  -- Scrutinee
                        -> Type                      -- Type of the case
                        -> [(Literal, MatchResult CoreExpr)]  -- Alternatives
                        -> MatchResult CoreExpr               -- Literals are all unlifted
mkCoPrimCaseMatchResult :: Id
-> Mult
-> [(Literal, MatchResult CoreExpr)]
-> MatchResult CoreExpr
mkCoPrimCaseMatchResult Id
var Mult
ty [(Literal, MatchResult CoreExpr)]
match_alts
  = (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible CoreExpr -> DsM CoreExpr
mk_case
  where
    mk_case :: CoreExpr -> DsM CoreExpr
mk_case CoreExpr
fail = do
        [Alt Id]
alts <- ((Literal, MatchResult CoreExpr)
 -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
-> [(Literal, MatchResult CoreExpr)]
-> IOEnv (Env DsGblEnv DsLclEnv) [Alt Id]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (CoreExpr
-> (Literal, MatchResult CoreExpr)
-> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id)
forall {c} {a}.
CoreExpr
-> (Literal, MatchResult c)
-> IOEnv (Env DsGblEnv DsLclEnv) (AltCon, [a], c)
mk_alt CoreExpr
fail) [(Literal, MatchResult CoreExpr)]
sorted_alts
        CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> Id -> Mult -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Mult -> [Alt b] -> Expr b
Case (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var) Id
var Mult
ty ((AltCon
DEFAULT, [], CoreExpr
fail) Alt Id -> [Alt Id] -> [Alt Id]
forall a. a -> [a] -> [a]
: [Alt Id]
alts))

    sorted_alts :: [(Literal, MatchResult CoreExpr)]
sorted_alts = ((Literal, MatchResult CoreExpr) -> Literal)
-> [(Literal, MatchResult CoreExpr)]
-> [(Literal, MatchResult CoreExpr)]
forall b a. Ord b => (a -> b) -> [a] -> [a]
sortWith (Literal, MatchResult CoreExpr) -> Literal
forall a b. (a, b) -> a
fst [(Literal, MatchResult CoreExpr)]
match_alts       -- Right order for a Case
    mk_alt :: CoreExpr
-> (Literal, MatchResult c)
-> IOEnv (Env DsGblEnv DsLclEnv) (AltCon, [a], c)
mk_alt CoreExpr
fail (Literal
lit, MatchResult c
mr)
       = ASSERT( not (litIsLifted lit) )
         do c
body <- CoreExpr -> MatchResult c -> DsM c
forall a. CoreExpr -> MatchResult a -> DsM a
runMatchResult CoreExpr
fail MatchResult c
mr
            (AltCon, [a], c) -> IOEnv (Env DsGblEnv DsLclEnv) (AltCon, [a], c)
forall (m :: * -> *) a. Monad m => a -> m a
return (Literal -> AltCon
LitAlt Literal
lit, [], c
body)

data CaseAlt a = MkCaseAlt{ forall a. CaseAlt a -> a
alt_pat :: a,
                            forall a. CaseAlt a -> [Id]
alt_bndrs :: [Var],
                            forall a. CaseAlt a -> HsWrapper
alt_wrapper :: HsWrapper,
                            forall a. CaseAlt a -> MatchResult CoreExpr
alt_result :: MatchResult CoreExpr }

mkCoAlgCaseMatchResult
  :: Id -- ^ Scrutinee
  -> Type -- ^ Type of exp
  -> NonEmpty (CaseAlt DataCon) -- ^ Alternatives (bndrs *include* tyvars, dicts)
  -> MatchResult CoreExpr
mkCoAlgCaseMatchResult :: Id -> Mult -> NonEmpty (CaseAlt DataCon) -> MatchResult CoreExpr
mkCoAlgCaseMatchResult Id
var Mult
ty NonEmpty (CaseAlt DataCon)
match_alts
  | Bool
isNewtype  -- Newtype case; use a let
  = ASSERT( null match_alts_tail && null (tail arg_ids1) )
    Bind Id -> MatchResult CoreExpr -> MatchResult CoreExpr
mkCoLetMatchResult (Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
arg_id1 CoreExpr
newtype_rhs) MatchResult CoreExpr
match_result1

  | Bool
otherwise
  = Id -> Mult -> NonEmpty (CaseAlt DataCon) -> MatchResult CoreExpr
mkDataConCase Id
var Mult
ty NonEmpty (CaseAlt DataCon)
match_alts
  where
    isNewtype :: Bool
isNewtype = TyCon -> Bool
isNewTyCon (DataCon -> TyCon
dataConTyCon (CaseAlt DataCon -> DataCon
forall a. CaseAlt a -> a
alt_pat CaseAlt DataCon
alt1))

        -- [Interesting: because of GADTs, we can't rely on the type of
        --  the scrutinised Id to be sufficiently refined to have a TyCon in it]

    alt1 :: CaseAlt DataCon
alt1@MkCaseAlt{ alt_bndrs :: forall a. CaseAlt a -> [Id]
alt_bndrs = [Id]
arg_ids1, alt_result :: forall a. CaseAlt a -> MatchResult CoreExpr
alt_result = MatchResult CoreExpr
match_result1 } :| [CaseAlt DataCon]
match_alts_tail
      = NonEmpty (CaseAlt DataCon)
match_alts
    -- Stuff for newtype
    arg_id1 :: Id
arg_id1       = ASSERT( notNull arg_ids1 ) head arg_ids1
    var_ty :: Mult
var_ty        = Id -> Mult
idType Id
var
    (TyCon
tc, [Mult]
ty_args) = Mult -> (TyCon, [Mult])
tcSplitTyConApp Mult
var_ty      -- Don't look through newtypes
                                                -- (not that splitTyConApp does, these days)
    newtype_rhs :: CoreExpr
newtype_rhs = TyCon -> [Mult] -> CoreExpr -> CoreExpr
unwrapNewTypeBody TyCon
tc [Mult]
ty_args (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var)

mkCoSynCaseMatchResult :: Id -> Type -> CaseAlt PatSyn -> MatchResult CoreExpr
mkCoSynCaseMatchResult :: Id -> Mult -> CaseAlt PatSyn -> MatchResult CoreExpr
mkCoSynCaseMatchResult Id
var Mult
ty CaseAlt PatSyn
alt = (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr)
-> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ Id -> Mult -> CaseAlt PatSyn -> CoreExpr -> DsM CoreExpr
mkPatSynCase Id
var Mult
ty CaseAlt PatSyn
alt

mkPatSynCase :: Id -> Type -> CaseAlt PatSyn -> CoreExpr -> DsM CoreExpr
mkPatSynCase :: Id -> Mult -> CaseAlt PatSyn -> CoreExpr -> DsM CoreExpr
mkPatSynCase Id
var Mult
ty CaseAlt PatSyn
alt CoreExpr
fail = do
    CoreExpr
matcher <- LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
dsLExpr (LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr)
-> LHsExpr (GhcPass 'Typechecked) -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ HsWrapper
-> LHsExpr (GhcPass 'Typechecked) -> LHsExpr (GhcPass 'Typechecked)
mkLHsWrap HsWrapper
wrapper (LHsExpr (GhcPass 'Typechecked) -> LHsExpr (GhcPass 'Typechecked))
-> LHsExpr (GhcPass 'Typechecked) -> LHsExpr (GhcPass 'Typechecked)
forall a b. (a -> b) -> a -> b
$
                         Id -> [Mult] -> LHsExpr (GhcPass 'Typechecked)
nlHsTyApp Id
matcher [HasDebugCallStack => Mult -> Mult
Mult -> Mult
getRuntimeRep Mult
ty, Mult
ty]
    CoreExpr
cont <- [Id] -> CoreExpr -> CoreExpr
mkCoreLams [Id]
bndrs (CoreExpr -> CoreExpr) -> DsM CoreExpr -> DsM CoreExpr
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CoreExpr -> MatchResult CoreExpr -> DsM CoreExpr
forall a. CoreExpr -> MatchResult a -> DsM a
runMatchResult CoreExpr
fail MatchResult CoreExpr
match_result
    CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> DsM CoreExpr) -> CoreExpr -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ SDoc -> CoreExpr -> [CoreExpr] -> CoreExpr
mkCoreAppsDs (String -> SDoc
text String
"patsyn" SDoc -> SDoc -> SDoc
<+> Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
var) CoreExpr
matcher [Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var, CoreExpr -> CoreExpr
ensure_unstrict CoreExpr
cont, Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
voidArgId CoreExpr
fail]
  where
    MkCaseAlt{ alt_pat :: forall a. CaseAlt a -> a
alt_pat = PatSyn
psyn,
               alt_bndrs :: forall a. CaseAlt a -> [Id]
alt_bndrs = [Id]
bndrs,
               alt_wrapper :: forall a. CaseAlt a -> HsWrapper
alt_wrapper = HsWrapper
wrapper,
               alt_result :: forall a. CaseAlt a -> MatchResult CoreExpr
alt_result = MatchResult CoreExpr
match_result} = CaseAlt PatSyn
alt
    (Id
matcher, Bool
needs_void_lam) = PatSyn -> (Id, Bool)
patSynMatcher PatSyn
psyn

    -- See Note [Matchers and builders for pattern synonyms] in GHC.Core.PatSyn
    -- on these extra Void# arguments
    ensure_unstrict :: CoreExpr -> CoreExpr
ensure_unstrict CoreExpr
cont | Bool
needs_void_lam = Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
voidArgId CoreExpr
cont
                         | Bool
otherwise      = CoreExpr
cont

mkDataConCase :: Id -> Type -> NonEmpty (CaseAlt DataCon) -> MatchResult CoreExpr
mkDataConCase :: Id -> Mult -> NonEmpty (CaseAlt DataCon) -> MatchResult CoreExpr
mkDataConCase Id
var Mult
ty alts :: NonEmpty (CaseAlt DataCon)
alts@(CaseAlt DataCon
alt1 :| [CaseAlt DataCon]
_)
    = (Maybe (Alt Id) -> [Alt Id] -> CoreExpr)
-> MatchResult (Maybe (Alt Id))
-> MatchResult [Alt Id]
-> MatchResult CoreExpr
forall (f :: * -> *) a b c.
Applicative f =>
(a -> b -> c) -> f a -> f b -> f c
liftA2 Maybe (Alt Id) -> [Alt Id] -> CoreExpr
mk_case MatchResult (Maybe (Alt Id))
mk_default MatchResult [Alt Id]
mk_alts
    -- The liftA2 combines the failability of all the alternatives and the default
  where
    con1 :: DataCon
con1          = CaseAlt DataCon -> DataCon
forall a. CaseAlt a -> a
alt_pat CaseAlt DataCon
alt1
    tycon :: TyCon
tycon         = DataCon -> TyCon
dataConTyCon DataCon
con1
    data_cons :: [DataCon]
data_cons     = TyCon -> [DataCon]
tyConDataCons TyCon
tycon

    sorted_alts :: [ CaseAlt DataCon ]
    sorted_alts :: [CaseAlt DataCon]
sorted_alts  = (CaseAlt DataCon -> ConTag)
-> [CaseAlt DataCon] -> [CaseAlt DataCon]
forall b a. Ord b => (a -> b) -> [a] -> [a]
sortWith (DataCon -> ConTag
dataConTag (DataCon -> ConTag)
-> (CaseAlt DataCon -> DataCon) -> CaseAlt DataCon -> ConTag
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CaseAlt DataCon -> DataCon
forall a. CaseAlt a -> a
alt_pat) ([CaseAlt DataCon] -> [CaseAlt DataCon])
-> [CaseAlt DataCon] -> [CaseAlt DataCon]
forall a b. (a -> b) -> a -> b
$ NonEmpty (CaseAlt DataCon) -> [CaseAlt DataCon]
forall a. NonEmpty a -> [a]
NEL.toList NonEmpty (CaseAlt DataCon)
alts

    var_ty :: Mult
var_ty       = Id -> Mult
idType Id
var
    (TyCon
_, [Mult]
ty_args) = Mult -> (TyCon, [Mult])
tcSplitTyConApp Mult
var_ty -- Don't look through newtypes
                                          -- (not that splitTyConApp does, these days)

    mk_case :: Maybe CoreAlt -> [CoreAlt] -> CoreExpr
    mk_case :: Maybe (Alt Id) -> [Alt Id] -> CoreExpr
mk_case Maybe (Alt Id)
def [Alt Id]
alts = CoreExpr -> Scaled Mult -> Mult -> [Alt Id] -> CoreExpr
mkWildCase (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
var) (Id -> Scaled Mult
idScaledType Id
var) Mult
ty ([Alt Id] -> CoreExpr) -> [Alt Id] -> CoreExpr
forall a b. (a -> b) -> a -> b
$
      Maybe (Alt Id) -> [Alt Id]
forall a. Maybe a -> [a]
maybeToList Maybe (Alt Id)
def [Alt Id] -> [Alt Id] -> [Alt Id]
forall a. [a] -> [a] -> [a]
++ [Alt Id]
alts

    mk_alts :: MatchResult [CoreAlt]
    mk_alts :: MatchResult [Alt Id]
mk_alts = (CaseAlt DataCon -> MatchResult (Alt Id))
-> [CaseAlt DataCon] -> MatchResult [Alt Id]
forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse CaseAlt DataCon -> MatchResult (Alt Id)
mk_alt [CaseAlt DataCon]
sorted_alts

    mk_alt :: CaseAlt DataCon -> MatchResult CoreAlt
    mk_alt :: CaseAlt DataCon -> MatchResult (Alt Id)
mk_alt MkCaseAlt { alt_pat :: forall a. CaseAlt a -> a
alt_pat = DataCon
con
                     , alt_bndrs :: forall a. CaseAlt a -> [Id]
alt_bndrs = [Id]
args
                     , alt_result :: forall a. CaseAlt a -> MatchResult CoreExpr
alt_result = MatchResult CoreExpr
match_result } =
      ((CoreExpr -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
 -> MatchResult CoreExpr -> MatchResult (Alt Id))
-> MatchResult CoreExpr
-> (CoreExpr -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
-> MatchResult (Alt Id)
forall a b c. (a -> b -> c) -> b -> a -> c
flip (CoreExpr -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
-> MatchResult CoreExpr -> MatchResult (Alt Id)
forall a b. (a -> DsM b) -> MatchResult a -> MatchResult b
adjustMatchResultDs MatchResult CoreExpr
match_result ((CoreExpr -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
 -> MatchResult (Alt Id))
-> (CoreExpr -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id))
-> MatchResult (Alt Id)
forall a b. (a -> b) -> a -> b
$ \CoreExpr
body -> do
        case DataCon -> Maybe DataConBoxer
dataConBoxer DataCon
con of
          Maybe DataConBoxer
Nothing -> Alt Id -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (DataCon -> AltCon
DataAlt DataCon
con, [Id]
args, CoreExpr
body)
          Just (DCB [Mult] -> [Id] -> UniqSM ([Id], [Bind Id])
boxer) -> do
            UniqSupply
us <- TcRnIf DsGblEnv DsLclEnv UniqSupply
forall gbl lcl. TcRnIf gbl lcl UniqSupply
newUniqueSupply
            let ([Id]
rep_ids, [Bind Id]
binds) = UniqSupply -> UniqSM ([Id], [Bind Id]) -> ([Id], [Bind Id])
forall a. UniqSupply -> UniqSM a -> a
initUs_ UniqSupply
us ([Mult] -> [Id] -> UniqSM ([Id], [Bind Id])
boxer [Mult]
ty_args [Id]
args)
            let rep_ids' :: [Id]
rep_ids' = (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map (Mult -> Id -> Id
scaleVarBy (Id -> Mult
idMult Id
var)) [Id]
rep_ids
              -- Upholds the invariant that the binders of a case expression
              -- must be scaled by the case multiplicity. See Note [Case
              -- expression invariants] in CoreSyn.
            Alt Id -> IOEnv (Env DsGblEnv DsLclEnv) (Alt Id)
forall (m :: * -> *) a. Monad m => a -> m a
return (DataCon -> AltCon
DataAlt DataCon
con, [Id]
rep_ids', [Bind Id] -> CoreExpr -> CoreExpr
forall b. [Bind b] -> Expr b -> Expr b
mkLets [Bind Id]
binds CoreExpr
body)

    mk_default :: MatchResult (Maybe CoreAlt)
    mk_default :: MatchResult (Maybe (Alt Id))
mk_default
      | Bool
exhaustive_case = DsM (Maybe (Alt Id)) -> MatchResult (Maybe (Alt Id))
forall a. DsM a -> MatchResult a
MR_Infallible (DsM (Maybe (Alt Id)) -> MatchResult (Maybe (Alt Id)))
-> DsM (Maybe (Alt Id)) -> MatchResult (Maybe (Alt Id))
forall a b. (a -> b) -> a -> b
$ Maybe (Alt Id) -> DsM (Maybe (Alt Id))
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe (Alt Id)
forall a. Maybe a
Nothing
      | Bool
otherwise       = (CoreExpr -> DsM (Maybe (Alt Id))) -> MatchResult (Maybe (Alt Id))
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM (Maybe (Alt Id)))
 -> MatchResult (Maybe (Alt Id)))
-> (CoreExpr -> DsM (Maybe (Alt Id)))
-> MatchResult (Maybe (Alt Id))
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail -> Maybe (Alt Id) -> DsM (Maybe (Alt Id))
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe (Alt Id) -> DsM (Maybe (Alt Id)))
-> Maybe (Alt Id) -> DsM (Maybe (Alt Id))
forall a b. (a -> b) -> a -> b
$ Alt Id -> Maybe (Alt Id)
forall a. a -> Maybe a
Just (AltCon
DEFAULT, [], CoreExpr
fail)

    mentioned_constructors :: UniqSet DataCon
mentioned_constructors = [DataCon] -> UniqSet DataCon
forall a. Uniquable a => [a] -> UniqSet a
mkUniqSet ([DataCon] -> UniqSet DataCon) -> [DataCon] -> UniqSet DataCon
forall a b. (a -> b) -> a -> b
$ (CaseAlt DataCon -> DataCon) -> [CaseAlt DataCon] -> [DataCon]
forall a b. (a -> b) -> [a] -> [b]
map CaseAlt DataCon -> DataCon
forall a. CaseAlt a -> a
alt_pat [CaseAlt DataCon]
sorted_alts
    un_mentioned_constructors :: UniqSet DataCon
un_mentioned_constructors
        = [DataCon] -> UniqSet DataCon
forall a. Uniquable a => [a] -> UniqSet a
mkUniqSet [DataCon]
data_cons UniqSet DataCon -> UniqSet DataCon -> UniqSet DataCon
forall a. UniqSet a -> UniqSet a -> UniqSet a
`minusUniqSet` UniqSet DataCon
mentioned_constructors
    exhaustive_case :: Bool
exhaustive_case = UniqSet DataCon -> Bool
forall a. UniqSet a -> Bool
isEmptyUniqSet UniqSet DataCon
un_mentioned_constructors

{-
************************************************************************
*                                                                      *
\subsection{Desugarer's versions of some Core functions}
*                                                                      *
************************************************************************
-}

mkErrorAppDs :: Id              -- The error function
             -> Type            -- Type to which it should be applied
             -> SDoc            -- The error message string to pass
             -> DsM CoreExpr

mkErrorAppDs :: Id -> Mult -> SDoc -> DsM CoreExpr
mkErrorAppDs Id
err_id Mult
ty SDoc
msg = do
    SrcSpan
src_loc <- DsM SrcSpan
getSrcSpanDs
    DynFlags
dflags <- IOEnv (Env DsGblEnv DsLclEnv) DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
    let
        full_msg :: String
full_msg = DynFlags -> SDoc -> String
showSDoc DynFlags
dflags ([SDoc] -> SDoc
hcat [SrcSpan -> SDoc
forall a. Outputable a => a -> SDoc
ppr SrcSpan
src_loc, SDoc
vbar, SDoc
msg])
        core_msg :: CoreExpr
core_msg = Literal -> CoreExpr
forall b. Literal -> Expr b
Lit (String -> Literal
mkLitString String
full_msg)
        -- mkLitString returns a result of type String#
    CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> [CoreExpr] -> CoreExpr
forall b. Expr b -> [Expr b] -> Expr b
mkApps (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
err_id) [Mult -> CoreExpr
forall b. Mult -> Expr b
Type (HasDebugCallStack => Mult -> Mult
Mult -> Mult
getRuntimeRep Mult
ty), Mult -> CoreExpr
forall b. Mult -> Expr b
Type Mult
ty, CoreExpr
core_msg])

{-
'mkCoreAppDs' and 'mkCoreAppsDs' handle the special-case desugaring of 'seq'.

Note [Desugaring seq]
~~~~~~~~~~~~~~~~~~~~~

There are a few subtleties in the desugaring of `seq`:

 1. (as described in #1031)

    Consider,
       f x y = x `seq` (y `seq` (# x,y #))

    The [Core let/app invariant] means that, other things being equal, because
    the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:

       f x y = case (y `seq` (# x,y #)) of v -> x `seq` v

    But that is bad for two reasons:
      (a) we now evaluate y before x, and
      (b) we can't bind v to an unboxed pair

    Seq is very, very special!  So we recognise it right here, and desugar to
            case x of _ -> case y of _ -> (# x,y #)

 2. (as described in #2273)

    Consider
       let chp = case b of { True -> fst x; False -> 0 }
       in chp `seq` ...chp...
    Here the seq is designed to plug the space leak of retaining (snd x)
    for too long.

    If we rely on the ordinary inlining of seq, we'll get
       let chp = case b of { True -> fst x; False -> 0 }
       case chp of _ { I# -> ...chp... }

    But since chp is cheap, and the case is an alluring contet, we'll
    inline chp into the case scrutinee.  Now there is only one use of chp,
    so we'll inline a second copy.  Alas, we've now ruined the purpose of
    the seq, by re-introducing the space leak:
        case (case b of {True -> fst x; False -> 0}) of
          I# _ -> ...case b of {True -> fst x; False -> 0}...

    We can try to avoid doing this by ensuring that the binder-swap in the
    case happens, so we get his at an early stage:
       case chp of chp2 { I# -> ...chp2... }
    But this is fragile.  The real culprit is the source program.  Perhaps we
    should have said explicitly
       let !chp2 = chp in ...chp2...

    But that's painful.  So the code here does a little hack to make seq
    more robust: a saturated application of 'seq' is turned *directly* into
    the case expression, thus:
       x  `seq` e2 ==> case x of x -> e2    -- Note shadowing!
       e1 `seq` e2 ==> case x of _ -> e2

    So we desugar our example to:
       let chp = case b of { True -> fst x; False -> 0 }
       case chp of chp { I# -> ...chp... }
    And now all is well.

    The reason it's a hack is because if you define mySeq=seq, the hack
    won't work on mySeq.

 3. (as described in #2409)

    The isLocalId ensures that we don't turn
            True `seq` e
    into
            case True of True { ... }
    which stupidly tries to bind the datacon 'True'.
-}

-- NB: Make sure the argument is not levity polymorphic
mkCoreAppDs  :: SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreAppDs :: SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreAppDs SDoc
_ (Var Id
f `App` Type Mult
_r `App` Type Mult
ty1 `App` Type Mult
ty2 `App` CoreExpr
arg1) CoreExpr
arg2
  | Id
f Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
seqIdKey            -- Note [Desugaring seq], points (1) and (2)
  = CoreExpr -> Id -> Mult -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Mult -> [Alt b] -> Expr b
Case CoreExpr
arg1 Id
case_bndr Mult
ty2 [(AltCon
DEFAULT,[],CoreExpr
arg2)]
  where
    case_bndr :: Id
case_bndr = case CoreExpr
arg1 of
                   Var Id
v1 | Name -> Bool
isInternalName (Id -> Name
idName Id
v1)
                          -> Id
v1        -- Note [Desugaring seq], points (2) and (3)
                   CoreExpr
_      -> Mult -> Mult -> Id
mkWildValBinder Mult
Many Mult
ty1

mkCoreAppDs SDoc
s CoreExpr
fun CoreExpr
arg = SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreApp SDoc
s CoreExpr
fun CoreExpr
arg  -- The rest is done in GHC.Core.Make

-- NB: No argument can be levity polymorphic
mkCoreAppsDs :: SDoc -> CoreExpr -> [CoreExpr] -> CoreExpr
mkCoreAppsDs :: SDoc -> CoreExpr -> [CoreExpr] -> CoreExpr
mkCoreAppsDs SDoc
s CoreExpr
fun [CoreExpr]
args = (CoreExpr -> CoreExpr -> CoreExpr)
-> CoreExpr -> [CoreExpr] -> CoreExpr
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' (SDoc -> CoreExpr -> CoreExpr -> CoreExpr
mkCoreAppDs SDoc
s) CoreExpr
fun [CoreExpr]
args

mkCastDs :: CoreExpr -> Coercion -> CoreExpr
-- We define a desugarer-specific version of GHC.Core.Utils.mkCast,
-- because in the immediate output of the desugarer, we can have
-- apparently-mis-matched coercions:  E.g.
--     let a = b
--     in (x :: a) |> (co :: b ~ Int)
-- Lint know about type-bindings for let and does not complain
-- So here we do not make the assertion checks that we make in
-- GHC.Core.Utils.mkCast; and we do less peephole optimisation too
mkCastDs :: CoreExpr -> Coercion -> CoreExpr
mkCastDs CoreExpr
e Coercion
co | Coercion -> Bool
isReflCo Coercion
co = CoreExpr
e
              | Bool
otherwise   = CoreExpr -> Coercion -> CoreExpr
forall b. Expr b -> Coercion -> Expr b
Cast CoreExpr
e Coercion
co

{-
************************************************************************
*                                                                      *
               Tuples and selector bindings
*                                                                      *
************************************************************************

This is used in various places to do with lazy patterns.
For each binder $b$ in the pattern, we create a binding:
\begin{verbatim}
    b = case v of pat' -> b'
\end{verbatim}
where @pat'@ is @pat@ with each binder @b@ cloned into @b'@.

ToDo: making these bindings should really depend on whether there's
much work to be done per binding.  If the pattern is complex, it
should be de-mangled once, into a tuple (and then selected from).
Otherwise the demangling can be in-line in the bindings (as here).

Boring!  Boring!  One error message per binder.  The above ToDo is
even more helpful.  Something very similar happens for pattern-bound
expressions.

Note [mkSelectorBinds]
~~~~~~~~~~~~~~~~~~~~~~
mkSelectorBinds is used to desugar a pattern binding {p = e},
in a binding group:
  let { ...; p = e; ... } in body
where p binds x,y (this list of binders can be empty).
There are two cases.

------ Special case (A) -------
  For a pattern that is just a variable,
     let !x = e in body
  ==>
     let x = e in x `seq` body
  So we return the binding, with 'x' as the variable to seq.

------ Special case (B) -------
  For a pattern that is essentially just a tuple:
      * A product type, so cannot fail
      * Only one level, so that
          - generating multiple matches is fine
          - seq'ing it evaluates the same as matching it
  Then instead we generate
       { v = e
       ; x = case v of p -> x
       ; y = case v of p -> y }
  with 'v' as the variable to force

------ General case (C) -------
  In the general case we generate these bindings:
       let { ...; p = e; ... } in body
  ==>
       let { t = case e of p -> (x,y)
           ; x = case t of (x,y) -> x
           ; y = case t of (x,y) -> y }
       in t `seq` body

  Note that we return 't' as the variable to force if the pattern
  is strict (i.e. with -XStrict or an outermost-bang-pattern)

  Note that (A) /includes/ the situation where

   * The pattern binds exactly one variable
        let !(Just (Just x) = e in body
     ==>
       let { t = case e of Just (Just v) -> Solo v
           ; v = case t of Solo v -> v }
       in t `seq` body
    The 'Solo' is a one-tuple; see Note [One-tuples] in GHC.Builtin.Types
    Note that forcing 't' makes the pattern match happen,
    but does not force 'v'.

  * The pattern binds no variables
        let !(True,False) = e in body
    ==>
        let t = case e of (True,False) -> ()
        in t `seq` body


------ Examples ----------
  *   !(_, (_, a)) = e
    ==>
      t = case e of (_, (_, a)) -> Solo a
      a = case t of Solo a -> a

    Note that
     - Forcing 't' will force the pattern to match fully;
       e.g. will diverge if (snd e) is bottom
     - But 'a' itself is not forced; it is wrapped in a one-tuple
       (see Note [One-tuples] in GHC.Builtin.Types)

  *   !(Just x) = e
    ==>
      t = case e of Just x -> Solo x
      x = case t of Solo x -> x

    Again, forcing 't' will fail if 'e' yields Nothing.

Note that even though this is rather general, the special cases
work out well:

* One binder, not -XStrict:

    let Just (Just v) = e in body
  ==>
    let t = case e of Just (Just v) -> Solo v
        v = case t of Solo v -> v
    in body
  ==>
    let v = case (case e of Just (Just v) -> Solo v) of
              Solo v -> v
    in body
  ==>
    let v = case e of Just (Just v) -> v
    in body

* Non-recursive, -XStrict
     let p = e in body
  ==>
     let { t = case e of p -> (x,y)
         ; x = case t of (x,y) -> x
         ; y = case t of (x,y) -> x }
     in t `seq` body
  ==> {inline seq, float x,y bindings inwards}
     let t = case e of p -> (x,y) in
     case t of t' ->
     let { x = case t' of (x,y) -> x
         ; y = case t' of (x,y) -> x } in
     body
  ==> {inline t, do case of case}
     case e of p ->
     let t = (x,y) in
     let { x = case t' of (x,y) -> x
         ; y = case t' of (x,y) -> x } in
     body
  ==> {case-cancellation, drop dead code}
     case e of p -> body

* Special case (B) is there to avoid fruitlessly taking the tuple
  apart and rebuilding it. For example, consider
     { K x y = e }
  where K is a product constructor.  Then general case (A) does:
     { t = case e of K x y -> (x,y)
     ; x = case t of (x,y) -> x
     ; y = case t of (x,y) -> y }
  In the lazy case we can't optimise out this fruitless taking apart
  and rebuilding.  Instead (B) builds
     { v = e
     ; x = case v of K x y -> x
     ; y = case v of K x y -> y }
  which is better.
-}
-- Remark: pattern selectors only occur in unrestricted patterns so we are free
-- to select Many as the multiplicity of every let-expression introduced.
mkSelectorBinds :: [[Tickish Id]] -- ^ ticks to add, possibly
                -> LPat GhcTc     -- ^ The pattern
                -> CoreExpr       -- ^ Expression to which the pattern is bound
                -> DsM (Id,[(Id,CoreExpr)])
                -- ^ Id the rhs is bound to, for desugaring strict
                -- binds (see Note [Desugar Strict binds] in "GHC.HsToCore.Binds")
                -- and all the desugared binds

mkSelectorBinds :: [[Tickish Id]]
-> XRec (GhcPass 'Typechecked) Pat
-> CoreExpr
-> DsM (Id, [(Id, CoreExpr)])
mkSelectorBinds [[Tickish Id]]
ticks XRec (GhcPass 'Typechecked) Pat
pat CoreExpr
val_expr
  | L SrcSpan
_ (VarPat XVarPat (GhcPass 'Typechecked)
_ (L SrcSpan
_ IdP (GhcPass 'Typechecked)
v)) <- XRec (GhcPass 'Typechecked) Pat
pat'     -- Special case (A)
  = (Id, [(Id, CoreExpr)]) -> DsM (Id, [(Id, CoreExpr)])
forall (m :: * -> *) a. Monad m => a -> m a
return (Id
IdP (GhcPass 'Typechecked)
v, [(Id
IdP (GhcPass 'Typechecked)
v, CoreExpr
val_expr)])

  | XRec (GhcPass 'Typechecked) Pat -> Bool
is_flat_prod_lpat XRec (GhcPass 'Typechecked) Pat
pat'           -- Special case (B)
  = do { let pat_ty :: Mult
pat_ty = XRec (GhcPass 'Typechecked) Pat -> Mult
hsLPatType XRec (GhcPass 'Typechecked) Pat
pat'
       ; Id
val_var <- Mult -> Mult -> DsM Id
newSysLocalDsNoLP Mult
Many Mult
pat_ty

       ; let mk_bind :: [Tickish Id] -> Id -> IOEnv (Env DsGblEnv DsLclEnv) (Id, CoreExpr)
mk_bind [Tickish Id]
tick Id
bndr_var
               -- (mk_bind sv bv)  generates  bv = case sv of { pat -> bv }
               -- Remember, 'pat' binds 'bv'
               = do { CoreExpr
rhs_expr <- CoreExpr
-> HsMatchContext GhcRn
-> XRec (GhcPass 'Typechecked) Pat
-> CoreExpr
-> CoreExpr
-> DsM CoreExpr
matchSimply (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
val_var) HsMatchContext GhcRn
forall p. HsMatchContext p
PatBindRhs XRec (GhcPass 'Typechecked) Pat
pat'
                                       (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
bndr_var)
                                       (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
bndr_var)  -- Neat hack
                      -- Neat hack: since 'pat' can't fail, the
                      -- "fail-expr" passed to matchSimply is not
                      -- used. But it /is/ used for its type, and for
                      -- that bndr_var is just the ticket.
                    ; (Id, CoreExpr) -> IOEnv (Env DsGblEnv DsLclEnv) (Id, CoreExpr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Id
bndr_var, [Tickish Id] -> CoreExpr -> CoreExpr
mkOptTickBox [Tickish Id]
tick CoreExpr
rhs_expr) }

       ; [(Id, CoreExpr)]
binds <- ([Tickish Id]
 -> Id -> IOEnv (Env DsGblEnv DsLclEnv) (Id, CoreExpr))
-> [[Tickish Id]]
-> [Id]
-> IOEnv (Env DsGblEnv DsLclEnv) [(Id, CoreExpr)]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM [Tickish Id] -> Id -> IOEnv (Env DsGblEnv DsLclEnv) (Id, CoreExpr)
mk_bind [[Tickish Id]]
ticks' [Id]
[IdP (GhcPass 'Typechecked)]
binders
       ; (Id, [(Id, CoreExpr)]) -> DsM (Id, [(Id, CoreExpr)])
forall (m :: * -> *) a. Monad m => a -> m a
return ( Id
val_var, (Id
val_var, CoreExpr
val_expr) (Id, CoreExpr) -> [(Id, CoreExpr)] -> [(Id, CoreExpr)]
forall a. a -> [a] -> [a]
: [(Id, CoreExpr)]
binds) }

  | Bool
otherwise                          -- General case (C)
  = do { Id
tuple_var  <- Mult -> Mult -> DsM Id
newSysLocalDs Mult
Many Mult
tuple_ty
       ; CoreExpr
error_expr <- Id -> Mult -> SDoc -> DsM CoreExpr
mkErrorAppDs Id
pAT_ERROR_ID Mult
tuple_ty (GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> SDoc
forall a. Outputable a => a -> SDoc
ppr GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
pat')
       ; CoreExpr
tuple_expr <- CoreExpr
-> HsMatchContext GhcRn
-> XRec (GhcPass 'Typechecked) Pat
-> CoreExpr
-> CoreExpr
-> DsM CoreExpr
matchSimply CoreExpr
val_expr HsMatchContext GhcRn
forall p. HsMatchContext p
PatBindRhs XRec (GhcPass 'Typechecked) Pat
pat
                                   CoreExpr
local_tuple CoreExpr
error_expr
       ; let mk_tup_bind :: [Tickish Id] -> Id -> (Id, CoreExpr)
mk_tup_bind [Tickish Id]
tick Id
binder
               = (Id
binder, [Tickish Id] -> CoreExpr -> CoreExpr
mkOptTickBox [Tickish Id]
tick (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
forall a b. (a -> b) -> a -> b
$
                          [Id] -> Id -> Id -> CoreExpr -> CoreExpr
mkTupleSelector1 [Id]
local_binders Id
binder
                                           Id
tuple_var (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
tuple_var))
             tup_binds :: [(Id, CoreExpr)]
tup_binds = ([Tickish Id] -> Id -> (Id, CoreExpr))
-> [[Tickish Id]] -> [Id] -> [(Id, CoreExpr)]
forall a b c. (a -> b -> c) -> [a] -> [b] -> [c]
zipWith [Tickish Id] -> Id -> (Id, CoreExpr)
mk_tup_bind [[Tickish Id]]
ticks' [Id]
[IdP (GhcPass 'Typechecked)]
binders
       ; (Id, [(Id, CoreExpr)]) -> DsM (Id, [(Id, CoreExpr)])
forall (m :: * -> *) a. Monad m => a -> m a
return (Id
tuple_var, (Id
tuple_var, CoreExpr
tuple_expr) (Id, CoreExpr) -> [(Id, CoreExpr)] -> [(Id, CoreExpr)]
forall a. a -> [a] -> [a]
: [(Id, CoreExpr)]
tup_binds) }
  where
    pat' :: XRec (GhcPass 'Typechecked) Pat
pat' = XRec (GhcPass 'Typechecked) Pat -> XRec (GhcPass 'Typechecked) Pat
forall (p :: Pass). LPat (GhcPass p) -> LPat (GhcPass p)
strip_bangs XRec (GhcPass 'Typechecked) Pat
pat
           -- Strip the bangs before looking for case (A) or (B)
           -- The incoming pattern may well have a bang on it

    binders :: [IdP (GhcPass 'Typechecked)]
binders = XRec (GhcPass 'Typechecked) Pat -> [IdP (GhcPass 'Typechecked)]
forall p. CollectPass p => LPat p -> [IdP p]
collectPatBinders XRec (GhcPass 'Typechecked) Pat
pat'
    ticks' :: [[Tickish Id]]
ticks'  = [[Tickish Id]]
ticks [[Tickish Id]] -> [[Tickish Id]] -> [[Tickish Id]]
forall a. [a] -> [a] -> [a]
++ [Tickish Id] -> [[Tickish Id]]
forall a. a -> [a]
repeat []

    local_binders :: [Id]
local_binders = (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Id
localiseId [Id]
[IdP (GhcPass 'Typechecked)]
binders      -- See Note [Localise pattern binders]
    local_tuple :: CoreExpr
local_tuple   = [Id] -> CoreExpr
mkBigCoreVarTup1 [Id]
[IdP (GhcPass 'Typechecked)]
binders
    tuple_ty :: Mult
tuple_ty      = CoreExpr -> Mult
exprType CoreExpr
local_tuple

strip_bangs :: LPat (GhcPass p) -> LPat (GhcPass p)
-- Remove outermost bangs and parens
strip_bangs :: forall (p :: Pass). LPat (GhcPass p) -> LPat (GhcPass p)
strip_bangs (L SrcSpan
_ (ParPat XParPat (GhcPass p)
_ LPat (GhcPass p)
p))  = LPat (GhcPass p) -> LPat (GhcPass p)
forall (p :: Pass). LPat (GhcPass p) -> LPat (GhcPass p)
strip_bangs LPat (GhcPass p)
p
strip_bangs (L SrcSpan
_ (BangPat XBangPat (GhcPass p)
_ LPat (GhcPass p)
p)) = LPat (GhcPass p) -> LPat (GhcPass p)
forall (p :: Pass). LPat (GhcPass p) -> LPat (GhcPass p)
strip_bangs LPat (GhcPass p)
p
strip_bangs LPat (GhcPass p)
lp                  = LPat (GhcPass p)
lp

is_flat_prod_lpat :: LPat GhcTc -> Bool
is_flat_prod_lpat :: XRec (GhcPass 'Typechecked) Pat -> Bool
is_flat_prod_lpat = Pat (GhcPass 'Typechecked) -> Bool
is_flat_prod_pat (Pat (GhcPass 'Typechecked) -> Bool)
-> (GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
    -> Pat (GhcPass 'Typechecked))
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> Pat (GhcPass 'Typechecked)
forall l e. GenLocated l e -> e
unLoc

is_flat_prod_pat :: Pat GhcTc -> Bool
is_flat_prod_pat :: Pat (GhcPass 'Typechecked) -> Bool
is_flat_prod_pat (ParPat XParPat (GhcPass 'Typechecked)
_ XRec (GhcPass 'Typechecked) Pat
p)          = XRec (GhcPass 'Typechecked) Pat -> Bool
is_flat_prod_lpat XRec (GhcPass 'Typechecked) Pat
p
is_flat_prod_pat (TuplePat XTuplePat (GhcPass 'Typechecked)
_ [XRec (GhcPass 'Typechecked) Pat]
ps Boxity
Boxed) = (GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Bool)
-> [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Bool
forall (p :: Pass). LPat (GhcPass p) -> Bool
is_triv_lpat [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
[XRec (GhcPass 'Typechecked) Pat]
ps
is_flat_prod_pat (ConPat { pat_con :: forall p. Pat p -> Located (ConLikeP p)
pat_con  = L SrcSpan
_ ConLikeP (GhcPass 'Typechecked)
pcon
                         , pat_args :: forall p. Pat p -> HsConPatDetails p
pat_args = HsConPatDetails (GhcPass 'Typechecked)
ps})
  | RealDataCon DataCon
con <- ConLikeP (GhcPass 'Typechecked)
pcon
  , TyCon -> Bool
isProductTyCon (DataCon -> TyCon
dataConTyCon DataCon
con)
  = (GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Bool)
-> [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Bool
forall (p :: Pass). LPat (GhcPass p) -> Bool
is_triv_lpat (HsConPatDetails (GhcPass 'Typechecked)
-> [XRec (GhcPass 'Typechecked) Pat]
forall p. HsConPatDetails p -> [LPat p]
hsConPatArgs HsConPatDetails (GhcPass 'Typechecked)
ps)
is_flat_prod_pat Pat (GhcPass 'Typechecked)
_ = Bool
False

is_triv_lpat :: LPat (GhcPass p) -> Bool
is_triv_lpat :: forall (p :: Pass). LPat (GhcPass p) -> Bool
is_triv_lpat = Pat (GhcPass p) -> Bool
forall (p :: Pass). Pat (GhcPass p) -> Bool
is_triv_pat (Pat (GhcPass p) -> Bool)
-> (GenLocated SrcSpan (Pat (GhcPass p)) -> Pat (GhcPass p))
-> GenLocated SrcSpan (Pat (GhcPass p))
-> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. GenLocated SrcSpan (Pat (GhcPass p)) -> Pat (GhcPass p)
forall l e. GenLocated l e -> e
unLoc

is_triv_pat :: Pat (GhcPass p) -> Bool
is_triv_pat :: forall (p :: Pass). Pat (GhcPass p) -> Bool
is_triv_pat (VarPat {})  = Bool
True
is_triv_pat (WildPat{})  = Bool
True
is_triv_pat (ParPat XParPat (GhcPass p)
_ LPat (GhcPass p)
p) = LPat (GhcPass p) -> Bool
forall (p :: Pass). LPat (GhcPass p) -> Bool
is_triv_lpat LPat (GhcPass p)
p
is_triv_pat Pat (GhcPass p)
_            = Bool
False


{- *********************************************************************
*                                                                      *
  Creating big tuples and their types for full Haskell expressions.
  They work over *Ids*, and create tuples replete with their types,
  which is whey they are not in GHC.Hs.Utils.
*                                                                      *
********************************************************************* -}

mkLHsPatTup :: [LPat GhcTc] -> LPat GhcTc
mkLHsPatTup :: [XRec (GhcPass 'Typechecked) Pat]
-> XRec (GhcPass 'Typechecked) Pat
mkLHsPatTup []     = Pat (GhcPass 'Typechecked)
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall e. e -> Located e
noLoc (Pat (GhcPass 'Typechecked)
 -> GenLocated SrcSpan (Pat (GhcPass 'Typechecked)))
-> Pat (GhcPass 'Typechecked)
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$ [XRec (GhcPass 'Typechecked) Pat]
-> Boxity -> Pat (GhcPass 'Typechecked)
mkVanillaTuplePat [] Boxity
Boxed
mkLHsPatTup [XRec (GhcPass 'Typechecked) Pat
lpat] = XRec (GhcPass 'Typechecked) Pat
lpat
mkLHsPatTup [XRec (GhcPass 'Typechecked) Pat]
lpats  = SrcSpan
-> Pat (GhcPass 'Typechecked)
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall l e. l -> e -> GenLocated l e
L (GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> SrcSpan
forall l e. GenLocated l e -> l
getLoc ([GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall a. [a] -> a
head [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
[XRec (GhcPass 'Typechecked) Pat]
lpats)) (Pat (GhcPass 'Typechecked)
 -> GenLocated SrcSpan (Pat (GhcPass 'Typechecked)))
-> Pat (GhcPass 'Typechecked)
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall a b. (a -> b) -> a -> b
$
                     [XRec (GhcPass 'Typechecked) Pat]
-> Boxity -> Pat (GhcPass 'Typechecked)
mkVanillaTuplePat [XRec (GhcPass 'Typechecked) Pat]
lpats Boxity
Boxed

mkVanillaTuplePat :: [LPat GhcTc] -> Boxity -> Pat GhcTc
-- A vanilla tuple pattern simply gets its type from its sub-patterns
mkVanillaTuplePat :: [XRec (GhcPass 'Typechecked) Pat]
-> Boxity -> Pat (GhcPass 'Typechecked)
mkVanillaTuplePat [XRec (GhcPass 'Typechecked) Pat]
pats Boxity
box = XTuplePat (GhcPass 'Typechecked)
-> [XRec (GhcPass 'Typechecked) Pat]
-> Boxity
-> Pat (GhcPass 'Typechecked)
forall p. XTuplePat p -> [LPat p] -> Boxity -> Pat p
TuplePat ((GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Mult)
-> [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))] -> [Mult]
forall a b. (a -> b) -> [a] -> [b]
map GenLocated SrcSpan (Pat (GhcPass 'Typechecked)) -> Mult
XRec (GhcPass 'Typechecked) Pat -> Mult
hsLPatType [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
[XRec (GhcPass 'Typechecked) Pat]
pats) [XRec (GhcPass 'Typechecked) Pat]
pats Boxity
box

-- The Big equivalents for the source tuple expressions
mkBigLHsVarTupId :: [Id] -> LHsExpr GhcTc
mkBigLHsVarTupId :: [Id] -> LHsExpr (GhcPass 'Typechecked)
mkBigLHsVarTupId [Id]
ids = [LHsExpr (GhcPass 'Typechecked)] -> LHsExpr (GhcPass 'Typechecked)
mkBigLHsTupId ((Id -> LHsExpr (GhcPass 'Typechecked))
-> [Id] -> [LHsExpr (GhcPass 'Typechecked)]
forall a b. (a -> b) -> [a] -> [b]
map Id -> LHsExpr (GhcPass 'Typechecked)
forall (id :: Pass). IdP (GhcPass id) -> LHsExpr (GhcPass id)
nlHsVar [Id]
ids)

mkBigLHsTupId :: [LHsExpr GhcTc] -> LHsExpr GhcTc
mkBigLHsTupId :: [LHsExpr (GhcPass 'Typechecked)] -> LHsExpr (GhcPass 'Typechecked)
mkBigLHsTupId = ([LHsExpr (GhcPass 'Typechecked)]
 -> LHsExpr (GhcPass 'Typechecked))
-> [LHsExpr (GhcPass 'Typechecked)]
-> LHsExpr (GhcPass 'Typechecked)
forall a. ([a] -> a) -> [a] -> a
mkChunkified [LHsExpr (GhcPass 'Typechecked)] -> LHsExpr (GhcPass 'Typechecked)
forall (a :: Pass). [LHsExpr (GhcPass a)] -> LHsExpr (GhcPass a)
mkLHsTupleExpr

-- The Big equivalents for the source tuple patterns
mkBigLHsVarPatTupId :: [Id] -> LPat GhcTc
mkBigLHsVarPatTupId :: [Id] -> XRec (GhcPass 'Typechecked) Pat
mkBigLHsVarPatTupId [Id]
bs = [XRec (GhcPass 'Typechecked) Pat]
-> XRec (GhcPass 'Typechecked) Pat
mkBigLHsPatTupId ((Id -> GenLocated SrcSpan (Pat (GhcPass 'Typechecked)))
-> [Id] -> [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
forall a b. (a -> b) -> [a] -> [b]
map Id -> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall (id :: Pass). IdP (GhcPass id) -> LPat (GhcPass id)
nlVarPat [Id]
bs)

mkBigLHsPatTupId :: [LPat GhcTc] -> LPat GhcTc
mkBigLHsPatTupId :: [XRec (GhcPass 'Typechecked) Pat]
-> XRec (GhcPass 'Typechecked) Pat
mkBigLHsPatTupId = ([GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
 -> GenLocated SrcSpan (Pat (GhcPass 'Typechecked)))
-> [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall a. ([a] -> a) -> [a] -> a
mkChunkified [GenLocated SrcSpan (Pat (GhcPass 'Typechecked))]
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
[XRec (GhcPass 'Typechecked) Pat]
-> XRec (GhcPass 'Typechecked) Pat
mkLHsPatTup

{-
************************************************************************
*                                                                      *
        Code for pattern-matching and other failures
*                                                                      *
************************************************************************

Generally, we handle pattern matching failure like this: let-bind a
fail-variable, and use that variable if the thing fails:
\begin{verbatim}
        let fail.33 = error "Help"
        in
        case x of
                p1 -> ...
                p2 -> fail.33
                p3 -> fail.33
                p4 -> ...
\end{verbatim}
Then
\begin{itemize}
\item
If the case can't fail, then there'll be no mention of @fail.33@, and the
simplifier will later discard it.

\item
If it can fail in only one way, then the simplifier will inline it.

\item
Only if it is used more than once will the let-binding remain.
\end{itemize}

There's a problem when the result of the case expression is of
unboxed type.  Then the type of @fail.33@ is unboxed too, and
there is every chance that someone will change the let into a case:
\begin{verbatim}
        case error "Help" of
          fail.33 -> case ....
\end{verbatim}

which is of course utterly wrong.  Rather than drop the condition that
only boxed types can be let-bound, we just turn the fail into a function
for the primitive case:
\begin{verbatim}
        let fail.33 :: Void -> Int#
            fail.33 = \_ -> error "Help"
        in
        case x of
                p1 -> ...
                p2 -> fail.33 void
                p3 -> fail.33 void
                p4 -> ...
\end{verbatim}

Now @fail.33@ is a function, so it can be let-bound.

We would *like* to use join points here; in fact, these "fail variables" are
paradigmatic join points! Sadly, this breaks pattern synonyms, which desugar as
CPS functions - i.e. they take "join points" as parameters. It's not impossible
to imagine extending our type system to allow passing join points around (very
carefully), but we certainly don't support it now.

99.99% of the time, the fail variables wind up as join points in short order
anyway, and the Void# doesn't do much harm.
-}

mkFailurePair :: CoreExpr       -- Result type of the whole case expression
              -> DsM (CoreBind, -- Binds the newly-created fail variable
                                -- to \ _ -> expression
                      CoreExpr) -- Fail variable applied to realWorld#
-- See Note [Failure thunks and CPR]
mkFailurePair :: CoreExpr -> DsM (Bind Id, CoreExpr)
mkFailurePair CoreExpr
expr
  = do { Id
fail_fun_var <- Mult -> Mult -> DsM Id
newFailLocalDs Mult
Many (Mult
voidPrimTy Mult -> Mult -> Mult
`mkVisFunTyMany` Mult
ty)
       ; Id
fail_fun_arg <- Mult -> Mult -> DsM Id
newSysLocalDs Mult
Many Mult
voidPrimTy
       ; let real_arg :: Id
real_arg = Id -> Id
setOneShotLambda Id
fail_fun_arg
       ; (Bind Id, CoreExpr) -> DsM (Bind Id, CoreExpr)
forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> CoreExpr -> Bind Id
forall b. b -> Expr b -> Bind b
NonRec Id
fail_fun_var (Id -> CoreExpr -> CoreExpr
forall b. b -> Expr b -> Expr b
Lam Id
real_arg CoreExpr
expr),
                 CoreExpr -> CoreExpr -> CoreExpr
forall b. Expr b -> Expr b -> Expr b
App (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
fail_fun_var) (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
voidPrimId)) }
  where
    ty :: Mult
ty = CoreExpr -> Mult
exprType CoreExpr
expr

-- Uses '@mkFailurePair@' to bind the failure case. Infallible matches have
-- neither a failure arg or failure "hole", so nothing is let-bound, and no
-- extraneous Core is produced.
shareFailureHandler :: MatchResult CoreExpr -> MatchResult CoreExpr
shareFailureHandler :: MatchResult CoreExpr -> MatchResult CoreExpr
shareFailureHandler = \case
  mr :: MatchResult CoreExpr
mr@(MR_Infallible DsM CoreExpr
_) -> MatchResult CoreExpr
mr
  MR_Fallible CoreExpr -> DsM CoreExpr
match_fn -> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a. (CoreExpr -> DsM a) -> MatchResult a
MR_Fallible ((CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr)
-> (CoreExpr -> DsM CoreExpr) -> MatchResult CoreExpr
forall a b. (a -> b) -> a -> b
$ \CoreExpr
fail_expr -> do
    (Bind Id
fail_bind, CoreExpr
shared_failure_handler) <- CoreExpr -> DsM (Bind Id, CoreExpr)
mkFailurePair CoreExpr
fail_expr
    CoreExpr
body <- CoreExpr -> DsM CoreExpr
match_fn CoreExpr
shared_failure_handler
    -- Never unboxed, per the above, so always OK for `let` not `case`.
    CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> DsM CoreExpr) -> CoreExpr -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ Bind Id -> CoreExpr -> CoreExpr
forall b. Bind b -> Expr b -> Expr b
Let Bind Id
fail_bind CoreExpr
body

{-
Note [Failure thunks and CPR]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(This note predates join points as formal entities (hence the quotation marks).
We can't use actual join points here (see above); if we did, this would also
solve the CPR problem, since join points don't get CPR'd. See Note [Don't CPR
join points] in GHC.Core.Opt.WorkWrap.)

When we make a failure point we ensure that it
does not look like a thunk. Example:

   let fail = \rw -> error "urk"
   in case x of
        [] -> fail realWorld#
        (y:ys) -> case ys of
                    [] -> fail realWorld#
                    (z:zs) -> (y,z)

Reason: we know that a failure point is always a "join point" and is
entered at most once.  Adding a dummy 'realWorld' token argument makes
it clear that sharing is not an issue.  And that in turn makes it more
CPR-friendly.  This matters a lot: if you don't get it right, you lose
the tail call property.  For example, see #3403.


************************************************************************
*                                                                      *
              Ticks
*                                                                      *
********************************************************************* -}

mkOptTickBox :: [Tickish Id] -> CoreExpr -> CoreExpr
mkOptTickBox :: [Tickish Id] -> CoreExpr -> CoreExpr
mkOptTickBox = (CoreExpr -> [Tickish Id] -> CoreExpr)
-> [Tickish Id] -> CoreExpr -> CoreExpr
forall a b c. (a -> b -> c) -> b -> a -> c
flip ((Tickish Id -> CoreExpr -> CoreExpr)
-> CoreExpr -> [Tickish Id] -> CoreExpr
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Tickish Id -> CoreExpr -> CoreExpr
forall b. Tickish Id -> Expr b -> Expr b
Tick)

mkBinaryTickBox :: Int -> Int -> CoreExpr -> DsM CoreExpr
mkBinaryTickBox :: ConTag -> ConTag -> CoreExpr -> DsM CoreExpr
mkBinaryTickBox ConTag
ixT ConTag
ixF CoreExpr
e = do
       Unique
uq <- TcRnIf DsGblEnv DsLclEnv Unique
forall gbl lcl. TcRnIf gbl lcl Unique
newUnique
       Module
this_mod <- IOEnv (Env DsGblEnv DsLclEnv) Module
forall (m :: * -> *). HasModule m => m Module
getModule
       let bndr1 :: Id
bndr1 = FastString -> Unique -> Mult -> Mult -> Id
mkSysLocal (String -> FastString
fsLit String
"t1") Unique
uq Mult
One Mult
boolTy
         -- It's always sufficient to pattern-match on a boolean with
         -- multiplicity 'One'.
       let
           falseBox :: CoreExpr
falseBox = Tickish Id -> CoreExpr -> CoreExpr
forall b. Tickish Id -> Expr b -> Expr b
Tick (Module -> ConTag -> Tickish Id
forall id. Module -> ConTag -> Tickish id
HpcTick Module
this_mod ConTag
ixF) (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
falseDataConId)
           trueBox :: CoreExpr
trueBox  = Tickish Id -> CoreExpr -> CoreExpr
forall b. Tickish Id -> Expr b -> Expr b
Tick (Module -> ConTag -> Tickish Id
forall id. Module -> ConTag -> Tickish id
HpcTick Module
this_mod ConTag
ixT) (Id -> CoreExpr
forall b. Id -> Expr b
Var Id
trueDataConId)
       --
       CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (CoreExpr -> DsM CoreExpr) -> CoreExpr -> DsM CoreExpr
forall a b. (a -> b) -> a -> b
$ CoreExpr -> Id -> Mult -> [Alt Id] -> CoreExpr
forall b. Expr b -> b -> Mult -> [Alt b] -> Expr b
Case CoreExpr
e Id
bndr1 Mult
boolTy
                       [ (DataCon -> AltCon
DataAlt DataCon
falseDataCon, [], CoreExpr
falseBox)
                       , (DataCon -> AltCon
DataAlt DataCon
trueDataCon,  [], CoreExpr
trueBox)
                       ]



-- *******************************************************************

{- Note [decideBangHood]
~~~~~~~~~~~~~~~~~~~~~~~~
With -XStrict we may make /outermost/ patterns more strict.
E.g.
       let (Just x) = e in ...
          ==>
       let !(Just x) = e in ...
and
       f x = e
          ==>
       f !x = e

This adjustment is done by decideBangHood,

  * Just before constructing an EqnInfo, in GHC.HsToCore.Match
      (matchWrapper and matchSinglePat)

  * When desugaring a pattern-binding in GHC.HsToCore.Binds.dsHsBind

Note that it is /not/ done recursively.  See the -XStrict
spec in the user manual.

Specifically:
   ~pat    => pat    -- when -XStrict (even if pat = ~pat')
   !pat    => !pat   -- always
   pat     => !pat   -- when -XStrict
   pat     => pat    -- otherwise
-}


-- | Use -XStrict to add a ! or remove a ~
-- See Note [decideBangHood]
decideBangHood :: DynFlags
               -> LPat GhcTc  -- ^ Original pattern
               -> LPat GhcTc  -- Pattern with bang if necessary
decideBangHood :: DynFlags
-> XRec (GhcPass 'Typechecked) Pat
-> XRec (GhcPass 'Typechecked) Pat
decideBangHood DynFlags
dflags XRec (GhcPass 'Typechecked) Pat
lpat
  | Bool -> Bool
not (Extension -> DynFlags -> Bool
xopt Extension
LangExt.Strict DynFlags
dflags)
  = XRec (GhcPass 'Typechecked) Pat
lpat
  | Bool
otherwise   --  -XStrict
  = GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
-> GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
forall {p} {l}.
(XRec p Pat ~ GenLocated l (Pat p), XBangPat p ~ NoExtField) =>
GenLocated l (Pat p) -> GenLocated l (Pat p)
go GenLocated SrcSpan (Pat (GhcPass 'Typechecked))
XRec (GhcPass 'Typechecked) Pat
lpat
  where
    go :: GenLocated l (Pat p) -> GenLocated l (Pat p)
go lp :: GenLocated l (Pat p)
lp@(L l
l Pat p
p)
      = case Pat p
p of
           ParPat XParPat p
x XRec p Pat
p    -> l -> Pat p -> GenLocated l (Pat p)
forall l e. l -> e -> GenLocated l e
L l
l (XParPat p -> XRec p Pat -> Pat p
forall p. XParPat p -> LPat p -> Pat p
ParPat XParPat p
x (GenLocated l (Pat p) -> GenLocated l (Pat p)
go GenLocated l (Pat p)
XRec p Pat
p))
           LazyPat XLazyPat p
_ XRec p Pat
lp' -> GenLocated l (Pat p)
XRec p Pat
lp'
           BangPat XBangPat p
_ XRec p Pat
_   -> GenLocated l (Pat p)
lp
           Pat p
_             -> l -> Pat p -> GenLocated l (Pat p)
forall l e. l -> e -> GenLocated l e
L l
l (XBangPat p -> XRec p Pat -> Pat p
forall p. XBangPat p -> LPat p -> Pat p
BangPat NoExtField
XBangPat p
noExtField GenLocated l (Pat p)
XRec p Pat
lp)

isTrueLHsExpr :: LHsExpr GhcTc -> Maybe (CoreExpr -> DsM CoreExpr)

-- Returns Just {..} if we're sure that the expression is True
-- I.e.   * 'True' datacon
--        * 'otherwise' Id
--        * Trivial wappings of these
-- The arguments to Just are any HsTicks that we have found,
-- because we still want to tick then, even it they are always evaluated.
isTrueLHsExpr :: LHsExpr (GhcPass 'Typechecked) -> Maybe (CoreExpr -> DsM CoreExpr)
isTrueLHsExpr (L SrcSpan
_ (HsVar XVar (GhcPass 'Typechecked)
_ (L SrcSpan
_ IdP (GhcPass 'Typechecked)
v)))
  |  Id
IdP (GhcPass 'Typechecked)
v Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
otherwiseIdKey
     Bool -> Bool -> Bool
|| Id
IdP (GhcPass 'Typechecked)
v Id -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Id -> Unique
forall a. Uniquable a => a -> Unique
getUnique Id
trueDataConId
                                              = (CoreExpr -> DsM CoreExpr) -> Maybe (CoreExpr -> DsM CoreExpr)
forall a. a -> Maybe a
Just CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return
        -- trueDataConId doesn't have the same unique as trueDataCon
isTrueLHsExpr (L SrcSpan
_ (HsConLikeOut XConLikeOut (GhcPass 'Typechecked)
_ ConLike
con))
  | ConLike
con ConLike -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` DataCon -> Unique
forall a. Uniquable a => a -> Unique
getUnique DataCon
trueDataCon = (CoreExpr -> DsM CoreExpr) -> Maybe (CoreExpr -> DsM CoreExpr)
forall a. a -> Maybe a
Just CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return
isTrueLHsExpr (L SrcSpan
_ (HsTick XTick (GhcPass 'Typechecked)
_ Tickish (IdP (GhcPass 'Typechecked))
tickish LHsExpr (GhcPass 'Typechecked)
e))
    | Just CoreExpr -> DsM CoreExpr
ticks <- LHsExpr (GhcPass 'Typechecked) -> Maybe (CoreExpr -> DsM CoreExpr)
isTrueLHsExpr LHsExpr (GhcPass 'Typechecked)
e
    = (CoreExpr -> DsM CoreExpr) -> Maybe (CoreExpr -> DsM CoreExpr)
forall a. a -> Maybe a
Just (\CoreExpr
x -> do CoreExpr
wrapped <- CoreExpr -> DsM CoreExpr
ticks CoreExpr
x
                     CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (Tickish Id -> CoreExpr -> CoreExpr
forall b. Tickish Id -> Expr b -> Expr b
Tick Tickish Id
Tickish (IdP (GhcPass 'Typechecked))
tickish CoreExpr
wrapped))
   -- This encodes that the result is constant True for Hpc tick purposes;
   -- which is specifically what isTrueLHsExpr is trying to find out.
isTrueLHsExpr (L SrcSpan
_ (HsBinTick XBinTick (GhcPass 'Typechecked)
_ ConTag
ixT ConTag
_ LHsExpr (GhcPass 'Typechecked)
e))
    | Just CoreExpr -> DsM CoreExpr
ticks <- LHsExpr (GhcPass 'Typechecked) -> Maybe (CoreExpr -> DsM CoreExpr)
isTrueLHsExpr LHsExpr (GhcPass 'Typechecked)
e
    = (CoreExpr -> DsM CoreExpr) -> Maybe (CoreExpr -> DsM CoreExpr)
forall a. a -> Maybe a
Just (\CoreExpr
x -> do CoreExpr
e <- CoreExpr -> DsM CoreExpr
ticks CoreExpr
x
                     Module
this_mod <- IOEnv (Env DsGblEnv DsLclEnv) Module
forall (m :: * -> *). HasModule m => m Module
getModule
                     CoreExpr -> DsM CoreExpr
forall (m :: * -> *) a. Monad m => a -> m a
return (Tickish Id -> CoreExpr -> CoreExpr
forall b. Tickish Id -> Expr b -> Expr b
Tick (Module -> ConTag -> Tickish Id
forall id. Module -> ConTag -> Tickish id
HpcTick Module
this_mod ConTag
ixT) CoreExpr
e))

isTrueLHsExpr (L SrcSpan
_ (HsPar XPar (GhcPass 'Typechecked)
_ LHsExpr (GhcPass 'Typechecked)
e))   = LHsExpr (GhcPass 'Typechecked) -> Maybe (CoreExpr -> DsM CoreExpr)
isTrueLHsExpr LHsExpr (GhcPass 'Typechecked)
e
isTrueLHsExpr LHsExpr (GhcPass 'Typechecked)
_                   = Maybe (CoreExpr -> DsM CoreExpr)
forall a. Maybe a
Nothing