{-# LANGUAGE TypeFamilies #-}

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

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


Pattern-matching constructors
-}

module GHC.HsToCore.Match.Constructor ( matchConFamily, matchPatSyn ) where

import GHC.Prelude

import {-# SOURCE #-} GHC.HsToCore.Match ( match )

import GHC.Hs
import GHC.HsToCore.Binds
import GHC.Core.ConLike
import GHC.Types.Basic ( Origin(..) )
import GHC.Tc.Utils.TcType
import GHC.Core.Multiplicity
import GHC.HsToCore.Monad
import GHC.HsToCore.Utils
import GHC.Core ( CoreExpr )
import GHC.Core.Make ( mkCoreLets )
import GHC.Utils.Misc
import GHC.Types.Id
import GHC.Types.Name.Env
import GHC.Types.FieldLabel ( flSelector )
import GHC.Types.SrcLoc
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Panic.Plain
import Control.Monad(liftM)
import Data.List (groupBy)
import Data.List.NonEmpty (NonEmpty(..))

{-
We are confronted with the first column of patterns in a set of
equations, all beginning with constructors from one ``family'' (e.g.,
@[]@ and @:@ make up the @List@ ``family'').  We want to generate the
alternatives for a @Case@ expression.  There are several choices:
\begin{enumerate}
\item
Generate an alternative for every constructor in the family, whether
they are used in this set of equations or not; this is what the Wadler
chapter does.
\begin{description}
\item[Advantages:]
(a)~Simple.  (b)~It may also be that large sparsely-used constructor
families are mainly handled by the code for literals.
\item[Disadvantages:]
(a)~Not practical for large sparsely-used constructor families, e.g.,
the ASCII character set.  (b)~Have to look up a list of what
constructors make up the whole family.
\end{description}

\item
Generate an alternative for each constructor used, then add a default
alternative in case some constructors in the family weren't used.
\begin{description}
\item[Advantages:]
(a)~Alternatives aren't generated for unused constructors.  (b)~The
STG is quite happy with defaults.  (c)~No lookup in an environment needed.
\item[Disadvantages:]
(a)~A spurious default alternative may be generated.
\end{description}

\item
``Do it right:'' generate an alternative for each constructor used,
and add a default alternative if all constructors in the family
weren't used.
\begin{description}
\item[Advantages:]
(a)~You will get cases with only one alternative (and no default),
which should be amenable to optimisation.  Tuples are a common example.
\item[Disadvantages:]
(b)~Have to look up constructor families in TDE (as above).
\end{description}
\end{enumerate}

We are implementing the ``do-it-right'' option for now.  The arguments
to @matchConFamily@ are the same as to @match@; the extra @Int@
returned is the number of constructors in the family.

The function @matchConFamily@ is concerned with this
have-we-used-all-the-constructors? question; the local function
@match_cons_used@ does all the real work.
-}

matchConFamily :: NonEmpty Id
               -> Type
               -> NonEmpty (NonEmpty EquationInfo)
               -> DsM (MatchResult CoreExpr)
-- Each group of eqns is for a single constructor
matchConFamily :: NonEmpty Id
-> Type
-> NonEmpty (NonEmpty EquationInfo)
-> DsM (MatchResult CoreExpr)
matchConFamily (Id
var :| [Id]
vars) Type
ty NonEmpty (NonEmpty EquationInfo)
groups
  = do let mult :: Type
mult = Id -> Type
idMult Id
var
           -- Each variable in the argument list correspond to one column in the
           -- pattern matching equations. Its multiplicity is the context
           -- multiplicity of the pattern. We extract that multiplicity, so that
           -- 'matchOneconLike' knows the context multiplicity, in case it needs
           -- to come up with new variables.
       NonEmpty (CaseAlt DataCon)
alts <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap CaseAlt ConLike -> CaseAlt DataCon
toRealAlt forall b c a. (b -> c) -> (a -> b) -> a -> c
. [Id]
-> Type -> Type -> NonEmpty EquationInfo -> DsM (CaseAlt ConLike)
matchOneConLike [Id]
vars Type
ty Type
mult) NonEmpty (NonEmpty EquationInfo)
groups
       forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> Type -> NonEmpty (CaseAlt DataCon) -> MatchResult CoreExpr
mkCoAlgCaseMatchResult Id
var Type
ty NonEmpty (CaseAlt DataCon)
alts)
  where
    toRealAlt :: CaseAlt ConLike -> CaseAlt DataCon
toRealAlt CaseAlt ConLike
alt = case forall a. CaseAlt a -> a
alt_pat CaseAlt ConLike
alt of
        RealDataCon DataCon
dcon -> CaseAlt ConLike
alt{ alt_pat :: DataCon
alt_pat = DataCon
dcon }
        ConLike
_ -> forall a. String -> a
panic String
"matchConFamily: not RealDataCon"

matchPatSyn :: NonEmpty Id
            -> Type
            -> NonEmpty EquationInfo
            -> DsM (MatchResult CoreExpr)
matchPatSyn :: NonEmpty Id
-> Type -> NonEmpty EquationInfo -> DsM (MatchResult CoreExpr)
matchPatSyn (Id
var :| [Id]
vars) Type
ty NonEmpty EquationInfo
eqns
  = do let mult :: Type
mult = Id -> Type
idMult Id
var
       CaseAlt PatSyn
alt <- forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap CaseAlt ConLike -> CaseAlt PatSyn
toSynAlt forall a b. (a -> b) -> a -> b
$ [Id]
-> Type -> Type -> NonEmpty EquationInfo -> DsM (CaseAlt ConLike)
matchOneConLike [Id]
vars Type
ty Type
mult NonEmpty EquationInfo
eqns
       forall (m :: * -> *) a. Monad m => a -> m a
return (Id -> Type -> CaseAlt PatSyn -> MatchResult CoreExpr
mkCoSynCaseMatchResult Id
var Type
ty CaseAlt PatSyn
alt)
  where
    toSynAlt :: CaseAlt ConLike -> CaseAlt PatSyn
toSynAlt CaseAlt ConLike
alt = case forall a. CaseAlt a -> a
alt_pat CaseAlt ConLike
alt of
        PatSynCon PatSyn
psyn -> CaseAlt ConLike
alt{ alt_pat :: PatSyn
alt_pat = PatSyn
psyn }
        ConLike
_ -> forall a. String -> a
panic String
"matchPatSyn: not PatSynCon"

type ConArgPats = HsConPatDetails GhcTc

matchOneConLike :: [Id]
                -> Type
                -> Mult
                -> NonEmpty EquationInfo
                -> DsM (CaseAlt ConLike)
matchOneConLike :: [Id]
-> Type -> Type -> NonEmpty EquationInfo -> DsM (CaseAlt ConLike)
matchOneConLike [Id]
vars Type
ty Type
mult (EquationInfo
eqn1 :| [EquationInfo]
eqns)   -- All eqns for a single constructor
  = do  { let inst_tys :: [Type]
inst_tys = forall a. HasCallStack => Bool -> a -> a
assert (forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Id -> Bool
tcIsTcTyVar [Id]
ex_tvs) forall a b. (a -> b) -> a -> b
$
                           -- ex_tvs can only be tyvars as data types in source
                           -- Haskell cannot mention covar yet (Aug 2018).
                         forall a. HasCallStack => Bool -> a -> a
assert ([Id]
tvs1 forall a b. [a] -> [b] -> Bool
`equalLength` [Id]
ex_tvs) forall a b. (a -> b) -> a -> b
$
                         [Type]
arg_tys forall a. [a] -> [a] -> [a]
++ [Id] -> [Type]
mkTyVarTys [Id]
tvs1

              val_arg_tys :: [Scaled Type]
val_arg_tys = ConLike -> [Type] -> [Scaled Type]
conLikeInstOrigArgTys ConLike
con1 [Type]
inst_tys
        -- dataConInstOrigArgTys takes the univ and existential tyvars
        -- and returns the types of the *value* args, which is what we want

              match_group :: [Id]
                          -> [(ConArgPats, EquationInfo)] -> DsM (MatchResult CoreExpr)
              -- All members of the group have compatible ConArgPats
              match_group :: [Id] -> [(ConArgPats, EquationInfo)] -> DsM (MatchResult CoreExpr)
match_group [Id]
arg_vars [(ConArgPats, EquationInfo)]
arg_eqn_prs
                = forall a. HasCallStack => Bool -> a -> a
assert (forall (f :: * -> *) a. Foldable f => f a -> Bool
notNull [(ConArgPats, EquationInfo)]
arg_eqn_prs) forall a b. (a -> b) -> a -> b
$
                  do { ([CoreExpr -> CoreExpr]
wraps, [EquationInfo]
eqns') <- forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
liftM forall a b. [(a, b)] -> ([a], [b])
unzip (forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM (HsConDetails
   (HsPatSigType (GhcPass 'Renamed))
   (GenLocated SrcSpanAnnA (Pat GhcTc))
   (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
 EquationInfo)
-> IOEnv
     (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
shift [(ConArgPats, EquationInfo)]
arg_eqn_prs)
                     ; let group_arg_vars :: [Id]
group_arg_vars = [Id] -> [(ConArgPats, EquationInfo)] -> [Id]
select_arg_vars [Id]
arg_vars [(ConArgPats, EquationInfo)]
arg_eqn_prs
                     ; MatchResult CoreExpr
match_result <- [Id] -> Type -> [EquationInfo] -> DsM (MatchResult CoreExpr)
match ([Id]
group_arg_vars forall a. [a] -> [a] -> [a]
++ [Id]
vars) Type
ty [EquationInfo]
eqns'
                     ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
foldr1 forall b c a. (b -> c) -> (a -> b) -> a -> c
(.) [CoreExpr -> CoreExpr]
wraps forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> MatchResult CoreExpr
match_result
                     }

              shift :: (HsConDetails
   (HsPatSigType (GhcPass 'Renamed))
   (GenLocated SrcSpanAnnA (Pat GhcTc))
   (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))),
 EquationInfo)
-> IOEnv
     (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
shift (HsConDetails
  (HsPatSigType (GhcPass 'Renamed))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
_, eqn :: EquationInfo
eqn@(EqnInfo
                             { eqn_pats :: EquationInfo -> [Pat GhcTc]
eqn_pats = ConPat
                               { pat_args :: forall p. Pat p -> HsConPatDetails p
pat_args = ConArgPats
args
                               , pat_con_ext :: forall p. Pat p -> XConPat p
pat_con_ext = ConPatTc
                                 { cpt_tvs :: ConPatTc -> [Id]
cpt_tvs = [Id]
tvs
                                 , cpt_dicts :: ConPatTc -> [Id]
cpt_dicts = [Id]
ds
                                 , cpt_binds :: ConPatTc -> TcEvBinds
cpt_binds = TcEvBinds
bind
                                 }
                               } : [Pat GhcTc]
pats
                             }))
                = do [CoreBind]
ds_bind <- TcEvBinds -> DsM [CoreBind]
dsTcEvBinds TcEvBinds
bind
                     forall (m :: * -> *) a. Monad m => a -> m a
return ( [(Id, Id)] -> CoreExpr -> CoreExpr
wrapBinds ([Id]
tvs forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
tvs1)
                            forall b c a. (b -> c) -> (a -> b) -> a -> c
. [(Id, Id)] -> CoreExpr -> CoreExpr
wrapBinds ([Id]
ds  forall a b. [a] -> [b] -> [(a, b)]
`zip` [Id]
dicts1)
                            forall b c a. (b -> c) -> (a -> b) -> a -> c
. [CoreBind] -> CoreExpr -> CoreExpr
mkCoreLets [CoreBind]
ds_bind
                            , EquationInfo
eqn { eqn_orig :: Origin
eqn_orig = Origin
Generated
                                  , eqn_pats :: [Pat GhcTc]
eqn_pats = [Scaled Type] -> ConArgPats -> [Pat GhcTc]
conArgPats [Scaled Type]
val_arg_tys ConArgPats
args forall a. [a] -> [a] -> [a]
++ [Pat GhcTc]
pats }
                            )
              shift (HsConDetails
  (HsPatSigType (GhcPass 'Renamed))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
  (HsRecFields GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc)))
_, (EqnInfo { eqn_pats :: EquationInfo -> [Pat GhcTc]
eqn_pats = [Pat GhcTc]
ps })) = forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"matchOneCon/shift" (forall a. Outputable a => a -> SDoc
ppr [Pat GhcTc]
ps)
        ; let scaled_arg_tys :: [Scaled Type]
scaled_arg_tys = forall a b. (a -> b) -> [a] -> [b]
map (forall a. Type -> Scaled a -> Scaled a
scaleScaled Type
mult) [Scaled Type]
val_arg_tys
            -- The 'val_arg_tys' are taken from the data type definition, they
            -- do not take into account the context multiplicity, therefore we
            -- need to scale them back to get the correct context multiplicity
            -- to desugar the sub-pattern in each field. We need to know these
            -- multiplicity because of the invariant that, in Core, binders in a
            -- constructor pattern must be scaled by the multiplicity of the
            -- case. See Note [Case expression invariants].
        ; [Id]
arg_vars <- [Scaled Type] -> ConArgPats -> DsM [Id]
selectConMatchVars [Scaled Type]
scaled_arg_tys ConArgPats
args1
                -- Use the first equation as a source of
                -- suggestions for the new variables

        -- Divide into sub-groups; see Note [Record patterns]
        ; let groups :: [[(ConArgPats, EquationInfo)]]
              groups :: [[(ConArgPats, EquationInfo)]]
groups = forall a. (a -> a -> Bool) -> [a] -> [[a]]
groupBy forall a. (ConArgPats, a) -> (ConArgPats, a) -> Bool
compatible_pats [ (forall p. Pat p -> HsConPatDetails p
pat_args (EquationInfo -> Pat GhcTc
firstPat EquationInfo
eqn), EquationInfo
eqn)
                                               | EquationInfo
eqn <- EquationInfo
eqn1forall a. a -> [a] -> [a]
:[EquationInfo]
eqns ]

        ; [MatchResult CoreExpr]
match_results <- forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
mapM ([Id] -> [(ConArgPats, EquationInfo)] -> DsM (MatchResult CoreExpr)
match_group [Id]
arg_vars) [[(ConArgPats, EquationInfo)]]
groups

        ; forall (m :: * -> *) a. Monad m => a -> m a
return forall a b. (a -> b) -> a -> b
$ MkCaseAlt{ alt_pat :: ConLike
alt_pat = ConLike
con1,
                              alt_bndrs :: [Id]
alt_bndrs = [Id]
tvs1 forall a. [a] -> [a] -> [a]
++ [Id]
dicts1 forall a. [a] -> [a] -> [a]
++ [Id]
arg_vars,
                              alt_wrapper :: HsWrapper
alt_wrapper = HsWrapper
wrapper1,
                              alt_result :: MatchResult CoreExpr
alt_result = forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
foldr1 MatchResult CoreExpr
-> MatchResult CoreExpr -> MatchResult CoreExpr
combineMatchResults [MatchResult CoreExpr]
match_results } }
  where
    ConPat { pat_con :: forall p. Pat p -> XRec p (ConLikeP p)
pat_con = L SrcSpanAnnN
_ ConLike
con1
           , pat_args :: forall p. Pat p -> HsConPatDetails p
pat_args = ConArgPats
args1
           , pat_con_ext :: forall p. Pat p -> XConPat p
pat_con_ext = ConPatTc
             { cpt_arg_tys :: ConPatTc -> [Type]
cpt_arg_tys = [Type]
arg_tys
             , cpt_wrap :: ConPatTc -> HsWrapper
cpt_wrap = HsWrapper
wrapper1
             , cpt_tvs :: ConPatTc -> [Id]
cpt_tvs = [Id]
tvs1
             , cpt_dicts :: ConPatTc -> [Id]
cpt_dicts = [Id]
dicts1
             }
           } = EquationInfo -> Pat GhcTc
firstPat EquationInfo
eqn1
    fields1 :: [Name]
fields1 = forall a b. (a -> b) -> [a] -> [b]
map FieldLabel -> Name
flSelector (ConLike -> [FieldLabel]
conLikeFieldLabels ConLike
con1)

    ex_tvs :: [Id]
ex_tvs = ConLike -> [Id]
conLikeExTyCoVars ConLike
con1

    -- Choose the right arg_vars in the right order for this group
    -- Note [Record patterns]
    select_arg_vars :: [Id] -> [(ConArgPats, EquationInfo)] -> [Id]
    select_arg_vars :: [Id] -> [(ConArgPats, EquationInfo)] -> [Id]
select_arg_vars [Id]
arg_vars ((ConArgPats
arg_pats, EquationInfo
_) : [(ConArgPats, EquationInfo)]
_)
      | RecCon HsRecFields GhcTc (LPat GhcTc)
flds <- ConArgPats
arg_pats
      , let rpats :: [LHsRecField GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))]
rpats = forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds HsRecFields GhcTc (LPat GhcTc)
flds
      , Bool -> Bool
not (forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LHsRecField GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))]
rpats)     -- Treated specially; cf conArgPats
      = forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr ([Name]
fields1 forall a b. [a] -> [b] -> Bool
`equalLength` [Id]
arg_vars)
                  (forall a. Outputable a => a -> SDoc
ppr ConLike
con1 SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [Name]
fields1 SDoc -> SDoc -> SDoc
$$ forall a. Outputable a => a -> SDoc
ppr [Id]
arg_vars) forall a b. (a -> b) -> a -> b
$
        forall a b. (a -> b) -> [a] -> [b]
map GenLocated
  SrcSpanAnnA
  (HsFieldBind
     (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
     (GenLocated SrcSpanAnnA (Pat GhcTc)))
-> Id
lookup_fld [LHsRecField GhcTc (GenLocated SrcSpanAnnA (Pat GhcTc))]
rpats
      | Bool
otherwise
      = [Id]
arg_vars
      where
        fld_var_env :: NameEnv Id
fld_var_env = forall a. [(Name, a)] -> NameEnv a
mkNameEnv forall a b. (a -> b) -> a -> b
$ forall a b. String -> [a] -> [b] -> [(a, b)]
zipEqual String
"get_arg_vars" [Name]
fields1 [Id]
arg_vars
        lookup_fld :: GenLocated
  SrcSpanAnnA
  (HsFieldBind
     (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
     (GenLocated SrcSpanAnnA (Pat GhcTc)))
-> Id
lookup_fld (L SrcSpanAnnA
_ HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
rpat) = forall a. NameEnv a -> Name -> a
lookupNameEnv_NF NameEnv Id
fld_var_env
                                            (Id -> Name
idName (forall arg. HsRecField GhcTc arg -> Id
hsRecFieldId HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
rpat))
    select_arg_vars [Id]
_ [] = forall a. String -> a
panic String
"matchOneCon/select_arg_vars []"

-----------------
compatible_pats :: (ConArgPats,a) -> (ConArgPats,a) -> Bool
-- Two constructors have compatible argument patterns if the number
-- and order of sub-matches is the same in both cases
compatible_pats :: forall a. (ConArgPats, a) -> (ConArgPats, a) -> Bool
compatible_pats (RecCon HsRecFields GhcTc (LPat GhcTc)
flds1, a
_) (RecCon HsRecFields GhcTc (LPat GhcTc)
flds2, a
_) = HsRecFields GhcTc (LPat GhcTc)
-> HsRecFields GhcTc (LPat GhcTc) -> Bool
same_fields HsRecFields GhcTc (LPat GhcTc)
flds1 HsRecFields GhcTc (LPat GhcTc)
flds2
compatible_pats (RecCon HsRecFields GhcTc (LPat GhcTc)
flds1, a
_) (ConArgPats, a)
_                 = forall (t :: * -> *) a. Foldable t => t a -> Bool
null (forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds HsRecFields GhcTc (LPat GhcTc)
flds1)
compatible_pats (ConArgPats, a)
_                 (RecCon HsRecFields GhcTc (LPat GhcTc)
flds2, a
_) = forall (t :: * -> *) a. Foldable t => t a -> Bool
null (forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds HsRecFields GhcTc (LPat GhcTc)
flds2)
compatible_pats (ConArgPats, a)
_                 (ConArgPats, a)
_                 = Bool
True -- Prefix or infix con

same_fields :: HsRecFields GhcTc (LPat GhcTc) -> HsRecFields GhcTc (LPat GhcTc)
            -> Bool
same_fields :: HsRecFields GhcTc (LPat GhcTc)
-> HsRecFields GhcTc (LPat GhcTc) -> Bool
same_fields HsRecFields GhcTc (LPat GhcTc)
flds1 HsRecFields GhcTc (LPat GhcTc)
flds2
  = forall a b. (a -> b -> Bool) -> [a] -> [b] -> Bool
all2 (\(L SrcSpanAnnA
_ HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
f1) (L SrcSpanAnnA
_ HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
f2)
                          -> forall arg. HsRecField GhcTc arg -> Id
hsRecFieldId HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
f1 forall a. Eq a => a -> a -> Bool
== forall arg. HsRecField GhcTc arg -> Id
hsRecFieldId HsFieldBind
  (GenLocated (SrcAnn NoEpAnns) (FieldOcc GhcTc))
  (GenLocated SrcSpanAnnA (Pat GhcTc))
f2)
         (forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds HsRecFields GhcTc (LPat GhcTc)
flds1) (forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds HsRecFields GhcTc (LPat GhcTc)
flds2)


-----------------
selectConMatchVars :: [Scaled Type] -> ConArgPats -> DsM [Id]
selectConMatchVars :: [Scaled Type] -> ConArgPats -> DsM [Id]
selectConMatchVars [Scaled Type]
arg_tys ConArgPats
con
  = case ConArgPats
con of
      RecCon {}      -> [Scaled Type] -> DsM [Id]
newSysLocalsDs [Scaled Type]
arg_tys
      PrefixCon [HsPatSigType (NoGhcTc GhcTc)]
_ [LPat GhcTc]
ps -> [(Type, Pat GhcTc)] -> DsM [Id]
selectMatchVars (forall {a} {l} {b}. [Scaled a] -> [GenLocated l b] -> [(Type, b)]
zipMults [Scaled Type]
arg_tys [LPat GhcTc]
ps)
      InfixCon LPat GhcTc
p1 LPat GhcTc
p2 -> [(Type, Pat GhcTc)] -> DsM [Id]
selectMatchVars (forall {a} {l} {b}. [Scaled a] -> [GenLocated l b] -> [(Type, b)]
zipMults [Scaled Type]
arg_tys [LPat GhcTc
p1, LPat GhcTc
p2])
  where
    zipMults :: [Scaled a] -> [GenLocated l b] -> [(Type, b)]
zipMults = forall a b c. String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual String
"selectConMatchVar" (\Scaled a
a GenLocated l b
b -> (forall a. Scaled a -> Type
scaledMult Scaled a
a, forall l e. GenLocated l e -> e
unLoc GenLocated l b
b))

conArgPats :: [Scaled Type]-- Instantiated argument types
                          -- Used only to fill in the types of WildPats, which
                          -- are probably never looked at anyway
           -> ConArgPats
           -> [Pat GhcTc]
conArgPats :: [Scaled Type] -> ConArgPats -> [Pat GhcTc]
conArgPats [Scaled Type]
_arg_tys (PrefixCon [HsPatSigType (NoGhcTc GhcTc)]
_ [LPat GhcTc]
ps) = forall a b. (a -> b) -> [a] -> [b]
map forall l e. GenLocated l e -> e
unLoc [LPat GhcTc]
ps
conArgPats [Scaled Type]
_arg_tys (InfixCon LPat GhcTc
p1 LPat GhcTc
p2) = [forall l e. GenLocated l e -> e
unLoc LPat GhcTc
p1, forall l e. GenLocated l e -> e
unLoc LPat GhcTc
p2]
conArgPats  [Scaled Type]
arg_tys (RecCon (HsRecFields { rec_flds :: forall p arg. HsRecFields p arg -> [LHsRecField p arg]
rec_flds = [LHsRecField GhcTc (LPat GhcTc)]
rpats }))
  | forall (t :: * -> *) a. Foldable t => t a -> Bool
null [LHsRecField GhcTc (LPat GhcTc)]
rpats = forall a b. (a -> b) -> [a] -> [b]
map forall p. XWildPat p -> Pat p
WildPat (forall a b. (a -> b) -> [a] -> [b]
map forall a. Scaled a -> a
scaledThing [Scaled Type]
arg_tys)
        -- Important special case for C {}, which can be used for a
        -- datacon that isn't declared to have fields at all
  | Bool
otherwise  = forall a b. (a -> b) -> [a] -> [b]
map (forall l e. GenLocated l e -> e
unLoc forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall lhs rhs. HsFieldBind lhs rhs -> rhs
hfbRHS forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall l e. GenLocated l e -> e
unLoc) [LHsRecField GhcTc (LPat GhcTc)]
rpats

{-
Note [Record patterns]
~~~~~~~~~~~~~~~~~~~~~~
Consider
         data T = T { x,y,z :: Bool }

         f (T { y=True, x=False }) = ...

We must match the patterns IN THE ORDER GIVEN, thus for the first
one we match y=True before x=False.  See #246; or imagine
matching against (T { y=False, x=undefined }): should fail without
touching the undefined.

Now consider:

         f (T { y=True, x=False }) = ...
         f (T { x=True, y= False}) = ...

In the first we must test y first; in the second we must test x
first.  So we must divide even the equations for a single constructor
T into sub-groups, based on whether they match the same field in the
same order.  That's what the (groupBy compatible_pats) grouping.

All non-record patterns are "compatible" in this sense, because the
positional patterns (T a b) and (a `T` b) all match the arguments
in order.  Also T {} is special because it's equivalent to (T _ _).
Hence the (null rpats) checks here and there.

-}