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

    Pattern-matching constructors
    -}

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

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

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

    #include "HsVersions.h"

    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 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 <- (NonEmpty EquationInfo
     -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt DataCon))
    -> NonEmpty (NonEmpty EquationInfo)
    -> IOEnv (Env DsGblEnv DsLclEnv) (NonEmpty (CaseAlt DataCon))
    forall (t :: * -> *) (m :: * -> *) a b.
    (Traversable t, Monad m) =>
    (a -> m b) -> t a -> m (t b)
    mapM ((CaseAlt ConLike -> CaseAlt DataCon)
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt DataCon)
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap CaseAlt ConLike -> CaseAlt DataCon
    toRealAlt (IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
     -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt DataCon))
    -> (NonEmpty EquationInfo
        -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike))
    -> NonEmpty EquationInfo
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt DataCon)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [Id]
    -> Type
    -> Type
    -> NonEmpty EquationInfo
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    matchOneConLike [Id]
    vars Type
    ty Type
    mult) NonEmpty (NonEmpty EquationInfo)
    groups
           MatchResult CoreExpr -> DsM (MatchResult CoreExpr)
    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 CaseAlt ConLike -> ConLike
    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
    _ -> String -> CaseAlt DataCon
    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 <- (CaseAlt ConLike -> CaseAlt PatSyn)
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt PatSyn)
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    fmap CaseAlt ConLike -> CaseAlt PatSyn
    toSynAlt (IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
     -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt PatSyn))
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt PatSyn)
    forall a b. (a -> b) -> a -> b
    $ [Id]
    -> Type
    -> Type
    -> NonEmpty EquationInfo
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    matchOneConLike [Id]
    vars Type
    ty Type
    mult NonEmpty EquationInfo
    eqns
           MatchResult CoreExpr -> DsM (MatchResult CoreExpr)
    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 CaseAlt ConLike -> ConLike
    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
    _ -> String -> CaseAlt PatSyn
    forall a. String -> a
    panic String
    "matchPatSyn: not PatSynCon"

    type ConArgPats = HsConDetails (LPat GhcTc) (HsRecFields GhcTc (LPat GhcTc))

    matchOneConLike :: [Id]
                    -> Type
                    -> Mult
                    -> NonEmpty EquationInfo
                    -> DsM (CaseAlt ConLike)
    matchOneConLike :: [Id]
    -> Type
    -> Type
    -> NonEmpty EquationInfo
    -> IOEnv (Env DsGblEnv DsLclEnv) (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 = ASSERT( all tcIsTcTyVar ex_tvs )
                               -- ex_tvs can only be tyvars as data types in source
                               -- Haskell cannot mention covar yet (Aug 2018).
                             ASSERT( tvs1 `equalLength` ex_tvs )
                             [Type]
    arg_tys [Type] -> [Type] -> [Type]
    forall a. [a] -> [a] -> [a]
    ++ [Id] -> [Type]
    mkTyVarTys [Id]
    tvs1

                  val_arg_tys :: [Scaled Type]
    val_arg_tys = ConLike -> [Type] -> [Scaled Type]
    conLikeInstOrigArgTys ConLike
    ConLikeP GhcTc
    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
                    = ASSERT( notNull arg_eqn_prs )
                      do { ([CoreExpr -> CoreExpr]
    wraps, [EquationInfo]
    eqns') <- ([(CoreExpr -> CoreExpr, EquationInfo)]
     -> ([CoreExpr -> CoreExpr], [EquationInfo]))
    -> IOEnv
         (Env DsGblEnv DsLclEnv) [(CoreExpr -> CoreExpr, EquationInfo)]
    -> IOEnv
         (Env DsGblEnv DsLclEnv) ([CoreExpr -> CoreExpr], [EquationInfo])
    forall (m :: * -> *) a1 r. Monad m => (a1 -> r) -> m a1 -> m r
    liftM [(CoreExpr -> CoreExpr, EquationInfo)]
    -> ([CoreExpr -> CoreExpr], [EquationInfo])
    forall a b. [(a, b)] -> ([a], [b])
    unzip (((HsConDetails
        (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
      EquationInfo)
     -> IOEnv
          (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo))
    -> [(HsConDetails
           (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
         EquationInfo)]
    -> IOEnv
         (Env DsGblEnv DsLclEnv) [(CoreExpr -> CoreExpr, EquationInfo)]
    forall (t :: * -> *) (m :: * -> *) a b.
    (Traversable t, Monad m) =>
    (a -> m b) -> t a -> m (t b)
    mapM (HsConDetails
       (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
     EquationInfo)
    -> IOEnv
         (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
    shift [(HsConDetails
        (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
      EquationInfo)]
    [(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 [Id] -> [Id] -> [Id]
    forall a. [a] -> [a] -> [a]
    ++ [Id]
    vars) Type
    ty [EquationInfo]
    eqns'
                         ; MatchResult CoreExpr -> DsM (MatchResult CoreExpr)
    forall (m :: * -> *) a. Monad m => a -> m a
    return (MatchResult CoreExpr -> DsM (MatchResult CoreExpr))
    -> MatchResult CoreExpr -> DsM (MatchResult CoreExpr)
    forall a b. (a -> b) -> a -> b
    $ ((CoreExpr -> CoreExpr)
     -> (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr)
    -> [CoreExpr -> CoreExpr] -> CoreExpr -> CoreExpr
    forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
    foldr1 (CoreExpr -> CoreExpr)
    -> (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    (.) [CoreExpr -> CoreExpr]
    wraps (CoreExpr -> CoreExpr)
    -> MatchResult CoreExpr -> MatchResult CoreExpr
    forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
    <$> MatchResult CoreExpr
    match_result
                         }

                  shift :: (HsConDetails
       (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
     EquationInfo)
    -> IOEnv
         (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
    shift (HsConDetails
      (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (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
                         (CoreExpr -> CoreExpr, EquationInfo)
    -> IOEnv
         (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
    forall (m :: * -> *) a. Monad m => a -> m a
    return ( [(Id, Id)] -> CoreExpr -> CoreExpr
    wrapBinds ([Id]
    tvs [Id] -> [Id] -> [(Id, Id)]
    forall a b. [a] -> [b] -> [(a, b)]
    `zip` [Id]
    tvs1)
                                (CoreExpr -> CoreExpr)
    -> (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [(Id, Id)] -> CoreExpr -> CoreExpr
    wrapBinds ([Id]
    ds  [Id] -> [Id] -> [(Id, Id)]
    forall a b. [a] -> [b] -> [(a, b)]
    `zip` [Id]
    dicts1)
                                (CoreExpr -> CoreExpr)
    -> (CoreExpr -> CoreExpr) -> CoreExpr -> CoreExpr
    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 [Pat GhcTc] -> [Pat GhcTc] -> [Pat GhcTc]
    forall a. [a] -> [a] -> [a]
    ++ [Pat GhcTc]
    pats }
                                )
                  shift (HsConDetails
      (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc)))
    _, (EqnInfo { eqn_pats :: EquationInfo -> [Pat GhcTc]
    eqn_pats = [Pat GhcTc]
    ps })) = String
    -> SDoc
    -> IOEnv
         (Env DsGblEnv DsLclEnv) (CoreExpr -> CoreExpr, EquationInfo)
    forall a. HasCallStack => String -> SDoc -> a
    pprPanic String
    "matchOneCon/shift" ([Pat GhcTc] -> SDoc
    forall a. Outputable a => a -> SDoc
    ppr [Pat GhcTc]
    ps)
            ; let scaled_arg_tys :: [Scaled Type]
    scaled_arg_tys = (Scaled Type -> Scaled Type) -> [Scaled Type] -> [Scaled Type]
    forall a b. (a -> b) -> [a] -> [b]
    map (Type -> Scaled Type -> Scaled Type
    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 = ((HsConDetails
        (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
      EquationInfo)
     -> (HsConDetails
           (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
         EquationInfo)
     -> Bool)
    -> [(HsConDetails
           (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
         EquationInfo)]
    -> [[(HsConDetails
            (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
          EquationInfo)]]
    forall a. (a -> a -> Bool) -> [a] -> [[a]]
    groupBy (HsConDetails
       (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
     EquationInfo)
    -> (HsConDetails
          (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
        EquationInfo)
    -> Bool
    forall a. (ConArgPats, a) -> (ConArgPats, a) -> Bool
    compatible_pats [ (Pat GhcTc -> ConArgPats
    forall p. Pat p -> HsConPatDetails p
    pat_args (EquationInfo -> Pat GhcTc
    firstPat EquationInfo
    eqn), EquationInfo
    eqn)
                                                   | EquationInfo
    eqn <- EquationInfo
    eqn1EquationInfo -> [EquationInfo] -> [EquationInfo]
    forall a. a -> [a] -> [a]
    :[EquationInfo]
    eqns ]

            ; [MatchResult CoreExpr]
    match_results <- ([(HsConDetails
         (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
       EquationInfo)]
     -> DsM (MatchResult CoreExpr))
    -> [[(HsConDetails
            (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
          EquationInfo)]]
    -> IOEnv (Env DsGblEnv DsLclEnv) [MatchResult CoreExpr]
    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) [[(HsConDetails
         (Located (Pat GhcTc)) (HsRecFields GhcTc (Located (Pat GhcTc))),
       EquationInfo)]]
    [[(ConArgPats, EquationInfo)]]
    groups

            ; CaseAlt ConLike -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    forall (m :: * -> *) a. Monad m => a -> m a
    return (CaseAlt ConLike
     -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike))
    -> CaseAlt ConLike
    -> IOEnv (Env DsGblEnv DsLclEnv) (CaseAlt ConLike)
    forall a b. (a -> b) -> a -> b
    $ MkCaseAlt :: forall a.
    a -> [Id] -> HsWrapper -> MatchResult CoreExpr -> CaseAlt a
    MkCaseAlt{ alt_pat :: ConLike
    alt_pat = ConLike
    ConLikeP GhcTc
    con1,
                                  alt_bndrs :: [Id]
    alt_bndrs = [Id]
    tvs1 [Id] -> [Id] -> [Id]
    forall a. [a] -> [a] -> [a]
    ++ [Id]
    dicts1 [Id] -> [Id] -> [Id]
    forall a. [a] -> [a] -> [a]
    ++ [Id]
    arg_vars,
                                  alt_wrapper :: HsWrapper
    alt_wrapper = HsWrapper
    wrapper1,
                                  alt_result :: MatchResult CoreExpr
    alt_result = (MatchResult CoreExpr
     -> MatchResult CoreExpr -> MatchResult CoreExpr)
    -> [MatchResult CoreExpr] -> MatchResult CoreExpr
    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 -> Located (ConLikeP p)
    pat_con = L SrcSpan
    _ ConLikeP GhcTc
    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 = (FieldLbl Name -> Name) -> [FieldLbl Name] -> [Name]
    forall a b. (a -> b) -> [a] -> [b]
    map FieldLbl Name -> Name
    forall a. FieldLbl a -> a
    flSelector (ConLike -> [FieldLbl Name]
    conLikeFieldLabels ConLike
    ConLikeP GhcTc
    con1)

        ex_tvs :: [Id]
    ex_tvs = ConLike -> [Id]
    conLikeExTyCoVars ConLike
    ConLikeP GhcTc
    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 (Located (Pat GhcTc))]
    rpats = HsRecFields GhcTc (Located (Pat GhcTc))
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    forall p arg. HsRecFields p arg -> [LHsRecField p arg]
    rec_flds HsRecFields GhcTc (Located (Pat GhcTc))
    HsRecFields GhcTc (LPat GhcTc)
    flds
          , Bool -> Bool
    not ([LHsRecField GhcTc (Located (Pat GhcTc))] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [LHsRecField GhcTc (Located (Pat GhcTc))]
    rpats)     -- Treated specially; cf conArgPats
          = ASSERT2( fields1 `equalLength` arg_vars,
                     ppr con1 $$ ppr fields1 $$ ppr arg_vars )
            (LHsRecField GhcTc (Located (Pat GhcTc)) -> Id)
    -> [LHsRecField GhcTc (Located (Pat GhcTc))] -> [Id]
    forall a b. (a -> b) -> [a] -> [b]
    map LHsRecField GhcTc (Located (Pat GhcTc)) -> Id
    lookup_fld [LHsRecField GhcTc (Located (Pat GhcTc))]
    rpats
          | Bool
    otherwise
          = [Id]
    arg_vars
          where
            fld_var_env :: NameEnv Id
    fld_var_env = [(Name, Id)] -> NameEnv Id
    forall a. [(Name, a)] -> NameEnv a
    mkNameEnv ([(Name, Id)] -> NameEnv Id) -> [(Name, Id)] -> NameEnv Id
    forall a b. (a -> b) -> a -> b
    $ String -> [Name] -> [Id] -> [(Name, Id)]
    forall a b. String -> [a] -> [b] -> [(a, b)]
    zipEqual String
    "get_arg_vars" [Name]
    fields1 [Id]
    arg_vars
            lookup_fld :: LHsRecField GhcTc (Located (Pat GhcTc)) -> Id
    lookup_fld (L SrcSpan
    _ HsRecField GhcTc (Located (Pat GhcTc))
    rpat) = NameEnv Id -> Name -> Id
    forall a. NameEnv a -> Name -> a
    lookupNameEnv_NF NameEnv Id
    fld_var_env
                                                (Id -> Name
    idName (GenLocated SrcSpan Id -> Id
    forall l e. GenLocated l e -> e
    unLoc (HsRecField GhcTc (Located (Pat GhcTc)) -> GenLocated SrcSpan Id
    forall arg. HsRecField GhcTc arg -> GenLocated SrcSpan Id
    hsRecFieldId HsRecField GhcTc (Located (Pat GhcTc))
    rpat)))
        select_arg_vars [Id]
    _ [] = String -> [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)
    _                 = [LHsRecField GhcTc (Located (Pat GhcTc))] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null (HsRecFields GhcTc (Located (Pat GhcTc))
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    forall p arg. HsRecFields p arg -> [LHsRecField p arg]
    rec_flds HsRecFields GhcTc (Located (Pat GhcTc))
    HsRecFields GhcTc (LPat GhcTc)
    flds1)
    compatible_pats (ConArgPats, a)
    _                 (RecCon HsRecFields GhcTc (LPat GhcTc)
    flds2, a
    _) = [LHsRecField GhcTc (Located (Pat GhcTc))] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null (HsRecFields GhcTc (Located (Pat GhcTc))
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    forall p arg. HsRecFields p arg -> [LHsRecField p arg]
    rec_flds HsRecFields GhcTc (Located (Pat GhcTc))
    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
      = (LHsRecField GhcTc (Located (Pat GhcTc))
     -> LHsRecField GhcTc (Located (Pat GhcTc)) -> Bool)
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    -> Bool
    forall a b. (a -> b -> Bool) -> [a] -> [b] -> Bool
    all2 (\(L SrcSpan
    _ HsRecField GhcTc (Located (Pat GhcTc))
    f1) (L SrcSpan
    _ HsRecField GhcTc (Located (Pat GhcTc))
    f2)
                              -> GenLocated SrcSpan Id -> Id
    forall l e. GenLocated l e -> e
    unLoc (HsRecField GhcTc (Located (Pat GhcTc)) -> GenLocated SrcSpan Id
    forall arg. HsRecField GhcTc arg -> GenLocated SrcSpan Id
    hsRecFieldId HsRecField GhcTc (Located (Pat GhcTc))
    f1) Id -> Id -> Bool
    forall a. Eq a => a -> a -> Bool
    == GenLocated SrcSpan Id -> Id
    forall l e. GenLocated l e -> e
    unLoc (HsRecField GhcTc (Located (Pat GhcTc)) -> GenLocated SrcSpan Id
    forall arg. HsRecField GhcTc arg -> GenLocated SrcSpan Id
    hsRecFieldId HsRecField GhcTc (Located (Pat GhcTc))
    f2))
             (HsRecFields GhcTc (Located (Pat GhcTc))
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    forall p arg. HsRecFields p arg -> [LHsRecField p arg]
    rec_flds HsRecFields GhcTc (Located (Pat GhcTc))
    HsRecFields GhcTc (LPat GhcTc)
    flds1) (HsRecFields GhcTc (Located (Pat GhcTc))
    -> [LHsRecField GhcTc (Located (Pat GhcTc))]
    forall p arg. HsRecFields p arg -> [LHsRecField p arg]
    rec_flds HsRecFields GhcTc (Located (Pat GhcTc))
    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]
    newSysLocalsDsNoLP [Scaled Type]
    arg_tys
                                       (PrefixCon [LPat GhcTc]
    ps) -> [(Type, Pat GhcTc)] -> DsM [Id]
    selectMatchVars ([Scaled Type] -> [Located (Pat GhcTc)] -> [(Type, Pat GhcTc)]
    forall {a} {l} {b}. [Scaled a] -> [GenLocated l b] -> [(Type, b)]
    zipMults [Scaled Type]
    arg_tys [Located (Pat GhcTc)]
    [LPat GhcTc]
    ps)
                                       (InfixCon LPat GhcTc
    p1 LPat GhcTc
    p2) -> [(Type, Pat GhcTc)] -> DsM [Id]
    selectMatchVars ([Scaled Type] -> [Located (Pat GhcTc)] -> [(Type, Pat GhcTc)]
    forall {a} {l} {b}. [Scaled a] -> [GenLocated l b] -> [(Type, b)]
    zipMults [Scaled Type]
    arg_tys [Located (Pat GhcTc)
    LPat GhcTc
    p1, Located (Pat GhcTc)
    LPat GhcTc
    p2])
      where
        zipMults :: [Scaled a] -> [GenLocated l b] -> [(Type, b)]
    zipMults = String
    -> (Scaled a -> GenLocated l b -> (Type, b))
    -> [Scaled a]
    -> [GenLocated l b]
    -> [(Type, b)]
    forall a b c. String -> (a -> b -> c) -> [a] -> [b] -> [c]
    zipWithEqual String
    "selectConMatchVar" (\Scaled a
    a GenLocated l b
    b -> (Scaled a -> Type
    forall a. Scaled a -> Type
    scaledMult Scaled a
    a, GenLocated l b -> b
    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 [LPat GhcTc]
    ps)   = (Located (Pat GhcTc) -> Pat GhcTc)
    -> [Located (Pat GhcTc)] -> [Pat GhcTc]
    forall a b. (a -> b) -> [a] -> [b]
    map Located (Pat GhcTc) -> Pat GhcTc
    forall l e. GenLocated l e -> e
    unLoc [Located (Pat GhcTc)]
    [LPat GhcTc]
    ps
    conArgPats [Scaled Type]
    _arg_tys (InfixCon LPat GhcTc
    p1 LPat GhcTc
    p2) = [Located (Pat GhcTc) -> Pat GhcTc
    forall l e. GenLocated l e -> e
    unLoc Located (Pat GhcTc)
    LPat GhcTc
    p1, Located (Pat GhcTc) -> Pat GhcTc
    forall l e. GenLocated l e -> e
    unLoc Located (Pat GhcTc)
    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 }))
      | [LHsRecField GhcTc (Located (Pat GhcTc))] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [LHsRecField GhcTc (Located (Pat GhcTc))]
    [LHsRecField GhcTc (LPat GhcTc)]
    rpats = (Type -> Pat GhcTc) -> [Type] -> [Pat GhcTc]
    forall a b. (a -> b) -> [a] -> [b]
    map Type -> Pat GhcTc
    forall p. XWildPat p -> Pat p
    WildPat ((Scaled Type -> Type) -> [Scaled Type] -> [Type]
    forall a b. (a -> b) -> [a] -> [b]
    map Scaled Type -> Type
    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  = (LHsRecField GhcTc (Located (Pat GhcTc)) -> Pat GhcTc)
    -> [LHsRecField GhcTc (Located (Pat GhcTc))] -> [Pat GhcTc]
    forall a b. (a -> b) -> [a] -> [b]
    map (Located (Pat GhcTc) -> Pat GhcTc
    forall l e. GenLocated l e -> e
    unLoc (Located (Pat GhcTc) -> Pat GhcTc)
    -> (LHsRecField GhcTc (Located (Pat GhcTc)) -> Located (Pat GhcTc))
    -> LHsRecField GhcTc (Located (Pat GhcTc))
    -> Pat GhcTc
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . HsRecField GhcTc (Located (Pat GhcTc)) -> Located (Pat GhcTc)
    forall id arg. HsRecField' id arg -> arg
    hsRecFieldArg (HsRecField GhcTc (Located (Pat GhcTc)) -> Located (Pat GhcTc))
    -> (LHsRecField GhcTc (Located (Pat GhcTc))
        -> HsRecField GhcTc (Located (Pat GhcTc)))
    -> LHsRecField GhcTc (Located (Pat GhcTc))
    -> Located (Pat GhcTc)
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . LHsRecField GhcTc (Located (Pat GhcTc))
    -> HsRecField GhcTc (Located (Pat GhcTc))
    forall l e. GenLocated l e -> e
    unLoc) [LHsRecField GhcTc (Located (Pat GhcTc))]
    [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.

    -}