HsUtils.hs

{-
(c) The University of Glasgow, 1992-2006


Here we collect a variety of helper functions that construct or
analyse HsSyn.  All these functions deal with generic HsSyn; functions
which deal with the instantiated versions are located elsewhere:

   Parameterised by     Module
   ----------------     -------------
   RdrName              parser/RdrHsSyn
   Name                 rename/RnHsSyn
   Id                   typecheck/TcHsSyn
-}

{-# LANGUAGE CPP #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleContexts #-}

module HsUtils(
  -- Terms
  mkHsPar, mkHsApp, mkHsConApp, mkSimpleHsAlt,
  mkSimpleMatch, unguardedGRHSs, unguardedRHS,
  mkMatchGroup, mkMatchGroupName, mkMatch, mkHsLam, mkHsIf,
  mkHsWrap, mkLHsWrap, mkHsWrapCo, mkHsWrapCoR, mkLHsWrapCo,
  mkHsDictLet, mkHsLams,
  mkHsOpApp, mkHsDo, mkHsComp, mkHsWrapPat, mkHsWrapPatCo,
  mkLHsPar, mkHsCmdCast,

  nlHsTyApp, nlHsTyApps, nlHsVar, nlHsLit, nlHsApp, nlHsApps, nlHsIntLit, nlHsVarApps,
  nlHsDo, nlHsOpApp, nlHsLam, nlHsPar, nlHsIf, nlHsCase, nlList,
  mkLHsTupleExpr, mkLHsVarTuple, missingTupArg,
  toLHsSigWcType,

  -- * Constructing general big tuples
  -- $big_tuples
  mkChunkified, chunkify,

  -- Bindings
  mkFunBind, mkVarBind, mkHsVarBind, mk_easy_FunBind, mkTopFunBind,
  mkPatSynBind,
  isInfixFunBind,

  -- Literals
  mkHsIntegral, mkHsFractional, mkHsIsString, mkHsString, mkHsStringPrimLit,

  -- Patterns
  mkNPat, mkNPlusKPat, nlVarPat, nlLitPat, nlConVarPat, nlConVarPatName, nlConPat,
  nlConPatName, nlInfixConPat, nlNullaryConPat, nlWildConPat, nlWildPat,
  nlWildPatName, nlWildPatId, nlTuplePat, mkParPat,
  mkBigLHsVarTup, mkBigLHsTup, mkBigLHsVarPatTup, mkBigLHsPatTup,

  -- Types
  mkHsAppTy, userHsTyVarBndrs,
  mkLHsSigType, mkLHsSigWcType, mkClassOpSigs,
  nlHsAppTy, nlHsTyVar, nlHsFunTy, nlHsTyConApp,

  -- Stmts
  mkTransformStmt, mkTransformByStmt, mkBodyStmt, mkBindStmt, mkLastStmt,
  emptyTransStmt, mkGroupUsingStmt, mkGroupByUsingStmt,
  emptyRecStmt, emptyRecStmtName, emptyRecStmtId, mkRecStmt,

  -- Template Haskell
  mkHsSpliceTy, mkHsSpliceE, mkHsSpliceTE, mkUntypedSplice,
  mkHsQuasiQuote, unqualQuasiQuote,

  -- Flags
  noRebindableInfo,

  -- Collecting binders
  collectLocalBinders, collectHsValBinders, collectHsBindListBinders,
  collectHsIdBinders,
  collectHsBindsBinders, collectHsBindBinders, collectMethodBinders,
  collectPatBinders, collectPatsBinders,
  collectLStmtsBinders, collectStmtsBinders,
  collectLStmtBinders, collectStmtBinders,

  hsLTyClDeclBinders, hsTyClForeignBinders, hsPatSynBinders,
  hsForeignDeclsBinders, hsGroupBinders, hsDataFamInstBinders,

  -- Collecting implicit binders
  lStmtsImplicits, hsValBindsImplicits, lPatImplicits
  ) where

#include "HsVersions.h"

import HsDecls
import HsBinds
import HsExpr
import HsPat
import HsTypes
import HsLit
import PlaceHolder

import TcType( tcSplitForAllTys, tcSplitPhiTy )
import TcEvidence
import RdrName
import Var
import Type( isPredTy )
import Kind( isKind )
import TypeRep
import DataCon
import Name
import NameSet
import BasicTypes
import SrcLoc
import FastString
import Util
import Bag
import Outputable
import Constants

import Data.Either
import Data.Function
import Data.List

#if __GLASGOW_HASKELL__ < 709
import Data.Foldable ( foldMap )
import Data.Monoid ( mempty, mappend )
#endif

{-
************************************************************************
*                                                                      *
        Some useful helpers for constructing syntax
*                                                                      *
************************************************************************

These functions attempt to construct a not-completely-useless SrcSpan
from their components, compared with the nl* functions below which
just attach noSrcSpan to everything.
-}

mkHsPar :: LHsExpr id -> LHsExpr id
mkHsPar e = L (getLoc e) (HsPar e)

mkSimpleMatch :: [LPat id] -> Located (body id) -> LMatch id (Located (body id))
mkSimpleMatch pats rhs
  = L loc $
    Match NonFunBindMatch pats Nothing (unguardedGRHSs rhs)
  where
    loc = case pats of
                []      -> getLoc rhs
                (pat:_) -> combineSrcSpans (getLoc pat) (getLoc rhs)

unguardedGRHSs :: Located (body id) -> GRHSs id (Located (body id))
unguardedGRHSs rhs@(L loc _)
  = GRHSs (unguardedRHS loc rhs) (noLoc emptyLocalBinds)

unguardedRHS :: SrcSpan -> Located (body id) -> [LGRHS id (Located (body id))]
unguardedRHS loc rhs = [L loc (GRHS [] rhs)]

mkMatchGroup :: Origin -> [LMatch RdrName (Located (body RdrName))]
             -> MatchGroup RdrName (Located (body RdrName))
mkMatchGroup origin matches = MG { mg_alts = mkLocatedList matches
                                 , mg_arg_tys = []
                                 , mg_res_ty = placeHolderType
                                 , mg_origin = origin }

mkLocatedList ::  [Located a] -> Located [Located a]
mkLocatedList [] = noLoc []
mkLocatedList ms = L (combineLocs (head ms) (last ms)) ms

mkMatchGroupName :: Origin -> [LMatch Name (Located (body Name))]
             -> MatchGroup Name (Located (body Name))
mkMatchGroupName origin matches = MG { mg_alts = mkLocatedList matches
                                     , mg_arg_tys = []
                                     , mg_res_ty = placeHolderType
                                     , mg_origin = origin }

mkHsAppTy :: LHsType name -> LHsType name -> LHsType name
mkHsAppTy t1 t2 = addCLoc t1 t2 (HsAppTy t1 t2)

mkHsApp :: LHsExpr name -> LHsExpr name -> LHsExpr name
mkHsApp e1 e2 = addCLoc e1 e2 (HsApp e1 e2)

mkHsLam :: [LPat RdrName] -> LHsExpr RdrName -> LHsExpr RdrName
mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
        where
          matches = mkMatchGroup Generated [mkSimpleMatch pats body]

mkHsLams :: [TyVar] -> [EvVar] -> LHsExpr Id -> LHsExpr Id
mkHsLams tyvars dicts expr = mkLHsWrap (mkWpTyLams tyvars
                                       <.> mkWpLams dicts) expr

mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
-- Used for constructing dictionary terms etc, so no locations
mkHsConApp data_con tys args
  = foldl mk_app (nlHsTyApp (dataConWrapId data_con) tys) args
  where
    mk_app f a = noLoc (HsApp f (noLoc a))

mkSimpleHsAlt :: LPat id -> (Located (body id)) -> LMatch id (Located (body id))
-- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
mkSimpleHsAlt pat expr
  = mkSimpleMatch [pat] expr

nlHsTyApp :: name -> [Type] -> LHsExpr name
nlHsTyApp fun_id tys = noLoc (HsWrap (mkWpTyApps tys) (HsVar (noLoc fun_id)))

nlHsTyApps :: name -> [Type] -> [LHsExpr name] -> LHsExpr name
nlHsTyApps fun_id tys xs = foldl nlHsApp (nlHsTyApp fun_id tys) xs

--------- Adding parens ---------
mkLHsPar :: LHsExpr name -> LHsExpr name
-- Wrap in parens if hsExprNeedsParens says it needs them
-- So   'f x'  becomes '(f x)', but '3' stays as '3'
mkLHsPar le@(L loc e) | hsExprNeedsParens e = L loc (HsPar le)
                      | otherwise           = le

mkParPat :: LPat name -> LPat name
mkParPat lp@(L loc p) | hsPatNeedsParens p = L loc (ParPat lp)
                      | otherwise          = lp


-------------------------------
-- These are the bits of syntax that contain rebindable names
-- See RnEnv.lookupSyntaxName

mkHsIntegral   :: String -> Integer -> PostTc RdrName Type -> HsOverLit RdrName
mkHsFractional :: FractionalLit -> PostTc RdrName Type -> HsOverLit RdrName
mkHsIsString :: String -> FastString -> PostTc RdrName Type -> HsOverLit RdrName
mkHsDo         :: HsStmtContext Name -> [ExprLStmt RdrName] -> HsExpr RdrName
mkHsComp       :: HsStmtContext Name -> [ExprLStmt RdrName] -> LHsExpr RdrName
               -> HsExpr RdrName

mkNPat      :: Located (HsOverLit id) -> Maybe (SyntaxExpr id) -> Pat id
mkNPlusKPat :: Located id -> Located (HsOverLit id) -> Pat id

mkLastStmt :: Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR))
mkBodyStmt :: Located (bodyR RdrName)
           -> StmtLR idL RdrName (Located (bodyR RdrName))
mkBindStmt :: LPat idL -> Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR))

emptyRecStmt     :: StmtLR idL  RdrName bodyR
emptyRecStmtName :: StmtLR Name Name    bodyR
emptyRecStmtId   :: StmtLR Id   Id      bodyR
mkRecStmt    :: [LStmtLR idL RdrName bodyR] -> StmtLR idL RdrName bodyR


mkHsIntegral src i  = OverLit (HsIntegral   src i) noRebindableInfo noSyntaxExpr
mkHsFractional   f  = OverLit (HsFractional     f) noRebindableInfo noSyntaxExpr
mkHsIsString src s  = OverLit (HsIsString   src s) noRebindableInfo noSyntaxExpr

noRebindableInfo :: PlaceHolder
noRebindableInfo = PlaceHolder -- Just another placeholder;

mkHsDo ctxt stmts = HsDo ctxt (mkLocatedList stmts) placeHolderType
mkHsComp ctxt stmts expr = mkHsDo ctxt (stmts ++ [last_stmt])
  where
    last_stmt = L (getLoc expr) $ mkLastStmt expr

mkHsIf :: LHsExpr id -> LHsExpr id -> LHsExpr id -> HsExpr id
mkHsIf c a b = HsIf (Just noSyntaxExpr) c a b

mkNPat lit neg     = NPat lit neg noSyntaxExpr
mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr

mkTransformStmt    :: [ExprLStmt idL] -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkTransformByStmt  :: [ExprLStmt idL] -> LHsExpr idR -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkGroupUsingStmt   :: [ExprLStmt idL]                -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkGroupByUsingStmt :: [ExprLStmt idL] -> LHsExpr idR -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)

emptyTransStmt :: StmtLR idL idR (LHsExpr idR)
emptyTransStmt = TransStmt { trS_form = panic "emptyTransStmt: form"
                           , trS_stmts = [], trS_bndrs = []
                           , trS_by = Nothing, trS_using = noLoc noSyntaxExpr
                           , trS_ret = noSyntaxExpr, trS_bind = noSyntaxExpr
                           , trS_fmap = noSyntaxExpr }
mkTransformStmt    ss u   = emptyTransStmt { trS_form = ThenForm,  trS_stmts = ss, trS_using = u }
mkTransformByStmt  ss u b = emptyTransStmt { trS_form = ThenForm,  trS_stmts = ss, trS_using = u, trS_by = Just b }
mkGroupUsingStmt   ss u   = emptyTransStmt { trS_form = GroupForm, trS_stmts = ss, trS_using = u }
mkGroupByUsingStmt ss b u = emptyTransStmt { trS_form = GroupForm, trS_stmts = ss, trS_using = u, trS_by = Just b }

mkLastStmt body     = LastStmt body False noSyntaxExpr
mkBodyStmt body     = BodyStmt body noSyntaxExpr noSyntaxExpr placeHolderType
mkBindStmt pat body = BindStmt pat body noSyntaxExpr noSyntaxExpr


emptyRecStmt' :: forall idL idR body.
                       PostTc idR Type -> StmtLR idL idR body
emptyRecStmt' tyVal =
   RecStmt
     { recS_stmts = [], recS_later_ids = []
     , recS_rec_ids = []
     , recS_ret_fn = noSyntaxExpr
     , recS_mfix_fn = noSyntaxExpr
     , recS_bind_fn = noSyntaxExpr, recS_later_rets = []
     , recS_rec_rets = [], recS_ret_ty = tyVal }

emptyRecStmt     = emptyRecStmt' placeHolderType
emptyRecStmtName = emptyRecStmt' placeHolderType
emptyRecStmtId   = emptyRecStmt' placeHolderTypeTc
mkRecStmt stmts  = emptyRecStmt { recS_stmts = stmts }

-------------------------------
--- A useful function for building @OpApps@.  The operator is always a
-- variable, and we don't know the fixity yet.
mkHsOpApp :: LHsExpr id -> id -> LHsExpr id -> HsExpr id
mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar (noLoc op)))
                           (error "mkOpApp:fixity") e2

unqualSplice :: RdrName
unqualSplice = mkRdrUnqual (mkVarOccFS (fsLit "splice"))

mkUntypedSplice :: LHsExpr RdrName -> HsSplice RdrName
mkUntypedSplice e = HsUntypedSplice unqualSplice e

mkHsSpliceE :: LHsExpr RdrName -> HsExpr RdrName
mkHsSpliceE e = HsSpliceE (mkUntypedSplice e)

mkHsSpliceTE :: LHsExpr RdrName -> HsExpr RdrName
mkHsSpliceTE e = HsSpliceE (HsTypedSplice unqualSplice e)

mkHsSpliceTy :: LHsExpr RdrName -> HsType RdrName
mkHsSpliceTy e = HsSpliceTy (HsUntypedSplice unqualSplice e) placeHolderKind

mkHsQuasiQuote :: RdrName -> SrcSpan -> FastString -> HsSplice RdrName
mkHsQuasiQuote quoter span quote = HsQuasiQuote unqualSplice quoter span quote

unqualQuasiQuote :: RdrName
unqualQuasiQuote = mkRdrUnqual (mkVarOccFS (fsLit "quasiquote"))
                -- A name (uniquified later) to
                -- identify the quasi-quote

mkHsString :: String -> HsLit
mkHsString s = HsString s (mkFastString s)

mkHsStringPrimLit :: FastString -> HsLit
mkHsStringPrimLit fs
  = HsStringPrim (unpackFS fs) (fastStringToByteString fs)

-------------
userHsTyVarBndrs :: SrcSpan -> [name] -> [Located (HsTyVarBndr name)]
-- Caller sets location
userHsTyVarBndrs loc bndrs = [ L loc (UserTyVar (L loc v)) | v <- bndrs ]

{-
************************************************************************
*                                                                      *
        Constructing syntax with no location info
*                                                                      *
************************************************************************
-}

nlHsVar :: id -> LHsExpr id
nlHsVar n = noLoc (HsVar (noLoc n))

nlHsLit :: HsLit -> LHsExpr id
nlHsLit n = noLoc (HsLit n)

nlVarPat :: id -> LPat id
nlVarPat n = noLoc (VarPat (noLoc n))

nlLitPat :: HsLit -> LPat id
nlLitPat l = noLoc (LitPat l)

nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
nlHsApp f x = noLoc (HsApp f x)

nlHsIntLit :: Integer -> LHsExpr id
nlHsIntLit n = noLoc (HsLit (HsInt (show n) n))

nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs

nlHsVarApps :: id -> [id] -> LHsExpr id
nlHsVarApps f xs = noLoc (foldl mk (HsVar (noLoc f)) (map (HsVar . noLoc) xs))
                 where
                   mk f a = HsApp (noLoc f) (noLoc a)

nlConVarPat :: RdrName -> [RdrName] -> LPat RdrName
nlConVarPat con vars = nlConPat con (map nlVarPat vars)

nlConVarPatName :: Name -> [Name] -> LPat Name
nlConVarPatName con vars = nlConPatName con (map nlVarPat vars)

nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))

nlConPat :: RdrName -> [LPat RdrName] -> LPat RdrName
nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))

nlConPatName :: Name -> [LPat Name] -> LPat Name
nlConPatName con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))

nlNullaryConPat :: id -> LPat id
nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))

nlWildConPat :: DataCon -> LPat RdrName
nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
                         (PrefixCon (nOfThem (dataConSourceArity con)
                                             nlWildPat)))

nlWildPat :: LPat RdrName
nlWildPat  = noLoc (WildPat placeHolderType )  -- Pre-typechecking

nlWildPatName :: LPat Name
nlWildPatName  = noLoc (WildPat placeHolderType )  -- Pre-typechecking

nlWildPatId :: LPat Id
nlWildPatId  = noLoc (WildPat placeHolderTypeTc )  -- Post-typechecking

nlHsDo :: HsStmtContext Name -> [LStmt RdrName (LHsExpr RdrName)]
       -> LHsExpr RdrName
nlHsDo ctxt stmts = noLoc (mkHsDo ctxt stmts)

nlHsOpApp :: LHsExpr id -> id -> LHsExpr id -> LHsExpr id
nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)

nlHsLam  :: LMatch RdrName (LHsExpr RdrName) -> LHsExpr RdrName
nlHsPar  :: LHsExpr id -> LHsExpr id
nlHsIf   :: LHsExpr id -> LHsExpr id -> LHsExpr id -> LHsExpr id
nlHsCase :: LHsExpr RdrName -> [LMatch RdrName (LHsExpr RdrName)]
         -> LHsExpr RdrName
nlList   :: [LHsExpr RdrName] -> LHsExpr RdrName

nlHsLam match          = noLoc (HsLam (mkMatchGroup Generated [match]))
nlHsPar e              = noLoc (HsPar e)
nlHsIf cond true false = noLoc (mkHsIf cond true false)
nlHsCase expr matches  = noLoc (HsCase expr (mkMatchGroup Generated matches))
nlList exprs           = noLoc (ExplicitList placeHolderType Nothing exprs)

nlHsAppTy :: LHsType name -> LHsType name -> LHsType name
nlHsTyVar :: name                         -> LHsType name
nlHsFunTy :: LHsType name -> LHsType name -> LHsType name

nlHsAppTy f t           = noLoc (HsAppTy f t)
nlHsTyVar x             = noLoc (HsTyVar (noLoc x))
nlHsFunTy a b           = noLoc (HsFunTy a b)

nlHsTyConApp :: name -> [LHsType name] -> LHsType name
nlHsTyConApp tycon tys  = foldl nlHsAppTy (nlHsTyVar tycon) tys

{-
Tuples.  All these functions are *pre-typechecker* because they lack
types on the tuple.
-}

mkLHsTupleExpr :: [LHsExpr a] -> LHsExpr a
-- Makes a pre-typechecker boxed tuple, deals with 1 case
mkLHsTupleExpr [e] = e
mkLHsTupleExpr es  = noLoc $ ExplicitTuple (map (noLoc . Present) es) Boxed

mkLHsVarTuple :: [a] -> LHsExpr a
mkLHsVarTuple ids  = mkLHsTupleExpr (map nlHsVar ids)

nlTuplePat :: [LPat id] -> Boxity -> LPat id
nlTuplePat pats box = noLoc (TuplePat pats box [])

missingTupArg :: HsTupArg RdrName
missingTupArg = Missing placeHolderType

mkLHsPatTup :: [LPat id] -> LPat id
mkLHsPatTup []     = noLoc $ TuplePat [] Boxed []
mkLHsPatTup [lpat] = lpat
mkLHsPatTup lpats  = L (getLoc (head lpats)) $ TuplePat lpats Boxed []

-- The Big equivalents for the source tuple expressions
mkBigLHsVarTup :: [id] -> LHsExpr id
mkBigLHsVarTup ids = mkBigLHsTup (map nlHsVar ids)

mkBigLHsTup :: [LHsExpr id] -> LHsExpr id
mkBigLHsTup = mkChunkified mkLHsTupleExpr

-- The Big equivalents for the source tuple patterns
mkBigLHsVarPatTup :: [id] -> LPat id
mkBigLHsVarPatTup bs = mkBigLHsPatTup (map nlVarPat bs)

mkBigLHsPatTup :: [LPat id] -> LPat id
mkBigLHsPatTup = mkChunkified mkLHsPatTup

-- $big_tuples
-- #big_tuples#
--
-- GHCs built in tuples can only go up to 'mAX_TUPLE_SIZE' in arity, but
-- we might concievably want to build such a massive tuple as part of the
-- output of a desugaring stage (notably that for list comprehensions).
--
-- We call tuples above this size \"big tuples\", and emulate them by
-- creating and pattern matching on >nested< tuples that are expressible
-- by GHC.
--
-- Nesting policy: it's better to have a 2-tuple of 10-tuples (3 objects)
-- than a 10-tuple of 2-tuples (11 objects), so we want the leaves of any
-- construction to be big.
--
-- If you just use the 'mkBigCoreTup', 'mkBigCoreVarTupTy', 'mkTupleSelector'
-- and 'mkTupleCase' functions to do all your work with tuples you should be
-- fine, and not have to worry about the arity limitation at all.

-- | Lifts a \"small\" constructor into a \"big\" constructor by recursive decompositon
mkChunkified :: ([a] -> a)      -- ^ \"Small\" constructor function, of maximum input arity 'mAX_TUPLE_SIZE'
             -> [a]             -- ^ Possible \"big\" list of things to construct from
             -> a               -- ^ Constructed thing made possible by recursive decomposition
mkChunkified small_tuple as = mk_big_tuple (chunkify as)
  where
        -- Each sub-list is short enough to fit in a tuple
    mk_big_tuple [as] = small_tuple as
    mk_big_tuple as_s = mk_big_tuple (chunkify (map small_tuple as_s))

chunkify :: [a] -> [[a]]
-- ^ Split a list into lists that are small enough to have a corresponding
-- tuple arity. The sub-lists of the result all have length <= 'mAX_TUPLE_SIZE'
-- But there may be more than 'mAX_TUPLE_SIZE' sub-lists
chunkify xs
  | n_xs <= mAX_TUPLE_SIZE = [xs]
  | otherwise              = split xs
  where
    n_xs     = length xs
    split [] = []
    split xs = take mAX_TUPLE_SIZE xs : split (drop mAX_TUPLE_SIZE xs)

{-
************************************************************************
*                                                                      *
        LHsSigType and LHsSigWcType
*                                                                      *
********************************************************************* -}

mkLHsSigType :: LHsType RdrName -> LHsSigType RdrName
mkLHsSigType ty = mkHsImplicitBndrs ty

mkLHsSigWcType :: LHsType RdrName -> LHsSigWcType RdrName
mkLHsSigWcType ty = mkHsImplicitBndrs (mkHsWildCardBndrs ty)

mkClassOpSigs :: [LSig RdrName] -> [LSig RdrName]
-- Convert TypeSig to ClassOpSig
-- The former is what is parsed, but the latter is
-- what we need in class/instance declarations
mkClassOpSigs sigs
  = map fiddle sigs
  where
    fiddle (L loc (TypeSig nms ty)) = L loc (ClassOpSig False nms (dropWildCards ty))
    fiddle sig                      = sig

toLHsSigWcType :: Type -> LHsSigWcType RdrName
-- ^ Converting a Type to an HsType RdrName
-- This is needed to implement GeneralizedNewtypeDeriving.
--
-- Note that we use 'getRdrName' extensively, which
-- generates Exact RdrNames rather than strings.
toLHsSigWcType ty
  = mkLHsSigWcType (go ty)
  where
    go :: Type -> LHsType RdrName
    go ty@(ForAllTy {})
      | (tvs, tau) <- tcSplitForAllTys ty
      = noLoc (HsForAllTy { hst_bndrs = map go_tv tvs
                          , hst_body = go tau })
    go ty@(FunTy arg _)
      | isPredTy arg
      , (theta, tau) <- tcSplitPhiTy ty
      = noLoc (HsQualTy { hst_ctxt = noLoc (map go theta)
                        , hst_body = go tau })
    go (FunTy arg res)      = nlHsFunTy (go arg) (go res)
    go (TyVarTy tv)         = nlHsTyVar (getRdrName tv)
    go (AppTy t1 t2)        = nlHsAppTy (go t1) (go t2)
    go (LitTy (NumTyLit n)) = noLoc $ HsTyLit (HsNumTy "" n)
    go (LitTy (StrTyLit s)) = noLoc $ HsTyLit (HsStrTy "" s)
    go (TyConApp tc args)   = nlHsTyConApp (getRdrName tc) (map go args')
       where
         args' = filterOut isKind args
         -- Source-language types have _implicit_ kind arguments,
         -- so we must remove them here (Trac #8563)

    go_tv :: TyVar -> LHsTyVarBndr RdrName
    go_tv tv = noLoc $ KindedTyVar (noLoc (getRdrName tv))
                                   (go (tyVarKind tv))


{- *********************************************************************
*                                                                      *
    --------- HsWrappers: type args, dict args, casts ---------
*                                                                      *
********************************************************************* -}

mkLHsWrap :: HsWrapper -> LHsExpr id -> LHsExpr id
mkLHsWrap co_fn (L loc e) = L loc (mkHsWrap co_fn e)

mkHsWrap :: HsWrapper -> HsExpr id -> HsExpr id
mkHsWrap co_fn e | isIdHsWrapper co_fn = e
                 | otherwise           = HsWrap co_fn e

mkHsWrapCo :: TcCoercionN   -- A Nominal coercion  a ~N b
           -> HsExpr id -> HsExpr id
mkHsWrapCo co e = mkHsWrap (mkWpCastN co) e

mkHsWrapCoR :: TcCoercionR   -- A Representational coercion  a ~R b
            -> HsExpr id -> HsExpr id
mkHsWrapCoR co e = mkHsWrap (mkWpCastR co) e

mkLHsWrapCo :: TcCoercionN -> LHsExpr id -> LHsExpr id
mkLHsWrapCo co (L loc e) = L loc (mkHsWrapCo co e)

mkHsCmdCast :: TcCoercion -> HsCmd id -> HsCmd id
mkHsCmdCast co cmd | isTcReflCo co = cmd
                   | otherwise     = HsCmdCast co cmd

mkHsWrapPat :: HsWrapper -> Pat id -> Type -> Pat id
mkHsWrapPat co_fn p ty | isIdHsWrapper co_fn = p
                       | otherwise           = CoPat co_fn p ty

mkHsWrapPatCo :: TcCoercionN -> Pat id -> Type -> Pat id
mkHsWrapPatCo co pat ty | isTcReflCo co = pat
                        | otherwise     = CoPat (mkWpCastN co) pat ty

mkHsDictLet :: TcEvBinds -> LHsExpr Id -> LHsExpr Id
mkHsDictLet ev_binds expr = mkLHsWrap (mkWpLet ev_binds) expr

{-
l
************************************************************************
*                                                                      *
                Bindings; with a location at the top
*                                                                      *
************************************************************************
-}

mkFunBind :: Located RdrName -> [LMatch RdrName (LHsExpr RdrName)]
          -> HsBind RdrName
-- Not infix, with place holders for coercion and free vars
mkFunBind fn ms = FunBind { fun_id = fn
                          , fun_matches = mkMatchGroup Generated ms
                          , fun_co_fn = idHsWrapper
                          , bind_fvs = placeHolderNames
                          , fun_tick = [] }

mkTopFunBind :: Origin -> Located Name -> [LMatch Name (LHsExpr Name)]
             -> HsBind Name
-- In Name-land, with empty bind_fvs
mkTopFunBind origin fn ms = FunBind { fun_id = fn
                                    , fun_matches = mkMatchGroupName origin ms
                                    , fun_co_fn = idHsWrapper
                                    , bind_fvs = emptyNameSet -- NB: closed
                                                              --     binding
                                    , fun_tick = [] }

mkHsVarBind :: SrcSpan -> RdrName -> LHsExpr RdrName -> LHsBind RdrName
mkHsVarBind loc var rhs = mk_easy_FunBind loc var [] rhs

mkVarBind :: id -> LHsExpr id -> LHsBind id
mkVarBind var rhs = L (getLoc rhs) $
                    VarBind { var_id = var, var_rhs = rhs, var_inline = False }

mkPatSynBind :: Located RdrName -> HsPatSynDetails (Located RdrName)
             -> LPat RdrName -> HsPatSynDir RdrName -> HsBind RdrName
mkPatSynBind name details lpat dir = PatSynBind psb
  where
    psb = PSB{ psb_id = name
             , psb_args = details
             , psb_def = lpat
             , psb_dir = dir
             , psb_fvs = placeHolderNames }

-- |If any of the matches in the 'FunBind' are infix, the 'FunBind' is
-- considered infix.
isInfixFunBind :: HsBindLR id1 id2 -> Bool
isInfixFunBind (FunBind _ (MG matches _ _ _) _ _ _)
  = any (isInfixMatch . unLoc) (unLoc matches)
isInfixFunBind _ = False


------------
mk_easy_FunBind :: SrcSpan -> RdrName -> [LPat RdrName]
                -> LHsExpr RdrName -> LHsBind RdrName
mk_easy_FunBind loc fun pats expr
  = L loc $ mkFunBind (L loc fun) [mkMatch pats expr (noLoc emptyLocalBinds)]

------------
mkMatch :: [LPat id] -> LHsExpr id -> Located (HsLocalBinds id)
        -> LMatch id (LHsExpr id)
mkMatch pats expr lbinds
  = noLoc (Match NonFunBindMatch (map paren pats) Nothing
                 (GRHSs (unguardedRHS noSrcSpan expr) lbinds))
  where
    paren lp@(L l p) | hsPatNeedsParens p = L l (ParPat lp)
                     | otherwise          = lp

{-
************************************************************************
*                                                                      *
        Collecting binders
*                                                                      *
************************************************************************

Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.

...
where
  (x, y) = ...
  f i j  = ...
  [a, b] = ...

it should return [x, y, f, a, b] (remember, order important).

Note [Collect binders only after renaming]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
These functions should only be used on HsSyn *after* the renamer,
to return a [Name] or [Id].  Before renaming the record punning
and wild-card mechanism makes it hard to know what is bound.
So these functions should not be applied to (HsSyn RdrName)
-}

----------------- Bindings --------------------------
collectLocalBinders :: HsLocalBindsLR idL idR -> [idL]
collectLocalBinders (HsValBinds binds) = collectHsIdBinders binds
                                         -- No pattern synonyms here
collectLocalBinders (HsIPBinds _)      = []
collectLocalBinders EmptyLocalBinds    = []

collectHsIdBinders, collectHsValBinders :: HsValBindsLR idL idR -> [idL]
-- Collect Id binders only, or Ids + pattern synonmys, respectively
collectHsIdBinders  = collect_hs_val_binders True
collectHsValBinders = collect_hs_val_binders False

collectHsBindBinders :: HsBindLR idL idR -> [idL]
-- Collect both Ids and pattern-synonym binders
collectHsBindBinders b = collect_bind False b []

collectHsBindsBinders :: LHsBindsLR idL idR -> [idL]
collectHsBindsBinders binds = collect_binds False binds []

collectHsBindListBinders :: [LHsBindLR idL idR] -> [idL]
-- Same as collectHsBindsBinders, but works over a list of bindings
collectHsBindListBinders = foldr (collect_bind False . unLoc) []

collect_hs_val_binders :: Bool -> HsValBindsLR idL idR -> [idL]
collect_hs_val_binders ps (ValBindsIn  binds _) = collect_binds     ps binds []
collect_hs_val_binders ps (ValBindsOut binds _) = collect_out_binds ps binds

collect_out_binds :: Bool -> [(RecFlag, LHsBinds id)] -> [id]
collect_out_binds ps = foldr (collect_binds ps . snd) []

collect_binds :: Bool -> LHsBindsLR idL idR -> [idL] -> [idL]
-- Collect Ids, or Ids + patter synonyms, depending on boolean flag
collect_binds ps binds acc = foldrBag (collect_bind ps . unLoc) acc binds

collect_bind :: Bool -> HsBindLR idL idR -> [idL] -> [idL]
collect_bind _ (PatBind { pat_lhs = p })           acc = collect_lpat p acc
collect_bind _ (FunBind { fun_id = L _ f })        acc = f : acc
collect_bind _ (VarBind { var_id = f })            acc = f : acc
collect_bind _ (AbsBinds { abs_exports = dbinds }) acc = map abe_poly dbinds ++ acc
        -- I don't think we want the binders from the abe_binds
        -- The only time we collect binders from a typechecked
        -- binding (hence see AbsBinds) is in zonking in TcHsSyn
collect_bind omitPatSyn (PatSynBind (PSB { psb_id = L _ ps })) acc =
    if omitPatSyn then acc else ps : acc

collectMethodBinders :: LHsBindsLR RdrName idR -> [Located RdrName]
-- Used exclusively for the bindings of an instance decl which are all FunBinds
collectMethodBinders binds = foldrBag (get . unLoc) [] binds
  where
    get (FunBind { fun_id = f }) fs = f : fs
    get _                        fs = fs
       -- Someone else complains about non-FunBinds

----------------- Statements --------------------------
collectLStmtsBinders :: [LStmtLR idL idR body] -> [idL]
collectLStmtsBinders = concatMap collectLStmtBinders

collectStmtsBinders :: [StmtLR idL idR body] -> [idL]
collectStmtsBinders = concatMap collectStmtBinders

collectLStmtBinders :: LStmtLR idL idR body -> [idL]
collectLStmtBinders = collectStmtBinders . unLoc

collectStmtBinders :: StmtLR idL idR body -> [idL]
  -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
collectStmtBinders (BindStmt pat _ _ _)  = collectPatBinders pat
collectStmtBinders (LetStmt (L _ binds)) = collectLocalBinders binds
collectStmtBinders (BodyStmt {})         = []
collectStmtBinders (LastStmt {})         = []
collectStmtBinders (ParStmt xs _ _)   = collectLStmtsBinders
                                      $ [s | ParStmtBlock ss _ _ <- xs, s <- ss]
collectStmtBinders (TransStmt { trS_stmts = stmts }) = collectLStmtsBinders stmts
collectStmtBinders (RecStmt { recS_stmts = ss })     = collectLStmtsBinders ss
collectStmtBinders ApplicativeStmt{} = []


----------------- Patterns --------------------------
collectPatBinders :: LPat a -> [a]
collectPatBinders pat = collect_lpat pat []

collectPatsBinders :: [LPat a] -> [a]
collectPatsBinders pats = foldr collect_lpat [] pats

-------------
collect_lpat :: LPat name -> [name] -> [name]
collect_lpat (L _ pat) bndrs
  = go pat
  where
    go (VarPat (L _ var))         = var : bndrs
    go (WildPat _)                = bndrs
    go (LazyPat pat)              = collect_lpat pat bndrs
    go (BangPat pat)              = collect_lpat pat bndrs
    go (AsPat (L _ a) pat)        = a : collect_lpat pat bndrs
    go (ViewPat _ pat _)          = collect_lpat pat bndrs
    go (ParPat  pat)              = collect_lpat pat bndrs

    go (ListPat pats _ _)         = foldr collect_lpat bndrs pats
    go (PArrPat pats _)           = foldr collect_lpat bndrs pats
    go (TuplePat pats _ _)        = foldr collect_lpat bndrs pats

    go (ConPatIn _ ps)            = foldr collect_lpat bndrs (hsConPatArgs ps)
    go (ConPatOut {pat_args=ps})  = foldr collect_lpat bndrs (hsConPatArgs ps)
        -- See Note [Dictionary binders in ConPatOut]
    go (LitPat _)                 = bndrs
    go (NPat _ _ _)               = bndrs
    go (NPlusKPat (L _ n) _ _ _)  = n : bndrs

    go (SigPatIn pat _)           = collect_lpat pat bndrs
    go (SigPatOut pat _)          = collect_lpat pat bndrs
    go (SplicePat _)              = bndrs
    go (CoPat _ pat _)            = go pat

{-
Note [Dictionary binders in ConPatOut] See also same Note in DsArrows
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Do *not* gather (a) dictionary and (b) dictionary bindings as binders
of a ConPatOut pattern.  For most calls it doesn't matter, because
it's pre-typechecker and there are no ConPatOuts.  But it does matter
more in the desugarer; for example, DsUtils.mkSelectorBinds uses
collectPatBinders.  In a lazy pattern, for example f ~(C x y) = ...,
we want to generate bindings for x,y but not for dictionaries bound by
C.  (The type checker ensures they would not be used.)

Desugaring of arrow case expressions needs these bindings (see DsArrows
and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
own pat-binder-collector:

Here's the problem.  Consider

data T a where
   C :: Num a => a -> Int -> T a

f ~(C (n+1) m) = (n,m)

Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
and *also* uses that dictionary to match the (n+1) pattern.  Yet, the
variables bound by the lazy pattern are n,m, *not* the dictionary d.
So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.
-}

hsGroupBinders :: HsGroup Name -> [Name]
hsGroupBinders (HsGroup { hs_valds = val_decls, hs_tyclds = tycl_decls,
                          hs_instds = inst_decls, hs_fords = foreign_decls })
  =  collectHsValBinders val_decls
  ++ hsTyClForeignBinders tycl_decls inst_decls foreign_decls

hsTyClForeignBinders :: [TyClGroup Name] -> [LInstDecl Name]
                     -> [LForeignDecl Name] -> [Name]
-- We need to look at instance declarations too,
-- because their associated types may bind data constructors
hsTyClForeignBinders tycl_decls inst_decls foreign_decls