{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE BlockArguments #-}
{-# OPTIONS_GHC -Wno-incomplete-record-updates #-}
{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-}
-- | Typecheck arrow notation
module GHC.Tc.Gen.Arrow ( tcProc ) where
import GHC.Prelude
import {-# SOURCE #-} GHC.Tc.Gen.Expr( tcCheckMonoExpr, tcInferRho, tcSyntaxOp
, tcCheckPolyExpr )
import GHC.Hs
import GHC.Tc.Errors.Types
import GHC.Tc.Gen.Match
import GHC.Tc.Gen.Head( tcCheckId )
import GHC.Tc.Utils.Concrete ( hasFixedRuntimeRep_syntactic )
import GHC.Tc.Utils.TcType
import GHC.Tc.Utils.TcMType
import GHC.Tc.Gen.Bind
import GHC.Tc.Gen.Pat
import GHC.Tc.Utils.Unify
import GHC.Tc.Utils.Monad
import GHC.Tc.Utils.Env
import GHC.Tc.Types.Origin
import GHC.Tc.Types.Evidence
import GHC.Core.Multiplicity
import GHC.Core.Coercion
import GHC.Types.Id( mkLocalId )
import GHC.Tc.Utils.Instantiate
import GHC.Builtin.Types
import GHC.Types.Var.Set
import GHC.Builtin.Types.Prim
import GHC.Types.Basic( Arity )
import GHC.Types.Error
import GHC.Types.SrcLoc
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Misc
import Control.Monad
{-
Note [Arrow overview]
~~~~~~~~~~~~~~~~~~~~~
Here's a summary of arrows and how they typecheck. First, here's
a cut-down syntax:
expr ::= ....
| proc pat cmd
cmd ::= cmd exp -- Arrow application
| \pat -> cmd -- Arrow abstraction
| (| exp cmd1 ... cmdn |) -- Arrow form, n>=0
| ... -- If, case in the usual way
cmd_type ::= carg_type --> type
carg_type ::= ()
| (type, carg_type)
Note that
* The 'exp' in an arrow form can mention only
"arrow-local" variables
* An "arrow-local" variable is bound by an enclosing
cmd binding form (eg arrow abstraction)
* A cmd_type is here written with a funny arrow "-->",
The bit on the left is a carg_type (command argument type)
which itself is a nested tuple, finishing with ()
* The arrow-tail operator (e1 -< e2) means
(| e1 <<< arr snd |) e2
************************************************************************
* *
Proc
* *
************************************************************************
-}
tcProc :: LPat GhcRn -> LHsCmdTop GhcRn -- proc pat -> expr
-> ExpRhoType -- Expected type of whole proc expression
-> TcM (LPat GhcTc, LHsCmdTop GhcTc, TcCoercion)
tcProc pat cmd@(L loc (HsCmdTop names _)) exp_ty
= do { exp_ty <- expTypeToType exp_ty -- no higher-rank stuff with arrows
; (co, (exp_ty1, res_ty)) <- matchExpectedAppTy exp_ty
; (co1, (arr_ty, arg_ty)) <- matchExpectedAppTy exp_ty1
-- start with the names as they are used to desugar the proc itself
-- See #17423
; names' <- setSrcSpanA loc $
mapM (tcSyntaxName ProcOrigin arr_ty) names
; let cmd_env = CmdEnv { cmd_arr = arr_ty }
; (pat', cmd') <- newArrowScope
$ tcCheckPat (ArrowMatchCtxt ProcExpr) pat (unrestricted arg_ty)
$ tcCmdTop cmd_env names' cmd (unitTy, res_ty)
; let res_co = co `mkTransCo` mkAppCo co1 (mkNomReflCo res_ty)
; return (pat', cmd', res_co) }
{-
************************************************************************
* *
Commands
* *
************************************************************************
-}
-- See Note [Arrow overview]
type CmdType = (CmdArgType, TcTauType) -- cmd_type
type CmdArgType = TcTauType -- carg_type, a nested tuple
data CmdEnv
= CmdEnv {
cmd_arr :: TcType -- ^ Arrow type constructor, of kind *->*->*
}
mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType
mkCmdArrTy env t1 t2 = mkAppTys (cmd_arr env) [t1, t2]
---------------------------------------
tcCmdTop :: CmdEnv
-> CmdSyntaxTable GhcTc -- ^ Type-checked Arrow class methods (arr, (>>>), ...)
-> LHsCmdTop GhcRn
-> CmdType
-> TcM (LHsCmdTop GhcTc)
tcCmdTop env names (L loc (HsCmdTop _names cmd)) cmd_ty@(cmd_stk, res_ty)
= setSrcSpanA loc $
do { cmd' <- tcCmd env cmd cmd_ty
; return (L loc $ HsCmdTop (CmdTopTc cmd_stk res_ty names) cmd') }
----------------------------------------
tcCmd :: CmdEnv -> LHsCmd GhcRn -> CmdType -> TcM (LHsCmd GhcTc)
-- The main recursive function
tcCmd env (L loc cmd) cmd_ty@(_, res_ty)
= setSrcSpan (locA loc) $ do
{ cmd' <- tc_cmd env cmd cmd_ty
; hasFixedRuntimeRep_syntactic (FRRArrow $ ArrowCmdResTy cmd) res_ty
; return (L loc cmd') }
tc_cmd :: CmdEnv -> HsCmd GhcRn -> CmdType -> TcM (HsCmd GhcTc)
tc_cmd env (HsCmdPar x lpar cmd rpar) res_ty
= do { cmd' <- tcCmd env cmd res_ty
; return (HsCmdPar x lpar cmd' rpar) }
tc_cmd env (HsCmdLet x tkLet binds tkIn (L body_loc body)) res_ty
= do { (binds', body') <- tcLocalBinds binds $
setSrcSpan (locA body_loc) $
tc_cmd env body res_ty
; return (HsCmdLet x tkLet binds' tkIn (L body_loc body')) }
tc_cmd env in_cmd@(HsCmdCase x scrut matches) (stk, res_ty)
= addErrCtxt (cmdCtxt in_cmd) $ do
(scrut', scrut_ty) <- tcInferRho scrut
hasFixedRuntimeRep_syntactic
(FRRArrow $ ArrowCmdCase)
scrut_ty
matches' <- tcCmdMatches env scrut_ty matches (stk, res_ty)
return (HsCmdCase x scrut' matches')
tc_cmd env cmd@(HsCmdLamCase x lc_variant match) cmd_ty
= addErrCtxt (cmdCtxt cmd)
do { let match_ctxt = ArrowLamCaseAlt lc_variant
; checkArgCounts (ArrowMatchCtxt match_ctxt) match
; (wrap, match') <-
tcCmdMatchLambda env match_ctxt match cmd_ty
; return (mkHsCmdWrap wrap (HsCmdLamCase x lc_variant match')) }
tc_cmd env (HsCmdIf x NoSyntaxExprRn pred b1 b2) res_ty -- Ordinary 'if'
= do { pred' <- tcCheckMonoExpr pred boolTy
; b1' <- tcCmd env b1 res_ty
; b2' <- tcCmd env b2 res_ty
; return (HsCmdIf x NoSyntaxExprTc pred' b1' b2')
}
tc_cmd env (HsCmdIf x fun@(SyntaxExprRn {}) pred b1 b2) res_ty -- Rebindable syntax for if
= do { pred_ty <- newOpenFlexiTyVarTy
-- For arrows, need ifThenElse :: forall r. T -> r -> r -> r
-- because we're going to apply it to the environment, not
-- the return value.
; skol_info <- mkSkolemInfo ArrowReboundIfSkol
; (_, [r_tv]) <- tcInstSkolTyVars skol_info [alphaTyVar]
; let r_ty = mkTyVarTy r_tv
; checkTc (not (r_tv `elemVarSet` tyCoVarsOfType pred_ty))
TcRnArrowIfThenElsePredDependsOnResultTy
; (pred', fun') <- tcSyntaxOp IfThenElseOrigin fun
(map synKnownType [pred_ty, r_ty, r_ty])
(mkCheckExpType r_ty) $ \ _ _ ->
tcCheckMonoExpr pred pred_ty
; b1' <- tcCmd env b1 res_ty
; b2' <- tcCmd env b2 res_ty
; return (HsCmdIf x fun' pred' b1' b2')
}
-------------------------------------------
-- Arrow application
-- (f -< a) or (f -<< a)
--
-- D |- fun :: a t1 t2
-- D,G |- arg :: t1
-- ------------------------
-- D;G |-a fun -< arg :: stk --> t2
--
-- D,G |- fun :: a t1 t2
-- D,G |- arg :: t1
-- ------------------------
-- D;G |-a fun -<< arg :: stk --> t2
--
-- (plus -<< requires ArrowApply)
tc_cmd env cmd@(HsCmdArrApp _ fun arg ho_app lr) (_, res_ty)
= addErrCtxt (cmdCtxt cmd) $
do { arg_ty <- newOpenFlexiTyVarTy
; let fun_ty = mkCmdArrTy env arg_ty res_ty
; fun' <- select_arrow_scope (tcCheckMonoExpr fun fun_ty)
; arg' <- tcCheckMonoExpr arg arg_ty
; hasFixedRuntimeRep_syntactic
(FRRArrow $ ArrowCmdArrApp (unLoc fun) (unLoc arg) ho_app)
fun_ty
; return (HsCmdArrApp fun_ty fun' arg' ho_app lr) }
where
-- Before type-checking f, use the environment of the enclosing
-- proc for the (-<) case.
-- Local bindings, inside the enclosing proc, are not in scope
-- inside f. In the higher-order case (-<<), they are.
-- See Note [Escaping the arrow scope] in GHC.Tc.Types
select_arrow_scope tc = case ho_app of
HsHigherOrderApp -> tc
HsFirstOrderApp -> escapeArrowScope tc
-------------------------------------------
-- Command application
--
-- D,G |- exp : t
-- D;G |-a cmd : (t,stk) --> res
-- -----------------------------
-- D;G |-a cmd exp : stk --> res
tc_cmd env cmd@(HsCmdApp x fun arg) (cmd_stk, res_ty)
= addErrCtxt (cmdCtxt cmd) $
do { arg_ty <- newOpenFlexiTyVarTy
; fun' <- tcCmd env fun (mkPairTy arg_ty cmd_stk, res_ty)
; arg' <- tcCheckMonoExpr arg arg_ty
; hasFixedRuntimeRep_syntactic
(FRRArrow $ ArrowCmdApp (unLoc fun) (unLoc arg))
arg_ty
; return (HsCmdApp x fun' arg') }
-------------------------------------------
-- Lambda
--
-- D;G,x:t |-a cmd : stk --> res
-- ------------------------------
-- D;G |-a (\x.cmd) : (t,stk) --> res
tc_cmd env (HsCmdLam x match) cmd_ty
= do { (wrap, match') <- tcCmdMatchLambda env KappaExpr match cmd_ty
; return (mkHsCmdWrap wrap (HsCmdLam x match')) }
-------------------------------------------
-- Do notation
tc_cmd env (HsCmdDo _ (L l stmts) ) (cmd_stk, res_ty)
= do { co <- unifyType Nothing unitTy cmd_stk -- Expecting empty argument stack
; stmts' <- tcStmts ArrowExpr (tcArrDoStmt env) stmts res_ty
; return (mkHsCmdWrap (mkWpCastN co) (HsCmdDo res_ty (L l stmts') )) }
-----------------------------------------------------------------
-- Arrow ``forms'' (| e c1 .. cn |)
--
-- D; G |-a1 c1 : stk1 --> r1
-- ...
-- D; G |-an cn : stkn --> rn
-- D |- e :: forall e. a1 (e, stk1) t1
-- ...
-- -> an (e, stkn) tn
-- -> a (e, stk) t
-- e \not\in (stk, stk1, ..., stkm, t, t1, ..., tn)
-- ----------------------------------------------
-- D; G |-a (| e c1 ... cn |) : stk --> t
tc_cmd env cmd@(HsCmdArrForm x expr f fixity cmd_args) (cmd_stk, res_ty)
= addErrCtxt (cmdCtxt cmd)
do { (cmd_args', cmd_tys) <- mapAndUnzipM tc_cmd_arg cmd_args
-- We use alphaTyVar for 'w'
; let e_ty = mkInfForAllTy alphaTyVar $
mkVisFunTysMany cmd_tys $
mkCmdArrTy env (mkPairTy alphaTy cmd_stk) res_ty
; expr' <- tcCheckPolyExpr expr e_ty
; return (HsCmdArrForm x expr' f fixity cmd_args') }
where
tc_cmd_arg :: LHsCmdTop GhcRn -> TcM (LHsCmdTop GhcTc, TcType)
tc_cmd_arg cmd@(L loc (HsCmdTop names _))
= do { arr_ty <- newFlexiTyVarTy arrowTyConKind
; stk_ty <- newFlexiTyVarTy liftedTypeKind
; res_ty <- newFlexiTyVarTy liftedTypeKind
; names' <- setSrcSpanA loc $
mapM (tcSyntaxName ArrowCmdOrigin arr_ty) names
; let env' = env { cmd_arr = arr_ty }
; cmd' <- tcCmdTop env' names' cmd (stk_ty, res_ty)
; return (cmd', mkCmdArrTy env' (mkPairTy alphaTy stk_ty) res_ty) }
-- | Typechecking for case command alternatives. Used for 'HsCmdCase'.
tcCmdMatches :: CmdEnv
-> TcTypeFRR -- ^ Type of the scrutinee.
-> MatchGroup GhcRn (LHsCmd GhcRn) -- ^ case alternatives
-> CmdType
-> TcM (MatchGroup GhcTc (LHsCmd GhcTc))
tcCmdMatches env scrut_ty matches (stk, res_ty)
= tcMatchesCase match_ctxt (unrestricted scrut_ty) matches (mkCheckExpType res_ty)
where
match_ctxt = MC { mc_what = ArrowMatchCtxt ArrowCaseAlt,
mc_body = mc_body }
mc_body body res_ty' = do { res_ty' <- expTypeToType res_ty'
; tcCmd env body (stk, res_ty') }
-- | Typechecking for 'HsCmdLam' and 'HsCmdLamCase'.
tcCmdMatchLambda :: CmdEnv
-> HsArrowMatchContext
-> MatchGroup GhcRn (LHsCmd GhcRn)
-> CmdType
-> TcM (HsWrapper, MatchGroup GhcTc (LHsCmd GhcTc))
tcCmdMatchLambda env
ctxt
mg@MG { mg_alts = L l matches, mg_ext = origin }
(cmd_stk, res_ty)
= do { (co, arg_tys, cmd_stk') <- matchExpectedCmdArgs n_pats cmd_stk
; let check_arg_tys = map (unrestricted . mkCheckExpType) arg_tys
; matches' <- forM matches $
addErrCtxt . pprMatchInCtxt . unLoc <*> tc_match check_arg_tys cmd_stk'
; let arg_tys' = map unrestricted arg_tys
mg' = mg { mg_alts = L l matches'
, mg_ext = MatchGroupTc arg_tys' res_ty origin }
; return (mkWpCastN co, mg') }
where
n_pats | isEmptyMatchGroup mg = 1 -- must be lambda-case
| otherwise = matchGroupArity mg
-- Check the patterns, and the GRHSs inside
tc_match arg_tys cmd_stk' (L mtch_loc (Match { m_pats = pats, m_grhss = grhss }))
= do { (pats', grhss') <- setSrcSpanA mtch_loc $
tcPats match_ctxt pats arg_tys $
tc_grhss grhss cmd_stk' (mkCheckExpType res_ty)
; return $ L mtch_loc (Match { m_ext = noAnn
, m_ctxt = match_ctxt
, m_pats = pats'
, m_grhss = grhss' }) }
match_ctxt = ArrowMatchCtxt ctxt
pg_ctxt = PatGuard match_ctxt
tc_grhss (GRHSs x grhss binds) stk_ty res_ty
= do { (binds', grhss') <- tcLocalBinds binds $
mapM (wrapLocMA (tc_grhs stk_ty res_ty)) grhss
; return (GRHSs x grhss' binds') }
tc_grhs stk_ty res_ty (GRHS x guards body)
= do { (guards', rhs') <- tcStmtsAndThen pg_ctxt tcGuardStmt guards res_ty $
\ res_ty -> tcCmd env body
(stk_ty, checkingExpType "tc_grhs" res_ty)
; return (GRHS x guards' rhs') }
matchExpectedCmdArgs :: Arity -> TcType -> TcM (TcCoercionN, [TcTypeFRR], TcType)
matchExpectedCmdArgs 0 ty
= return (mkNomReflCo ty, [], ty)
matchExpectedCmdArgs n ty
= do { (co1, [ty1, ty2]) <- matchExpectedTyConApp pairTyCon ty
; (co2, tys, res_ty) <- matchExpectedCmdArgs (n-1) ty2
; return (mkTyConAppCo Nominal pairTyCon [co1, co2], ty1:tys, res_ty) }
{-
************************************************************************
* *
Stmts
* *
************************************************************************
-}
--------------------------------
-- Mdo-notation
-- The distinctive features here are
-- (a) RecStmts, and
-- (b) no rebindable syntax
tcArrDoStmt :: CmdEnv -> TcCmdStmtChecker
tcArrDoStmt env _ (LastStmt x rhs noret _) res_ty thing_inside
= do { rhs' <- tcCmd env rhs (unitTy, res_ty)
; thing <- thing_inside (panic "tcArrDoStmt")
; return (LastStmt x rhs' noret noSyntaxExpr, thing) }
tcArrDoStmt env _ (BodyStmt _ rhs _ _) res_ty thing_inside
= do { (rhs', elt_ty) <- tc_arr_rhs env rhs
; thing <- thing_inside res_ty
; return (BodyStmt elt_ty rhs' noSyntaxExpr noSyntaxExpr, thing) }
tcArrDoStmt env ctxt (BindStmt _ pat rhs) res_ty thing_inside
= do { (rhs', pat_ty) <- tc_arr_rhs env rhs
; (pat', thing) <- tcCheckPat (StmtCtxt ctxt) pat (unrestricted pat_ty) $
thing_inside res_ty
; return (mkTcBindStmt pat' rhs', thing) }
tcArrDoStmt env ctxt (RecStmt { recS_stmts = L l stmts, recS_later_ids = later_names
, recS_rec_ids = rec_names }) res_ty thing_inside
= do { let tup_names = rec_names ++ filterOut (`elem` rec_names) later_names
; tup_elt_tys <- newFlexiTyVarTys (length tup_names) liftedTypeKind
; let tup_ids = zipWith (\n p -> mkLocalId n ManyTy p) tup_names tup_elt_tys
-- Many because it's a recursive definition
; tcExtendIdEnv tup_ids $ do
{ (stmts', tup_rets)
<- tcStmtsAndThen ctxt (tcArrDoStmt env) stmts res_ty $ \ _res_ty' ->
-- ToDo: res_ty not really right
zipWithM tcCheckId tup_names (map mkCheckExpType tup_elt_tys)
; thing <- thing_inside res_ty
-- NB: The rec_ids for the recursive things
-- already scope over this part. This binding may shadow
-- some of them with polymorphic things with the same Name
-- (see Note [How RecStmt works] in Language.Haskell.Syntax.Expr)
; let rec_ids = takeList rec_names tup_ids
; later_ids <- tcLookupLocalIds later_names
; let rec_rets = takeList rec_names tup_rets
; let ret_table = zip tup_ids tup_rets
; let later_rets = [r | i <- later_ids, (j, r) <- ret_table, i == j]
; let
stmt :: Stmt GhcTc (LocatedA (HsCmd GhcTc))
stmt = emptyRecStmtId
{ recS_stmts = L l stmts'
-- { recS_stmts = _ stmts'
, recS_later_ids = later_ids
, recS_rec_ids = rec_ids
, recS_ext = unitRecStmtTc
{ recS_later_rets = later_rets
, recS_rec_rets = rec_rets
, recS_ret_ty = res_ty} }
; return (stmt, thing)
}}
tcArrDoStmt _ _ stmt _ _
= pprPanic "tcArrDoStmt: unexpected Stmt" (ppr stmt)
tc_arr_rhs :: CmdEnv -> LHsCmd GhcRn -> TcM (LHsCmd GhcTc, TcType)
tc_arr_rhs env rhs = do { ty <- newFlexiTyVarTy liftedTypeKind
; rhs' <- tcCmd env rhs (unitTy, ty)
; return (rhs', ty) }
{-
************************************************************************
* *
Helpers
* *
************************************************************************
-}
mkPairTy :: Type -> Type -> Type
mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2]
arrowTyConKind :: Kind -- *->*->*
arrowTyConKind = mkVisFunTysMany [liftedTypeKind, liftedTypeKind] liftedTypeKind
{-
************************************************************************
* *
Errors
* *
************************************************************************
-}
cmdCtxt :: HsCmd GhcRn -> SDoc
cmdCtxt cmd = text "In the command:" <+> ppr cmd