import TysWiredIn
import TcGadt
import Type
+import Coercion
import StaticFlags
import TyCon
import DataCon
+import DynFlags
import PrelNames
import BasicTypes hiding (SuccessFlag(..))
import SrcLoc
-> TcM (LPat TcId, a)
tcLetPat sig_fn pat pat_ty thing_inside
= do { let init_state = PS { pat_ctxt = LetPat sig_fn,
- pat_reft = emptyRefinement }
+ pat_reft = emptyRefinement,
+ pat_eqs = False }
; (pat', ex_tvs, res) <- tc_lpat pat pat_ty init_state (\ _ -> thing_inside)
-- Don't know how to deal with pattern-bound existentials yet
-> ((Refinement,BoxyRhoType) -> TcM a) -- Checker for body, given its result type
-> TcM ([LPat TcId], a)
tc_lam_pats pat_ty_prs (reft, res_ty) thing_inside
- = do { let init_state = PS { pat_ctxt = LamPat, pat_reft = reft }
+ = do { let init_state = PS { pat_ctxt = LamPat, pat_reft = reft, pat_eqs = False }
; (pats', ex_tvs, res) <- tcMultiple tc_lpat_pr pat_ty_prs init_state $ \ pstate' ->
- refineEnvironment (pat_reft pstate') $
- thing_inside (pat_reft pstate', res_ty)
+ refineEnvironment (pat_reft pstate') (pat_eqs pstate') $
+ if (pat_eqs pstate' && (not $ isRigidTy res_ty))
+ then failWithTc (nonRigidResult res_ty)
+ else thing_inside (pat_reft pstate', res_ty)
; let tys = map snd pat_ty_prs
; tcCheckExistentialPat pats' ex_tvs tys res_ty
data PatState = PS {
pat_ctxt :: PatCtxt,
- pat_reft :: Refinement -- Binds rigid TcTyVars to their refinements
+ pat_reft :: Refinement, -- Binds rigid TcTyVars to their refinements
+ pat_eqs :: Bool -- <=> there are GADT equational constraints
+ -- for refinement
}
data PatCtxt
------------------------
-- Literal patterns
tc_pat pstate (LitPat simple_lit) pat_ty thing_inside
- = do { boxyUnify (hsLitType simple_lit) pat_ty
+ = do { let lit_ty = hsLitType simple_lit
+ ; coi <- boxyUnify lit_ty pat_ty
+ -- coi is of kind: lit_ty ~ pat_ty
; res <- thing_inside pstate
- ; returnM (LitPat simple_lit, [], res) }
+ ; span <- getSrcSpanM
+ -- pattern coercions have to
+ -- be of kind: pat_ty ~ lit_ty
+ -- hence, sym coi
+ ; returnM (wrapPatCoI (mkSymCoI coi) (LitPat simple_lit) pat_ty, [], res) }
------------------------
-- Overloaded patterns: n, and n+k
; res <- tcExtendIdEnv1 name bndr_id (thing_inside pstate)
; returnM (NPlusKPat (L nm_loc bndr_id) lit' ge' minus', [], res) }
-tc_pat _ _other_pat _ _ = panic "tc_pat" -- DictPat, ConPatOut, SigPatOut, VarPatOut
+tc_pat _ _other_pat _ _ = panic "tc_pat" -- ConPatOut, SigPatOut, VarPatOut
\end{code}
tcConPat :: PatState -> SrcSpan -> DataCon -> TyCon
-> BoxySigmaType -- Type of the pattern
- -> HsConDetails Name (LPat Name) -> (PatState -> TcM a)
+ -> HsConPatDetails Name -> (PatState -> TcM a)
-> TcM (Pat TcId, [TcTyVar], a)
tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside
- = do { let (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _) = dataConFullSig data_con
+ = do { let (univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _) = dataConFullSig data_con
skol_info = PatSkol data_con
origin = SigOrigin skol_info
; let tenv = zipTopTvSubst (univ_tvs ++ ex_tvs)
(ctxt_res_tys ++ mkTyVarTys ex_tvs')
eq_spec' = substEqSpec tenv eq_spec
- theta' = substTheta tenv theta
+ theta' = substTheta tenv (eq_theta ++ dict_theta)
arg_tys' = substTys tenv arg_tys
; co_vars <- newCoVars eq_spec' -- Make coercion variables
; pstate' <- refineAlt data_con pstate ex_tvs' co_vars pat_ty
-
+
; ((arg_pats', inner_tvs, res), lie_req) <- getLIE $
tcConArgs data_con arg_tys' arg_pats pstate' thing_inside
tcConArgs :: DataCon -> [TcSigmaType]
- -> Checker (HsConDetails Name (LPat Name))
- (HsConDetails Id (LPat Id))
+ -> Checker (HsConPatDetails Name) (HsConPatDetails Id)
tcConArgs data_con arg_tys (PrefixCon arg_pats) pstate thing_inside
= do { checkTc (con_arity == no_of_args) -- Check correct arity
tcConArgs data_con other_args (InfixCon p1 p2) pstate thing_inside
= pprPanic "tcConArgs" (ppr data_con) -- InfixCon always has two arguments
-tcConArgs data_con arg_tys (RecCon rpats) pstate thing_inside
+tcConArgs data_con arg_tys (RecCon (HsRecFields rpats dd)) pstate thing_inside
= do { (rpats', tvs, res) <- tcMultiple tc_field rpats pstate thing_inside
- ; return (RecCon rpats', tvs, res) }
+ ; return (RecCon (HsRecFields rpats' dd), tvs, res) }
where
- -- doc comments are typechecked to Nothing here
tc_field :: Checker (HsRecField FieldLabel (LPat Name)) (HsRecField TcId (LPat TcId))
- tc_field (HsRecField field_lbl pat _) pstate thing_inside
+ tc_field (HsRecField field_lbl pat pun) pstate thing_inside
= do { (sel_id, pat_ty) <- wrapLocFstM find_field_ty field_lbl
; (pat', tvs, res) <- tcConArg (pat, pat_ty) pstate thing_inside
- ; return (mkRecField sel_id pat', tvs, res) }
+ ; return (HsRecField sel_id pat' pun, tvs, res) }
find_field_ty :: FieldLabel -> TcM (Id, TcType)
find_field_ty field_lbl
-> TcM PatState
refineAlt con pstate ex_tvs [] pat_ty
+ | null $ dataConEqTheta con
= return pstate -- Common case: no equational constraints
refineAlt con pstate ex_tvs co_vars pat_ty
- | not (isRigidTy pat_ty)
- = failWithTc (nonRigidMatch con)
+ = do { opt_gadt <- doptM Opt_GADTs -- No type-refinement unless GADTs are on
+ ; if (not opt_gadt) then return pstate
+ else do
+
+ { checkTc (isRigidTy pat_ty) (nonRigidMatch con)
-- We are matching against a GADT constructor with non-trivial
-- constraints, but pattern type is wobbly. For now we fail.
-- We can make sense of this, however:
-- then unify these constraints to make pat_ty the right shape;
-- then proceed exactly as in the rigid case
- | otherwise -- In the rigid case, we perform type refinement
- = case gadtRefine (pat_reft pstate) ex_tvs co_vars of {
+ -- In the rigid case, we perform type refinement
+ ; case gadtRefine (pat_reft pstate) ex_tvs co_vars of {
Failed msg -> failWithTc (inaccessibleAlt msg) ;
Succeeded reft -> do { traceTc trace_msg
- ; return (pstate { pat_reft = reft }) }
+ ; return (pstate { pat_reft = reft, pat_eqs = (pat_eqs pstate || not (null $ dataConEqTheta con)) }) }
-- DO NOT refine the envt right away, because we
-- might be inside a lazy pattern. Instead, refine pstate
where
vcat [ ppr con <+> ppr ex_tvs,
ppr [(v, tyVarKind v) | v <- co_vars],
ppr reft]
- }
+ } } }
\end{code}
existentialExplode pat
= hang (vcat [text "My brain just exploded.",
text "I can't handle pattern bindings for existentially-quantified constructors.",
+ text "Instead, use a case-expression, or do-notation, to unpack the constructor.",
text "In the binding group for"])
4 (ppr pat)
= hang (ptext SLIT("GADT pattern match in non-rigid context for") <+> quotes (ppr con))
2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context"))
+nonRigidResult res_ty
+ = hang (ptext SLIT("GADT pattern match with non-rigid result type") <+> quotes (ppr res_ty))
+ 2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context"))
+
inaccessibleAlt msg
= hang (ptext SLIT("Inaccessible case alternative:")) 2 msg
\end{code}
+
+\begin{code}
+wrapPatCoI :: CoercionI -> Pat a -> TcType -> Pat a
+wrapPatCoI IdCo pat ty = pat
+wrapPatCoI (ACo co) pat ty = CoPat (WpCo co) pat ty
+\end{code}