) $
-- TYPECHECK THE BINDINGS
- getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', binder_names, mono_ids), lie_req) ->
+ getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', bndr_names_w_ids), lie_req) ->
let
+ (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids)
tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
in
\begin{code}
tcMonoBinds :: RenamedMonoBinds
- -> [TcSigInfo]
- -> RecFlag
+ -> [TcSigInfo] -> RecFlag
-> TcM (TcMonoBinds,
- [Name], -- Bound names
- [TcId]) -- Corresponding monomorphic bound things
+ Bag (Name, -- Bound names
+ TcId)) -- Corresponding monomorphic bound things
tcMonoBinds mbinds tc_ty_sigs is_rec
- = tc_mb_pats mbinds `thenM` \ (complete_it, tvs, ids, lie_avail) ->
- let
- id_list = bagToList ids
- (names, mono_ids) = unzip id_list
-
- -- This last defn is the key one:
- -- extend the val envt with bindings for the
- -- things bound in this group, overriding the monomorphic
- -- ids with the polymorphic ones from the pattern
- extra_val_env = case is_rec of
- Recursive -> map mk_bind id_list
- NonRecursive -> []
- in
- -- Don't know how to deal with pattern-bound existentials yet
- checkTc (isEmptyBag tvs && null lie_avail)
- (existentialExplode mbinds) `thenM_`
-
- -- *Before* checking the RHSs, but *after* checking *all* the patterns,
- -- extend the envt with bindings for all the bound ids;
- -- and *then* override with the polymorphic Ids from the signatures
- -- That is the whole point of the "complete_it" stuff.
- --
- -- There's a further wrinkle: we have to delay extending the environment
- -- until after we've dealt with any pattern-bound signature type variables
- -- Consider f (x::a) = ...f...
- -- We're going to check that a isn't unified with anything in the envt,
- -- so f itself had better not be! So we pass the envt binding f into
- -- complete_it, which extends the actual envt in TcMatches.tcMatch, after
- -- dealing with the signature tyvars
-
- complete_it extra_val_env `thenM` \ mbinds' ->
-
- returnM (mbinds', names, mono_ids)
+ -- Three stages:
+ -- 1. Check the patterns, building up an environment binding
+ -- the variables in this group (in the recursive case)
+ -- 2. Extend the environment
+ -- 3. Check the RHSs
+ = tc_mb_pats mbinds `thenM` \ (complete_it, xve) ->
+ tcExtendLocalValEnv2 (bagToList xve) complete_it
where
-
- mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of
- Nothing -> (name, mono_id)
- Just sig -> (idName poly_id, poly_id)
- where
- poly_id = tcSigPolyId sig
-
- tc_mb_pats EmptyMonoBinds
- = returnM (\ xve -> returnM EmptyMonoBinds, emptyBag, emptyBag, [])
+ tc_mb_pats EmptyMonoBinds
+ = returnM (returnM (EmptyMonoBinds, emptyBag), emptyBag)
tc_mb_pats (AndMonoBinds mb1 mb2)
- = tc_mb_pats mb1 `thenM` \ (complete_it1, tvs1, ids1, lie_avail1) ->
- tc_mb_pats mb2 `thenM` \ (complete_it2, tvs2, ids2, lie_avail2) ->
+ = tc_mb_pats mb1 `thenM` \ (complete_it1, xve1) ->
+ tc_mb_pats mb2 `thenM` \ (complete_it2, xve2) ->
let
- complete_it xve = complete_it1 xve `thenM` \ mb1' ->
- complete_it2 xve `thenM` \ mb2' ->
- returnM (AndMonoBinds mb1' mb2')
+ complete_it = complete_it1 `thenM` \ (mb1', bs1) ->
+ complete_it2 `thenM` \ (mb2', bs2) ->
+ returnM (AndMonoBinds mb1' mb2', bs1 `unionBags` bs2)
in
- returnM (complete_it,
- tvs1 `unionBags` tvs2,
- ids1 `unionBags` ids2,
- lie_avail1 ++ lie_avail2)
+ returnM (complete_it, xve1 `unionBags` xve2)
tc_mb_pats (FunMonoBind name inf matches locn)
- = (case maybeSig tc_ty_sigs name of
- Just sig -> returnM (tcSigMonoId sig)
- Nothing -> newLocalName name `thenM` \ bndr_name ->
- newTyVarTy openTypeKind `thenM` \ bndr_ty ->
- -- NB: not a 'hole' tyvar; since there is no type
- -- signature, we revert to ordinary H-M typechecking
- -- which means the variable gets an inferred tau-type
- returnM (mkLocalId bndr_name bndr_ty)
- ) `thenM` \ bndr_id ->
+ -- Three cases:
+ -- a) Type sig supplied
+ -- b) No type sig and recursive
+ -- c) No type sig and non-recursive
+
+ | Just sig <- maybeSig tc_ty_sigs name
+ = let -- (a) There is a type signature
+ -- Use it for the environment extension, and check
+ -- the RHS has the appropriate type (with outer for-alls stripped off)
+ mono_id = tcSigMonoId sig
+ mono_ty = idType mono_id
+ complete_it = addSrcLoc locn $
+ tcMatchesFun name mono_ty matches `thenM` \ matches' ->
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, if isRec is_rec then unitBag (name,tcSigPolyId sig)
+ else emptyBag)
+
+ | isRec is_rec
+ = -- (b) No type signature, and recursive
+ -- So we must use an ordinary H-M type variable
+ -- which means the variable gets an inferred tau-type
+ newLocalName name `thenM` \ mono_name ->
+ newTyVarTy openTypeKind `thenM` \ mono_ty ->
let
- bndr_ty = idType bndr_id
- complete_it xve = addSrcLoc locn $
- tcMatchesFun xve name bndr_ty matches `thenM` \ matches' ->
- returnM (FunMonoBind bndr_id inf matches' locn)
+ mono_id = mkLocalId mono_name mono_ty
+ complete_it = addSrcLoc locn $
+ tcMatchesFun name mono_ty matches `thenM` \ matches' ->
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
in
- returnM (complete_it, emptyBag, unitBag (name, bndr_id), [])
-
+ returnM (complete_it, unitBag (name, mono_id))
+
+ | otherwise -- (c) No type signature, and non-recursive
+ = let -- So we can use a 'hole' type to infer a higher-rank type
+ complete_it
+ = addSrcLoc locn $
+ newHoleTyVarTy `thenM` \ fun_ty ->
+ tcMatchesFun name fun_ty matches `thenM` \ matches' ->
+ readHoleResult fun_ty `thenM` \ fun_ty' ->
+ newLocalName name `thenM` \ mono_name ->
+ let
+ mono_id = mkLocalId mono_name fun_ty'
+ in
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, emptyBag)
+
tc_mb_pats bind@(PatMonoBind pat grhss locn)
= addSrcLoc locn $
- newHoleTyVarTy `thenM` \ pat_ty ->
-- Now typecheck the pattern
-- We do now support binding fresh (not-already-in-scope) scoped
-- The type variables are brought into scope in tc_binds_and_then,
-- so we don't have to do anything here.
- tcPat tc_pat_bndr pat pat_ty `thenM` \ (pat', tvs, ids, lie_avail) ->
- readHoleResult pat_ty `thenM` \ pat_ty' ->
+ newHoleTyVarTy `thenM` \ pat_ty ->
+ tcPat tc_pat_bndr pat pat_ty `thenM` \ (pat', tvs, ids, lie_avail) ->
+ readHoleResult pat_ty `thenM` \ pat_ty' ->
+
+ -- Don't know how to deal with pattern-bound existentials yet
+ checkTc (isEmptyBag tvs && null lie_avail)
+ (existentialExplode bind) `thenM_`
+
let
- complete_it xve = addSrcLoc locn $
- addErrCtxt (patMonoBindsCtxt bind) $
- tcExtendLocalValEnv2 xve $
- tcGRHSs PatBindRhs grhss pat_ty' `thenM` \ grhss' ->
- returnM (PatMonoBind pat' grhss' locn)
+ complete_it = addSrcLoc locn $
+ addErrCtxt (patMonoBindsCtxt bind) $
+ tcGRHSs PatBindRhs grhss pat_ty' `thenM` \ grhss' ->
+ returnM (PatMonoBind pat' grhss' locn, ids)
in
- returnM (complete_it, tvs, ids, lie_avail)
+ returnM (complete_it, if isRec is_rec then ids else emptyBag)
-- tc_pat_bndr is used when dealing with a LHS binder in a pattern.
-- If there was a type sig for that Id, we want to make it much
tc_pat_bndr name pat_ty
= case maybeSig tc_ty_sigs name of
- Nothing
- -> newLocalName name `thenM` \ bndr_name ->
- tcMonoPatBndr bndr_name pat_ty
+ Nothing -> newLocalName name `thenM` \ bndr_name ->
+ tcMonoPatBndr bndr_name pat_ty
Just sig -> addSrcLoc (getSrcLoc name) $
tcSubPat (idType mono_id) pat_ty `thenM` \ co_fn ->
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