[project @ 2003-09-20 17:26:46 by ross]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcBinds.lhs

diff --git a/ghc/compiler/typecheck/TcBinds.lhs b/ghc/compiler/typecheck/TcBinds.lhs
index a33e7f4..b5d2cb7 100644 (file)
--- a/ghc/compiler/typecheck/TcBinds.lhs
+++ b/ghc/compiler/typecheck/TcBinds.lhs
@@ -4,61 +4,51 @@
 \section[TcBinds]{TcBinds}
 
 \begin{code}
 \section[TcBinds]{TcBinds}
 
 \begin{code}

-module TcBinds ( tcBindsAndThen, tcTopBinds,
-                tcSpecSigs, tcBindWithSigs ) where
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where

 
 #include "HsVersions.h"
 
 
 #include "HsVersions.h"
 

-import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun )
-import {-# SOURCE #-} TcExpr  ( tcExpr )
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr  ( tcCheckSigma, tcCheckRho )

 
 

-import HsSyn           ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), StmtCtxt(..),
-                         Match(..), collectMonoBinders, andMonoBinds
+import CmdLineOpts     ( DynFlag(Opt_NoMonomorphismRestriction) )
+import HsSyn           ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), 
+                         Match(..), mkMonoBind,
+                         collectMonoBinders, andMonoBinds,
+                         collectSigTysFromMonoBinds

                        )
 import RnHsSyn         ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
                        )
 import RnHsSyn         ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )

-import TcHsSyn         ( TcMonoBinds, TcId, zonkId, mkHsLet )
-
-import TcMonad
-import Inst            ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..),
-                         newDicts, tyVarsOfInst, instToId,
-                         getAllFunDepsOfLIE, getIPsOfLIE, zonkFunDeps
-                       )
-import TcEnv           ( tcExtendLocalValEnv,
-                         newSpecPragmaId, newLocalId,
-                         tcLookupTyCon, 
-                         tcGetGlobalTyVars, tcExtendGlobalTyVars
-                       )
-import TcSimplify      ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts )
-import TcImprove       ( tcImprove )
-import TcMonoType      ( tcHsSigType, checkSigTyVars,
-                         TcSigInfo(..), tcTySig, maybeSig, sigCtxt
+import TcHsSyn         ( TcHsBinds, TcMonoBinds, TcId, zonkId, mkHsLet )
+
+import TcRnMonad
+import Inst            ( InstOrigin(..), newDicts, newIPDict, instToId )
+import TcEnv           ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName )
+import TcUnify         ( Expected(..), newHole, unifyTauTyLists, checkSigTyVarsWrt, sigCtxt )
+import TcSimplify      ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, 
+                         tcSimplifyToDicts, tcSimplifyIPs )
+import TcMonoType      ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..), 
+                         tcTySig, maybeSig, tcSigPolyId, tcSigMonoId, tcAddScopedTyVars

                        )
                        )

-import TcPat           ( tcPat )
+import TcPat           ( tcPat, tcSubPat, tcMonoPatBndr )

 import TcSimplify      ( bindInstsOfLocalFuns )
 import TcSimplify      ( bindInstsOfLocalFuns )

-import TcType          ( TcThetaType, newTyVarTy, newTyVar, 
-                         zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar
+import TcMType         ( newTyVar, newTyVarTy, zonkTcTyVarToTyVar )
+import TcType          ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType, 
+                         mkPredTy, mkForAllTy, isUnLiftedType, 
+                         unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind

                        )
                        )

-import TcUnify         ( unifyTauTy, unifyTauTyLists )

 
 

-import Id              ( mkVanillaId, setInlinePragma, idFreeTyVars )
+import CoreFVs         ( idFreeTyVars )
+import Id              ( mkLocalId, mkSpecPragmaId, setInlinePragma )

 import Var             ( idType, idName )
 import Var             ( idType, idName )

-import IdInfo          ( InlinePragInfo(..) )
-import Name            ( Name, getOccName, getSrcLoc )
+import Name            ( Name, getSrcLoc )

 import NameSet
 import NameSet

-import Type            ( mkTyVarTy, tyVarsOfTypes, mkTyConApp,
-                         mkForAllTys, mkFunTys, 
-                         mkPredTy, mkForAllTy, isUnLiftedType, 
-                         isUnboxedType, unboxedTypeKind, boxedTypeKind, openTypeKind
-                       )
-import FunDeps         ( tyVarFunDep, oclose )

 import Var             ( tyVarKind )
 import VarSet
 import Bag
 import Var             ( tyVarKind )
 import VarSet
 import Bag

-import Util            ( isIn )
-import Maybes          ( maybeToBool )
-import BasicTypes      ( TopLevelFlag(..), RecFlag(..), isNotTopLevel )
+import Util            ( isIn, equalLength )
+import BasicTypes      ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec, 
+                         isNotTopLevel, isAlwaysActive )

 import FiniteMap       ( listToFM, lookupFM )
 import FiniteMap       ( listToFM, lookupFM )

-import PrelNames       ( ioTyConName, mainKey, hasKey )

 import Outputable
 \end{code}
 
 import Outputable
 \end{code}
 

@@ -95,20 +85,29 @@ At the top-level the LIE is sure to contain nothing but constant
 dictionaries, which we resolve at the module level.
 
 \begin{code}
 dictionaries, which we resolve at the module level.
 
 \begin{code}

-tcTopBinds :: RenamedHsBinds -> TcM ((TcMonoBinds, TcEnv), LIE)
+tcTopBinds :: RenamedHsBinds -> TcM (TcMonoBinds, TcLclEnv)
+       -- Note: returning the TcLclEnv is more than we really
+       --       want.  The bit we care about is the local bindings
+       --       and the free type variables thereof

 tcTopBinds binds
   = tc_binds_and_then TopLevel glue binds      $
 tcTopBinds binds
   = tc_binds_and_then TopLevel glue binds      $

-    tcGetEnv                                   `thenNF_Tc` \ env ->
-    returnTc ((EmptyMonoBinds, env), emptyLIE)
+    getLclEnv                                  `thenM` \ env ->
+    returnM (EmptyMonoBinds, env)

   where
   where

-    glue is_rec binds1 (binds2, thing) = (binds1 `AndMonoBinds` binds2, thing)
+       -- The top level bindings are flattened into a giant 
+       -- implicitly-mutually-recursive MonoBinds
+    glue binds1 (binds2, env) = (flatten binds1 `AndMonoBinds` binds2, env)
+    flatten EmptyBinds                 = EmptyMonoBinds
+    flatten (b1 `ThenBinds` b2) = flatten b1 `AndMonoBinds` flatten b2
+    flatten (MonoBind b _ _)   = b
+       -- Can't have a IPBinds at top level

 
 
 tcBindsAndThen
 
 
 tcBindsAndThen

-       :: (RecFlag -> TcMonoBinds -> thing -> thing)           -- Combinator
+       :: (TcHsBinds -> thing -> thing)                -- Combinator

        -> RenamedHsBinds
        -> RenamedHsBinds

-       -> TcM (thing, LIE)
-       -> TcM (thing, LIE)
+       -> TcM thing
+       -> TcM thing

 
 tcBindsAndThen = tc_binds_and_then NotTopLevel
 
 
 tcBindsAndThen = tc_binds_and_then NotTopLevel
 

@@ -122,91 +121,88 @@ tc_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next
     tc_binds_and_then top_lvl combiner b2      $
     do_next
 
     tc_binds_and_then top_lvl combiner b2      $
     do_next
 

+tc_binds_and_then top_lvl combiner (IPBinds binds is_with) do_next
+  = getLIE do_next                     `thenM` \ (result, expr_lie) ->
+    mapAndUnzipM tc_ip_bind binds      `thenM` \ (avail_ips, binds') ->
+
+       -- If the binding binds ?x = E, we  must now 
+       -- discharge any ?x constraints in expr_lie
+    tcSimplifyIPs avail_ips expr_lie   `thenM` \ dict_binds ->
+
+    returnM (combiner (IPBinds binds' is_with) $
+            combiner (mkMonoBind Recursive dict_binds) result)
+  where
+       -- I wonder if we should do these one at at time
+       -- Consider     ?x = 4
+       --              ?y = ?x + 1
+    tc_ip_bind (ip, expr)
+      = newTyVarTy openTypeKind                `thenM` \ ty ->
+       getSrcLocM                      `thenM` \ loc ->
+       newIPDict (IPBind ip) ip ty     `thenM` \ (ip', ip_inst) ->
+       tcCheckRho expr ty              `thenM` \ expr' ->
+       returnM (ip_inst, (ip', expr'))
+

 tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
 tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next

-  =    -- TYPECHECK THE SIGNATURES
-      mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs ->
-  
-      tcBindWithSigs top_lvl bind tc_ty_sigs
-                    sigs is_rec                        `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
-  
-         -- Extend the environment to bind the new polymorphic Ids
-      tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $
+  =    -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
+       -- Notice that they scope over 
+       --      a) the type signatures in the binding group
+       --      b) the bindings in the group
+       --      c) the scope of the binding group (the "in" part)
+      tcAddScopedTyVars (collectSigTysFromMonoBinds bind)      $
+
+      tcBindWithSigs top_lvl bind sigs is_rec  `thenM` \ (poly_binds, poly_ids) ->

   
   

-         -- Build bindings and IdInfos corresponding to user pragmas
-      tcSpecSigs sigs          `thenTc` \ (prag_binds, prag_lie) ->
-
-       -- Now do whatever happens next, in the augmented envt
-      do_next                  `thenTc` \ (thing, thing_lie) ->
-
-       -- Create specialisations of functions bound here
-       -- We want to keep non-recursive things non-recursive
-       -- so that we desugar unboxed bindings correctly
-      case (top_lvl, is_rec) of
-
-               -- For the top level don't bother will all this bindInstsOfLocalFuns stuff
-               -- All the top level things are rec'd together anyway, so it's fine to
-               -- leave them to the tcSimplifyTop, and quite a bit faster too
-       (TopLevel, _)
-               -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing,
-                            thing_lie `plusLIE` prag_lie `plusLIE` poly_lie)
-
-       (NotTopLevel, NonRecursive) 
-               -> bindInstsOfLocalFuns 
-                               (thing_lie `plusLIE` prag_lie)
-                               poly_ids                        `thenTc` \ (thing_lie', lie_binds) ->
-
-                  returnTc (
-                       combiner NonRecursive poly_binds $
-                       combiner NonRecursive prag_binds $
-                       combiner Recursive lie_binds  $
+      case top_lvl of
+       TopLevel        -- For the top level don't bother will all this
+                       --  bindInstsOfLocalFuns stuff. All the top level 
+                       -- things are rec'd together anyway, so it's fine to
+                       -- leave them to the tcSimplifyTop, and quite a bit faster too
+                       --
+                       -- Subtle (and ugly) point: furthermore at top level we
+                       -- return the TcLclEnv, which contains the LIE var; we
+                       -- don't want to return the wrong one!
+               -> tc_body poly_ids                     `thenM` \ (prag_binds, thing) ->
+                  returnM (combiner (mkMonoBind Recursive (poly_binds `andMonoBinds` prag_binds)) 
+                                    thing)
+
+       NotTopLevel     -- For nested bindings we must do teh bindInstsOfLocalFuns thing
+               -> getLIE (tc_body poly_ids)            `thenM` \ ((prag_binds, thing), lie) ->
+
+                       -- Create specialisations of functions bound here
+                   bindInstsOfLocalFuns lie poly_ids   `thenM` \ lie_binds ->
+
+                       -- We want to keep non-recursive things non-recursive
+                       -- so that we desugar unlifted bindings correctly
+                  if isRec is_rec then
+                    returnM (
+                       combiner (mkMonoBind Recursive (
+                               poly_binds `andMonoBinds`
+                               lie_binds  `andMonoBinds`
+                               prag_binds)) thing
+                    )
+                  else
+                    returnM (
+                       combiner (mkMonoBind NonRecursive poly_binds) $
+                       combiner (mkMonoBind NonRecursive prag_binds) $
+                       combiner (mkMonoBind Recursive lie_binds)     $

                                -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
                                -- aren't guaranteed in dependency order (though we could change
                                -- that); hence the Recursive marker.
                                -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
                                -- aren't guaranteed in dependency order (though we could change
                                -- that); hence the Recursive marker.

-                       thing,
-
-                       thing_lie' `plusLIE` poly_lie
-                  )
+                       thing)
+  where
+    tc_body poly_ids   -- Type check the pragmas and "thing inside"
+      =   -- Extend the environment to bind the new polymorphic Ids
+         tcExtendLocalValEnv poly_ids  $
+  
+         -- Build bindings and IdInfos corresponding to user pragmas
+         tcSpecSigs sigs               `thenM` \ prag_binds ->

 
 

-       (NotTopLevel, Recursive)
-               -> bindInstsOfLocalFuns 
-                               (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie) 
-                               poly_ids                        `thenTc` \ (final_lie, lie_binds) ->
+         -- Now do whatever happens next, in the augmented envt
+         do_next                       `thenM` \ thing ->

 
 

-                  returnTc (
-                       combiner Recursive (
-                               poly_binds `andMonoBinds`
-                               lie_binds  `andMonoBinds`
-                               prag_binds) thing,
-                       final_lie
-                  )
+         returnM (prag_binds, thing)

 \end{code}
 
 \end{code}
 

-An aside.  The original version of @tcBindsAndThen@ which lacks a
-combiner function, appears below.  Though it is perfectly well
-behaved, it cannot be typed by Haskell, because the recursive call is
-at a different type to the definition itself.  There aren't too many
-examples of this, which is why I thought it worth preserving! [SLPJ]
-
-\begin{pseudocode}
-% tcBindsAndThen
-%      :: RenamedHsBinds
-%      -> TcM (thing, LIE, thing_ty))
-%      -> TcM ((TcHsBinds, thing), LIE, thing_ty)
-% 
-% tcBindsAndThen EmptyBinds do_next
-%   = do_next          `thenTc` \ (thing, lie, thing_ty) ->
-%     returnTc ((EmptyBinds, thing), lie, thing_ty)
-% 
-% tcBindsAndThen (ThenBinds binds1 binds2) do_next
-%   = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
-%      `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
-% 
-%     returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-% 
-% tcBindsAndThen (MonoBind bind sigs is_rec) do_next
-%   = tcBindAndThen bind sigs do_next
-\end{pseudocode}
-

 
 %************************************************************************
 %*                                                                     *
 
 %************************************************************************
 %*                                                                     *

@@ -228,218 +224,166 @@ so all the clever stuff is in here.
 tcBindWithSigs 
        :: TopLevelFlag
        -> RenamedMonoBinds
 tcBindWithSigs 
        :: TopLevelFlag
        -> RenamedMonoBinds

-       -> [TcSigInfo]

        -> [RenamedSig]         -- Used solely to get INLINE, NOINLINE sigs
        -> RecFlag
        -> [RenamedSig]         -- Used solely to get INLINE, NOINLINE sigs
        -> RecFlag

-       -> TcM (TcMonoBinds, LIE, [TcId])
+       -> TcM (TcMonoBinds, [TcId])
+
+tcBindWithSigs top_lvl mbind sigs is_rec
+  =    -- TYPECHECK THE SIGNATURES
+     recoverM (returnM []) (
+       mappM tcTySig [sig | sig@(Sig name _ _) <- sigs]
+     )                                         `thenM` \ tc_ty_sigs ->

 
 

-tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec
-  = recoverTc (
+       -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+   recoverM (

        -- If typechecking the binds fails, then return with each
        -- signature-less binder given type (forall a.a), to minimise subsequent
        -- error messages
        -- If typechecking the binds fails, then return with each
        -- signature-less binder given type (forall a.a), to minimise subsequent
        -- error messages

-       newTyVar boxedTypeKind          `thenNF_Tc` \ alpha_tv ->
+       newTyVar liftedTypeKind         `thenM` \ alpha_tv ->

        let
          forall_a_a    = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
           binder_names  = collectMonoBinders mbind
          poly_ids      = map mk_dummy binder_names
          mk_dummy name = case maybeSig tc_ty_sigs name of
        let
          forall_a_a    = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
           binder_names  = collectMonoBinders mbind
          poly_ids      = map mk_dummy binder_names
          mk_dummy name = case maybeSig tc_ty_sigs name of

-                           Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id   -- Signature
-                           Nothing -> mkVanillaId name forall_a_a              -- No signature
+                           Just sig -> tcSigPolyId sig                 -- Signature
+                           Nothing  -> mkLocalId name forall_a_a       -- No signature

        in
        in

-       returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
-    ) $
+       traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)   `thenM_`
+       returnM (EmptyMonoBinds, poly_ids)
+    )                                          $

 
        -- TYPECHECK THE BINDINGS
 
        -- TYPECHECK THE BINDINGS

-    tcMonoBinds mbind tc_ty_sigs is_rec                `thenTc` \ (mbind', lie_req, binder_names, mono_ids) ->
-
-       -- CHECK THAT THE SIGNATURES MATCH
-       -- (must do this before getTyVarsToGen)
-    checkSigMatch top_lvl binder_names mono_ids tc_ty_sigs     `thenTc` \ maybe_sig_theta ->   
-
-       -- IMPROVE the LIE
-       -- Force any unifications dictated by functional dependencies.
-       -- Because unification may happen, it's important that this step
-       -- come before:
-       --   - computing vars over which to quantify
-       --   - zonking the generalized type vars
-    let lie_avail = case maybe_sig_theta of
-                     Nothing      -> emptyLIE
-                     Just (_, la) -> la
-       lie_avail_req = lie_avail `plusLIE` lie_req in
-    tcImprove lie_avail_req                            `thenTc_`
-
-       -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen
-       -- The tyvars_not_to_gen are free in the environment, and hence
-       -- candidates for generalisation, but sometimes the monomorphism
-       -- restriction means we can't generalise them nevertheless
+    getLIE (tcMonoBinds mbind tc_ty_sigs is_rec)       `thenM` \ ((mbind', bndr_names_w_ids), lie_req) ->

     let
     let

-       mono_id_tys = map idType mono_ids
+       (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids)
+       tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids

     in
     in

-    getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
-
-       -- Finally, zonk the generalised type variables to real TyVars
-       -- This commits any unbound kind variables to boxed kind
-       -- I'm a little worried that such a kind variable might be
-       -- free in the environment, but I don't think it's possible for
-       -- this to happen when the type variable is not free in the envt
-       -- (which it isn't).            SLPJ Nov 98
-    mapTc zonkTcTyVarToTyVar (varSetElems tyvars_to_gen)       `thenTc` \ real_tyvars_to_gen_list ->
-    let
-       real_tyvars_to_gen = mkVarSet real_tyvars_to_gen_list
-               -- It's important that the final list 
-               -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
-               -- zonked, *including boxity*, because they'll be included in the forall types of
-               -- the polymorphic Ids, and instances of these Ids will be generated from them.
-               -- 
-               -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass
-               -- real_tyvars_to_gen
-    in
-
-       -- SIMPLIFY THE LIE
-    tcExtendGlobalTyVars tyvars_not_to_gen (
-       let ips = getIPsOfLIE lie_avail_req in
-       if null real_tyvars_to_gen_list && (null ips || not is_unrestricted) then
-               -- No polymorphism, and no IPs, so no need to simplify context
-           returnTc (lie_req, EmptyMonoBinds, [])
-       else
-       case maybe_sig_theta of
-         Nothing ->
-               -- No signatures, so just simplify the lie
-               -- NB: no signatures => no polymorphic recursion, so no
-               -- need to use lie_avail (which will be empty anyway)
-           tcSimplify (text "tcBinds1" <+> ppr binder_names)
-                      real_tyvars_to_gen lie_req       `thenTc` \ (lie_free, dict_binds, lie_bound) ->
-           returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
-
-         Just (sig_theta, lie_avail) ->
-               -- There are signatures, and their context is sig_theta
-               -- Furthermore, lie_avail is an LIE containing the 'method insts'
-               -- for the things bound here
-
-           zonkTcThetaType sig_theta                   `thenNF_Tc` \ sig_theta' ->
-           newDicts SignatureOrigin sig_theta'         `thenNF_Tc` \ (dicts_sig, dict_ids) ->
-               -- It's important that sig_theta is zonked, because
-               -- dict_id is later used to form the type of the polymorphic thing,
-               -- and forall-types must be zonked so far as their bound variables
-               -- are concerned
-
-           let
-               -- The "givens" is the stuff available.  We get that from
-               -- the context of the type signature, BUT ALSO the lie_avail
-               -- so that polymorphic recursion works right (see comments at end of fn)
-               givens = dicts_sig `plusLIE` lie_avail
-           in
-
-               -- Check that the needed dicts can be expressed in
-               -- terms of the signature ones
-           tcAddErrCtxt  (bindSigsCtxt tysig_names) $
-           tcSimplifyAndCheck
-               (ptext SLIT("type signature for") <+> pprQuotedList binder_names)
-               real_tyvars_to_gen givens lie_req       `thenTc` \ (lie_free, dict_binds) ->
-
-           returnTc (lie_free, dict_binds, dict_ids)
-
-    )                                          `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
-
-       -- GET THE FINAL MONO_ID_TYS
-    zonkTcTypes mono_id_tys                    `thenNF_Tc` \ zonked_mono_id_types ->
-
-
-       -- CHECK FOR BOGUS UNPOINTED BINDINGS
-    (if any isUnLiftedType zonked_mono_id_types then
-               -- Unlifted bindings must be non-recursive,
-               -- not top level, and non-polymorphic
-       checkTc (isNotTopLevel top_lvl)
-               (unliftedBindErr "Top-level" mbind)             `thenTc_`
-       checkTc (case is_rec of {Recursive -> False; NonRecursive -> True})
-               (unliftedBindErr "Recursive" mbind)             `thenTc_`
-       checkTc (null real_tyvars_to_gen_list)
-               (unliftedBindErr "Polymorphic" mbind)
-     else
-       returnTc ()
-    )                                                  `thenTc_`
-
-    ASSERT( not (any ((== unboxedTypeKind) . tyVarKind) real_tyvars_to_gen_list) )
-               -- The instCantBeGeneralised stuff in tcSimplify should have
-               -- already raised an error if we're trying to generalise an 
-               -- unboxed tyvar (NB: unboxed tyvars are always introduced 
-               -- along with a class constraint) and it's better done there 
-               -- because we have more precise origin information.
-               -- That's why we just use an ASSERT here.

 
 

-
-        -- BUILD THE POLYMORPHIC RESULT IDs
-    mapNF_Tc zonkId mono_ids           `thenNF_Tc` \ zonked_mono_ids ->
+       -- GENERALISE
+       --      (it seems a bit crude to have to do getLIE twice,
+       --       but I can't see a better way just now)
+    addSrcLoc  (minimum (map getSrcLoc binder_names))          $
+    addErrCtxt (genCtxt binder_names)                          $
+    getLIE (generalise binder_names mbind tau_tvs lie_req tc_ty_sigs)
+                       `thenM` \ ((tc_tyvars_to_gen, dict_binds, dict_ids), lie_free) ->
+
+
+       -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars
+       -- This commits any unbound kind variables to boxed kind, by unification
+       -- It's important that the final quanfified type variables
+       -- are fully zonked, *including boxity*, because they'll be 
+       -- included in the forall types of the polymorphic Ids.
+       -- At calls of these Ids we'll instantiate fresh type variables from
+       -- them, and we use their boxity then.
+    mappM zonkTcTyVarToTyVar tc_tyvars_to_gen  `thenM` \ real_tyvars_to_gen ->
+
+       -- ZONK THE Ids
+       -- It's important that the dict Ids are zonked, including the boxity set
+       -- in the previous step, because they are later used to form the type of 
+       -- the polymorphic thing, and forall-types must be zonked so far as 
+       -- their bound variables are concerned
+    mappM zonkId dict_ids                              `thenM` \ zonked_dict_ids ->
+    mappM zonkId mono_ids                              `thenM` \ zonked_mono_ids ->
+
+       -- BUILD THE POLYMORPHIC RESULT IDs

     let
        exports  = zipWith mk_export binder_names zonked_mono_ids
     let
        exports  = zipWith mk_export binder_names zonked_mono_ids

-       dict_tys = map idType dicts_bound
+       poly_ids = [poly_id | (_, poly_id, _) <- exports]
+       dict_tys = map idType zonked_dict_ids

 
 

-       inlines    = mkNameSet [name | InlineSig name _ loc <- inline_sigs]
-        no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++
-                              [(name, IMustNotBeINLINEd True  phase) | InlineSig   name phase loc <- inline_sigs, maybeToBool phase])
-               -- "INLINE n foo" means inline foo, but not until at least phase n
-               -- "NOINLINE n foo" means don't inline foo until at least phase n, and even 
-               --                  then only if it is small enough etc.
-               -- "NOINLINE foo" means don't inline foo ever, which we signal with a (IMustNotBeINLINEd Nothing)
-               -- See comments in CoreUnfold.blackListed for the Authorised Version
+       inlines    = mkNameSet [name | InlineSig True name _ loc <- sigs]
+                       -- Any INLINE sig (regardless of phase control) 
+                       -- makes the RHS look small
+        inline_phases = listToFM [(name, phase) | InlineSig _ name phase _ <- sigs, 
+                                                 not (isAlwaysActive phase)]
+                       -- Set the IdInfo field to control the inline phase
+                       -- AlwaysActive is the default, so don't bother with them

 
        mk_export binder_name zonked_mono_id
          = (tyvars, 
 
        mk_export binder_name zonked_mono_id
          = (tyvars, 

-            attachNoInlinePrag no_inlines poly_id,
+            attachInlinePhase inline_phases poly_id,

             zonked_mono_id)
          where
            (tyvars, poly_id) = 
                case maybeSig tc_ty_sigs binder_name of
             zonked_mono_id)
          where
            (tyvars, poly_id) = 
                case maybeSig tc_ty_sigs binder_name of

-                 Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) -> 
+                 Just (TySigInfo sig_poly_id sig_tyvars _ _ _ _ _) -> 

                        (sig_tyvars, sig_poly_id)
                        (sig_tyvars, sig_poly_id)

-                 Nothing -> (real_tyvars_to_gen_list, new_poly_id)
+                 Nothing -> (real_tyvars_to_gen, new_poly_id)

 
 

-           new_poly_id = mkVanillaId binder_name poly_ty
-           poly_ty = mkForAllTys real_tyvars_to_gen_list 
-                       $ mkFunTys dict_tys 
-                       $ idType (zonked_mono_id)
+           new_poly_id = mkLocalId binder_name poly_ty
+           poly_ty = mkForAllTys real_tyvars_to_gen
+                   $ mkFunTys dict_tys 
+                   $ idType zonked_mono_id

                -- It's important to build a fully-zonked poly_ty, because
                -- we'll slurp out its free type variables when extending the
                -- local environment (tcExtendLocalValEnv); if it's not zonked
                -- it appears to have free tyvars that aren't actually free 
                -- at all.
                -- It's important to build a fully-zonked poly_ty, because
                -- we'll slurp out its free type variables when extending the
                -- local environment (tcExtendLocalValEnv); if it's not zonked
                -- it appears to have free tyvars that aren't actually free 
                -- at all.

-       
-       pat_binders :: [Name]
-       pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds)

     in
     in

-       -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS
-    mapTc (\id -> checkTc (not (idName id `elem` pat_binders
-                               && isUnboxedType (idType id)))
-                         (unboxedPatBindErr id)) zonked_mono_ids
-                               `thenTc_`
-
-        -- BUILD RESULTS
-    returnTc (
-        -- pprTrace "binding.." (ppr ((dicts_bound, dict_binds), exports, [idType poly_id | (_, poly_id, _) <- exports])) $
-        AbsBinds real_tyvars_to_gen_list
-                 dicts_bound
-                 exports
-                 inlines
-                 (dict_binds `andMonoBinds` mbind'),
-        lie_free,
-        [poly_id | (_, poly_id, _) <- exports]
-    )
-  where
-    tysig_names     = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs]
-    is_unrestricted = isUnRestrictedGroup tysig_names mbind

 
 

-justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds
-justPatBindings (AndMonoBinds b1 b2) binds = 
-       justPatBindings b1 (justPatBindings b2 binds) 
-justPatBindings other_bind binds = binds
+    traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
+                                     exports, map idType poly_ids)) `thenM_`

 
 

-attachNoInlinePrag no_inlines bndr
-  = case lookupFM no_inlines (idName bndr) of
+       -- Check for an unlifted, non-overloaded group
+       -- In that case we must make extra checks
+    if any (isUnLiftedType . idType) zonked_mono_ids && null zonked_dict_ids 
+    then       -- Some bindings are unlifted
+       checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind      `thenM_` 
+       
+       extendLIEs lie_req                      `thenM_`
+       returnM (
+           AbsBinds [] [] exports inlines mbind',
+               -- Do not generate even any x=y bindings
+           poly_ids
+        )
+
+    else       -- The normal case
+    extendLIEs lie_free                                `thenM_`
+    returnM (
+       AbsBinds real_tyvars_to_gen
+                zonked_dict_ids
+                exports
+                inlines
+                (dict_binds `andMonoBinds` mbind'),
+       poly_ids
+    )
+
+attachInlinePhase inline_phases bndr
+  = case lookupFM inline_phases (idName bndr) of

        Just prag -> bndr `setInlinePragma` prag
        Nothing   -> bndr
        Just prag -> bndr `setInlinePragma` prag
        Nothing   -> bndr

+
+-- Check that non-overloaded unlifted bindings are
+--     a) non-recursive,
+--     b) not top level, 
+--     c) non-polymorphic
+--     d) not a multiple-binding group (more or less implied by (a))
+
+checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind
+  = ASSERT( not (any ((eqKind unliftedTypeKind) . tyVarKind) real_tyvars_to_gen) )
+               -- The instCantBeGeneralised stuff in tcSimplify should have
+               -- already raised an error if we're trying to generalise an 
+               -- unboxed tyvar (NB: unboxed tyvars are always introduced 
+               -- along with a class constraint) and it's better done there 
+               -- because we have more precise origin information.
+               -- That's why we just use an ASSERT here.
+
+    checkTc (isNotTopLevel top_lvl)
+           (unliftedBindErr "Top-level" mbind)         `thenM_`
+    checkTc (isNonRec is_rec)
+           (unliftedBindErr "Recursive" mbind)         `thenM_`
+    checkTc (single_bind mbind)
+           (unliftedBindErr "Multiple" mbind)          `thenM_`
+    checkTc (null real_tyvars_to_gen)
+           (unliftedBindErr "Polymorphic" mbind)
+
+  where
+    single_bind (PatMonoBind _ _ _)   = True
+    single_bind (FunMonoBind _ _ _ _) = True
+    single_bind other                = False

 \end{code}
 
 \end{code}
 

+

 Polymorphic recursion
 ~~~~~~~~~~~~~~~~~~~~~
 The game plan for polymorphic recursion in the code above is 
 Polymorphic recursion
 ~~~~~~~~~~~~~~~~~~~~~
 The game plan for polymorphic recursion in the code above is 

@@ -502,6 +446,109 @@ is doing.
 %*                                                                     *
 %************************************************************************
 
 %*                                                                     *
 %************************************************************************
 

+\begin{code}
+generalise binder_names mbind tau_tvs lie_req sigs =
+
+  -- check for -fno-monomorphism-restriction
+  doptM Opt_NoMonomorphismRestriction          `thenM` \ no_MR ->
+  let is_unrestricted | no_MR    = True
+                     | otherwise = isUnRestrictedGroup tysig_names mbind
+  in
+
+  if not is_unrestricted then  -- RESTRICTED CASE
+       -- Check signature contexts are empty 
+    checkTc (all is_mono_sig sigs)
+           (restrictedBindCtxtErr binder_names)        `thenM_`
+
+       -- Now simplify with exactly that set of tyvars
+       -- We have to squash those Methods
+    tcSimplifyRestricted doc tau_tvs lie_req           `thenM` \ (qtvs, binds) ->
+
+       -- Check that signature type variables are OK
+    checkSigsTyVars qtvs sigs                          `thenM` \ final_qtvs ->
+
+    returnM (final_qtvs, binds, [])
+
+  else if null sigs then       -- UNRESTRICTED CASE, NO TYPE SIGS
+    tcSimplifyInfer doc tau_tvs lie_req
+
+  else                                 -- UNRESTRICTED CASE, WITH TYPE SIGS
+       -- CHECKING CASE: Unrestricted group, there are type signatures
+       -- Check signature contexts are identical
+    checkSigsCtxts sigs                        `thenM` \ (sig_avails, sig_dicts) ->
+    
+       -- Check that the needed dicts can be
+       -- expressed in terms of the signature ones
+    tcSimplifyInferCheck doc tau_tvs sig_avails lie_req        `thenM` \ (forall_tvs, dict_binds) ->
+       
+       -- Check that signature type variables are OK
+    checkSigsTyVars forall_tvs sigs                    `thenM` \ final_qtvs ->
+
+    returnM (final_qtvs, dict_binds, sig_dicts)
+
+  where
+    tysig_names = map (idName . tcSigPolyId) sigs
+    is_mono_sig (TySigInfo _ _ theta _ _ _ _) = null theta
+
+    doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names
+
+-----------------------
+       -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE
+       -- The type signatures on a mutually-recursive group of definitions
+       -- must all have the same context (or none).
+       --
+       -- We unify them because, with polymorphic recursion, their types
+       -- might not otherwise be related.  This is a rather subtle issue.
+       -- ToDo: amplify
+checkSigsCtxts sigs@(TySigInfo id1 sig_tvs theta1 _ _ _ src_loc : other_sigs)
+  = addSrcLoc src_loc                  $
+    mappM_ check_one other_sigs                `thenM_` 
+    if null theta1 then
+       returnM ([], [])                -- Non-overloaded type signatures
+    else
+    newDicts SignatureOrigin theta1    `thenM` \ sig_dicts ->
+    let
+       -- The "sig_avails" is the stuff available.  We get that from
+       -- the context of the type signature, BUT ALSO the lie_avail
+       -- so that polymorphic recursion works right (see comments at end of fn)
+       sig_avails = sig_dicts ++ sig_meths
+    in
+    returnM (sig_avails, map instToId sig_dicts)
+  where
+    sig1_dict_tys = map mkPredTy theta1
+    sig_meths    = concat [insts | TySigInfo _ _ _ _ _ insts _ <- sigs]
+
+    check_one sig@(TySigInfo id _ theta _ _ _ _)
+       = addErrCtxt (sigContextsCtxt id1 id)                   $
+        checkTc (equalLength theta theta1) sigContextsErr      `thenM_`
+        unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
+
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs 
+  = mappM check_one sigs       `thenM` \ sig_tvs_s ->
+    let
+       -- Sigh.  Make sure that all the tyvars in the type sigs
+       -- appear in the returned ty var list, which is what we are
+       -- going to generalise over.  Reason: we occasionally get
+       -- silly types like
+       --      type T a = () -> ()
+       --      f :: T a
+       --      f () = ()
+       -- Here, 'a' won't appear in qtvs, so we have to add it
+
+       sig_tvs = foldr (unionVarSet . mkVarSet) emptyVarSet sig_tvs_s
+       all_tvs = mkVarSet qtvs `unionVarSet` sig_tvs
+    in
+    returnM (varSetElems all_tvs)
+  where
+    check_one (TySigInfo id sig_tyvars sig_theta sig_tau _ _ src_loc)
+      = addSrcLoc src_loc                                              $
+       addErrCtxt (ptext SLIT("When checking the type signature for") 
+                     <+> quotes (ppr id))                              $
+       addErrCtxtM (sigCtxt id sig_tyvars sig_theta sig_tau)           $
+       checkSigTyVarsWrt (idFreeTyVars id) sig_tyvars
+\end{code}
+

 @getTyVarsToGen@ decides what type variables to generalise over.
 
 For a "restricted group" -- see the monomorphism restriction
 @getTyVarsToGen@ decides what type variables to generalise over.
 
 For a "restricted group" -- see the monomorphism restriction

@@ -530,6 +577,8 @@ generalise.  We must be careful about doing this:
        Another, more common, example is when there's a Method inst in
        the LIE, whose type might very well involve non-overloaded
        type variables.
        Another, more common, example is when there's a Method inst in
        the LIE, whose type might very well involve non-overloaded
        type variables.

+  [NOTE: Jan 2001: I don't understand the problem here so I'm doing 
+       the simple thing instead]

 
  (b) On the other hand, we mustn't generalise tyvars which are constrained,
        because we are going to pass on out the unmodified LIE, with those
 
  (b) On the other hand, we mustn't generalise tyvars which are constrained,
        because we are going to pass on out the unmodified LIE, with those

@@ -540,43 +589,6 @@ constrained tyvars. We don't use any of the results, except to
 find which tyvars are constrained.
 
 \begin{code}
 find which tyvars are constrained.
 
 \begin{code}

-getTyVarsToGen is_unrestricted mono_id_tys lie
-  = tcGetGlobalTyVars                  `thenNF_Tc` \ free_tyvars ->
-    zonkTcTypes mono_id_tys            `thenNF_Tc` \ zonked_mono_id_tys ->
-    let
-       body_tyvars = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars
-       fds         = getAllFunDepsOfLIE lie
-    in
-    if is_unrestricted
-    then
-         -- We need to augment the type variables that appear explicitly in
-         -- the type by those that are determined by the functional dependencies.
-         -- e.g. suppose our type is   C a b => a -> a
-         --    with the fun-dep  a->b
-         -- Then we should generalise over b too; otherwise it will be
-         -- reported as ambiguous.
-       zonkFunDeps fds         `thenNF_Tc` \ fds' ->
-       let tvFundep        = tyVarFunDep fds'
-           extended_tyvars = oclose tvFundep body_tyvars
-       in
-       returnNF_Tc (emptyVarSet, extended_tyvars)
-    else
-       -- This recover and discard-errs is to avoid duplicate error
-       -- messages; this, after all, is an "extra" call to tcSimplify
-       recoverNF_Tc (returnNF_Tc (emptyVarSet, body_tyvars))           $
-       discardErrsTc                                                   $
-
-       tcSimplify (text "getTVG") body_tyvars lie    `thenTc` \ (_, _, constrained_dicts) ->
-       let
-         -- ASSERT: dicts_sig is already zonked!
-           constrained_tyvars    = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts
-           reduced_tyvars_to_gen = body_tyvars `minusVarSet` constrained_tyvars
-        in
-        returnTc (constrained_tyvars, reduced_tyvars_to_gen)
-\end{code}
-
-
-\begin{code}

 isUnRestrictedGroup :: [Name]          -- Signatures given for these
                    -> RenamedMonoBinds
                    -> Bool
 isUnRestrictedGroup :: [Name]          -- Signatures given for these
                    -> RenamedMonoBinds
                    -> Bool

@@ -585,14 +597,14 @@ is_elem v vs = isIn "isUnResMono" v vs
 
 isUnRestrictedGroup sigs (PatMonoBind other        _ _) = False
 isUnRestrictedGroup sigs (VarMonoBind v _)             = v `is_elem` sigs
 
 isUnRestrictedGroup sigs (PatMonoBind other        _ _) = False
 isUnRestrictedGroup sigs (VarMonoBind v _)             = v `is_elem` sigs

-isUnRestrictedGroup sigs (FunMonoBind v _ matches _)   = any isUnRestrictedMatch matches || 
+isUnRestrictedGroup sigs (FunMonoBind v _ matches _)   = isUnRestrictedMatch matches || 

                                                          v `is_elem` sigs
 isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2)                = isUnRestrictedGroup sigs mb1 &&
                                                          isUnRestrictedGroup sigs mb2
 isUnRestrictedGroup sigs EmptyMonoBinds                        = True
 
                                                          v `is_elem` sigs
 isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2)                = isUnRestrictedGroup sigs mb1 &&
                                                          isUnRestrictedGroup sigs mb2
 isUnRestrictedGroup sigs EmptyMonoBinds                        = True
 

-isUnRestrictedMatch (Match _ [] Nothing _) = False     -- No args, no signature
-isUnRestrictedMatch other                 = True       -- Some args or a signature
+isUnRestrictedMatch (Match [] _ _ : _) = False -- No args => like a pattern binding
+isUnRestrictedMatch other             = True   -- Some args => a function binding

 \end{code}
 
 
 \end{code}
 
 

@@ -607,219 +619,129 @@ The signatures have been dealt with already.
 
 \begin{code}
 tcMonoBinds :: RenamedMonoBinds 
 
 \begin{code}
 tcMonoBinds :: RenamedMonoBinds 

-           -> [TcSigInfo]
-           -> RecFlag
+           -> [TcSigInfo] -> RecFlag

            -> TcM (TcMonoBinds, 
            -> TcM (TcMonoBinds, 

-                     LIE,              -- LIE required
-                     [Name],           -- Bound names
-                     [TcId])   -- Corresponding monomorphic bound things
+                   Bag (Name,          -- Bound names
+                        TcId))         -- Corresponding monomorphic bound things

 
 tcMonoBinds mbinds tc_ty_sigs is_rec
 
 tcMonoBinds mbinds tc_ty_sigs is_rec

-  = tc_mb_pats mbinds          `thenTc` \ (complete_it, lie_req_pat, 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 && isEmptyBag lie_avail) 
-           (existentialExplode mbinds)                 `thenTc_` 
-
-       -- *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                          `thenTc` \ (mbinds', lie_req_rhss) ->
-
-    returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, 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
   where

-
-       -- This function is used when dealing with a LHS binder; we make a monomorphic
-       -- version of the Id.  We check for type signatures
-    tc_pat_bndr name pat_ty
-       = case maybeSig tc_ty_sigs name of
-           Nothing
-               -> newLocalId (getOccName name) pat_ty (getSrcLoc name)
-
-           Just (TySigInfo _ _ _ _ _ mono_id _ _)
-               -> tcAddSrcLoc (getSrcLoc name)                         $
-                  unifyTauTy (idType mono_id) pat_ty   `thenTc_`
-                  returnTc mono_id
-
-    mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of
-                               Nothing                                   -> (name, mono_id)
-                               Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id)
-
-    tc_mb_pats EmptyMonoBinds
-      = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
+    tc_mb_pats EmptyMonoBinds 
+      = returnM (returnM (EmptyMonoBinds, emptyBag), emptyBag)

 
     tc_mb_pats (AndMonoBinds mb1 mb2)
 
     tc_mb_pats (AndMonoBinds mb1 mb2)

-      = tc_mb_pats mb1         `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) ->
-        tc_mb_pats mb2         `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) ->
+      = tc_mb_pats mb1         `thenM` \ (complete_it1, xve1) ->
+        tc_mb_pats mb2         `thenM` \ (complete_it2, xve2) ->

        let
        let

-          complete_it xve = complete_it1 xve   `thenTc` \ (mb1', lie1) ->
-                            complete_it2 xve   `thenTc` \ (mb2', lie2) ->
-                            returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2)
+          complete_it = complete_it1   `thenM` \ (mb1', bs1) ->
+                        complete_it2   `thenM` \ (mb2', bs2) ->
+                        returnM (AndMonoBinds mb1' mb2', bs1 `unionBags` bs2)

        in
        in

-       returnTc (complete_it,
-                 lie_req1 `plusLIE` lie_req2,
-                 tvs1 `unionBags` tvs2,
-                 ids1 `unionBags` ids2,
-                 lie_avail1 `plusLIE` lie_avail2)
+       returnM (complete_it, xve1 `unionBags` xve2)

 
     tc_mb_pats (FunMonoBind name inf matches locn)
 
     tc_mb_pats (FunMonoBind name inf matches locn)

-      = newTyVarTy kind                `thenNF_Tc` \ bndr_ty -> 
-       tc_pat_bndr name bndr_ty        `thenTc` \ 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 matches (Check mono_ty)      `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
        let

-          complete_it xve = tcAddSrcLoc locn                           $
-                            tcMatchesFun xve name bndr_ty  matches     `thenTc` \ (matches', lie) ->
-                            returnTc (FunMonoBind bndr_id inf matches' locn, lie)
+          mono_id     = mkLocalId mono_name mono_ty
+          complete_it = addSrcLoc locn                                 $
+                        tcMatchesFun name matches (Check mono_ty)      `thenM` \ matches' ->
+                        returnM (FunMonoBind mono_id inf matches' locn, 
+                                 unitBag (name, mono_id))

        in
        in

-       returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
-
+       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                                $
+                 newHole                                       `thenM` \ hole -> 
+                 tcMatchesFun name matches (Infer hole)        `thenM` \ matches' ->
+                 readMutVar hole                               `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)
     tc_mb_pats bind@(PatMonoBind pat grhss locn)

-      = tcAddSrcLoc locn               $
-       newTyVarTy kind                 `thenNF_Tc` \ pat_ty -> 
+      = addSrcLoc locn         $

 
                --      Now typecheck the pattern
 
                --      Now typecheck the pattern

-               -- We don't support binding fresh type variables in the
-               -- pattern of a pattern binding.  For example, this is illegal:
+               -- We do now support binding fresh (not-already-in-scope) scoped 
+               -- type variables in the pattern of a pattern binding.  
+               -- For example, this is now legal:

                --      (x::a, y::b) = e
                --      (x::a, y::b) = e

-               -- whereas this is ok
-               --      (x::Int, y::Bool) = e
-               --
-               -- We don't check explicitly for this problem.  Instead, we simply
-               -- type check the pattern with tcPat.  If the pattern mentions any
-               -- fresh tyvars we simply get an out-of-scope type variable error
-       tcPat tc_pat_bndr pat pat_ty            `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
-       let
-          complete_it xve = tcAddSrcLoc locn                           $
-                            tcAddErrCtxt (patMonoBindsCtxt bind)       $
-                            tcExtendLocalValEnv xve                    $
-                            tcGRHSs grhss pat_ty PatBindRhs            `thenTc` \ (grhss', lie) ->
-                            returnTc (PatMonoBind pat' grhss' locn, lie)
-       in
-       returnTc (complete_it, lie_req, tvs, ids, lie_avail)
+               -- The type variables are brought into scope in tc_binds_and_then,
+               -- so we don't have to do anything here.

 
 

-       -- Figure out the appropriate kind for the pattern,
-       -- and generate a suitable type variable 
-    kind = case is_rec of
-               Recursive    -> boxedTypeKind   -- Recursive, so no unboxed types
-               NonRecursive -> openTypeKind    -- Non-recursive, so we permit unboxed types
-\end{code}
-
-%************************************************************************
-%*                                                                     *
-\subsection{Signatures}
-%*                                                                     *
-%************************************************************************
-
-@checkSigMatch@ does the next step in checking signature matching.
-The tau-type part has already been unified.  What we do here is to
-check that this unification has not over-constrained the (polymorphic)
-type variables of the original signature type.
-
-The error message here is somewhat unsatisfactory, but it'll do for
-now (ToDo).
-
-\begin{code}
-checkSigMatch :: TopLevelFlag -> [Name] -> [TcId] -> [TcSigInfo] -> TcM (Maybe (TcThetaType, LIE))
-checkSigMatch top_lvl binder_names mono_ids sigs
-  | main_bound_here
-  =    -- First unify the main_id with IO t, for any old t
-    tcSetErrCtxt mainTyCheckCtxt (
-       tcLookupTyCon ioTyConName               `thenTc`    \ ioTyCon ->
-       newTyVarTy boxedTypeKind                `thenNF_Tc` \ t_tv ->
-       unifyTauTy ((mkTyConApp ioTyCon [t_tv]))
-                  (idType main_mono_id)
-    )                                          `thenTc_`
-
-       -- Now check the signatures
-       -- Must do this after the unification with IO t, 
-       -- in case of a silly signature like
-       --      main :: forall a. a
-       -- The unification to IO t will bind the type variable 'a',
-       -- which is just waht check_one_sig looks for
-    mapTc check_one_sig sigs                   `thenTc_`
-    mapTc check_main_ctxt sigs                 `thenTc_` 
-
-           returnTc (Just ([], emptyLIE))
-
-  | not (null sigs)
-  = mapTc check_one_sig sigs                   `thenTc_`
-    mapTc check_one_ctxt all_sigs_but_first    `thenTc_`
-    returnTc (Just (theta1, sig_lie))
-
-  | otherwise
-  = returnTc Nothing           -- No constraints from type sigs
-
-  where
-    (TySigInfo _ id1 _ theta1 _ _ _ _ : all_sigs_but_first) = sigs
-
-    sig1_dict_tys      = mk_dict_tys theta1
-    n_sig1_dict_tys    = length sig1_dict_tys
-    sig_lie            = mkLIE (concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs])
-
-    maybe_main        = find_main top_lvl binder_names mono_ids
-    main_bound_here   = maybeToBool maybe_main
-    Just main_mono_id = maybe_main
-                     
-       -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK
-       -- Doesn't affect substitution
-    check_one_sig (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc)
-      = tcAddSrcLoc src_loc                                    $
-       tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau)       $
-       checkSigTyVars sig_tyvars (idFreeTyVars id)
+       newHole                                 `thenM` \ hole -> 
+       tcPat tc_pat_bndr pat (Infer hole)      `thenM` \ (pat', tvs, ids, lie_avail) ->
+       readMutVar hole                         `thenM` \ pat_ty ->

 
 

+       -- Don't know how to deal with pattern-bound existentials yet
+        checkTc (isEmptyBag tvs && null lie_avail) 
+               (existentialExplode bind)       `thenM_` 

 
 

-       -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE
-       -- The type signatures on a mutually-recursive group of definitions
-       -- must all have the same context (or none).
-       --
-       -- We unify them because, with polymorphic recursion, their types
-       -- might not otherwise be related.  This is a rather subtle issue.
-       -- ToDo: amplify
-    check_one_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc)
-       = tcAddSrcLoc src_loc   $
-        tcAddErrCtxt (sigContextsCtxt id1 id) $
-        checkTc (length this_sig_dict_tys == n_sig1_dict_tys)
-                               sigContextsErr          `thenTc_`
-        unifyTauTyLists sig1_dict_tys this_sig_dict_tys
-      where
-        this_sig_dict_tys = mk_dict_tys theta
-
-       -- CHECK THAT FOR A GROUP INVOLVING Main.main, all 
-       -- the signature contexts are empty (what a bore)
-    check_main_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc)
-       = tcAddSrcLoc src_loc   $
-         checkTc (null theta) (mainContextsErr id)
-
-    mk_dict_tys theta = map mkPredTy theta
-
-    sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id)
-
-       -- Search for Main.main in the binder_names, return corresponding mono_id
-    find_main NotTopLevel binder_names mono_ids = Nothing
-    find_main TopLevel    binder_names mono_ids = go binder_names mono_ids
-    go [] [] = Nothing
-    go (n:ns) (m:ms) | n `hasKey` mainKey = Just m
-                    | otherwise          = go ns ms
+       let
+          complete_it = addSrcLoc locn                                 $
+                        addErrCtxt (patMonoBindsCtxt bind)             $
+                        tcGRHSsPat grhss (Check pat_ty)        `thenM` \ grhss' ->
+                        returnM (PatMonoBind pat' grhss' locn, ids)
+       in
+       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
+       -- as if that type signature had been on the binder as a SigPatIn.
+       -- We check for a type signature; if there is one, we use the mono_id
+       -- from the signature.  This is how we make sure the tau part of the
+       -- signature actually matches the type of the LHS; then tc_mb_pats
+       -- ensures the LHS and RHS have the same type
+       
+    tc_pat_bndr name pat_ty
+       = case maybeSig tc_ty_sigs name of
+           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 ->
+                       returnM (co_fn, mono_id)
+                    where
+                       mono_id = tcSigMonoId sig

 \end{code}
 
 
 \end{code}
 
 

@@ -865,34 +787,37 @@ a RULE now:
        {-# SPECIALISE (f::<type) = g #-}
 
 \begin{code}
        {-# SPECIALISE (f::<type) = g #-}
 
 \begin{code}

-tcSpecSigs :: [RenamedSig] -> TcM (TcMonoBinds, LIE)
+tcSpecSigs :: [RenamedSig] -> TcM TcMonoBinds

 tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
   =    -- SPECIALISE f :: forall b. theta => tau  =  g
 tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
   =    -- SPECIALISE f :: forall b. theta => tau  =  g

-    tcAddSrcLoc src_loc                                $
-    tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
+    addSrcLoc src_loc                          $
+    addErrCtxt (valSpecSigCtxt name poly_ty)   $

 
        -- Get and instantiate its alleged specialised type
 
        -- Get and instantiate its alleged specialised type

-    tcHsSigType poly_ty                                `thenTc` \ sig_ty ->
+    tcHsSigType (FunSigCtxt name) poly_ty      `thenM` \ sig_ty ->

 
        -- Check that f has a more general type, and build a RHS for
        -- the spec-pragma-id at the same time
 
        -- Check that f has a more general type, and build a RHS for
        -- the spec-pragma-id at the same time

-    tcExpr (HsVar name) sig_ty                 `thenTc` \ (spec_expr, spec_lie) ->
+    getLIE (tcCheckSigma (HsVar name) sig_ty)  `thenM` \ (spec_expr, spec_lie) ->

 
        -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
 
        -- Squeeze out any Methods (see comments with tcSimplifyToDicts)

-    tcSimplifyToDicts spec_lie                 `thenTc` \ (spec_lie1, spec_binds) ->
+    tcSimplifyToDicts spec_lie                 `thenM` \ spec_binds ->

 
        -- Just specialise "f" by building a SpecPragmaId binding
        -- It is the thing that makes sure we don't prematurely 
        -- dead-code-eliminate the binding we are really interested in.
 
        -- Just specialise "f" by building a SpecPragmaId binding
        -- It is the thing that makes sure we don't prematurely 
        -- dead-code-eliminate the binding we are really interested in.

-    newSpecPragmaId name sig_ty                `thenNF_Tc` \ spec_id ->
+    newLocalName name                  `thenM` \ spec_name ->
+    let
+       spec_bind = VarMonoBind (mkSpecPragmaId spec_name sig_ty)
+                               (mkHsLet spec_binds spec_expr)
+    in

 
        -- Do the rest and combine
 
        -- Do the rest and combine

-    tcSpecSigs sigs                    `thenTc` \ (binds_rest, lie_rest) ->
-    returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr),
-             lie_rest   `plusLIE`      spec_lie1)
+    tcSpecSigs sigs                    `thenM` \ binds_rest ->
+    returnM (binds_rest `andMonoBinds` spec_bind)

 
 tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
 
 tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs

-tcSpecSigs []                = returnTc (EmptyMonoBinds, emptyLIE)
+tcSpecSigs []                = returnM EmptyMonoBinds

 \end{code}
 
 
 \end{code}
 
 

@@ -913,41 +838,37 @@ valSpecSigCtxt v ty
         nest 4 (ppr v <+> dcolon <+> ppr ty)]
 
 -----------------------------------------------
         nest 4 (ppr v <+> dcolon <+> ppr ty)]
 
 -----------------------------------------------

-unboxedPatBindErr id
-  = ptext SLIT("variable in a lazy pattern binding has unboxed type: ")
-        <+> quotes (ppr id)
-
------------------------------------------------
-bindSigsCtxt ids
-  = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
-
------------------------------------------------
-sigContextsErr
-  = ptext SLIT("Mismatched contexts")
+sigContextsErr = ptext SLIT("Mismatched contexts")

 
 sigContextsCtxt s1 s2
 
 sigContextsCtxt s1 s2

-  = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"), 
-               quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)])
-        4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)"))
-
-mainContextsErr id
-  | id `hasKey` mainKey = ptext SLIT("Main.main cannot be overloaded")
-  | otherwise
-  = quotes (ppr id) <+> ptext SLIT("cannot be overloaded") <> char ',' <> -- sigh; workaround for cpp's inability to deal
-    ptext SLIT("because it is mutually recursive with Main.main")         -- with commas inside SLIT strings.
-
-mainTyCheckCtxt
-  = hsep [ptext SLIT("When checking that"), quotes (ptext SLIT("main")),
-         ptext SLIT("has the required type")]
+  = vcat [ptext SLIT("When matching the contexts of the signatures for"), 
+         nest 2 (vcat [ppr s1 <+> dcolon <+> ppr (idType s1),
+                       ppr s2 <+> dcolon <+> ppr (idType s2)]),
+         ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]

 
 -----------------------------------------------
 unliftedBindErr flavour mbind
 
 -----------------------------------------------
 unliftedBindErr flavour mbind

-  = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed"))
+  = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:"))

         4 (ppr mbind)
 
         4 (ppr mbind)
 

+-----------------------------------------------

 existentialExplode mbinds
   = hang (vcat [text "My brain just exploded.",
                text "I can't handle pattern bindings for existentially-quantified constructors.",
                text "In the binding group"])
        4 (ppr mbinds)
 existentialExplode mbinds
   = hang (vcat [text "My brain just exploded.",
                text "I can't handle pattern bindings for existentially-quantified constructors.",
                text "In the binding group"])
        4 (ppr mbinds)

+
+-----------------------------------------------
+restrictedBindCtxtErr binder_names
+  = hang (ptext SLIT("Illegal overloaded type signature(s)"))
+       4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
+               ptext SLIT("that falls under the monomorphism restriction")])
+
+genCtxt binder_names
+  = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
+
+-- Used in error messages
+-- Use quotes for a single one; they look a bit "busy" for several
+pprBinders [bndr] = quotes (ppr bndr)
+pprBinders bndrs  = pprWithCommas ppr bndrs

 \end{code}
 \end{code}