minor cleanup; remove one use of fromJust

[ghc-hetmet.git] / ghc / compiler / rename / RnBinds.lhs

diff --git a/ghc/compiler/rename/RnBinds.lhs b/ghc/compiler/rename/RnBinds.lhs
index ced653a..13035e7 100644 (file)
--- a/ghc/compiler/rename/RnBinds.lhs
+++ b/ghc/compiler/rename/RnBinds.lhs
@@ -1,5 +1,5 @@
 %
 %

-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998

 %
 \section[RnBinds]{Renaming and dependency analysis of bindings}
 
 %
 \section[RnBinds]{Renaming and dependency analysis of bindings}
 

@@ -9,37 +9,44 @@ type-synonym declarations; those cannot be done at this stage because
 they may be affected by renaming (which isn't fully worked out yet).
 
 \begin{code}
 they may be affected by renaming (which isn't fully worked out yet).
 
 \begin{code}

-#include "HsVersions.h"
-

 module RnBinds (
 module RnBinds (

-       rnTopBinds,
-       rnMethodBinds,
-       rnBinds,
-       SYN_IE(FreeVars),
-       SYN_IE(DefinedVars)
+       rnTopBinds, 
+       rnLocalBindsAndThen, rnValBindsAndThen, rnValBinds, trimWith,
+       rnMethodBinds, renameSigs, 
+       rnMatchGroup, rnGRHSs

    ) where
 
    ) where
 

-IMP_Ubiq()
-IMPORT_DELOOPER(RnLoop)                -- break the RnPass/RnExpr/RnBinds loops
+#include "HsVersions.h"
+
+import {-# SOURCE #-} RnExpr( rnLExpr, rnStmts )

 
 import HsSyn
 
 import HsSyn

-import HsPragmas       ( isNoGenPragmas, noGenPragmas )

 import RdrHsSyn
 import RnHsSyn
 import RdrHsSyn
 import RnHsSyn

-import RnMonad
-import RnExpr          ( rnMatch, rnGRHSsAndBinds, rnPat, checkPrecMatch )
-
-import CmdLineOpts     ( opt_SigsRequired )
-import Digraph         ( stronglyConnComp )
-import ErrUtils                ( addErrLoc, addShortErrLocLine )
-import Name            ( getLocalName, RdrName )
-import Maybes          ( catMaybes )
---import PprStyle--ToDo:rm
-import Pretty
-import UniqSet         ( emptyUniqSet, unitUniqSet, mkUniqSet,
-                         unionUniqSets, unionManyUniqSets,
-                         elementOfUniqSet, uniqSetToList, SYN_IE(UniqSet) )
-import Util            ( thenCmp, isIn, removeDups, panic, panic#, assertPanic )
+import TcRnMonad
+import RnTypes         ( rnHsSigType, rnLHsType, rnHsTypeFVs, 
+                         rnLPat, rnPatsAndThen, patSigErr, checkPrecMatch )
+import RnEnv           ( bindLocatedLocalsRn, lookupLocatedBndrRn, 
+                         lookupLocatedInstDeclBndr, newIPNameRn,
+                         lookupLocatedSigOccRn, bindPatSigTyVars, bindPatSigTyVarsFV,
+                         bindLocalFixities, bindSigTyVarsFV, 
+                         warnUnusedLocalBinds, mapFvRn, extendTyVarEnvFVRn,
+                       )
+import DynFlags        ( DynFlag(..) )
+import Name            ( Name, nameOccName, nameSrcLoc )
+import NameEnv
+import NameSet
+import PrelNames       ( isUnboundName )
+import RdrName         ( RdrName, rdrNameOcc )
+import SrcLoc          ( mkSrcSpan, Located(..), unLoc )
+import ListSetOps      ( findDupsEq )
+import BasicTypes      ( RecFlag(..) )
+import Digraph         ( SCC(..), stronglyConnComp )
+import Bag
+import Outputable
+import Maybes          ( orElse, isJust )
+import Util            ( filterOut )
+import Monad           ( foldM )

 \end{code}
 
 -- ToDo: Put the annotations into the monad, so that they arrive in the proper
 \end{code}
 
 -- ToDo: Put the annotations into the monad, so that they arrive in the proper

@@ -64,30 +71,17 @@ This is precisely what the function @rnBinds@ does.
 ToDo: deal with case where a single monobinds binds the same variable
 twice.
 
 ToDo: deal with case where a single monobinds binds the same variable
 twice.
 

-Sets of variable names are represented as sets explicitly, rather than lists.
-
-\begin{code}
-type DefinedVars = UniqSet RnName
-type FreeVars    = UniqSet RnName
-\end{code}
-
-i.e., binders.
-

 The vertag tag is a unique @Int@; the tags only need to be unique
 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
 (heavy monad machinery not needed).
 
 The vertag tag is a unique @Int@; the tags only need to be unique
 within one @MonoBinds@, so that unique-Int plumbing is done explicitly
 (heavy monad machinery not needed).
 

-\begin{code}
-type VertexTag = Int
-type Cycle     = [VertexTag]
-type Edge      = (VertexTag, VertexTag)
-\end{code}

 
 %************************************************************************
 %*                                                                     *
 %* naming conventions                                                  *
 %*                                                                     *
 %************************************************************************
 
 %************************************************************************
 %*                                                                     *
 %* naming conventions                                                  *
 %*                                                                     *
 %************************************************************************

+

 \subsection[name-conventions]{Name conventions}
 
 The basic algorithm involves walking over the tree and returning a tuple
 \subsection[name-conventions]{Name conventions}
 
 The basic algorithm involves walking over the tree and returning a tuple

@@ -111,9 +105,10 @@ a set of variables free in @Exp@ is written @fvExp@
 
 %************************************************************************
 %*                                                                     *
 
 %************************************************************************
 %*                                                                     *

-%* analysing polymorphic bindings (HsBinds, Bind, MonoBinds)           *
+%* analysing polymorphic bindings (HsBindGroup, HsBind)

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

+

 \subsubsection[dep-HsBinds]{Polymorphic bindings}
 
 Non-recursive expressions are reconstructed without any changes at top
 \subsubsection[dep-HsBinds]{Polymorphic bindings}
 
 Non-recursive expressions are reconstructed without any changes at top

@@ -122,7 +117,7 @@ However, non-recursive expressions are currently not expected as
 \Haskell{} programs, and this code should not be executed.
 
 Monomorphic bindings contain information that is returned in a tuple
 \Haskell{} programs, and this code should not be executed.
 
 Monomorphic bindings contain information that is returned in a tuple

-(a @FlatMonoBindsInfo@) containing:
+(a @FlatMonoBinds@) containing:

 
 \begin{enumerate}
 \item
 
 \begin{enumerate}
 \item

@@ -154,494 +149,474 @@ instance declarations.  It expects only to see @FunMonoBind@s, and
 it expects the global environment to contain bindings for the binders
 (which are all class operations).
 
 it expects the global environment to contain bindings for the binders
 (which are all class operations).
 

-\begin{code}
-rnTopBinds    :: RdrNameHsBinds -> RnM_Fixes s RenamedHsBinds
-rnMethodBinds :: RnName{-class-} -> RdrNameMonoBinds -> RnM_Fixes s RenamedMonoBinds
-rnBinds              :: RdrNameHsBinds -> RnM_Fixes s (RenamedHsBinds, FreeVars, [RnName])
-
-rnTopBinds EmptyBinds                     = returnRn EmptyBinds
-rnTopBinds (SingleBind (RecBind bind))    = rnTopMonoBinds bind []
-rnTopBinds (BindWith (RecBind bind) sigs) = rnTopMonoBinds bind sigs
-  -- the parser doesn't produce other forms
-
--- ********************************************************************
-
-rnMethodBinds class_name EmptyMonoBinds = returnRn EmptyMonoBinds
+%************************************************************************
+%*                                                                     *
+\subsubsection{ Top-level bindings}
+%*                                                                     *
+%************************************************************************

 
 

-rnMethodBinds class_name (AndMonoBinds mb1 mb2)
-  = andRn AndMonoBinds (rnMethodBinds class_name mb1)
-                      (rnMethodBinds class_name mb2)
+@rnTopMonoBinds@ assumes that the environment already
+contains bindings for the binders of this particular binding.

 
 

-rnMethodBinds class_name (FunMonoBind occname inf matches locn)
-  = pushSrcLocRn locn                             $
-    lookupClassOp class_name occname              `thenRn` \ op_name ->
-    mapAndUnzipRn rnMatch matches                 `thenRn` \ (new_matches, _) ->
-    mapRn (checkPrecMatch inf op_name) new_matches `thenRn_`
-    returnRn (FunMonoBind op_name inf new_matches locn)
+\begin{code}
+rnTopBinds :: HsValBinds RdrName -> RnM (HsValBinds Name, DefUses)
+
+-- The binders of the binding are in scope already;
+-- the top level scope resolution does that
+
+rnTopBinds binds
+ =  do { is_boot <- tcIsHsBoot
+       ; if is_boot then rnTopBindsBoot binds
+                    else rnTopBindsSrc  binds }
+
+rnTopBindsBoot :: HsValBinds RdrName -> RnM (HsValBinds Name, DefUses)
+-- A hs-boot file has no bindings. 
+-- Return a single HsBindGroup with empty binds and renamed signatures
+rnTopBindsBoot (ValBindsIn mbinds sigs)
+  = do { checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
+       ; sigs' <- renameSigs okHsBootSig sigs
+       ; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
+
+rnTopBindsSrc :: HsValBinds RdrName -> RnM (HsValBinds Name, DefUses)
+rnTopBindsSrc binds@(ValBindsIn mbinds _)
+  = do { (binds', dus) <- rnValBinds noTrim binds
+
+               -- Warn about missing signatures, 
+       ; let   { ValBindsOut _ sigs' = binds'
+               ; ty_sig_vars = mkNameSet [ unLoc n | L _ (TypeSig n _) <- sigs']
+               ; un_sigd_bndrs = duDefs dus `minusNameSet` ty_sig_vars }
+
+       ; warn_missing_sigs <- doptM Opt_WarnMissingSigs
+       ; ifM (warn_missing_sigs)
+             (mappM_ missingSigWarn (nameSetToList un_sigd_bndrs))
+
+       ; return (binds', dus)
+       }
+\end{code}

 
 

-rnMethodBinds class_name (PatMonoBind (VarPatIn occname) grhss_and_binds locn)
-  = pushSrcLocRn locn                  $
-    lookupClassOp class_name occname   `thenRn` \ op_name ->
-    rnGRHSsAndBinds grhss_and_binds    `thenRn` \ (grhss_and_binds', _) ->
-    returnRn (PatMonoBind (VarPatIn op_name) grhss_and_binds' locn)

 
 

--- Can't handle method pattern-bindings which bind multiple methods.
-rnMethodBinds _ mbind@(PatMonoBind other_pat _ locn)
-  = failButContinueRn EmptyMonoBinds (methodBindErr mbind locn)

 
 

--- ********************************************************************
+%*********************************************************
+%*                                                     *
+               HsLocalBinds
+%*                                                     *
+%*********************************************************

 
 

-rnBinds EmptyBinds                     = returnRn (EmptyBinds,emptyUniqSet,[])
-rnBinds (SingleBind (RecBind bind))    = rnNestedMonoBinds bind []
-rnBinds (BindWith (RecBind bind) sigs) = rnNestedMonoBinds bind sigs
-  -- the parser doesn't produce other forms
+\begin{code}
+rnLocalBindsAndThen 
+  :: HsLocalBinds RdrName
+  -> (HsLocalBinds Name -> RnM (result, FreeVars))
+  -> RnM (result, FreeVars)
+-- This version (a) assumes that the binding vars are not already in scope
+--             (b) removes the binders from the free vars of the thing inside
+-- The parser doesn't produce ThenBinds
+rnLocalBindsAndThen EmptyLocalBinds thing_inside
+  = thing_inside EmptyLocalBinds
+
+rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
+  = rnValBindsAndThen val_binds $ \ val_binds' -> 
+    thing_inside (HsValBinds val_binds')
+
+rnLocalBindsAndThen (HsIPBinds binds) thing_inside
+  = rnIPBinds binds                    `thenM` \ (binds',fv_binds) ->
+    thing_inside (HsIPBinds binds')    `thenM` \ (thing, fvs_thing) ->
+    returnM (thing, fvs_thing `plusFV` fv_binds)
+
+-------------
+rnIPBinds (IPBinds ip_binds _no_dict_binds)
+  = do { (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
+       ; return (IPBinds ip_binds' emptyLHsBinds, plusFVs fvs_s) }
+
+rnIPBind (IPBind n expr)
+  = newIPNameRn  n             `thenM` \ name ->
+    rnLExpr expr               `thenM` \ (expr',fvExpr) ->
+    return (IPBind name expr', fvExpr)

 \end{code}
 
 \end{code}
 

-@rnNestedMonoBinds@
-       - collects up the binders for this declaration group,
-       - checkes that they form a set
-       - extends the environment to bind them to new local names
-       - calls @rnMonoBinds@ to do the real work

 
 

-In contrast, @rnTopMonoBinds@ doesn't extend the environment, because that's
-already done in pass3. All it does is call @rnMonoBinds@ and discards
-the free var info.
+%************************************************************************
+%*                                                                     *
+               ValBinds
+%*                                                                     *
+%************************************************************************

 
 \begin{code}
 
 \begin{code}

-rnTopMonoBinds :: RdrNameMonoBinds -> [RdrNameSig] -> RnM_Fixes s RenamedHsBinds
+rnValBindsAndThen :: HsValBinds RdrName
+                 -> (HsValBinds Name -> RnM (result, FreeVars))
+                 -> RnM (result, FreeVars)

 
 

-rnTopMonoBinds EmptyMonoBinds sigs = returnRn EmptyBinds
-
-rnTopMonoBinds mbs sigs
- = rnBindSigs True{-top-level-} (collectMonoBinders mbs) sigs `thenRn` \ siglist ->
-   rnMonoBinds mbs siglist `thenRn` \ (new_binds, fv_set) ->
-   returnRn new_binds
+rnValBindsAndThen binds@(ValBindsIn mbinds sigs) thing_inside
+  =    -- Extract all the binders in this group, and extend the
+       -- current scope, inventing new names for the new binders
+       -- This also checks that the names form a set
+    bindLocatedLocalsRn doc mbinders_w_srclocs                 $ \ bndrs ->

 
 

+       -- Then install local fixity declarations
+       -- Notice that they scope over thing_inside too
+    bindLocalFixities [sig | L _ (FixSig sig) <- sigs ]        $

 
 

-rnNestedMonoBinds :: RdrNameMonoBinds -> [RdrNameSig]
-                 -> RnM_Fixes s (RenamedHsBinds, FreeVars, [RnName])
+       -- Do the business
+    rnValBinds (trimWith bndrs) binds  `thenM` \ (binds, bind_dus) ->

 
 

-rnNestedMonoBinds EmptyMonoBinds sigs
-  = returnRn (EmptyBinds, emptyUniqSet, [])
+       -- Now do the "thing inside"
+    thing_inside binds                         `thenM` \ (result,result_fvs) ->

 
 

-rnNestedMonoBinds mbinds sigs  -- Non-empty monobinds
-  =
-       -- Extract all the binders in this group,
-       -- and extend current scope, inventing new names for the new binders
-       -- This also checks that the names form a set
+       -- Final error checking

     let
     let

-       mbinders_w_srclocs = collectMonoBindersAndLocs mbinds
-       mbinders           = map fst mbinders_w_srclocs
+       all_uses = duUses bind_dus `plusFV` result_fvs
+       -- duUses: It's important to return all the uses, not the 'real uses' 
+       -- used for warning about unused bindings.  Otherwise consider:
+       --      x = 3
+       --      y = let p = x in 'x'    -- NB: p not used
+       -- If we don't "see" the dependency of 'y' on 'x', we may put the
+       -- bindings in the wrong order, and the type checker will complain
+       -- that x isn't in scope
+
+       unused_bndrs = [ b | b <- bndrs, not (b `elemNameSet` all_uses)]

     in
     in

-    newLocalNames "variable"
-                 mbinders_w_srclocs    `thenRn` \ new_mbinders ->
-
-    extendSS2 new_mbinders (
-        rnBindSigs False{-not top- level-} mbinders sigs `thenRn` \ siglist ->
-        rnMonoBinds mbinds  siglist
-    )                                  `thenRn` \ (new_binds, fv_set) ->
-    returnRn (new_binds, fv_set, new_mbinders)
-\end{code}
+    warnUnusedLocalBinds unused_bndrs  `thenM_`

 
 

-@rnMonoBinds@ is used by *both* top-level and nested bindings.  It
-assumes that all variables bound in this group are already in scope.
-This is done *either* by pass 3 (for the top-level bindings),
-*or* by @rnNestedMonoBinds@ (for the nested ones).
+    returnM (result, delListFromNameSet all_uses bndrs)
+  where
+    mbinders_w_srclocs = collectHsBindLocatedBinders mbinds
+    doc = text "In the binding group for:"
+         <+> pprWithCommas ppr (map unLoc mbinders_w_srclocs)

 
 

-\begin{code}
-rnMonoBinds :: RdrNameMonoBinds
-           -> [RenamedSig]     -- Signatures attached to this group
-           -> RnM_Fixes s (RenamedHsBinds, FreeVars)
+---------------------
+rnValBinds :: (FreeVars -> FreeVars)
+          -> HsValBinds RdrName
+          -> RnM (HsValBinds Name, DefUses)
+-- Assumes the binders of the binding are in scope already

 
 

-rnMonoBinds mbinds siglist
-  =
-        -- Rename the bindings, returning a MonoBindsInfo
-        -- which is a list of indivisible vertices so far as
-        -- the strongly-connected-components (SCC) analysis is concerned
-    flattenMonoBinds 0 siglist mbinds  `thenRn` \ (_, mbinds_info) ->
+rnValBinds trim (ValBindsIn mbinds sigs)
+  = do { sigs' <- rename_sigs sigs

 
 

-        -- Do the SCC analysis
-    let vertices = mkVertices mbinds_info
-       edges   = mkEdges     mbinds_info
+       ; binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs') trim) mbinds

 
 

-       scc_result = stronglyConnComp (==) edges vertices
+       ; let (binds', bind_dus) = depAnalBinds binds_w_dus

 
 

-        -- Deal with bound and free-var calculation
-       rhs_free_vars = foldr f emptyUniqSet mbinds_info
+       -- We do the check-sigs after renaming the bindings,
+       -- so that we have convenient access to the binders
+       ; check_sigs (okBindSig (duDefs bind_dus)) sigs'

 
 

-       final_binds = reconstructRec scc_result edges mbinds_info
+       ; return (ValBindsOut binds' sigs', 
+                 usesOnly (hsSigsFVs sigs') `plusDU` bind_dus) }

 
 

-       happy_answer = returnRn (final_binds, rhs_free_vars)
-    in
-    case (inline_sigs_in_recursive_binds final_binds) of
-      Nothing -> happy_answer
-      Just names_n_locns ->
--- SLPJ: sometimes want recursive INLINE for worker wrapper style stuff
---     addErrRn (inlineInRecursiveBindsErr names_n_locns) `thenRn_`
-       {-not so-}happy_answer
+
+---------------------
+depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
+            -> ([(RecFlag, LHsBinds Name)], DefUses)
+-- Dependency analysis; this is important so that 
+-- unused-binding reporting is accurate
+depAnalBinds binds_w_dus
+  = (map get_binds sccs, map get_du sccs)
+  where
+    sccs = stronglyConnComp edges
+
+    keyd_nodes = bagToList binds_w_dus `zip` [0::Int ..]
+
+    edges = [ (node, key, [key | n <- nameSetToList uses,
+                                Just key <- [lookupNameEnv key_map n] ])
+           | (node@(_,_,uses), key) <- keyd_nodes ]
+
+    key_map :: NameEnv Int     -- Which binding it comes from
+    key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
+                                    , bndr <- bndrs ]
+
+    get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
+    get_binds (CyclicSCC  binds_w_dus)  = (Recursive, listToBag [b | (b,d,u) <- binds_w_dus])
+
+    get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
+    get_du (CyclicSCC  binds_w_dus)      = (Just defs, uses)
+       where
+         defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
+         uses = unionManyNameSets [u | (_,_,u) <- binds_w_dus]
+
+
+---------------------
+-- Bind the top-level forall'd type variables in the sigs.
+-- E.g         f :: a -> a
+--     f = rhs
+--     The 'a' scopes over the rhs
+--
+-- NB: there'll usually be just one (for a function binding)
+--     but if there are many, one may shadow the rest; too bad!
+--     e.g  x :: [a] -> [a]
+--          y :: [(a,a)] -> a
+--          (x,y) = e
+--      In e, 'a' will be in scope, and it'll be the one from 'y'!
+
+mkSigTvFn :: [LSig Name] -> (Name -> [Name])
+-- Return a lookup function that maps an Id Name to the names
+-- of the type variables that should scope over its body..
+mkSigTvFn sigs
+  = \n -> lookupNameEnv env n `orElse` []

   where
   where

-    f :: (a,b, FreeVars, c,d) -> FreeVars -> FreeVars
-
-    f (_, _, fvs_body, _, _) fvs_sofar = fvs_sofar `unionUniqSets` fvs_body
-
-    inline_sigs_in_recursive_binds (BindWith (RecBind _) sigs)
-      = case [(n, locn) | (InlineSig n locn) <- sigs ] of
-         []   -> Nothing
-         sigh ->
-#if OMIT_DEFORESTER
-               Just sigh
-#else
-               -- Allow INLINEd recursive functions if they are
-               -- designated DEFORESTable too.
-               case [(n, locn) | (DeforestSig n locn) <- sigs ] of
-                       []   -> Just sigh
-                       sigh -> Nothing
-#endif
-
-    inline_sigs_in_recursive_binds (ThenBinds b1 b2)
-      = case (inline_sigs_in_recursive_binds b1) of
-         Nothing -> inline_sigs_in_recursive_binds b2
-         Just  x -> Just x -- NB: won't report error(s) in b2
-
-    inline_sigs_in_recursive_binds anything_else = Nothing
+    env :: NameEnv [Name]
+    env = mkNameEnv [ (name, map hsLTyVarName ltvs)
+                   | L _ (TypeSig (L _ name) 
+                                  (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs]
+       -- Note the pattern-match on "Explicit"; we only bind
+       -- type variables from signatures with an explicit top-level for-all
+                               
+-- The trimming function trims the free vars we attach to a
+-- binding so that it stays reasonably small
+noTrim :: FreeVars -> FreeVars
+noTrim fvs = fvs       -- Used at top level
+
+trimWith :: [Name] -> FreeVars -> FreeVars
+-- Nested bindings; trim by intersection with the names bound here
+trimWith bndrs = intersectNameSet (mkNameSet bndrs)
+
+---------------------
+rnBind :: (Name -> [Name])             -- Signature tyvar function
+       -> (FreeVars -> FreeVars)       -- Trimming function for rhs free vars
+       -> LHsBind RdrName
+       -> RnM (LHsBind Name, [Name], Uses)
+rnBind sig_fn trim (L loc (PatBind { pat_lhs = pat, pat_rhs = grhss }))
+  = setSrcSpan loc $ 
+    do { (pat', pat_fvs) <- rnLPat pat
+
+       ; let bndrs = collectPatBinders pat'
+
+       ; (grhss', fvs) <- bindSigTyVarsFV (concatMap sig_fn bndrs) $
+                          rnGRHSs PatBindRhs grhss
+
+       ; return (L loc (PatBind { pat_lhs = pat', pat_rhs = grhss', 
+                                  pat_rhs_ty = placeHolderType, bind_fvs = trim fvs }), 
+                 bndrs, pat_fvs `plusFV` fvs) }
+
+rnBind sig_fn trim (L loc (FunBind { fun_id = name, fun_infix = inf, fun_matches = matches }))
+  = setSrcSpan loc $ 
+    do { new_name <- lookupLocatedBndrRn name
+       ; let plain_name = unLoc new_name
+
+       ; (matches', fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
+                            rnMatchGroup (FunRhs plain_name) matches
+
+       ; checkPrecMatch inf plain_name matches'
+
+       ; return (L loc (FunBind { fun_id = new_name, fun_infix = inf, fun_matches = matches',
+                                  bind_fvs = trim fvs, fun_co_fn = idCoercion }), 
+                 [plain_name], fvs)
+      }

 \end{code}
 
 \end{code}
 

-@flattenMonoBinds@ is ever-so-slightly magical in that it sticks
-unique ``vertex tags'' on its output; minor plumbing required.

 
 

-\begin{code}
-flattenMonoBinds :: Int                                -- Next free vertex tag
-                -> [RenamedSig]                -- Signatures
-                -> RdrNameMonoBinds
-                -> RnM_Fixes s (Int, FlatMonoBindsInfo)
-
-flattenMonoBinds uniq sigs EmptyMonoBinds = returnRn (uniq, [])
-
-flattenMonoBinds uniq sigs (AndMonoBinds bs1 bs2)
-  = flattenMonoBinds uniq  sigs bs1    `thenRn` \ (uniq1, flat1) ->
-    flattenMonoBinds uniq1 sigs bs2    `thenRn` \ (uniq2, flat2) ->
-    returnRn (uniq2, flat1 ++ flat2)
-
-flattenMonoBinds uniq sigs (PatMonoBind pat grhss_and_binds locn)
-  = pushSrcLocRn locn                  $
-    rnPat pat                          `thenRn` \ pat' ->
-    rnGRHSsAndBinds grhss_and_binds    `thenRn` \ (grhss_and_binds', fvs) ->
-
-        -- Find which things are bound in this group
-    let
-       names_bound_here = collectPatBinders pat'
-
-       sigs_etc_for_here = foldl (sig_for_here (\ n -> n `is_elem` names_bound_here))
-                                 [] sigs
+@rnMethodBinds@ is used for the method bindings of a class and an instance
+declaration.   Like @rnBinds@ but without dependency analysis.

 
 

-       sigs_fvs = foldr sig_fv emptyUniqSet sigs_etc_for_here
+NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
+That's crucial when dealing with an instance decl:
+\begin{verbatim}
+       instance Foo (T a) where
+          op x = ...
+\end{verbatim}
+This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
+and unless @op@ occurs we won't treat the type signature of @op@ in the class
+decl for @Foo@ as a source of instance-decl gates.  But we should!  Indeed,
+in many ways the @op@ in an instance decl is just like an occurrence, not
+a binder.

 
 

-       is_elem = isIn "flattenMonoBinds"
+\begin{code}
+rnMethodBinds :: Name                  -- Class name
+             -> [Name]                 -- Names for generic type variables
+             -> LHsBinds RdrName
+             -> RnM (LHsBinds Name, FreeVars)
+
+rnMethodBinds cls gen_tyvars binds
+  = foldM do_one (emptyBag,emptyFVs) (bagToList binds)
+  where do_one (binds,fvs) bind = do
+          (bind', fvs_bind) <- rnMethodBind cls gen_tyvars bind
+          return (bind' `unionBags` binds, fvs_bind `plusFV` fvs)
+
+rnMethodBind cls gen_tyvars (L loc (FunBind { fun_id = name, fun_infix = inf, 
+                                             fun_matches = MatchGroup matches _ }))
+  =  setSrcSpan loc $ 
+     lookupLocatedInstDeclBndr cls name                        `thenM` \ sel_name -> 
+     let plain_name = unLoc sel_name in
+       -- We use the selector name as the binder
+
+    mapFvRn (rn_match plain_name) matches              `thenM` \ (new_matches, fvs) ->
+    let 
+       new_group = MatchGroup new_matches placeHolderType

     in
     in

-    returnRn (
-       uniq + 1,
-       [(uniq,
-         mkUniqSet names_bound_here,
-          fvs `unionUniqSets` sigs_fvs,
-          PatMonoBind pat' grhss_and_binds' locn,
-          sigs_etc_for_here
-        )]
-    )
-
-flattenMonoBinds uniq sigs (FunMonoBind name inf matches locn)
-  = pushSrcLocRn locn                           $
-    lookupValue name                            `thenRn` \ name' ->
-    mapAndUnzipRn rnMatch matches               `thenRn` \ (new_matches, fv_lists) ->
-    mapRn (checkPrecMatch inf name') new_matches `thenRn_`
-    let
-       fvs = unionManyUniqSets fv_lists
+    checkPrecMatch inf plain_name new_group            `thenM_`
+    returnM (unitBag (L loc (FunBind { fun_id = sel_name, fun_infix = inf, fun_matches = new_group,
+                                      bind_fvs = fvs, fun_co_fn = idCoercion })), 
+            fvs `addOneFV` plain_name)
+       -- The 'fvs' field isn't used for method binds
+  where
+       -- Truly gruesome; bring into scope the correct members of the generic 
+       -- type variables.  See comments in RnSource.rnSourceDecl(ClassDecl)
+    rn_match sel_name match@(L _ (Match (L _ (TypePat ty) : _) _ _))
+       = extendTyVarEnvFVRn gen_tvs    $
+         rnMatch (FunRhs sel_name) match
+       where
+         tvs     = map (rdrNameOcc.unLoc) (extractHsTyRdrTyVars ty)
+         gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs] 

 
 

-       sigs_for_me = foldl (sig_for_here (\ n -> n == name')) [] sigs
+    rn_match sel_name match = rnMatch (FunRhs sel_name) match

 
 

-       sigs_fvs = foldr sig_fv emptyUniqSet sigs_for_me
-    in
-    returnRn (
-      uniq + 1,
-      [(uniq,
-       unitUniqSet name',
-       fvs `unionUniqSets` sigs_fvs,
-       FunMonoBind name' inf new_matches locn,
-       sigs_for_me
-       )]
-    )
-\end{code}

 
 

-Grab type-signatures/user-pragmas of interest:
-\begin{code}
-sig_for_here want_me acc s@(Sig n _ _ _)     | want_me n = s:acc
-sig_for_here want_me acc s@(InlineSig n _)   | want_me n = s:acc
-sig_for_here want_me acc s@(DeforestSig n _) | want_me n = s:acc
-sig_for_here want_me acc s@(SpecSig n _ _ _) | want_me n = s:acc
-sig_for_here want_me acc s@(MagicUnfoldingSig n _ _)
-                                            | want_me n = s:acc
-sig_for_here want_me acc other_wise                     = acc
-
--- If a SPECIALIZE pragma is of the "... = blah" form,
--- then we'd better make sure "blah" is taken into
--- acct in the dependency analysis (or we get an
--- unexpected out-of-scope error)! WDP 95/07
-
-sig_fv (SpecSig _ _ (Just blah) _) acc = acc `unionUniqSets` unitUniqSet blah
-sig_fv _                          acc = acc
+-- Can't handle method pattern-bindings which bind multiple methods.
+rnMethodBind cls gen_tyvars mbind@(L loc (PatBind other_pat _ _ _))
+  = addLocErr mbind methodBindErr      `thenM_`
+    returnM (emptyBag, emptyFVs) 

 \end{code}
 
 \end{code}
 

+

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

-\subsection[reconstruct-deps]{Reconstructing dependencies}
+\subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}

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

-This @MonoBinds@- and @ClassDecls@-specific code is segregated here,
-as the two cases are similar.
+@renameSigs@ checks for:
+\begin{enumerate}
+\item more than one sig for one thing;
+\item signatures given for things not bound here;
+\item with suitably flaggery, that all top-level things have type signatures.
+\end{enumerate}
+%
+At the moment we don't gather free-var info from the types in
+signatures.  We'd only need this if we wanted to report unused tyvars.

 
 \begin{code}
 
 \begin{code}

-reconstructRec :: [Cycle]      -- Result of SCC analysis; at least one
-               -> [Edge]       -- Original edges
-               -> FlatMonoBindsInfo
-               -> RenamedHsBinds
-
-reconstructRec cycles edges mbi
-  = foldr1 ThenBinds (map (reconstructCycle mbi) cycles)
+renameSigs :: (LSig Name -> Bool) -> [LSig RdrName] -> RnM [LSig Name]
+-- Renames the signatures and performs error checks
+renameSigs ok_sig sigs 
+  = do { sigs' <- rename_sigs sigs
+       ; check_sigs ok_sig sigs'
+       ; return sigs' }
+
+----------------------
+rename_sigs :: [LSig RdrName] -> RnM [LSig Name]
+rename_sigs sigs = mappM (wrapLocM renameSig)
+                        (filter (not . isFixityLSig) sigs)
+               -- Remove fixity sigs which have been dealt with already
+
+----------------------
+check_sigs :: (LSig Name -> Bool) -> [LSig Name] -> RnM ()
+-- Used for class and instance decls, as well as regular bindings
+check_sigs ok_sig sigs 
+       -- Check for (a) duplicate signatures
+       --           (b) signatures for things not in this group
+  = do { mappM_ unknownSigErr (filter (not . ok_sig) sigs')
+       ; mappM_ dupSigDeclErr (findDupsEq eqHsSig sigs') }

   where
   where

-    reconstructCycle :: FlatMonoBindsInfo -> Cycle -> RenamedHsBinds
-
-    reconstructCycle mbi2 cycle
-      = case [(binds,sigs) | (vertex, _, _, binds, sigs) <- mbi2, vertex `is_elem` cycle]
-                 of { relevant_binds_and_sigs ->
-
-       case (unzip relevant_binds_and_sigs) of { (binds, sig_lists) ->
-
-       case (foldr AndMonoBinds EmptyMonoBinds binds) of { this_gp_binds ->
-       let
-           this_gp_sigs        = foldr1 (++) sig_lists
-           have_sigs           = not (null sig_lists)
-               -- ToDo: this might not be the right
-               -- thing to call this predicate;
-               -- e.g. "have_sigs [[], [], []]" ???????????
-       in
-       mk_binds this_gp_binds this_gp_sigs (isCyclic edges cycle) have_sigs
-       }}}
-      where
-       is_elem = isIn "reconstructRec"
-
-       mk_binds :: RenamedMonoBinds -> [RenamedSig]
-                -> Bool -> Bool -> RenamedHsBinds
-
-       mk_binds bs ss True  False              = SingleBind (RecBind    bs)
-       mk_binds bs ss True  True{-have sigs-}  = BindWith   (RecBind    bs) ss
-       mk_binds bs ss False False              = SingleBind (NonRecBind bs)
-       mk_binds bs ss False True{-have sigs-}  = BindWith   (NonRecBind bs) ss
-
-       -- moved from Digraph, as this is the only use here
-       -- (avoid overloading cost).  We have to use elem
-       -- (not FiniteMaps or whatever), because there may be
-       -- many edges out of one vertex.  We give it its own
-       -- "elem" just for speed.
-
-       isCyclic es []  = panic "isCyclic: empty component"
-       isCyclic es [v] = (v,v) `elem` es
-       isCyclic es vs  = True
-
-       elem _ []       = False
-       elem x (y:ys)   = x==y || elem x ys
+       -- Don't complain about an unbound name again
+    sigs' = filterOut bad_name sigs
+    bad_name sig = case sigName sig of
+                       Just n -> isUnboundName n
+                       other  -> False
+
+-- We use lookupLocatedSigOccRn in the signatures, which is a little bit unsatisfactory
+-- because this won't work for:
+--     instance Foo T where
+--       {-# INLINE op #-}
+--       Baz.op = ...
+-- We'll just rename the INLINE prag to refer to whatever other 'op'
+-- is in scope.  (I'm assuming that Baz.op isn't in scope unqualified.)
+-- Doesn't seem worth much trouble to sort this.
+
+renameSig :: Sig RdrName -> RnM (Sig Name)
+-- FixitSig is renamed elsewhere.
+renameSig (TypeSig v ty)
+  = lookupLocatedSigOccRn v                    `thenM` \ new_v ->
+    rnHsSigType (quotes (ppr v)) ty            `thenM` \ new_ty ->
+    returnM (TypeSig new_v new_ty)
+
+renameSig (SpecInstSig ty)
+  = rnLHsType (text "A SPECIALISE instance pragma") ty `thenM` \ new_ty ->
+    returnM (SpecInstSig new_ty)
+
+renameSig (SpecSig v ty inl)
+  = lookupLocatedSigOccRn v            `thenM` \ new_v ->
+    rnHsSigType (quotes (ppr v)) ty    `thenM` \ new_ty ->
+    returnM (SpecSig new_v new_ty inl)
+
+renameSig (InlineSig v s)
+  = lookupLocatedSigOccRn v            `thenM` \ new_v ->
+    returnM (InlineSig new_v s)

 \end{code}
 
 \end{code}
 

-%************************************************************************
-%*                                                                     *
-%*     Manipulating FlatMonoBindInfo                                   *
-%*                                                                     *
-%************************************************************************

 
 

-During analysis a @MonoBinds@ is flattened to a @FlatMonoBindsInfo@.
-The @RenamedMonoBinds@ is always an empty bind, a pattern binding or
-a function binding, and has itself been dependency-analysed and
-renamed.
+************************************************************************
+*                                                                      *
+\subsection{Match}
+*                                                                      *
+************************************************************************

 
 \begin{code}
 
 \begin{code}

-type FlatMonoBindsInfo
-  = [(VertexTag,               -- Identifies the vertex
-      UniqSet RnName,          -- Set of names defined in this vertex
-      UniqSet RnName,          -- Set of names used in this vertex
-      RenamedMonoBinds,                -- Binding for this vertex (always just one binding, either fun or pat)
-      [RenamedSig])            -- Signatures, if any, for this vertex
-    ]
-
-mkVertices :: FlatMonoBindsInfo -> [VertexTag]
-mkEdges    :: FlatMonoBindsInfo -> [Edge]
-
-mkVertices info = [ vertex | (vertex,_,_,_,_) <- info]
-
-mkEdges flat_info
- -- An edge (v,v') indicates that v depends on v'
-  = -- pprTrace "mkEdges:" (ppAboves [ppAboves[ppInt v, ppCat [ppr PprDebug d|d <- uniqSetToList defd], ppCat [ppr PprDebug u|u <- uniqSetToList used]] | (v,defd,used,_,_) <- flat_info]) $
-    [ (source_vertex, target_vertex)
-    | (source_vertex, _, used_names, _, _) <- flat_info,
-      target_name   <- uniqSetToList used_names,
-      target_vertex <- vertices_defining target_name flat_info
-    ]
-    where
-    -- If each name only has one binding in this group, then
-    -- vertices_defining will always return the empty list, or a
-    -- singleton.  The case when there is more than one binding (an
-    -- error) needs more thought.
-
-    vertices_defining name flat_info2
-     = [ vertex |  (vertex, names_defined, _, _, _) <- flat_info2,
-                name `elementOfUniqSet` names_defined
-       ]
+rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
+rnMatchGroup ctxt (MatchGroup ms _)
+  = mapFvRn (rnMatch ctxt) ms  `thenM` \ (new_ms, ms_fvs) ->
+    returnM (MatchGroup new_ms placeHolderType, ms_fvs)
+
+rnMatch :: HsMatchContext Name -> LMatch RdrName -> RnM (LMatch Name, FreeVars)
+rnMatch ctxt  = wrapLocFstM (rnMatch' ctxt)
+
+rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
+  = 
+       -- Deal with the rhs type signature
+    bindPatSigTyVarsFV rhs_sig_tys     $ 
+    doptM Opt_GlasgowExts              `thenM` \ opt_GlasgowExts ->
+    (case maybe_rhs_sig of
+       Nothing -> returnM (Nothing, emptyFVs)
+       Just ty | opt_GlasgowExts -> rnHsTypeFVs doc_sig ty     `thenM` \ (ty', ty_fvs) ->
+                                    returnM (Just ty', ty_fvs)
+               | otherwise       -> addLocErr ty patSigErr     `thenM_`
+                                    returnM (Nothing, emptyFVs)
+    )                                  `thenM` \ (maybe_rhs_sig', ty_fvs) ->
+
+       -- Now the main event
+    rnPatsAndThen ctxt pats    $ \ pats' ->
+    rnGRHSs ctxt grhss         `thenM` \ (grhss', grhss_fvs) ->
+
+    returnM (Match pats' maybe_rhs_sig' grhss', grhss_fvs `plusFV` ty_fvs)
+       -- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
+  where
+     rhs_sig_tys =  case maybe_rhs_sig of
+                       Nothing -> []
+                       Just ty -> [ty]
+     doc_sig = text "In a result type-signature"

 \end{code}
 
 
 %************************************************************************
 %*                                                                     *
 \end{code}
 
 
 %************************************************************************
 %*                                                                     *

-\subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
+\subsubsection{Guarded right-hand sides (GRHSs)}

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

-@rnBindSigs@ checks for: (a)~more than one sig for one thing;
-(b)~signatures given for things not bound here; (c)~with suitably
-flaggery, that all top-level things have type signatures.
-

 \begin{code}
 \begin{code}

-rnBindSigs :: Bool                     -- True <=> top-level binders
-           -> [RdrName]                -- Binders for this decl group
-           -> [RdrNameSig]
-           -> RnM_Fixes s [RenamedSig] -- List of Sig constructors
-
-rnBindSigs is_toplev binder_occnames sigs
-  =
-        -- Rename the signatures
-        -- Will complain about sigs for variables not in this group
-    mapRn rename_sig sigs      `thenRn` \ sigs_maybe ->
-    let
-       sigs' = catMaybes sigs_maybe
+rnGRHSs :: HsMatchContext Name -> GRHSs RdrName -> RnM (GRHSs Name, FreeVars)

 
 

-        -- Discard unbound ones we've already complained about, so we
-        -- complain about duplicate ones.
+rnGRHSs ctxt (GRHSs grhss binds)
+  = rnLocalBindsAndThen binds  $ \ binds' ->
+    mapFvRn (rnGRHS ctxt) grhss        `thenM` \ (grhss', fvGRHSs) ->
+    returnM (GRHSs grhss' binds', fvGRHSs)

 
 

-       (goodies, dups) = removeDups compare (filter (\ x -> not_unbound x && not_main x) sigs')
-    in
-    mapRn (addErrRn . dupSigDeclErr) dups `thenRn_`
+rnGRHS :: HsMatchContext Name -> LGRHS RdrName -> RnM (LGRHS Name, FreeVars)
+rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)

 
 

-    getSrcLocRn                        `thenRn` \ locn ->
+rnGRHS' ctxt (GRHS guards rhs)
+  = do { opt_GlasgowExts <- doptM Opt_GlasgowExts
+       ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $
+                                   rnLExpr rhs

 
 

-    (if (is_toplev && opt_SigsRequired) then
-       let
-           sig_frees = catMaybes (map (sig_free sigs) binder_occnames)
-       in
-       mapRn (addErrRn . missingSigErr locn) sig_frees
-     else
-       returnRn []
-    )                          `thenRn_`
+       ; checkM (opt_GlasgowExts || is_standard_guard guards')
+                (addWarn (nonStdGuardErr guards'))

 
 

-    returnRn sigs' -- bad ones and all:
-                  -- we need bindings of *some* sort for every name
+       ; return (GRHS guards' rhs', fvs) }

   where
   where

-    rename_sig (Sig v ty pragmas src_loc)
-      = pushSrcLocRn src_loc $
-       if not (v `elem` binder_occnames) then
-          addErrRn (unknownSigDeclErr "type signature" v src_loc) `thenRn_`
-          returnRn Nothing
-       else
-          lookupValue v                        `thenRn` \ new_v ->
-          rnPolyType nullTyVarNamesEnv ty      `thenRn` \ new_ty ->
-
-          ASSERT(isNoGenPragmas pragmas)
-          returnRn (Just (Sig new_v new_ty noGenPragmas src_loc))
-
-    -- and now, the various flavours of value-modifying user-pragmas:
-
-    rename_sig (SpecSig v ty using src_loc)
-      = pushSrcLocRn src_loc $
-       if not (v `elem` binder_occnames) then
-          addErrRn (unknownSigDeclErr "SPECIALIZE pragma" v src_loc) `thenRn_`
-          returnRn Nothing
-       else
-          lookupValue v                        `thenRn` \ new_v ->
-          rnPolyType nullTyVarNamesEnv ty      `thenRn` \ new_ty ->
-          rn_using using                       `thenRn` \ new_using ->
-          returnRn (Just (SpecSig new_v new_ty new_using src_loc))
-      where
-       rn_using Nothing  = returnRn Nothing
-       rn_using (Just x) = lookupValue x `thenRn` \ new_x ->
-                           returnRn (Just new_x)
-
-    rename_sig (InlineSig v src_loc)
-      = pushSrcLocRn src_loc $
-       if not (v `elem` binder_occnames) then
-          addErrRn (unknownSigDeclErr "INLINE pragma" v src_loc) `thenRn_`
-          returnRn Nothing
-       else
-          lookupValue v        `thenRn` \ new_v ->
-          returnRn (Just (InlineSig new_v src_loc))
-
-    rename_sig (DeforestSig v src_loc)
-      = pushSrcLocRn src_loc $
-       if not (v `elem` binder_occnames) then
-          addErrRn (unknownSigDeclErr "DEFOREST pragma" v src_loc) `thenRn_`
-          returnRn Nothing
-       else
-          lookupValue v        `thenRn` \ new_v ->
-          returnRn (Just (DeforestSig new_v src_loc))
-
-    rename_sig (MagicUnfoldingSig v str src_loc)
-      = pushSrcLocRn src_loc $
-       if not (v `elem` binder_occnames) then
-          addErrRn (unknownSigDeclErr "MAGIC_UNFOLDING pragma" v src_loc) `thenRn_`
-          returnRn Nothing
-       else
-          lookupValue v        `thenRn` \ new_v ->
-          returnRn (Just (MagicUnfoldingSig new_v str src_loc))
-
-    not_unbound, not_main :: RenamedSig -> Bool
-
-    not_unbound (Sig n _ _ _)            = not (isRnUnbound n)
-    not_unbound (SpecSig n _ _ _)        = not (isRnUnbound n)
-    not_unbound (InlineSig n _)                  = not (isRnUnbound n)
-    not_unbound (DeforestSig n _)        = not (isRnUnbound n)
-    not_unbound (MagicUnfoldingSig n _ _) = not (isRnUnbound n)
-
-    not_main (Sig n _ _ _)  = let str = getLocalName n in
-                             not (str == SLIT("main") || str == SLIT("mainPrimIO"))
-    not_main _             = True
-
-    -------------------------------------
-    sig_free :: [RdrNameSig] -> RdrName -> Maybe RdrName
-       -- Return "Just x" if "x" has no type signature in
-       -- sigs.  Nothing, otherwise.
-
-    sig_free [] ny = Just ny
-    sig_free (Sig nx _ _ _ : rest) ny
-      = if (nx == ny) then Nothing else sig_free rest ny
-    sig_free (_ : rest) ny = sig_free rest ny
-
-    -------------------------------------
-    compare :: RenamedSig -> RenamedSig -> TAG_
-    compare (Sig n1 _ _ _)            (Sig n2 _ _ _)             = n1 `cmp` n2
-    compare (InlineSig n1 _)          (InlineSig n2 _)           = n1 `cmp` n2
-    compare (MagicUnfoldingSig n1 _ _) (MagicUnfoldingSig n2 _ _) = n1 `cmp` n2
-    compare (SpecSig n1 ty1 _ _)       (SpecSig n2 ty2 _ _)
-      = -- may have many specialisations for one value;
-       -- but not ones that are exactly the same...
-       thenCmp (n1 `cmp` n2) (cmpPolyType cmp ty1 ty2)
-
-    compare other_1 other_2    -- tags *must* be different
-      = let tag1 = tag other_1
-           tag2 = tag other_2
-       in
-       if tag1 _LT_ tag2 then LT_ else GT_
-
-    tag (Sig n1 _ _ _)            = (ILIT(1) :: FAST_INT)
-    tag (SpecSig n1 _ _ _)        = ILIT(2)
-    tag (InlineSig n1 _)          = ILIT(3)
-    tag (MagicUnfoldingSig n1 _ _) = ILIT(4)
-    tag (DeforestSig n1 _)         = ILIT(5)
-    tag _ = panic# "tag(RnBinds)"
+       -- Standard Haskell 1.4 guards are just a single boolean
+       -- expression, rather than a list of qualifiers as in the
+       -- Glasgow extension
+    is_standard_guard []                     = True
+    is_standard_guard [L _ (ExprStmt _ _ _)] = True
+    is_standard_guard other                 = False

 \end{code}
 
 %************************************************************************
 \end{code}
 
 %************************************************************************

@@ -651,46 +626,35 @@ rnBindSigs is_toplev binder_occnames sigs
 %************************************************************************
 
 \begin{code}
 %************************************************************************
 
 \begin{code}

-dupSigDeclErr sigs
-  = let
-       undup_sigs = fst (removeDups cmp_sig sigs)
-    in
-    addErrLoc locn1
-       ("more than one "++what_it_is++"\n\thas been given for these variables") ( \ sty ->
-    ppAboves (map (ppr sty) undup_sigs) )
+dupSigDeclErr sigs@(L loc sig : _)
+  = addErrAt loc $
+       vcat [ptext SLIT("Duplicate") <+> what_it_is <> colon,
+             nest 2 (vcat (map ppr_sig sigs))]
+  where
+    what_it_is = hsSigDoc sig
+    ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
+
+unknownSigErr (L loc sig)
+  = addErrAt loc $
+       sep [ptext SLIT("Misplaced") <+> what_it_is <> colon, ppr sig]

   where
   where

-    (what_it_is, locn1)
-      = case (head sigs) of
-         Sig        _ _ _ loc -> ("type signature",loc)
-         ClassOpSig _ _ _ loc -> ("class-method type signature", loc)
-         SpecSig    _ _ _ loc -> ("SPECIALIZE pragma",loc)
-         InlineSig  _     loc -> ("INLINE pragma",loc)
-         MagicUnfoldingSig _ _ loc -> ("MAGIC_UNFOLDING pragma",loc)
-
-    cmp_sig a b = get_name a `cmp` get_name b
-
-    get_name (Sig        n _ _ _) = n
-    get_name (ClassOpSig n _ _ _) = n
-    get_name (SpecSig    n _ _ _) = n
-    get_name (InlineSig  n     _) = n
-    get_name (MagicUnfoldingSig n _ _) = n
-
-------------------------
-methodBindErr mbind locn
- = addErrLoc locn "Can't handle multiple methods defined by one pattern binding"
-       (\ sty -> ppr sty mbind)
-
---------------------------
-missingSigErr locn var
-  = addShortErrLocLine locn ( \ sty ->
-    ppBesides [ppStr "a definition but no type signature for `",
-              ppr sty var,
-              ppStr "'."])
-
---------------------------------
-unknownSigDeclErr flavor var locn
-  = addShortErrLocLine locn ( \ sty ->
-    ppBesides [ppStr flavor, ppStr " but no definition for `",
-              ppr sty var,
-              ppStr "'."])
+    what_it_is = hsSigDoc sig
+
+missingSigWarn var
+  = addWarnAt (mkSrcSpan loc loc) $
+      sep [ptext SLIT("Definition but no type signature for"), quotes (ppr var)]
+  where 
+    loc = nameSrcLoc var  -- TODO: make a proper span
+
+methodBindErr mbind
+ =  hang (ptext SLIT("Pattern bindings (except simple variables) not allowed in instance declarations"))
+       2 (ppr mbind)
+
+bindsInHsBootFile mbinds
+  = hang (ptext SLIT("Bindings in hs-boot files are not allowed"))
+       2 (ppr mbinds)
+
+nonStdGuardErr guards
+  = hang (ptext SLIT("accepting non-standard pattern guards (-fglasgow-exts to suppress this message)"))
+       4 (interpp'SP guards)

 \end{code}
 \end{code}