From 6e5c95e9102581703b8cb2734b87d7958bce4183 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Fri, 17 Sep 1999 09:13:17 +0000
Subject: [PATCH] [project @ 1999-09-17 09:13:14 by simonpj]
 /home/simonpj/tmp/msg1

---
 ghc/compiler/typecheck/Inst.lhs       | 257 +++++++-------------------
 ghc/compiler/typecheck/TcDeriv.lhs    |   2 +-
 ghc/compiler/typecheck/TcIfaceSig.lhs |   4 +-
 ghc/compiler/typecheck/TcMatches.lhs  |   2 +-
 ghc/compiler/typecheck/TcModule.lhs   |  11 +-
 ghc/compiler/typecheck/TcMonad.lhs    | 131 ++++++++++++-
 ghc/compiler/typecheck/TcSimplify.lhs |  49 +++--
 7 files changed, 224 insertions(+), 232 deletions(-)

diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs
index 155ed13c4d2f..a076b026fea5 100644
--- a/ghc/compiler/typecheck/Inst.lhs
+++ b/ghc/compiler/typecheck/Inst.lhs
@@ -25,7 +25,7 @@ module Inst (
 
 	zonkInst, instToId, instToIdBndr,
 
-	InstOrigin(..), pprOrigin
+	InstOrigin(..), InstLoc, pprInstLoc
     ) where
 
 #include "HsVersions.h"
@@ -107,7 +107,7 @@ pprInsts insts = parens (sep (punctuate comma (map pprInst insts)))
 pprInstsInFull insts
   = vcat (map go insts)
   where
-    go inst = quotes (ppr inst) <+> pprOrigin inst
+    go inst = quotes (ppr inst) <+> pprInstLoc (instLoc inst)
 \end{code}
 
 %************************************************************************
@@ -130,8 +130,7 @@ data Inst
 	Unique
 	Class		-- The type of the dict is (c ts), where
 	[TcType]	-- c is the class and ts the types;
-	InstOrigin
-	SrcLoc
+	InstLoc
 
   | Method
 	Unique
@@ -152,8 +151,7 @@ data Inst
 
 	TcTauType	-- The type of the method
 
-	InstOrigin
-	SrcLoc
+	InstLoc
 
 	-- INVARIANT: in (Method u f tys theta tau loc)
 	--	type of (f tys dicts(from theta)) = tau
@@ -162,8 +160,7 @@ data Inst
 	Unique
 	OverloadedLit
 	TcType		-- The type at which the literal is used
-	InstOrigin	-- Always a literal; but more convenient to carry this around
-	SrcLoc
+	InstLoc
 
 data OverloadedLit
   = OverloadedIntegral	 Integer	-- The number
@@ -185,22 +182,22 @@ instance Eq Inst where
 	         EQ    -> True
 		 other -> False
 
-cmpInst  (Dict _ clas1 tys1 _ _) (Dict _ clas2 tys2 _ _)
+cmpInst  (Dict _ clas1 tys1 _) (Dict _ clas2 tys2 _)
   = (clas1 `compare` clas2) `thenCmp` (tys1 `compare` tys2)
-cmpInst (Dict _ _ _ _ _) other
+cmpInst (Dict _ _ _ _) other
   = LT
 
 
-cmpInst (Method _ _ _ _ _ _ _) (Dict _ _ _ _ _)
+cmpInst (Method _ _ _ _ _ _) (Dict _ _ _ _)
   = GT
-cmpInst (Method _ id1 tys1 _ _ _ _) (Method _ id2 tys2 _ _ _ _)
+cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _)
   = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2)
-cmpInst (Method _ _ _ _ _ _ _) other
+cmpInst (Method _ _ _ _ _ _) other
   = LT
 
-cmpInst (LitInst _ lit1 ty1 _ _) (LitInst _ lit2 ty2 _ _)
+cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _)
   = (lit1 `cmpOverLit` lit2) `thenCmp` (ty1 `compare` ty2)
-cmpInst (LitInst _ _ _ _ _) other
+cmpInst (LitInst _ _ _ _) other
   = GT
 
 cmpOverLit (OverloadedIntegral   i1) (OverloadedIntegral   i2) = i1 `compare` i2
@@ -213,43 +210,39 @@ cmpOverLit (OverloadedFractional _)  (OverloadedIntegral _)    = GT
 Selection
 ~~~~~~~~~
 \begin{code}
-instOrigin (Dict   u clas tys    origin loc) = origin
-instOrigin (Method u clas ty _ _ origin loc) = origin
-instOrigin (LitInst u lit ty     origin loc) = origin
+instLoc (Dict   u clas tys  loc) = loc
+instLoc (Method u _ _ _ _   loc) = loc
+instLoc (LitInst u lit ty   loc) = loc
 
-instLoc (Dict   u clas tys    origin loc) = loc
-instLoc (Method u clas ty _ _ origin loc) = loc
-instLoc (LitInst u lit ty     origin loc) = loc
-
-getDictClassTys (Dict u clas tys _ _) = (clas, tys)
+getDictClassTys (Dict u clas tys _) = (clas, tys)
 
 tyVarsOfInst :: Inst -> TcTyVarSet
-tyVarsOfInst (Dict _ _ tys _ _)        = tyVarsOfTypes  tys
-tyVarsOfInst (Method _ id tys _ _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id
+tyVarsOfInst (Dict _ _ tys _)        = tyVarsOfTypes  tys
+tyVarsOfInst (Method _ id tys _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id
 					 -- The id might have free type variables; in the case of
 					 -- locally-overloaded class methods, for example
-tyVarsOfInst (LitInst _ _ ty _ _)     = tyVarsOfType  ty
+tyVarsOfInst (LitInst _ _ ty _)      = tyVarsOfType  ty
 \end{code}
 
 Predicates
 ~~~~~~~~~~
 \begin{code}
 isDict :: Inst -> Bool
-isDict (Dict _ _ _ _ _) = True
-isDict other	        = False
+isDict (Dict _ _ _ _) = True
+isDict other	      = False
 
 isMethodFor :: TcIdSet -> Inst -> Bool
-isMethodFor ids (Method uniq id tys _ _ orig loc) 
+isMethodFor ids (Method uniq id tys _ _ loc) 
   = id `elemVarSet` ids
 isMethodFor ids inst 
   = False
 
 isTyVarDict :: Inst -> Bool
-isTyVarDict (Dict _ _ tys _ _) = all isTyVarTy tys
-isTyVarDict other 	       = False
+isTyVarDict (Dict _ _ tys _) = all isTyVarTy tys
+isTyVarDict other 	     = False
 
-isStdClassTyVarDict (Dict _ clas [ty] _ _) = isStandardClass clas && isTyVarTy ty
-isStdClassTyVarDict other		   = False
+isStdClassTyVarDict (Dict _ clas [ty] _) = isStandardClass clas && isTyVarTy ty
+isStdClassTyVarDict other		 = False
 \end{code}
 
 Two predicates which deal with the case where class constraints don't
@@ -259,12 +252,12 @@ must be witnessed by an actual binding; the second tells whether an
 
 \begin{code}
 instBindingRequired :: Inst -> Bool
-instBindingRequired (Dict _ clas _ _ _) = not (isNoDictClass clas)
-instBindingRequired other		= True
+instBindingRequired (Dict _ clas _ _) = not (isNoDictClass clas)
+instBindingRequired other	      = True
 
 instCanBeGeneralised :: Inst -> Bool
-instCanBeGeneralised (Dict _ clas _ _ _) = not (isCcallishClass clas)
-instCanBeGeneralised other		 = True
+instCanBeGeneralised (Dict _ clas _ _) = not (isCcallishClass clas)
+instCanBeGeneralised other	       = True
 \end{code}
 
 
@@ -276,28 +269,27 @@ newDicts :: InstOrigin
 	 -> TcThetaType
 	 -> NF_TcM s (LIE, [TcId])
 newDicts orig theta
-  = tcGetSrcLoc				`thenNF_Tc` \ loc ->
-    newDictsAtLoc orig loc theta        `thenNF_Tc` \ (dicts, ids) ->
+  = tcGetInstLoc orig		`thenNF_Tc` \ loc ->
+    newDictsAtLoc loc theta	`thenNF_Tc` \ (dicts, ids) ->
     returnNF_Tc (listToBag dicts, ids)
 
 -- Local function, similar to newDicts, 
 -- but with slightly different interface
-newDictsAtLoc :: InstOrigin
-              -> SrcLoc
+newDictsAtLoc :: InstLoc
  	      -> TcThetaType
 	      -> NF_TcM s ([Inst], [TcId])
-newDictsAtLoc orig loc theta =
+newDictsAtLoc loc theta =
  tcGetUniques (length theta)		`thenNF_Tc` \ new_uniqs ->
  let
-  mk_dict u (clas, tys) = Dict u clas tys orig loc
+  mk_dict u (clas, tys) = Dict u clas tys loc
   dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta
  in
  returnNF_Tc (dicts, map instToId dicts)
 
 newDictFromOld :: Inst -> Class -> [TcType] -> NF_TcM s Inst
-newDictFromOld (Dict _ _ _ orig loc) clas tys
+newDictFromOld (Dict _ _ _ loc) clas tys
   = tcGetUnique	      `thenNF_Tc` \ uniq ->
-    returnNF_Tc (Dict uniq clas tys orig loc)
+    returnNF_Tc (Dict uniq clas tys loc)
 
 
 newMethod :: InstOrigin
@@ -319,17 +311,17 @@ instOverloadedFun orig (HsVar v) arg_tys theta tau
     returnNF_Tc (HsVar (instToId inst), unitLIE inst)
 
 newMethodWithGivenTy orig id tys theta tau
-  = tcGetSrcLoc		`thenNF_Tc` \ loc ->
+  = tcGetInstLoc orig	`thenNF_Tc` \ loc ->
     tcGetUnique		`thenNF_Tc` \ new_uniq ->
     let
-	meth_inst = Method new_uniq id tys theta tau orig loc
+	meth_inst = Method new_uniq id tys theta tau loc
     in
     returnNF_Tc meth_inst
 
-newMethodAtLoc :: InstOrigin -> SrcLoc
+newMethodAtLoc :: InstLoc
 	       -> Id -> [TcType]
 	       -> NF_TcM s (Inst, TcId)
-newMethodAtLoc orig loc real_id tys	-- Local function, similar to newMethod but with 
+newMethodAtLoc loc real_id tys		-- Local function, similar to newMethod but with 
 					-- slightly different interface
   =   	-- Get the Id type and instantiate it at the specified types
     tcGetUnique					`thenNF_Tc` \ new_uniq ->
@@ -338,7 +330,7 @@ newMethodAtLoc orig loc real_id tys	-- Local function, similar to newMethod but
 	rho_ty	      = ASSERT( length tyvars == length tys )
 			substTy (mkTopTyVarSubst tyvars tys) rho
 	(theta, tau)  = splitRhoTy rho_ty
-	meth_inst     = Method new_uniq real_id tys theta tau orig loc
+	meth_inst     = Method new_uniq real_id tys theta tau loc
     in
     returnNF_Tc (meth_inst, instToId meth_inst)
 \end{code}
@@ -366,10 +358,10 @@ newOverloadedLit orig (OverloadedIntegral i) ty
     int_lit        = HsCon intDataCon [] [intprim_lit]
 
 newOverloadedLit orig lit ty		-- The general case
-  = tcGetSrcLoc			`thenNF_Tc` \ loc ->
+  = tcGetInstLoc orig		`thenNF_Tc` \ loc ->
     tcGetUnique			`thenNF_Tc` \ new_uniq ->
     let
-	lit_inst = LitInst new_uniq lit ty orig loc
+	lit_inst = LitInst new_uniq lit ty loc
     in
     returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)
 \end{code}
@@ -380,13 +372,13 @@ instToId :: Inst -> TcId
 instToId inst = instToIdBndr inst
 
 instToIdBndr :: Inst -> TcId
-instToIdBndr (Dict u clas ty orig loc)
+instToIdBndr (Dict u clas ty (_,loc,_))
   = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas ty) loc
 
-instToIdBndr (Method u id tys theta tau orig loc)
+instToIdBndr (Method u id tys theta tau (_,loc,_))
   = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc
     
-instToIdBndr (LitInst u list ty orig loc)
+instToIdBndr (LitInst u list ty loc)
   = mkSysLocal SLIT("lit") u ty
 \end{code}
 
@@ -399,11 +391,11 @@ need, and it's a lot of extra work.
 
 \begin{code}
 zonkInst :: Inst -> NF_TcM s Inst
-zonkInst (Dict u clas tys orig loc)
+zonkInst (Dict u clas tys loc)
   = zonkTcTypes	tys			`thenNF_Tc` \ new_tys ->
-    returnNF_Tc (Dict u clas new_tys orig loc)
+    returnNF_Tc (Dict u clas new_tys loc)
 
-zonkInst (Method u id tys theta tau orig loc) 
+zonkInst (Method u id tys theta tau loc) 
   = zonkId id			`thenNF_Tc` \ new_id ->
 	-- Essential to zonk the id in case it's a local variable
 	-- Can't use zonkIdOcc because the id might itself be
@@ -412,11 +404,11 @@ zonkInst (Method u id tys theta tau orig loc)
     zonkTcTypes tys		`thenNF_Tc` \ new_tys ->
     zonkTcThetaType theta	`thenNF_Tc` \ new_theta ->
     zonkTcType tau		`thenNF_Tc` \ new_tau ->
-    returnNF_Tc (Method u new_id new_tys new_theta new_tau orig loc)
+    returnNF_Tc (Method u new_id new_tys new_theta new_tau loc)
 
-zonkInst (LitInst u lit ty orig loc)
+zonkInst (LitInst u lit ty loc)
   = zonkTcType ty			`thenNF_Tc` \ new_ty ->
-    returnNF_Tc (LitInst u lit new_ty orig loc)
+    returnNF_Tc (LitInst u lit new_ty loc)
 \end{code}
 
 
@@ -429,7 +421,7 @@ relevant in error messages.
 instance Outputable Inst where
     ppr inst = pprInst inst
 
-pprInst (LitInst u lit ty orig loc)
+pprInst (LitInst u lit ty loc)
   = hsep [case lit of
 	      OverloadedIntegral   i -> integer i
 	      OverloadedFractional f -> rational f,
@@ -437,26 +429,26 @@ pprInst (LitInst u lit ty orig loc)
 	   ppr ty,
 	   show_uniq u]
 
-pprInst (Dict u clas tys orig loc) = pprConstraint clas tys <+> show_uniq u
+pprInst (Dict u clas tys loc) = pprConstraint clas tys <+> show_uniq u
 
-pprInst (Method u id tys _ _ orig loc)
+pprInst (Method u id tys _ _ loc)
   = hsep [ppr id, ptext SLIT("at"), 
 	  brackets (interppSP tys),
 	  show_uniq u]
 
 tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst)
-tidyInst env (LitInst u lit ty orig loc)
-  = (env', LitInst u lit ty' orig loc)
+tidyInst env (LitInst u lit ty loc)
+  = (env', LitInst u lit ty' loc)
   where
     (env', ty') = tidyOpenType env ty
 
-tidyInst env (Dict u clas tys orig loc)
-  = (env', Dict u clas tys' orig loc)
+tidyInst env (Dict u clas tys loc)
+  = (env', Dict u clas tys' loc)
   where
     (env', tys') = tidyOpenTypes env tys
 
-tidyInst env (Method u id tys theta tau orig loc)
-  = (env', Method u id tys' theta tau orig loc)
+tidyInst env (Method u id tys theta tau loc)
+  = (env', Method u id tys' theta tau loc)
 		-- Leave theta, tau alone cos we don't print them
   where
     (env', tys') = tidyOpenTypes env tys
@@ -503,7 +495,7 @@ lookupInst :: Inst
 
 -- Dictionaries
 
-lookupInst dict@(Dict _ clas tys orig loc)
+lookupInst dict@(Dict _ clas tys loc)
   = case lookupInstEnv (ppr clas) (classInstEnv clas) tys of
 
       Just (tenv, dfun_id)
@@ -521,7 +513,7 @@ lookupInst dict@(Dict _ clas tys orig loc)
 	   if null theta then
 		returnNF_Tc (SimpleInst ty_app)
 	   else
-	   newDictsAtLoc orig loc theta	`thenNF_Tc` \ (dicts, dict_ids) ->
+	   newDictsAtLoc loc theta	`thenNF_Tc` \ (dicts, dict_ids) ->
 	   let 
 		rhs = mkHsDictApp ty_app dict_ids
 	   in
@@ -531,13 +523,13 @@ lookupInst dict@(Dict _ clas tys orig loc)
 
 -- Methods
 
-lookupInst inst@(Method _ id tys theta _ orig loc)
-  = newDictsAtLoc orig loc theta	`thenNF_Tc` \ (dicts, dict_ids) ->
+lookupInst inst@(Method _ id tys theta _ loc)
+  = newDictsAtLoc loc theta		`thenNF_Tc` \ (dicts, dict_ids) ->
     returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids))
 
 -- Literals
 
-lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc)
+lookupInst inst@(LitInst u (OverloadedIntegral i) ty loc)
   | isIntTy ty && in_int_range			-- Short cut for Int
   = returnNF_Tc (GenInst [] int_lit)
 	-- GenInst, not SimpleInst, because int_lit is actually a constructor application
@@ -547,12 +539,12 @@ lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc)
 
   | in_int_range				-- It's overloaded but small enough to fit into an Int
   = tcLookupValueByKey fromIntClassOpKey	`thenNF_Tc` \ from_int ->
-    newMethodAtLoc orig loc from_int [ty]	`thenNF_Tc` \ (method_inst, method_id) ->
+    newMethodAtLoc loc from_int [ty]		`thenNF_Tc` \ (method_inst, method_id) ->
     returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) int_lit))
 
   | otherwise   				-- Alas, it is overloaded and a big literal!
   = tcLookupValueByKey fromIntegerClassOpKey	`thenNF_Tc` \ from_integer ->
-    newMethodAtLoc orig loc from_integer [ty]		`thenNF_Tc` \ (method_inst, method_id) ->
+    newMethodAtLoc loc from_integer [ty]	`thenNF_Tc` \ (method_inst, method_id) ->
     returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) integer_lit))
   where
     in_int_range   = inIntRange i
@@ -564,7 +556,7 @@ lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc)
 -- *definitely* a float or a double, generate the real thing here.
 -- This is essential  (see nofib/spectral/nucleic).
 
-lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc)
+lookupInst inst@(LitInst u (OverloadedFractional f) ty loc)
   | isFloatTy ty    = returnNF_Tc (GenInst [] float_lit)
   | isDoubleTy ty   = returnNF_Tc (GenInst [] double_lit)
 
@@ -577,7 +569,7 @@ lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc)
 	rational_ty  = mkSynTy rational_tycon []
 	rational_lit = HsLitOut (HsFrac f) rational_ty
     in
-    newMethodAtLoc orig loc from_rational [ty]		`thenNF_Tc` \ (method_inst, method_id) ->
+    newMethodAtLoc loc from_rational [ty]		`thenNF_Tc` \ (method_inst, method_id) ->
     returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit))
 
   where
@@ -608,110 +600,3 @@ lookupSimpleInst class_inst_env clas tys
         where
 	   (_, theta, _) = splitSigmaTy (idType dfun)
 \end{code}
-
-
-
-%************************************************************************
-%*									*
-\subsection[Inst-origin]{The @InstOrigin@ type}
-%*									*
-%************************************************************************
-
-The @InstOrigin@ type gives information about where a dictionary came from.
-This is important for decent error message reporting because dictionaries
-don't appear in the original source code.  Doubtless this type will evolve...
-
-\begin{code}
-data InstOrigin
-  = OccurrenceOf TcId	-- Occurrence of an overloaded identifier
-  | OccurrenceOfCon Id		-- Occurrence of a data constructor
-
-  | RecordUpdOrigin
-
-  | DataDeclOrigin		-- Typechecking a data declaration
-
-  | InstanceDeclOrigin		-- Typechecking an instance decl
-
-  | LiteralOrigin	HsLit	-- Occurrence of a literal
-
-  | PatOrigin RenamedPat
-
-  | ArithSeqOrigin	RenamedArithSeqInfo -- [x..], [x..y] etc
-
-  | SignatureOrigin		-- A dict created from a type signature
-  | Rank2Origin			-- A dict created when typechecking the argument
-				-- of a rank-2 typed function
-
-  | DoOrigin			-- The monad for a do expression
-
-  | ClassDeclOrigin		-- Manufactured during a class decl
-
-  | InstanceSpecOrigin	Class	-- in a SPECIALIZE instance pragma
-			Type
-
-	-- When specialising instances the instance info attached to
-	-- each class is not yet ready, so we record it inside the
-	-- origin information.  This is a bit of a hack, but it works
-	-- fine.  (Patrick is to blame [WDP].)
-
-  | ValSpecOrigin	Name	-- in a SPECIALIZE pragma for a value
-
-	-- Argument or result of a ccall
-	-- Dictionaries with this origin aren't actually mentioned in the
-	-- translated term, and so need not be bound.  Nor should they
-	-- be abstracted over.
-
-  | CCallOrigin		String			-- CCall label
-			(Maybe RenamedHsExpr)	-- Nothing if it's the result
-						-- Just arg, for an argument
-
-  | LitLitOrigin	String	-- the litlit
-
-  | UnknownOrigin	-- Help! I give up...
-\end{code}
-
-\begin{code}
-pprOrigin :: Inst -> SDoc
-pprOrigin inst
-  = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
-  where
-    (orig, locn) = case inst of
-			Dict _ _ _       orig loc -> (orig,loc)
-			Method _ _ _ _ _ orig loc -> (orig,loc)
-			LitInst _ _ _    orig loc -> (orig,loc)
-			
-    pp_orig (OccurrenceOf id)
-      	= hsep [ptext SLIT("use of"), quotes (ppr id)]
-    pp_orig (OccurrenceOfCon id)
-	= hsep [ptext SLIT("use of"), quotes (ppr id)]
-    pp_orig (LiteralOrigin lit)
-	= hsep [ptext SLIT("the literal"), quotes (ppr lit)]
-    pp_orig (PatOrigin pat)
-	= hsep [ptext SLIT("the pattern"), quotes (ppr pat)]
-    pp_orig (InstanceDeclOrigin)
-	=  ptext SLIT("an instance declaration")
-    pp_orig (ArithSeqOrigin seq)
-	= hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
-    pp_orig (SignatureOrigin)
-	=  ptext SLIT("a type signature")
-    pp_orig (Rank2Origin)
-	=  ptext SLIT("a function with an overloaded argument type")
-    pp_orig (DoOrigin)
-	=  ptext SLIT("a do statement")
-    pp_orig (ClassDeclOrigin)
-	=  ptext SLIT("a class declaration")
-    pp_orig (InstanceSpecOrigin clas ty)
-	= hsep [text "a SPECIALIZE instance pragma; class",
-	        quotes (ppr clas), text "type:", ppr ty]
-    pp_orig (ValSpecOrigin name)
-	= hsep [ptext SLIT("a SPECIALIZE user-pragma for"), quotes (ppr name)]
-    pp_orig (CCallOrigin clabel Nothing{-ccall result-})
-	= hsep [ptext SLIT("the result of the _ccall_ to"), quotes (text clabel)]
-    pp_orig (CCallOrigin clabel (Just arg_expr))
-	= hsep [ptext SLIT("an argument in the _ccall_ to"), quotes (text clabel) <> comma, 
-		text "namely", quotes (ppr arg_expr)]
-    pp_orig (LitLitOrigin s)
-	= hsep [ptext SLIT("the ``literal-literal''"), quotes (text s)]
-    pp_orig (UnknownOrigin)
-	= ptext SLIT("...oops -- I don't know where the overloading came from!")
-\end{code}
diff --git a/ghc/compiler/typecheck/TcDeriv.lhs b/ghc/compiler/typecheck/TcDeriv.lhs
index fd54e6ecdc02..a6894074e226 100644
--- a/ghc/compiler/typecheck/TcDeriv.lhs
+++ b/ghc/compiler/typecheck/TcDeriv.lhs
@@ -29,7 +29,7 @@ import RnMonad		( RnNameSupply,
 
 import Bag		( Bag, emptyBag, unionBags, listToBag )
 import Class		( classKey, Class )
-import ErrUtils		( dumpIfSet, Message )
+import ErrUtils		( dumpIfSet, Message, pprBagOfErrors )
 import MkId		( mkDictFunId )
 import Id		( mkVanillaId )
 import DataCon		( dataConArgTys, isNullaryDataCon )
diff --git a/ghc/compiler/typecheck/TcIfaceSig.lhs b/ghc/compiler/typecheck/TcIfaceSig.lhs
index bb63100b1640..c4a59f33ec38 100644
--- a/ghc/compiler/typecheck/TcIfaceSig.lhs
+++ b/ghc/compiler/typecheck/TcIfaceSig.lhs
@@ -31,7 +31,7 @@ import CoreSyn
 import CoreUtils	( coreExprType )
 import CoreUnfold
 import CoreLint		( lintUnfolding )
-import WwLib		( mkWrapper )
+import WorkWrap		( mkWrapper )
 import PrimOp		( PrimOp(..) )
 
 import Id		( Id, mkId, mkVanillaId,
@@ -136,7 +136,7 @@ tcWorkerInfo unf_env ty info worker_name
       cpr_info   = cprInfo info
       demands    = case strictnessInfo info of
 			StrictnessInfo d _ -> d
-			_                  -> repeat wwLazy	-- Noncommittal
+			_                  -> take arity (repeat wwLazy)	-- Noncommittal
 \end{code}
 
 For unfoldings we try to do the job lazily, so that we never type check
diff --git a/ghc/compiler/typecheck/TcMatches.lhs b/ghc/compiler/typecheck/TcMatches.lhs
index 9722bfe980fb..8a27ea5139e8 100644
--- a/ghc/compiler/typecheck/TcMatches.lhs
+++ b/ghc/compiler/typecheck/TcMatches.lhs
@@ -403,7 +403,7 @@ stmtCtxt do_or_lc stmt
   where
     what = case do_or_lc of
 		ListComp -> ptext SLIT("a list-comprehension qualifier")
-		DoStmt   -> ptext SLIT("a do statement:")
+		DoStmt   -> ptext SLIT("a do statement")
 		PatBindRhs -> thing <+> ptext SLIT("a pattern binding")
 		FunRhs f   -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f)
 		CaseAlt	   -> thing <+> ptext SLIT("a case alternative")
diff --git a/ghc/compiler/typecheck/TcModule.lhs b/ghc/compiler/typecheck/TcModule.lhs
index cd82d9ee4763..c3b6dc203862 100644
--- a/ghc/compiler/typecheck/TcModule.lhs
+++ b/ghc/compiler/typecheck/TcModule.lhs
@@ -46,9 +46,7 @@ import TcType		( TcType, typeToTcType,
 
 import RnMonad		( RnNameSupply, getIfaceFixities, Fixities, InterfaceDetails )
 import Bag		( isEmptyBag )
-import ErrUtils		( Message,
-			  pprBagOfErrors, dumpIfSet
-			)
+import ErrUtils		( Message, printErrorsAndWarnings, dumpIfSet )
 import Id		( Id, idType )
 import Module           ( pprModuleName )
 import Name		( Name, nameUnique, isLocallyDefined, NamedThing(..) )
@@ -99,8 +97,7 @@ typecheckModule us rn_name_supply iface_det mod
   = initTc us initEnv (tcModule rn_name_supply (getIfaceFixities iface_det) mod)
 		    	>>= \ (maybe_result, warns, errs) ->
 		
-    print_errs warns	>>
-    print_errs errs	>>
+    printErrorsAndWarnings errs warns		>>
 
     -- write the thin-air Id map
     (case maybe_result of
@@ -124,10 +121,6 @@ pp_rules [] = empty
 pp_rules rs = vcat [ptext SLIT("{-# RULES"),
 		    nest 4 (vcat (map ppr rs)),
 		    ptext SLIT("#-}")]
-
-print_errs errs
-  | isEmptyBag errs = return ()
-  | otherwise       = printErrs (pprBagOfErrors errs)
 \end{code}
 
 The internal monster:
diff --git a/ghc/compiler/typecheck/TcMonad.lhs b/ghc/compiler/typecheck/TcMonad.lhs
index 27abfa73b824..2deadb007390 100644
--- a/ghc/compiler/typecheck/TcMonad.lhs
+++ b/ghc/compiler/typecheck/TcMonad.lhs
@@ -22,19 +22,21 @@ module TcMonad(
 
 	checkTc, checkTcM, checkMaybeTc, checkMaybeTcM, 
 	failTc, failWithTc, addErrTc, warnTc, recoverTc, checkNoErrsTc, recoverNF_Tc, discardErrsTc,
-	addErrTcM, failWithTcM,
+	addErrTcM, addInstErrTcM, failWithTcM,
 
 	tcGetEnv, tcSetEnv,
 	tcGetDefaultTys, tcSetDefaultTys,
 	tcGetUnique, tcGetUniques,
 
-	tcAddSrcLoc, tcGetSrcLoc,
+	tcAddSrcLoc, tcGetSrcLoc, tcGetInstLoc,
 	tcAddErrCtxtM, tcSetErrCtxtM,
 	tcAddErrCtxt, tcSetErrCtxt,
 
 	tcNewMutVar, tcNewSigTyVar, tcReadMutVar, tcWriteMutVar, TcRef,
 	tcNewMutTyVar, tcReadMutTyVar, tcWriteMutTyVar,
 
+	InstOrigin(..), InstLoc, pprInstLoc, 
+
 	TcError, TcWarning, TidyEnv, emptyTidyEnv,
 	arityErr
   ) where
@@ -43,16 +45,18 @@ module TcMonad(
 
 import {-# SOURCE #-} TcEnv  ( TcEnv )
 
+import HsSyn		( HsLit )
+import RnHsSyn		( RenamedPat, RenamedArithSeqInfo, RenamedHsExpr )
 import Type		( Type, Kind, ThetaType, RhoType, TauType,
 			)
-import ErrUtils		( addShortErrLocLine, addShortWarnLocLine, ErrMsg, Message, WarnMsg )
+import ErrUtils		( addShortErrLocLine, addShortWarnLocLine, pprBagOfErrors, ErrMsg, Message, WarnMsg )
 import CmdLineOpts      ( opt_PprStyle_Debug )
 
 import Bag		( Bag, emptyBag, isEmptyBag,
 			  foldBag, unitBag, unionBags, snocBag )
 import Class		( Class )
 import Name		( Name )
-import Var		( TyVar, newMutTyVar, newSigTyVar, readMutTyVar, writeMutTyVar )
+import Var		( Id, TyVar, newMutTyVar, newSigTyVar, readMutTyVar, writeMutTyVar )
 import VarEnv		( TyVarEnv, emptyVarEnv, TidyEnv, emptyTidyEnv )
 import VarSet		( TyVarSet )
 import UniqSupply	( UniqSupply, uniqFromSupply, uniqsFromSupply, splitUniqSupply,
@@ -313,6 +317,18 @@ checkMaybeTcM Nothing    err = err
 
 addErrTcM :: (TidyEnv, Message) -> NF_TcM s ()	-- Add an error message but don't fail
 addErrTcM (tidy_env, err_msg) down env
+  = add_err_tcm tidy_env err_msg ctxt loc down env
+  where
+    ctxt     = getErrCtxt down
+    loc      = getLoc down
+
+addInstErrTcM :: InstLoc -> (TidyEnv, Message) -> NF_TcM s ()	-- Add an error message but don't fail
+addInstErrTcM inst_loc@(_, loc, ctxt) (tidy_env, err_msg) down env
+  = add_err_tcm tidy_env err_msg full_ctxt loc down env
+  where
+    full_ctxt = (\env -> returnNF_Tc (env, pprInstLoc inst_loc)) : ctxt
+
+add_err_tcm tidy_env err_msg ctxt loc down env
   = do
 	(warns, errs) <- readIORef errs_var
 	ctxt_msgs     <- do_ctxt tidy_env ctxt down env
@@ -321,8 +337,6 @@ addErrTcM (tidy_env, err_msg) down env
 	writeIORef errs_var (warns, errs `snocBag` err)
   where
     errs_var = getTcErrs down
-    ctxt     = getErrCtxt down
-    loc      = getLoc down
 
 do_ctxt tidy_env [] down env
   = return []
@@ -467,6 +481,9 @@ tcAddSrcLoc loc m down env = m (setLoc down loc) env
 tcGetSrcLoc :: NF_TcM s SrcLoc
 tcGetSrcLoc down env = return (getLoc down)
 
+tcGetInstLoc :: InstOrigin -> NF_TcM s InstLoc
+tcGetInstLoc origin down env = return (origin, getLoc down, getErrCtxt down)
+
 tcSetErrCtxtM, tcAddErrCtxtM :: (TidyEnv -> NF_TcM s (TidyEnv, Message))
 			     -> TcM s a -> TcM s a
 tcSetErrCtxtM msg m down env = m (setErrCtxt down msg) env
@@ -581,3 +598,105 @@ arityErr kind name n m
 \end{code}
 
 
+
+%************************************************************************
+%*									*
+\subsection[Inst-origin]{The @InstOrigin@ type}
+%*									*
+%************************************************************************
+
+The @InstOrigin@ type gives information about where a dictionary came from.
+This is important for decent error message reporting because dictionaries
+don't appear in the original source code.  Doubtless this type will evolve...
+
+It appears in TcMonad because there are a couple of error-message-generation
+functions that deal with it.
+
+\begin{code}
+type InstLoc = (InstOrigin, SrcLoc, ErrCtxt)
+
+data InstOrigin
+  = OccurrenceOf Id		-- Occurrence of an overloaded identifier
+
+  | RecordUpdOrigin
+
+  | DataDeclOrigin		-- Typechecking a data declaration
+
+  | InstanceDeclOrigin		-- Typechecking an instance decl
+
+  | LiteralOrigin HsLit		-- Occurrence of a literal
+
+  | PatOrigin RenamedPat
+
+  | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc
+
+  | SignatureOrigin		-- A dict created from a type signature
+  | Rank2Origin			-- A dict created when typechecking the argument
+				-- of a rank-2 typed function
+
+  | DoOrigin			-- The monad for a do expression
+
+  | ClassDeclOrigin		-- Manufactured during a class decl
+
+  | InstanceSpecOrigin	Class	-- in a SPECIALIZE instance pragma
+			Type
+
+	-- When specialising instances the instance info attached to
+	-- each class is not yet ready, so we record it inside the
+	-- origin information.  This is a bit of a hack, but it works
+	-- fine.  (Patrick is to blame [WDP].)
+
+  | ValSpecOrigin	Name	-- in a SPECIALIZE pragma for a value
+
+	-- Argument or result of a ccall
+	-- Dictionaries with this origin aren't actually mentioned in the
+	-- translated term, and so need not be bound.  Nor should they
+	-- be abstracted over.
+
+  | CCallOrigin		String			-- CCall label
+			(Maybe RenamedHsExpr)	-- Nothing if it's the result
+						-- Just arg, for an argument
+
+  | LitLitOrigin	String	-- the litlit
+
+  | UnknownOrigin	-- Help! I give up...
+\end{code}
+
+\begin{code}
+pprInstLoc :: InstLoc -> SDoc
+pprInstLoc (orig, locn, ctxt)
+  = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
+  where
+    pp_orig (OccurrenceOf id)
+      	= hsep [ptext SLIT("use of"), quotes (ppr id)]
+    pp_orig (LiteralOrigin lit)
+	= hsep [ptext SLIT("the literal"), quotes (ppr lit)]
+    pp_orig (PatOrigin pat)
+	= hsep [ptext SLIT("the pattern"), quotes (ppr pat)]
+    pp_orig (InstanceDeclOrigin)
+	=  ptext SLIT("an instance declaration")
+    pp_orig (ArithSeqOrigin seq)
+	= hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
+    pp_orig (SignatureOrigin)
+	=  ptext SLIT("a type signature")
+    pp_orig (Rank2Origin)
+	=  ptext SLIT("a function with an overloaded argument type")
+    pp_orig (DoOrigin)
+	=  ptext SLIT("a do statement")
+    pp_orig (ClassDeclOrigin)
+	=  ptext SLIT("a class declaration")
+    pp_orig (InstanceSpecOrigin clas ty)
+	= hsep [text "a SPECIALIZE instance pragma; class",
+	        quotes (ppr clas), text "type:", ppr ty]
+    pp_orig (ValSpecOrigin name)
+	= hsep [ptext SLIT("a SPECIALIZE user-pragma for"), quotes (ppr name)]
+    pp_orig (CCallOrigin clabel Nothing{-ccall result-})
+	= hsep [ptext SLIT("the result of the _ccall_ to"), quotes (text clabel)]
+    pp_orig (CCallOrigin clabel (Just arg_expr))
+	= hsep [ptext SLIT("an argument in the _ccall_ to"), quotes (text clabel) <> comma, 
+		text "namely", quotes (ppr arg_expr)]
+    pp_orig (LitLitOrigin s)
+	= hsep [ptext SLIT("the ``literal-literal''"), quotes (text s)]
+    pp_orig (UnknownOrigin)
+	= ptext SLIT("...oops -- I don't know where the overloading came from!")
+\end{code}
diff --git a/ghc/compiler/typecheck/TcSimplify.lhs b/ghc/compiler/typecheck/TcSimplify.lhs
index dde4d4cc9fb2..ccae6cbde933 100644
--- a/ghc/compiler/typecheck/TcSimplify.lhs
+++ b/ghc/compiler/typecheck/TcSimplify.lhs
@@ -135,10 +135,10 @@ import Inst		( lookupInst, lookupSimpleInst, LookupInstResult(..),
 			  isDict, isStdClassTyVarDict, isMethodFor,
 			  instToId, instBindingRequired, instCanBeGeneralised,
 			  newDictFromOld,
-			  instLoc, getDictClassTys,
-			  pprInst, zonkInst, tidyInst, tidyInsts,
+			  getDictClassTys,
+			  instLoc, pprInst, zonkInst, tidyInst, tidyInsts,
 			  Inst, LIE, pprInsts, pprInstsInFull, mkLIE, emptyLIE, 
-			  plusLIE, pprOrigin
+			  plusLIE
 			)
 import TcEnv		( tcGetGlobalTyVars )
 import TcType		( TcType, TcTyVarSet, typeToTcType )
@@ -1138,12 +1138,11 @@ genCantGenErr insts	-- Can't generalise these Insts
 addAmbigErrs ambig_tv_fn dicts = mapNF_Tc (addAmbigErr ambig_tv_fn) dicts
 
 addAmbigErr ambig_tv_fn dict
-  = tcAddSrcLoc (instLoc dict) $
-    addErrTcM (tidy_env,
-	       sep [text "Ambiguous type variable(s)" <+>
+  = addInstErrTcM (instLoc dict)
+	(tidy_env,
+	 sep [text "Ambiguous type variable(s)" <+>
 			hsep (punctuate comma (map (quotes . ppr) ambig_tvs)),
-		   nest 4 (text "in the constraint" <+> quotes (pprInst tidy_dict)),
-	 	   nest 4 (pprOrigin dict)])
+	      nest 4 (text "in the constraint" <+> quotes (pprInst tidy_dict))])
   where
     ambig_tvs = varSetElems (ambig_tv_fn tidy_dict)
     (tidy_env, tidy_dict) = tidyInst emptyTidyEnv dict
@@ -1153,8 +1152,7 @@ warnDefault dicts default_ty
   = returnNF_Tc ()
 
   | otherwise
-  = tcAddSrcLoc (instLoc (head dicts))		$
-    warnTc True msg
+  = warnTc True msg
   where
     msg | length dicts > 1 
 	= (ptext SLIT("Defaulting the following constraint(s) to type") <+> quotes (ppr default_ty))
@@ -1166,33 +1164,30 @@ warnDefault dicts default_ty
     (_, tidy_dicts) = mapAccumL tidyInst emptyTidyEnv dicts
 
 addRuleLhsErr dict
-  = tcAddSrcLoc (instLoc dict)			$
-    addErrTcM (tidy_env,
-	       vcat [ptext SLIT("Could not deduce") <+> quotes (pprInst tidy_dict),
-		     nest 4 (pprOrigin dict),
-		     ptext SLIT("LHS of a rule must have no overloading")])
+  = addInstErrTcM (instLoc dict)
+	(tidy_env,
+	 vcat [ptext SLIT("Could not deduce") <+> quotes (pprInst tidy_dict),
+	       nest 4 (ptext SLIT("LHS of a rule must have no overloading"))])
   where
     (tidy_env, tidy_dict) = tidyInst emptyTidyEnv dict
 
 -- Used for top-level irreducibles
 addTopInstanceErr dict
-  = tcAddSrcLoc (instLoc dict)		       $
-    addErrTcM (tidy_env, 
-	       sep [ptext SLIT("No instance for") <+> quotes (pprInst tidy_dict),
-		   nest 4 $ pprOrigin dict])
+  = addInstErrTcM (instLoc dict) 
+	(tidy_env, 
+	 ptext SLIT("No instance for") <+> quotes (pprInst tidy_dict))
   where
     (tidy_env, tidy_dict) = tidyInst emptyTidyEnv dict
 
 addNoInstanceErr str givens dict
-  = tcAddSrcLoc (instLoc dict) $
-    addErrTcM (tidy_env, 
-	       sep [sep [ptext SLIT("Could not deduce") <+> quotes (pprInst tidy_dict),
-		        nest 4 $ parens $ pprOrigin dict],
-		   nest 4 $ ptext SLIT("from the context:") <+> pprInsts tidy_givens]
-	      $$
-	      ptext SLIT("Probable cause:") <+> 
+  = addInstErrTcM (instLoc dict) 
+	(tidy_env, 
+	 sep [ptext SLIT("Could not deduce") <+> quotes (pprInst tidy_dict),
+	      nest 4 $ ptext SLIT("from the context:") <+> pprInsts tidy_givens]
+	$$
+	 ptext SLIT("Probable cause:") <+> 
 	      vcat [sep [ptext SLIT("missing") <+> quotes (pprInst tidy_dict),
-			 ptext SLIT("in") <+> str],
+		    ptext SLIT("in") <+> str],
 		    if all_tyvars then empty else
 		    ptext SLIT("or missing instance declaration for") <+> quotes (pprInst tidy_dict)]
     )
-- 
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