X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcRnTypes.lhs;h=fd7e954b743a07fdc91e34b473ae24fb023e4f39;hb=1fede4bc9501744bf2269ce2a4cb9fb735969caa;hp=daed79dbd48a4b3bb4e27c8404090e175ca67eba;hpb=703ca1542c8e0983cc9d8eebce6e9f3dd3fd71e2;p=ghc-hetmet.git

diff --git a/compiler/typecheck/TcRnTypes.lhs b/compiler/typecheck/TcRnTypes.lhs
index daed79d..fd7e954 100644
--- a/compiler/typecheck/TcRnTypes.lhs
+++ b/compiler/typecheck/TcRnTypes.lhs
@@ -222,14 +222,8 @@ data TcGblEnv
           -- reference is implicit rather than explicit, so we have to zap a
           -- mutable variable.
 
-	tcg_dfun_n  :: TcRef Int,
-          -- ^ Allows us to number off the names of DFuns.
-          --
-          -- It's convenient to allocate an External Name for a DFun, with
-          -- a permanently-fixed unique, just like other top-level functions
-          -- defined in this module.  But that means we need a canonical
-          -- occurrence name, distinct from all other dfuns in this module,
-          -- and this name supply serves that purpose (df1, df2, etc).
+	tcg_dfun_n  :: TcRef OccSet,
+          -- ^ Allows us to choose unique DFun names.
 
 	-- The next fields accumulate the payload of the module
 	-- The binds, rules and foreign-decl fiels are collected
@@ -339,7 +333,7 @@ data TcLclEnv		-- Changes as we move inside an expression
 			-- Discarded after typecheck/rename; not passed on to desugarer
   = TcLclEnv {
 	tcl_loc  :: SrcSpan,		-- Source span
-	tcl_ctxt :: ErrCtxt,		-- Error context
+	tcl_ctxt :: [ErrCtxt],		-- Error context, innermost on top
 	tcl_errs :: TcRef Messages,	-- Place to accumulate errors
 
 	tcl_th_ctxt    :: ThStage,	      -- Template Haskell context
@@ -522,10 +516,13 @@ instance Outputable RefinementVisibility where
 \end{code}
 
 \begin{code}
-type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]	
-			-- Innermost first.  Monadic so that we have a chance
-			-- to deal with bound type variables just before error
-			-- message construction
+type ErrCtxt = (Bool, TidyEnv -> TcM (TidyEnv, Message))
+	-- Monadic so that we have a chance
+	-- to deal with bound type variables just before error
+	-- message construction
+
+	-- Bool:  True <=> this is a landmark context; do not
+	--		   discard it when trimming for display
 \end{code}
 
 
@@ -882,7 +879,7 @@ functions that deal with it.
 
 \begin{code}
 -------------------------------------------
-data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
+data InstLoc = InstLoc InstOrigin SrcSpan [ErrCtxt]
 
 instLoc :: Inst -> InstLoc
 instLoc inst = tci_loc inst