X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDefaults.lhs;h=7335631009c7fa672eb03c2c4a05eec1ae5ac919;hb=438596897ebbe25a07e1c82085cfbc5bdb00f09e;hp=0296080e8aa8679c9d627b6677be4303c4f74213;hpb=ca5a4a480d10d61e5b7a52eb4d556e8b8c33e69d;p=ghc-hetmet.git

diff --git a/ghc/compiler/typecheck/TcDefaults.lhs b/ghc/compiler/typecheck/TcDefaults.lhs
index 0296080..7335631 100644
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -1,43 +1,43 @@
 %
-% (c) The AQUA Project, Glasgow University, 1993-1995
+% (c) The AQUA Project, Glasgow University, 1993-1998
 %
 \section[TcDefaults]{Typechecking \tr{default} declarations}
 
 \begin{code}
-#include "HsVersions.h"
-
 module TcDefaults ( tcDefaults ) where
 
-import Ubiq
+#include "HsVersions.h"
 
-import HsSyn		( DefaultDecl(..), MonoType,
-			  HsExpr, HsLit, ArithSeqInfo, Fake, InPat)
-import RnHsSyn		( RenamedDefaultDecl(..) )
-import TcHsSyn		( TcIdOcc )
+import HsSyn		( HsDecl(..), DefaultDecl(..) )
+import RnHsSyn		( RenamedHsDecl )
 
-import TcMonad		hiding ( rnMtoTcM )
-import Inst		( InstOrigin(..) )
+import TcMonad
 import TcEnv		( tcLookupClassByKey )
-import TcMonoType	( tcMonoType )
+import TcMonoType	( tcHsType )
 import TcSimplify	( tcSimplifyCheckThetas )
 
-import PrelInfo		( intTy, doubleTy, unitTy )
+import TysWiredIn	( intTy, doubleTy )
+import Type             ( Type )
 import Unique		( numClassKey )
+import ErrUtils		( addShortErrLocLine )
+import Outputable
 import Util
 \end{code}
 
 \begin{code}
-tcDefaults :: [RenamedDefaultDecl]
+default_default = [intTy, doubleTy] 	    -- language-specified default `default'
+
+tcDefaults :: [RenamedHsDecl]
 	   -> TcM s [Type] 	    -- defaulting types to heave
 				    -- into Tc monad for later use
 				    -- in Disambig.
+tcDefaults decls = tc_defaults [default_decl | DefD default_decl <- decls]
 
-tcDefaults []
-  = returnTc [intTy, doubleTy] 	    -- language-specified default `default'
+tc_defaults [] = returnTc default_default
 
-tcDefaults [DefaultDecl mono_tys locn]
+tc_defaults [DefaultDecl mono_tys locn]
   = tcAddSrcLoc locn $
-    mapTc tcMonoType mono_tys	`thenTc` \ tau_tys ->
+    mapTc tcHsType mono_tys	`thenTc` \ tau_tys ->
 
     case tau_tys of
       [] -> returnTc []		-- no defaults
@@ -46,10 +46,28 @@ tcDefaults [DefaultDecl mono_tys locn]
 	    -- Check that all the types are instances of Num
 	    -- We only care about whether it worked or not
 
-	tcLookupClassByKey numClassKey			`thenNF_Tc` \ num ->
-	tcSimplifyCheckThetas DefaultDeclOrigin
-		[ (num, ty) | ty <- tau_tys ]		`thenTc` \ _ ->
+	tcAddErrCtxt defaultDeclCtxt		$
+	tcLookupClassByKey numClassKey		`thenNF_Tc` \ num ->
+	tcSimplifyCheckThetas
+		[{- Nothing given -}]
+		[ (num, [ty]) | ty <- tau_tys ]	`thenTc_`
 
 	returnTc tau_tys
 
+tc_defaults decls
+  = failWithTc (dupDefaultDeclErr decls)
+
+
+defaultDeclCtxt =  ptext SLIT("when checking that each type in a default declaration")
+		    $$ ptext SLIT("is an instance of class Num")
+
+
+dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things)
+  = vcat (item1 : map dup_item dup_things)
+  where
+    item1
+      = addShortErrLocLine locn1 (ptext SLIT("multiple default declarations"))
+
+    dup_item (DefaultDecl _ locn)
+      = addShortErrLocLine locn (ptext SLIT("here was another default declaration"))
 \end{code}