X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcDefaults.lhs;h=6c9de36a3c099979b3336f97596373b9c94847b7;hb=7434eae33776ba56eae28dfd85172dd86d180be2;hp=0296080e8aa8679c9d627b6677be4303c4f74213;hpb=ca5a4a480d10d61e5b7a52eb4d556e8b8c33e69d;p=ghc-hetmet.git

diff --git a/ghc/compiler/typecheck/TcDefaults.lhs b/ghc/compiler/typecheck/TcDefaults.lhs
index 0296080..6c9de36 100644
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -1,55 +1,79 @@
 %
-% (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
-
-import HsSyn		( DefaultDecl(..), MonoType,
-			  HsExpr, HsLit, ArithSeqInfo, Fake, InPat)
-import RnHsSyn		( RenamedDefaultDecl(..) )
-import TcHsSyn		( TcIdOcc )
-
-import TcMonad		hiding ( rnMtoTcM )
-import Inst		( InstOrigin(..) )
-import TcEnv		( tcLookupClassByKey )
-import TcMonoType	( tcMonoType )
-import TcSimplify	( tcSimplifyCheckThetas )
+#include "HsVersions.h"
 
-import PrelInfo		( intTy, doubleTy, unitTy )
-import Unique		( numClassKey )
-import Util
+import HsSyn		( DefaultDecl(..), LDefaultDecl )
+import Name		( Name )
+import TcRnMonad
+import TcEnv		( tcLookupClass )
+import TcHsType		( tcHsSigType, UserTypeCtxt( DefaultDeclCtxt ) )
+import TcSimplify	( tcSimplifyDefault )
+import TcType           ( Type, mkClassPred, isTauTy )
+import PrelNames	( numClassName )
+import SrcLoc		( Located(..) )
+import Outputable
 \end{code}
 
 \begin{code}
-tcDefaults :: [RenamedDefaultDecl]
-	   -> TcM s [Type] 	    -- defaulting types to heave
+tcDefaults :: [LDefaultDecl Name]
+	   -> TcM (Maybe [Type])    -- Defaulting types to heave
 				    -- into Tc monad for later use
 				    -- in Disambig.
 
-tcDefaults []
-  = returnTc [intTy, doubleTy] 	    -- language-specified default `default'
+tcDefaults [] 
+  = getDefaultTys		-- No default declaration, so get the
+				-- default types from the envt; 
+				-- i.e. use the curent ones
+				-- (the caller will put them back there)
+	-- It's important not to return defaultDefaultTys here (which
+	-- we used to do) because in a TH program, tcDefaults [] is called
+	-- repeatedly, once for each group of declarations between top-level
+	-- splices.  We don't want to carefully set the default types in
+	-- one group, only for the next group to ignore them and install
+	-- defaultDefaultTys
 
-tcDefaults [DefaultDecl mono_tys locn]
-  = tcAddSrcLoc locn $
-    mapTc tcMonoType mono_tys	`thenTc` \ tau_tys ->
+tcDefaults [L locn (DefaultDecl [])]
+  = returnM (Just [])		-- Default declaration specifying no types
 
-    case tau_tys of
-      [] -> returnTc []		-- no defaults
+tcDefaults [L locn (DefaultDecl mono_tys)]
+  = setSrcSpan locn 			$
+    addErrCtxt defaultDeclCtxt		$
+    tcLookupClass numClassName		`thenM` \ num_class ->
+    mappM tc_default_ty mono_tys	`thenM` \ tau_tys ->
+    
+    	-- Check that all the types are instances of Num
+    	-- We only care about whether it worked or not
+    tcSimplifyDefault [mkClassPred num_class [ty] | ty <- tau_tys]	`thenM_`
+    
+    returnM (Just tau_tys)
 
-      _  ->
-	    -- Check that all the types are instances of Num
-	    -- We only care about whether it worked or not
+tcDefaults decls@(L locn (DefaultDecl _) : _) =
+    setSrcSpan locn $
+    failWithTc (dupDefaultDeclErr decls)
 
-	tcLookupClassByKey numClassKey			`thenNF_Tc` \ num ->
-	tcSimplifyCheckThetas DefaultDeclOrigin
-		[ (num, ty) | ty <- tau_tys ]		`thenTc` \ _ ->
 
-	returnTc tau_tys
+tc_default_ty hs_ty 
+ = tcHsSigType DefaultDeclCtxt hs_ty		`thenM` \ ty ->
+   checkTc (isTauTy ty) (polyDefErr hs_ty)	`thenM_`
+   returnM ty
 
+defaultDeclCtxt =  ptext SLIT("when checking that each type in a default declaration")
+		    $$ ptext SLIT("is an instance of class Num")
+
+
+dupDefaultDeclErr (L _ (DefaultDecl _) : dup_things)
+  = hang (ptext SLIT("Multiple default declarations"))
+      4  (vcat (map pp dup_things))
+  where
+    pp (L locn (DefaultDecl _)) = ptext SLIT("here was another default declaration") <+> ppr locn
+
+polyDefErr ty 
+  = hang (ptext SLIT("Illegal polymorphic type in default declaration") <> colon) 4 (ppr ty) 
 \end{code}
+