[project @ 1999-02-04 13:45:24 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcDefaults.lhs

diff --git a/ghc/compiler/typecheck/TcDefaults.lhs b/ghc/compiler/typecheck/TcDefaults.lhs
index 0b9a66b..6fe697b 100644 (file)
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -1,38 +1,31 @@
 %
-% (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
 
-IMP_Ubiq()
+#include "HsVersions.h"
 
-import HsSyn           ( HsDecl(..), TyDecl, ClassDecl, InstDecl, HsBinds,
-                         DefaultDecl(..), HsType, IfaceSig,
-                         HsExpr, HsLit, ArithSeqInfo, Fake, InPat)
-import RnHsSyn         ( RenamedHsDecl(..), RenamedDefaultDecl(..) )
-import TcHsSyn         ( TcIdOcc )
+import HsSyn           ( HsDecl(..), DefaultDecl(..) )
+import RnHsSyn         ( RenamedHsDecl )
 
 import TcMonad
-import Inst            ( InstOrigin(..) )
 import TcEnv           ( tcLookupClassByKey )
-import SpecEnv         ( SpecEnv )
 import TcMonoType      ( tcHsType )
 import TcSimplify      ( tcSimplifyCheckThetas )
 
-import TysWiredIn      ( intTy, doubleTy, unitTy )
-import Type             ( SYN_IE(Type) )
+import TysWiredIn      ( integerTy, doubleTy )
+import Type             ( Type )
 import Unique          ( numClassKey )
-import Pretty          ( ptext, vcat )
 import ErrUtils                ( addShortErrLocLine )
+import Outputable
 import Util
 \end{code}
 
 \begin{code}
-default_default = [intTy, doubleTy]        -- language-specified default `default'
+default_default = [integerTy, doubleTy ]
 
 tcDefaults :: [RenamedHsDecl]
           -> TcM s [Type]          -- defaulting types to heave
@@ -53,25 +46,26 @@ tc_defaults [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 ->
+       tcAddErrCtxt defaultDeclCtxt            $
+       tcLookupClassByKey numClassKey          `thenNF_Tc` \ num ->
        tcSimplifyCheckThetas
-               [ (num, ty) | ty <- tau_tys ]           `thenTc_`
+               [{- Nothing given -}]
+               [ (num, [ty]) | ty <- tau_tys ] `thenTc_`
 
        returnTc tau_tys
 
-tc_defaults decls
-  = failTc (dupDefaultDeclErr decls)
+tc_defaults decls@(DefaultDecl _ loc : _) =
+    tcAddSrcLoc loc $
+    failWithTc (dupDefaultDeclErr decls)
 
 
-dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things) sty
-  = vcat (item1 : map dup_item dup_things)
-  where
-    item1
-      = addShortErrLocLine locn1 (\ sty ->
-       ptext SLIT("multiple default declarations")) sty
+defaultDeclCtxt =  ptext SLIT("when checking that each type in a default declaration")
+                   $$ ptext SLIT("is an instance of class Num")
 
-    dup_item (DefaultDecl _ locn)
-      = addShortErrLocLine locn (\ sty ->
-       ptext SLIT("here was another default declaration")) sty
 
+dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things)
+  = hang (ptext SLIT("Multiple default declarations"))
+      4  (vcat (map pp dup_things))
+  where
+    pp (DefaultDecl _ locn) = ptext SLIT("here was another default declaration") <+> ppr locn
 \end{code}