[project @ 1996-12-19 09:10:02 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 066f90e..bb0557d 100644 (file)
--- a/ghc/compiler/typecheck/TcDefaults.lhs
+++ b/ghc/compiler/typecheck/TcDefaults.lhs
@@ -10,35 +10,40 @@ module TcDefaults ( tcDefaults ) where
 
 IMP_Ubiq()
 
-import HsSyn           ( DefaultDecl(..), MonoType,
+import HsSyn           ( HsDecl(..), TyDecl, ClassDecl, InstDecl, HsBinds,
+                         DefaultDecl(..), HsType, IfaceSig,
                          HsExpr, HsLit, ArithSeqInfo, Fake, InPat)
-import RnHsSyn         ( RenamedDefaultDecl(..) )
+import RnHsSyn         ( RenamedHsDecl(..), RenamedDefaultDecl(..) )
 import TcHsSyn         ( TcIdOcc )
 
-import TcMonad         hiding ( rnMtoTcM )
+import TcMonad
 import Inst            ( InstOrigin(..) )
 import TcEnv           ( tcLookupClassByKey )
 import SpecEnv         ( SpecEnv )
-import TcMonoType      ( tcMonoType )
+import TcMonoType      ( tcHsType )
 import TcSimplify      ( tcSimplifyCheckThetas )
 
 import TysWiredIn      ( intTy, doubleTy, unitTy )
 import Unique          ( numClassKey )
+import Pretty          ( ppStr, ppAboves )
+import ErrUtils                ( addShortErrLocLine )
 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
@@ -53,4 +58,19 @@ tcDefaults [DefaultDecl mono_tys locn]
 
        returnTc tau_tys
 
+tc_defaults decls
+  = failTc (dupDefaultDeclErr decls)
+
+
+dupDefaultDeclErr (DefaultDecl _ locn1 : dup_things) sty
+  = ppAboves (item1 : map dup_item dup_things)
+  where
+    item1
+      = addShortErrLocLine locn1 (\ sty ->
+       ppStr "multiple default declarations") sty
+
+    dup_item (DefaultDecl _ locn)
+      = addShortErrLocLine locn (\ sty ->
+       ppStr "here was another default declaration") sty
+
 \end{code}