Fix Trac #3013: multiple constructors in a GADT decl

[ghc-hetmet.git] / compiler / parser / RdrHsSyn.lhs

diff --git a/compiler/parser/RdrHsSyn.lhs b/compiler/parser/RdrHsSyn.lhs
index 187d64d..3ca1b29 100644 (file)
--- a/compiler/parser/RdrHsSyn.lhs
+++ b/compiler/parser/RdrHsSyn.lhs
@@ -28,7 +28,7 @@ module RdrHsSyn (
                              -- -> (FastString, RdrName, RdrNameHsType)
                              -- -> P RdrNameHsDecl
        mkExtName,           -- RdrName -> CLabelString
-       mkGadtDecl,          -- Located RdrName -> LHsType RdrName -> ConDecl RdrName
+       mkGadtDecl,          -- [Located RdrName] -> LHsType RdrName -> ConDecl RdrName
                              
        -- Bunch of functions in the parser monad for 
        -- checking and constructing values
@@ -813,11 +813,19 @@ checkValSig (L l (HsVar v)) ty
 checkValSig (L l _)         _
   = parseError l "Invalid type signature"
 
-mkGadtDecl :: Located RdrName
+mkGadtDecl :: [Located RdrName]
            -> LHsType RdrName -- assuming HsType
-           -> ConDecl RdrName
-mkGadtDecl name (L _ (HsForAllTy _ qvars cxt ty)) = mk_gadt_con name qvars cxt ty
-mkGadtDecl name ty                               = mk_gadt_con name [] (noLoc []) ty
+           -> [ConDecl RdrName]
+-- We allow C,D :: ty
+-- and expand it as if it had been 
+--    C :: ty; D :: ty
+-- (Just like type signatures in general.)
+mkGadtDecl names ty
+  = [mk_gadt_con name qvars cxt tau | name <- names]
+  where
+    (qvars,cxt,tau) = case ty of
+                       L _ (HsForAllTy _ qvars cxt tau) -> (qvars, cxt,      tau)
+                       _                                -> ([],    noLoc [], ty)
 
 mk_gadt_con :: Located RdrName
             -> [LHsTyVarBndr RdrName]