Allow instance heads to use infix syntax

  class C a b
  instance Int `C` Bool

This was accidentally disallowed before.

diff --git a/compiler/parser/RdrHsSyn.lhs b/compiler/parser/RdrHsSyn.lhs
index d18b8d8..746f3d6 100644 (file)
--- a/compiler/parser/RdrHsSyn.lhs
+++ b/compiler/parser/RdrHsSyn.lhs
@@ -549,12 +549,14 @@ checkInstType (L l t)
 checkDictTy :: LHsType RdrName -> P (LHsType RdrName)
 checkDictTy (L spn ty) = check ty []
   where
 checkDictTy :: LHsType RdrName -> P (LHsType RdrName)
 checkDictTy (L spn ty) = check ty []
   where

-  check (HsTyVar t) args | not (isRdrTyVar t) 
-       = return (L spn (HsPredTy (HsClassP t args)))
+  check (HsTyVar tc)            args | isRdrTc tc = done tc args
+  check (HsOpTy t1 (L _ tc) t2) args | isRdrTc tc = done tc (t1:t2:args)

   check (HsAppTy l r) args = check (unLoc l) (r:args)
   check (HsParTy t)   args = check (unLoc t) args
   check _ _ = parseError spn "Malformed instance header"
 
   check (HsAppTy l r) args = check (unLoc l) (r:args)
   check (HsParTy t)   args = check (unLoc t) args
   check _ _ = parseError spn "Malformed instance header"
 

+  done tc args = return (L spn (HsPredTy (HsClassP tc args)))
+

 checkTParams :: Bool     -- Type/data family
             -> [LHsType RdrName]
             -> P ([LHsTyVarBndr RdrName], Maybe [LHsType RdrName])
 checkTParams :: Bool     -- Type/data family
             -> [LHsType RdrName]
             -> P ([LHsTyVarBndr RdrName], Maybe [LHsType RdrName])