X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fparser%2FParser.y.pp;h=f72c8b9d83f46b2085b40957b5662ba61a73ce8f;hb=3ded6e65b730c2b5eb9a9519448bbcd905c5d7fa;hp=009eddca6281abcd815386a4515deccc9c171b85;hpb=d386e0d20c6953b7cba4d53538a1782c4aa9980d;p=ghc-hetmet.git

diff --git a/compiler/parser/Parser.y.pp b/compiler/parser/Parser.y.pp
index 009eddc..f72c8b9 100644
--- a/compiler/parser/Parser.y.pp
+++ b/compiler/parser/Parser.y.pp
@@ -971,8 +971,13 @@ ctype	:: { LHsType RdrName }
 -- errors in ctype.  The basic problem is that
 --	(Eq a, Ord a)
 -- looks so much like a tuple type.  We can't tell until we find the =>
+--
+-- We have the t1 ~ t2 form here and in gentype, to permit an individual
+-- equational constraint without parenthesis.
 context :: { LHsContext RdrName }
-	: btype 			{% checkContext $1 }
+        : btype '~'      btype  	{% checkContext
+					     (LL $ HsPredTy (HsEqualP $1 $3)) }
+	| btype 			{% checkContext $1 }
 
 type :: { LHsType RdrName }
 	: ipvar '::' gentype		{ LL (HsPredTy (HsIParam (unLoc $1) $3)) }
@@ -983,7 +988,7 @@ gentype :: { LHsType RdrName }
         | btype qtyconop gentype        { LL $ HsOpTy $1 $2 $3 }
         | btype tyvarop  gentype  	{ LL $ HsOpTy $1 $2 $3 }
  	| btype '->'     ctype		{ LL $ HsFunTy $1 $3 }
-        | btype '~'      gentype  	{ LL $ HsPredTy (HsEqualP $1 $3) }
+        | btype '~'      btype  	{ LL $ HsPredTy (HsEqualP $1 $3) }
 
 btype :: { LHsType RdrName }
 	: btype atype			{ LL $ HsAppTy $1 $2 }