[Haskell-cafe] Infix instance headers

Hello, What's the reason that infix class declarations and infix constraints are supported but infix instance heads aren't? For example the following code from my regions package is allowed but writing the instance header infix results in a "Malformed instance header" error: class (Monad pr, Monad cr) => pr `ParentOf` cr instance Monad r => ParentOf r r instance ( Monad cr , cr `TypeCast2` RegionT resource s pcr , pr `ParentOf` pcr ) => ParentOf pr cr regards, Bas