http://dotty.epfl.ch/docs/reference/contextual/extension-methods.html says: > If an extension method has type parameters, they come immediately after the def and are followed by the extended parameter. But in fact they're also accepted after the method name: ```Scala scala> def (x: A) foo[A]: A = x def foo[A](x: A): A scala> def [A] (x: A) foo: A = x def foo[A](x: A): A ``` @odersky: I assume this is a remnant of a previous syntax and not intentional?