Tweak to the syntax of extension methods

A small item in Dotty News today: this PR from Martin changes the placement of type parameters when defining extension methods.

Basically, the change is that the type parameter comes first in the declaration. It looks a little odd:

def [T](xs: List[T]) append (ys: List[T]): List[T] = ...

But IMO the arguments given at the link are good ones, and I think the intuition — that you should always declare the type parameter before you use it — makes sense and is teachable. So it’s likely a net positive.

Usual caveats: this is just a PR, not merged to master, much less a Scala 3 SIP. But it makes sense, so I suspect this one has legs; YMMV…