Make the method ## have no parameter list (instead of a single empty one)

[dwijnand]

In Dotty, the method ## has no parameter list (instead of having a single empty one), so this aligns Scala 2.13 to that. It would appear calling .##() is highly unlikely so this was changed to error immediately (no warnings).

[eed3si9n]

https://github.com/scala/scala/blob/2.13.x/src/library-aux/scala/Any.scala should be updated together for documentation purpose - scala/bug#5077

[lrytz]

LGTM otherwise! I wonder how breaking this change will be, i.e., how many ##() are out there. Community build will hopefully give us an idea. Maybe we can make a special case in the type checker to allow it with a deprecation warning.

[dwijnand]

CB run: https://scala-ci.typesafe.com/job/scala-2.13.x-integrate-community-build/3318/ (404 while Jenkins goes to make tea.) https://scala-ci.typesafe.com/job/scala-2.13.x-integrate-community-build/3320/

[lrytz]

The community build seems fine. Since ## is final we don't have to worry about overriding. The breaking change is that x.##() no longer compiles. Do we need to worry about this? Intuitively this should affect very few codebases, but unfortunately it's a rough breakage (error, not just a warning).

@SethTisue should we include this in 2.13.2? Scalafix-it?

[SethTisue]

let's roll

@dwijnand would you mind adding a PR description that motivates the change a bit? doesn't need to be extensive, but if we're going to annoy people with a fiddly-seeming change like this, we should say what it's in service of.

[dwijnand]

Scalafix-it?

Done-zo: lightbend-labs/scala-rewrites#16