companion extension method not found for opaque type

Compiler version

v3.1.0-RC1

Minimized code

opaque type Foo[T] = Int
object Foo:
  extension [T](f: Foo[T]) def foo: Int = 1

def bar[T](f: Foo[T]): Unit =
  val x = f.foo

Output

value foo is not a member of Foo[T], but could be made available as an extension method.

Expectation

No error.

[odersky]

But it works if I put the whole thing in an object. So there’s still something wrong with the toplevel scope here.

object O:
  opaque type Foo[T] = Int
  object Foo:
    extension [T](f: Foo[T]) def foo: Int = 1

import O.*
def bar[T](f: Foo[T]): Unit =
  val x = f.foo

[soronpo]

OK, I’ll submit a PR for the docs.