Context bounds doesn't work sometime

Compiler version

3.1.2

Minimized code

trait Sorting:
  def sort1[A: ClassTag, B >: A: Ordering, CC](
      xs: CC
  )(using view: CC => IterableOnce[A], factory: Factory[A, CC]): CC

  def sort2[A, B >: A: Ordering, CC](
      xs: CC
  )(using view: CC => IterableOnce[A], factory: Factory[A, CC])(using ClassTag[A]): CC

Output

val sorting: Sorting = ...
sorting.sort1(Seq(3, 2, 1))

Will got this compile error:

[error] 48 |    val actual = sorting.sort(input)
[error]    |                                    ^
[error]    |                         No ClassTag available for A
[error]    |
[error]    |                         where:    A is a type variable with constraint

But sort2 works with no problem:

val sorting: Sorting = ...
sorting.sort2(Seq(3, 2, 1))

Expectation

Based on this article, I think sort1 is just the sort2 with syntactic sugar.

Is it a bug or just a misused case?

[odersky]

And we can’t change it, since we need to stay compatible with the way Scala-2 does it.

[odersky]

Note that the current reference doc already describes the actual expansion. It’s just that docs-scala-lang is not updated yet.

https://dotty.epfl.ch/docs/reference/contextual/context-bounds.html