3.3.0-RC5 -Wunused:imports false positive for imports that "shadow" other imports

[Lasering]

Compiler version

3.3.0-RC5 with -Wunused:imports flag on.

Minimized code

trait Circular[T] extends Ordering[T]
trait Turns[C: Circular, T] extends Ordering[T]:
  extension (turns: T)
    def extract: C

def foo[K, T](start: T, end: T)(using circular: Circular[K], turns: Turns[K, T]): Boolean =
  import turns.given
  if start > end then throw new IllegalArgumentException("start must be <= end")
  
  import circular.given
  start.extract < end.extract

Output

 10 |    import turns.given
    |                 ^^^^^
    |                 unused import

Expectation

No warning should be emitted.

[KacperFKorban]

Minimized a bit to use less language features:

//> using scala "3.3.0-RC5"
//> using options "-Wunused:all"

class A
class B

def Test() =
  val ordA: Ordering[A] = ???
  val ordB: Ordering[B] = ???
  val a: A = ???
  val b: B = ???

  import ordA.given
  val _ = a > a
  
  import ordB.given // warn: Unused
  val _ = b < b

Output:

-- Warning: i17371.scala:16:14 ----------------------------------
16 |  import ordB.given // warn: Unused
   |              ^^^^^
   |              unused import

[odersky]

I have no idea why this one behaves as it does. If we adopt the strategy "an import is used if code refers to some of its imported symbols" this should compile without warning, since mkOrderingOps is selected from ordB.

[som-snytt]

This is the first issue addressed on the linked PR: mkOrderingOps is selected from both imports, albeit with different prefixes.

You might expect the code to use the nearest enclosing import context in that case, but contexts are broken in this context.