Regression in typer method dispatch when using context bounds with ClassTag of function

[WojciechMazur]

Compiler version

3.3.1-RC1-nighlty

Last good release: 3.3.1-RC1-bin-20230302-8020c77-NIGHTLY
First bad release: 3.3.1-RC1-bin-20230303-6ad22aa-NIGHTLY

The commit-based bisect for range of commits 8020c77..6ad22aa failed due to other failures.

Minimized code

Based on Open CB failures in pjfanning/akka-rabbitmq, compilation logs can be found here: https://github.com/VirtusLab/community-build3/actions/runs/4650721329/jobs/8229907414

import scala.reflect.ClassTag

trait MockSettings

object Mockito {
  def mock[T : ClassTag]: T = ???
  def mock[T : ClassTag](settings: MockSettings): T = ??? 
}

trait Channel 
type OnChannel = Channel => Any

@main def Test =
  val fail1: OnChannel = Mockito.mock[OnChannel] // fails
  val fail2: OnChannel = Mockito.mock // fails

  val workaround1 = Mockito.mock[OnChannel]  // compiles
  val workaround2: OnChannel =  Mockito.mock[OnChannel](summon[ClassTag[OnChannel]]) // compiles  

Output

-- [E134] Type Error: /workspace/dotty/bisect/main.scala:14:33 -----------------
14 |  val fail1: OnChannel = Mockito.mock[OnChannel] // fails
   |                         ^^^^^^^^^^^^
   |None of the overloaded alternatives of method mock in object Mockito with types
   | [T](settings: MockSettings)(implicit evidence$2: reflect.ClassTag[T]): T
   | [T](implicit evidence$1: reflect.ClassTag[T²]): T²
   |match type arguments [OnChannel] and expected type OnChannel
   |
   |where:    T  is a type variable
   |          T² is a type variable
-- [E134] Type Error: /workspace/dotty/bisect/main.scala:15:33 -----------------
15 |  val fail2: OnChannel = Mockito.mock // fails
   |                         ^^^^^^^^^^^^
   |None of the overloaded alternatives of method mock in object Mockito with types
   | [T](settings: MockSettings)(implicit evidence$2: reflect.ClassTag[T]): T
   | [T](implicit evidence$1: reflect.ClassTag[T²]): T²
   |match expected type OnChannel
   |
   |where:    T  is a type variable
   |          T² is a type variable
2 errors found

Expectation

Compiler should pick def mock[T : ClassTag]: T and allow for compilation

[Kordyjan]

According to bisect, it was broken by #16507
@natsukagami, @nicolasstucki, what do you think?

[nicolasstucki]

It might be due to an unintended change with MethodTypes or function types.