Regression in estrondo/farango

[WojciechMazur]

Open CB regression found in estrondo/farango - build logs

Compiler version

3.3.1-RC1-bin-20230515-22b2259-NIGHTLY
3.3.1-RC4

Bisect points to d1d6c2e

Minimized code

import scala.collection.Factory

trait EffectStream[S[_]]:
  def fromJavaStream[A]: S[A]

given [I[_] <: Iterable[_]](using Factory[Any, I[Any]]): EffectStream[I] with
  override def fromJavaStream[A]: I[A] = {
    val builder = summon[Factory[_, I[_]]].newBuilder
    ???
  }

Output

-- [E043] Type Error: /Users/wmazur/projects/dotty/bisect/main.scala:8:36 ------
8 |    val builder = summon[Factory[_, I[_]]].newBuilder
  |                                    ^^^^
  |     unreducible application of higher-kinded type I to wildcard arguments
  |
  | longer explanation available when compiling with `-explain`

Expectation

Probably should compile

[WojciechMazur]

The bisected commit was fixing #17168
@odersky is it actually typer improvement, and not a regression?

[dwijnand]

Yeah, it's not a regression. I'm not sure about the original, but to me it looks like it should be summon[Factory[Any, I[Any]]].newBuilder.

(Edit) yeah in the original as well.

[odersky]

If I understood Dale correctly, it looks like an error in the program that is now correctly diagnosed.