Argument types are erroneously inferred as Nothing when a method is explicitly eta-expanded as in f(_)

[neko-kai]

Compiler version

3.2.1 and 3.2.2-RC1

Minimized code

Runnable: https://scastie.scala-lang.org/WNexehduQzOT4XJ2XfUB7Q

import scala.compiletime.summonInline

case class TypeDesc[T](tpe: String)
object TypeDesc {
  given TypeDesc[Nothing] = TypeDesc("Nothing")
  given TypeDesc[String] = TypeDesc("String")
  given TypeDesc[Int] = TypeDesc("Int")
}

def exampleFn(s: String, i: Int): Unit = ()

inline def argumentTypesOf[R](fun: (?, ?) => R): (TypeDesc[?], TypeDesc[?]) = {
  inline fun match {
    case x: ((a, b) => R) =>
      (summonInline[TypeDesc[a]], summonInline[TypeDesc[b]])
  }
}

inline def argumentTypesOfNoWildCard[A, B, R](fun: (A, B) => R): (TypeDesc[?], TypeDesc[?]) = argumentTypesOf(fun)

inline def argumentTypesOfAllWildCard(fun: (?, ?) => ?): (TypeDesc[?], TypeDesc[?]) = argumentTypesOf(fun)

@main def main: Unit = {
  println(argumentTypesOf(exampleFn)) // good
  println(argumentTypesOf(exampleFn(_, _))) // bad
  println(argumentTypesOfNoWildCard(exampleFn(_, _))) // good
  println(argumentTypesOfAllWildCard(exampleFn)) // bad, even without explicit placeholders
}

Output

(TypeDesc(String),TypeDesc(Int))
(TypeDesc(Nothing),TypeDesc(Nothing))
(TypeDesc(String),TypeDesc(Int))
(TypeDesc(Nothing),TypeDesc(Nothing))

Expectation

(TypeDesc(String),TypeDesc(Int))
(TypeDesc(String),TypeDesc(Int))
(TypeDesc(String),TypeDesc(Int))
(TypeDesc(String),TypeDesc(Int))

Expected there to be no difference between exampleFn and exampleFn(_, _) form in type inference in general and when calling argumentTypesOf.
Expected all variants of argumentTypesOf* to not infer Nothing regardless of using wildcards anywhere in the parameter type.

This code is a minimized version of real library code in https://github.com/izumi/izumi which we're trying to port to Scala 3

[szymon-rd]

Thank you for reporting and minimization!