Imported From: https://issues.scala-lang.org/browse/SI-9523?orig=1
Reporter: Michael Pollmeier (pollmeier)
Affected Versions: 2.11.7, 2.12.0-M3

Michael Pollmeier (pollmeier) said:
Typer debug output

Another example I think: http://stackoverflow.com/questions/43402995/implicit-conversion-is-not-applied-if-generics-are-present

implicit def CToC2(obj: C1): C2 = {
  new C2()
}

class C1() {
  def f[U](i: Int): Unit = ???
}

class C2() {
  def f(s: String): Unit = ???
}

val c1 = new C1()
c1.f("a")    // error: type mismatch; found: String("a") required: Int

Remove type parameter U and it works.

Or

val zip = (List(1, 3, 5), List(2, 4, 6)).zipped
val f: ((Int, Int)) => Unit = x => println(x._1 + x._2)
zip.foreach(f)

which should work, since the std lib contains a conversion for this purpose: https://github.com/scala/scala/blob/v2.12.1/src/library/scala/runtime/Tuple2Zipped.scala#L31

#11232 is a recent duplicate. PR with fix: scala/scala#7396

I won't have time to get this fix over the finish line for RC1. Tentatively scheduled for 2.13.1, but it may have to be 2.14 if it turns out too breaking of a change.

This has cropped up in a slightly different form for me too: https://users.scala-lang.org/t/error-in-method-resolution-between-core-method-and-pseudo-overload-in-syntax-helper/7102 .

In this case, the type parameter on the method provided by the syntax enhancement is used in the argument signature, but still fails to unify with the actual argument.

To make matters more interesting, the same problem happens in reverse if the method in the core class has the type parameter and the one in the syntax enhancement doesn't. Again, this occurs even if the core class's method actually uses the type parameter in the argument signature.