Scala compiler fails choosing method overload

[scabug]

Having the following Java interfaces:

public interface Promise<T> {
  <R> Promise<R> map(SuccessHandler<? super T, ? extends R> handler);
  <R> Promise<R> map(FutureSuccessHandler<? super T, R> handler);
}

public interface SuccessHandler<T, R> {
  R handle(T result);
}

public interface FutureSuccessHandler<T,R> {
  Promise<R> handle(T result);
}

Where Promise#map method contains two overloads, receiving two different interfaces and using bounded wildcards, Scala fails to choose which overload to use having the following code:

object Test {
  val promise: Promise[String] = ???
  promise.map(new SuccessHandler[String, Int] {
    override def handle(result: String): Int = ???
  })
}

Failing on compilation error:

(Using directly scalac and providing classpath):

Test.scala:9: error: overloaded method value map with alternatives:
  [R](x$1: test.FutureSuccessHandler[_ >: String, R])test.Promise[R] <and>
  [R](x$1: test.SuccessHandler[_ >: String, _ <: R])test.Promise[R]
 cannot be applied to (test.SuccessHandler[String,Int])
  promise.map(new SuccessHandler[String, Int] {
          ^
one error found

(Using Maven with scala-maven-plugin):

[INFO] Using incremental compilation
[INFO] Compiling 1 Scala sources and 3 Java sources to /home/michael/ScalaTest/target/classes...
[ERROR] /home/michael/ScalaTest/src/main/scala/test/Test.scala:9: overloaded method value map with alternatives:
  [R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)](handler: test.FutureSuccessHandler[_ >: String, R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)])test.Promise[R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)] <and>
  [R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)](handler: test.SuccessHandler[_ >: String, _ <: R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)])test.Promise[R(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)(in method map)]
 cannot be applied to (test.SuccessHandler[String,Int])
[ERROR]   promise.map(new SuccessHandler[String, Int] {
[ERROR]           ^
[ERROR] one error found

Now, interesting things about the issue:

1. Having this line: 'promise.map(new SuccessHandler[String, Int]', changing the parameter type R to be also String (instead of Int), leads the code to compile successfully (when 'SuccessHandler' generic types are the same, all works fine).
2. Signatures of the 'map' methods containing bounded wildcard as defined below:

<R> Promise<R> map(SuccessHandler<? super T, ? extends R> handler);
<R> Promise<R> map(FutureSuccessHandler<? super T, R> handler);

if I remove the lower bounded wildcards (from both methods) everything compiles without any issues.
The issue looks like caused by the wildcards, but have no idea more why.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9901?orig=1
Reporter: Michael (marenzo)
Affected Versions: 2.11.7
Attachments:

• source.zip (created on Aug 23, 2016 8:45:26 PM UTC, 1645 bytes)

[scabug]

@som-snytt said:
Without the overload:

.\src\main\scala\test\Test.scala:5: error: no type parameters for method map: (x$1: test.SuccessHandler[_ >: String, _ <: R])test.Promise[R] exist so that it can be applied to arguments (test.SuccessHandler[String,Int])
 --- because ---
argument expression's type is not compatible with formal parameter type;
 found   : test.SuccessHandler[String,Int]
 required: test.SuccessHandler[_ >: String, _ <: ?R]
Note: String <: Any, but Java-defined trait SuccessHandler is invariant in type T.
You may wish to investigate a wildcard type such as `_ <: Any`. (SLS 3.2.10)
  promise.map(new SuccessHandler[String, Int] {
          ^
.\src\main\scala\test\Test.scala:5: error: type mismatch;
 found   : test.SuccessHandler[String,Int]
 required: test.SuccessHandler[_ >: String, _ <: R]
  promise.map(new SuccessHandler[String, Int] {
              ^
two errors found

[som-snytt]

Fails in 2.12.20, compiles in 2.13.x, separate and mixed. Still OK in 3.5.2.

[[syntax trees at end of                     typer]] // Test.scala
package <empty> {
  object Test extends AnyRef with App {
    def <init>(): Test.type = {
      Test.super.<init>();
      ()
    };
    def f(promise: Promise[String]): Promise[Int] = promise.map[Int]({
      final class $anon extends Object with SuccessHandler[String,Int] {
        def <init>(): <$anon: SuccessHandler[String,Int]> = {
          $anon.super.<init>();
          ()
        };
        override def handle(result: String): Int = 42
      };
      new $anon()
    })
  }
}