[SOLVED] Why does this program no longer compile in Java 8 with "cannot infer type arguments"?

Why does this program no longer compile in Java 8 with "cannot infer type arguments"?

This program compiles fine in Java 7 (or in Java 8 with -source 7), but fails to compile with Java 8:

interface Iface<T> {}
class Impl implements Iface<Impl> {}

class Acceptor<T extends Iface<T>> {
    public Acceptor(T obj) {}
}

public class Main {
    public static void main(String[] args) {
        Acceptor<?> acceptor = new Acceptor<>(new Impl());
    }
}

Result:

Main.java:10: error: incompatible types: cannot infer type arguments for Acceptor<>
        Acceptor<?> acceptor = new Acceptor<>(new Impl());
                                           ^
    reason: inference variable T has incompatible bounds
      equality constraints: Impl
      upper bounds: Iface<CAP#1>,Iface<T>
  where T is a type-variable:
    T extends Iface<T> declared in class Acceptor
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Iface<CAP#1> from capture of ?
1 error

In other words, this is a backwards source incompatibility between Java 7 and 8. I've gone through the Incompatibilities between Java SE 8 and Java SE 7 list but did not found anything that would fit my problem.

So, is this a bug?

Environment:

$ /usr/lib/jvm/java-8-oracle/bin/java -version
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)

Solution

Thanks for the report. This looks like a bug. I will take care of it and probably add a better answer once we have more information about why this is happening. I have filed this bug entry JDK-8043926, to track it.