FULL PRODUCT VERSION :
java version "1.8.0_40"
Java(TM) SE Runtime Environment (build 1.8.0_40-b25)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
Getting compile error

C.java:2: error: name clash: m() in A1 and m() in B1 have the same erasure, yet neither overrides the other
public abstract class C extends A2 implements B2 {

for the following class/interface constellation :

public interface A1 {
    A1 m();
}
public abstract class A2 implements A1 {
    public abstract A2 m();
}
public interface B1 {
    A1 m();
}
public interface B2 extends B1 {
    A2 m();
}
public abstract class C extends A2 implements B2 {
}


ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_40"
Java(TM) SE Runtime Environment (build 1.8.0_40-b25)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compiling the above classes / interfaces

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
compile without any errors
ACTUAL -
C.java:2: error: name clash: m() in A1 and m() in B1 have the same erasure, yet neither overrides the other
public abstract class C extends A2 implements B2 {


ERROR MESSAGES/STACK TRACES THAT OCCUR :
C.java:2: error: name clash: m() in A1 and m() in B1 have the same erasure, yet neither overrides the other
public abstract class C extends A2 implements B2 {


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public interface A1 {
A1 m();
}
public abstract class A2 implements A1 {
public abstract A2 m();
}
public interface B1 {
A1 m();
}
public interface B2 extends B1 {
A2 m();
}
public abstract class C extends A2 implements B2 {
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
public abstract class C extends A2 implements B2 {
public abstract A2 m();
}