FULL PRODUCT VERSION :
On CentOS

java version "1.8.0_112"
Java(TM) SE Runtime Environment (build 1.8.0_112-b15)
Java HotSpot(TM) 64-Bit Server VM (build 25.112-b15, mixed mode)

On OSX, tested both

java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)

and

jopenjdk version "9-internal"
OpenJDK Runtime Environment (build 9-internal+0-2016-08-03-125324.jsailor.jdk9)
OpenJDK 64-Bit Server VM (build 9-internal+0-2016-08-03-125324.jsailor.jdk9, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux devbig340.prn1.facebook.com 4.0.9-68_fbk12_4058_gd84fdb3 #1 SMP Fri Aug 26 15:02:40 PDT 2016 x86_64 x86_64 x86_64 GNU/Linux
CentOS Linux release 7.3.1611 (Core)

also

Darwin karkat 16.3.0 Darwin Kernel Version 16.3.0: Thu Nov 17 20:23:58 PST 2016; root:xnu-3789.31.2~1/RELEASE_X86_64 x86_64
ProductName: Mac OS X
ProductVersion: 10.12.2
BuildVersion: 16C67


A DESCRIPTION OF THE PROBLEM :
The JLS forbids references to enum constants from within instance variable initializers of the same enum type. However, javac improperly allows such references if they occur inside a nested class in the instance variable initializer. See:


JLS 8.9.2 https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.9.2

It is a compile-time error to reference a static field of an enum type from constructors, instance initializers, or instance variable initializer expressions of the enum type, unless the field is a constant variable (§4.12.4).

JLS 8.9.3 https://docs.oracle.com/javase/specs/jls/se8/html/jls-8.html#jls-8.9.3

The members of an enum type E are all of the following:
…
For each enum constant c declared in the body of the declaration of E, E has an implicitly declared public static final field of type E that has the same name as c. The field has a variable initializer consisting of c, and is annotated by the same annotations as c.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Compile code below with `javac Main.java`

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
An error from javac along the lines of:


Main.java:6: error: illegal reference to static field from initializer
        add(FOO);
1 error

ACTUAL -
Code compiles, runs, and prints "[null]"


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
  import java.util.HashSet;
  public class Main {
    public enum Bleh {
      FOO;
      public HashSet<Bleh> vals = new HashSet<Bleh>(){{
        add(FOO);
      }};
    }
    
    public static void main(String[] args) {
      System.out.println(Bleh.FOO.vals);
    }
  }

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