(See https://mail.openjdk.java.net/pipermail/compiler-dev/2019-February/012958.html )

Steps to reproduce: compile and run the following program:

// Test.java
class Test {
  enum A{
    X;
    static { System.out.println("A is initialized!"); }
  }
  enum B{
    Y;
    static { System.out.println("B is initialized!"); }
  }

  static void testA(A a) { switch(a) {} }

  static void testB(B b) { switch(b) {} }

  public static void main(String[] args) {
    testA(A.X);
  }
}

Expected result:

A is initialized!

Actual result:

A is initialized!
B is initialized!

According to JLS 12.4.1 the B enum type should not be initialized, as its fields and methods are not referenced during the program's execution. It appears that the mere declaration of method `testB(B)` is enough to make javac think, wrongly, that B needs to be initialized.