When compiling with -Xcheckinit, the compiler-generated bitmap field(s) are not marked synthetic. For example:

$ ~/Programs/scala-2.11.7/bin/scala -Xcheckinit
Welcome to Scala version 2.11.7 (OpenJDK 64-Bit Server VM, Java 1.8.0_51).
Type in expressions to have them evaluated.
Type :help for more information.

scala> final class Foo(constant: Double) { val value: Double = constant }
defined class Foo

scala> classOf[Foo].getDeclaredFields
res0: Array[java.lang.reflect.Field] = Array(private final double Foo.value, private volatile boolean Foo.bitmap$init$0)

scala> res0.last.isSynthetic
res1: Boolean = false

This may cause a problem for reflection-based tools that specifically must ignore synthetic fields for correctness (e.g. see this thread related to the EqualsVerifier library).

A similar issue was raised on the scala-internals mailing list last year, and there seemed to be agreement that such compiler-generated bitmap fields should be marked synthetic. However, I was unable to find an associated issue in JIRA.