Unclear error message in enums

In enumerations, the enum elements are implicitly assigned, leading to an unintuitive error. Consider this enum,

import org.checkerframework.checker.tainting.qual.*;

public enum C {
    @Untainted A
}

When I run javac -processor TaintingChecker C.java I get the error,

C.java:4: error: [assignment.type.incompatible] incompatible types in assignment.
    @Untainted A
               ^
  found   : @Tainted C
  required: @Untainted C

The error is that A is actually a field which is assigned to a default constructed instance of C, which is Tainted. However, there's no explicit assignment in the code so without knowledge of how Java implements enums this error is confusing.

When enum fields are set to invalid values, it should be clear that it's because they're implicitly being assigned to a newly constructed value. Perhaps add a different error name for invalid assignments in enums.