Using shared library steps (vars folder script), in not a call method, when trying to call .next() on a enum Status{}, an exception is thrown:

hudson.remoting.ProxyException: groovy.lang.MissingMethodException: No signature of method: [LStatus;.getAt() is applicable for argument types: (java.lang.Integer) values: [1] Possible solutions: getAt(java.lang.Integer), getAt(groovy.lang.Range), getAt(groovy.lang.EmptyRange), getAt(groovy.lang.ObjectRange), getAt(groovy.lang.IntRange), getAt(java.util.Collection) at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onMethodCall(SandboxInterceptor.java:131)

Steps to reproduce:

1. Create shared library step 
2. declare enum Status with some states
3. define method checkState(){}
4. print Status.next() inside the method checkState(){}

Basically, equivalent of this piece of code that runs normally on https://groovyconsole.appspot.com/ :

enum Status{
    open, indev, developed, deploydev, verified, deploystage, resolved
}
def taskStatus='developed'
print Status."${taskStatus}".next()
RESULT: 
[deploydev]