In a declarative pipeline, we have some parallel steps. On start of a build, the user should be able to decide whether the steps should fail fast or not.

Thus, we introduced a boolean parameter "FAIL_FAST" and used it in the step like this:

stage('Smoke Test') {
    failFast params.FAIL_FAST
    parallel {
        ...

However, that led to following exception:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
WorkflowScript: 196: Expected a boolean with failFast @ line 196, column 7.
     failFast params.FAIL_FAST
     ^

It should be possible to use variables at this point.