The following Jenkinsfile snippet shows the fully quallified usage of an imported Type within an `expression` block. The whole Jenkinsfile can be executed without a failure.

```groovy

@Library('SomeManagedLibID') _
import some.package.MyType
[...]
stages {
  stage('Foobar') {
    when {
      expression {
        def xyz = new some.package.MyType()
        [...]
      }
```

Whereas the second snippet uses the short name (because it is imported) ...

```groovy

@Library('SomeManagedLibID') _
import some.package.MyType
[...]
stages {
  stage('Foobar') {
    when {
      expression {
        def xyz = new MyType()
        [...]
      }
```

... but in this case, the execution fails with a ProxyException:

```
Bitbucket] Build result notified
hudson.remoting.ProxyException: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Script2.groovy: 2: unable to resolve class MyType
@ line 2, column 10.
def cg = new MyType()
^

1 error

at org.codehaus.groovy.control.ErrorCollector.failIfErrors(ErrorCollector.java:310)
at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(CompilationUnit.java:958)
at org.codehaus.groovy.control.CompilationUnit.doPhaseOperation(CompilationUnit.java:605)
at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:554)
at groovy.lang.GroovyClassLoader.doParseClass(GroovyClassLoader.java:298)
at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:268)
at groovy.lang.GroovyShell.parseClass(GroovyShell.java:688)
at groovy.lang.GroovyShell.parse(GroovyShell.java:700)
at org.jenkinsci.plugins.workflow.cps.CpsGroovyShell.parse(CpsGroovyShell.java:55)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:584)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:623)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:594)
at org.jenkinsci.plugins.workflow.cps.CpsScript.evaluate(CpsScript.java:167)
at org.jenkinsci.plugins.workflow.cps.CpsScript$evaluate.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:113)
at com.cloudbees.groovy.cps.sandbox.DefaultInvoker.methodCall(DefaultInvoker.java:18)
at org.jenkinsci.plugins.pipeline.modeldefinition.when.impl.ExpressionConditionalScript.evaluate(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/when/impl/ExpressionConditionalScript.groovy:43)
at org.jenkinsci.plugins.pipeline.modeldefinition.when.impl.AllOfConditionalScript.evaluate(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/when/impl/AllOfConditionalScript.groovy:44)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.evaluateWhen(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:420)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.call(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:95)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:223)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.withEnvBlock(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:222)
at org.jenkinsci.plugins.pipeline.modeldefinition.ModelInterpreter.call(jar:file:/var/jenkins_home/plugins/pipeline-model-definition/WEB-INF/lib/pipeline-model-definition.jar!/org/jenkinsci/plugins/pipeline/modeldefinition/ModelInterpreter.groovy:94)
at __cps.transform__(Native Method)
at com.cloudbees.groovy.cps.impl.ContinuationGroup.methodCall(ContinuationGroup.java:57)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.dispatchOrArg(FunctionCallBlock.java:109)
at com.cloudbees.groovy.cps.impl.FunctionCallBlock$ContinuationImpl.fixArg(FunctionCallBlock.java:82)
at sun.reflect.GeneratedMethodAccessor330.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.LocalVariableBlock$LocalVariable.get(LocalVariableBlock.java:39)
at com.cloudbees.groovy.cps.LValueBlock$GetAdapter.receive(LValueBlock.java:30)
at com.cloudbees.groovy.cps.impl.LocalVariableBlock.evalLValue(LocalVariableBlock.java:28)
at com.cloudbees.groovy.cps.LValueBlock$BlockImpl.eval(LValueBlock.java:55)
at com.cloudbees.groovy.cps.LValueBlock.eval(LValueBlock.java:16)
at com.cloudbees.groovy.cps.Next.step(Next.java:74)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:154)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:18)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:33)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable$1.call(SandboxContinuable.java:30)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:108)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:30)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:165)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:328)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$100(CpsThreadGroup.java:80)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:240)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:228)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:64)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:112)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Finished: FAILURE
```
It looks like the `expression` does allow to execute groovy code but does not see the imported types.