Method <org.gradle.api.Project.allprojects(groovy.lang.Closure)> has arguments/return type groovy.lang.Closure that is not Gradle public API or primitive or built-in JDK classes or Kotlin classes in (Project.java:0)

    public void beforeEvaluate(Closure closure) {
        assertMutatingMethodAllowed("beforeEvaluate(Closure)");
        evaluationListener.add(new ClosureBackedMethodInvocationDispatch("beforeEvaluate", getListenerBuildOperationDecorator().decorate("Project.beforeEvaluate", Cast.<Closure<?>>uncheckedNonnullCast(closure))));
    }

    @Override
    public void afterEvaluate(Closure closure) {

    /**
     * <p>Adds a closure to call immediately before this project is evaluated.</p>
     *
     * @see Project#beforeEvaluate(Action)
     *
     * @param closure The closure to call.
     */
    void beforeEvaluate(Closure closure);

    /**
     * <p>Adds a closure to call immediately after this project is evaluated.</p>
     *

    @Override
    public DomainObjectContext getDomainObjectContext() {
        return domainObjectContext;
    }

    @Override
    public Configuration resolutionStrategy(Closure closure) {
        configure(closure, getResolutionStrategy());
        return this;
    }

    @Override
    public Configuration resolutionStrategy(Action<? super ResolutionStrategy> action) {

include::sample[dir="snippets/files/fileCollections/groovy",files="build.gradle[tags=closure]"]
====

----
$ gradle -q list
include::{snippetsPath}/files/fileCollections/tests/fileCollectionsWithClosure.out[]
----

The key to lazy creation is passing a closure (in Groovy) or a `Provider` (in Kotlin) to the `files()` method.

    }

    def fileCollectionWithClosureSpec() {
        def closure = { dep -> dep.group == 'group1' }
        def configuration = conf()
        def fileSet = [new File("somePath")] as Set
        resolver.resolveGraph(configuration) >> graphResolved(fileSet)

        when:
        def fileCollection = configuration.fileCollection(closure)

        then:
        fileCollection.files == fileSet

				st.advance(1)
				st.fail("expected closure or unnamed type")
			}
			c := st.str[1]
			switch c {
			case 'b':
				st.advance(2)
				st.compactNumber()
				a = &Name{Name: "'block-literal'"}
			case 'l':
				a = st.closureTypeName()
			case 't':
				a = st.unnamedTypeName()
			default:
				st.advance(1)
				st.fail("expected closure or unnamed type")
			}
		default:

=== Groovy closures from Kotlin

You may sometimes have to call Groovy methods that take link:https://groovy-lang.org/closures.html[Closure] arguments from Kotlin code.
For example, some third-party plugins written in Groovy expect closure arguments.

On link:{javadocPath}/org/gradle/api/artifacts/Configuration.html--[Configuration]:

- `files(Dependency...)`
- `files(Spec)`
- `files(Closure)`
- `fileCollection(Dependency...)`
- `fileCollection(Spec)`
- `fileCollection(Closure)`

On link:{javadocPath}/org/gradle/api/artifacts/ResolvedConfiguration.html--[ResolvedConfiguration]:

- `getFiles(Spec)`
- `getFirstLevelModuleDependencies(Spec)`

    public void beforeExecute(@DelegatesTo(GradleExecuter.class) Closure action) {
        beforeExecute.add(new ClosureBackedAction<>(action));
    }

    @Override
    public void afterExecute(Action<? super GradleExecuter> action) {
        afterExecute = afterExecute.add(action);
    }

    @Override
    public void afterExecute(@DelegatesTo(GradleExecuter.class) Closure action) {