[GROOVY-8881] Inner class - qualified "this" reference cast exception inside 2 closures

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-4, 2.5.5
• Component/s: Compiler, groovy-runtime
• Assignee: Paul King
• Reporter: Anton Pryamostanov
• Created: 13/Nov/18 09:01
• Updated: 16/Jan/19 12:07
• Resolved: 16/Nov/18 10:51

Description

Let's consider the below example of qualified (Outer class) "this" reference from within the Inner class, used inside a closure defined inside another closure (2 layers of closures):

class OuterClass implements Runnable {

    class InnerClass {

        String bar() {
            Closure closureOne = {
                Closure closureTwo = {
                    OuterClass outerClassViaQualifiedThisReference = OuterClass.this
                    return outerClassViaQualifiedThisReference
                }
                return closureTwo.call()
            }
            closureOne.call()
        }

    }

    String toString() {
        return "OuterClass"
    }

    void run() {
        System.out.println(new InnerClass().bar())
    }
}

It produces the below runtime exception:

java.lang.ClassCastException: OuterClass$InnerClass cannot be cast to OuterClass$InnerClass$_bar_closure1
	at OuterClass$InnerClass$_bar_closure1$_closure2.doCall(ConsoleScript279:8)
	at OuterClass$InnerClass$_bar_closure1$_closure2.doCall(ConsoleScript279)
	at OuterClass$InnerClass$_bar_closure1.doCall(ConsoleScript279:11)
	at OuterClass$InnerClass$_bar_closure1.doCall(ConsoleScript279)
	at OuterClass$InnerClass.bar(ConsoleScript279:13)
	at OuterClass$InnerClass$bar.call(Unknown Source)
	at OuterClass.run(ConsoleScript279:23)

However the below code runs fine (if only 1 closure is used):

class OuterClass implements Runnable {

    class InnerClass {

        String bar() {
            Closure closureOne = {
                //Closure closureTwo = {
                    OuterClass outerClassViaQualifiedThisReference = OuterClass.this
                    return outerClassViaQualifiedThisReference
                //}
                //return closureTwo.call()
            }
            closureOne.call()
        }

    }

    String toString() {
        return "OuterClass"
    }

    void run() {
        System.out.println(new InnerClass().bar())
    }
}

Expected result:

Code should run in both cases without runtime exceptions and should output "OuterClass".