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  1. Groovy
  2. GROOVY-8881

Inner class - qualified "this" reference cast exception inside 2 closures

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      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".

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            • Assignee:
              paulk Paul King
              Reporter:
              anton.pryamostanov Anton Pryamostanov
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              • Created:
                Updated:
                Resolved: