[GROOVY-7687] Bug with @CompileStatic and nested closures

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.5
• Fix Version/s: 2.5.6, 3.0.0-beta-1
• Component/s: Compiler
• Assignee: Paul King
• Reporter: Marc Ewert
• Created: 25/Nov/15 14:28
• Updated: 03/Apr/19 05:50
• Resolved: 22/Jan/19 04:45

Description

I've encountered a strange bug in conjunction with closures, delegates and @CompileStatic. The following code works as expected:

import groovy.transform.CompileStatic

@CompileStatic
class SimpleTest {

    static class Foo {
        List<Bar> bars = Arrays.asList(new Bar())
    }

    static class Bar {
        String message
        public String toString() {return message}
    }


    void execute(Foo foo) {
        interactions(foo, {
            bars.each ( { bar -> bar.message = "hello world"})
        })
    }

    void interactions(Foo foo, @DelegatesTo(Foo) Closure closure) {
        closure.delegate = foo
        closure.resolveStrategy = Closure.DELEGATE_FIRST
        closure()
    }

    static void main(String... args) {
        SimpleTest test = new SimpleTest()
        Foo foo = new Foo()
        test.execute(foo)
        println foo.bars
    }
}

But when the bars member is prefixed with a public modifier the following compilation error is thrown

Exception in thread "main" java.lang.ClassCastException: SimpleTest$_execute_closure1 cannot be cast to SimpleTest$Foo
	at SimpleTest$_execute_closure1.doCall(SimpleTest.groovy:18)
	at SimpleTest$_execute_closure1.call(SimpleTest.groovy)
	at SimpleTest.interactions(SimpleTest.groovy:25)
	at SimpleTest.execute(SimpleTest.groovy:17)
	at SimpleTest.main(SimpleTest.groovy:31)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Here the code causing the error:

import groovy.transform.CompileStatic

@CompileStatic
class SimpleTest {

    static class Foo {
        public List<Bar> bars = Arrays.asList(new Bar())
    }

    static class Bar {
        String message
        public String toString() {return message}
    }


    void execute(Foo foo) {
        interactions(foo, {
            bars.each ( { bar -> bar.message = "hello world"})
        })
    }

    void interactions(Foo foo, @DelegatesTo(Foo) Closure closure) {
        closure.delegate = foo
        closure.resolveStrategy = Closure.DELEGATE_FIRST
        closure()
    }

    static void main(String... args) {
        SimpleTest test = new SimpleTest()
        Foo foo = new Foo()
        test.execute(foo)
        println foo.bars
    }
}

Issue Links

• is related to: GROOVY-9063 Groovy 2.5.6 @CompileStatic generates invalid bytecode (leading to runtime ClassCastException) when accessing protected instance member from 2 level of nested closures