[GROOVY-5639] Spurious "Closure shared variable has been assigned with various type" exception

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.0, 2.0.1
• Fix Version/s: 2.0.2
• Component/s: Static Type Checker
• Environment: 64-bit Linux JDK 1.7.0.5
• Assignee: Cédric Champeau
• Reporter: Marlon Pierce
• Created: 27/Jul/12 17:16
• Updated: 11/Sep/12 01:15
• Resolved: 21/Aug/12 11:07

Description

Compiling this fails:

import groovy.transform.TypeChecked

@TypeChecked
class Foo {

    private void doIt() {
        Closure<Void> c = {
            List<String> list = new ArrayList<String>()
            String s = "foo"
            10.times {
                list.add(s)
            }
        }
    }
}

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Foo.groovy: 11: [Static type checking] - A closure shared variable [list] has been assigned with various types and the method [add(java.lang.Object <E>)] does not exist in the lowest upper bound of those types: [java.util.ArrayList <java.lang.String>]. In general, this is a bad practice (variable reuse) because the compiler cannot determine safely what is the type of the variable at the moment of the call in a multithreaded context.
 @ line 11, column 17.
                   list.add(s)
                   ^

1 error

The error only occurs when a closure is involved. The following works fine:

import groovy.transform.TypeChecked

@TypeChecked
class Bar {
    void doIt() {
        List<String> list = new ArrayList<String>()
        String s = "foo"
        10.times {
            list.add(s)
        }
    }
}