[GROOVY-8452] @CompileStatic, generic with 'extends' bug: Expected parameter of type ? but got A

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.13, 3.0.0-alpha-3, 2.5.2
• Fix Version/s: 4.0.0-beta-1, 3.0.9
• Component/s: Static compilation
• Assignee: Eric Milles
• Reporter: Xiaoguang Wang
• Created: 18/Jan/18 17:32
• Updated: 03/Feb/22 22:34
• Resolved: 25/Oct/21 14:09

Description

 

The inferred type of a generic List<? extends X> is wrong.

The minimal reproduceable code is:

import groovy.transform.CompileStatic

class A {}
class B extends A {}

@CompileStatic
class TestClassSort {

    void test() {
        //List<? extends A> a  // without ` = null`, this compiles OK
        List<? extends A> a = null
        if(false) {
            a = new ArrayList<A>()
        } else {
            a = new ArrayList<B>()
        }
        //BUG: Error: Groovyc: Expected parameter of type ? but got A
        a.sort({ A v1, A v2 -> return 0 })
    }

    static void main(String []a) {
        new TestClassSort().test()
    }
}