[GROOVY-8330] Wrong 'Inconvertible types' error on casting interface

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.12
• Fix Version/s: 3.0.0-alpha-1, 2.5.0-beta-2, 2.4.13, 2.6.0-alpha-2
• Component/s: Static compilation, Static Type Checker
• Assignee: Daniel Sun
• Reporter: Alexey Afanasiev
• Created: 26/Sep/17 14:24
• Updated: 27/Sep/17 09:10
• Resolved: 27/Sep/17 07:00

Description

import groovy.transform.CompileStatic

interface A1{}
interface A2 extends A1{}
        
class C1 implements A1{}
class C2 extends C1 implements A2 {}
        
@CompileStatic
def m(A2 a2) {
       C1 c1 = (C1) a2 // There is error here now: Inconvertible types: cannot cast A2 to C1
}

JLS handle this situation in 5.1.6.1 :
A narrowing reference conversion exists from reference type S to reference type T
if ...... - S is an interface type, T is a class type, and T does not name a final class.

Issue Links

• links to: GitHub Pull Request #607