[jira] [Created] (GROOVY-8034) Compile error when using generic type with lower bound

["Yuriy Kiselev (JIRA)" <ji...@apache.org>]

Yuriy Kiselev created GROOVY-8034:
-------------------------------------

             Summary: Compile error when using generic type with lower bound
                 Key: GROOVY-8034
                 URL: https://issues.apache.org/jira/browse/GROOVY-8034
             Project: Groovy
          Issue Type: Bug
    Affects Versions: 2.4.6
         Environment: org.codehaus.groovy:groovy-all:2.4.6 in maven project
            Reporter: Yuriy Kiselev


I'm trying to implement chained generics. It works as Java code but failed to compile by groovyc:
{code}
Error:(38, 9) Groovyc: [Static type checking] - Cannot call <C extends com.github.ykiselev.ChainTest.A<? super O, ?>> com.github.ykiselev.ChainTest$A <? super O -> java.lang.Object, ?>#andThen(C) with arguments [com.github.ykiselev.ChainTest$A <Double, String>]
{code}
Code (JUnit4 unit test)
{code:groovy}
package com.github.ykiselev

import groovy.transform.TypeChecked
import org.junit.Test

@TypeChecked
class ChainTest {

    static class A<I, O> {

        def <C extends A<? super O, ?>> C andThen(C next) {
            return next
        }

    }

    static <I, O, C extends A<? super O, ?>> C chain(A<I, O> self, C next) {
        self.andThen(next)
        return next
    }

    @Test
    "should chain"() {
        def a1 = new A<String, Integer>()
        def a2 = new A<Integer, Double>()
        def a3 = new A<Double, String>()
        def a4 = new A<String, Double>()
        def a5 = new A<Number, Object>()

        a1.andThen(a2) // ok
        a2.andThen(a3) // ok
        a3.andThen(a4) // ok
        a4.andThen(a5) // ok (even without "? super O")

        chain(a1, a2).andThen(a3) // ok
        chain(chain(chain(chain(a1, a2), a3), a4), a5) // ok

        a1.andThen(a2)
                .andThen(a3) // static type checker error
                .andThen(a4)
                .andThen(a5)
    }
}
{code}

This would compile if I change bounded type parameter like this:
{code:groovy}
def <C extends A<O, ?>> C andThen(C next) {
            return next
}
{code}

but I need it bounded.



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