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Posted to notifications@groovy.apache.org by "Yuriy Kiselev (JIRA)" <ji...@apache.org> on 2017/01/05 10:45:58 UTC
[jira] [Commented] (GROOVY-8034) Compile error when using generic
type with lower bound
[ https://issues.apache.org/jira/browse/GROOVY-8034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15801035#comment-15801035 ]
Yuriy Kiselev commented on GROOVY-8034:
---------------------------------------
(i) This code is compiled without errors by groovy 2.4.4
> 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 fails 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}
> 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
> void "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}
> def <C extends A<O, ?>> C andThen(C next) {
> return next
> }
> {code}
> but I need it bounded.
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