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https://issues.apache.org/jira/browse/GROOVY-11508?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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James Daugherty updated GROOVY-11508:
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Summary: Multiple traits with related generic types cannot be used (was:
Revert Groovy-5106 or allow it to be a warning only)
> Multiple traits with related generic types cannot be used
> ---------------------------------------------------------
>
> Key: GROOVY-11508
> URL: https://issues.apache.org/jira/browse/GROOVY-11508
> Project: Groovy
> Issue Type: Bug
> Components: Compiler
> Affects Versions: 4.0.0
> Reporter: James Daugherty
> Priority: Major
>
> When updating Grails from Groovy 3.x to 4.x we discovered that Groovy-5106
> prevents us from updating to Groovy 4 for the grails-data-mapping (GORM)
> project. Groovy-5106 does not take into relationships between generic types
> and groovy does not support inheritance in generic types on traits so we have
> no workable solution for using Groovy 4.
>
> For example, the following is not possible in Groovy 4:
> {code:java}
> class Parent extends GormEntity<Parent> {
> }
> class Child extends GormEntity<Child> {
> }
> class GormEntity<? extends GormEntity> { // ? extends GormEntity is not
> allowed
> }{code}
>
> We have documented this issue on the grails-data-mapping project here:
> [https://github.com/grails/grails-data-mapping/issues/1811] We have
> discovered that the original change could be reverted and continue to work
> with the latest Java & Groovy.
>
> For Grails Data Mapping (GORM), there is support for inheritance between a
> Parent & Child domain object. This is often implemented like this:
> {code:java}
> class Parent extends GormEntity<Parent> {
> }
> class Child extends GormEntity<Child> {
> }
> trait GormEntity<D> { // Simplified for this ticket
> static D get(Serializable id)
>
> static List<D> getAll()
> }
> {code}
> This allows someone to do the following in code:
> {code:java}
> Parent.get(1L) // Will find either a Child or Parent
> Child.get(1L) // Will find only child types{code}
>
> Since Groovy-5106 does not take into account inheritance, can this change be
> reverted or changed to a warning until inheritance is taken into account?
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