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James Daugherty commented on GROOVY-11508: ------------------------------------------ As for static example, the class file that's generated in 3.x shows: Child Class: {code:java} public class Child extends Parent implements GormEntity<Child> { // Only including the getAll method() for discussion purposes @TraitBridge( traitClass = GormEntity.class, desc = "()Ljava/util/List;" ) public static List<Child> getAll() { CallSite[] var0 = $getCallSiteArray(); return (List)ScriptBytecodeAdapter.castToType(var0[4].call(GormEntity$Trait$Helper.class, Child.class), List.class); } } {code} Parent Class {code:java} public class Parent implements GormEntity<Parent>, GroovyObject { // Only including the getAll method() for discussion purposes @TraitBridge( traitClass = GormEntity.class, desc = "()Ljava/util/List;" ) public static List<Parent> getAll() { CallSite[] var0 = $getCallSiteArray(); return (List)ScriptBytecodeAdapter.castToType(var0[4].call(GormEntity$Trait$Helper.class, Parent.class), List.class); } } {code} I would have expected this behavior since the trait resolution in the docs ([https://docs.groovy-lang.org/latest/html/documentation#_default_conflict_resolution]) says the last declared trait chooses the method that's copied to the implementing class. The data mapping project in Grails took advantage of this so that a child would invoke the child specific code, while a parent would invoke the parent one. > 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 > Assignee: Eric Milles > 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|https://github.com/grails/grails-data-mapping] (GORM) > project. Groovy-5106 does not take into account 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 the impacts of 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? -- This message was sent by Atlassian Jira (v8.20.10#820010)