[GROOVY-6691] Cannot extend trait with generic parameter

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.3.0-beta-1
• Fix Version/s: 2.3.0-beta-2
• Assignee: Cédric Champeau
• Reporter: Mark Perry
• Created: 09/Apr/14 21:06
• Updated: 10/Apr/14 17:16
• Resolved: 10/Apr/14 02:46

Description

I get a compiler error when I try to extend a trait with a generic type parameter.

trait Functor<T> { }
trait Applicative<App> extends Functor<App> { }

does not compile with the error message:

src\main\groovy\com\github\mperry\Applicative.groovy: 14: A transform used a generics containing ClassNode com.github.mperry.Functor <T> for the super class com.github.mperry.Applicative directly. You are not supposed to do this. Please create a new ClassNode referring to the old ClassNode and use the new ClassNode instead of the old one. Otherwise the compiler will create wrong descriptors and a potential NullPointerException in TypeResolver in the OpenJDK. If this is not your own doing, please report this bug to the writer
 of the transform. @ line 14, column 1.
   trait Applicative extends Functor {
:compileGroovy FAILED
   ^

Changing the Applicative trait to a simpler form gets the same compiler error:

trait Functor<T> { }
trait Applicative extends Functor { }

Extending from a non-generic trait compiles:

trait Functor { }
trait Applicative<App> extends Functor { }

I am using Gradle 1.11, Java 7 and Windows 7.