[GROOVY-7287] Problem With Trait Generics With Conflicting Names

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.0
• Fix Version/s: 2.4.1
• Assignee: Jochen Theodorou
• Reporter: Jeff Brown
• Created: 03/Feb/15 09:33
• Updated: 23/Feb/15 01:12
• Resolved: 06/Feb/15 08:23

Description

The attached traitgenerics.zip contains the following code:

src/main/groovy/demo/SomeTrait.groovy

package demo

trait SomeTrait<T> {
}

src/main/groovy/demo/SomeOtherTrait.groovy

package demo

trait SomeOtherTrait {
    def <T> T someOtherMethod() {
    }
}

src/main/groovy/demo/TopClass.groovy

package demo

class TopClass<T> implements SomeTrait<T>, SomeOtherTrait {}

src/main/groovy/demo/MiddleClass.groovy

package demo

class MiddleClass<T> extends TopClass<T> implements SomeTrait<T>, SomeOtherTrait {}

src/main/groovy/demo/BottomClass.groovy

package demo

class BottomClass extends MiddleClass<String> implements SomeTrait<String>, SomeOtherTrait {}

The code will not compile:

$ ./gradlew clean cG
:clean
:compileJava UP-TO-DATE
:compileGroovy
startup failed:
/Users/jeff/traitgenerics/src/main/groovy/demo/BottomClass.groovy: -1: The return type of java.lang.Object someOtherMethod() in demo.BottomClass is incompatible with java.lang.String in demo.MiddleClass
. At [-1:-1]  @ line -1, column -1.
1 error

:compileGroovy FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileGroovy'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 4.054 secs

If I change the type parameter name in SomeOtherTrait to anyting other than T, it compiles...

src/main/groovy/demo/SomeOtherTrait.groovy

package demo

trait SomeOtherTrait {
    def <SOM> SOM someOtherMethod() {
    }
}