[GROOVY-7204] Static type checking and compilation fail when multiple generics in use

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.3.8
• Fix Version/s: 3.0.0-alpha-3, 2.5.0-rc-3
• Component/s: Static compilation, Static Type Checker
• Assignee: Daniel Sun
• Reporter: Mauro Molinari
• Created: 10/Dec/14 02:48
• Updated: 11/Nov/22 20:18
• Resolved: 10/May/18 08:02

Description

Consider the following interfaces:

CrudRepository.java

package f;

import java.io.Serializable;

public interface CrudRepository<T, S extends Serializable> {

	void delete(S arg);
	void delete(T arg);
}

MyRepository.java

package f;

public interface MyRepository extends CrudRepository<String, Long> {
}

The following implementation class:

MyRepositoryImpl.java

package f;

public class MyRepositoryImpl implements MyRepository {

	@Override
	public void delete(String arg) {
		System.out.println("String");
	}

	@Override
	public void delete(Long arg) {
		System.out.println("Long");
	}
}

And the following Groovy class:

MyClass.groovy

package f

import groovy.transform.CompileStatic;
import groovy.transform.TypeChecked;

@TypeChecked
class MyClass {

	static MyRepository factory() {
		return new MyRepositoryImpl()
	}
	
	static void main(String[] args) {
		MyRepository r = factory()
		r.delete('foo')
	}	
}

Static type checking returns the following error:

MyClass.groovy: 15: [Static type checking] - Cannot call f.MyRepository#delete(S) with arguments [java.lang.String]

The same applies if you use @CompileStatic instead of @TypeChecked.

Note that if, In the previous code, you change the method main by replacing:

MyRepository r = factory()

with:

MyRepository r = new MyRepositoryImpl()

compilation succeeds. However in real code this might not be possible (the MyRepository instance may be injected and auto-generated, think of Spring Data for instance).

The only workaround is (yet again...) to disable static type checking and static compilation.

Issue Links

• relates to: GROOVY-10820 SC: static choice of Class vs Object extension for Type dot name
• links to: GitHub Pull Request #699