Java 8 compiler bug?

[Oliver Gierke]

Sorry, I forgot the link to the reproducing example:

https://dl.dropboxusercontent.com/u/25310722/compiler-ambiguity.zip

> Anfang der weitergeleiteten Nachricht:
> 
> Von: Oliver Gierke <ogierke at pivotal.io>
> Betreff: Java 8 compiler bug?
> Datum: 16. November 2016 um 00:46:02 MEZ
> An: compiler-dev at openjdk.java.net
> 
> Hi all,
> 
> I just ran in this code compiling fine with a JDK 8 if I define a compilation source and target of 1.6, but not if I define both values of 1.8.
> 
> public class Ambiguity {
> 
> 	public void foo(CriteriaBuilder builder) {
> 
> 		Expression<Object> objectExpression = null;
> 		Expression<Collection<Object>> collectionOfObjectExpression = null;
> 		builder.isNotMember(objectExpression, collectionOfObjectExpression);
> 		//      ^^^^^^^^^^^ - ambiguous
> 	}
> }
> 
> CriteriaBuilder and all other types come from JPA. The method in question has two overloads:
> 
> <E, C extends Collection<E>> Predicate isNotMember(Expression<E> elem, Expression<C> collection);
> <E, C extends Collection<E>> Predicate isNotMember(E elem, Expression<C> collection);
> 
> I fail to understand why the second method is even considered as that create a contradiction between the bound values of E (Expression<…>) and C (Collection<Object>).
> 
> I've prepared an example here [0]. Steps to reproduce:
> 
> 1. Unzip
> 2. Run mvn clean compile -> fails
> 3. Change java.version property in pom.xml to 1.6
> 4. Run mvn clean compile -> succeeds
> 
> $ java -version
> java version "1.8.0_112"
> Java(TM) SE Runtime Environment (build 1.8.0_112-b16)
> Java HotSpot(TM) 64-Bit Server VM (build 25.112-b16, mixed mode)
> 
> Is that a known issue, something I oversee or should I create a ticket for that?
> 
> Cheers,
> Ollie
> 

--
/**
 * @author Oliver Gierke - Senior Software Engineer
 *
 * @param email ogierke at pivotal.io
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