Eclipse中的空注释处理器

Question

I'm using the Eclipse JDT Null annotation processor and I'm getting some weird behaviour when using java.lang.Class.

package test;

import org.eclipse.jdt.annotation.Nullable;

public class AnnotationSpul {

    @Nullable
    public <V> V get1(Class<V> type) {
        return get2(type); //This line has a warning
    }

    @Nullable
    public <V> V get2(Class<V> type) {
        return null;
    }
}

This is my package info:

@NonNullByDefault({ PARAMETER, RETURN_TYPE, FIELD })
package test;

import static org.eclipse.jdt.annotation.DefaultLocation.FIELD;
import static org.eclipse.jdt.annotation.DefaultLocation.PARAMETER;
import static org.eclipse.jdt.annotation.DefaultLocation.RETURN_TYPE;

import org.eclipse.jdt.annotation.NonNullByDefault;

The warning I get is: "The expression of type '@NonNull Class' needs unchecked conversion to conform to '@NonNull Class<@Nullable V>'"

I don't understand why I get the warning. The method signatures are exactly the same, so why does the value passed need conversion? Why is type inferred as @NonNull Class<V> in one method and @NonNull Class<@Nullable V> in the other?

Answer 1

This was a bug in ecj 4.4 . In a combination of type inference and null inference ecj over-eagerly inferred the type parameter to @Nullable V .

The bug was fixed in 4.5M5 , so the upcoming release 4.5 (Mars) will accept the program as expected.