Description Clovis Seragiotto 2014-08-13 09:44:47 EDT

In the program below, the method requireNonNull is invoked with 

@Nullable Iterable<@NonNull String> 

as argument, and therefore the returned value is 

@NonNull Iterable<@NonNull String>. 

Assigning the returned value to the field iterable is therefore safe.

With Annotation-based null analysis enabled and "Unchecked conversion from non-annotated type to @NonNull type" set to warning, the null analysis issues a bogus warning: "The expression of type '@NonNull Iterable<String>' needs unchecked conversion to conform to '@NonNull Iterable<@NonNull String>'" at the line marked with (*)


package foo.bar;

import org.eclipse.jdt.annotation.NonNull;
import org.eclipse.jdt.annotation.NonNullByDefault;
import org.eclipse.jdt.annotation.Nullable;

@NonNullByDefault({})
public abstract class Foo {
    
    abstract <T> @NonNull T requireNonNull(@Nullable T obj);
    
    @NonNull Iterable<@NonNull String> iterable;
    
    Foo(@Nullable Iterable<@NonNull String> iterable) {
        this.iterable = requireNonNull(iterable); // (*)
    }
}