package org.checkerframework.framework.qual;
import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* A meta-annotation that indicates that an annotation is a polymorphic type qualifier.
*
* <p>Any method written using a polymorphic type qualifier conceptually has two or more versions
* — one version for each qualifier in the qualifier hierarchy. In each version of the method,
* all instances of the polymorphic type qualifier are replaced by one of the other type qualifiers.
*
* <p>
*
* @checker_framework.manual #qualifier-polymorphism Qualifier polymorphism
*/
@Documented
@Target({ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface PolymorphicQualifier {
/**
* Usually, you can write {@code @PolymorphicQualifier} without an argument. When multiple type
* hierarchies are supported by a single type system, then each polymorphic qualifier needs to
* indicate which sub-hierarchy it belongs to. Do so by passing a qualifier from the given
* hierarchy, by convention the top qualifier.
*/
// We use the meaningless PolymorphicQualifier.class as default value and
// then ensure there is a single top qualifier to use.
Class<? extends Annotation> value() default PolymorphicQualifier.class;
}