package org.checkerframework.framework.qual;

import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PACKAGE;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE;

import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Applied to a declaration of a package, type, method, variable, etc., specifies that the given
 * annotation should be the default. The default is applied to type uses within the declaration for
 * which no other annotation is explicitly written. (The default is not applied to the "parametric
 * locations": class declarations, type parameter declarations, and type parameter uses.) If
 * multiple {@code DefaultQualifier} annotations are in scope, the innermost one takes precedence.
 * DefaultQualifier takes precedence over {@link DefaultQualifierInHierarchy}.
 *
 * <p>If you wish to write multiple {@code @DefaultQualifier} annotations (for unrelated type
 * systems, or with different {@code locations} fields) at the same location, use {@link
 * DefaultQualifiers}.
 *
 * @see org.checkerframework.framework.qual.TypeUseLocation
 * @see DefaultQualifiers
 * @see DefaultQualifierInHierarchy
 * @see DefaultFor
 */
@Documented
@Retention(RetentionPolicy.SOURCE)
@Target({PACKAGE, TYPE, CONSTRUCTOR, METHOD, FIELD, LOCAL_VARIABLE, PARAMETER})
public @interface DefaultQualifier {

    /**
     * The Class for the default annotation.
     *
     * <p>To prevent affecting other type systems, always specify an annotation in your own type
     * hierarchy. (For example, do not set "org.checkerframework.framework.qual.Unqualified" as the
     * default.)
     */
    Class<? extends Annotation> value();

    /** @return the locations to which the annotation should be applied */
    TypeUseLocation[] locations() default {TypeUseLocation.ALL};
}