package org.checkerframework.common.value.qual;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.checkerframework.framework.qual.SubtypeOf;

/**
 * An expression with this type is exactly the same as an {@link IntRange} annotation whose {@code
 * from} field is {@code 0} and whose {@code to} field is {@code Integer.MAX_VALUE}. However, this
 * annotation is derived from an {@code org.checkerframework.checker.index.qual.NonNegative}
 * annotation.
 *
 * <p>IntRangeFromNonNegative annotations derived from NonNegative annotations are used to create
 * IntRange annotations, but IntRangeFromNonNegative annotations are not checked when they appear on
 * the left hand side of expressions. Therefore, the Index Checker MUST be run on any code
 * with @NonNegative annotations on the left-hand side of expressions, since the Value Checker will
 * derive information from them but not check them.
 *
 * <p>It is an error to write this annotation directly. {@code @NonNegative} or {@code IntRange(from
 * = 0, to = Integer.MAX_VALUE)} should always be written instead. This annotation is not retained
 * in bytecode, but is replaced with {@code @UnknownVal}, so that it is not enforced on method
 * boundaries. The {@code @NonNegative} annotation it replaced is retained in bytecode by the Lower
 * Bound Checker instead.
 *
 * @checker_framework.manual #constant-value-checker Constant Value Checker
 */
@Documented
@Retention(RetentionPolicy.SOURCE)
@Target({})
@SubtypeOf(UnknownVal.class)
public @interface IntRangeFromNonNegative {}