checker-qual/src/main/java/org/checkerframework/checker/nullness/qual/EnsuresKeyForIf.java

package org.checkerframework.checker.nullness.qual;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.checkerframework.framework.qual.ConditionalPostconditionAnnotation;
import org.checkerframework.framework.qual.InheritedAnnotation;
import org.checkerframework.framework.qual.JavaExpression;
import org.checkerframework.framework.qual.QualifierArgument;

/**
 * Indicates that the given expressions evaluate to a value that is a key in all the given maps, if
 * the method returns the given result (either true or false).
 *
 * <p>As an example, consider the following method in {@code java.util.Map}:
 *
 * <pre>
 *   &#64;EnsuresKeyForIf(result=true, expression="key", map="this")
 *   public boolean containsKey(String key) { ... }
 * </pre>
 *
 * If an invocation {@code m.containsKey(k)} returns true, then the type of {@code k} can be
 * inferred to be {@code @KeyFor("m")}.
 *
 * @see KeyFor
 * @see EnsuresKeyFor
 * @checker_framework.manual #map-key-checker Map Key Checker
 */
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
@ConditionalPostconditionAnnotation(qualifier = KeyFor.class)
@InheritedAnnotation
@Repeatable(EnsuresKeyForIf.List.class)
public @interface EnsuresKeyForIf {
  /** The value the method must return, in order for the postcondition to hold. */
  boolean result();

  /**
   * Java expressions that are keys in the given maps after the method returns the given result.
   *
   * @checker_framework.manual #java-expressions-as-arguments Syntax of Java expressions
   */
  String[] expression();

  /**
   * Returns Java expressions whose values are maps, each of which contains each expression value as
   * a key (after the method returns the given result).
   *
   * @return Java expressions whose values are maps, each of which contains each expression value as
   *     a key (after the method returns the given result)
   * @checker_framework.manual #java-expressions-as-arguments Syntax of Java expressions
   */
  @JavaExpression
  @QualifierArgument("value")
  String[] map();

  /**
   * A wrapper annotation that makes the {@link EnsuresKeyForIf} annotation repeatable.
   *
   * <p>Programmers generally do not need to write this. It is created by Java when a programmer
   * writes more than one {@link EnsuresKeyForIf} annotation at the same location.
   */
  @Documented
  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.METHOD, ElementType.CONSTRUCTOR})
  @ConditionalPostconditionAnnotation(qualifier = KeyFor.class)
  @InheritedAnnotation
  @interface List {
    /**
     * Returns the repeatable annotations.
     *
     * @return the repeatable annotations
     */
    EnsuresKeyForIf[] value();
  }
}