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   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
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  package java.lang.invoke;
  
  import java.lang.reflect.*;
  import java.util.*;
  import java.lang.invoke.MethodHandleNatives.Constants;
  import java.lang.invoke.MethodHandles.Lookup;
  import static java.lang.invoke.MethodHandleStatics.*;
  
  /**
   * A symbolic reference obtained by cracking a direct method handle
   * into its consitutent symbolic parts.
   * To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}.
   * <h1><a name="directmh"></a>Direct Method Handles</h1>
   * A <em>direct method handle</em> represents a method, constructor, or field without
   * any intervening argument bindings or other transformations.
   * The method, constructor, or field referred to by a direct method handle is called
   * its <em>underlying member</em>.
   * Direct method handles may be obtained in any of these ways:
   * <ul>
   * <li>By executing an {@code ldc} instruction on a {@code CONSTANT_MethodHandle} constant.
   *     (See the Java Virtual Machine Specification, sections 4.4.8 and 5.4.3.)
   * <li>By calling one of the <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>,
   *     such as {@link Lookup#findVirtual Lookup.findVirtual},
   *     to resolve a symbolic reference into a method handle.
   *     A symbolic reference consists of a class, name string, and type.
   * <li>By calling the factory method {@link Lookup#unreflect Lookup.unreflect}
   *     or {@link Lookup#unreflectSpecial Lookup.unreflectSpecial}
   *     to convert a {@link Method} into a method handle.
   * <li>By calling the factory method {@link Lookup#unreflectConstructor Lookup.unreflectConstructor}
   *     to convert a {@link Constructor} into a method handle.
   * <li>By calling the factory method {@link Lookup#unreflectGetter Lookup.unreflectGetter}
   *     or {@link Lookup#unreflectSetter Lookup.unreflectSetter}
   *     to convert a {@link Field} into a method handle.
   * </ul>
   *
   * <h1>Restrictions on Cracking</h1>
   * Given a suitable {@code Lookup} object, it is possible to crack any direct method handle
   * to recover a symbolic reference for the underlying method, constructor, or field.
   * Cracking must be done via a {@code Lookup} object equivalent to that which created
   * the target method handle, or which has enough access permissions to recreate
   * an equivalent method handle.
   * <p>
   * If the underlying method is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>,
   * the direct method handle will have been "bound" to a particular caller class, the
   * {@linkplain Lookup#lookupClass() lookup class}
   * of the lookup object used to create it.
   * Cracking this method handle with a different lookup class will fail
   * even if the underlying method is public (like {@code Class.forName}).
   * <p>
   * The requirement of lookup object matching provides a "fast fail" behavior
   * for programs which may otherwise trust erroneous revelation of a method
   * handle with symbolic information (or caller binding) from an unexpected scope.
   * Use {@link MethodHandles#reflectAs} to override this limitation.
   *
   * <h1><a name="refkinds"></a>Reference kinds</h1>
   * The <a href="MethodHandles.Lookup.html#lookups">Lookup Factory Methods</a>
   * correspond to all major use cases for methods, constructors, and fields.
   * These use cases may be distinguished using small integers as follows:
   * <table border=1 cellpadding=5 summary="reference kinds">
   * <tr><th>reference kind</th><th>descriptive name</th><th>scope</th><th>member</th><th>behavior</th></tr>
   * <tr>
   *     <td>{@code 1}</td><td>{@code REF_getField}</td><td>{@code class}</td>
   *     <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
   * </tr>
   * <tr>
   *     <td>{@code 2}</td><td>{@code REF_getStatic}</td><td>{@code class} or {@code interface}</td>
   *     <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
   * </tr>
   * <tr>
   *     <td>{@code 3}</td><td>{@code REF_putField}</td><td>{@code class}</td>
   *     <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
   * </tr>
   * <tr>
   *     <td>{@code 4}</td><td>{@code REF_putStatic}</td><td>{@code class}</td>
   *     <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
   * </tr>
   * <tr>
   *     <td>{@code 5}</td><td>{@code REF_invokeVirtual}</td><td>{@code class}</td>
   *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
   * </tr>
   * <tr>
   *     <td>{@code 6}</td><td>{@code REF_invokeStatic}</td><td>{@code class} or {@code interface}</td>
   *     <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
   * </tr>
   * <tr>
   *     <td>{@code 7}</td><td>{@code REF_invokeSpecial}</td><td>{@code class} or {@code interface}</td>
   *     <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
   * </tr>
   * <tr>
   *     <td>{@code 8}</td><td>{@code REF_newInvokeSpecial}</td><td>{@code class}</td>
   *     <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
   * </tr>
   * <tr>
   *     <td>{@code 9}</td><td>{@code REF_invokeInterface}</td><td>{@code interface}</td>
   *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
   * </tr>
   * </table>
   * @since 1.8
   */
  public
  interface MethodHandleInfo {
      /**
       * A direct method handle reference kind,
       * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
       */
      public static final int
          REF_getField                = Constants.REF_getField,
          REF_getStatic               = Constants.REF_getStatic,
          REF_putField                = Constants.REF_putField,
          REF_putStatic               = Constants.REF_putStatic,
          REF_invokeVirtual           = Constants.REF_invokeVirtual,
          REF_invokeStatic            = Constants.REF_invokeStatic,
          REF_invokeSpecial           = Constants.REF_invokeSpecial,
          REF_newInvokeSpecial        = Constants.REF_newInvokeSpecial,
          REF_invokeInterface         = Constants.REF_invokeInterface;
  
      /**
       * Returns the reference kind of the cracked method handle, which in turn
       * determines whether the method handle's underlying member was a constructor, method, or field.
       * See the <a href="MethodHandleInfo.html#refkinds">table above</a> for definitions.
       * @return the integer code for the kind of reference used to access the underlying member
       */
      public int getReferenceKind();
  
      /**
       * Returns the class in which the cracked method handle's underlying member was defined.
       * @return the declaring class of the underlying member
       */
      public Class<?> getDeclaringClass();
  
      /**
       * Returns the name of the cracked method handle's underlying member.
       * This is {@code "<init>"} if the underlying member was a constructor,
       * else it is a simple method name or field name.
       * @return the simple name of the underlying member
       */
      public String getName();
  
      /**
       * Returns the nominal type of the cracked symbolic reference, expressed as a method type.
       * If the reference is to a constructor, the return type will be {@code void}.
       * If it is to a non-static method, the method type will not mention the {@code this} parameter.
       * If it is to a field and the requested access is to read the field,
       * the method type will have no parameters and return the field type.
       * If it is to a field and the requested access is to write the field,
       * the method type will have one parameter of the field type and return {@code void}.
       * <p>
       * Note that original direct method handle may include a leading {@code this} parameter,
       * or (in the case of a constructor) will replace the {@code void} return type
       * with the constructed class.
       * The nominal type does not include any {@code this} parameter,
       * and (in the case of a constructor) will return {@code void}.
       * @return the type of the underlying member, expressed as a method type
       */
      public MethodType getMethodType();
  
      // Utility methods.
      // NOTE: class/name/type and reference kind constitute a symbolic reference
      // member and modifiers are an add-on, derived from Core Reflection (or the equivalent)
  
      /**
       * Reflects the underlying member as a method, constructor, or field object.
       * If the underlying member is public, it is reflected as if by
       * {@code getMethod}, {@code getConstructor}, or {@code getField}.
       * Otherwise, it is reflected as if by
       * {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}.
       * The underlying member must be accessible to the given lookup object.
       * @param <T> the desired type of the result, either {@link Member} or a subtype
       * @param expected a class object representing the desired result type {@code T}
       * @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges
       * @return a reference to the method, constructor, or field object
       * @exception ClassCastException if the member is not of the expected type
       * @exception NullPointerException if either argument is {@code null}
       * @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object
       */
      public <T extends Member> T reflectAs(Class<T> expected, Lookup lookup);
  
      /**
       * Returns the access modifiers of the underlying member.
       * @return the Java language modifiers for underlying member,
       *         or -1 if the member cannot be accessed
       * @see Modifier
       * @see #reflectAs
       */
      public int getModifiers();
  
      /**
       * Determines if the underlying member was a variable arity method or constructor.
       * Such members are represented by method handles that are varargs collectors.
       * @implSpec
       * This produces a result equivalent to:
       * <pre>{@code
       *     getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
       * }</pre>
       *
       *
       * @return {@code true} if and only if the underlying member was declared with variable arity.
       */
      // spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector
      public default boolean isVarArgs()  {
          // fields are never varargs:
          if (MethodHandleNatives.refKindIsField((byte) getReferenceKind()))
              return false;
          // not in the public API: Modifier.VARARGS
          final int ACC_VARARGS = 0x00000080;  // from JVMS 4.6 (Table 4.20)
          assert(ACC_VARARGS == Modifier.TRANSIENT);
          return Modifier.isTransient(getModifiers());
      }
  
      /**
       * Returns the descriptive name of the given reference kind,
       * as defined in the <a href="MethodHandleInfo.html#refkinds">table above</a>.
       * The conventional prefix "REF_" is omitted.
       * @param referenceKind an integer code for a kind of reference used to access a class member
       * @return a mixed-case string such as {@code "getField"}
       * @exception IllegalArgumentException if the argument is not a valid
       *            <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
       */
      public static String referenceKindToString(int referenceKind) {
          if (!MethodHandleNatives.refKindIsValid(referenceKind))
              throw newIllegalArgumentException("invalid reference kind", referenceKind);
          return MethodHandleNatives.refKindName((byte)referenceKind);
      }
  
      /**
       * Returns a string representation for a {@code MethodHandleInfo},
       * given the four parts of its symbolic reference.
       * This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the
       * {@linkplain #referenceKindToString reference kind string} for {@code kind},
       * {@code C} is the {@linkplain Class#getName name} of {@code defc}
       * {@code N} is the {@code name}, and
       * {@code MT} is the {@code type}.
       * These four values may be obtained from the
       * {@linkplain #getReferenceKind reference kind},
       * {@linkplain #getDeclaringClass declaring class},
       * {@linkplain #getName member name},
       * and {@linkplain #getMethodType method type}
       * of a {@code MethodHandleInfo} object.
       *
       * @implSpec
       * This produces a result equivalent to:
       * <pre>{@code
       *     String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
       * }</pre>
       *
       * @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference
       * @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference
       * @param name the {@linkplain #getName member name} part of the symbolic reference
       * @param type the {@linkplain #getMethodType method type} part of the symbolic reference
       * @return a string of the form {@code "RK C.N:MT"}
       * @exception IllegalArgumentException if the first argument is not a valid
       *            <a href="MethodHandleInfo.html#refkinds">reference kind number</a>
       * @exception NullPointerException if any reference argument is {@code null}
       */
      public static String toString(int kind, Class<?> defc, String name, MethodType type) {
          Objects.requireNonNull(name); Objects.requireNonNull(type);
          return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type);
      }
  
      // BEGIN Android-added: refKind...() methods needed for API compatibility with 26.
      // These methods were accidentally added into the public API in API level. They are now
      // deprecated as a prelude to being removed from the public API.
      /**
       * @deprecated This internal method was accidentally added to API 26 and must not be used. No
       *             replacement is available but it is possible to replicate using information from
       *             the <a href="MethodHandleInfo.html#refkinds">table above</a>, e.g.
       *             {@code refKind >= 1 && refKind <= 9}. There are no guarantees that this logic
       *             will work if future versions extend the table.
       */
      @Deprecated
      static boolean refKindIsValid(int refKind) {
          return MethodHandleNatives.refKindIsValid(refKind);
      }
  
      /**
       * @deprecated This internal method was accidentally added to API 26 and must not be used. No
       *             replacement is available but it is possible to replicate using information from
       *             the <a href="MethodHandleInfo.html#refkinds">table above</a>, e.g.
       *             {@code refKind >= 1 && refKind <= 4}.  There are no guarantees that this logic
       *             will work if future versions extend the table.
       */
      @Deprecated
      static boolean refKindIsField(int refKind) {
          return MethodHandleNatives.refKindIsField((byte) refKind);
      }
  
      /**
       * @deprecated This internal method was accidentally added to API 26 and must not be used. Use
       *             {@link MethodHandleInfo#referenceKindToString(int)} instead.
       */
      @Deprecated
      static String refKindName(int refKind) {
          return MethodHandleNatives.refKindName((byte) refKind);
      }
      // END Android-added: refKind...() methods needed for API compatibility with 26.
  }
  