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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Bob Jervis
 *   Google Inc.
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package com.google.javascript.rhino.jstype;

import static com.google.javascript.rhino.jstype.TernaryValue.FALSE;
import static com.google.javascript.rhino.jstype.TernaryValue.TRUE;

import com.google.javascript.rhino.ErrorReporter;
import com.google.javascript.rhino.Node;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * An enum type representing a branded collection of elements. Each element
 * is referenced by its name, and has an {@link EnumElementType} type.
 */
public class EnumType extends PrototypeObjectType {
  private static final long serialVersionUID = 1L;

  // the type of the individual elements
  private EnumElementType elementsType;
  // the elements' names (they all have the same type)
  private final Set elements = new HashSet<>();

  /**
   * Creates an enum type.
   *
   * @param name the enum's name
   * @param elementsType the base type of the individual elements
   */
  EnumType(JSTypeRegistry registry, String name, Node source,
      JSType elementsType) {
    super(registry, "enum{" + name + "}", null);
    this.elementsType = new EnumElementType(registry, elementsType, name, this);
  }

  @Override
  public EnumType toMaybeEnumType() {
    return this;
  }

  @Override
  public ObjectType getImplicitPrototype() {
    return registry.getNativeObjectType(JSTypeNative.OBJECT_TYPE);
  }

  /**
   * Gets the elements defined on this enum.
   * @return the elements' names defined on this enum. The returned set is
   *         immutable.
   */
  public Set getElements() {
    return Collections.unmodifiableSet(elements);
  }

  /**
   * Defines a new element on this enum.
   * @param name the name of the new element
   * @param definingNode the {@code Node} that defines this new element
   * @return true iff the new element is added successfully
   */
  public boolean defineElement(String name, Node definingNode) {
    elements.add(name);
    return defineDeclaredProperty(name, elementsType, definingNode);
  }

  /**
   * Gets the elements' type.
   */
  public EnumElementType getElementsType() {
    return elementsType;
  }

  @Override
  public TernaryValue testForEquality(JSType that) {
    TernaryValue result = super.testForEquality(that);
    if (result != null) {
      return result;
    }
    return this.isEquivalentTo(that) ? TRUE : FALSE;
  }

  @Override
  public boolean isSubtype(JSType that) {
    return isSubtype(that, ImplCache.create(), SubtypingMode.NORMAL);
  }

  @Override
  protected boolean isSubtype(JSType that,
      ImplCache implicitImplCache, SubtypingMode subtypingMode) {
    return that.isEquivalentTo(getNativeType(JSTypeNative.OBJECT_TYPE)) ||
        that.isEquivalentTo(getNativeType(JSTypeNative.OBJECT_PROTOTYPE)) ||
        JSType.isSubtypeHelper(this, that, implicitImplCache, subtypingMode);
  }

  @Override
  StringBuilder appendTo(StringBuilder sb, boolean forAnnotations) {
    return sb.append(forAnnotations ? "Object" : getReferenceName());
  }

  @Override
  public String getDisplayName() {
    return elementsType.getDisplayName();
  }

  @Override
  public  T visit(Visitor visitor) {
    return visitor.caseObjectType(this);
  }

  @Override  T visit(RelationshipVisitor visitor, JSType that) {
    return visitor.caseObjectType(this, that);
  }

  @Override
  public FunctionType getConstructor() {
    return null;
  }

  @Override
  public boolean matchesNumberContext() {
    return false;
  }

  @Override
  public boolean matchesStringContext() {
    return true;
  }

  @Override
  public boolean matchesObjectContext() {
    return true;
  }

  @Override
  JSType resolveInternal(ErrorReporter t, StaticTypedScope scope) {
    elementsType = (EnumElementType) elementsType.resolve(t, scope);
    return super.resolveInternal(t, scope);
  }
}