com.google.javascript.rhino.jstype.NoType Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of closure-compiler Show documentation

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.

There is a newer version: v20240317

Show newest version

/*
 *
 * ***** 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;



/**
 * Bottom type, representing the subclass of any value or object.
 *
 * Although JavaScript programmers can't explicitly denote the bottom type,
 * it comes up in static analysis. For example, if we have:
 * 
 * var x = null;
 * if (x) {
 *   f(x);
 * }
 * 
 * We need to be able to assign {@code x} a type within the {@code f(x)}
 * call. Since it has no possible type, we assign {@code x} the NoType,
 * so that {@code f(x)} is legal no matter what the type of {@code f}'s
 * first argument is.
 *
 * @see Bottom types
 */
public class NoType extends NoObjectType {
  private static final long serialVersionUID = 1L;

  NoType(JSTypeRegistry registry) {
    super(registry);
  }

  @Override
  JSTypeClass getTypeClass() {
    return JSTypeClass.NO;
  }

  @Override
  public final boolean isNoObjectType() {
    return false;
  }

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

  @Override
  public final boolean isNullable() {
    return true;
  }

  @Override
  public final boolean isVoidable() {
    return true;
  }

  @Override
  public final BooleanLiteralSet getPossibleToBooleanOutcomes() {
    return BooleanLiteralSet.BOTH;
  }

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

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

  @Override
  void appendTo(TypeStringBuilder sb) {
    sb.append(sb.isForAnnotations() ? "?" : "None");
  }
}