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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.

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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 com.google.javascript.rhino.QualifiedName;
import com.google.javascript.rhino.StaticScope;
import org.jspecify.nullness.Nullable;

/**
 * The {@code StaticTypedScope} interface must be implemented by any object that defines variables
 * for the purposes of static analysis. It is distinguished from the {@code Scriptable} class that
 * Rhino normally uses to represent a run-time scope.
 *
 */
public interface StaticTypedScope extends StaticScope {
  /** Returns the scope enclosing this one or null if none. */
  @Override
  StaticTypedScope getParentScope();

  /**
   * Returns any defined slot within this scope for this name. This call continues searching through
   * parent scopes if a slot with this name is not found in the current scope.
   *
   * @param name The name of the variable slot to look up.
   * @return The defined slot for the variable, or {@code null} if no definition exists.
   */
  @Override
  StaticTypedSlot getSlot(String name);

  /** Like {@code getSlot} but does not recurse into parent scopes. */
  @Override
  StaticTypedSlot getOwnSlot(String name);

  /** Returns the expected type of {@code this} in the current scope. */
  JSType getTypeOfThis();

  /**
   * Looks up a given qualified name in the scope. if that fails, looks up the component properties
   * off of any owner types that are in scope.
   *
   * This is always more or equally expensive as calling getSlot(String name), so should only be
   * used when necessary.
   *
   * This only returns declared qualified names and known properties. It returns null given an
   * inferred name.
   */
  default @Nullable JSType lookupQualifiedName(QualifiedName qname) {
    StaticTypedSlot slot = getSlot(qname.join());
    if (slot != null && !slot.isTypeInferred()) {
      return slot.getType();
    } else if (!qname.isSimple()) {
      JSType type = lookupQualifiedName(qname.getOwner());
      if (type != null && !type.isUnknownType()) {
        return type.findPropertyType(qname.getComponent());
      }
    }
    return null;
  }
}