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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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/*
 * Copyright 2020 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.javascript.jscomp.disambiguate;

/**
 * Describes one way in which a property became invalidated.
 *
 * This information is only used diagnostically and doesn't affect the outcome of optimizations.
 * Since diagnostic information isn't usually rendered, this class is designed to defer work as much
 * as possible.
 */
@SuppressWarnings({"UnusedVariable", "FieldCanBeLocal"}) // GSON reflection.
class Invalidation {

  static Invalidation wellKnownProperty() {
    return WELL_KNOWN_PROPERTY;
  }

  static Invalidation invalidatingType(int recieverType) {
    return new WithRecieverType(Reason.INVALIDATING_TYPE, recieverType);
  }

  static Invalidation undeclaredAccess(int recieverType) {
    return new WithRecieverType(Reason.UNDECLARED_ACCESS, recieverType);
  }

  private enum Reason {
    /** Certain well-known properties like "prototype" are always invalidated. */
    WELL_KNOWN_PROPERTY,
    /** Properties accessed on invalidating types (like Object) are invalidated. */
    INVALIDATING_TYPE,
    /** Properties accessed on types that don't declare them are invalidated. */
    UNDECLARED_ACCESS;
  }

  private final Reason reason;

  private Invalidation(Reason reason) {
    this.reason = reason;
  }

  /** Anonymous classes are not serialized correctly by GSON. */
  private static final class WithRecieverType extends Invalidation {
    final int recieverType;

    WithRecieverType(Reason reason, int recieverType) {
      super(reason);
      this.recieverType = recieverType;
    }
  }

  private static final Invalidation WELL_KNOWN_PROPERTY =
      new Invalidation(Reason.WELL_KNOWN_PROPERTY);
}