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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.base;

import static com.google.javascript.jscomp.base.JSCompObjects.identical;

/**
 * A reference to another object that uses the identity semantics of that object for equality.
 *
 * The intended purpose of these references is to make give identity semantics to {@code Map}
 * keys. For example, {@code LinkedHashMap, Bar>}, behaves as an {@code
 * IdentityHashMap} but with deterministic iteration order.
 */
public final class IdentityRef {

  private final T value;

  public static  IdentityRef of(U value) {
    return new IdentityRef<>(value);
  }

  private IdentityRef(T value) {
    this.value = value;
  }

  public T get() {
    return this.value;
  }

  @Override
  public boolean equals(Object o) {
    return (o instanceof IdentityRef) && identical(((IdentityRef) o).value, this.value);
  }

  @Override
  public int hashCode() {
    return System.identityHashCode(this.value);
  }

  @Override
  public String toString() {
    return "IdentityRef<" + this.value + ">";
  }
}