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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 2014 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.newtypes;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;

import com.google.common.base.Preconditions;
import com.google.javascript.rhino.JSTypeExpression;
import com.google.javascript.rhino.Node;
import java.io.Serializable;

/**
 *
 * @author [email protected] (Ben Lickly)
 * @author [email protected] (Dimitris Vardoulakis)
 */
public final class Typedef implements Serializable {

  private enum State {
    NOT_RESOLVED,
    DURING_RESOLUTION,
    RESOLVED
  }

  private final Node defSite;
  private State state;
  private JSTypeExpression typeExpr;
  private JSType type;

  private Typedef(Node defSite, JSTypeExpression typeExpr) {
    checkState(defSite.isQualifiedName(), defSite);
    this.defSite = defSite;
    this.state = State.NOT_RESOLVED;
    // Non-null iff the typedef is resolved
    this.type = null;
    // Non-null iff the typedef is not resolved
    this.typeExpr = typeExpr;
  }

  public static Typedef make(Node defSite, JSTypeExpression typeExpr) {
    return new Typedef(defSite, typeExpr);
  }

  public boolean isResolved() {
    return state == State.RESOLVED;
  }

  public JSType getType() {
    checkState(state == State.RESOLVED);
    return type;
  }

  // Returns null iff there is a typedef cycle
  public JSTypeExpression getTypeExpr() {
    checkState(state != State.RESOLVED);
    if (state == State.DURING_RESOLUTION) {
      return null;
    }
    state = State.DURING_RESOLUTION;
    return typeExpr;
  }

  public JSTypeExpression getTypeExprForErrorReporting() {
    checkState(state == State.DURING_RESOLUTION);
    return typeExpr;
  }

  void resolveTypedef(JSType t) {
    checkNotNull(t);
    if (state == State.RESOLVED) {
      return;
    }
    Preconditions.checkState(state == State.DURING_RESOLUTION,
        "Expected state DURING_RESOLUTION but found %s", state.toString());
    state = State.RESOLVED;
    typeExpr = null;
    type = t;
  }

  @Override
  public String toString() {
    return this.defSite.getQualifiedName();
  }
}