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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. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2006 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;

import com.google.javascript.jscomp.AnalyzePrototypeProperties.NameInfo;
import com.google.javascript.jscomp.AnalyzePrototypeProperties.Symbol;
import com.google.javascript.rhino.Node;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Removes unused properties from prototypes.
 *
 * @author [email protected] (Nick Santos)
 */
class RemoveUnusedPrototypeProperties implements CompilerPass {

  private static final Logger logger =
    Logger.getLogger(RemoveUnusedPrototypeProperties.class.getName());

  private final AbstractCompiler compiler;
  private final boolean canModifyExterns;
  private final boolean anchorUnusedVars;

  /**
   * Creates a new pass for removing unused prototype properties, based
   * on the uniqueness of property names.
   * @param compiler The compiler.
   * @param canModifyExterns If true, then we can remove prototype
   *     properties that are declared in the externs file.
   * @param anchorUnusedVars If true, then we must keep unused variables
   *     and the prototype properties they reference, even if they are
   *     never used.
   */
  RemoveUnusedPrototypeProperties(AbstractCompiler compiler,
      boolean canModifyExterns,
      boolean anchorUnusedVars) {
    this.compiler = compiler;
    this.canModifyExterns = canModifyExterns;
    this.anchorUnusedVars = anchorUnusedVars;
  }

  @Override
  public void process(Node externRoot, Node root) {
    AnalyzePrototypeProperties analyzer =
        new AnalyzePrototypeProperties(compiler,
            null /* no module graph */, canModifyExterns, anchorUnusedVars);
    analyzer.process(externRoot, root);
    // Remove all properties under a given name if the property name is
    // never referenced.
    for (NameInfo nameInfo : analyzer.getAllNameInfo()) {
      if (!nameInfo.isReferenced()) {
        for (Symbol declaration : nameInfo.getDeclarations()) {
          // Code-change reporting happens at the remove methods
          declaration.remove(compiler);
        }
        if (logger.isLoggable(Level.FINE)) {
          logger.fine("Removed unused prototype property: " + nameInfo.name);
        }
      }
    }
  }
}