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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;

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

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.JSTypeRegistry;
import com.google.javascript.rhino.jstype.StaticTypedScope;
import java.io.Serializable;
import java.util.Set;
import java.util.function.Consumer;
import org.jspecify.nullness.Nullable;

/**
 * When parsing a jsdoc, a type-annotation string is parsed to a type AST. Somewhat confusingly, we
 * use the Node class both for type ASTs and for the source-code AST. JSTypeExpression wraps a type
 * AST. During type checking, type ASTs are evaluated to JavaScript types.
 */
public final class JSTypeExpression implements Serializable {
  private static final long serialVersionUID = 1L;

  private static final String IMPLICIT_TEMPLATE_BOUND_SOURCE = "";

  static final JSTypeExpression IMPLICIT_TEMPLATE_BOUND =
      new JSTypeExpression(new Node(Token.QMARK), IMPLICIT_TEMPLATE_BOUND_SOURCE);

  static {
    IMPLICIT_TEMPLATE_BOUND
        .getRoot()
        .setStaticSourceFile(
            new SimpleSourceFile(
                IMPLICIT_TEMPLATE_BOUND_SOURCE, StaticSourceFile.SourceKind.STRONG));
  }

  /** The root of the AST. */
  private final Node root;

  /** The source name where the type expression appears. */
  private final String sourceName;

  public JSTypeExpression(Node root, String sourceName) {
    this.root = root;
    this.sourceName = sourceName;
  }

  /** Replaces given names in this type expression with unknown */
  public JSTypeExpression replaceNamesWithUnknownType(Set names) {
    Node oldExprRoot = this.root.cloneTree();
    Node newExprRoot = replaceNames(oldExprRoot, names);
    JSTypeExpression newTypeExpression = new JSTypeExpression(newExprRoot, sourceName);
    return newTypeExpression;
  }

  /**
   * Recursively traverse over the type tree and replace matched types with unknown type
   *
   * @param n Root of the JsTypeExpression on which replacement is applied
   * @param names The set of names to replace in this type expression
   * @return the new root after replacing the names
   */
  private static @Nullable Node replaceNames(Node n, Set names) {
    if (n == null) {
      return null;
    }
    for (Node child = n.getFirstChild(); child != null; ) {
      final Node next = child.getNext();
      replaceNames(child, names);
      child = next;
    }
    if (n.isStringLit() && names.contains(n.getString())) {
      Node qMark = new Node(Token.QMARK);
      qMark.addChildrenToBack(n.removeChildren());
      if (n.hasParent()) {
        n.replaceWith(qMark);
      }
      return qMark;
    }
    return n;
  }

  /** Returns a list of all type nodes in this type expression. */
  public ImmutableList getAllTypeNodes() {
    ImmutableList.Builder builder = ImmutableList.builder();
    visitAllTypeNodes(this.root, builder::add);
    return builder.build();
  }

  /** Returns a set of all string names in this type expression */
  public ImmutableSet getAllTypeNames() {
    ImmutableSet.Builder builder = ImmutableSet.builder();
    visitAllTypeNodes(this.root, (n) -> builder.add(n.getString()));
    return builder.build();
  }

  /** Recursively traverse the type tree and visit all type nodes. */
  private static void visitAllTypeNodes(Node n, Consumer visitor) {
    if (n == null) {
      return;
    }
    for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
      visitAllTypeNodes(child, visitor);
    }
    if (n.isStringLit()) {
      visitor.accept(n);
    }
  }

  /** Make the given type expression into an optional type expression, if possible. */
  public static JSTypeExpression makeOptionalArg(JSTypeExpression expr) {
    if (expr.isOptionalArg() || expr.isVarArgs()) {
      return expr;
    } else {
      Node equals = new Node(Token.EQUALS, expr.root);
      equals.clonePropsFrom(expr.root);
      return new JSTypeExpression(equals, expr.sourceName);
    }
  }

  /** @return Whether this expression denotes an optional {@code @param}. */
  public boolean isOptionalArg() {
    return root.getToken() == Token.EQUALS;
  }

  /** @return Whether this expression denotes a rest args {@code @param}. */
  public boolean isVarArgs() {
    return root.getToken() == Token.ITER_REST;
  }

  /** Evaluates the type expression into a {@code JSType} object. */
  public JSType evaluate(StaticTypedScope scope, JSTypeRegistry registry) {
    JSType type = registry.createTypeFromCommentNode(root, sourceName, scope);
    root.setJSType(type);
    return type;
  }

  /** Does this object represent a type expression that is equivalent to the other one? */
  public boolean isEquivalentTo(@Nullable JSTypeExpression other) {
    return other != null && root.isEquivalentTo(other.root);
  }

  /**
   * @return The source for this type expression. Note that it will not contain an expression if
   *     there's an @override tag.
   */
  public Node getRoot() {
    return root;
  }

  public String getSourceName() {
    return this.sourceName;
  }

  @Override
  public String toString() {
    return "type: " + root.toStringTree();
  }

  public JSTypeExpression copy() {
    return new JSTypeExpression(root.cloneTree(), sourceName);
  }

  /** Whether this expression is an explicit unknown template bound. */
  public boolean isExplicitUnknownTemplateBound() {
    return identical(root.getToken(), Token.QMARK)
        && !root.hasChildren()
        && !sourceName.equals(IMPLICIT_TEMPLATE_BOUND_SOURCE);
  }

  /**
   * Returns a set of keys of all record types (e.g. {{key : string }}) present in this
   * JSTypeExpression.
   */
  public ImmutableSet getRecordPropertyNames() {
    ImmutableSet.Builder builder = ImmutableSet.builder();
    getRecordPropertyNamesRecursive(this.root, builder);
    return builder.build();
  }

  private static void getRecordPropertyNamesRecursive(Node n, ImmutableSet.Builder names) {
    if (n == null) {
      return;
    }

    for (Node child = n.getFirstChild(); child != null; child = child.getNext()) {
      getRecordPropertyNamesRecursive(child, names);
    }
    if (n.isStringKey()) {
      names.add(n.getString());
    }
  }
}




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