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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 2015 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 static com.google.common.base.Preconditions.checkArgument;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Sets;
import com.google.javascript.rhino.ErrorReporter;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.StaticTypedRef;
import com.google.javascript.rhino.jstype.StaticTypedSlot;

/**
 * {@link AbstractVar} subclass for use with {@link TypedScope}.
 *
 * Note that this class inherits its {@link #equals} and {@link #hashCode} implementations from
 * {@link ScopedName}, which does not include any type information. This is necessary because {@code
 * Var}-keyed maps are used across multiple top scopes, but it comes with the caveat that if {@code
 * TypedVar} instances are stored in a set, the type information is at risk of disappearing if an
 * untyped (or differently typed) var is added for the same symbol.
 */
public class TypedVar extends AbstractVar
    implements StaticTypedSlot, StaticTypedRef {

  private JSType type;
  // The next two fields and the associated methods are only used by
  // TypeInference.java. Maybe there is a way to avoid having them in all typed variable instances.
  private boolean markedEscaped = false;
  private boolean markedAssignedExactlyOnce = false;

  /**
   * Whether the variable's type has been inferred or is declared. An inferred
   * type may change over time (as more code is discovered), whereas a
   * declared type is a static contract that must be matched.
   */
  private final boolean typeInferred;

  // includes nodes that in plain JS semantics are not 'declarations', but that the type system
  // & compiler treat as declarations.
  private static final ImmutableSet NAME_NODE_TYPES =
      Sets.immutableEnumSet(
          Token.NAME,
          Token.THIS, // `if ('prop' in this) {` creates a TypedVar `this.prop` requiring a node
          Token.IMPORT_STAR,
          Token.EXPR_RESULT, // implicit variables from goog.provide
          Token.EXPORT, // tracks the *default* export
          Token.GETPROP,
          Token.FUNCTION,
          Token.STRING_KEY,
          Token.SETTER_DEF,
          Token.GETTER_DEF,
          Token.MEMBER_FUNCTION_DEF,
          Token.MODULE_BODY); // for the implicit exports object in a module

  TypedVar(boolean inferred, String name, Node nameNode, JSType type,
      TypedScope scope, int index, CompilerInput input) {
    super(name, nameNode, scope, index, input, /* implicitGoogNamespaceDefinition= */ null);
    if (nameNode != null) {
      checkArgument(
          NAME_NODE_TYPES.contains(nameNode.getToken()),
          "Invalid name node token %s",
          nameNode.getToken());
    }
    this.type = type;
    this.typeInferred = inferred;
  }

  /**
   * Gets this variable's type. To know whether this type has been inferred,
   * see {@code #isTypeInferred()}.
   */
  @Override
  public JSType getType() {
    return type;
  }

  void setType(JSType type) {
    this.type = type;
  }

  void resolveType(ErrorReporter errorReporter) {
    if (type != null) {
      this.type = type.resolve(errorReporter);
    }
  }

  /**
   * Returns whether this variable's type is inferred. To get the variable's
   * type, see {@link #getType()}.
   */
  @Override
  public boolean isTypeInferred() {
    return typeInferred;
  }

  public String getInputName() {
    if (getInput() == null) {
      return "";
    }
    return getInput().getName();
  }

  @Override
  public String toString() {
    return "Var " + getName() + "{" + type + "}";
  }

  void markEscaped() {
    markedEscaped = true;
  }

  boolean isMarkedEscaped() {
    return markedEscaped;
  }

  void markAssignedExactlyOnce() {
    markedAssignedExactlyOnce = true;
  }

  boolean isMarkedAssignedExactlyOnce() {
    return markedAssignedExactlyOnce;
  }
}