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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 2008 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.type;

import com.google.errorprone.annotations.CheckReturnValue;
import com.google.javascript.jscomp.graph.LatticeElement;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.jstype.JSType;
import com.google.javascript.rhino.jstype.StaticTypedScope;

/**
 * A symbol table for inferring types during data flow analysis.
 *
 * Each flow scope represents the types of all variables in the scope at a particular point in
 * the flow analysis.
 */
public interface FlowScope extends StaticTypedScope, LatticeElement {

  /**
   * Returns a flow scope with the given syntactic scope, which may be required to be a specific
   * subclass, such as TypedScope.
   */
  FlowScope withSyntacticScope(StaticTypedScope scope);

  /**
   * Returns a flow scope with the type of the given {@code symbol} updated to {@code type}.
   *
   * @throws IllegalArgumentException If no slot for this symbol exists.
   */
  @CheckReturnValue
  FlowScope inferSlotType(String symbol, JSType type);

  /**
   * Returns a flow scope with the type of the given {@code symbol} updated to {@code inferredType}.
   * Updates are not performed in-place.
   *
   * 
When traversing the control flow of a function, simple names are declared at the bottom of
   * the flow lattice. But there are far too many qualified names to be able to do this and be
   * performant. So the bottoms of qualified names are declared lazily.
   *
   * Therefore, when inferring a qualified slot, we need both the "bottom" type of the slot when
   * we enter the scope, and the current type being inferred.
   */
  @CheckReturnValue
  FlowScope inferQualifiedSlot(
      Node node, String symbol, JSType bottomType, JSType inferredType, boolean declare);

  /** Returns the underlying TypedScope. */
  StaticTypedScope getDeclarationScope();
}