chromium/v8/src/parsing/preparse-data.h

// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_PARSING_PREPARSE_DATA_H_
#define V8_PARSING_PREPARSE_DATA_H_

#include <memory>

#include "src/base/vector.h"
#include "src/common/globals.h"
#include "src/handles/handles.h"
#include "src/handles/maybe-handles.h"
#include "src/utils/scoped-list.h"
#include "src/zone/zone-chunk-list.h"
#include "src/zone/zone-containers.h"

namespace v8 {
namespace internal {

template <typename T>
class PodArray;

class Parser;
class PreParser;
class PreparseData;
class ZonePreparseData;
class AstValueFactory;

/*

  Skipping inner functions.

  Consider the following code:
  (function eager_outer() {
    function lazy_inner() {
      let a;
      function skip_me() { a; }
    }

    return lazy_inner;
  })();

  ... lazy_inner(); ...

  When parsing the code the first time, eager_outer is parsed and lazy_inner
  (and everything inside it) is preparsed. When lazy_inner is called, we don't
  want to parse or preparse skip_me again. Instead, we want to skip over it,
  since it has already been preparsed once.

  In order to be able to do this, we need to store the information needed for
  allocating the variables in lazy_inner when we preparse it, and then later do
  scope allocation based on that data.

  We need the following data for each scope in lazy_inner's scope tree:
  For each Variable:
  - is_used
  - maybe_assigned
  - has_forced_context_allocation

  For each Scope:
  - inner_scope_calls_eval_.

  ProducedPreparseData implements storing the above mentioned data and
  ConsumedPreparseData implements restoring it (= setting the context
  allocation status of the variables in a Scope (and its subscopes) based on the
  data).

 */

struct PreparseByteDataConstants { … };

class V8_EXPORT_PRIVATE PreparseDataBuilder : public ZoneObject,
                                              public PreparseByteDataConstants { … };

class ProducedPreparseData : public ZoneObject { … };

class ConsumedPreparseData { … };

}  // namespace internal
}  // namespace v8

#endif  // V8_PARSING_PREPARSE_DATA_H_