runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc

// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/compiler/frontend/kernel_binary_flowgraph.h"

#include "vm/bootstrap.h"
#include "vm/code_descriptors.h"
#include "vm/compiler/aot/precompiler.h"
#include "vm/compiler/assembler/disassembler_kbc.h"
#include "vm/compiler/frontend/prologue_builder.h"
#include "vm/compiler/jit/compiler.h"
#include "vm/dart_entry.h"
#include "vm/longjump.h"
#include "vm/object_store.h"
#include "vm/resolver.h"
#include "vm/stack_frame.h"

#if !defined(DART_PRECOMPILED_RUNTIME)

namespace dart {

#if defined(DART_USE_INTERPRETER)
DEFINE_FLAG(bool, dump_kernel_bytecode, false, "Dump kernel bytecode");
#endif  // defined(DART_USE_INTERPRETER)

namespace kernel {

#define Z (zone_)
#define H (translation_helper_)
#define T (type_translator_)
#define I Isolate::Current()
#define B (flow_graph_builder_)

static bool IsFieldInitializer(const Function& function, Zone* zone) {
  return (function.kind() == RawFunction::kImplicitStaticFinalGetter) &&
         String::Handle(zone, function.name())
             .StartsWith(Symbols::InitPrefix());
}

void FunctionNodeHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kStart: {
      Tag tag = helper_->ReadTag();  // read tag.
      ASSERT(tag == kFunctionNode);
      if (++next_read_ == field) return;
    }
    /* Falls through */
    case kPosition:
      position_ = helper_->ReadPosition();  // read position.
      if (++next_read_ == field) return;
      /* Falls through */
    case kEndPosition:
      end_position_ = helper_->ReadPosition();  // read end position.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAsyncMarker:
      async_marker_ = static_cast<AsyncMarker>(helper_->ReadByte());
      if (++next_read_ == field) return;
      /* Falls through */
    case kDartAsyncMarker:
      dart_async_marker_ = static_cast<AsyncMarker>(
          helper_->ReadByte());  // read dart async marker.
      if (++next_read_ == field) return;
      /* Falls through */
    case kTypeParameters:
      helper_->SkipTypeParametersList();  // read type parameters.
      if (++next_read_ == field) return;
      /* Falls through */
    case kTotalParameterCount:
      total_parameter_count_ =
          helper_->ReadUInt();  // read total parameter count.
      if (++next_read_ == field) return;
      /* Falls through */
    case kRequiredParameterCount:
      required_parameter_count_ =
          helper_->ReadUInt();  // read required parameter count.
      if (++next_read_ == field) return;
      /* Falls through */
    case kPositionalParameters:
      helper_->SkipListOfVariableDeclarations();  // read positionals.
      if (++next_read_ == field) return;
      /* Falls through */
    case kNamedParameters:
      helper_->SkipListOfVariableDeclarations();  // read named.
      if (++next_read_ == field) return;
      /* Falls through */
    case kReturnType:
      helper_->SkipDartType();  // read return type.
      if (++next_read_ == field) return;
      /* Falls through */
    case kBody:
      if (helper_->ReadTag() == kSomething)
        helper_->SkipStatement();  // read body.
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

void TypeParameterHelper::ReadUntilExcluding(Field field) {
  for (; next_read_ < field; ++next_read_) {
    switch (next_read_) {
      case kFlags:
        flags_ = helper_->ReadFlags();
        break;
      case kAnnotations:
        helper_->SkipListOfExpressions();  // read annotations.
        break;
      case kName:
        name_index_ = helper_->ReadStringReference();  // read name index.
        break;
      case kBound:
        helper_->SkipDartType();
        break;
      case kDefaultType:
        if (helper_->ReadTag() == kSomething) {
          helper_->SkipDartType();
        }
        break;
      case kEnd:
        return;
    }
  }
}

void VariableDeclarationHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kPosition:
      position_ = helper_->ReadPosition();  // read position.
      if (++next_read_ == field) return;
      /* Falls through */
    case kEqualPosition:
      equals_position_ = helper_->ReadPosition();  // read equals position.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations:
      helper_->SkipListOfExpressions();  // read annotations.
      if (++next_read_ == field) return;
      /* Falls through */
    case kFlags:
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
      /* Falls through */
    case kNameIndex:
      name_index_ = helper_->ReadStringReference();  // read name index.
      if (++next_read_ == field) return;
      /* Falls through */
    case kType:
      helper_->SkipDartType();  // read type.
      if (++next_read_ == field) return;
      /* Falls through */
    case kInitializer:
      if (helper_->ReadTag() == kSomething)
        helper_->SkipExpression();  // read initializer.
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

FieldHelper::FieldHelper(KernelReaderHelper* helper, intptr_t offset)
    : helper_(helper),
      next_read_(kStart),
      has_function_literal_initializer_(false) {
  helper_->SetOffset(offset);
}

void FieldHelper::ReadUntilExcluding(Field field,
                                     bool detect_function_literal_initializer) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kStart: {
      Tag tag = helper_->ReadTag();  // read tag.
      ASSERT(tag == kField);
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kCanonicalName:
      canonical_name_ =
          helper_->ReadCanonicalNameReference();  // read canonical_name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSourceUriIndex:
      source_uri_index_ = helper_->ReadUInt();  // read source_uri_index.
      helper_->set_current_script_id(source_uri_index_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kPosition:
      position_ = helper_->ReadPosition(false);  // read position.
      helper_->RecordTokenPosition(position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kEndPosition:
      end_position_ = helper_->ReadPosition(false);  // read end position.
      helper_->RecordTokenPosition(end_position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kFlags:
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
      /* Falls through */
    case kName:
      helper_->SkipName();  // read name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations: {
      annotation_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < annotation_count_; ++i) {
        helper_->SkipExpression();  // read ith expression.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kType:
      helper_->SkipDartType();  // read type.
      if (++next_read_ == field) return;
      /* Falls through */
    case kInitializer:
      if (helper_->ReadTag() == kSomething) {
        if (detect_function_literal_initializer &&
            helper_->PeekTag() == kFunctionExpression) {
          AlternativeReadingScope alt(&helper_->reader_);
          Tag tag = helper_->ReadTag();
          ASSERT(tag == kFunctionExpression);
          helper_->ReadPosition();  // read position.

          FunctionNodeHelper helper(helper_);
          helper.ReadUntilIncluding(FunctionNodeHelper::kEndPosition);

          has_function_literal_initializer_ = true;
          function_literal_start_ = helper.position_;
          function_literal_end_ = helper.end_position_;
        }
        helper_->SkipExpression();  // read initializer.
      }
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

void ProcedureHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kStart: {
      Tag tag = helper_->ReadTag();  // read tag.
      ASSERT(tag == kProcedure);
      if (++next_read_ == field) return;
    }
    /* Falls through */
    case kCanonicalName:
      canonical_name_ =
          helper_->ReadCanonicalNameReference();  // read canonical_name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSourceUriIndex:
      source_uri_index_ = helper_->ReadUInt();  // read source_uri_index.
      helper_->set_current_script_id(source_uri_index_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kPosition:
      position_ = helper_->ReadPosition(false);  // read position.
      helper_->RecordTokenPosition(position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kEndPosition:
      end_position_ = helper_->ReadPosition(false);  // read end position.
      helper_->RecordTokenPosition(end_position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kKind:
      kind_ = static_cast<Kind>(helper_->ReadByte());
      if (++next_read_ == field) return;
      /* Falls through */
    case kFlags:
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
      /* Falls through */
    case kName:
      helper_->SkipName();  // read name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations: {
      annotation_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < annotation_count_; ++i) {
        helper_->SkipExpression();  // read ith expression.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kForwardingStubSuperTarget:
      if (helper_->ReadTag() == kSomething) {
        forwarding_stub_super_target_ = helper_->ReadCanonicalNameReference();
      }
      if (++next_read_ == field) return;
      /* Falls through */
    case kForwardingStubInterfaceTarget:
      if (helper_->ReadTag() == kSomething) {
        helper_->ReadCanonicalNameReference();
      }
      if (++next_read_ == field) return;
      /* Falls through */
    case kFunction:
      if (helper_->ReadTag() == kSomething)
        helper_->SkipFunctionNode();  // read function node.
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

void ConstructorHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kStart: {
      Tag tag = helper_->ReadTag();  // read tag.
      ASSERT(tag == kConstructor);
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kCanonicalName:
      canonical_name_ =
          helper_->ReadCanonicalNameReference();  // read canonical_name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSourceUriIndex:
      source_uri_index_ = helper_->ReadUInt();  // read source_uri_index.
      helper_->set_current_script_id(source_uri_index_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kPosition:
      position_ = helper_->ReadPosition();  // read position.
      helper_->RecordTokenPosition(position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kEndPosition:
      end_position_ = helper_->ReadPosition();  // read end position.
      helper_->RecordTokenPosition(end_position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kFlags:
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
      /* Falls through */
    case kName:
      helper_->SkipName();  // read name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations: {
      annotation_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < annotation_count_; ++i) {
        helper_->SkipExpression();  // read ith expression.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kFunction:
      helper_->SkipFunctionNode();  // read function.
      if (++next_read_ == field) return;
      /* Falls through */
    case kInitializers: {
      intptr_t list_length =
          helper_->ReadListLength();  // read initializers list length.
      for (intptr_t i = 0; i < list_length; i++) {
        helper_->SkipInitializer();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kEnd:
      return;
  }
}

void ClassHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kStart: {
      Tag tag = helper_->ReadTag();  // read tag.
      ASSERT(tag == kClass);
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kCanonicalName:
      canonical_name_ =
          helper_->ReadCanonicalNameReference();  // read canonical_name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSourceUriIndex:
      source_uri_index_ = helper_->ReadUInt();  // read source_uri_index.
      helper_->set_current_script_id(source_uri_index_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kPosition:
      position_ = helper_->ReadPosition(false);  // read position.
      helper_->RecordTokenPosition(position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kEndPosition:
      end_position_ = helper_->ReadPosition();  // read end position.
      helper_->RecordTokenPosition(end_position_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kFlags:
      flags_ = helper_->ReadFlags();  // read flags.
      if (++next_read_ == field) return;
      /* Falls through */
    case kNameIndex:
      name_index_ = helper_->ReadStringReference();  // read name index.
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations: {
      annotation_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < annotation_count_; ++i) {
        helper_->SkipExpression();  // read ith expression.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kTypeParameters:
      helper_->SkipTypeParametersList();  // read type parameters.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSuperClass: {
      Tag type_tag = helper_->ReadTag();  // read super class type (part 1).
      if (type_tag == kSomething) {
        helper_->SkipDartType();  // read super class type (part 2).
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kMixinType: {
      Tag type_tag = helper_->ReadTag();  // read mixin type (part 1).
      if (type_tag == kSomething) {
        helper_->SkipDartType();  // read mixin type (part 2).
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kImplementedClasses:
      helper_->SkipListOfDartTypes();  // read implemented_classes.
      if (++next_read_ == field) return;
      /* Falls through */
    case kFields: {
      intptr_t list_length =
          helper_->ReadListLength();  // read fields list length.
      for (intptr_t i = 0; i < list_length; i++) {
        FieldHelper field_helper(helper_);
        field_helper.ReadUntilExcluding(FieldHelper::kEnd);  // read field.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kConstructors: {
      intptr_t list_length =
          helper_->ReadListLength();  // read constructors list length.
      for (intptr_t i = 0; i < list_length; i++) {
        ConstructorHelper constructor_helper(helper_);
        constructor_helper.ReadUntilExcluding(
            ConstructorHelper::kEnd);  // read constructor.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kProcedures: {
      procedure_count_ = helper_->ReadListLength();  // read procedures #.
      for (intptr_t i = 0; i < procedure_count_; i++) {
        ProcedureHelper procedure_helper(helper_);
        procedure_helper.ReadUntilExcluding(
            ProcedureHelper::kEnd);  // read procedure.
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kClassIndex:
      // Read class index.
      for (intptr_t i = 0; i < procedure_count_; ++i) {
        helper_->reader_.ReadUInt32();
      }
      helper_->reader_.ReadUInt32();
      helper_->reader_.ReadUInt32();
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

void LibraryHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kFlags: {
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kCanonicalName:
      canonical_name_ =
          helper_->ReadCanonicalNameReference();  // read canonical_name.
      if (++next_read_ == field) return;
      /* Falls through */
    case kName:
      name_index_ = helper_->ReadStringReference();  // read name index.
      if (++next_read_ == field) return;
      /* Falls through */
    case kSourceUriIndex:
      source_uri_index_ = helper_->ReadUInt();  // read source_uri_index.
      helper_->set_current_script_id(source_uri_index_);
      if (++next_read_ == field) return;
      /* Falls through */
    case kAnnotations:
      helper_->SkipListOfExpressions();  // read annotations.
      if (++next_read_ == field) return;
      /* Falls through */
    case kDependencies: {
      intptr_t dependency_count = helper_->ReadUInt();  // read list length.
      for (intptr_t i = 0; i < dependency_count; ++i) {
        helper_->SkipLibraryDependency();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kAdditionalExports: {
      intptr_t name_count = helper_->ReadUInt();
      for (intptr_t i = 0; i < name_count; ++i) {
        helper_->SkipCanonicalNameReference();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kParts: {
      intptr_t part_count = helper_->ReadUInt();  // read list length.
      for (intptr_t i = 0; i < part_count; ++i) {
        helper_->SkipLibraryPart();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kTypedefs: {
      intptr_t typedef_count = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < typedef_count; i++) {
        helper_->SkipLibraryTypedef();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kClasses: {
      class_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < class_count_; ++i) {
        ClassHelper class_helper(helper_);
        class_helper.ReadUntilExcluding(ClassHelper::kEnd);
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kToplevelField: {
      intptr_t field_count = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < field_count; ++i) {
        FieldHelper field_helper(helper_);
        field_helper.ReadUntilExcluding(FieldHelper::kEnd);
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kToplevelProcedures: {
      procedure_count_ = helper_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < procedure_count_; ++i) {
        ProcedureHelper procedure_helper(helper_);
        procedure_helper.ReadUntilExcluding(ProcedureHelper::kEnd);
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kLibraryIndex:
      // Read library index.
      for (intptr_t i = 0; i < class_count_; ++i) {
        helper_->reader_.ReadUInt32();
      }
      helper_->reader_.ReadUInt32();
      helper_->reader_.ReadUInt32();
      for (intptr_t i = 0; i < procedure_count_; ++i) {
        helper_->reader_.ReadUInt32();
      }
      helper_->reader_.ReadUInt32();
      helper_->reader_.ReadUInt32();
      if (++next_read_ == field) return;
      /* Falls through */
    case kEnd:
      return;
  }
}

void LibraryDependencyHelper::ReadUntilExcluding(Field field) {
  if (field <= next_read_) return;

  // Ordered with fall-through.
  switch (next_read_) {
    case kFileOffset: {
      helper_->ReadPosition();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kFlags: {
      flags_ = helper_->ReadFlags();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kAnnotations: {
      helper_->SkipListOfExpressions();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kTargetLibrary: {
      target_library_canonical_name_ = helper_->ReadCanonicalNameReference();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kName: {
      name_index_ = helper_->ReadStringReference();
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kCombinators: {
      intptr_t count = helper_->ReadListLength();
      for (intptr_t i = 0; i < count; ++i) {
        // Skip flags
        helper_->SkipBytes(1);
        // Skip list of names.
        helper_->SkipListOfStrings();
      }
      if (++next_read_ == field) return;
    }
      /* Falls through */
    case kEnd:
      return;
  }
}

MetadataHelper::MetadataHelper(StreamingFlowGraphBuilder* builder)
    : builder_(builder),
      translation_helper_(builder->translation_helper_),
      mappings_offset_(0),
      mappings_num_(0),
      last_node_offset_(0),
      last_mapping_index_(0) {}

void MetadataHelper::SetMetadataMappings(intptr_t mappings_offset,
                                         intptr_t mappings_num) {
  ASSERT((mappings_offset_ == 0) && (mappings_num_ == 0));
  ASSERT((mappings_offset != 0) && (mappings_num != 0));
  mappings_offset_ = mappings_offset;
  mappings_num_ = mappings_num;

#ifdef DEBUG
  // Verify that node offsets are sorted.
  {
    Reader reader(H.metadata_mappings());
    reader.set_offset(mappings_offset);

    intptr_t prev_node_offset = 0;
    for (intptr_t i = 0; i < mappings_num; ++i) {
      intptr_t node_offset = reader.ReadUInt32();
      intptr_t md_offset = reader.ReadUInt32();

      ASSERT((node_offset > 0) && (md_offset >= 0));
      ASSERT(node_offset > prev_node_offset);
      prev_node_offset = node_offset;
    }
  }
#endif  // DEBUG

  last_node_offset_ = kIntptrMax;
  last_mapping_index_ = 0;
}

intptr_t MetadataHelper::FindMetadataMapping(intptr_t node_offset) {
  const intptr_t kUInt32Size = 4;
  ASSERT(mappings_num_ > 0);

  Reader reader(H.metadata_mappings());

  intptr_t left = 0;
  intptr_t right = mappings_num_ - 1;
  while (left < right) {
    intptr_t mid = ((right - left) / 2) + left;
    intptr_t mid_node_offset =
        reader.ReadUInt32At(mappings_offset_ + mid * 2 * kUInt32Size);

    if (node_offset < mid_node_offset) {
      right = mid - 1;
    } else if (node_offset > mid_node_offset) {
      left = mid + 1;
    } else {
      return mid;  // Exact match found.
    }
  }
  ASSERT((0 <= left) && (left <= mappings_num_));

  // Approximate match is found. Make sure it has an offset greater or equal
  // to the given node offset.
  if (left < mappings_num_) {
    intptr_t found_node_offset =
        reader.ReadUInt32At(mappings_offset_ + left * 2 * kUInt32Size);

    if (found_node_offset < node_offset) {
      ++left;
    }
  }
  ASSERT((left == mappings_num_) ||
         static_cast<intptr_t>(reader.ReadUInt32At(
             mappings_offset_ + left * 2 * kUInt32Size)) >= node_offset);

  return left;
}

intptr_t MetadataHelper::GetNextMetadataPayloadOffset(intptr_t node_offset) {
  builder_->EnsureMetadataIsScanned();

  if (mappings_num_ == 0) {
    return -1;  // No metadata.
  }

  node_offset += builder_->data_program_offset_;

  // Nodes are parsed in linear order most of the time, so do the search
  // only if looking back.
  if (node_offset < last_node_offset_) {
    last_mapping_index_ = FindMetadataMapping(node_offset);
  }

  intptr_t index = last_mapping_index_;
  intptr_t mapping_node_offset = 0;
  intptr_t mapping_md_offset = -1;

  Reader reader(H.metadata_mappings());
  const intptr_t kUInt32Size = 4;
  reader.set_offset(mappings_offset_ + index * 2 * kUInt32Size);

  for (; index < mappings_num_; ++index) {
    mapping_node_offset = reader.ReadUInt32();
    mapping_md_offset = reader.ReadUInt32();

    if (mapping_node_offset >= node_offset) {
      break;
    }
  }

  last_mapping_index_ = index;
  last_node_offset_ = node_offset;

  if ((index < mappings_num_) && (mapping_node_offset == node_offset)) {
    ASSERT(mapping_md_offset >= 0);
    return mapping_md_offset;
  } else {
    return -1;
  }
}

bool DirectCallMetadataHelper::ReadMetadata(intptr_t node_offset,
                                            NameIndex* target_name,
                                            bool* check_receiver_for_null) {
  intptr_t md_offset = GetNextMetadataPayloadOffset(node_offset);
  if (md_offset < 0) {
    return false;
  }

  AlternativeReadingScope alt(&builder_->reader_, &H.metadata_payloads(),
                              md_offset);

  *target_name = builder_->ReadCanonicalNameReference();
  *check_receiver_for_null = builder_->ReadBool();
  return true;
}

DirectCallMetadata DirectCallMetadataHelper::GetDirectTargetForPropertyGet(
    intptr_t node_offset) {
  NameIndex kernel_name;
  bool check_receiver_for_null = false;
  if (!ReadMetadata(node_offset, &kernel_name, &check_receiver_for_null)) {
    return DirectCallMetadata(Function::null_function(), false);
  }

  if (H.IsProcedure(kernel_name) && !H.IsGetter(kernel_name)) {
    // Tear-off. Use method extractor as direct call target.
    const String& method_name = H.DartMethodName(kernel_name);
    const Function& target_method = Function::ZoneHandle(
        builder_->zone_,
        builder_->LookupMethodByMember(kernel_name, method_name));
    const String& getter_name = H.DartGetterName(kernel_name);
    return DirectCallMetadata(
        Function::ZoneHandle(builder_->zone_,
                             target_method.GetMethodExtractor(getter_name)),
        check_receiver_for_null);
  } else {
    const String& getter_name = H.DartGetterName(kernel_name);
    const Function& target = Function::ZoneHandle(
        builder_->zone_,
        builder_->LookupMethodByMember(kernel_name, getter_name));
    ASSERT(target.IsGetterFunction() || target.IsImplicitGetterFunction());
    return DirectCallMetadata(target, check_receiver_for_null);
  }
}

DirectCallMetadata DirectCallMetadataHelper::GetDirectTargetForPropertySet(
    intptr_t node_offset) {
  NameIndex kernel_name;
  bool check_receiver_for_null = false;
  if (!ReadMetadata(node_offset, &kernel_name, &check_receiver_for_null)) {
    return DirectCallMetadata(Function::null_function(), false);
  }

  const String& method_name = H.DartSetterName(kernel_name);
  const Function& target = Function::ZoneHandle(
      builder_->zone_,
      builder_->LookupMethodByMember(kernel_name, method_name));
  ASSERT(target.IsSetterFunction() || target.IsImplicitSetterFunction());

  return DirectCallMetadata(target, check_receiver_for_null);
}

DirectCallMetadata DirectCallMetadataHelper::GetDirectTargetForMethodInvocation(
    intptr_t node_offset) {
  NameIndex kernel_name;
  bool check_receiver_for_null = false;
  if (!ReadMetadata(node_offset, &kernel_name, &check_receiver_for_null)) {
    return DirectCallMetadata(Function::null_function(), false);
  }

  const String& method_name = H.DartProcedureName(kernel_name);
  const Function& target = Function::ZoneHandle(
      builder_->zone_,
      builder_->LookupMethodByMember(kernel_name, method_name));

  return DirectCallMetadata(target, check_receiver_for_null);
}

bool ProcedureAttributesMetadataHelper::ReadMetadata(
    intptr_t node_offset,
    ProcedureAttributesMetadata* metadata) {
  intptr_t md_offset = GetNextMetadataPayloadOffset(node_offset);
  if (md_offset < 0) {
    return false;
  }

  AlternativeReadingScope alt(&builder_->reader_, &H.metadata_payloads(),
                              md_offset);

  const int kDynamicUsesBit = 1 << 0;
  const int kNonThisUsesBit = 1 << 1;
  const int kTearOffUsesBit = 1 << 2;

  const uint8_t flags = builder_->ReadByte();
  metadata->has_dynamic_invocations =
      (flags & kDynamicUsesBit) == kDynamicUsesBit;
  metadata->has_non_this_uses = (flags & kNonThisUsesBit) == kNonThisUsesBit;
  metadata->has_tearoff_uses = (flags & kTearOffUsesBit) == kTearOffUsesBit;
  return true;
}

ProcedureAttributesMetadata
ProcedureAttributesMetadataHelper::GetProcedureAttributes(
    intptr_t node_offset) {
  ProcedureAttributesMetadata metadata;
  ReadMetadata(node_offset, &metadata);
  return metadata;
}

InferredTypeMetadata InferredTypeMetadataHelper::GetInferredType(
    intptr_t node_offset) {
  const intptr_t md_offset = GetNextMetadataPayloadOffset(node_offset);
  if (md_offset < 0) {
    return InferredTypeMetadata(kDynamicCid, true);
  }

  AlternativeReadingScope alt(&builder_->reader_, &H.metadata_payloads(),
                              md_offset);

  const NameIndex kernel_name = builder_->ReadCanonicalNameReference();
  const bool nullable = builder_->ReadBool();

  if (H.IsRoot(kernel_name)) {
    return InferredTypeMetadata(kDynamicCid, nullable);
  }

  const Class& klass =
      Class::Handle(builder_->zone_, H.LookupClassByKernelClass(kernel_name));
  ASSERT(!klass.IsNull());

  intptr_t cid = klass.id();
  if (cid == kClosureCid) {
    // VM uses more specific function types and doesn't expect instances of
    // _Closure class, so inferred _Closure class doesn't make sense for the VM.
    cid = kDynamicCid;
  }

  return InferredTypeMetadata(cid, nullable);
}

#if defined(DART_USE_INTERPRETER)
void BytecodeMetadataHelper::ReadMetadata(const Function& function) {
  const intptr_t node_offset = function.kernel_offset();
  const intptr_t md_offset = GetNextMetadataPayloadOffset(node_offset);
  if (md_offset < 0) {
    return;
  }

  AlternativeReadingScope alt(&builder_->reader_, &H.metadata_payloads(),
                              md_offset);

  // Create object pool and read pool entries.
  const intptr_t obj_count = builder_->reader_.ReadListLength();
  const ObjectPool& pool =
      ObjectPool::Handle(builder_->zone_, ObjectPool::New(obj_count));
  ReadPoolEntries(function, function, pool, 0);

  // Read bytecode and attach to function.
  const Code& bytecode = Code::Handle(builder_->zone_, ReadBytecode(pool));
  function.AttachBytecode(bytecode);

  // Read exceptions table.
  ReadExceptionsTable(bytecode);

  if (FLAG_dump_kernel_bytecode) {
    KernelBytecodeDisassembler::Disassemble(function);
  }

  // Read closures.
  Function& closure = Function::Handle(builder_->zone_);
  Code& closure_bytecode = Code::Handle(builder_->zone_);
  intptr_t num_closures = builder_->ReadListLength();
  for (intptr_t i = 0; i < num_closures; i++) {
    intptr_t closure_index = builder_->ReadUInt();
    ASSERT(closure_index < obj_count);
    closure ^= pool.ObjectAt(closure_index);

    // Read closure bytecode and attach to closure function.
    closure_bytecode = ReadBytecode(pool);
    closure.AttachBytecode(closure_bytecode);

    // Read closure exceptions table.
    ReadExceptionsTable(closure_bytecode);

    if (FLAG_dump_kernel_bytecode) {
      KernelBytecodeDisassembler::Disassemble(closure);
    }
  }
}

intptr_t BytecodeMetadataHelper::ReadPoolEntries(const Function& function,
                                                 const Function& inner_function,
                                                 const ObjectPool& pool,
                                                 intptr_t from_index) {
  // These enums and the code below reading the constant pool from kernel must
  // be kept in sync with pkg/vm/lib/bytecode/constant_pool.dart.
  enum ConstantPoolTag {
    kInvalid,
    kNull,
    kString,
    kInt,
    kDouble,
    kBool,
    kArgDesc,
    kICData,
    kStaticICData,
    kField,
    kFieldOffset,
    kClass,
    kTypeArgumentsFieldOffset,
    kTearOff,
    kType,
    kTypeArguments,
    kList,
    kInstance,
    kSymbol,
    kTypeArgumentsForInstanceAllocation,
    kContextOffset,
    kClosureFunction,
    kEndClosureFunctionScope,
    kNativeEntry,
    kSubtypeTestCache,
  };

  enum InvocationKind {
    method,  // x.foo(...) or foo(...)
    getter,  // x.foo
    setter   // x.foo = ...
  };

  Object& obj = Object::Handle(builder_->zone_);
  Object& elem = Object::Handle(builder_->zone_);
  Array& array = Array::Handle(builder_->zone_);
  Field& field = Field::Handle(builder_->zone_);
  Class& cls = Class::Handle(builder_->zone_);
  String& name = String::Handle(builder_->zone_);
  TypeArguments& type_args = TypeArguments::Handle(builder_->zone_);
  const intptr_t obj_count = pool.Length();
  for (intptr_t i = from_index; i < obj_count; ++i) {
    const intptr_t tag = builder_->ReadTag();
    switch (tag) {
      case ConstantPoolTag::kInvalid:
        UNREACHABLE();
      case ConstantPoolTag::kNull:
        obj = Object::null();
        break;
      case ConstantPoolTag::kString:
        obj = H.DartString(builder_->ReadStringReference()).raw();
        ASSERT(obj.IsString());
        obj = H.Canonicalize(String::Cast(obj));
        break;
      case ConstantPoolTag::kInt: {
        uint32_t low_bits = builder_->ReadUInt32();
        int64_t value = builder_->ReadUInt32();
        value = (value << 32) | low_bits;
        obj = Integer::New(value);
      } break;
      case ConstantPoolTag::kDouble: {
        uint32_t low_bits = builder_->ReadUInt32();
        uint64_t bits = builder_->ReadUInt32();
        bits = (bits << 32) | low_bits;
        double value = bit_cast<double, uint64_t>(bits);
        obj = Double::New(value);
      } break;
      case ConstantPoolTag::kBool:
        if (builder_->ReadUInt() == 1) {
          obj = Bool::True().raw();
        } else {
          obj = Bool::False().raw();
        }
        break;
      case ConstantPoolTag::kArgDesc: {
        intptr_t num_arguments = builder_->ReadUInt();
        intptr_t num_type_args = builder_->ReadUInt();
        intptr_t num_arg_names = builder_->ReadListLength();
        if (num_arg_names == 0) {
          obj = ArgumentsDescriptor::New(num_type_args, num_arguments);
        } else {
          array = Array::New(num_arg_names);
          for (intptr_t j = 0; j < num_arg_names; j++) {
            array.SetAt(j, H.DartSymbolPlain(builder_->ReadStringReference()));
          }
          obj = ArgumentsDescriptor::New(num_type_args, num_arguments, array);
        }
      } break;
      case ConstantPoolTag::kICData: {
        InvocationKind kind = static_cast<InvocationKind>(builder_->ReadByte());
        if (kind == InvocationKind::getter) {
          name = builder_->ReadNameAsGetterName().raw();
        } else if (kind == InvocationKind::setter) {
          name = builder_->ReadNameAsSetterName().raw();
        } else {
          ASSERT(kind == InvocationKind::method);
          name = builder_->ReadNameAsMethodName().raw();
        }
        intptr_t arg_desc_index = builder_->ReadUInt();
        ASSERT(arg_desc_index < i);
        array ^= pool.ObjectAt(arg_desc_index);
        // TODO(regis): Should num_args_tested be explicitly provided?
        obj = ICData::New(function, name,
                          array,  // Arguments descriptor.
                          Thread::kNoDeoptId, 1 /* num_args_tested */,
                          ICData::RebindRule::kInstance);
#if defined(TAG_IC_DATA)
        ICData::Cast(obj).set_tag(Instruction::kInstanceCall);
#endif
      } break;
      case ConstantPoolTag::kStaticICData: {
        InvocationKind kind = static_cast<InvocationKind>(builder_->ReadByte());
        NameIndex target = builder_->ReadCanonicalNameReference();
        if (H.IsConstructor(target)) {
          name = H.DartConstructorName(target).raw();
          elem = H.LookupConstructorByKernelConstructor(target);
        } else if (H.IsField(target)) {
          if (kind == InvocationKind::getter) {
            name = H.DartGetterName(target).raw();
          } else if (kind == InvocationKind::setter) {
            name = H.DartSetterName(target).raw();
          } else {
            ASSERT(kind == InvocationKind::method);
            UNIMPLEMENTED();  // TODO(regis): Revisit.
          }
          field = H.LookupFieldByKernelField(target);
          cls = field.Owner();
          elem = cls.LookupFunctionAllowPrivate(name);
        } else {
          if ((kind == InvocationKind::method) && H.IsGetter(target)) {
            UNIMPLEMENTED();  // TODO(regis): Revisit.
          }
          name = H.DartProcedureName(target).raw();
          elem = H.LookupStaticMethodByKernelProcedure(target);
        }
        ASSERT(elem.IsFunction());
        intptr_t arg_desc_index = builder_->ReadUInt();
        ASSERT(arg_desc_index < i);
        array ^= pool.ObjectAt(arg_desc_index);
        obj = ICData::New(function, name,
                          array,  // Arguments descriptor.
                          Thread::kNoDeoptId, 0 /* num_args_tested */,
                          ICData::RebindRule::kStatic);
        ICData::Cast(obj).AddTarget(Function::Cast(elem));
#if defined(TAG_IC_DATA)
        ICData::Cast(obj).set_tag(Instruction::kStaticCall);
#endif
      } break;
      case ConstantPoolTag::kField:
        obj =
            H.LookupFieldByKernelField(builder_->ReadCanonicalNameReference());
        ASSERT(obj.IsField());
        break;
      case ConstantPoolTag::kFieldOffset:
        obj =
            H.LookupFieldByKernelField(builder_->ReadCanonicalNameReference());
        ASSERT(obj.IsField());
        obj = Smi::New(Field::Cast(obj).Offset() / kWordSize);
        break;
      case ConstantPoolTag::kClass:
        obj =
            H.LookupClassByKernelClass(builder_->ReadCanonicalNameReference());
        ASSERT(obj.IsClass());
        break;
      case ConstantPoolTag::kTypeArgumentsFieldOffset:
        cls =
            H.LookupClassByKernelClass(builder_->ReadCanonicalNameReference());
        obj = Smi::New(cls.type_arguments_field_offset() / kWordSize);
        break;
      case ConstantPoolTag::kTearOff:
        obj = H.LookupStaticMethodByKernelProcedure(
            builder_->ReadCanonicalNameReference());
        ASSERT(obj.IsFunction());
        obj = Function::Cast(obj).ImplicitClosureFunction();
        ASSERT(obj.IsFunction());
        obj = Function::Cast(obj).ImplicitStaticClosure();
        ASSERT(obj.IsInstance());
        obj = H.Canonicalize(Instance::Cast(obj));
        break;
      case ConstantPoolTag::kType:
        obj = builder_->type_translator_.BuildType().raw();
        ASSERT(obj.IsAbstractType());
        break;
      case ConstantPoolTag::kTypeArguments:
        obj = builder_->type_translator_
                  .BuildTypeArguments(builder_->ReadListLength())
                  .raw();
        ASSERT(obj.IsNull() || obj.IsTypeArguments());
        break;
      case ConstantPoolTag::kList: {
        obj = builder_->type_translator_.BuildType().raw();
        ASSERT(obj.IsAbstractType());
        const intptr_t length = builder_->ReadListLength();
        array = Array::New(length, AbstractType::Cast(obj));
        for (intptr_t j = 0; j < length; j++) {
          intptr_t elem_index = builder_->ReadUInt();
          ASSERT(elem_index < i);
          elem = pool.ObjectAt(elem_index);
          array.SetAt(j, elem);
        }
        obj = H.Canonicalize(Array::Cast(array));
        ASSERT(!obj.IsNull());
      } break;
      case ConstantPoolTag::kInstance: {
        cls =
            H.LookupClassByKernelClass(builder_->ReadCanonicalNameReference());
        obj = Instance::New(cls, Heap::kOld);
        intptr_t type_args_index = builder_->ReadUInt();
        ASSERT(type_args_index < i);
        type_args ^= pool.ObjectAt(type_args_index);
        if (!type_args.IsNull()) {
          Instance::Cast(obj).SetTypeArguments(type_args);
        }
        intptr_t num_fields = builder_->ReadUInt();
        for (intptr_t j = 0; j < num_fields; j++) {
          NameIndex field_name = builder_->ReadCanonicalNameReference();
          ASSERT(H.IsField(field_name));
          field = H.LookupFieldByKernelField(field_name);
          intptr_t elem_index = builder_->ReadUInt();
          ASSERT(elem_index < i);
          elem = pool.ObjectAt(elem_index);
          Instance::Cast(obj).SetField(field, elem);
        }
        obj = H.Canonicalize(Instance::Cast(obj));
      } break;
      case ConstantPoolTag::kSymbol:
        obj = H.DartSymbolPlain(builder_->ReadStringReference()).raw();
        ASSERT(String::Cast(obj).IsSymbol());
        break;
      case ConstantPoolTag::kTypeArgumentsForInstanceAllocation: {
        cls =
            H.LookupClassByKernelClass(builder_->ReadCanonicalNameReference());
        obj =
            builder_->type_translator_
                .BuildInstantiatedTypeArguments(cls, builder_->ReadListLength())
                .raw();
        ASSERT(obj.IsNull() || obj.IsTypeArguments());
      } break;
      case ConstantPoolTag::kContextOffset: {
        intptr_t index = builder_->ReadUInt();
        if (i == 0) {
          obj = Smi::New(Context::parent_offset() / kWordSize);
        } else {
          obj = Smi::New(Context::variable_offset(index - 1) / kWordSize);
        }
      } break;
      case ConstantPoolTag::kClosureFunction: {
        name = H.DartSymbolPlain(builder_->ReadStringReference()).raw();
        const Function& closure = Function::Handle(
            builder_->zone_,
            Function::NewClosureFunction(name, inner_function,
                                         TokenPosition::kNoSource));

        FunctionNodeHelper function_node_helper(builder_);
        function_node_helper.ReadUntilExcluding(
            FunctionNodeHelper::kTypeParameters);
        builder_->LoadAndSetupTypeParameters(builder_->active_class(), closure,
                                             builder_->ReadListLength(),
                                             closure);
        function_node_helper.SetJustRead(FunctionNodeHelper::kTypeParameters);

        // Scope remains opened until ConstantPoolTag::kEndClosureFunctionScope.
        ActiveTypeParametersScope scope(
            builder_->active_class(), &closure,
            TypeArguments::Handle(builder_->zone_, closure.type_parameters()),
            builder_->zone_);

        function_node_helper.ReadUntilExcluding(
            FunctionNodeHelper::kPositionalParameters);

        intptr_t required_parameter_count =
            function_node_helper.required_parameter_count_;
        intptr_t total_parameter_count =
            function_node_helper.total_parameter_count_;

        intptr_t positional_parameter_count = builder_->ReadListLength();

        intptr_t named_parameter_count =
            total_parameter_count - positional_parameter_count;

        const intptr_t extra_parameters = 1;
        closure.set_num_fixed_parameters(extra_parameters +
                                         required_parameter_count);
        if (named_parameter_count > 0) {
          closure.SetNumOptionalParameters(named_parameter_count, false);
        } else {
          closure.SetNumOptionalParameters(
              positional_parameter_count - required_parameter_count, true);
        }
        intptr_t parameter_count = extra_parameters + total_parameter_count;
        closure.set_parameter_types(Array::Handle(
            builder_->zone_, Array::New(parameter_count, Heap::kOld)));
        closure.set_parameter_names(Array::Handle(
            builder_->zone_, Array::New(parameter_count, Heap::kOld)));

        intptr_t pos = 0;
        closure.SetParameterTypeAt(pos, AbstractType::dynamic_type());
        closure.SetParameterNameAt(pos, Symbols::ClosureParameter());
        pos++;

        const Library& lib = Library::Handle(
            builder_->zone_, builder_->active_class()->klass->library());
        for (intptr_t j = 0; j < positional_parameter_count; ++j, ++pos) {
          VariableDeclarationHelper helper(builder_);
          helper.ReadUntilExcluding(VariableDeclarationHelper::kType);
          const AbstractType& type =
              builder_->type_translator_.BuildVariableType();
          Tag tag = builder_->ReadTag();  // read (first part of) initializer.
          if (tag == kSomething) {
            builder_->SkipExpression();  // read (actual) initializer.
          }

          closure.SetParameterTypeAt(pos, type);
          closure.SetParameterNameAt(pos,
                                     H.DartIdentifier(lib, helper.name_index_));
        }

        intptr_t named_parameter_count_check = builder_->ReadListLength();
        ASSERT(named_parameter_count_check == named_parameter_count);
        for (intptr_t j = 0; j < named_parameter_count; ++j, ++pos) {
          VariableDeclarationHelper helper(builder_);
          helper.ReadUntilExcluding(VariableDeclarationHelper::kType);
          const AbstractType& type =
              builder_->type_translator_.BuildVariableType();
          Tag tag = builder_->ReadTag();  // read (first part of) initializer.
          if (tag == kSomething) {
            builder_->SkipExpression();  // read (actual) initializer.
          }

          closure.SetParameterTypeAt(pos, type);
          closure.SetParameterNameAt(pos,
                                     H.DartIdentifier(lib, helper.name_index_));
        }

        function_node_helper.SetJustRead(FunctionNodeHelper::kNamedParameters);

        const AbstractType& return_type =
            builder_->type_translator_.BuildVariableType();
        closure.set_result_type(return_type);
        function_node_helper.SetJustRead(FunctionNodeHelper::kReturnType);
        // The closure has no body.
        function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kEnd);

        pool.SetTypeAt(i, ObjectPool::kTaggedObject);
        pool.SetObjectAt(i, closure);

        // Continue reading the constant pool entries inside the opened
        // ActiveTypeParametersScope until the scope gets closed by a
        // kEndClosureFunctionScope tag, in which case control returns here.
        i = ReadPoolEntries(function, closure, pool, i + 1);
        // Pool entry at index i has been set to null, because it was a
        // kEndClosureFunctionScope.
        ASSERT(pool.ObjectAt(i) == Object::null());
        continue;
      }
      case ConstantPoolTag::kEndClosureFunctionScope: {
        // Entry is not used and set to null.
        obj = Object::null();
        pool.SetTypeAt(i, ObjectPool::kTaggedObject);
        pool.SetObjectAt(i, obj);
        return i;  // The caller will close the scope.
      } break;
      case ConstantPoolTag::kNativeEntry: {
        name = H.DartString(builder_->ReadStringReference()).raw();
        obj = NativeEntry(function, name);
      } break;
      case ConstantPoolTag::kSubtypeTestCache: {
        obj = SubtypeTestCache::New();
      } break;
      default:
        UNREACHABLE();
    }
    pool.SetTypeAt(i, ObjectPool::kTaggedObject);
    pool.SetObjectAt(i, obj);
  }
  // Return the index of the last read pool entry.
  return obj_count - 1;
}

RawCode* BytecodeMetadataHelper::ReadBytecode(const ObjectPool& pool) {
  // TODO(regis): Avoid copying bytecode from mapped kernel binary.
  intptr_t size = builder_->reader_.ReadUInt();
  intptr_t offset = builder_->reader_.offset();
  uint8_t* data =
      builder_->reader_.CopyDataIntoZone(builder_->zone_, offset, size);
  builder_->reader_.set_offset(offset + size);

  // Create and return code object.
  return Code::FinalizeBytecode(reinterpret_cast<void*>(data), size, pool);
}

void BytecodeMetadataHelper::ReadExceptionsTable(const Code& bytecode) {
  const intptr_t try_block_count = builder_->reader_.ReadListLength();
  if (try_block_count > 0) {
    const ObjectPool& pool =
        ObjectPool::Handle(builder_->zone_, bytecode.object_pool());
    AbstractType& handler_type = AbstractType::Handle(builder_->zone_);
    Array& handler_types = Array::Handle(builder_->zone_);
    DescriptorList* pc_descriptors_list =
        new (builder_->zone_) DescriptorList(64);
    ExceptionHandlerList* exception_handlers_list =
        new (builder_->zone_) ExceptionHandlerList();

    // Encoding of ExceptionsTable is described in
    // pkg/vm/lib/bytecode/exceptions.dart.
    for (intptr_t try_index = 0; try_index < try_block_count; try_index++) {
      intptr_t outer_try_index_plus1 = builder_->reader_.ReadUInt();
      intptr_t outer_try_index = outer_try_index_plus1 - 1;
      intptr_t start_pc = builder_->reader_.ReadUInt();
      intptr_t end_pc = builder_->reader_.ReadUInt();
      intptr_t handler_pc = builder_->reader_.ReadUInt();
      uint8_t flags = builder_->reader_.ReadByte();
      const uint8_t kFlagNeedsStackTrace = 1 << 0;
      const uint8_t kFlagIsSynthetic = 1 << 1;
      const bool needs_stacktrace = (flags & kFlagNeedsStackTrace) != 0;
      const bool is_generated = (flags & kFlagIsSynthetic) != 0;
      intptr_t type_count = builder_->reader_.ReadListLength();
      ASSERT(type_count > 0);
      handler_types = Array::New(type_count, Heap::kOld);
      for (intptr_t i = 0; i < type_count; i++) {
        intptr_t type_index = builder_->reader_.ReadUInt();
        ASSERT(type_index < pool.Length());
        handler_type ^= pool.ObjectAt(type_index);
        handler_types.SetAt(i, handler_type);
      }
      pc_descriptors_list->AddDescriptor(RawPcDescriptors::kOther, start_pc,
                                         Thread::kNoDeoptId,
                                         TokenPosition::kNoSource, try_index);
      pc_descriptors_list->AddDescriptor(RawPcDescriptors::kOther, end_pc,
                                         Thread::kNoDeoptId,
                                         TokenPosition::kNoSource, -1);

      exception_handlers_list->AddHandler(
          try_index, outer_try_index, handler_pc, TokenPosition::kNoSource,
          is_generated, handler_types, needs_stacktrace);
    }
    const PcDescriptors& descriptors = PcDescriptors::Handle(
        builder_->zone_,
        pc_descriptors_list->FinalizePcDescriptors(bytecode.PayloadStart()));
    bytecode.set_pc_descriptors(descriptors);
    const ExceptionHandlers& handlers = ExceptionHandlers::Handle(
        builder_->zone_, exception_handlers_list->FinalizeExceptionHandlers(
                             bytecode.PayloadStart()));
    bytecode.set_exception_handlers(handlers);
  } else {
    bytecode.set_pc_descriptors(Object::empty_descriptors());
    bytecode.set_exception_handlers(Object::empty_exception_handlers());
  }
}

RawTypedData* BytecodeMetadataHelper::NativeEntry(const Function& function,
                                                  const String& external_name) {
  Zone* zone = builder_->zone_;
  MethodRecognizer::Kind kind = MethodRecognizer::RecognizeKind(function);
  // This list of recognized methods must be kept in sync with the list of
  // methods handled specially by the NativeCall bytecode in the interpreter.
  switch (kind) {
    case MethodRecognizer::kObjectEquals:
    case MethodRecognizer::kStringBaseLength:
    case MethodRecognizer::kStringBaseIsEmpty:
    case MethodRecognizer::kGrowableArrayLength:
    case MethodRecognizer::kObjectArrayLength:
    case MethodRecognizer::kImmutableArrayLength:
    case MethodRecognizer::kTypedDataLength:
    case MethodRecognizer::kClassIDgetID:
    case MethodRecognizer::kGrowableArrayCapacity:
    case MethodRecognizer::kListFactory:
    case MethodRecognizer::kObjectArrayAllocate:
    case MethodRecognizer::kLinkedHashMap_getIndex:
    case MethodRecognizer::kLinkedHashMap_setIndex:
    case MethodRecognizer::kLinkedHashMap_getData:
    case MethodRecognizer::kLinkedHashMap_setData:
    case MethodRecognizer::kLinkedHashMap_getHashMask:
    case MethodRecognizer::kLinkedHashMap_setHashMask:
    case MethodRecognizer::kLinkedHashMap_getUsedData:
    case MethodRecognizer::kLinkedHashMap_setUsedData:
    case MethodRecognizer::kLinkedHashMap_getDeletedKeys:
    case MethodRecognizer::kLinkedHashMap_setDeletedKeys:
      break;
    default:
      kind = MethodRecognizer::kUnknown;
  }
  NativeFunctionWrapper trampoline = NULL;
  NativeFunction native_function = NULL;
  intptr_t argc_tag = 0;
  if (kind == MethodRecognizer::kUnknown) {
    if (FLAG_link_natives_lazily) {
      trampoline = &NativeEntry::BootstrapNativeCallWrapper;
      native_function =
          reinterpret_cast<NativeFunction>(&NativeEntry::LinkNativeCall);
    } else {
      const Class& cls = Class::Handle(zone, function.Owner());
      const Library& library = Library::Handle(zone, cls.library());
      Dart_NativeEntryResolver resolver = library.native_entry_resolver();
      const bool is_bootstrap_native = Bootstrap::IsBootstrapResolver(resolver);
      const int num_params =
          NativeArguments::ParameterCountForResolution(function);
      bool is_auto_scope = true;
      native_function = NativeEntry::ResolveNative(library, external_name,
                                                   num_params, &is_auto_scope);
      ASSERT(native_function != NULL);  // TODO(regis): Should we throw instead?
      if (is_bootstrap_native) {
        trampoline = &NativeEntry::BootstrapNativeCallWrapper;
      } else if (is_auto_scope) {
        trampoline = &NativeEntry::AutoScopeNativeCallWrapper;
      } else {
        trampoline = &NativeEntry::NoScopeNativeCallWrapper;
      }
    }
    argc_tag = NativeArguments::ComputeArgcTag(function);
  }
  // TODO(regis): Introduce a new VM class subclassing Object and containing
  // these four untagged values.
#ifdef ARCH_IS_32_BIT
  const TypedData& native_entry = TypedData::Handle(
      zone, TypedData::New(kTypedDataUint32ArrayCid, 4, Heap::kOld));
  native_entry.SetUint32(0 << 2, static_cast<uint32_t>(kind));
  native_entry.SetUint32(1 << 2, reinterpret_cast<uint32_t>(trampoline));
  native_entry.SetUint32(2 << 2, reinterpret_cast<uint32_t>(native_function));
  native_entry.SetUint32(3 << 2, static_cast<uint32_t>(argc_tag));
#else
  const TypedData& native_entry = TypedData::Handle(
      zone, TypedData::New(kTypedDataUint64ArrayCid, 4, Heap::kOld));
  native_entry.SetUint64(0 << 3, static_cast<uint64_t>(kind));
  native_entry.SetUint64(1 << 3, reinterpret_cast<uint64_t>(trampoline));
  native_entry.SetUint64(2 << 3, reinterpret_cast<uint64_t>(native_function));
  native_entry.SetUint64(3 << 3, static_cast<uint64_t>(argc_tag));
#endif
  return native_entry.raw();
}
#endif  // defined(DART_USE_INTERPRETER)

StreamingScopeBuilder::StreamingScopeBuilder(ParsedFunction* parsed_function)
    : result_(NULL),
      parsed_function_(parsed_function),
      translation_helper_(Thread::Current()),
      zone_(translation_helper_.zone()),
      current_function_scope_(NULL),
      scope_(NULL),
      depth_(0),
      name_index_(0),
      needs_expr_temp_(false),
      builder_(new StreamingFlowGraphBuilder(
          &translation_helper_,
          Script::Handle(Z, parsed_function->function().script()),
          zone_,
          TypedData::Handle(Z, parsed_function->function().KernelData()),
          parsed_function->function().KernelDataProgramOffset(),
          &active_class_)),
      type_translator_(builder_, /*finalize=*/true) {
  H.InitFromScript(builder_->script());
  ASSERT(type_translator_.active_class_ == &active_class_);
  ASSERT(builder_->type_translator_.active_class_ == &active_class_);
}

StreamingScopeBuilder::~StreamingScopeBuilder() {
  delete builder_;
}

ScopeBuildingResult* StreamingScopeBuilder::BuildScopes() {
  if (result_ != NULL) return result_;

  ASSERT(scope_ == NULL && depth_.loop_ == 0 && depth_.function_ == 0);
  result_ = new (Z) ScopeBuildingResult();

  const Function& function = parsed_function_->function();

  // Setup a [ActiveClassScope] and a [ActiveMemberScope] which will be used
  // e.g. for type translation.
  const Class& klass = Class::Handle(zone_, function.Owner());

  Function& outermost_function = Function::Handle(Z);
  builder_->DiscoverEnclosingElements(Z, function, &outermost_function);

  ActiveClassScope active_class_scope(&active_class_, &klass);
  ActiveMemberScope active_member(&active_class_, &outermost_function);
  ActiveTypeParametersScope active_type_params(&active_class_, function, Z);

  LocalScope* enclosing_scope = NULL;
  if (function.IsImplicitClosureFunction() && !function.is_static()) {
    // Create artificial enclosing scope for the tear-off that contains
    // captured receiver value. This ensure that AssertAssignable will correctly
    // load instantiator type arguments if they are needed.
    Class& klass = Class::Handle(Z, function.Owner());
    Type& klass_type = H.GetCanonicalType(klass);
    result_->this_variable =
        MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                     Symbols::This(), klass_type);
    result_->this_variable->set_index(VariableIndex(0));
    result_->this_variable->set_is_captured();
    enclosing_scope = new (Z) LocalScope(NULL, 0, 0);
    enclosing_scope->set_context_level(0);
    enclosing_scope->AddVariable(result_->this_variable);
  } else if (function.IsLocalFunction()) {
    enclosing_scope = LocalScope::RestoreOuterScope(
        ContextScope::Handle(Z, function.context_scope()));
  }
  current_function_scope_ = scope_ = new (Z) LocalScope(enclosing_scope, 0, 0);
  scope_->set_begin_token_pos(function.token_pos());
  scope_->set_end_token_pos(function.end_token_pos());

  // Add function type arguments variable before current context variable.
  if (I->reify_generic_functions() &&
      (function.IsGeneric() || function.HasGenericParent())) {
    LocalVariable* type_args_var = MakeVariable(
        TokenPosition::kNoSource, TokenPosition::kNoSource,
        Symbols::FunctionTypeArgumentsVar(), AbstractType::dynamic_type());
    scope_->AddVariable(type_args_var);
    parsed_function_->set_function_type_arguments(type_args_var);
  }

  if (parsed_function_->has_arg_desc_var()) {
    needs_expr_temp_ = true;
    scope_->AddVariable(parsed_function_->arg_desc_var());
  }

  LocalVariable* context_var = parsed_function_->current_context_var();
  context_var->set_is_forced_stack();
  scope_->AddVariable(context_var);

  parsed_function_->SetNodeSequence(
      new SequenceNode(TokenPosition::kNoSource, scope_));

  builder_->SetOffset(function.kernel_offset());

  FunctionNodeHelper function_node_helper(builder_);
  const ProcedureAttributesMetadata attrs =
      builder_->procedure_attributes_metadata_helper_.GetProcedureAttributes(
          function.kernel_offset());

  switch (function.kind()) {
    case RawFunction::kClosureFunction:
    case RawFunction::kImplicitClosureFunction:
    case RawFunction::kRegularFunction:
    case RawFunction::kGetterFunction:
    case RawFunction::kSetterFunction:
    case RawFunction::kConstructor: {
      const Tag tag = builder_->PeekTag();
      builder_->ReadUntilFunctionNode();
      function_node_helper.ReadUntilExcluding(
          FunctionNodeHelper::kPositionalParameters);
      current_function_async_marker_ = function_node_helper.async_marker_;
      // NOTE: FunctionNode is read further below the if.

      intptr_t pos = 0;
      if (function.IsClosureFunction()) {
        LocalVariable* closure_parameter = MakeVariable(
            TokenPosition::kNoSource, TokenPosition::kNoSource,
            Symbols::ClosureParameter(), AbstractType::dynamic_type());
        closure_parameter->set_is_forced_stack();
        scope_->InsertParameterAt(pos++, closure_parameter);
      } else if (!function.is_static()) {
        // We use [is_static] instead of [IsStaticFunction] because the latter
        // returns `false` for constructors.
        Class& klass = Class::Handle(Z, function.Owner());
        Type& klass_type = H.GetCanonicalType(klass);
        LocalVariable* variable =
            MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                         Symbols::This(), klass_type);
        scope_->InsertParameterAt(pos++, variable);
        result_->this_variable = variable;

        // We visit instance field initializers because they might contain
        // [Let] expressions and we need to have a mapping.
        if (tag == kConstructor) {
          Class& parent_class = Class::Handle(Z, function.Owner());
          Array& class_fields = Array::Handle(Z, parent_class.fields());
          Field& class_field = Field::Handle(Z);
          for (intptr_t i = 0; i < class_fields.Length(); ++i) {
            class_field ^= class_fields.At(i);
            if (!class_field.is_static()) {
              TypedData& kernel_data =
                  TypedData::Handle(Z, class_field.KernelData());
              ASSERT(!kernel_data.IsNull());
              intptr_t field_offset = class_field.kernel_offset();
              AlternativeReadingScope alt(&builder_->reader_, &kernel_data,
                                          field_offset);
              FieldHelper field_helper(builder_);
              field_helper.ReadUntilExcluding(FieldHelper::kInitializer);
              Tag initializer_tag =
                  builder_->ReadTag();  // read first part of initializer.
              if (initializer_tag == kSomething) {
                EnterScope(field_offset);
                VisitExpression();  // read initializer.
                ExitScope(field_helper.position_, field_helper.end_position_);
              }
            }
          }
        }
      } else if (function.IsFactory()) {
        LocalVariable* variable = MakeVariable(
            TokenPosition::kNoSource, TokenPosition::kNoSource,
            Symbols::TypeArgumentsParameter(), AbstractType::dynamic_type());
        scope_->InsertParameterAt(pos++, variable);
        result_->type_arguments_variable = variable;
      }

      ParameterTypeCheckMode type_check_mode = kTypeCheckAllParameters;
      if (function.IsNonImplicitClosureFunction()) {
        type_check_mode = kTypeCheckAllParameters;
      } else if (function.IsImplicitClosureFunction()) {
        if (!attrs.has_dynamic_invocations) {
          // This is a tear-off of an instance method that can not be reached
          // from any dynamic invocation. The method would not check any
          // parameters except covariant ones and those annotated with
          // generic-covariant-impl. Which means that we have to check
          // the rest in the tear-off itself..
          type_check_mode = kTypeCheckForTearOffOfNonDynamicallyInvokedMethod;
        }
      } else {
        if (function.is_static()) {
          // In static functions we don't check anything.
          type_check_mode = kTypeCheckForStaticFunction;
        } else if (!attrs.has_dynamic_invocations) {
          // If the current function is never a target of a dynamic invocation
          // and this parameter is not marked with generic-covariant-impl
          // (which means that among all super-interfaces no type parameters
          // ever occur at the position of this parameter) then we don't need
          // to check this parameter on the callee side, because strong mode
          // guarantees that it was checked at the caller side.
          type_check_mode = kTypeCheckForNonDynamicallyInvokedMethod;
        }
      }

      // Continue reading FunctionNode:
      // read positional_parameters and named_parameters.
      AddPositionalAndNamedParameters(pos, type_check_mode, attrs);

      // We generate a synthetic body for implicit closure functions - which
      // will forward the call to the real function.
      //     -> see BuildGraphOfImplicitClosureFunction
      if (!function.IsImplicitClosureFunction()) {
        builder_->SetOffset(function.kernel_offset());
        first_body_token_position_ = TokenPosition::kNoSource;
        VisitNode();

        // TODO(jensj): HACK: Push the begin token to after any parameters to
        // avoid crash when breaking on definition line of async method in
        // debugger. It seems that another scope needs to be added
        // in which captures are made, but I can't make that work.
        // This 'solution' doesn't crash, but I cannot see the parameters at
        // that particular breakpoint either.
        // Also push the end token to after the "}" to avoid crashing on
        // stepping past the last line (to the "}" character).
        if (first_body_token_position_.IsReal()) {
          scope_->set_begin_token_pos(first_body_token_position_);
        }
        if (scope_->end_token_pos().IsReal()) {
          scope_->set_end_token_pos(scope_->end_token_pos().Next());
        }
      }
      break;
    }
    case RawFunction::kImplicitGetter:
    case RawFunction::kImplicitStaticFinalGetter:
    case RawFunction::kImplicitSetter: {
      ASSERT(builder_->PeekTag() == kField);
      if (IsFieldInitializer(function, Z)) {
        VisitNode();
        break;
      }
      const bool is_setter = function.IsImplicitSetterFunction();
      const bool is_method = !function.IsStaticFunction();
      intptr_t pos = 0;
      if (is_method) {
        Class& klass = Class::Handle(Z, function.Owner());
        Type& klass_type = H.GetCanonicalType(klass);
        LocalVariable* variable =
            MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                         Symbols::This(), klass_type);
        scope_->InsertParameterAt(pos++, variable);
        result_->this_variable = variable;
      }
      if (is_setter) {
        result_->setter_value = MakeVariable(
            TokenPosition::kNoSource, TokenPosition::kNoSource,
            Symbols::Value(),
            AbstractType::ZoneHandle(Z, function.ParameterTypeAt(pos)));
        scope_->InsertParameterAt(pos++, result_->setter_value);

        if (is_method && !attrs.has_dynamic_invocations) {
          FieldHelper field_helper(builder_);
          field_helper.ReadUntilIncluding(FieldHelper::kFlags);

          if (!field_helper.IsCovariant() &&
              (!field_helper.IsGenericCovariantImpl() ||
               (!attrs.has_non_this_uses && !attrs.has_tearoff_uses))) {
            result_->setter_value->set_type_check_mode(
                LocalVariable::kTypeCheckedByCaller);
          }
        }
      }
      break;
    }
    case RawFunction::kMethodExtractor: {
      // Add a receiver parameter.  Though it is captured, we emit code to
      // explicitly copy it to a fixed offset in a freshly-allocated context
      // instead of using the generic code for regular functions.
      // Therefore, it isn't necessary to mark it as captured here.
      Class& klass = Class::Handle(Z, function.Owner());
      Type& klass_type = H.GetCanonicalType(klass);
      LocalVariable* variable =
          MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                       Symbols::This(), klass_type);
      scope_->InsertParameterAt(0, variable);
      result_->this_variable = variable;
      break;
    }
    case RawFunction::kNoSuchMethodDispatcher:
    case RawFunction::kInvokeFieldDispatcher:
      for (intptr_t i = 0; i < function.NumParameters(); ++i) {
        LocalVariable* variable =
            MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                         String::ZoneHandle(Z, function.ParameterNameAt(i)),
                         AbstractType::dynamic_type());
        scope_->InsertParameterAt(i, variable);
      }
      break;
    case RawFunction::kSignatureFunction:
    case RawFunction::kIrregexpFunction:
      UNREACHABLE();
  }
  if (needs_expr_temp_ || function.is_no_such_method_forwarder()) {
    scope_->AddVariable(parsed_function_->EnsureExpressionTemp());
  }
  parsed_function_->AllocateVariables();

  return result_;
}

void StreamingScopeBuilder::ReportUnexpectedTag(const char* variant, Tag tag) {
  H.ReportError(builder_->script(), TokenPosition::kNoSource,
                "Unexpected tag %d (%s) in %s, expected %s", tag,
                Reader::TagName(tag),
                parsed_function_->function().ToQualifiedCString(), variant);
}

void StreamingScopeBuilder::VisitNode() {
  Tag tag = builder_->PeekTag();
  switch (tag) {
    case kConstructor:
      VisitConstructor();
      return;
    case kProcedure:
      VisitProcedure();
      return;
    case kField:
      VisitField();
      return;
    case kFunctionNode:
      VisitFunctionNode();
      return;
    default:
      UNIMPLEMENTED();
      return;
  }
}

void StreamingScopeBuilder::VisitConstructor() {
  // Field initializers that come from non-static field declarations are
  // compiled as if they appear in the constructor initializer list.  This is
  // important for closure-valued field initializers because the VM expects the
  // corresponding closure functions to appear as if they were nested inside the
  // constructor.
  ConstructorHelper constructor_helper(builder_);
  constructor_helper.ReadUntilExcluding(ConstructorHelper::kFunction);
  {
    const Function& function = parsed_function_->function();
    Class& parent_class = Class::Handle(Z, function.Owner());
    Array& class_fields = Array::Handle(Z, parent_class.fields());
    Field& class_field = Field::Handle(Z);
    for (intptr_t i = 0; i < class_fields.Length(); ++i) {
      class_field ^= class_fields.At(i);
      if (!class_field.is_static()) {
        TypedData& kernel_data = TypedData::Handle(Z, class_field.KernelData());
        ASSERT(!kernel_data.IsNull());
        intptr_t field_offset = class_field.kernel_offset();
        AlternativeReadingScope alt(&builder_->reader_, &kernel_data,
                                    field_offset);
        FieldHelper field_helper(builder_);
        field_helper.ReadUntilExcluding(FieldHelper::kInitializer);
        Tag initializer_tag = builder_->ReadTag();
        if (initializer_tag == kSomething) {
          VisitExpression();  // read initializer.
        }
      }
    }
  }

  // Visit children (note that there's no reason to visit the name).
  VisitFunctionNode();
  intptr_t list_length =
      builder_->ReadListLength();  // read initializers list length.
  for (intptr_t i = 0; i < list_length; i++) {
    VisitInitializer();
  }
}

void StreamingScopeBuilder::VisitProcedure() {
  ProcedureHelper procedure_helper(builder_);
  procedure_helper.ReadUntilExcluding(ProcedureHelper::kFunction);
  if (builder_->ReadTag() == kSomething) {
    VisitFunctionNode();
  }
}

void StreamingScopeBuilder::VisitField() {
  FieldHelper field_helper(builder_);
  field_helper.ReadUntilExcluding(FieldHelper::kType);
  VisitDartType();                // read type.
  Tag tag = builder_->ReadTag();  // read initializer (part 1).
  if (tag == kSomething) {
    VisitExpression();  // read initializer (part 2).
  }
}

void StreamingScopeBuilder::VisitFunctionNode() {
  FunctionNodeHelper function_node_helper(builder_);
  function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kTypeParameters);

  intptr_t list_length =
      builder_->ReadListLength();  // read type_parameters list length.
  for (intptr_t i = 0; i < list_length; ++i) {
    TypeParameterHelper helper(builder_);
    helper.ReadUntilExcludingAndSetJustRead(TypeParameterHelper::kBound);
    VisitDartType();                    // read ith bound.
    helper.ReadUntilExcludingAndSetJustRead(TypeParameterHelper::kDefaultType);
    if (builder_->ReadTag() == kSomething) {
      VisitDartType();  // read ith default type.
    }
    helper.Finish();
  }
  function_node_helper.SetJustRead(FunctionNodeHelper::kTypeParameters);

  if (FLAG_causal_async_stacks &&
      (function_node_helper.dart_async_marker_ == FunctionNodeHelper::kAsync ||
       function_node_helper.dart_async_marker_ ==
           FunctionNodeHelper::kAsyncStar)) {
    LocalVariable* asyncStackTraceVar = MakeVariable(
        TokenPosition::kNoSource, TokenPosition::kNoSource,
        Symbols::AsyncStackTraceVar(), AbstractType::dynamic_type());
    scope_->AddVariable(asyncStackTraceVar);
  }

  if (function_node_helper.async_marker_ == FunctionNodeHelper::kSyncYielding) {
    LocalScope* scope = parsed_function_->node_sequence()->scope();
    intptr_t offset = parsed_function_->function().num_fixed_parameters();
    for (intptr_t i = 0;
         i < parsed_function_->function().NumOptionalPositionalParameters();
         i++) {
      scope->VariableAt(offset + i)->set_is_forced_stack();
    }
  }

  // Read (but don't visit) the positional and named parameters, because they've
  // already been added to the scope.
  function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kBody);

  if (builder_->ReadTag() == kSomething) {
    PositionScope scope(&builder_->reader_);
    VisitStatement();  // Read body
    first_body_token_position_ = builder_->reader_.min_position();
  }

  // Ensure that :await_jump_var, :await_ctx_var, :async_op,
  // :async_completer and :async_stack_trace are captured.
  if (function_node_helper.async_marker_ == FunctionNodeHelper::kSyncYielding) {
    {
      LocalVariable* temp = NULL;
      LookupCapturedVariableByName(
          (depth_.function_ == 0) ? &result_->yield_jump_variable : &temp,
          Symbols::AwaitJumpVar());
    }
    {
      LocalVariable* temp = NULL;
      LookupCapturedVariableByName(
          (depth_.function_ == 0) ? &result_->yield_context_variable : &temp,
          Symbols::AwaitContextVar());
    }
    {
      LocalVariable* temp =
          scope_->LookupVariable(Symbols::AsyncOperation(), true);
      if (temp != NULL) {
        scope_->CaptureVariable(temp);
      }
    }
    {
      LocalVariable* temp =
          scope_->LookupVariable(Symbols::AsyncCompleter(), true);
      if (temp != NULL) {
        scope_->CaptureVariable(temp);
      }
    }
    if (FLAG_causal_async_stacks) {
      LocalVariable* temp =
          scope_->LookupVariable(Symbols::AsyncStackTraceVar(), true);
      if (temp != NULL) {
        scope_->CaptureVariable(temp);
      }
    }
  }
}

void StreamingScopeBuilder::VisitInitializer() {
  Tag tag = builder_->ReadTag();
  builder_->ReadByte();  // read isSynthetic flag.
  switch (tag) {
    case kInvalidInitializer:
      return;
    case kFieldInitializer:
      builder_->SkipCanonicalNameReference();  // read field_reference.
      VisitExpression();                       // read value.
      return;
    case kSuperInitializer:
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitArguments();                        // read arguments.
      return;
    case kRedirectingInitializer:
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitArguments();                        // read arguments.
      return;
    case kLocalInitializer:
      VisitVariableDeclaration();  // read variable.
      return;
    case kAssertInitializer:
      VisitStatement();
      return;
    default:
      ReportUnexpectedTag("initializer", tag);
      UNREACHABLE();
  }
}

void StreamingScopeBuilder::VisitExpression() {
  uint8_t payload = 0;
  Tag tag = builder_->ReadTag(&payload);
  switch (tag) {
    case kInvalidExpression:
      builder_->ReadPosition();
      builder_->SkipStringReference();
      return;
    case kVariableGet: {
      builder_->ReadPosition();  // read position.
      intptr_t variable_kernel_offset =
          builder_->ReadUInt();          // read kernel position.
      builder_->ReadUInt();              // read relative variable index.
      builder_->SkipOptionalDartType();  // read promoted type.
      LookupVariable(variable_kernel_offset);
      return;
    }
    case kSpecializedVariableGet: {
      builder_->ReadPosition();  // read position.
      intptr_t variable_kernel_offset =
          builder_->ReadUInt();  // read kernel position.
      LookupVariable(variable_kernel_offset);
      return;
    }
    case kVariableSet: {
      builder_->ReadPosition();  // read position.
      intptr_t variable_kernel_offset =
          builder_->ReadUInt();  // read kernel position.
      builder_->ReadUInt();      // read relative variable index.
      LookupVariable(variable_kernel_offset);
      VisitExpression();  // read expression.
      return;
    }
    case kSpecializedVariableSet: {
      builder_->ReadPosition();  // read position.
      intptr_t variable_kernel_offset =
          builder_->ReadUInt();  // read kernel position.
      LookupVariable(variable_kernel_offset);
      VisitExpression();  // read expression.
      return;
    }
    case kPropertyGet:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read receiver.
      builder_->SkipName();      // read name.
      // read interface_target_reference.
      builder_->SkipCanonicalNameReference();
      return;
    case kPropertySet:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read receiver.
      builder_->SkipName();      // read name.
      VisitExpression();         // read value.
      // read interface_target_reference.
      builder_->SkipCanonicalNameReference();
      return;
    case kDirectPropertyGet:
      builder_->ReadPosition();                // read position.
      VisitExpression();                       // read receiver.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      return;
    case kDirectPropertySet:
      builder_->ReadPosition();                // read position.
      VisitExpression();                       // read receiver.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitExpression();                       // read value·
      return;
    case kSuperPropertyGet:
      HandleSpecialLoad(&result_->this_variable, Symbols::This());
      builder_->ReadPosition();                // read position.
      builder_->SkipName();                    // read name.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      return;
    case kSuperPropertySet:
      HandleSpecialLoad(&result_->this_variable, Symbols::This());
      builder_->ReadPosition();                // read position.
      builder_->SkipName();                    // read name.
      VisitExpression();                       // read value.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      return;
    case kStaticGet:
      builder_->ReadPosition();                // read position.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      return;
    case kStaticSet:
      builder_->ReadPosition();                // read position.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitExpression();                       // read expression.
      return;
    case kMethodInvocation:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read receiver.
      builder_->SkipName();      // read name.
      VisitArguments();          // read arguments.
      // read interface_target_reference.
      builder_->SkipCanonicalNameReference();
      return;
    case kDirectMethodInvocation:
      builder_->ReadPosition();                // read position.
      VisitExpression();                       // read receiver.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitArguments();                        // read arguments.
      return;
    case kSuperMethodInvocation:
      HandleSpecialLoad(&result_->this_variable, Symbols::This());
      builder_->ReadPosition();  // read position.
      builder_->SkipName();      // read name.
      VisitArguments();          // read arguments.
      // read interface_target_reference.
      builder_->SkipCanonicalNameReference();
      return;
    case kStaticInvocation:
    case kConstStaticInvocation:
      builder_->ReadPosition();                // read position.
      builder_->SkipCanonicalNameReference();  // read procedure_reference.
      VisitArguments();                        // read arguments.
      return;
    case kConstructorInvocation:
    case kConstConstructorInvocation:
      builder_->ReadPosition();                // read position.
      builder_->SkipCanonicalNameReference();  // read target_reference.
      VisitArguments();                        // read arguments.
      return;
    case kNot:
      VisitExpression();  // read expression.
      return;
    case kLogicalExpression:
      needs_expr_temp_ = true;
      VisitExpression();       // read left.
      builder_->SkipBytes(1);  // read operator.
      VisitExpression();       // read right.
      return;
    case kConditionalExpression: {
      needs_expr_temp_ = true;
      VisitExpression();                 // read condition.
      VisitExpression();                 // read then.
      VisitExpression();                 // read otherwise.
      builder_->SkipOptionalDartType();  // read unused static type.
      return;
    }
    case kStringConcatenation: {
      builder_->ReadPosition();                           // read position.
      intptr_t list_length = builder_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitExpression();  // read ith expression.
      }
      return;
    }
    case kIsExpression:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read operand.
      VisitDartType();           // read type.
      return;
    case kAsExpression:
      builder_->ReadPosition();  // read position.
      builder_->ReadFlags();     // read flags.
      VisitExpression();         // read operand.
      VisitDartType();           // read type.
      return;
    case kSymbolLiteral:
      builder_->SkipStringReference();  // read index into string table.
      return;
    case kTypeLiteral:
      VisitDartType();  // read type.
      return;
    case kThisExpression:
      HandleSpecialLoad(&result_->this_variable, Symbols::This());
      return;
    case kRethrow:
      builder_->ReadPosition();  // read position.
      return;
    case kThrow:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read expression.
      return;
    case kListLiteral:
    case kConstListLiteral: {
      builder_->ReadPosition();                           // read position.
      VisitDartType();                                    // read type.
      intptr_t list_length = builder_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitExpression();  // read ith expression.
      }
      return;
    }
    case kMapLiteral:
    case kConstMapLiteral: {
      builder_->ReadPosition();                           // read position.
      VisitDartType();                                    // read key type.
      VisitDartType();                                    // read value type.
      intptr_t list_length = builder_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitExpression();  // read ith key.
        VisitExpression();  // read ith value.
      }
      return;
    }
    case kFunctionExpression: {
      intptr_t offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.
      builder_->ReadPosition();          // read position.
      HandleLocalFunction(offset);       // read function node.
      return;
    }
    case kLet: {
      PositionScope scope(&builder_->reader_);
      intptr_t offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.

      EnterScope(offset);

      VisitVariableDeclaration();  // read variable declaration.
      VisitExpression();           // read expression.

      ExitScope(builder_->reader_.min_position(),
                builder_->reader_.max_position());
      return;
    }
    case kBigIntLiteral:
      builder_->SkipStringReference();  // read string reference.
      return;
    case kStringLiteral:
      builder_->SkipStringReference();  // read string reference.
      return;
    case kSpecializedIntLiteral:
      return;
    case kNegativeIntLiteral:
      builder_->ReadUInt();  // read value.
      return;
    case kPositiveIntLiteral:
      builder_->ReadUInt();  // read value.
      return;
    case kDoubleLiteral:
      builder_->ReadDouble();  // read value.
      return;
    case kTrueLiteral:
      return;
    case kFalseLiteral:
      return;
    case kNullLiteral:
      return;
    case kConstantExpression: {
      builder_->SkipConstantReference();
      return;
    }
    case kInstantiation: {
      VisitExpression();
      const intptr_t list_length =
          builder_->ReadListLength();  // read list length.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitDartType();  // read ith type.
      }
      return;
    }
    case kLoadLibrary:
    case kCheckLibraryIsLoaded:
      builder_->ReadUInt();  // library index
      break;
    default:
      ReportUnexpectedTag("expression", tag);
      UNREACHABLE();
  }
}

void StreamingScopeBuilder::VisitStatement() {
  Tag tag = builder_->ReadTag();  // read tag.
  switch (tag) {
    case kExpressionStatement:
      VisitExpression();  // read expression.
      return;
    case kBlock: {
      PositionScope scope(&builder_->reader_);
      intptr_t offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.

      EnterScope(offset);

      intptr_t list_length =
          builder_->ReadListLength();  // read number of statements.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitStatement();  // read ith statement.
      }

      ExitScope(builder_->reader_.min_position(),
                builder_->reader_.max_position());
      return;
    }
    case kEmptyStatement:
      return;
    case kAssertBlock:
      if (I->asserts()) {
        PositionScope scope(&builder_->reader_);
        intptr_t offset =
            builder_->ReaderOffset() - 1;  // -1 to include tag byte.

        EnterScope(offset);

        intptr_t list_length =
            builder_->ReadListLength();  // read number of statements.
        for (intptr_t i = 0; i < list_length; ++i) {
          VisitStatement();  // read ith statement.
        }

        ExitScope(builder_->reader_.min_position(),
                  builder_->reader_.max_position());
      } else {
        builder_->SkipStatementList();
      }
      return;
    case kAssertStatement:
      if (I->asserts()) {
        VisitExpression();              // Read condition.
        builder_->ReadPosition();       // read condition start offset.
        builder_->ReadPosition();       // read condition end offset.
        Tag tag = builder_->ReadTag();  // read (first part of) message.
        if (tag == kSomething) {
          VisitExpression();  // read (rest of) message.
        }
      } else {
        builder_->SkipExpression();     // Read condition.
        builder_->ReadPosition();       // read condition start offset.
        builder_->ReadPosition();       // read condition end offset.
        Tag tag = builder_->ReadTag();  // read (first part of) message.
        if (tag == kSomething) {
          builder_->SkipExpression();  // read (rest of) message.
        }
      }
      return;
    case kLabeledStatement:
      VisitStatement();  // read body.
      return;
    case kBreakStatement:
      builder_->ReadPosition();  // read position.
      builder_->ReadUInt();      // read target_index.
      return;
    case kWhileStatement:
      ++depth_.loop_;
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read condition.
      VisitStatement();          // read body.
      --depth_.loop_;
      return;
    case kDoStatement:
      ++depth_.loop_;
      builder_->ReadPosition();  // read position.
      VisitStatement();          // read body.
      VisitExpression();         // read condition.
      --depth_.loop_;
      return;
    case kForStatement: {
      PositionScope scope(&builder_->reader_);

      intptr_t offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.

      ++depth_.loop_;
      EnterScope(offset);

      TokenPosition position = builder_->ReadPosition();  // read position.
      intptr_t list_length =
          builder_->ReadListLength();  // read number of variables.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitVariableDeclaration();  // read ith variable.
      }

      Tag tag = builder_->ReadTag();  // Read first part of condition.
      if (tag == kSomething) {
        VisitExpression();  // read rest of condition.
      }
      list_length = builder_->ReadListLength();  // read number of updates.
      for (intptr_t i = 0; i < list_length; ++i) {
        VisitExpression();  // read ith update.
      }
      VisitStatement();  // read body.

      ExitScope(position, builder_->reader_.max_position());
      --depth_.loop_;
      return;
    }
    case kForInStatement:
    case kAsyncForInStatement: {
      PositionScope scope(&builder_->reader_);

      intptr_t start_offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.

      builder_->ReadPosition();  // read position.
      TokenPosition body_position =
          builder_->ReadPosition();  // read body position.

      // Notice the ordering: We skip the variable, read the iterable, go back,
      // re-read the variable, go forward to after having read the iterable.
      intptr_t offset = builder_->ReaderOffset();
      builder_->SkipVariableDeclaration();  // read variable.
      VisitExpression();                    // read iterable.

      ++depth_.for_in_;
      AddIteratorVariable();
      ++depth_.loop_;
      EnterScope(start_offset);

      {
        AlternativeReadingScope alt(&builder_->reader_, offset);
        VisitVariableDeclaration();  // read variable.
      }
      VisitStatement();  // read body.

      if (!body_position.IsReal()) {
        body_position = builder_->reader_.min_position();
      }
      // TODO(jensj): From kernel_binary.cc
      // forinstmt->variable_->set_end_position(forinstmt->position_);
      ExitScope(body_position, builder_->reader_.max_position());
      --depth_.loop_;
      --depth_.for_in_;
      return;
    }
    case kSwitchStatement: {
      AddSwitchVariable();
      builder_->ReadPosition();                     // read position.
      VisitExpression();                            // read condition.
      int case_count = builder_->ReadListLength();  // read number of cases.
      for (intptr_t i = 0; i < case_count; ++i) {
        int expression_count =
            builder_->ReadListLength();  // read number of expressions.
        for (intptr_t j = 0; j < expression_count; ++j) {
          builder_->ReadPosition();  // read jth position.
          VisitExpression();         // read jth expression.
        }
        builder_->ReadBool();  // read is_default.
        VisitStatement();      // read body.
      }
      return;
    }
    case kContinueSwitchStatement:
      builder_->ReadPosition();  // read position.
      builder_->ReadUInt();      // read target_index.
      return;
    case kIfStatement:
      builder_->ReadPosition();  // read position.
      VisitExpression();         // read condition.
      VisitStatement();          // read then.
      VisitStatement();          // read otherwise.
      return;
    case kReturnStatement: {
      if ((depth_.function_ == 0) && (depth_.finally_ > 0) &&
          (result_->finally_return_variable == NULL)) {
        const String& name = Symbols::TryFinallyReturnValue();
        LocalVariable* variable =
            MakeVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                         name, AbstractType::dynamic_type());
        current_function_scope_->AddVariable(variable);
        result_->finally_return_variable = variable;
      }

      builder_->ReadPosition();       // read position
      Tag tag = builder_->ReadTag();  // read (first part of) expression.
      if (tag == kSomething) {
        VisitExpression();  // read (rest of) expression.
      }
      return;
    }
    case kTryCatch: {
      ++depth_.try_;
      AddTryVariables();
      VisitStatement();  // read body.
      --depth_.try_;

      ++depth_.catch_;
      AddCatchVariables();

      builder_->ReadByte();  // read flags
      intptr_t catch_count =
          builder_->ReadListLength();  // read number of catches.
      for (intptr_t i = 0; i < catch_count; ++i) {
        PositionScope scope(&builder_->reader_);
        intptr_t offset = builder_->ReaderOffset();  // Catch has no tag.

        EnterScope(offset);

        builder_->ReadPosition();   // read position.
        VisitDartType();            // Read the guard.
        tag = builder_->ReadTag();  // read first part of exception.
        if (tag == kSomething) {
          VisitVariableDeclaration();  // read exception.
        }
        tag = builder_->ReadTag();  // read first part of stack trace.
        if (tag == kSomething) {
          VisitVariableDeclaration();  // read stack trace.
        }
        VisitStatement();  // read body.

        ExitScope(builder_->reader_.min_position(),
                  builder_->reader_.max_position());
      }

      FinalizeCatchVariables();

      --depth_.catch_;
      return;
    }
    case kTryFinally: {
      ++depth_.try_;
      ++depth_.finally_;
      AddTryVariables();

      VisitStatement();  // read body.

      --depth_.finally_;
      --depth_.try_;
      ++depth_.catch_;
      AddCatchVariables();

      VisitStatement();  // read finalizer.

      FinalizeCatchVariables();

      --depth_.catch_;
      return;
    }
    case kYieldStatement: {
      builder_->ReadPosition();           // read position.
      word flags = builder_->ReadByte();  // read flags.
      VisitExpression();                  // read expression.

      ASSERT(flags == kNativeYieldFlags);
      if (depth_.function_ == 0) {
        AddSwitchVariable();
        // Promote all currently visible local variables into the context.
        // TODO(27590) CaptureLocalVariables promotes to many variables into
        // the scope. Mark those variables as stack_local.
        // TODO(27590) we don't need to promote those variables that are
        // not used across yields.
        scope_->CaptureLocalVariables(current_function_scope_);
      }
      return;
    }
    case kVariableDeclaration:
      VisitVariableDeclaration();  // read variable declaration.
      return;
    case kFunctionDeclaration: {
      intptr_t offset =
          builder_->ReaderOffset() - 1;  // -1 to include tag byte.
      builder_->ReadPosition();          // read position.
      VisitVariableDeclaration();        // read variable declaration.
      HandleLocalFunction(offset);       // read function node.
      return;
    }
    default:
      ReportUnexpectedTag("declaration", tag);
      UNREACHABLE();
  }
}

void StreamingScopeBuilder::VisitArguments() {
  builder_->ReadUInt();  // read argument_count.

  // Types
  intptr_t list_length = builder_->ReadListLength();  // read list length.
  for (intptr_t i = 0; i < list_length; ++i) {
    VisitDartType();  // read ith type.
  }

  // Positional.
  list_length = builder_->ReadListLength();  // read list length.
  for (intptr_t i = 0; i < list_length; ++i) {
    VisitExpression();  // read ith positional.
  }

  // Named.
  list_length = builder_->ReadListLength();  // read list length.
  for (intptr_t i = 0; i < list_length; ++i) {
    builder_->SkipStringReference();  // read ith name index.
    VisitExpression();                // read ith expression.
  }
}

void StreamingScopeBuilder::VisitVariableDeclaration() {
  PositionScope scope(&builder_->reader_);

  intptr_t kernel_offset_no_tag = builder_->ReaderOffset();
  VariableDeclarationHelper helper(builder_);
  helper.ReadUntilExcluding(VariableDeclarationHelper::kType);
  AbstractType& type = BuildAndVisitVariableType();

  // In case `declaration->IsConst()` the flow graph building will take care of
  // evaluating the constant and setting it via
  // `declaration->SetConstantValue()`.
  const String& name = (H.StringSize(helper.name_index_) == 0)
                           ? GenerateName(":var", name_index_++)
                           : H.DartSymbolObfuscate(helper.name_index_);

  Tag tag = builder_->ReadTag();  // read (first part of) initializer.
  if (tag == kSomething) {
    VisitExpression();  // read (actual) initializer.
  }

  // Go to next token position so it ends *after* the last potentially
  // debuggable position in the initializer.
  TokenPosition end_position = builder_->reader_.max_position();
  if (end_position.IsReal()) {
    end_position.Next();
  }
  LocalVariable* variable =
      MakeVariable(helper.position_, end_position, name, type);
  if (helper.IsFinal()) {
    variable->set_is_final();
  }
  scope_->AddVariable(variable);
  result_->locals.Insert(builder_->data_program_offset_ + kernel_offset_no_tag,
                         variable);
}

AbstractType& StreamingScopeBuilder::BuildAndVisitVariableType() {
  const intptr_t offset = builder_->ReaderOffset();
  AbstractType& type = T.BuildVariableType();
  builder_->SetOffset(offset);  // rewind
  VisitDartType();
  return type;
}

void StreamingScopeBuilder::VisitDartType() {
  Tag tag = builder_->ReadTag();
  switch (tag) {
    case kInvalidType:
    case kDynamicType:
    case kVoidType:
    case kBottomType:
      // those contain nothing.
      return;
    case kInterfaceType:
      VisitInterfaceType(false);
      return;
    case kSimpleInterfaceType:
      VisitInterfaceType(true);
      return;
    case kFunctionType:
      VisitFunctionType(false);
      return;
    case kSimpleFunctionType:
      VisitFunctionType(true);
      return;
    case kTypeParameterType:
      VisitTypeParameterType();
      return;
    default:
      ReportUnexpectedTag("type", tag);
      UNREACHABLE();
  }
}

void StreamingScopeBuilder::VisitInterfaceType(bool simple) {
  builder_->ReadUInt();  // read klass_name.
  if (!simple) {
    intptr_t length = builder_->ReadListLength();  // read number of types.
    for (intptr_t i = 0; i < length; ++i) {
      VisitDartType();  // read the ith type.
    }
  }
}

void StreamingScopeBuilder::VisitFunctionType(bool simple) {
  if (!simple) {
    intptr_t list_length =
        builder_->ReadListLength();  // read type_parameters list length.
    for (int i = 0; i < list_length; ++i) {
      TypeParameterHelper helper(builder_);
      helper.ReadUntilExcludingAndSetJustRead(TypeParameterHelper::kBound);
      VisitDartType();  // read bound.
      helper.ReadUntilExcludingAndSetJustRead(
          TypeParameterHelper::kDefaultType);
      if (builder_->ReadTag() == kSomething) {
        VisitDartType();  // read default type.
      }
      helper.Finish();
    }
    builder_->ReadUInt();  // read required parameter count.
    builder_->ReadUInt();  // read total parameter count.
  }

  const intptr_t positional_count =
      builder_->ReadListLength();  // read positional_parameters list length.
  for (intptr_t i = 0; i < positional_count; ++i) {
    VisitDartType();  // read ith positional parameter.
  }

  if (!simple) {
    const intptr_t named_count =
        builder_->ReadListLength();  // read named_parameters list length.
    for (intptr_t i = 0; i < named_count; ++i) {
      // read string reference (i.e. named_parameters[i].name).
      builder_->SkipStringReference();
      VisitDartType();  // read named_parameters[i].type.
    }
  }

  builder_->SkipListOfStrings();  // read positional parameter names.

  if (!simple) {
    builder_->SkipCanonicalNameReference();  // read typedef reference.
  }

  VisitDartType();  // read return type.
}

void StreamingScopeBuilder::VisitTypeParameterType() {
  Function& function = Function::Handle(Z, parsed_function_->function().raw());
  while (function.IsClosureFunction()) {
    function = function.parent_function();
  }

  // The index here is the index identifying the type parameter binding site
  // inside the DILL file, which uses a different indexing system than the VM
  // uses for its 'TypeParameter's internally. This index includes both class
  // and function type parameters.

  intptr_t index = builder_->ReadUInt();  // read index for parameter.

  if (function.IsFactory()) {
    // The type argument vector is passed as the very first argument to the
    // factory constructor function.
    HandleSpecialLoad(&result_->type_arguments_variable,
                      Symbols::TypeArgumentsParameter());
  } else {
    // If the type parameter is a parameter to this or an enclosing function, we
    // can read it directly from the function type arguments vector later.
    // Otherwise, the type arguments vector we need is stored on the instance
    // object, so we need to capture 'this'.
    Class& parent_class = Class::Handle(Z, function.Owner());
    if (index < parent_class.NumTypeParameters()) {
      HandleSpecialLoad(&result_->this_variable, Symbols::This());
    }
  }

  builder_->SkipOptionalDartType();  // read bound bound.
}

void StreamingScopeBuilder::HandleLocalFunction(intptr_t parent_kernel_offset) {
  // "Peek" ahead into the function node
  intptr_t offset = builder_->ReaderOffset();

  FunctionNodeHelper function_node_helper(builder_);
  function_node_helper.ReadUntilExcluding(FunctionNodeHelper::kTypeParameters);

  LocalScope* saved_function_scope = current_function_scope_;
  FunctionNodeHelper::AsyncMarker saved_function_async_marker =
      current_function_async_marker_;
  DepthState saved_depth_state = depth_;
  depth_ = DepthState(depth_.function_ + 1);
  EnterScope(parent_kernel_offset);
  current_function_scope_ = scope_;
  current_function_async_marker_ = function_node_helper.async_marker_;
  if (depth_.function_ == 1) {
    FunctionScope function_scope = {offset, scope_};
    result_->function_scopes.Add(function_scope);
  }

  int num_type_params = 0;
  {
    AlternativeReadingScope _(&builder_->reader_);
    num_type_params = builder_->ReadListLength();
  }
  // Adding this scope here informs the type translator the type parameters of
  // this function are now in scope, although they are not defined and will be
  // filled in with dynamic. This is OK, since their definitions are not needed
  // for scope building of the enclosing function.
  StreamingDartTypeTranslator::TypeParameterScope scope(&type_translator_,
                                                        num_type_params);

  // read positional_parameters and named_parameters.
  function_node_helper.ReadUntilExcluding(
      FunctionNodeHelper::kPositionalParameters);

  ProcedureAttributesMetadata default_attrs;
  AddPositionalAndNamedParameters(0, kTypeCheckAllParameters, default_attrs);

  // "Peek" is now done.
  builder_->SetOffset(offset);

  VisitFunctionNode();  // read function node.

  ExitScope(function_node_helper.position_, function_node_helper.end_position_);
  depth_ = saved_depth_state;
  current_function_scope_ = saved_function_scope;
  current_function_async_marker_ = saved_function_async_marker;
}

void StreamingScopeBuilder::EnterScope(intptr_t kernel_offset) {
  scope_ = new (Z) LocalScope(scope_, depth_.function_, depth_.loop_);
  ASSERT(kernel_offset >= 0);
  result_->scopes.Insert(kernel_offset, scope_);
}

void StreamingScopeBuilder::ExitScope(TokenPosition start_position,
                                      TokenPosition end_position