Revert "Reland^2 "[parser] Introduce UnoptimizedCompileFlags""

This reverts commit 0a59e0cb.

Reason for revert: Still causing UBSAN issues:

https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20UBSan/10729


Original change's description:
> Reland^2 "[parser] Introduce UnoptimizedCompileFlags"
> 
> This is a reland of d91679bf
> which was a reland of d91679bf
> 
> Fixes missing initialization of ParserBase::allow_eval_cache_
> 
> Original change's description:
> > [parser] Introduce UnoptimizedCompileFlags
> >
> > UnoptimizedCompileFlags defines the input flags shared between parse and
> > compile (currently parse-only). It is set initially with some values, and
> > is immutable after being passed to ParseInfo (ParseInfo still has getters
> > for the fields, but no setters).
> >
> > Since a few of the existing flags were output flags, ParseInfo now has a
> > new output_flags field, which will eventually migrate to a ParseOutputs
> > structure.
> >
> > Bug: v8:10314
> > Change-Id: If3890a5fad883bca80a97bf9dfe44d91797dc286
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2096580
> > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> > Reviewed-by: Simon Zünd <szuend@chromium.org>
> > Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#66782}
> 
> TBR=rmcilroy@chromium.org,ulan@chromium.org,szuend@chromium.org
> 
> Bug: v8:10314
> Change-Id: I470de963bdedad31fe7dd149c610f9a89bffa162
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2157030
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67245}

TBR=rmcilroy@chromium.org,leszeks@chromium.org

Change-Id: I1c5f58cc5608217a149b04aa6f50bb3d7606c26d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10314
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2157657Reviewed-by: Francis McCabe <fgm@chromium.org>
Commit-Queue: Francis McCabe <fgm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67250}

src/ast/scopes.cc

@@ -2725,7 +2725,7 @@ bool ClassScope::ResolvePrivateNames(ParseInfo* info) {
     if (var == nullptr) {
       // It's only possible to fail to resolve private names here if
       // this is at the top level or the private name is accessed through eval.
-      DCHECK(info->flags().is_eval || outer_scope_->is_script_scope());
+      DCHECK(info->is_eval() || outer_scope_->is_script_scope());
       Scanner::Location loc = proxy->location();
       info->pending_error_handler()->ReportMessageAt(
           loc.beg_pos, loc.end_pos,

src/codegen/compiler.h

@@ -14,7 +14,6 @@
 #include "src/execution/isolate.h"
 #include "src/logging/code-events.h"
 #include "src/objects/contexts.h"
-#include "src/parsing/parse-info.h"
 #include "src/utils/allocation.h"
 #include "src/zone/zone.h"
 
@@ -400,7 +399,6 @@ class V8_EXPORT_PRIVATE BackgroundCompileTask {
   // Data needed for parsing, and data needed to to be passed between thread
   // between parsing and compilation. These need to be initialized before the
   // compilation starts.
-  UnoptimizedCompileFlags flags_;
   std::unique_ptr<ParseInfo> info_;
   std::unique_ptr<Parser> parser_;
 
@@ -416,11 +414,6 @@ class V8_EXPORT_PRIVATE BackgroundCompileTask {
   // This is a raw pointer to the off-thread allocated SharedFunctionInfo.
   SharedFunctionInfo outer_function_sfi_;
 
-  // Single function data for top-level function compilation.
-  int start_position_;
-  int end_position_;
-  int function_literal_id_;
-
   int stack_size_;
   WorkerThreadRuntimeCallStats* worker_thread_runtime_call_stats_;
   AccountingAllocator* allocator_;

src/codegen/unoptimized-compilation-info.cc

@@ -18,7 +18,7 @@ namespace internal {
 UnoptimizedCompilationInfo::UnoptimizedCompilationInfo(Zone* zone,
                                                        ParseInfo* parse_info,
                                                        FunctionLiteral* literal)
-    : flags_(parse_info->flags()), zone_(zone), feedback_vector_spec_(zone) {
+    : flags_(0), zone_(zone), feedback_vector_spec_(zone) {
   // NOTE: The parse_info passed here represents the global information gathered
   // during parsing, but does not represent specific details of the actual
   // function literal being compiled for this OptimizedCompilationInfo. As such,
@@ -28,6 +28,13 @@ UnoptimizedCompilationInfo::UnoptimizedCompilationInfo(Zone* zone,
   DCHECK_NOT_NULL(literal);
   literal_ = literal;
   source_range_map_ = parse_info->source_range_map();
+
+  if (parse_info->is_eval()) MarkAsEval();
+  if (parse_info->collect_type_profile()) MarkAsCollectTypeProfile();
+  if (parse_info->might_always_opt()) MarkAsMightAlwaysOpt();
+  if (parse_info->collect_source_positions()) {
+    MarkAsForceCollectSourcePositions();
+  }
 }
 
 DeclarationScope* UnoptimizedCompilationInfo::scope() const {
@@ -45,7 +52,7 @@ int UnoptimizedCompilationInfo::num_parameters_including_this() const {
 
 SourcePositionTableBuilder::RecordingMode
 UnoptimizedCompilationInfo::SourcePositionRecordingMode() const {
-  if (flags().collect_source_positions) {
+  if (collect_source_positions()) {
     return SourcePositionTableBuilder::RECORD_SOURCE_POSITIONS;
   }
 

src/codegen/unoptimized-compilation-info.h

@@ -12,7 +12,6 @@
 #include "src/handles/handles.h"
 #include "src/objects/feedback-vector.h"
 #include "src/objects/objects.h"
-#include "src/parsing/parse-info.h"
 #include "src/utils/utils.h"
 
 namespace v8 {
@@ -36,7 +35,21 @@ class V8_EXPORT_PRIVATE UnoptimizedCompilationInfo final {
 
   Zone* zone() { return zone_; }
 
-  const UnoptimizedCompileFlags& flags() const { return flags_; }
+  // Compilation flag accessors.
+
+  void MarkAsEval() { SetFlag(kIsEval); }
+  bool is_eval() const { return GetFlag(kIsEval); }
+
+  void MarkAsCollectTypeProfile() { SetFlag(kCollectTypeProfile); }
+  bool collect_type_profile() const { return GetFlag(kCollectTypeProfile); }
+
+  void MarkAsForceCollectSourcePositions() { SetFlag(kCollectSourcePositions); }
+  bool collect_source_positions() const {
+    return GetFlag(kCollectSourcePositions);
+  }
+
+  void MarkAsMightAlwaysOpt() { SetFlag(kMightAlwaysOpt); }
+  bool might_always_opt() const { return GetFlag(kMightAlwaysOpt); }
 
   // Accessors for the input data of the function being compiled.
 
@@ -84,8 +97,20 @@ class V8_EXPORT_PRIVATE UnoptimizedCompilationInfo final {
   FeedbackVectorSpec* feedback_vector_spec() { return &feedback_vector_spec_; }
 
  private:
+  // Various configuration flags for a compilation, as well as some properties
+  // of the compiled code produced by a compilation.
+  enum Flag {
+    kIsEval = 1 << 0,
+    kCollectTypeProfile = 1 << 1,
+    kMightAlwaysOpt = 1 << 2,
+    kCollectSourcePositions = 1 << 3,
+  };
+
+  void SetFlag(Flag flag) { flags_ |= flag; }
+  bool GetFlag(Flag flag) const { return (flags_ & flag) != 0; }
+
   // Compilation flags.
-  const UnoptimizedCompileFlags flags_;
+  unsigned flags_;
 
   // The zone from which the compilation pipeline working on this
   // OptimizedCompilationInfo allocates.

src/common/globals.h

@@ -837,7 +837,7 @@ enum NativesFlag { NOT_NATIVES_CODE, EXTENSION_CODE, INSPECTOR_CODE };
 
 // ParseRestriction is used to restrict the set of valid statements in a
 // unit of compilation.  Restriction violations cause a syntax error.
-enum ParseRestriction : bool {
+enum ParseRestriction {
   NO_PARSE_RESTRICTION,         // All expressions are allowed.
   ONLY_SINGLE_FUNCTION_LITERAL  // Only a single FunctionLiteral expression.
 };

src/d8/d8.cc

@@ -544,16 +544,16 @@ bool Shell::ExecuteString(Isolate* isolate, Local<String> source,
     i::Handle<i::String> str = Utils::OpenHandle(*(source));
 
     // Set up ParseInfo.
-    i::UnoptimizedCompileFlags flags =
-        i::UnoptimizedCompileFlags::ForToplevelCompile(
-            i_isolate, true, i::construct_language_mode(i::FLAG_use_strict),
-            i::REPLMode::kNo);
-
-    i::ParseInfo parse_info(i_isolate, flags);
-
-    i::Handle<i::Script> script = parse_info.CreateScript(
-        i_isolate, str, i::kNullMaybeHandle, options.compile_options);
-    if (!i::parsing::ParseProgram(&parse_info, script, i_isolate)) {
+    i::ParseInfo parse_info(i_isolate);
+    parse_info.set_toplevel();
+    parse_info.set_allow_lazy_parsing();
+    parse_info.set_language_mode(
+        i::construct_language_mode(i::FLAG_use_strict));
+
+    i::Handle<i::Script> script =
+        parse_info.CreateScript(i_isolate, str, options.compile_options);
+    if (!i::parsing::ParseProgram(&parse_info, script, i::kNullMaybeHandle,
+                                  i_isolate)) {
       fprintf(stderr, "Failed parsing\n");
       return false;
     }

src/debug/debug-scopes.cc

@@ -40,7 +40,7 @@ ScopeIterator::ScopeIterator(Isolate* isolate, FrameInspector* frame_inspector,
   TryParseAndRetrieveScopes(strategy);
 }
 
-ScopeIterator::~ScopeIterator() = default;
+ScopeIterator::~ScopeIterator() { delete info_; }
 
 Handle<Object> ScopeIterator::GetFunctionDebugName() const {
   if (!function_.is_null()) return JSFunction::GetDebugName(function_);
@@ -236,41 +236,36 @@ void ScopeIterator::TryParseAndRetrieveScopes(ReparseStrategy strategy) {
   // Depending on the choosen strategy, the whole script or just
   // the closure is re-parsed for function scopes.
   Handle<Script> script(Script::cast(shared_info->script()), isolate_);
-
-  UnoptimizedCompileFlags flags;
   if (scope_info->scope_type() == FUNCTION_SCOPE &&
       strategy == ReparseStrategy::kFunctionLiteral) {
-    flags = UnoptimizedCompileFlags::ForFunctionCompile(isolate_, *shared_info);
+    info_ = new ParseInfo(isolate_, *shared_info);
   } else {
-    flags = UnoptimizedCompileFlags::ForScriptCompile(isolate_, *script);
-    flags.is_eager = true;
+    info_ = new ParseInfo(isolate_, *script);
+    info_->set_eager();
   }
 
   MaybeHandle<ScopeInfo> maybe_outer_scope;
   if (scope_info->scope_type() == EVAL_SCOPE || script->is_wrapped()) {
-    flags.is_eval = true;
+    info_->set_eval();
     if (!context_->IsNativeContext()) {
       maybe_outer_scope = handle(context_->scope_info(), isolate_);
     }
     // Language mode may be inherited from the eval caller.
     // Retrieve it from shared function info.
-    flags.outer_language_mode = shared_info->language_mode();
+    info_->set_language_mode(shared_info->language_mode());
   } else if (scope_info->scope_type() == MODULE_SCOPE) {
-    DCHECK(flags.is_module);
+    DCHECK(info_->is_module());
   } else {
     DCHECK(scope_info->scope_type() == SCRIPT_SCOPE ||
            scope_info->scope_type() == FUNCTION_SCOPE);
   }
 
-  info_ = std::make_unique<ParseInfo>(isolate_, flags);
-
   const bool parse_result =
-      flags.is_toplevel
-          ? parsing::ParseProgram(info_.get(), script, maybe_outer_scope,
-                                  isolate_)
-          : parsing::ParseFunction(info_.get(), shared_info, isolate_);
+      info_->is_toplevel()
+          ? parsing::ParseProgram(info_, script, maybe_outer_scope, isolate_)
+          : parsing::ParseFunction(info_, shared_info, isolate_);
 
-  if (parse_result && Rewriter::Rewrite(info_.get())) {
+  if (parse_result && Rewriter::Rewrite(info_)) {
     info_->ast_value_factory()->Internalize(isolate_);
     DeclarationScope* literal_scope = info_->literal()->scope();
 
@@ -285,7 +280,7 @@ void ScopeIterator::TryParseAndRetrieveScopes(ReparseStrategy strategy) {
                          ? scope_chain_retriever.ClosureScope()
                          : literal_scope;
 
-    CHECK(DeclarationScope::Analyze(info_.get()));
+    CHECK(DeclarationScope::Analyze(info_));
     if (ignore_nested_scopes) {
       current_scope_ = closure_scope_;
       start_scope_ = current_scope_;

src/debug/debug-scopes.h

@@ -109,7 +109,7 @@ class ScopeIterator {
 
  private:
   Isolate* isolate_;
-  std::unique_ptr<ParseInfo> info_;
+  ParseInfo* info_ = nullptr;
   FrameInspector* const frame_inspector_ = nullptr;
   Handle<JSGeneratorObject> generator_;
   Handle<JSFunction> function_;

src/debug/liveedit.cc

@@ -750,6 +750,7 @@ class CollectFunctionLiterals final
 bool ParseScript(Isolate* isolate, Handle<Script> script, ParseInfo* parse_info,
                  bool compile_as_well, std::vector<FunctionLiteral*>* literals,
                  debug::LiveEditResult* result) {
+  parse_info->set_eager();
   v8::TryCatch try_catch(reinterpret_cast<v8::Isolate*>(isolate));
   Handle<SharedFunctionInfo> shared;
   bool success = false;
@@ -1057,21 +1058,15 @@ void LiveEdit::PatchScript(Isolate* isolate, Handle<Script> script,
     return;
   }
 
-  UnoptimizedCompileFlags flags =
-      UnoptimizedCompileFlags::ForScriptCompile(isolate, *script);
-  flags.is_eager = true;
-  ParseInfo parse_info(isolate, flags);
+  ParseInfo parse_info(isolate, *script);
   std::vector<FunctionLiteral*> literals;
   if (!ParseScript(isolate, script, &parse_info, false, &literals, result))
     return;
 
   Handle<Script> new_script = isolate->factory()->CloneScript(script);
   new_script->set_source(*new_source);
-  UnoptimizedCompileFlags new_flags =
-      UnoptimizedCompileFlags::ForScriptCompile(isolate, *new_script);
-  new_flags.is_eager = true;
-  ParseInfo new_parse_info(isolate, new_flags);
   std::vector<FunctionLiteral*> new_literals;
+  ParseInfo new_parse_info(isolate, *new_script);
   if (!ParseScript(isolate, new_script, &new_parse_info, true, &new_literals,
                    result)) {
     return;

src/execution/messages.cc

@@ -1252,8 +1252,7 @@ Handle<String> RenderCallSite(Isolate* isolate, Handle<Object> object,
                               MessageLocation* location,
                               CallPrinter::ErrorHint* hint) {
   if (ComputeLocation(isolate, location)) {
-    ParseInfo info(isolate, i::UnoptimizedCompileFlags::ForFunctionCompile(
-                                isolate, *location->shared()));
+    ParseInfo info(isolate, *location->shared());
     if (parsing::ParseAny(&info, location->shared(), isolate)) {
       info.ast_value_factory()->Internalize(isolate);
       CallPrinter printer(isolate, location->shared()->IsUserJavaScript());
@@ -1311,8 +1310,7 @@ Object ErrorUtils::ThrowSpreadArgIsNullOrUndefinedError(Isolate* isolate,
   MessageLocation location;
   Handle<String> callsite;
   if (ComputeLocation(isolate, &location)) {
-    ParseInfo info(isolate, i::UnoptimizedCompileFlags::ForFunctionCompile(
-                                isolate, *location.shared()));
+    ParseInfo info(isolate, *location.shared());
     if (parsing::ParseAny(&info, location.shared(), isolate)) {
       info.ast_value_factory()->Internalize(isolate);
       CallPrinter printer(isolate, location.shared()->IsUserJavaScript(),
@@ -1387,8 +1385,7 @@ Object ErrorUtils::ThrowLoadFromNullOrUndefined(Isolate* isolate,
   if (ComputeLocation(isolate, &location)) {
     location_computed = true;
 
-    ParseInfo info(isolate, i::UnoptimizedCompileFlags::ForFunctionCompile(
-                                isolate, *location.shared()));
+    ParseInfo info(isolate, *location.shared());
     if (parsing::ParseAny(&info, location.shared(), isolate)) {
       info.ast_value_factory()->Internalize(isolate);
       CallPrinter printer(isolate, location.shared()->IsUserJavaScript());

src/interpreter/bytecode-generator.cc

@@ -1332,7 +1332,7 @@ void BytecodeGenerator::GenerateBytecodeBody() {
   if (FLAG_trace) builder()->CallRuntime(Runtime::kTraceEnter);
 
   // Emit type profile call.
-  if (info()->flags().collect_type_profile) {
+  if (info()->collect_type_profile()) {
     feedback_spec()->AddTypeProfileSlot();
     int num_parameters = closure_scope()->num_parameters();
     for (int i = 0; i < num_parameters; i++) {
@@ -2134,7 +2134,7 @@ void BytecodeGenerator::VisitFunctionLiteral(FunctionLiteral* expr) {
   DCHECK(expr->scope()->outer_scope() == current_scope());
   uint8_t flags = CreateClosureFlags::Encode(
       expr->pretenure(), closure_scope()->is_function_scope(),
-      info()->flags().might_always_opt);
+      info()->might_always_opt());
   size_t entry = builder()->AllocateDeferredConstantPoolEntry();
   builder()->CreateClosure(entry, GetCachedCreateClosureSlot(expr), flags);
   function_literals_.push_back(std::make_pair(expr, entry));
@@ -3197,7 +3197,7 @@ void BytecodeGenerator::BuildReturn(int source_position) {
     builder()->StoreAccumulatorInRegister(result).CallRuntime(
         Runtime::kTraceExit, result);
   }
-  if (info()->flags().collect_type_profile) {
+  if (info()->collect_type_profile()) {
     builder()->CollectTypeProfile(info()->literal()->return_position());
   }
   builder()->SetReturnPosition(source_position, info()->literal());

src/interpreter/interpreter.cc

@@ -191,18 +191,17 @@ void InterpreterCompilationJob::CheckAndPrintBytecodeMismatch(
     std::cerr << "Bytecode mismatch";
 #ifdef OBJECT_PRINT
     std::cerr << " found for function: ";
-    MaybeHandle<String> maybe_name = parse_info()->literal()->GetName(isolate);
-    Handle<String> name;
-    if (maybe_name.ToHandle(&name) && name->length() != 0) {
-      name->StringPrint(std::cerr);
-    } else {
+    Handle<String> name = parse_info()->function_name()->string();
+    if (name->length() == 0) {
       std::cerr << "anonymous";
+    } else {
+      name->StringPrint(std::cerr);
     }
     Object script_name = script->GetNameOrSourceURL();
     if (script_name.IsString()) {
       std::cerr << " ";
       String::cast(script_name).StringPrint(std::cerr);
-      std::cerr << ":" << parse_info()->literal()->start_position();
+      std::cerr << ":" << parse_info()->start_position();
     }
 #endif
     std::cerr << "\nOriginal bytecode:\n";

src/objects/function-kind.h

@@ -6,7 +6,6 @@
 #define V8_OBJECTS_FUNCTION_KIND_H_
 
 #include "src/base/bounds.h"
-#include "src/base/macros.h"
 
 namespace v8 {
 namespace internal {
@@ -57,9 +56,6 @@ enum FunctionKind : uint8_t {
   kLastFunctionKind = kClassMembersInitializerFunction,
 };
 
-constexpr int kFunctionKindBitSize = 5;
-STATIC_ASSERT(kLastFunctionKind < (1 << kFunctionKindBitSize));
-
 inline bool IsArrowFunction(FunctionKind kind) {
   return base::IsInRange(kind, FunctionKind::kArrowFunction,
                          FunctionKind::kAsyncArrowFunction);

src/objects/shared-function-info-inl.h

@@ -5,7 +5,6 @@
 #ifndef V8_OBJECTS_SHARED_FUNCTION_INFO_INL_H_
 #define V8_OBJECTS_SHARED_FUNCTION_INFO_INL_H_
 
-#include "src/base/macros.h"
 #include "src/objects/shared-function-info.h"
 
 #include "src/handles/handles-inl.h"
@@ -251,7 +250,6 @@ void SharedFunctionInfo::set_language_mode(LanguageMode language_mode) {
 }
 
 FunctionKind SharedFunctionInfo::kind() const {
-  STATIC_ASSERT(FunctionKindBits::kSize == kFunctionKindBitSize);
   return FunctionKindBits::decode(flags());
 }
 

src/parsing/parser-base.h

@@ -23,7 +23,6 @@
 #include "src/objects/function-kind.h"
 #include "src/parsing/expression-scope.h"
 #include "src/parsing/func-name-inferrer.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/scanner.h"
 #include "src/parsing/token.h"
 #include "src/utils/pointer-with-payload.h"
@@ -242,7 +241,7 @@ class ParserBase {
              v8::Extension* extension, AstValueFactory* ast_value_factory,
              PendingCompilationErrorHandler* pending_error_handler,
              RuntimeCallStats* runtime_call_stats, Logger* logger,
-             UnoptimizedCompileFlags flags, bool parsing_on_main_thread)
+             int script_id, bool parsing_module, bool parsing_on_main_thread)
       : scope_(nullptr),
         original_scope_(nullptr),
         function_state_(nullptr),
@@ -253,22 +252,37 @@ class ParserBase {
         runtime_call_stats_(runtime_call_stats),
         logger_(logger),
         parsing_on_main_thread_(parsing_on_main_thread),
+        parsing_module_(parsing_module),
         stack_limit_(stack_limit),
         pending_error_handler_(pending_error_handler),
         zone_(zone),
         expression_scope_(nullptr),
         scanner_(scanner),
-        flags_(flags),
         function_literal_id_(0),
-        default_eager_compile_hint_(FunctionLiteral::kShouldLazyCompile) {
+        script_id_(script_id),
+        default_eager_compile_hint_(FunctionLiteral::kShouldLazyCompile),
+        allow_natives_(false),
+        allow_harmony_dynamic_import_(false),
+        allow_harmony_import_meta_(false),
+        allow_harmony_private_methods_(false),
+        allow_harmony_top_level_await_(false),
+        allow_eval_cache_(true) {
     pointer_buffer_.reserve(32);
     variable_buffer_.reserve(32);
   }
 
-  const UnoptimizedCompileFlags& flags() const { return flags_; }
+#define ALLOW_ACCESSORS(name)                           \
+  bool allow_##name() const { return allow_##name##_; } \
+  void set_allow_##name(bool allow) { allow_##name##_ = allow; }
 
-  bool allow_eval_cache() const { return allow_eval_cache_; }
-  void set_allow_eval_cache(bool allow) { allow_eval_cache_ = allow; }
+  ALLOW_ACCESSORS(natives)
+  ALLOW_ACCESSORS(harmony_dynamic_import)
+  ALLOW_ACCESSORS(harmony_import_meta)
+  ALLOW_ACCESSORS(harmony_private_methods)
+  ALLOW_ACCESSORS(harmony_top_level_await)
+  ALLOW_ACCESSORS(eval_cache)
+
+#undef ALLOW_ACCESSORS
 
   V8_INLINE bool has_error() const { return scanner()->has_parser_error(); }
 
@@ -855,6 +869,8 @@ class ParserBase {
     // Any further calls to Next or peek will return the illegal token.
     if (GetCurrentStackPosition() < stack_limit_) set_stack_overflow();
   }
+  int script_id() { return script_id_; }
+  void set_script_id(int id) { script_id_ = id; }
 
   V8_INLINE Token::Value peek() { return scanner()->peek(); }
 
@@ -1045,7 +1061,7 @@ class ParserBase {
     return IsResumableFunction(function_state_->kind());
   }
   bool is_await_allowed() const {
-    return is_async_function() || (flags().allow_harmony_top_level_await &&
+    return is_async_function() || (allow_harmony_top_level_await() &&
                                    IsModule(function_state_->kind()));
   }
   const PendingCompilationErrorHandler* pending_error_handler() const {
@@ -1500,6 +1516,7 @@ class ParserBase {
   RuntimeCallStats* runtime_call_stats_;
   internal::Logger* logger_;
   bool parsing_on_main_thread_;
+  const bool parsing_module_;
   uintptr_t stack_limit_;
   PendingCompilationErrorHandler* pending_error_handler_;
 
@@ -1514,8 +1531,8 @@ class ParserBase {
 
   Scanner* scanner_;
 
-  const UnoptimizedCompileFlags flags_;
   int function_literal_id_;
+  int script_id_;
 
   FunctionLiteral::EagerCompileHint default_eager_compile_hint_;
 
@@ -1554,7 +1571,12 @@ class ParserBase {
 
   bool accept_IN_ = true;
 
-  bool allow_eval_cache_ = true;
+  bool allow_natives_;
+  bool allow_harmony_dynamic_import_;
+  bool allow_harmony_import_meta_;
+  bool allow_harmony_private_methods_;
+  bool allow_harmony_top_level_await_;
+  bool allow_eval_cache_;
 };
 
 template <typename Impl>
@@ -1604,7 +1626,7 @@ ParserBase<Impl>::ParseAndClassifyIdentifier(Token::Value next) {
   }
 
   if (!Token::IsValidIdentifier(next, language_mode(), is_generator(),
-                                flags().is_module || is_async_function())) {
+                                parsing_module_ || is_async_function())) {
     ReportUnexpectedToken(next);
     return impl()->EmptyIdentifierString();
   }
@@ -1628,7 +1650,7 @@ typename ParserBase<Impl>::IdentifierT ParserBase<Impl>::ParseIdentifier(
 
   if (!Token::IsValidIdentifier(
           next, language_mode(), IsGeneratorFunction(function_kind),
-          flags().is_module || IsAsyncFunction(function_kind))) {
+          parsing_module_ || IsAsyncFunction(function_kind))) {
     ReportUnexpectedToken(next);
     return impl()->EmptyIdentifierString();
   }
@@ -1839,7 +1861,7 @@ ParserBase<Impl>::ParsePrimaryExpression() {
       return ParseSuperExpression(is_new);
     }
     case Token::IMPORT:
-      if (!flags().allow_harmony_dynamic_import) break;
+      if (!allow_harmony_dynamic_import()) break;
       return ParseImportExpressions();
 
     case Token::LBRACK:
@@ -1902,7 +1924,7 @@ ParserBase<Impl>::ParsePrimaryExpression() {
       return ParseTemplateLiteral(impl()->NullExpression(), beg_pos, false);
 
     case Token::MOD:
-      if (flags().allow_natives_syntax || extension_ != nullptr) {
+      if (allow_natives() || extension_ != nullptr) {
         return ParseV8Intrinsic();
       }
       break;
@@ -2148,7 +2170,7 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseProperty(
         prop_info->kind = ParsePropertyKind::kNotSet;
         return impl()->FailureExpression();
       }
-      if (V8_UNLIKELY(!flags().allow_harmony_private_methods &&
+      if (V8_UNLIKELY(!allow_harmony_private_methods() &&
                       (IsAccessor(prop_info->kind) ||
                        prop_info->kind == ParsePropertyKind::kMethod))) {
         ReportUnexpectedToken(Next());
@@ -2496,7 +2518,7 @@ ParserBase<Impl>::ParseObjectPropertyDefinition(ParsePropertyInfo* prop_info,
       DCHECK_EQ(function_flags, ParseFunctionFlag::kIsNormal);
 
       if (!Token::IsValidIdentifier(name_token, language_mode(), is_generator(),
-                                    flags().is_module || is_async_function())) {
+                                    parsing_module_ || is_async_function())) {
         ReportUnexpectedToken(Next());
         return impl()->NullLiteralProperty();
       }
@@ -3410,9 +3432,8 @@ ParserBase<Impl>::ParseMemberWithPresentNewPrefixesExpression() {
   if (peek() == Token::SUPER) {
     const bool is_new = true;
     result = ParseSuperExpression(is_new);
-  } else if (flags().allow_harmony_dynamic_import && peek() == Token::IMPORT &&
-             (!flags().allow_harmony_import_meta ||
-              PeekAhead() == Token::LPAREN)) {
+  } else if (allow_harmony_dynamic_import() && peek() == Token::IMPORT &&
+             (!allow_harmony_import_meta() || PeekAhead() == Token::LPAREN)) {
     impl()->ReportMessageAt(scanner()->peek_location(),
                             MessageTemplate::kImportCallNotNewExpression);
     return impl()->FailureExpression();
@@ -3510,14 +3531,14 @@ ParserBase<Impl>::ParseMemberExpression() {
 template <typename Impl>
 typename ParserBase<Impl>::ExpressionT
 ParserBase<Impl>::ParseImportExpressions() {
-  DCHECK(flags().allow_harmony_dynamic_import);
+  DCHECK(allow_harmony_dynamic_import());
 
   Consume(Token::IMPORT);
   int pos = position();
-  if (flags().allow_harmony_import_meta && Check(Token::PERIOD)) {
+  if (allow_harmony_import_meta() && Check(Token::PERIOD)) {
     ExpectContextualKeyword(ast_value_factory()->meta_string(), "import.meta",
                             pos);
-    if (!flags().is_module) {
+    if (!parsing_module_) {
       impl()->ReportMessageAt(scanner()->location(),
                               MessageTemplate::kImportMetaOutsideModule);
       return impl()->FailureExpression();
@@ -3527,7 +3548,7 @@ ParserBase<Impl>::ParseImportExpressions() {
   }
 
   if (V8_UNLIKELY(peek() != Token::LPAREN)) {
-    if (!flags().is_module) {
+    if (!parsing_module_) {
       impl()->ReportMessageAt(scanner()->location(),
                               MessageTemplate::kImportOutsideModule);
     } else {
@@ -4449,9 +4470,8 @@ ParserBase<Impl>::ParseArrowFunctionLiteral(
     const char* event_name =
         is_lazy_top_level_function ? "preparse-no-resolution" : "parse";
     const char* name = "arrow function";
-    logger_->FunctionEvent(event_name, flags().script_id, ms,
-                           scope->start_position(), scope->end_position(), name,
-                           strlen(name));
+    logger_->FunctionEvent(event_name, script_id(), ms, scope->start_position(),
+                           scope->end_position(), name, strlen(name));
   }
 
   return function_literal;

src/parsing/parser.h

@@ -14,7 +14,6 @@
 #include "src/base/compiler-specific.h"
 #include "src/base/threaded-list.h"
 #include "src/common/globals.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/parser-base.h"
 #include "src/parsing/parsing.h"
 #include "src/parsing/preparser.h"
@@ -135,8 +134,7 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
 
   static bool IsPreParser() { return false; }
 
-  void ParseOnBackground(ParseInfo* info, int start_position, int end_position,
-                         int function_literal_id);
+  void ParseOnBackground(ParseInfo* info);
 
   // Initializes an empty scope chain for top-level scripts, or scopes which
   // consist of only the native context.
@@ -217,8 +215,6 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
   FunctionLiteral* ParseFunction(Isolate* isolate, ParseInfo* info,
                                  Handle<SharedFunctionInfo> shared_info);
   FunctionLiteral* DoParseFunction(Isolate* isolate, ParseInfo* info,
-                                   int start_position, int end_position,
-                                   int function_literal_id,
                                    const AstRawString* raw_name);
 
   // Called by ParseProgram after setting up the scanner.
@@ -243,9 +239,15 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
     if (reusable_preparser_ == nullptr) {
       reusable_preparser_ = new PreParser(
           &preparser_zone_, &scanner_, stack_limit_, ast_value_factory(),
-          pending_error_handler(), runtime_call_stats_, logger_, flags(),
-          parsing_on_main_thread_);
-      reusable_preparser_->set_allow_eval_cache(allow_eval_cache());
+          pending_error_handler(), runtime_call_stats_, logger_, -1,
+          parsing_module_, parsing_on_main_thread_);
+#define SET_ALLOW(name) reusable_preparser_->set_allow_##name(allow_##name());
+      SET_ALLOW(natives);
+      SET_ALLOW(harmony_dynamic_import);
+      SET_ALLOW(harmony_import_meta);
+      SET_ALLOW(harmony_private_methods);
+      SET_ALLOW(eval_cache);
+#undef SET_ALLOW
       preparse_data_buffer_.reserve(128);
     }
     return reusable_preparser_;

src/parsing/parsing.cc

@@ -22,7 +22,7 @@ namespace parsing {
 bool ParseProgram(ParseInfo* info, Handle<Script> script,
                   MaybeHandle<ScopeInfo> maybe_outer_scope_info,
                   Isolate* isolate, ReportErrorsAndStatisticsMode mode) {
-  DCHECK(info->flags().is_toplevel);
+  DCHECK(info->is_toplevel());
   DCHECK_NULL(info->literal());
 
   VMState<PARSER> state(isolate);
@@ -44,7 +44,7 @@ bool ParseProgram(ParseInfo* info, Handle<Script> script,
   info->set_literal(result);
   if (result) {
     info->set_language_mode(info->literal()->language_mode());
-    if (info->flags().is_eval) {
+    if (info->is_eval()) {
       info->set_allow_eval_cache(parser.allow_eval_cache());
     }
   }
@@ -66,7 +66,7 @@ bool ParseProgram(ParseInfo* info, Handle<Script> script, Isolate* isolate,
 
 bool ParseFunction(ParseInfo* info, Handle<SharedFunctionInfo> shared_info,
                    Isolate* isolate, ReportErrorsAndStatisticsMode mode) {
-  DCHECK(!info->flags().is_toplevel);
+  DCHECK(!info->is_toplevel());
   DCHECK(!shared_info.is_null());
   DCHECK_NULL(info->literal());
 
@@ -91,7 +91,7 @@ bool ParseFunction(ParseInfo* info, Handle<SharedFunctionInfo> shared_info,
   info->set_literal(result);
   if (result) {
     info->ast_value_factory()->Internalize(isolate);
-    if (info->flags().is_eval) {
+    if (info->is_eval()) {
       info->set_allow_eval_cache(parser.allow_eval_cache());
     }
   }
@@ -109,7 +109,7 @@ bool ParseFunction(ParseInfo* info, Handle<SharedFunctionInfo> shared_info,
 bool ParseAny(ParseInfo* info, Handle<SharedFunctionInfo> shared_info,
               Isolate* isolate, ReportErrorsAndStatisticsMode mode) {
   DCHECK(!shared_info.is_null());
-  if (info->flags().is_toplevel) {
+  if (info->is_toplevel()) {
     MaybeHandle<ScopeInfo> maybe_outer_scope_info;
     if (shared_info->HasOuterScopeInfo()) {
       maybe_outer_scope_info =

src/parsing/preparser.cc

@@ -78,7 +78,7 @@ PreParser::PreParseResult PreParser::PreParseProgram() {
   // ModuleDeclarationInstantiation for Source Text Module Records creates a
   // new Module Environment Record whose outer lexical environment record is
   // the global scope.
-  if (flags().is_module) scope = NewModuleScope(scope);
+  if (parsing_module_) scope = NewModuleScope(scope);
 
   FunctionState top_scope(&function_state_, &scope_, scope);
   original_scope_ = scope_;
@@ -105,9 +105,11 @@ void PreParserFormalParameters::ValidateStrictMode(PreParser* preparser) const {
 PreParser::PreParseResult PreParser::PreParseFunction(
     const AstRawString* function_name, FunctionKind kind,
     FunctionSyntaxKind function_syntax_kind, DeclarationScope* function_scope,
-    int* use_counts, ProducedPreparseData** produced_preparse_data) {
+    int* use_counts, ProducedPreparseData** produced_preparse_data,
+    int script_id) {
   DCHECK_EQ(FUNCTION_SCOPE, function_scope->scope_type());
   use_counts_ = use_counts;
+  set_script_id(script_id);
 #ifdef DEBUG
   function_scope->set_is_being_lazily_parsed(true);
 #endif
@@ -357,7 +359,7 @@ PreParser::Expression PreParser::ParseFunctionLiteral(
       name_byte_length = string->byte_length();
     }
     logger_->FunctionEvent(
-        event_name, flags().script_id, ms, function_scope->start_position(),
+        event_name, script_id(), ms, function_scope->start_position(),
         function_scope->end_position(), name, name_byte_length);
   }
 

src/parsing/preparser.h

@@ -8,7 +8,6 @@
 #include "src/ast/ast-value-factory.h"
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/parser-base.h"
 #include "src/parsing/pending-compilation-error-handler.h"
 #include "src/parsing/preparser-logger.h"
@@ -922,11 +921,12 @@ class PreParser : public ParserBase<PreParser> {
             AstValueFactory* ast_value_factory,
             PendingCompilationErrorHandler* pending_error_handler,
             RuntimeCallStats* runtime_call_stats, Logger* logger,
-            UnoptimizedCompileFlags flags, bool parsing_on_main_thread = true)
+            int script_id = -1, bool parsing_module = false,
+            bool parsing_on_main_thread = true)
       : ParserBase<PreParser>(zone, scanner, stack_limit, nullptr,
                               ast_value_factory, pending_error_handler,
-                              runtime_call_stats, logger, flags,
-                              parsing_on_main_thread),
+                              runtime_call_stats, logger, script_id,
+                              parsing_module, parsing_on_main_thread),
         use_counts_(nullptr),
         preparse_data_builder_(nullptr),
         preparse_data_builder_buffer_() {
@@ -954,7 +954,8 @@ class PreParser : public ParserBase<PreParser> {
   PreParseResult PreParseFunction(
       const AstRawString* function_name, FunctionKind kind,
       FunctionSyntaxKind function_syntax_kind, DeclarationScope* function_scope,
-      int* use_counts, ProducedPreparseData** produced_preparser_scope_data);
+      int* use_counts, ProducedPreparseData** produced_preparser_scope_data,
+      int script_id);
 
   PreparseDataBuilder* preparse_data_builder() const {
     return preparse_data_builder_;

src/parsing/rewriter.cc

@@ -400,7 +400,7 @@ base::Optional<VariableProxy*> Rewriter::RewriteBody(
       int pos = kNoSourcePosition;
       VariableProxy* result_value =
           processor.factory()->NewVariableProxy(result, pos);
-      if (!info->flags().is_repl_mode) {
+      if (!info->is_repl_mode()) {
         Statement* result_statement =
             processor.factory()->NewReturnStatement(result_value, pos);
         body->Add(result_statement, info->zone());

src/parsing/scanner.cc

@@ -13,7 +13,6 @@
 #include "src/ast/ast-value-factory.h"
 #include "src/numbers/conversions-inl.h"
 #include "src/objects/bigint.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/scanner-inl.h"
 #include "src/zone/zone.h"
 
@@ -90,10 +89,10 @@ bool Scanner::BookmarkScope::HasBeenApplied() const {
 // ----------------------------------------------------------------------------
 // Scanner
 
-Scanner::Scanner(Utf16CharacterStream* source, UnoptimizedCompileFlags flags)
-    : flags_(flags),
-      source_(source),
+Scanner::Scanner(Utf16CharacterStream* source, bool is_module)
+    : source_(source),
       found_html_comment_(false),
+      is_module_(is_module),
       octal_pos_(Location::invalid()),
       octal_message_(MessageTemplate::kNone) {
   DCHECK_NOT_NULL(source);
@@ -189,7 +188,7 @@ Token::Value Scanner::PeekAhead() {
 }
 
 Token::Value Scanner::SkipSingleHTMLComment() {
-  if (flags_.is_module) {
+  if (is_module_) {
     ReportScannerError(source_pos(), MessageTemplate::kHtmlCommentInModule);
     return Token::ILLEGAL;
   }

src/parsing/scanner.h

@@ -15,7 +15,6 @@
 #include "src/common/globals.h"
 #include "src/common/message-template.h"
 #include "src/parsing/literal-buffer.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/token.h"
 #include "src/strings/char-predicates.h"
 #include "src/strings/unicode.h"
@@ -270,7 +269,7 @@ class V8_EXPORT_PRIVATE Scanner {
   static const int kNoOctalLocation = -1;
   static const uc32 kEndOfInput = Utf16CharacterStream::kEndOfInput;
 
-  explicit Scanner(Utf16CharacterStream* source, UnoptimizedCompileFlags flags);
+  explicit Scanner(Utf16CharacterStream* source, bool is_module);
 
   void Initialize();
 
@@ -704,8 +703,6 @@ class V8_EXPORT_PRIVATE Scanner {
   const TokenDesc& next() const { return *next_; }
   const TokenDesc& next_next() const { return *next_next_; }
 
-  UnoptimizedCompileFlags flags_;
-
   TokenDesc* current_;    // desc for current token (as returned by Next())
   TokenDesc* next_;       // desc for next token (one token look-ahead)
   TokenDesc* next_next_;  // desc for the token after next (after PeakAhead())
@@ -721,6 +718,8 @@ class V8_EXPORT_PRIVATE Scanner {
   // Whether this scanner encountered an HTML comment.
   bool found_html_comment_;
 
+  const bool is_module_;
+
   // Values parsed from magic comments.
   LiteralBuffer source_url_;
   LiteralBuffer source_mapping_url_;

test/cctest/parsing/test-preparser.cc

@@ -707,12 +707,9 @@ TEST(PreParserScopeAnalysis) {
           shared->uncompiled_data_with_preparse_data().preparse_data(),
           isolate);
 
-      i::UnoptimizedCompileFlags flags =
-          i::UnoptimizedCompileFlags::ForFunctionCompile(isolate, *shared);
-      flags.is_lazy_compile = true;
-
       // Parse the lazy function using the scope data.
-      i::ParseInfo using_scope_data(isolate, flags);
+      i::ParseInfo using_scope_data(isolate, *shared);
+      using_scope_data.set_lazy_compile();
       using_scope_data.set_consumed_preparse_data(
           i::ConsumedPreparseData::For(isolate, produced_data_on_heap));
       CHECK(i::parsing::ParseFunction(&using_scope_data, shared, isolate));
@@ -727,7 +724,8 @@ TEST(PreParserScopeAnalysis) {
       CHECK(i::DeclarationScope::Analyze(&using_scope_data));
 
       // Parse the lazy function again eagerly to produce baseline data.
-      i::ParseInfo not_using_scope_data(isolate, flags);
+      i::ParseInfo not_using_scope_data(isolate, *shared);
+      not_using_scope_data.set_lazy_compile();
       CHECK(i::parsing::ParseFunction(&not_using_scope_data, shared, isolate));
 
       // Verify that we didn't skip anything (there's no preparsed scope data,
@@ -761,9 +759,7 @@ TEST(Regress753896) {
   i::Handle<i::String> source = factory->InternalizeUtf8String(
       "function lazy() { let v = 0; if (true) { var v = 0; } }");
   i::Handle<i::Script> script = factory->NewScript(source);
-  i::UnoptimizedCompileFlags flags =
-      i::UnoptimizedCompileFlags::ForScriptCompile(isolate, *script);
-  i::ParseInfo info(isolate, flags);
+  i::ParseInfo info(isolate, *script);
 
   // We don't assert that parsing succeeded or that it failed; currently the
   // error is not detected inside lazy functions, but it might be in the future.

test/cctest/parsing/test-scanner.cc

@@ -7,7 +7,6 @@
 
 #include "src/handles/handles-inl.h"
 #include "src/objects/objects-inl.h"
-#include "src/parsing/parse-info.h"
 #include "src/parsing/scanner-character-streams.h"
 #include "src/parsing/scanner.h"
 #include "test/cctest/cctest.h"
@@ -35,9 +34,8 @@ struct ScannerTestHelper {
 ScannerTestHelper make_scanner(const char* src) {
   ScannerTestHelper helper;
   helper.stream = ScannerStream::ForTesting(src);
-  helper.scanner = std::unique_ptr<Scanner>(
-      new Scanner(helper.stream.get(),
-                  UnoptimizedCompileFlags::ForTest(CcTest::i_isolate())));
+  helper.scanner =
+      std::unique_ptr<Scanner>(new Scanner(helper.stream.get(), false));
   helper.scanner->Initialize();
   return helper;
 }

test/fuzzer/parser.cc

@@ -80,10 +80,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
 
   v8::internal::Handle<v8::internal::Script> script =
       factory->NewScript(source.ToHandleChecked());
-  v8::internal::UnoptimizedCompileFlags flags =
-      v8::internal::UnoptimizedCompileFlags::ForScriptCompile(i_isolate,
-                                                              *script);
-  v8::internal::ParseInfo info(i_isolate, flags);
+  v8::internal::ParseInfo info(i_isolate, *script);
   if (!v8::internal::parsing::ParseProgram(&info, script, i_isolate)) {
     i_isolate->OptionalRescheduleException(true);
   }

test/unittests/heap/off-thread-factory-unittest.cc

@@ -15,7 +15,6 @@
 #include "src/execution/off-thread-isolate.h"
 #include "src/handles/handles-inl.h"
 #include "src/handles/handles.h"
-#include "src/handles/maybe-handles.h"
 #include "src/heap/off-thread-factory-inl.h"
 #include "src/objects/fixed-array.h"
 #include "src/objects/script.h"
@@ -56,10 +55,7 @@ class OffThreadFactoryTest : public TestWithIsolateAndZone {
  public:
   OffThreadFactoryTest()
       : TestWithIsolateAndZone(),
-        parse_info_(isolate(), UnoptimizedCompileFlags::ForToplevelCompile(
-                                   isolate(), true,
-                                   construct_language_mode(FLAG_use_strict),
-                                   REPLMode::kNo)),
+        parse_info_(isolate()),
         off_thread_isolate_(isolate(), parse_info_.zone()) {}
 
   FunctionLiteral* ParseProgram(const char* source) {
@@ -72,6 +68,8 @@ class OffThreadFactoryTest : public TestWithIsolateAndZone {
 
     parse_info_.set_character_stream(
         ScannerStream::ForTesting(utf16_source.data(), utf16_source.size()));
+    parse_info_.set_toplevel();
+    parse_info_.set_allow_lazy_parsing();
 
     {
       DisallowHeapAllocation no_allocation;
@@ -80,7 +78,7 @@ class OffThreadFactoryTest : public TestWithIsolateAndZone {
 
       Parser parser(parse_info());
       parser.InitializeEmptyScopeChain(parse_info());
-      parser.ParseOnBackground(parse_info(), 0, 0, kFunctionLiteralIdTopLevel);
+      parser.ParseOnBackground(parse_info());
 
       CHECK(DeclarationScope::Analyze(parse_info()));
     }
@@ -90,7 +88,7 @@ class OffThreadFactoryTest : public TestWithIsolateAndZone {
 
     script_ = parse_info_.CreateScript(off_thread_isolate(),
                                        off_thread_factory()->empty_string(),
-                                       kNullMaybeHandle, ScriptOriginOptions());
+                                       ScriptOriginOptions());
 
     // Create the SFI list on the script so that SFI SetScript works.
     Handle<WeakFixedArray> infos = off_thread_factory()->NewWeakFixedArray(

test/unittests/test-helpers.cc

@@ -56,8 +56,8 @@ Handle<SharedFunctionInfo> CreateSharedFunctionInfo(
 std::unique_ptr<ParseInfo> OuterParseInfoForShared(
     Isolate* isolate, Handle<SharedFunctionInfo> shared) {
   Script script = Script::cast(shared->script());
-  std::unique_ptr<ParseInfo> result = std::make_unique<ParseInfo>(
-      isolate, i::UnoptimizedCompileFlags::ForScriptCompile(isolate, script));
+  std::unique_ptr<ParseInfo> result =
+      std::make_unique<ParseInfo>(isolate, script);
 
   // Create a character stream to simulate the parser having done so for the
   // to-level ParseProgram.