[parser] Lift template literal invalid escape restriction

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/api-natives.h"
 #include "src/base/ieee754.h"
 #include "src/code-stubs.h"
@@ skipping 3517 matching lines @@
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_tailcalls)
 #ifdef V8_I18N_SUPPORT
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(datetime_format_to_parts)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(icu_case_mapping)
 #endif
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_restrictive_generators)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_trailing_commas)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_class_fields)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_object_rest_spread)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_dynamic_import)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_template_escapes)
 
 void InstallPublicSymbol(Factory* factory, Handle<Context> native_context,
                          const char* name, Handle<Symbol> value) {
   Handle<JSGlobalObject> global(
       JSGlobalObject::cast(native_context->global_object()));
   Handle<String> symbol_string = factory->InternalizeUtf8String("Symbol");
   Handle<JSObject> symbol = Handle<JSObject>::cast(
       JSObject::GetProperty(global, symbol_string).ToHandleChecked());
   Handle<String> name_string = factory->InternalizeUtf8String(name);
   PropertyAttributes attributes =
@@ skipping 572 matching lines @@
                                                    nullptr};
   static const char* datetime_format_to_parts_natives[] = {
       "native datetime-format-to-parts.js", nullptr};
 #endif
   static const char* harmony_restrictive_generators_natives[] = {nullptr};
   static const char* harmony_trailing_commas_natives[] = {nullptr};
   static const char* harmony_class_fields_natives[] = {nullptr};
   static const char* harmony_object_rest_spread_natives[] = {nullptr};
   static const char* harmony_async_iteration_natives[] = {nullptr};
   static const char* harmony_dynamic_import_natives[] = {nullptr};
+  static const char* harmony_template_escapes_natives[] = {nullptr};

[vogelheim, 2017/02/13 17:36:06]

Do we need this? Why? This feature doesn't seem to implement any natives.

--------------------

Background:
The original 'startup snapshot' could only be applied whole, and therefore the
snapshot couldn't contain any optional features. This initially worked fine for
--harmony-*, where the snapshot contained no 'harmony' features, and instead
they were added - if enabled - during initialization of the isolate, at some
additional runtime cost. When (most of) the --harmony-* features were turned on
by the default, this had the unfortunate effect that most of our users 'paid'
for the extra initialization. That's when the snapshot was extended to allow for
additional sections, one for each feature to be [en|dis]abled. This is the
mechanism you're extending here.

But... does this feature have any representation in the snapshot at all? I'd
think it's purely a parser issue.

[adamk, 2017/02/13 19:14:10]

This is needed to let the macro just below work. Agreed that we can probably get
rid of this soon, as we phase out experimental natives, but for now this is just
a bit of boilerplate with negligible runtime overhead.

 
   for (int i = ExperimentalNatives::GetDebuggerCount();
        i < ExperimentalNatives::GetBuiltinsCount(); i++) {
 #define INSTALL_EXPERIMENTAL_NATIVES(id, desc)                                \
   if (FLAG_##id) {                                                            \
     for (size_t j = 0; id##_natives[j] != NULL; j++) {                        \
       Vector<const char> script_name = ExperimentalNatives::GetScriptName(i); \
       if (strncmp(script_name.start(), id##_natives[j],                       \
                   script_name.length()) == 0) {                               \
         if (!Bootstrapper::CompileExperimentalBuiltin(isolate(), i)) {        \
@@ skipping 735 matching lines @@
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 }  // namespace internal
 }  // namespace v8