Implement a 'trial parse' step, that will abort pre-parsing excessively

src/parser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PARSER_H_
 #define V8_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast.h"
 #include "src/compiler.h"  // TODO(titzer): remove this include dependency
@@ skipping 755 matching lines @@
       Scope* scope, Expression* params, const Scanner::Location& params_loc,
       FormalParameterErrorLocations* error_locs, bool* is_rest, bool* ok);
 
   // Temporary glue; these functions will move to ParserBase.
   Expression* ParseV8Intrinsic(bool* ok);
   FunctionLiteral* ParseFunctionLiteral(
       const AstRawString* name, Scanner::Location function_name_location,
       bool name_is_strict_reserved, FunctionKind kind,
       int function_token_position, FunctionLiteral::FunctionType type,
       FunctionLiteral::ArityRestriction arity_restriction, bool* ok);
-  V8_INLINE void SkipLazyFunctionBody(int* materialized_literal_count,
-                                      int* expected_property_count, bool* ok);
+  V8_INLINE void SkipLazyFunctionBody(
+      int* materialized_literal_count, int* expected_property_count, bool* ok,
+      Scanner::BookmarkScope* bookmark = nullptr);
   V8_INLINE ZoneList<Statement*>* ParseEagerFunctionBody(
       const AstRawString* name, int pos, Variable* fvar,
       Token::Value fvar_init_op, FunctionKind kind, bool* ok);
 
   ClassLiteral* ParseClassLiteral(const AstRawString* name,
                                   Scanner::Location class_name_location,
                                   bool name_is_strict_reserved, int pos,
                                   bool* ok);
 
   V8_INLINE void CheckConflictingVarDeclarations(v8::internal::Scope* scope,
@@ skipping 228 matching lines @@
   IterationStatement* LookupContinueTarget(const AstRawString* label, bool* ok);
 
   void AddAssertIsConstruct(ZoneList<Statement*>* body, int pos);
 
   // Factory methods.
   FunctionLiteral* DefaultConstructor(bool call_super, Scope* scope, int pos,
                                       int end_pos);
 
   // Skip over a lazy function, either using cached data if we have it, or
   // by parsing the function with PreParser. Consumes the ending }.
+  //
+  // If bookmark is set, the (pre-)parser may decide to abort skipping
+  // in order to force the function to be eagerly parsed, after all.
+  // In this case, it'll reset the scanner using the bookmark.
   void SkipLazyFunctionBody(int* materialized_literal_count,
-                            int* expected_property_count,
-                            bool* ok);
+                            int* expected_property_count, bool* ok,
+                            Scanner::BookmarkScope* bookmark = nullptr);
 
   PreParser::PreParseResult ParseLazyFunctionBodyWithPreParser(
-      SingletonLogger* logger);
+      SingletonLogger* logger, Scanner::BookmarkScope* bookmark = nullptr);
 
   // Consumes the ending }.
   ZoneList<Statement*>* ParseEagerFunctionBody(
       const AstRawString* function_name, int pos, Variable* fvar,
       Token::Value fvar_init_op, FunctionKind kind, bool* ok);
 
   void ThrowPendingError(Isolate* isolate, Handle<Script> script);
 
   TemplateLiteralState OpenTemplateLiteral(int pos);
   void AddTemplateSpan(TemplateLiteralState* state, bool tail);
@@ skipping 40 matching lines @@
   return parser_->NewScope(parent_scope, scope_type, kind);
 }
 
 
 const AstRawString* ParserTraits::EmptyIdentifierString() {
   return parser_->ast_value_factory()->empty_string();
 }
 
 
 void ParserTraits::SkipLazyFunctionBody(int* materialized_literal_count,
-                                        int* expected_property_count,
-                                        bool* ok) {
-  return parser_->SkipLazyFunctionBody(
-      materialized_literal_count, expected_property_count, ok);
+                                        int* expected_property_count, bool* ok,
+                                        Scanner::BookmarkScope* bookmark) {
+  return parser_->SkipLazyFunctionBody(materialized_literal_count,
+                                       expected_property_count, ok, bookmark);
 }
 
 
 ZoneList<Statement*>* ParserTraits::ParseEagerFunctionBody(
     const AstRawString* name, int pos, Variable* fvar,
     Token::Value fvar_init_op, FunctionKind kind, bool* ok) {
   return parser_->ParseEagerFunctionBody(name, pos, fvar, fvar_init_op, kind,
                                          ok);
 }
 
@@ skipping 67 matching lines @@
 }
 
 
 Expression* ParserTraits::SpreadCallNew(
     Expression* function, ZoneList<v8::internal::Expression*>* args, int pos) {
   return parser_->SpreadCallNew(function, args, pos);
 }
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_