[strong] Stricter check for referring to other classes inside methods.

src/preparser.h

Index: src/preparser.h
diff --git a/src/preparser.h b/src/preparser.h
index 0440d831eea5105552c2c268534faead9ff44f0e..2e6e9ddf31b5a12c30ef5e8e15d44b4bcf397151 100644
--- a/src/preparser.h
+++ b/src/preparser.h
@@ -238,6 +238,14 @@ class ParserBase : public Traits {
 
     typename Traits::Type::Factory* factory() { return factory_; }
 
+    void set_consecutive_class_declaration_batch_start(int position) {
+      consecutive_class_declaration_batch_start_ = position;
+    }
+
+    int consecutive_class_declaration_batch_start() const {
+      return consecutive_class_declaration_batch_start_;
+    }
+
    private:
     // Used to assign an index to each literal that needs materialization in
     // the function.  Includes regexp literals, and boilerplate for object and
@@ -267,6 +275,9 @@ class ParserBase : public Traits {
     Scope** scope_stack_;
     Scope* outer_scope_;
     typename Traits::Type::Factory* factory_;
+    // For tracking which classes are declared consecutively. Needed for strong
+    // mode.
+    int consecutive_class_declaration_batch_start_;
 
     friend class ParserTraits;
     friend class Checkpoint;
@@ -1632,6 +1643,7 @@ class PreParser : public ParserBase<PreParserTraits> {
                             &factory);
     bool ok = true;
     int start_position = scanner()->peek_location().beg_pos;
+    top_scope.set_consecutive_class_declaration_batch_start(start_position);
     ParseStatementList(Token::EOS, &ok);
     if (stack_overflow()) return kPreParseStackOverflow;
     if (!ok) {
@@ -1784,7 +1796,8 @@ ParserBase<Traits>::FunctionState::FunctionState(
       outer_function_state_(*function_state_stack),
       scope_stack_(scope_stack),
       outer_scope_(*scope_stack),
-      factory_(factory) {
+      factory_(factory),
+      consecutive_class_declaration_batch_start_(scope->start_position()) {
   *scope_stack_ = scope;
   *function_state_stack = this;
 }
@@ -3092,6 +3105,8 @@ ParserBase<Traits>::ParseArrowFunctionLiteral(int start_pos,
 
     Expect(Token::ARROW, CHECK_OK);
 
+    function_state.set_consecutive_class_declaration_batch_start(
+        scanner()->location().beg_pos);
     if (peek() == Token::LBRACE) {
       // Multiple statement body
       Consume(Token::LBRACE);