[strong] Class constructor bodies cannot contain "use strong" directive

src/preparser.cc

Index: src/preparser.cc
diff --git a/src/preparser.cc b/src/preparser.cc
index 7e75e78ef9c2e0753c26e6f8bf9f5303ddc02f70..48f228d97e74a2abc8e3930d59bd5b3de84883dd 100644
--- a/src/preparser.cc
+++ b/src/preparser.cc
@@ -262,6 +262,14 @@ void PreParser::ParseStatementList(int end_token, bool* ok,
       } else if (use_strong_found) {
         scope_->SetLanguageMode(static_cast<LanguageMode>(
             scope_->language_mode() | STRONG));
+        if (i::IsConstructor(function_state_->kind())) {
+          // "use strong" cannot occur in a class constructor body, to avoid
+          // unintuitive strong class object semantics.
+          PreParserTraits::ReportMessageAt(
+              token_loc, MessageTemplate::kStrongConstructorDirective);
+          *ok = false;
+          return;
+        }
       } else if (!statement.IsStringLiteral()) {
         directive_prologue = false;
       }