Raise SyntaxError on let [ starting an ExpressionStatement

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 9809071d4789a58da84abfd32420688e0fd2a038..2c97fe822cfa8524ddea5ba2e54683fb16acb8a1 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -4996,6 +4996,12 @@ ParserBase<Impl>::ParseExpressionOrLabelledStatement(
       ReportUnexpectedToken(Next());
       *ok = false;
       return impl()->NullStatement();
+    case Token::LET:
+      if (PeekAhead() != Token::LBRACK) break;
+      impl()->ReportMessageAt(scanner()->peek_location(),
+                              MessageTemplate::kUnexpectedTokenLetLBrack);
+      *ok = false;
+      return impl()->NullStatement();
     default:
       break;
   }