[parsing] Fix maybe-assigned for loop variables.

src/parsing/preparser.cc

Index: src/parsing/preparser.cc
diff --git a/src/parsing/preparser.cc b/src/parsing/preparser.cc
index 0377a1b9d35e70ff9cb131ad061e01f7f257888f..f674b09542b40ce2c58e57825c728e693363926e 100644
--- a/src/parsing/preparser.cc
+++ b/src/parsing/preparser.cc
@@ -310,8 +310,11 @@ void PreParser::DeclareAndInitializeVariables(
     DCHECK(track_unresolved_variables_);
     for (auto variable : *(declaration->pattern.variables_)) {
       declaration_descriptor->scope->RemoveUnresolved(variable);
-      scope()->DeclareVariableName(variable->raw_name(),
-                                   declaration_descriptor->mode);
+      Variable* var = scope()->DeclareVariableName(
+          variable->raw_name(), declaration_descriptor->mode);
+      if (FLAG_preparser_scope_analysis) {
+        MarkLoopVariableAsAssigned(declaration_descriptor->scope, var);
+      }
       if (names) {
         names->Add(variable->raw_name(), zone());
       }