VM: [Kernel] Ensure we don't capture :stack_trace variable in yielding functions

runtime/vm/kernel_to_il.cc

Index: runtime/vm/kernel_to_il.cc
diff --git a/runtime/vm/kernel_to_il.cc b/runtime/vm/kernel_to_il.cc
index 15962431289fd594b1375d928e4076e0c66bf967..11a84e2ffe6f9bbc55a57a82685f8b6ff037a375 100644
--- a/runtime/vm/kernel_to_il.cc
+++ b/runtime/vm/kernel_to_il.cc
@@ -671,10 +671,11 @@ void ScopeBuilder::VisitFunctionNode(FunctionNode* node) {
 
   if (node->async_marker() == FunctionNode::kSyncYielding) {
     LocalScope* scope = parsed_function_->node_sequence()->scope();
+    intptr_t offset = parsed_function_->function().num_fixed_parameters();
     for (intptr_t i = 0;
          i < parsed_function_->function().NumOptionalPositionalParameters();
          i++) {
-      scope->VariableAt(i)->set_is_forced_stack();
+      scope->VariableAt(offset + i)->set_is_forced_stack();

[Florian Schneider, 2017/01/19 17:57:16]

Can we get rid of is_forced_stack?

(see the discussion a while ago about exception_var and stacktrace_var in the
kernel merge CL)

     }
   }