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

runtime/vm/kernel_to_il.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "vm/kernel_to_il.h"
 
@@ skipping 653 matching lines @@
 
 
 void ScopeBuilder::VisitFunctionNode(FunctionNode* node) {
   List<TypeParameter>& type_parameters = node->type_parameters();
   for (intptr_t i = 0; i < type_parameters.length(); ++i) {
     VisitTypeParameter(type_parameters[i]);
   }
 
   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)

     }
   }
 
   // Do not visit the positional and named parameters, because they've
   // already been added to the scope.
   if (node->body() != NULL) {
     node->body()->AcceptStatementVisitor(this);
   }
 
   // Ensure that :await_jump_var, :await_ctx_var and :async_op are captured.
@@ skipping 5356 matching lines @@
     thread->clear_sticky_error();
     return error.raw();
   }
 }
 
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)