Fix capturing variables in optimized compilations

runtime/vm/flow_graph_builder.cc

 // Copyright (c) 2012, 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 "vm/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/compiler.h"
@@ skipping 2401 matching lines @@
     ReturnDefinition(new(Z) ConstantInstr(closure));
     return;
   }
 
   const bool is_implicit = function.IsImplicitInstanceClosureFunction();
   ASSERT(is_implicit || function.IsNonImplicitClosureFunction());
   // The context scope may have already been set by the non-optimizing
   // compiler.  If it was not, set it here.
   if (function.context_scope() == ContextScope::null()) {
     ASSERT(!is_implicit);
+    ASSERT(node->scope() != NULL);
     const ContextScope& context_scope = ContextScope::ZoneHandle(
         Z, node->scope()->PreserveOuterScope(owner()->context_level()));
     ASSERT(!function.HasCode());
     ASSERT(function.context_scope() == ContextScope::null());
     function.set_context_scope(context_scope);
 
     // The closure is now properly setup, add it to the lookup table.
     // It is possible that the compiler creates more than one function
     // object for the same closure, e.g. when inlining nodes from
     // finally clauses. If we already have a function object for the
@@ skipping 2178 matching lines @@
                    Script::Handle(function.script()),
                    function.token_pos(),
                    Report::AtLocation,
                    "FlowGraphBuilder Bailout: %s %s",
                    String::Handle(function.name()).ToCString(),
                    reason);
   UNREACHABLE();
 }
 
 }  // namespace dart