Make safe points in generated code invisible to the debugger

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/class_finalizer.h"
@@ skipping 949 matching lines @@
     Append(for_effect);
     if (!is_open()) {
       owner()->DeallocateTemps(owner()->temp_count());
       return;
     }
   }
 
   // Call to stub that checks whether the debugger is in single
   // step mode. This call must happen before the contexts are
   // unchained so that captured variables can be inspected.
-  // No debugger check is done in native functions.
+  // No debugger check is done in native functions or for return
+  // statements for which there is no associated source position.
   const Function& function = owner()->parsed_function()->function();
-  if (!function.is_native()) {
+  if ((node->token_pos() != Scanner::kDummyTokenIndex) &&
+      !function.is_native()) {
     AddInstruction(new DebugStepCheckInstr(node->token_pos(),
                                            PcDescriptors::kReturn));
   }
 
   Value* return_value = for_value.value();
   if (FLAG_enable_type_checks) {
     const bool is_implicit_dynamic_getter =
         (!function.is_static() &&
         ((function.kind() == RawFunction::kImplicitGetter) ||
          (function.kind() == RawFunction::kImplicitStaticFinalGetter)));
@@ skipping 3069 matching lines @@
                                   LanguageError::kError,
                                   Heap::kNew,
                                   "FlowGraphBuilder Bailout: %s %s",
                                   String::Handle(function.name()).ToCString(),
                                   reason));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart