Track the 'awaiter return' call stack use it to detect uncaught exceptions in async 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 2242 matching lines @@
 }
 
 
 Fragment FlowGraphBuilder::CatchBlockEntry(const Array& handler_types,
                                            intptr_t handler_index) {
   ASSERT(CurrentException()->is_captured() ==
          CurrentStackTrace()->is_captured());
   const bool should_restore_closure_context =
       CurrentException()->is_captured() || CurrentCatchContext()->is_captured();
   CatchBlockEntryInstr* entry = new (Z) CatchBlockEntryInstr(
+      TokenPosition::kNoSource,  // Token position of catch block.
+      false,                     // Not an artifact of compilation.
       AllocateBlockId(), CurrentTryIndex(), graph_entry_, handler_types,
       handler_index, *CurrentException(), *CurrentStackTrace(),
       /* needs_stacktrace = */ true, H.thread()->GetNextDeoptId(),
       should_restore_closure_context);
   graph_entry_->AddCatchEntry(entry);
   Fragment instructions(entry);
 
   // :saved_try_context_var can be captured in the context of
   // of the closure, in this case CatchBlockEntryInstr restores
   // :current_context_var to point to closure context in the
@@ skipping 4026 matching lines @@
     thread->clear_sticky_error();
     return error.raw();
   }
 }
 
 
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)