Track the 'awaiter return' call stack use it to detect uncaught exceptions in async functions

runtime/vm/flow_graph.h

 // Copyright (c) 2013, 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.
 
 #ifndef RUNTIME_VM_FLOW_GRAPH_H_
 #define RUNTIME_VM_FLOW_GRAPH_H_
 
 #include "vm/bit_vector.h"
 #include "vm/growable_array.h"
 #include "vm/hash_map.h"
@@ skipping 267 matching lines @@
   // Remove environments from the instructions which do not deoptimize.
   void EliminateEnvironments();
 
   bool IsReceiver(Definition* def) const;
 
   // Optimize (a << b) & c pattern: if c is a positive Smi or zero, then the
   // shift can be a truncating Smi shift-left and result is always Smi.
   // Merge instructions (only per basic-block).
   void TryOptimizePatterns();
 
+  ZoneGrowableArray<TokenPosition>* await_token_positions() const {
+    return await_token_positions_;
+  }
+
+  void set_await_token_positions(
+      ZoneGrowableArray<TokenPosition>* await_token_positions) {
+    await_token_positions_ = await_token_positions;
+  }
+
   // Replaces uses that are dominated by dom of 'def' with 'other'.
   // Note: uses that occur at instruction dom itself are not dominated by it.
   static void RenameDominatedUses(Definition* def,
                                   Instruction* dom,
                                   Definition* other);
 
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
   friend class ConstantPropagator;
@@ skipping 81 matching lines @@
   ConstantInstr* constant_null_;
   ConstantInstr* constant_dead_;
   ConstantInstr* constant_empty_context_;
 
   BlockEffects* block_effects_;
   bool licm_allowed_;
 
   ZoneGrowableArray<BlockEntryInstr*>* loop_headers_;
   ZoneGrowableArray<BitVector*>* loop_invariant_loads_;
   ZoneGrowableArray<const LibraryPrefix*>* deferred_prefixes_;
+  ZoneGrowableArray<TokenPosition>* await_token_positions_;
   DirectChainedHashMap<ConstantPoolTrait> constant_instr_pool_;
   BitVector* captured_parameters_;
 
   intptr_t inlining_id_;
 };
 
 
 class LivenessAnalysis : public ValueObject {
  public:
   LivenessAnalysis(intptr_t variable_count,
@@ skipping 134 matching lines @@
 
  private:
   GrowableArray<Definition*> defs_;
   BitVector* contains_vector_;
 };
 
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_FLOW_GRAPH_H_