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

runtime/vm/parser.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/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED_RUNTIME
 
 #include "lib/invocation_mirror.h"
@@ skipping 6799 matching lines @@
   LocalVariable* saved_stack_trace_var = NULL;
   SetupExceptionVariables(current_block_->scope, true, &context_var,
                           &exception_var, &stack_trace_var,
                           &saved_exception_var, &saved_stack_trace_var);
 
   // Open the try block.
   OpenBlock();
   // This is the outermost try-catch in the function.
   ASSERT(try_stack_ == NULL);
   PushTry(current_block_);
+  // Validate that we always get try index of 0.
+  ASSERT(try_stack_->try_index() == CatchClauseNode::kImplicitAsyncTryIndex);
 
   SetupSavedTryContext(context_var);
 }
 
 
 void Parser::AddSyncGenClosureParameters(ParamList* params) {
   // Create the parameter list for the body closure of a sync generator:
   // 1) Implicit closure parameter;
   // 2) Iterator
   // Add implicit closure parameter if not already present.
@@ skipping 249 matching lines @@
 void Parser::AddAsyncGeneratorVariables() {
   // Add to current block's scope:
   //   var :controller;
   // The :controller variable is used by the async generator closure to
   // store the StreamController object to which the yielded expressions
   // are added.
   //   var :async_op;
   //   var :async_then_callback;
   //   var :async_catch_error_callback;
   //   var :async_stack_trace;
+  //   var :controller_stream;
   // These variables are used to store the async generator closure containing
   // the body of the async* function. They are used by the await operator.
   LocalVariable* controller_var =
       new (Z) LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                             Symbols::Controller(), Object::dynamic_type());
   current_block_->scope->AddVariable(controller_var);
   LocalVariable* async_op_var =
       new (Z) LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                             Symbols::AsyncOperation(), Object::dynamic_type());
   current_block_->scope->AddVariable(async_op_var);
   LocalVariable* async_then_callback_var = new (Z)
       LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                     Symbols::AsyncThenCallback(), Object::dynamic_type());
   current_block_->scope->AddVariable(async_then_callback_var);
   LocalVariable* async_catch_error_callback_var = new (Z)
       LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                     Symbols::AsyncCatchErrorCallback(), Object::dynamic_type());
   current_block_->scope->AddVariable(async_catch_error_callback_var);
   LocalVariable* async_stack_trace = new (Z)
       LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
                     Symbols::AsyncStackTraceVar(), Object::dynamic_type());
   current_block_->scope->AddVariable(async_stack_trace);
+  LocalVariable* controller_stream = new (Z)
+      LocalVariable(TokenPosition::kNoSource, TokenPosition::kNoSource,
+                    Symbols::ControllerStream(), Object::dynamic_type());
+  current_block_->scope->AddVariable(controller_stream);
 }
 
 
 RawFunction* Parser::OpenAsyncGeneratorFunction(TokenPosition async_func_pos) {
   TRACE_PARSER("OpenAsyncGeneratorFunction");
   AddContinuationVariables();
   AddAsyncGeneratorVariables();
 
   Function& closure = Function::Handle(Z);
   bool is_new_closure = false;
@@ skipping 49 matching lines @@
 //   var :controller;
 //   var :await_jump_var = -1;
 //   var :await_context_var;
 //   f_async_body() {
 //     ... source code of f ...
 //   }
 //   var :async_op = f_async_body;
 //   var :async_then_callback = _asyncThenWrapperHelper(:async_op);
 //   var :async_catch_error_callback = _asyncCatchErrorWrapperHelper(:async_op);
 //   :controller = new _AsyncStarStreamController(:async_op);
-//   return :controller.stream;
+//   var :controller_stream = :controller.stream;
+//   return :controller_stream;
 // }
 SequenceNode* Parser::CloseAsyncGeneratorFunction(const Function& closure_func,
                                                   SequenceNode* closure_body) {
   TRACE_PARSER("CloseAsyncGeneratorFunction");
   ASSERT(!closure_func.IsNull());
   ASSERT(closure_body != NULL);
 
   // Explicitly reference variables of the async genenerator function from the
   // closure body in order to mark them as captured.
   LocalVariable* existing_var =
@@ skipping 10 matching lines @@
   ASSERT((existing_var != NULL) && existing_var->is_captured());
   existing_var = closure_body->scope()->LookupVariable(
       Symbols::AsyncThenCallback(), false);
   ASSERT((existing_var != NULL) && existing_var->is_captured());
   existing_var = closure_body->scope()->LookupVariable(
       Symbols::AsyncCatchErrorCallback(), false);
   ASSERT((existing_var != NULL) && existing_var->is_captured());
   existing_var = closure_body->scope()->LookupVariable(
       Symbols::AsyncStackTraceVar(), false);
   ASSERT((existing_var != NULL) && existing_var->is_captured());
+  existing_var =
+      closure_body->scope()->LookupVariable(Symbols::ControllerStream(), false);
+  ASSERT((existing_var != NULL) && existing_var->is_captured());
 
   const Library& async_lib = Library::Handle(Library::AsyncLibrary());
 
   const Class& controller_class = Class::Handle(
       Z,
       async_lib.LookupClassAllowPrivate(Symbols::_AsyncStarStreamController()));
   ASSERT(!controller_class.IsNull());
   const Function& controller_constructor = Function::ZoneHandle(
       Z, controller_class.LookupConstructorAllowPrivate(
              Symbols::_AsyncStarStreamControllerConstructor()));
@@ skipping 88 matching lines @@
   ConstructorCallNode* controller_constructor_call =
       new (Z) ConstructorCallNode(TokenPosition::kNoSource,
                                   TypeArguments::ZoneHandle(Z),
                                   controller_constructor, arguments);
   LocalVariable* controller_var =
       current_block_->scope->LookupVariable(Symbols::Controller(), false);
   StoreLocalNode* store_controller = new (Z) StoreLocalNode(
       TokenPosition::kNoSource, controller_var, controller_constructor_call);
   current_block_->statements->Add(store_controller);
 
+  // Grab :controller.stream
+  InstanceGetterNode* controller_stream = new (Z) InstanceGetterNode(
+      TokenPosition::kNoSource,
+      new (Z) LoadLocalNode(TokenPosition::kNoSource, controller_var),
+      Symbols::Stream());
+
+  // Store :controller.stream into :controller_stream inside the closure.
+  // We have to remember the stream because a new instance is generated for
+  // each getter invocation and in order to recreate the linkage, we need the
+  // awaited on instance.
+  LocalVariable* controller_stream_var =
+      current_block_->scope->LookupVariable(Symbols::ControllerStream(), false);
+  ASSERT(controller_stream_var != NULL);
+
+  StoreLocalNode* store_controller_stream = new (Z) StoreLocalNode(
+      TokenPosition::kNoSource, controller_stream_var, controller_stream);
+  current_block_->statements->Add(store_controller_stream);
+
   // return :controller.stream;
   ReturnNode* return_node = new (Z) ReturnNode(
       TokenPosition::kNoSource,
-      new (Z) InstanceGetterNode(
-          TokenPosition::kNoSource,
-          new (Z) LoadLocalNode(TokenPosition::kNoSource, controller_var),
-          Symbols::Stream()));
+      new (Z) LoadLocalNode(TokenPosition::kNoSource, controller_stream_var));
   current_block_->statements->Add(return_node);
   return CloseBlock();
 }
 
 
 void Parser::OpenAsyncGeneratorClosure() {
   async_temp_scope_ = current_block_->scope;
   OpenAsyncTryBlock();
 }
 
@@ skipping 1723 matching lines @@
   // contexts and if they have a matching token position range,
   // it can be an issue (cf. bug 26941).
   OpenBlock();
   const Block* await_for_block = current_block_;
 
   const TokenPosition stream_expr_pos = TokenPos();
   AstNode* stream_expr =
       ParseAwaitableExpr(kAllowConst, kConsumeCascades, NULL);
   ExpectToken(Token::kRPAREN);
 
+  // Create :stream to store the stream into temporarily.
+  LocalVariable* stream_var =
+      new (Z) LocalVariable(stream_expr_pos, stream_expr_pos,
+                            Symbols::ColonStream(), Object::dynamic_type());
+  current_block_->scope->AddVariable(stream_var);
+
+  // Store the stream expression into a variable.
+  StoreLocalNode* store_stream_var =
+      new (Z) StoreLocalNode(stream_expr_pos, stream_var, stream_expr);
+  current_block_->statements->Add(store_stream_var);
+
+  // Register the awaiter on the stream by invoking `_asyncStarListenHelper`.
+  const Library& async_lib = Library::Handle(Library::AsyncLibrary());
+  const Function& async_star_listen_helper = Function::ZoneHandle(
+      Z,
+      async_lib.LookupFunctionAllowPrivate(Symbols::_AsyncStarListenHelper()));
+  ASSERT(!async_star_listen_helper.IsNull());
+  LocalVariable* async_op_var =
+      current_block_->scope->LookupVariable(Symbols::AsyncOperation(), false);
+  ASSERT(async_op_var != NULL);
+  ArgumentListNode* async_star_listen_helper_args =
+      new (Z) ArgumentListNode(stream_expr_pos);
+  async_star_listen_helper_args->Add(
+      new (Z) LoadLocalNode(stream_expr_pos, stream_var));
+  async_star_listen_helper_args->Add(
+      new (Z) LoadLocalNode(stream_expr_pos, async_op_var));
+  StaticCallNode* async_star_listen_helper_call = new (Z) StaticCallNode(
+      stream_expr_pos, async_star_listen_helper, async_star_listen_helper_args);
+
+  current_block_->statements->Add(async_star_listen_helper_call);
+
   // Build creation of implicit StreamIterator.
   // var :for-in-iter = new StreamIterator(stream_expr).
   const Class& stream_iterator_cls =
       Class::ZoneHandle(Z, I->object_store()->stream_iterator_class());
   ASSERT(!stream_iterator_cls.IsNull());
   const Function& iterator_ctor = Function::ZoneHandle(
       Z,
       stream_iterator_cls.LookupFunction(Symbols::StreamIteratorConstructor()));
   ASSERT(!iterator_ctor.IsNull());
   ArgumentListNode* ctor_args = new (Z) ArgumentListNode(stream_expr_pos);
-  ctor_args->Add(stream_expr);
+  ctor_args->Add(new (Z) LoadLocalNode(stream_expr_pos, stream_var));
   ConstructorCallNode* ctor_call = new (Z) ConstructorCallNode(
       stream_expr_pos, TypeArguments::ZoneHandle(Z), iterator_ctor, ctor_args);
   const AbstractType& iterator_type = Object::dynamic_type();
   LocalVariable* iterator_var = new (Z) LocalVariable(
       stream_expr_pos, stream_expr_pos, Symbols::ForInIter(), iterator_type);
   current_block_->scope->AddVariable(iterator_var);
   AstNode* iterator_init =
       new (Z) StoreLocalNode(stream_expr_pos, iterator_var, ctor_call);
   current_block_->statements->Add(iterator_init);
 
@@ skipping 5985 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED_RUNTIME