Debugger support for step-into async and async* functions.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 7d8c5a3f1b3abb0c1149de76c5522393bdbfefb0..79097a3243e4c09ba60f7b8eded9e2406e59e7e3 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -7252,6 +7252,18 @@ SequenceNode* Parser::CloseAsyncGeneratorFunction(const Function& closure_func,
 
   TokenPosition token_pos = TokenPosition::kNoSource;
 
+
+  // Add to AST:
+  //   :async_op = <closure>;  (containing the original body)
+  LocalVariable* async_op_var =
+      current_block_->scope->LookupVariable(Symbols::AsyncOperation(), false);
+  ClosureNode* closure_obj = new (Z) ClosureNode(
+      TokenPosition::kNoSource, closure_func, NULL, closure_body->scope());
+  StoreLocalNode* store_async_op = new (Z)
+      StoreLocalNode(TokenPosition::kNoSource, async_op_var, closure_obj);
+
+  current_block_->statements->Add(store_async_op);
+
   if (FLAG_causal_async_stacks) {
     // Add to AST:
     //   :async_stack_trace = _asyncStackTraceHelper();
@@ -7261,6 +7273,8 @@ SequenceNode* Parser::CloseAsyncGeneratorFunction(const Function& closure_func,
     ASSERT(!async_stack_trace_helper.IsNull());
     ArgumentListNode* async_stack_trace_helper_args =
         new (Z) ArgumentListNode(TokenPosition::kNoSource);
+    async_stack_trace_helper_args->Add(
+        new (Z) LoadLocalNode(TokenPosition::kNoSource, async_op_var));
     StaticCallNode* async_stack_trace_helper_call = new (Z) StaticCallNode(
         token_pos, async_stack_trace_helper, async_stack_trace_helper_args);
     LocalVariable* async_stack_trace_var =
@@ -7271,18 +7285,6 @@ SequenceNode* Parser::CloseAsyncGeneratorFunction(const Function& closure_func,
     current_block_->statements->Add(store_async_stack_trace);
   }
 
-
-  // Add to AST:
-  //   :async_op = <closure>;  (containing the original body)
-  LocalVariable* async_op_var =
-      current_block_->scope->LookupVariable(Symbols::AsyncOperation(), false);
-  ClosureNode* closure_obj = new (Z) ClosureNode(
-      TokenPosition::kNoSource, closure_func, NULL, closure_body->scope());
-  StoreLocalNode* store_async_op = new (Z)
-      StoreLocalNode(TokenPosition::kNoSource, async_op_var, closure_obj);
-
-  current_block_->statements->Add(store_async_op);
-
   // :async_then_callback = _asyncThenWrapperHelper(:async_op)
   const Function& async_then_wrapper_helper = Function::ZoneHandle(
       Z,
@@ -7495,6 +7497,8 @@ SequenceNode* Parser::CloseAsyncFunction(const Function& closure,
     ASSERT(!async_stack_trace_helper.IsNull());
     ArgumentListNode* async_stack_trace_helper_args =
         new (Z) ArgumentListNode(token_pos);
+    async_stack_trace_helper_args->Add(
+        new (Z) LoadLocalNode(token_pos, async_op_var));
     StaticCallNode* async_stack_trace_helper_call = new (Z) StaticCallNode(
         token_pos, async_stack_trace_helper, async_stack_trace_helper_args);
     LocalVariable* async_stack_trace_var =
@@ -9225,6 +9229,21 @@ AstNode* Parser::ParseAwaitForStatement(String* label_name) {
       stream_expr_pos, new (Z) LoadLocalNode(stream_expr_pos, iterator_var),
       Symbols::MoveNext(), no_args);
   OpenBlock();
+  if (FLAG_support_debugger) {
+    // Call '_asyncStarMoveNextHelper' so that the debugger can intercept and
+    // handle single stepping into a async* generator.
+    const Function& async_star_move_next_helper = Function::ZoneHandle(
+        Z, isolate()->object_store()->async_star_move_next_helper());
+    ASSERT(!async_star_move_next_helper.IsNull());
+    ArgumentListNode* async_star_move_next_helper_args =
+        new (Z) ArgumentListNode(stream_expr_pos);
+    async_star_move_next_helper_args->Add(
+        new (Z) LoadLocalNode(stream_expr_pos, stream_var));
+    StaticCallNode* async_star_move_next_helper_call =
+        new (Z) StaticCallNode(stream_expr_pos, async_star_move_next_helper,
+                               async_star_move_next_helper_args);
+    current_block_->statements->Add(async_star_move_next_helper_call);
+  }

[siva, 2017/03/23 22:37:01]

This call has to be added to the kernel side too right? Can you open an issue so
we don't forget it.

[Cutch, 2017/03/24 14:55:39]

Filed https://github.com/dart-lang/sdk/issues/29158

   AstNode* await_moveNext = new (Z) AwaitNode(
       stream_expr_pos, iterator_moveNext, saved_try_ctx, async_saved_try_ctx,
       outer_saved_try_ctx, outer_async_saved_try_ctx, current_block_->scope);