Await always waits

runtime/vm/ast.h

 // 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.
 
 #ifndef VM_AST_H_
 #define VM_AST_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
@@ skipping 152 matching lines @@
   DECLARE_COMMON_NODE_FUNCTIONS(AwaitNode);
 
  private:
   AstNode* expr_;
 
   DISALLOW_COPY_AND_ASSIGN(AwaitNode);
 };
 
 
 // AwaitMarker nodes are used to generate markers that the FlowGraphBuilder
-// relies on. They can occur in two kinds:
-// 1) kNewContinuationState: A marker indicating that a new await state needs to
-//    be added to a function preamble. This type also triggers storing of the
-//    current context.
-// 2) kTargetForContinuation: A marker indicating an entry point for the most
-//    recent generated state.
+// relies on. A marker indicates that a new await state needs to be
+// added to a function preamble. This type also triggers storing of the
+// current context.
 //
-// In general it is expected (ASSERT) that the different kinds of markers reach
-// the FlowGraphBuilder in alternating order. That is:
-//   <new state> -> <other nodes> -> <target> -> <other nodes> ->
-//   <new state> -> ...
+// It is expected (ASSERT) that an AwaitMarker is followed by
+// a return node of kind kContinuationTarget. That is:
+//   <AwaitMarker> -> <other nodes> -> <kContinuationTarget> -> <other nodes> ->
+//   <AwaitMarker> -> ...
 class AwaitMarkerNode : public AstNode {
  public:
-  enum MarkerType {
-    kNewContinuationState,
-    kTargetForContinuation,
-  };
-
-  explicit AwaitMarkerNode(MarkerType marker_type)
-    : AstNode(Scanner::kNoSourcePos),
-      marker_type_(marker_type) { }
+  AwaitMarkerNode() : AstNode(Scanner::kNoSourcePos) { }
 
   void VisitChildren(AstNodeVisitor* visitor) const { }
 
-  MarkerType marker_type() const {
-    return marker_type_;
-  }
-
   LocalScope* scope() const { return scope_; }
   void set_scope(LocalScope* scope) { scope_ = scope; }
 
   DECLARE_COMMON_NODE_FUNCTIONS(AwaitMarkerNode);
 
  private:
-  MarkerType marker_type_;
   LocalScope* scope_;
 
   DISALLOW_COPY_AND_ASSIGN(AwaitMarkerNode);
 };
 
 
 class SequenceNode : public AstNode {
  public:
   SequenceNode(intptr_t token_pos, LocalScope* scope)
     : AstNode(token_pos),
@@ skipping 354 matching lines @@
 
   DECLARE_COMMON_NODE_FUNCTIONS(PrimaryNode);
 
  private:
   const Object& primary_;
   bool is_deferred_reference_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PrimaryNode);
 };
 
-// Return nodes can be of different types:
-// * A regular return node that in the case of async functions gets replaced
-//   with appropriate completer calls. This kind is generated by dart code.
-// * A continuation return that just returns from a function. This kind is
-//   generated by AST transformers.
+// In asynchronous code that gets suspeded and resumed, return nodes
+// can be of different types:
+// * A regular return node that in the case of async functions
+//    gets replaced with appropriate completer calls. (kRegular)
+// * A continuation return that just returns from a function, without
+//   completing the Future. (kContinuation)
+// * A continuation return followed by a continuation target, i.e. the
+//   location at which the closure resumes the next time it gets invoked.
+//   (kContinuationTarget).
+// In synchronous functions, return nodes are always of type'kRegular'
 class ReturnNode : public AstNode {
  public:
   enum ReturnType {
     kRegular,
     kContinuation,
+    kContinuationTarget
   };
 
   // Return from a void function returns the null object.
   explicit ReturnNode(intptr_t token_pos)
       : AstNode(token_pos),
         value_(new LiteralNode(token_pos, Instance::ZoneHandle())),
         inlined_finally_list_(),
         return_type_(kRegular) { }
   // Return from a non-void function.
   ReturnNode(intptr_t token_pos,
@@ skipping 1311 matching lines @@
   const intptr_t try_index_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(InlinedFinallyNode);
 };
 
 }  // namespace dart
 
 #undef DECLARE_COMMON_NODE_FUNCTIONS
 
 #endif  // VM_AST_H_