Fix await transformation of function calls

runtime/vm/ast_transformer.cc

 // Copyright (c) 2014, 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/ast_transformer.h"
 
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/thread.h"
 
@@ skipping 549 matching lines @@
   // The temporary variables will be captured as a side effect of being
   // added to a scope, and the subsequent nodes that are added to the
   // preample can access them.
   for (intptr_t i = 0; i < node->num_temps(); i++) {
     async_temp_scope_->AddVariable(node->TempAt(i));
     AstNode* new_init_val = Transform(node->InitializerAt(i));
     preamble_->Add(new(Z) StoreLocalNode(node->token_pos(),
                    node->TempAt(i),
                    new_init_val));
   }
-  // The transformed LetNode does not have any temporary variables.
-  LetNode* result = new(Z) LetNode(node->token_pos());
-  for (intptr_t i = 0; i < node->nodes().length(); i++) {
-    result->AddNode(Transform(node->nodes()[i]));
+
+  // Add all expressions but the last to the preamble. We must do
+  // this because subexpressions of the awaitable expression we
+  // are currently transforming may depend on each other,
+  // e.g. await foo(a++, a++). Thus we must preserve the order of the
+  // transformed subexpressions.
+  for (intptr_t i = 0; i < node->nodes().length() - 1; i++) {
+    preamble_->Add(Transform(node->nodes()[i]));
   }
-  result_ = result;
+
+  // The last expression in the let node is the value of the node.
+  // The result of the transformed let node is this expression.
+  ASSERT(node->nodes().length() > 0);
+  const intptr_t last_node_index = node->nodes().length() - 1;
+  result_ = Transform(node->nodes()[last_node_index]);

[regis, 2015/10/05 20:33:15]

You could have used node->nodes().Last()

[hausner, 2015/10/05 21:19:43]

Good idea. Will do in a later checkin.

 }
 
 
 void AwaitTransformer::VisitThrowNode(ThrowNode* node) {
   AstNode* new_exception = Transform(node->exception());
   result_ = new(Z) ThrowNode(node->token_pos(),
                              new_exception,
                              node->stacktrace());
 }
 
 }  // namespace dart