Pass closure object as first implicit argument to closure functions.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
===================================================================
--- runtime/vm/dart_api_impl.cc	(revision 14605)
+++ runtime/vm/dart_api_impl.cc	(working copy)
@@ -3936,6 +3936,11 @@
 DART_EXPORT Dart_Handle Dart_GetNativeArgument(Dart_NativeArguments args,
                                                int index) {
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
+  const bool is_instance = arguments->AreOfInstanceFunction();
+  const bool is_closure = arguments->AreOfClosureFunction();
+  if (!is_instance && is_closure) {
+    index++;  // Hide closure object.

[siva, 2012/11/07 18:56:32]

This seems to suggest that if one passed in an index of -1
to this function and the arguments are for a static implicit closure then we
will not be reporting an error.

Maybe you should increment the index after the index check
below?

[regis, 2012/11/08 18:08:30]

Good catch! Incrementing the index after the check would require the upper bound
to be adjusted prior to the check. It is actually simpler to use
Dart_GetNativeArgumentCount here.

+  }
   if (index < 0 || index >= arguments->Count()) {
     return Api::NewError(
         "%s: argument 'index' out of range. Expected 0..%d but saw %d.",
@@ -3943,13 +3948,28 @@
   }
   Isolate* isolate = arguments->isolate();
   CHECK_ISOLATE(isolate);
-  return Api::NewHandle(isolate, arguments->At(index));
+  if ((index == 0) && is_instance && is_closure) {
+    // Retrieve the receiver from the context.
+    const Context& context = Context::Handle(isolate->top_context());
+    return Api::NewHandle(isolate, context.At(0));
+  } else {
+    return Api::NewHandle(isolate, arguments->At(index));
+  }
 }
 
 
 DART_EXPORT int Dart_GetNativeArgumentCount(Dart_NativeArguments args) {
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
-  return arguments->Count();
+  int count = arguments->Count();
+  if (arguments->AreOfClosureFunction() &&
+      !arguments->AreOfInstanceFunction()) {
+    // The closure at index 0 is hidden and therefore not counted.
+    count--;
+    // In the instance closure function case, the receiver is accessed from
+    // the context and the closure at index 0 is hidden, so the apparent
+    // argument count remains unchanged.

[siva, 2012/11/07 18:56:32]

This comment should appear outside the if statement right.

[regis, 2012/11/08 18:08:30]

Done.

+  }
+  return count;
 }