VM: Explicitly load function and context before calling a closure.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 35546)
+++ runtime/vm/object.cc	(working copy)
@@ -13848,6 +13848,10 @@
   if (cls.raw() == Object::dynamic_class() && (isolate != Dart::vm_isolate())) {
     return Object::dynamic_type();
   }
+  if (cls.raw() == Object::function_class() &&

[srdjan, 2014/04/30 15:41:58]

cls.IsFunctionClass()

[Florian Schneider, 2014/04/30 16:02:19]

This seems equivalent and consistent with the code above, so I'd rather leave it
as is.

+      (isolate != Dart::vm_isolate())) {
+    return Object::dynamic_type();

[srdjan, 2014/04/30 15:41:58]

I would like to have Regis look into this change.

[Florian Schneider, 2014/04/30 16:02:19]

Now that I look at it again, actually, this should return 
Isolate::Current()->object_store()->function_type();

The problem here is that the flow-graph propagation want to canonicalize a type
that's stored in the VM isolate heap (read-only).

This occurs because we pass a Function value around in the IL (as input operand
to closure calls). 

[Florian Schneider, 2014/04/30 16:05:24]

No, not function_type, but the type corresponding to the RawFunction VM class,
not the Dart class.

[regis, 2014/04/30 16:46:39]

I fail to see what problem you are trying to solve here.
Why do you need a canonical Function type across all isolates?

+  }
   // Fast canonical lookup/registry for simple types.
   if ((cls.NumTypeArguments() == 0) && !cls.IsSignatureClass()) {
     type = cls.CanonicalType();