Incorporate constness into inferred interfaces

src/interface.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 106 matching lines @@
 
 
 void Interface::Unify(Interface* that, Zone* zone, bool* ok) {
   if (this->forward_) return this->Chase()->Unify(that, zone, ok);
   if (that->forward_) return this->Unify(that->Chase(), zone, ok);
   ASSERT(this->forward_ == NULL);
   ASSERT(that->forward_ == NULL);
 
   *ok = true;
   if (this == that) return;
-  if (this->IsValue()) return that->MakeValue(ok);
-  if (that->IsValue()) return this->MakeValue(ok);
+  if (this->IsValue()) {
+    that->MakeValue(ok);
+    if (*ok && this->IsConst()) that->MakeConst(ok);
+    return;
+  }
+  if (that->IsValue()) {
+    this->MakeValue(ok);
+    if (*ok && that->IsConst()) this->MakeConst(ok);
+    return;
+  }
 
 #ifdef DEBUG
   if (FLAG_print_interface_details) {
     PrintF("%*s# Unifying...\n", Nesting::current(), "");
     PrintF("%*sthis = ", Nesting::current(), "");
     this->Print(Nesting::current());
     PrintF("%*sthat = ", Nesting::current(), "");
     that->Print(Nesting::current());
   }
 #endif
@@ skipping 68 matching lines @@
 
   if (FLAG_print_interface_details) {
     PrintF("%p", static_cast<void*>(this));
     for (Interface* link = this->forward_; link != NULL; link = link->forward_)
       PrintF("->%p", static_cast<void*>(link));
     PrintF(" ");
   }
 
   if (IsUnknown()) {
     PrintF("unknown\n");
+  } else if (IsConst()) {
+    PrintF("const\n");
   } else if (IsValue()) {
     PrintF("value\n");
   } else if (IsModule()) {
     PrintF("module %s{", IsFrozen() ? "" : "(unresolved) ");
     ZoneHashMap* map = Chase()->exports_;
     if (map == NULL || map->occupancy() == 0) {
       PrintF("}\n");
     } else if (n < 0 || n0 >= 2 * FLAG_print_interface_depth) {
       // Avoid infinite recursion on cyclic types.
       PrintF("...}\n");
     } else {
       PrintF("\n");
       for (ZoneHashMap::Entry* p = map->Start(); p != NULL; p = map->Next(p)) {
         String* name = *static_cast<String**>(p->key);
         Interface* interface = static_cast<Interface*>(p->value);
         PrintF("%*s%s : ", n0 + 2, "", name->ToAsciiArray());
         interface->Print(n0 + 2);
       }
       PrintF("%*s}\n", n0, "");
     }
   }
 }
 #endif
 
 } }  // namespace v8::internal