Do not export library prefix names used in a library

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 27065)
+++ runtime/vm/object.cc	(working copy)
@@ -7693,11 +7693,12 @@
   intptr_t ignore = 0;
   // Lookup the name in the library's symbols.
   Object& obj = Object::Handle(isolate, lib.LookupEntry(name, &ignore));
-  if (obj.IsNull()) {
+  // Library prefixes are not exported.
+  if (obj.IsNull() || obj.IsLibraryPrefix()) {
     // Lookup in the re-exported symbols.
     obj = lib.LookupExport(name);

[Ivan Posva, 2013/09/03 21:56:06]

Wouldn't it be a conflict if the library is re-exporting something which
conflicts with a library prefix?

As far as I understand this will just cause us to overwrite the found library
prefix with a null from LookupExport, but it feels a bit weird.

[hausner, 2013/09/03 22:19:10]

That is part of what Gilad has to clarify for us. If a library prefix does not
belong to the exported namespace, then there can be no conflict with a
re-exported name. In other words, library L can contain a prefix P and may
re-export a class P from another library L2.

The IsLibraryPrefix() check in line 7701 below is actually redundant. We should
never get a library prefix back from lib.LookupExport().

   }
-  if (obj.IsNull() || HidesName(name)) {
+  if (obj.IsNull() || HidesName(name) || obj.IsLibraryPrefix()) {
     return Object::null();
   }
   return obj.raw();