Private names are not exported, not even if the library imports itself

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 39457)
+++ runtime/vm/parser.cc	(working copy)
@@ -1522,7 +1522,7 @@
   }
 
   if (params->has_optional_named_parameters &&
-      (parameter.name->CharAt(0) == '_')) {
+      (parameter.name->CharAt(0) == Library::kPrivateIdentifierStart)) {
     ReportError(parameter.name_pos, "named parameter must not be private");
   }
 
@@ -9553,6 +9553,15 @@
                                            const String& ident) {
   TRACE_PARSER("ResolveIdentInPrefixScope");
   HANDLESCOPE(I);
+  if (ident.CharAt(0) == Library::kPrivateIdentifierStart) {
+    // Private names are not exported by libraries. The name mangling
+    // of private names with a library-specific suffix usually ensures
+    // that _x in library A is not found when looked up from library B.
+    // In the pathological case where a library includes itself with
+    // a prefix, the name mangling would not help in hiding the private
+    // name, so we need to explicitly reject private names here.
+    return NULL;
+  }
   Object& obj = Object::Handle(I);
   if (prefix.is_loaded()) {
     obj = prefix.LookupObject(ident);