What falls out in the current implementation -- i.e., from consistently applying privacy to identifiers -- is that the library's name is private wrt itself. So,

library _foo;
import 'dart:mirrors';
class C {}
main() {
  var thisLibrary = reflectClass(C).owner;
  var a = #_foo;
  var b = thisLibrary.simpleName;
  var c = MirrorSystem.getSymbol('_foo', thisLibrary);
  print(a == b); // true
  print(b == c); // true
}

Banning private library names seems more tractable than declaring some identifiers starting with underscore to not be private. This might be small enough for TC52 to address.

It seems to me that the most consistent thing is that all names in a compilation unit are mangled the same way.

The whole foundation for our privacy mechanism was that it could be implemented by mangling during lexical analysis.

Set owner to @gbracha.
Removed Area-Language label.

Actually, I just found this in the specification:
"Privacy applies only to declarations within a library, not to library declarations themselves."
(which probably also applies to "part of" declarations), so I guess library names should not be mangled.

That means that you can have:
  library _foo; // Not private.
and no good way to create a symbol for the name.

It would perhaps be better if the mirror system did not use symbols for library names at all, and just used strings instead.

Also, the use of Symbol for qualified names introduces similar problems.