This bug is more a channel for discussion. I ran recently into this situation and it made me ponder things a bit.

I was wondering if there are any reasons why 'main' has to be public, or if it should actually be private (for example, suppose we call it '_main').

The rationale for this is that it would make it easy to write libraries that serve both as libraries and entrypoints, without having to hide their 'main' method.

For example:

 a.dart:
  library a;
  x = 1;
  _main() => print(x);

 b.dart:
  import 'a.dart';
  y = x + 1;
  _main() => print(y);

The idea is that these programs would have no conflicts in their imports and could be run as entrypoints ("dart a.dart" prints '1', "dart b.dart" prints '2').

This sounds like a minor improvement because you could write this with 'hide' directives today:
 a.dart:
  library a;
  x = 1;
  main() => print(x);

 b.dart:
  import 'a.dart' hide main;
  y = x + 1;
  main() => print(y);

But it brings up two questions:
 - what is more appropriate: a public or private method?
 - should we support this in the future?