Should we have an error or warning for a static method on an unnamed extension?

[natebosch]

extension on String {
  static String cannotCall() => '';
}

As far as I can tell there is no way to invoke cannotCall given this definition, so it's not useful to define it. Should we make this an error or warning?

[bwilkerson]

It can be invoked from within the extension, so I expect it won't be an error.

It's a TODO for the analyzer to detect it as dead code if it isn't being invoked.

[lrhn]

Agree. There is nothing inherently wrong with having local static helper functions in scope and used by the extension members.

It's dead code, like any other static on a private class, if it's not actually used by the containing library, and the analyzer should be able to recognize that normally.