Typdefs are ignored when running `extract`

[mosuem]

With this repository https://github.com/mosuem/typedef_export, running dart pub global run dart_apitool:main extract --input . prints

The following declarations do not have an entry point (did you miss to export them?):
  _A
    Usage(s):
    - typedef_export_base.dart::Awesome::isAwesome
    - typedef_export_base.dart::A

This is incorrect, as the typedef A is exported, which should be enough.