Resolve null safety migration TODOS (#135)

- Switch from `StackTrace.fromString` to `AsyncError.defaultStackTrace`.
- Remove a TODO about non-nullable `StackTrace`, by the time we merged
  null safety the type was already non-nullable and the TODO was stale.

Style tweak - remove the argument names from a Function type that are
redundant against their type names.
2 files changed
tree: dca3dfafe2b190b6a74c54d6cd74863bac5bedad
  1. lib/
  2. test/
  3. .gitignore
  4. .test_config
  5. .travis.yml
  6. AUTHORS
  7. CHANGELOG.md
  8. CONTRIBUTING.md
  9. LICENSE
  10. README.md
  11. analysis_options.yaml
  12. pubspec.yaml
README.md

Contains utility classes in the style of dart:async to work with asynchronous computations.