The `toString` logic in `mini_types.dart` is improved in the following ways:
- The `toString` representation of the "unknown" type is changed from
`?` to `_`, to match the behavior of the mini_types parser.
- Logic for applying parentheses is simplified and moved into the
function `_parenthesizeIf`.
- The boolean `allowSuffixes` (which was not well documented, and
poorly named) is replaced with a boolean `parenthesizeIfComplex`,
and documentation is added to clarify its behavior.
- Unit tests of `toString` are added to `mini_types_test.dart`.
Change-Id: I251e137369b5880017022be2514f00975a511e72
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/365660
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Paul Berry
b64c9ee5e9