False positive for unnecessary_parenthesis

[JaffaKetchup]

Describe the issue
Given a class with a non-nullable field, and a constructor with a nullable equivalent, and without a default value (because the wanted default would be non-const), an initialiser list with a default is required to prevent an error.
However, if this relies around a function callback, such as type void Function(), defining a default function with the arrow syntax is impossible without producing either an error or a lint warning.

To Reproduce

// Valid, but false positive lint
class Example {
  final bool Function() e;

  Example({
    bool Function()? e,
  }) : e = e ??= (() => true);
}

// Throws error
class Example2 {
  final bool Function() e;

  Example2({
    bool Function()? e,
  }) : e = e ??= () => true;
}

Expected behavior
Unnecessary parenthesis lint should not be thrown, as the brackets are necessary.

Additional context
The suggested fix that removes the brackets causes the issue shown in image 2 & 3.

[srawlins]

Thanks for filing an issue. Please provide a minimal, complete, reproduction (not screenshots).

[JaffaKetchup]

@srawlins Of course, apologies. I've updated the original post.

[srawlins]

Great catch! I'll note that I think the ??= should be ??. But I think still a valid bug.

[srawlins]

Fixed by https://dart-review.googlesource.com/c/sdk/+/352965