Prefer const option over BorderRadius.circular

[Piinks]

For full context see flutter/flutter#91239

BorderRadius.circular is simpler, but the same BorderRadius can be created with const by using the BorderRadius.all constructor.

Examples

// Less ideal, cannot be const
BorderRadius.circular(arg);

// More verbose, but const
const BorderRadius.all(Radius.circular(arg))

[Piinks]

cc @a14n :)

[pq]

Interesting! And cool that this is covered by "Dart Code Metrics". 👍

I wonder if there's any opportunity to generalize here. Are there any other Flutter APIs with similar const at the cost of verbosity trade-offs?

/cc @Hixie @goderbauer

(Great conversation on that PR BTW. Thanks!)