Can't use default Seq in CorsSettings methods

[timglauert]

Some methods in CoreSettings take a Seq, e.g. CoreSettings.withAllowedMethods. However this does not work with the default Seq that is imported from the scala package. It requires the more restrictive scala.collection.immutable.Seq which is a subclass of the default Seq.

The reason for this is that CorsSettings.scala has import scala.collection.immutable.Seq so all uses of Seq refer to the more restrictive type. Looking at the code there appears to be no benefit from this more restrictive type, so the fix is to remove the import.

[lomigmegard]

You're right that we are using the immutable Seq collection in all our APIs. This is however a design choice, as we prefer enforcing strict immutability on such public APIs.

Usually the simplest way to get an immutable Seq instance is to construct a List directly or to convert your collection to one using .toList.

Note that it's also the direction Scala is taking, as collections in 2.13 (and Scala 3) will have the immutable Seq as the new default:

• https://www.scala-lang.org/blog/2017/02/28/collections-rework.html
• https://docs.scala-lang.org/overviews/collections-2.13/overview.html