Newtype: validating tuples

[octavz]

Hi,

object KeyValue extends Newtype[(String, String)]:
  override inline def assertion = //I want to validate that first member is not empty, how do I do this ?

We should have a way to build a custom assertion for any given type.

Thank you

[nartamonov]

I think currently the design of newtypes does not supports wrapping tuples at compile-time. If we define something like:

type Both = Both.Type
object Both extends Newtype[(Int, String)]

Then compile-time construction of that newtype Both((10, "abc")) fails with:

[error]  Newtype Assertion Failed
[error] Could not validate Assertion at compile-time.
[error] Either use a literal or call "Both.unsafeWrap(Expr[Nothing](scala.Tuple2.apply[Int, String](10, "abc")))"

Macro requires we provide literal value, but we use tuple. Hope this limitation will be removed, because newtypes of tuples is helpful.

[guizmaii]

@octavz Did you try with assertCustom? See #1218 (comment)