问题是eu.timepit.refined
宏适用于文字BigDecimal
,,BigInt
https://github.com/fthomas/refined/blob/master/modules/core/shared/src/main/scala/eu/timepit/refined/macros/RefineMacro.scala#L14-L23
def impl[F[_, _], T: c.WeakTypeTag, P: c.WeakTypeTag](t: c.Expr[T])(
rt: c.Expr[RefType[F]],
v: c.Expr[Validate[T, P]]
): c.Expr[F[T, P]] = {
val tValue: T = t.tree match {
case Literal(Constant(value)) => value.asInstanceOf[T]
case BigDecimalMatcher(value) => value.asInstanceOf[T]
case BigIntMatcher(value) => value.asInstanceOf[T]
case _ => abort(Resources.refineNonCompileTimeConstant)
}
List(1, 2, 3, 4, 5)
不是文字。
对于像在运行时工作的List(1, 2, 3, 4, 5)
非文字值refineV
val v1 = List(1, 2, 3, 4, 5)
val v2 = List(1, 2, 3, 4, 5, 6)
refineV[Size[Equal[5]]](v1)
// Right(List(1, 2, 3, 4, 5))
refineV[Size[Equal[5]]](v2)
// Left(Predicate taking size(List(1, 2, 3, 4, 5, 6)) = 6 failed: Predicate failed: (6 == 5).)
幸运的是,您可以refineV
在编译时运行
object myAuto {
implicit def compileTimeRefineV[T, P](t: T): T Refined P =
macro compileTimeRefineVImpl[T, P]
def compileTimeRefineVImpl[T: c.WeakTypeTag,
P: c.WeakTypeTag](c: blackbox.Context)(t: c.Tree): c.Tree = {
import c.universe._
val pTyp = weakTypeOf[P]
val tTyp = weakTypeOf[T]
c.eval(c.Expr[Either[String, T Refined P]](c.untypecheck(
q"_root_.eu.timepit.refined.`package`.refineV[$pTyp].apply[$tTyp]($t)"
))).fold(
c.abort(c.enclosingPosition, _),
_ => q"$t.asInstanceOf[_root_.eu.timepit.refined.api.Refined[$tTyp, $pTyp]]"
)
}
}
import myAuto._ // don't import eu.timepit.refined.auto._
type Vec5 = List[Int] Refined Size[Equal[5]]
val v1: Vec5 = List(1, 2, 3, 4, 5) // compiles
// val v2: Vec5 = List(1, 2, 3, 4, 5, 6)
// Error: Predicate taking size(List(1, 2, 3, 4, 5, 6)) = 6 failed: Predicate failed: (6 == 5).
如果您只需要静态大小的集合,您可以使用shapeless.Sized
https://github.com/milessabin/shapeless/wiki/Feature-overview:-shapeless-2.0.0#collections-with-statically-known-sizes