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May 3, 2020 08:54
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| import scala.deriving._ | |
| import scala.quoted._ | |
| import scala.quoted.matching._ | |
| import scala.compiletime._ | |
| trait Show[T] { | |
| def show(x: T): String | |
| } | |
| object Show { | |
| inline def tryShow[T](x: T): String = summonInline[Show[T]].show(x) | |
| inline def showElems[Elems <: Tuple, Labels <: Tuple](n: Int)(x: Any): List[String] = | |
| inline erasedValue[Elems] match { | |
| case _: (elem *: elems1) => | |
| inline erasedValue[Labels] match { | |
| case _: (label *: labels1) => | |
| val formal = constValue[label] | |
| val actual = tryShow(productElement[elem](x, n)) | |
| s"$formal = $actual" :: showElems[elems1, labels1](n + 1)(x) | |
| } | |
| case _: Unit => | |
| Nil | |
| } | |
| inline def showCase[T](x: Any, m: Mirror.ProductOf[T]): String = { | |
| val label = constValue[m.MirroredLabel] | |
| inline m match { | |
| case m: Mirror.Singleton => label | |
| case _ => showElems[m.MirroredElemTypes, m.MirroredElemLabels](0)(x).mkString(s"$label(", ", ", ")") | |
| } | |
| } | |
| inline def showCases[Alts <: Tuple](n: Int)(x: Any, ord: Int): String = | |
| inline erasedValue[Alts] match { | |
| case _: (alt *: alts1) => | |
| if (ord == n) showCase(x, summonInline[Mirror.ProductOf[`alt`]]) | |
| else showCases[alts1](n + 1)(x, ord) | |
| case _: Unit => | |
| throw new MatchError(x) | |
| } | |
| inline def derived[T]: Show[T] = | |
| summonFrom { | |
| case ev: Mirror.Of[T] => | |
| inline ev match { | |
| case m: Mirror.SumOf[T] => | |
| new Show[T] { | |
| def show(x: T): String = { | |
| val ord = m.ordinal(x) | |
| showCases[m.MirroredElemTypes](0)(x, ord) | |
| } | |
| } | |
| case m: Mirror.ProductOf[T] => | |
| new Show[T] { | |
| def show(x: T): String = { | |
| showCase(x, m) | |
| } | |
| } | |
| } | |
| } | |
| implicit object IntShow extends Show[Int] { | |
| def show(x: Int): String = x.toString | |
| } | |
| implicit object StringShow extends Show[String] { | |
| def show(x: String): String = x | |
| } | |
| // implicit object BooleanShow extends Show[Boolean] { | |
| // def show(x: Boolean): String = x.toString | |
| // } | |
| } | |
| @main def showTest() = { | |
| import Show._ | |
| case class Address(street: String, a: Boolean) | |
| case class Person(name: String, address: Address) | |
| implicit inline def showGen[T]: Show[T] = Show.derived[T] | |
| println(showGen[Address].show(Address("a", true))) | |
| } |
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