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| 1 | +import scala.compiletime.* |
| 2 | +import scala.deriving.* |
| 3 | + |
| 4 | +object OriginalReport: |
| 5 | + sealed trait TreeValue |
| 6 | + sealed trait SubLevel extends TreeValue |
| 7 | + case class Leaf1(value: String) extends TreeValue |
| 8 | + case class Leaf2(value: Int) extends SubLevel |
| 9 | + |
| 10 | +// Variants from the initial failure in akka.event.LogEvent |
| 11 | +object FromAkkaCB: |
| 12 | + sealed trait A |
| 13 | + sealed trait B extends A |
| 14 | + sealed trait C extends A |
| 15 | + case class D() extends B, C |
| 16 | + case class E() extends C, B |
| 17 | + |
| 18 | +object FromAkkaCB2: |
| 19 | + sealed trait A |
| 20 | + sealed trait N extends A |
| 21 | + case class B() extends A |
| 22 | + case class C() extends A, N |
| 23 | + |
| 24 | +object FromAkkaCB3: |
| 25 | + sealed trait A |
| 26 | + case class B() extends A |
| 27 | + case class C() extends A |
| 28 | + class D extends C // ignored pattern: class extending a case class |
| 29 | + |
| 30 | +object FromAkkaCB4: |
| 31 | + sealed trait A |
| 32 | + sealed trait N extends A |
| 33 | + case class B() extends A |
| 34 | + case class C() extends A |
| 35 | + class D extends C, N // ignored |
| 36 | + |
| 37 | +object FromAkkaCB5: |
| 38 | + sealed trait A |
| 39 | + sealed trait N extends A |
| 40 | + case class B() extends A |
| 41 | + case class C() extends A |
| 42 | + class D extends N // ignored |
| 43 | + |
| 44 | +object Test: |
| 45 | + def main(args: Array[String]): Unit = |
| 46 | + testOriginalReport() |
| 47 | + testFromAkkaCB() |
| 48 | + testFromAkkaCB2() |
| 49 | + end main |
| 50 | + |
| 51 | + def testOriginalReport() = |
| 52 | + import OriginalReport._ |
| 53 | + val m = summon[Mirror.SumOf[TreeValue]] |
| 54 | + given Show[TreeValue] = Show.derived[TreeValue] |
| 55 | + val leaf1 = Leaf1("1") |
| 56 | + val leaf2 = Leaf2(2) |
| 57 | + |
| 58 | + assertEq(List(leaf1, leaf2).map(m.ordinal), List(1, 0)) |
| 59 | + assertShow[TreeValue](leaf1, "[1] Leaf1(value = \"1\")") |
| 60 | + assertShow[TreeValue](leaf2, "[0] [0] Leaf2(value = 2)") |
| 61 | + end testOriginalReport |
| 62 | + |
| 63 | + def testFromAkkaCB() = |
| 64 | + import FromAkkaCB._ |
| 65 | + val m = summon[Mirror.SumOf[A]] |
| 66 | + given Show[A] = Show.derived[A] |
| 67 | + val d = D() |
| 68 | + val e = E() |
| 69 | + |
| 70 | + assertEq(List(d, e).map(m.ordinal), List(0, 0)) |
| 71 | + assertShow[A](d, "[0] [0] D") |
| 72 | + assertShow[A](e, "[0] [1] E") |
| 73 | + end testFromAkkaCB |
| 74 | + |
| 75 | + def testFromAkkaCB2() = |
| 76 | + import FromAkkaCB2._ |
| 77 | + val m = summon[Mirror.SumOf[A]] |
| 78 | + val n = summon[Mirror.SumOf[N]] |
| 79 | + given Show[A] = Show.derived[A] |
| 80 | + val b = B() |
| 81 | + val c = C() |
| 82 | + |
| 83 | + assertEq(List(b, c).map(m.ordinal), List(1, 0)) |
| 84 | + assertShow[A](b, "[1] B") |
| 85 | + assertShow[A](c, "[0] [0] C") |
| 86 | + end testFromAkkaCB2 |
| 87 | + |
| 88 | + def assertEq[A](obt: A, exp: A) = assert(obt == exp, s"$obt != $exp (obtained != expected)") |
| 89 | + def assertShow[A: Show](x: A, s: String) = assertEq(Show.show(x), s) |
| 90 | +end Test |
| 91 | + |
| 92 | +trait Show[-T]: |
| 93 | + def show(x: T): String |
| 94 | + |
| 95 | +object Show: |
| 96 | + given Show[Int] with { def show(x: Int) = s"$x" } |
| 97 | + given Show[Char] with { def show(x: Char) = s"'$x'" } |
| 98 | + given Show[String] with { def show(x: String) = s"$"$x$"" } |
| 99 | + |
| 100 | + inline def show[T](x: T): String = summonInline[Show[T]].show(x) |
| 101 | + |
| 102 | + transparent inline def derived[T](implicit ev: Mirror.Of[T]): Show[T] = new { |
| 103 | + def show(x: T): String = inline ev match { |
| 104 | + case m: Mirror.ProductOf[T] => showProduct(x.asInstanceOf[Product], m) |
| 105 | + case m: Mirror.SumOf[T] => showCases[m.MirroredElemTypes](0)(x, m.ordinal(x)) |
| 106 | + } |
| 107 | + } |
| 108 | + |
| 109 | + transparent inline def showProduct[T](x: Product, m: Mirror.ProductOf[T]): String = |
| 110 | + constValue[m.MirroredLabel] + showElems[m.MirroredElemTypes, m.MirroredElemLabels](0, Nil)(x) |
| 111 | + |
| 112 | + transparent inline def showElems[Elems <: Tuple, Labels <: Tuple](n: Int, elems: List[String])(x: Product): String = |
| 113 | + inline (erasedValue[Labels], erasedValue[Elems]) match { |
| 114 | + case _: (label *: labels, elem *: elems) => |
| 115 | + val value = show(x.productElement(n).asInstanceOf[elem]) |
| 116 | + showElems[elems, labels](n + 1, s"${constValue[label]} = $value" :: elems)(x) |
| 117 | + case _: (EmptyTuple, EmptyTuple) => |
| 118 | + if elems.isEmpty then "" else elems.mkString(s"(", ", ", ")") |
| 119 | + } |
| 120 | + |
| 121 | + transparent inline def showCases[Alts <: Tuple](n: Int)(x: Any, ord: Int): String = |
| 122 | + inline erasedValue[Alts] match { |
| 123 | + case _: (alt *: alts) => |
| 124 | + if (ord == n) summonFrom { |
| 125 | + case m: Mirror.Of[`alt`] => s"[$ord] " + derived[alt](using m).show(x.asInstanceOf[alt]) |
| 126 | + } else showCases[alts](n + 1)(x, ord) |
| 127 | + case _: EmptyTuple => throw new MatchError(x) |
| 128 | + } |
| 129 | +end Show |
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