add eu.timepit.refined.W for Scala 3

modules/core/shared/src/main/scala-3.0+/eu/timepit/refined/W.scala

@@ -0,0 +1,87 @@
+package eu.timepit.refined
+
+import scala.annotation.compileTimeOnly
+import scala.compiletime.ops.int
+import scala.compiletime.ops.long
+import scala.compiletime.ops.string.CharAt
+import scala.compiletime.ops.string.Length
+import scala.compiletime.ops.string.Substring
+import scala.language.dynamics
+
+@compileTimeOnly("Illegal reference")
+object W extends Dynamic {
+  type StringTail[A <: String] = Substring[A, 1, Length[A]]
+
+  type StringLast[A <: String] = CharAt[A, int.-[Length[A], 1]]
+
+  type Literal[A <: String] = CharAt[A, 0] match {
+    case '"' =>
+      // String
+      StringLast[A] match {
+        case '"' =>
+          Substring[A, 1, int.-[Length[A], 1]]
+      }
+    case '\'' =>
+      // Char
+      CharAt[A, 2] match {
+        case '\'' =>
+          Length[A] match {
+            case 3 =>
+              CharAt[A, 1]
+          }
+      }
+    case _ =>
+      // TODO support another types
+      // e.g. Double, Float
+      StringLast[A] match {
+        case 'L' =>
+          // Long
+          StringToLong[Substring[A, 0, int.-[Length[A], 1]]]
+        case _ =>
+          // Int
+          long.ToInt[StringToLong[A]]
+      }
+  }
+
+  type StringToLong[Input <: String] <: Long = CharAt[Input, 0] match {
+    case '-' =>
+      long.Negate[Loop[StringTail[Input], 0L]]
+    case _ =>
+      Loop[Input, 0L]
+  }
+
+  type CharToLong[C <: Char] <: Long = C match {
+    case '0' => 0L
+    case '1' => 1L
+    case '2' => 2L
+    case '3' => 3L
+    case '4' => 4L
+    case '5' => 5L
+    case '6' => 6L
+    case '7' => 7L
+    case '8' => 8L
+    case '9' => 9L
+  }
+
+  type Loop[Input <: String, Acc <: Long] <: Long = Length[Input] match {
+    case 0 =>
+      Acc
+    case _ =>
+      Loop[
+        StringTail[Input],
+        long.+[
+          long.*[10L, Acc],
+          CharToLong[
+            CharAt[Input, 0]
+          ]
+        ]
+      ]
+  }
+
+  def selectDynamic(
+      selector: String
+  ): None.type { type T = Literal[selector.type] } =
+    None.asInstanceOf[
+      None.type { type T = Literal[selector.type] }
+    ]
+}