com.eed3si9n.manifesto.Derivation.scala Maven / Gradle / Ivy

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Manifesto is a Scala 3 reimplementation of Manifest

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package com.eed3si9n.manifesto

import scala.reflect.TypeTest
import scala.quoted.*

// https://github.com/scala/scala3/blob/3.5.1/compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala#L1774

object Derivation:
  inline def derived[A1]: Manifesto[A1] = ${ derivedMacro[A1] }
  def derivedMacro[A1: Type](using ctx: Quotes): Expr[Manifesto[A1]] =
    import ctx.reflect.*
    val tpe = Type.of[A1]
    def maybeApplied(repr: TypeRepr)(using TypeTest[TypeRepr, AppliedType]) = repr match
      case a @ AppliedType(con, args) => Some(a)
      case _                          => None
    def mkManifesto[A2: Type](
        typeCon0: String,
        args0: List[Expr[Manifesto[?]]],
        isSingleton0: Boolean,
    ): Expr[Manifesto[A2]] =
      '{
        new Manifesto[A2]:
          override def typeCon: String = ${ Expr(typeCon0) }
          override def typeArguments: List[Manifesto[?]] = List(${ Varargs(args0) }: _*)
          override def isSingleton: Boolean = ${ Expr(isSingleton0) }
      }
    def fromTypeRepr[A2: Type](repr: TypeRepr): Expr[Manifesto[A2]] =
      val show0 = repr.show(using Printer.TypeReprCode)
      val show1 =
        if repr.isSingleton then s"$show0.type"
        else if show0 == "scala.Predef.String" then "java.lang.String"
        else show0
      mkManifesto[A2](show1, Nil, repr.isSingleton)
    def fromTypeRepr2[A2: Type](
        repr: TypeRepr,
        con: TypeRepr,
        args: List[TypeRepr],
    ): Expr[Manifesto[A2]] =
      val isSingleton0 = repr.isSingleton
      val con0 = con.show(using Printer.TypeReprCode)
      val args0 = args.map: (arg) =>
        arg.asType match
          case '[a] =>
            maybeApplied(arg) match
              case Some(AppliedType(con, args)) => fromTypeRepr2[a](arg, con, args)
              case _                            => fromTypeRepr[a](arg)
      mkManifesto[A2](con0, args0, isSingleton0)
    val repr = TypeRepr.of[A1]
    maybeApplied(repr) match
      case Some(AppliedType(con, args)) => fromTypeRepr2[A1](repr, con, args)
      case _                            => fromTypeRepr[A1](repr)
end Derivation