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Use wildcard type instead of whitebox cast in IsoFields #1574

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Use wildcard type instead of whitebox cast in IsoFields #1574

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15 changes: 5 additions & 10 deletions core/shared/src/main/scala-3/monocle/internal/IsoFields.scala
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Original file line number Diff line number Diff line change
@@ -1,28 +1,23 @@
package monocle.internal

import monocle.Iso
import monocle.{Iso, PIso}
import scala.quoted.{quotes, Expr, Quotes, Type}
import scala.deriving.Mirror

object IsoFields {
transparent inline def apply[S <: Product](using mirror: Mirror.ProductOf[S]): Iso[S, Tuple] =
transparent inline def apply[S <: Product](using mirror: Mirror.ProductOf[S]): PIso[S, S, ? <: Tuple, ? <: Tuple] =
${ IsoFieldsImpl.apply[S]('mirror) }
}

private[monocle] object IsoFieldsImpl {

def apply[S <: Product](mirror: Expr[Mirror.ProductOf[S]])(using Quotes, Type[S]): Expr[Iso[S, Tuple]] = {

def whitebox[A <: Tuple](e: Expr[Iso[S, A]]): Expr[Iso[S, Tuple]] =
e.asInstanceOf[Expr[Iso[S, Tuple]]]

def apply[S <: Product](mirror: Expr[Mirror.ProductOf[S]])(using Quotes, Type[S]): Expr[PIso[S, S, ? <: Tuple, ? <: Tuple]] =
mirror match {
case '{ type a <: Tuple; $m: Mirror.ProductOf[S] { type MirroredElemTypes = `a` } } =>
whitebox('{
'{
val f: S => a = Tuple.fromProductTyped(_)(using $m)
val g: a => S = $m.fromProduct(_)
Iso[S, a](f)(g)
})
}
}
}
}
2 changes: 1 addition & 1 deletion core/shared/src/main/scala-3/monocle/syntax/MacroSyntax.scala
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Expand Up @@ -13,7 +13,7 @@ trait MacroSyntax {
* Case classes with 0 fields will correspond with `EmptyTuple`, 1 with `Tuple1[field type]`, 2 or more with a
* tuple of all field types in the same order as the fields themselves.
*/
transparent inline def fields[S <: Product: Mirror.ProductOf]: Iso[S, Tuple] =
transparent inline def fields[S <: Product: Mirror.ProductOf]: PIso[S, S, ? <: Tuple, ? <: Tuple] =
IsoFields[S]
}

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