Merge pull request #21 from typelevel/bugfix/19

Fixes #19

Author: mpilquist

build.sbt

@@ -2,7 +2,7 @@ import com.typesafe.tools.mima.core._
 
 Global / onChangedBuildSource := ReloadOnSourceChanges
 
-ThisBuild / tlBaseVersion := "0.7"
+ThisBuild / tlBaseVersion := "0.8"
 
 ThisBuild / organization := "org.typelevel"
 ThisBuild / organizationName := "Typelevel"

core/shared/src/main/scala-3/org/typelevel/twiddles/Twiddles.scala

@@ -40,9 +40,7 @@ trait TwiddleSyntax[F[_]]:
   )
   implicit def toTwiddleOpTwo[B](fb: F[B]): TwiddleOpTwo[F, B] = new TwiddleOpTwo(fb)
 
-  extension [A](fa: F[A])
-    // TODO: Define *: here instead of with toTwiddleOpCons/Two methods above; doing so breaks a bunch of tests though
-    def to[B](using iso: Iso[A, B], F: Invariant[F]): F[B] = fa.imap(iso.to)(iso.from)
+  implicit def toTwiddleOpTo[A](fa: F[A]): TwiddleOpTo[F, A] = new TwiddleOpTo(fa)
 
   extension [A <: Tuple](fa: F[A])
     inline def dropUnits(using Invariant[F]): F[DropUnits[A]] =
@@ -88,3 +86,6 @@ final class TwiddleOpTwo[F[_], B](private val self: F[B]) extends AnyVal:
     ga.product(self).imap[A *: B *: EmptyTuple] { case (a, b) => a *: b *: EmptyTuple } {
       case a *: b *: EmptyTuple => (a, b)
     }
+
+final class TwiddleOpTo[F[_], A](private val self: F[A]) extends AnyVal:
+  def to[B](implicit iso: Iso[A, B], F: Invariant[F]): F[B] = self.imap(iso.to)(iso.from)

core/shared/src/test/scala/examples/Hierarchy.scala

@@ -66,4 +66,5 @@ object Hierarchy {
   def g: Encoder[Foo] = ((int: Encoder[Int]) *: string *: bool).to[Foo]
   def h = (int *: string) *: bool
   def i = (int *: string *: bool) *: bool *: bool
+  def j: Codec[Foo] = (int *: string *: bool).to
 }