LensMacro

Compile-time derivation of a Lens (or Iso on full coverage) from one or more case-class accessors.

case class Person(age: Int, name: String)

val ageL = lens[Person](_.age)                // SimpleLens, complement = remaining fields NT
val asTuple = lens[Person](_.name, _.age)     // BijectionIso (full cover)

• Single-selector, partial cover → SimpleLens[S, A, XA] with XA the structural complement (gives transform / place / transfer for free).
• Multi-selector, partial cover → SimpleLens with NamedTuple focus (SELECTOR order) and NamedTuple complement (DECLARATION order among non-focused fields).
• Full cover at any arity → BijectionIso[S, S, NT, NT].

Constructor synthesis routes through Hearth's CaseClass.parse[S] + construct[Id], so parameterised / recursive types and Scala 3 enum cases (which lack .copy) work uniformly via new S(...).