Add experimental NamedTuple copyFrom method

library/src/scala/NamedTuple.scala

@@ -1,5 +1,8 @@
 package scala
 import compiletime.ops.boolean.*
+import compiletime.ops.int.*
+import scala.annotation.experimental
+import scala.annotation.implicitNotFound
 
 object NamedTuple:
 
@@ -25,10 +28,10 @@ object NamedTuple:
   extension [V <: Tuple](x: V)
     inline def withNames[N <: Tuple]: NamedTuple[N, V] = x
 
-  import NamedTupleDecomposition.{Names, DropNames}
+  import NamedTupleDecomposition.{Names, DropNames, Decompose}
   export NamedTupleDecomposition.{
-    Names, DropNames,
-    apply, size, init, head, last, tail, take, drop, splitAt, ++, map, reverse, zip, toList, toArray, toIArray
+    Names, DropNames, Decompose,
+    apply, size, init, head, last, tail, take, drop, splitAt, ++, copyFrom, map, reverse, zip, toList, toArray, toIArray
   }
 
   extension [N <: Tuple, V <: Tuple](x: NamedTuple[N, V])
@@ -116,6 +119,14 @@ object NamedTuple:
       case Names[Y] =>
         NamedTuple[Names[X], Tuple.Zip[DropNames[X], DropNames[Y]]]
 
+  @experimental
+  type Copy[X <: AnyNamedTuple, Y <: AnyNamedTuple] = (Decompose[X], Decompose[Y]) match
+    case ((nx, vx), (ny, vy)) =>
+      NamedTuple[
+        nx,
+        NamedTupleDecomposition.Copy0[nx, vx, ny, vy, EmptyTuple]
+      ]
+
   /** A type specially treated by the compiler to represent all fields of a
    *  class argument `T` as a named tuple. Or, if `T` is already a named tuple,
    *  `From[T]` is the same as `T`.
@@ -174,6 +185,18 @@ object NamedTupleDecomposition:
       : Concat[NamedTuple[N, V], NamedTuple[N2, V2]]
       = x.toTuple ++ that.toTuple
 
+    /** The named tuple consisting of all elements of this tuple, with fields replaced by those from `that`.
+     *  The field names of the update tuple of updates must all be present in this tuple, but not all fields are required.
+     */
+    @experimental
+    inline def copyFrom[N2 <: Tuple, V2 <: Tuple](that: NamedTuple[N2, V2])(using Tuple.ContainsAll[N2, N] =:= true)
+      : Copy[NamedTuple[N, V], NamedTuple[N2, V2]]
+      = scala.runtime.Tuples.copy(
+          self = x.toTuple,
+          that = that.toTuple,
+          indices = compiletime.constValueTuple[Tuple.Indices[N, N2]]
+        ).asInstanceOf[Copy[NamedTuple[N, V], NamedTuple[N2, V2]]]
+
     /** The named tuple consisting of all element values of this tuple mapped by
      *  the polymorphic mapping function `f`. The names of elements are preserved.
      *  If `x = (n1 = v1, ..., ni = vi)` then `x.map(f) = `(n1 = f(v1), ..., ni = f(vi))`.
@@ -205,10 +228,29 @@ object NamedTupleDecomposition:
 
   end extension
 
+  @experimental
+  type LookupName[X, N <: Tuple, V <: Tuple] <: Option[Any] =
+    (N, V) match
+      case (X *: _, v *: _) => Some[v]
+      case (_ *: ns, _ *: vs) => LookupName[X, ns, vs]
+      case (EmptyTuple, EmptyTuple) => None.type
+
+  @experimental
+  type Copy0[Nx <: Tuple, Vx <: Tuple, Ny <: Tuple, Vy <: Tuple, Acc <: Tuple] <: Tuple =
+    (Nx, Vx) match
+      case (nx *: nxs, vx *: vxs) => LookupName[nx, Ny, Vy] match
+        case Some[vy] => Copy0[nxs, vxs, Ny, Vy, vy *: Acc]
+        case _ => Copy0[nxs, vxs, Ny, Vy, vx *: Acc]
+      case (EmptyTuple, EmptyTuple) => Tuple.Reverse[Acc]
+
   /** The names of a named tuple, represented as a tuple of literal string values. */
   type Names[X <: AnyNamedTuple] <: Tuple = X match
     case NamedTuple[n, _] => n
 
   /** The value types of a named tuple represented as a regular tuple. */
   type DropNames[NT <: AnyNamedTuple] <: Tuple = NT match
     case NamedTuple[_, x] => x
+
+  @experimental
+  type Decompose[NT <: AnyNamedTuple] <: Tuple = NT match
+    case NamedTuple[n, x] => (n, x)

library/src/scala/Tuple.scala

@@ -3,6 +3,7 @@ package scala
 import annotation.showAsInfix
 import compiletime.*
 import compiletime.ops.int.*
+import scala.annotation.experimental
 
 /** Tuple of arbitrary arity */
 sealed trait Tuple extends Product {
@@ -281,6 +282,32 @@ object Tuple {
       case false => Disjoint[xs, Y]
     case EmptyTuple => true
 
+  @experimental
+  type ContainsAll[X <: Tuple, Y <: Tuple] <: Boolean = X match
+    case x *: xs => Contains[Y, x] match
+      case true  => ContainsAll[xs, Y]
+      case false => false
+    case EmptyTuple => true
+
+  @experimental
+  type IndexOfOptionOnto[X, N <: Tuple, Acc <: Int] <: Option[Int] = N match
+    case X *: _ => Some[Acc]
+    case _ *: ns => IndexOfOptionOnto[X, ns, S[Acc]]
+    case EmptyTuple => None.type
+
+  @experimental
+  type IndexOfOption[X, N <: Tuple] = IndexOfOptionOnto[X, N, 0]
+
+  @experimental
+  type Indices[X <: Tuple, Y <: Tuple] = IndicesOnto[X, Y, 0, EmptyTuple]
+
+  @experimental
+  type IndicesOnto[X <: Tuple, Y <: Tuple, Idx <: Int, Acc <: Tuple] <: Tuple = X match
+    case x *: xs => IndexOfOption[x, Y] match
+      case Some[i] => IndicesOnto[xs, Y, S[Idx], i *: Acc]
+      case _ => IndicesOnto[xs, Y, S[Idx], (-1 * S[Idx]) *: Acc] // no problem if Int overflow
+    case EmptyTuple => Reverse[Acc]
+
   /** Empty tuple */
   def apply(): EmptyTuple = EmptyTuple
 

library/src/scala/runtime/Tuples.scala

@@ -1,5 +1,7 @@
 package scala.runtime
 
+import scala.annotation.experimental
+
 object Tuples {
 
   inline val MaxSpecialized = 22
@@ -283,6 +285,21 @@ object Tuples {
     case self: Product => self.productArity
   }
 
+  @experimental
+  def copy(self: Tuple, that: Tuple, indices: Tuple): Tuple = indices match
+    case EmptyTuple => self
+    case _ =>
+      val is = indices.productIterator.asInstanceOf[Iterator[Int]]
+      val arr = IArray.from(
+        is.map: i =>
+          if i < 0 then
+            val i0 = Math.abs(i) - 1 // nice that it is correct even for min value
+            self.productElement(i0)
+          else
+            that.productElement(i)
+      )
+      Tuple.fromIArray(arr)
+
   // Tail for Tuple1 to Tuple22
   private def specialCaseTail(self: Tuple): Tuple = {
     (self: Any) match {

project/MiMaFilters.scala

@@ -13,6 +13,9 @@ object MiMaFilters {
         // Scala.js-only class
         ProblemFilters.exclude[FinalClassProblem]("scala.scalajs.runtime.AnonFunctionXXL"),
         ProblemFilters.exclude[DirectMissingMethodProblem]("scala.scalajs.runtime.AnonFunctionXXL.this"),
+
+        // NamedTuples copy method
+        ProblemFilters.exclude[DirectMissingMethodProblem]("scala.runtime.Tuples.copy")
       ),
 
       // Additions since last LTS

tests/neg/named-tuple-ops-copy.scala

@@ -0,0 +1,16 @@
+//> using options -experimental
+
+trait Mod
+
+given Conversion[String, Mod] = _ => new Mod {}
+
+type Foo = (name: String, mod: Mod)
+case class Foo0(name: String, mod: Mod)
+
+@main def Test =
+  val foo: Foo = (name = "foo", mod = "some_mod")
+  val foo_updated: Foo = foo.copyFrom((mod = "bar")) // error, stays as String
+
+
+  val foo0: Foo0 = Foo0(name = "foo", mod = "some_mod")
+  val foo0_updated: Foo0 = foo0.copy(mod = "bar") // ok - does the conversion

tests/run-tasty-inspector/stdlibExperimentalDefinitions.scala

@@ -105,7 +105,21 @@ val experimentalDefinitionInLibrary = Set(
   "scala.Predef$.runtimeChecked", "scala.annotation.internal.RuntimeChecked",
 
   // New feature: SIP 61 - @unroll annotation
-  "scala.annotation.unroll"
+  "scala.annotation.unroll",
+
+  // New experimental method - copyFrom in NamedTuple.scala (and supporting definitions)
+  "scala.NamedTuple$.copyFrom", "scala.NamedTuple$.Copy",
+  "scala.NamedTuple$.Decompose",
+  "scala.NamedTupleDecomposition$.Copy0",
+  "scala.NamedTupleDecomposition$.Decompose",
+  "scala.NamedTupleDecomposition$.LookupName",
+  "scala.NamedTupleDecomposition$.copyFrom",
+  "scala.Tuple$.ContainsAll",
+  "scala.Tuple$.IndexOfOption",
+  "scala.Tuple$.IndexOfOptionOnto",
+  "scala.Tuple$.Indices",
+  "scala.Tuple$.IndicesOnto",
+  "scala.runtime.Tuples$.copy",
 )
 
 

tests/run/named-tuple-ops-copy.scala

@@ -0,0 +1,29 @@
+//> using options -experimental
+
+type City = (name: String, zip: Int, pop: Int)
+type Coord = (x: Double, y: Double)
+type Labels = (x: String, y: String)
+
+@main def Test =
+  val city: City = (name = "Lausanne", zip = 1000, pop = 140000)
+  val coord: Coord = (x = 1.0, y = 0.0)
+  val labels: Labels = (x = "west", y = "north")
+
+  // first field updated
+  val coord_update = coord.copyFrom((x = 2.0))
+  val _: Coord = coord_update
+  assert(coord_update.x == 2.0 && coord_update.y == 0.0)
+
+  // last field updated
+  val city_update = city.copyFrom((pop = 150000))
+  val _: City = city_update
+  assert(city_update.name == "Lausanne" && city_update.zip == 1000 && city_update.pop == 150000)
+
+  // replace field types
+  val coord_to_labels = coord.copyFrom((x = "east", y = "south"))
+  val _: Labels = coord_to_labels
+  assert(coord_to_labels.x == "east" && coord_to_labels.y == "south")
+
+  // out of order
+  val city_update2 = city.copyFrom((pop = 150000, name = "Lausanne", zip = 1000))
+  val _: City = city_update2