Merge pull request #14414 from dotty-staging/add-experimental-tupled-functions

Add experimental TupledFunction

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -884,6 +884,10 @@ class Definitions {
     lazy val RuntimeTuples_isInstanceOfEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfEmptyTuple")
     lazy val RuntimeTuples_isInstanceOfNonEmptyTuple: Symbol = RuntimeTuplesModule.requiredMethod("isInstanceOfNonEmptyTuple")
 
+  @tu lazy val TupledFunctionTypeRef: TypeRef = requiredClassRef("scala.util.TupledFunction")
+  def TupledFunctionClass(using Context): ClassSymbol = TupledFunctionTypeRef.symbol.asClass
+  def RuntimeTupleFunctionsModule(using Context): Symbol = requiredModule("scala.runtime.TupledFunctions")
+
   // Annotation base classes
   @tu lazy val AnnotationClass: ClassSymbol = requiredClass("scala.annotation.Annotation")
   @tu lazy val ClassfileAnnotationClass: ClassSymbol = requiredClass("scala.annotation.ClassfileAnnotation")

compiler/src/dotty/tools/dotc/typer/Synthesizer.scala

@@ -78,6 +78,50 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
     }
   end synthesizedTypeTest
 
+  val synthesizedTupleFunction: SpecialHandler = (formal, span) =>
+    formal match
+      case AppliedType(_, funArgs @ fun :: tupled :: Nil) =>
+        def functionTypeEqual(baseFun: Type, actualArgs: List[Type],
+            actualRet: Type, expected: Type) =
+          expected =:= defn.FunctionOf(actualArgs, actualRet,
+            defn.isContextFunctionType(baseFun), defn.isErasedFunctionType(baseFun))
+        val arity: Int =
+          if defn.isErasedFunctionType(fun) || defn.isErasedFunctionType(fun) then -1 // TODO support?
+          else if defn.isFunctionType(fun) then
+            // TupledFunction[(...) => R, ?]
+            fun.dropDependentRefinement.dealias.argInfos match
+              case funArgs :+ funRet
+              if functionTypeEqual(fun, defn.tupleType(funArgs) :: Nil, funRet, tupled) =>
+                // TupledFunction[(...funArgs...) => funRet, ?]
+                funArgs.size
+              case _ => -1
+          else if defn.isFunctionType(tupled) then
+            // TupledFunction[?, (...) => R]
+            tupled.dropDependentRefinement.dealias.argInfos match
+              case tupledArgs :: funRet :: Nil =>
+                defn.tupleTypes(tupledArgs.dealias) match
+                  case Some(funArgs) if functionTypeEqual(tupled, funArgs, funRet, fun) =>
+                    // TupledFunction[?, ((...funArgs...)) => funRet]
+                    funArgs.size
+                  case _ => -1
+              case _ => -1
+          else
+            // TupledFunction[?, ?]
+            -1
+        if arity == -1 then
+          EmptyTree
+        else if arity <= Definitions.MaxImplementedFunctionArity then
+          ref(defn.RuntimeTupleFunctionsModule)
+            .select(s"tupledFunction$arity".toTermName)
+            .appliedToTypes(funArgs)
+        else
+          ref(defn.RuntimeTupleFunctionsModule)
+            .select("tupledFunctionXXL".toTermName)
+            .appliedToTypes(funArgs)
+      case _ =>
+        EmptyTree
+  end synthesizedTupleFunction
+
   /** If `formal` is of the form CanEqual[T, U], try to synthesize an
     *  `CanEqual.canEqualAny[T, U]` as solution.
     */
@@ -489,6 +533,7 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
     defn.TypeTestClass        -> synthesizedTypeTest,
     defn.CanEqualClass        -> synthesizedCanEqual,
     defn.ValueOfClass         -> synthesizedValueOf,
+    defn.TupledFunctionClass  -> synthesizedTupleFunction,
     defn.Mirror_ProductClass  -> synthesizedProductMirror,
     defn.Mirror_SumClass      -> synthesizedSumMirror,
     defn.MirrorClass          -> synthesizedMirror,

docs/_docs/reference/experimental/tupled-function.md

@@ -0,0 +1,82 @@
+---
+layout: doc-page
+title: "Tupled Function"
+---
+
+Tupled Function
+----------------------
+
+With functions bounded to arities up to 22 it was possible to generalize some operation on all function types using overloading.
+Now that we have functions and tuples generalized to [arities above 22](../dropped-features/limit22.md) overloading is not an option anymore.
+The type class `TupleFunction` provides a way to abstract directly over a function of any arity converting it to an equivalent function that receives all arguments in a single tuple.
+
+```scala
+/** Type class relating a `FunctionN[..., R]` with an equivalent tupled function `Function1[TupleN[...], R]`
+ *
+ *  @tparam F a function type
+ *  @tparam G a tupled function type (function of arity 1 receiving a tuple as argument)
+ */
+@implicitNotFound("${F} cannot be tupled as ${G}")
+sealed trait TupledFunction[F, G] {
+  def tupled(f: F): G
+  def untupled(g: G): F
+}
+```
+
+The compiler will synthesize an instance of `TupledFunction[F, G]` if:
+
+* `F` is a function type of arity `N`
+* `G` is a function with a single tuple argument of size `N` and its types are equal to the arguments of `F`
+* The return type of `F` is equal to the return type of `G`
+* `F` and `G` are the same sort of function (both are `(...) => R` or both are `(...) ?=> R`)
+* If only one of `F` or `G` is instantiated the second one is inferred.
+
+Examples
+--------
+`TupledFunction` can be used to generalize the `Function1.tupled`, ... `Function22.tupled` methods to functions of any arities.
+The following defines `tupled` as [extension method](../contextual/extension-methods.html) ([full example](https://github.com/lampepfl/dotty/blob/main/tests/run/tupled-function-tupled.scala)).
+
+```scala
+/** Creates a tupled version of this function: instead of N arguments,
+ *  it accepts a single [[scala.Tuple]] with N elements as argument.
+ *
+ *  @tparam F the function type
+ *  @tparam Args the tuple type with the same types as the function arguments of F
+ *  @tparam R the return type of F
+ */
+extension [F, Args <: Tuple, R](f: F)
+  def tupled(using tf: TupledFunction[F, Args => R]): Args => R = tf.tupled(f)
+```
+
+`TupledFunction` can be used to generalize the `Function.untupled` to a function of any arities ([full example](https://github.com/lampepfl/dotty/blob/main/tests/run/tupled-function-untupled.scala))
+
+```scala
+/** Creates an untupled version of this function: instead of a single argument of type [[scala.Tuple]] with N elements,
+ *  it accepts N arguments.
+ *
+ *  This is a generalization of [[scala.Function.untupled]] that work on functions of any arity
+ *
+ *  @tparam F the function type
+ *  @tparam Args the tuple type with the same types as the function arguments of F
+ *  @tparam R the return type of F
+ */
+extension [F, Args <: Tuple, R](f: Args => R)
+  def untupled(using tf: TupledFunction[F, Args => R]): F = tf.untupled(f)
+```
+
+`TupledFunction` can also be used to generalize the [`Tuple1.compose`](https://github.com/lampepfl/dotty/blob/main/tests/run/tupled-function-compose.scala) and [`Tuple1.andThen`](https://github.com/lampepfl/dotty/blob/main/tests/run/tupled-function-andThen.scala) methods to compose functions of larger arities and with functions that return tuples.
+
+```scala
+/** Composes two instances of TupledFunction into a new TupledFunction, with this function applied last.
+ *
+ *  @tparam F a function type
+ *  @tparam G a function type
+ *  @tparam FArgs the tuple type with the same types as the function arguments of F and return type of G
+ *  @tparam GArgs the tuple type with the same types as the function arguments of G
+ *  @tparam R the return type of F
+ */
+extension [F, G, FArgs <: Tuple, GArgs <: Tuple, R](f: F)
+  def compose(g: G)(using tg: TupledFunction[G, GArgs => FArgs], tf: TupledFunction[F, FArgs => R]): GArgs => R = {
+  (x: GArgs) => tf.tupled(f)(tg.tupled(g)(x))
+}
+```

docs/sidebar.yml

@@ -148,6 +148,7 @@ subsection:
           - page: reference/experimental/numeric-literals.md
           - page: reference/experimental/explicit-nulls.md
           - page: reference/experimental/cc.md
+          - page: reference/experimental/tupled-function.md
       - page: reference/syntax.md
       - title: Language Versions
         index: reference/language-versions/language-versions.md

library/src-bootstrapped/scala/runtime/TupledFunctions.scala

@@ -0,0 +1,165 @@
+package scala.runtime
+
+import scala.util.TupledFunction
+import scala.annotation.experimental
+
+@experimental
+object TupledFunctions {
+
+  def tupledFunction0[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => ((args: EmptyTuple) => f.asInstanceOf[() => Any].apply()).asInstanceOf[G],
+    untupledImpl = (g: G) => (() => g.asInstanceOf[EmptyTuple => Any].apply(EmptyTuple)).asInstanceOf[F]
+  )
+
+  def tupledFunction1[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => ((args: Tuple1[Any]) => f.asInstanceOf[Any => Any].apply(args._1)).asInstanceOf[G],
+    untupledImpl = (g: G) => ((x1: Any) => g.asInstanceOf[Tuple1[_] => Any].apply(Tuple1(x1))).asInstanceOf[F]
+  )
+
+  def tupledFunction2[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function2[_, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) => Function.untupled(g.asInstanceOf[Tuple2[_, _] => Any]).asInstanceOf[F]
+  )
+
+  def tupledFunction3[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function3[_, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) => Function.untupled(g.asInstanceOf[Tuple3[_, _, _] => Any]).asInstanceOf[F]
+  )
+
+  def tupledFunction4[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function4[_, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) => Function.untupled(g.asInstanceOf[Tuple4[_, _, _, _] => Any]).asInstanceOf[F]
+  )
+
+  def tupledFunction5[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function5[_, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) => Function.untupled(g.asInstanceOf[Tuple5[_, _, _, _, _] => Any]).asInstanceOf[F]
+  )
+
+  def tupledFunction6[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function6[_, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any) =>
+        g.asInstanceOf[Tuple6[_, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6))).asInstanceOf[F]
+  )
+
+  def tupledFunction7[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function7[_, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any) =>
+        g.asInstanceOf[Tuple7[_, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7))).asInstanceOf[F]
+  )
+
+  def tupledFunction8[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function8[_, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any) =>
+        g.asInstanceOf[Tuple8[_, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8))).asInstanceOf[F]
+  )
+
+  def tupledFunction9[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function9[_, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any) =>
+        g.asInstanceOf[Tuple9[_, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9))).asInstanceOf[F]
+  )
+
+  def tupledFunction10[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function10[_, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any) =>
+        g.asInstanceOf[Tuple10[_, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10))).asInstanceOf[F]
+  )
+
+  def tupledFunction11[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function11[_, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any) =>
+        g.asInstanceOf[Tuple11[_, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11))).asInstanceOf[F]
+  )
+
+  def tupledFunction12[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function12[_, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any) =>
+        g.asInstanceOf[Tuple12[_, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12))).asInstanceOf[F]
+  )
+
+  def tupledFunction13[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function13[_, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any) =>
+        g.asInstanceOf[Tuple13[_, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13))).asInstanceOf[F]
+  )
+
+  def tupledFunction14[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function14[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any) =>
+        g.asInstanceOf[Tuple14[_, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14))).asInstanceOf[F]
+  )
+
+  def tupledFunction15[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function15[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any) =>
+        g.asInstanceOf[Tuple15[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15))).asInstanceOf[F]
+  )
+
+  def tupledFunction16[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function16[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any) =>
+        g.asInstanceOf[Tuple16[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16))).asInstanceOf[F]
+  )
+
+  def tupledFunction17[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function17[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any) =>
+        g.asInstanceOf[Tuple17[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17))).asInstanceOf[F]
+  )
+
+  def tupledFunction18[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function18[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any, x18: Any) =>
+        g.asInstanceOf[Tuple18[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18))).asInstanceOf[F]
+  )
+
+  def tupledFunction19[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function19[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any, x18: Any, x19: Any) =>
+        g.asInstanceOf[Tuple19[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19))).asInstanceOf[F]
+  )
+
+  def tupledFunction20[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function20[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any, x18: Any, x19: Any, x20: Any) =>
+        g.asInstanceOf[Tuple20[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20))).asInstanceOf[F]
+  )
+
+  def tupledFunction21[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function21[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any, x18: Any, x19: Any, x20: Any, x21: Any) =>
+        g.asInstanceOf[Tuple21[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21))).asInstanceOf[F]
+  )
+
+  def tupledFunction22[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => f.asInstanceOf[Function22[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _]].tupled.asInstanceOf[G],
+    untupledImpl = (g: G) =>
+      ((x1: Any, x2: Any, x3: Any, x4: Any, x5: Any, x6: Any, x7: Any, x8: Any, x9: Any, x10: Any, x11: Any, x12: Any, x13: Any, x14: Any, x15: Any, x16: Any, x17: Any, x18: Any, x19: Any, x20: Any, x21: Any, x22: Any) =>
+        g.asInstanceOf[Tuple22[_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _] => Any].apply((x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22))).asInstanceOf[F]
+  )
+
+  def tupledFunctionXXL[F, G]: TupledFunction[F, G] = TupledFunction[F, G](
+    tupledImpl = (f: F) => ((args: TupleXXL) => f.asInstanceOf[FunctionXXL].apply(args.elems)).asInstanceOf[G],
+    untupledImpl = (g: G) => new FunctionXXL {
+      override def apply(xs: IArray[Object]): AnyRef = g.asInstanceOf[TupleXXL => AnyRef].apply(TupleXXL.fromIArray(xs))
+    }.asInstanceOf[F]
+  )
+
+}

library/src/scala/util/TupledFunction.scala

@@ -0,0 +1,22 @@
+package scala.util
+
+import scala.annotation.implicitNotFound
+import scala.annotation.experimental
+
+/** Type class relating a `FunctionN[..., R]` with an equivalent tupled function `Function1[TupleN[...], R]`
+ *
+ *  @tparam F a function type
+ *  @tparam G a tupled function type (function of arity 1 receiving a tuple as argument)
+ */
+@implicitNotFound("${F} cannot be tupled as ${G}")
+@experimental
+sealed trait TupledFunction[F, G]:
+  def tupled(f: F): G
+  def untupled(g: G): F
+
+@experimental
+private[scala] object TupledFunction:
+  def apply[F, G](tupledImpl: F => G, untupledImpl: G => F): TupledFunction[F, G] =
+    new TupledFunction[F, G]:
+      def tupled(f: F): G = tupledImpl(f)
+      def untupled(g: G): F = untupledImpl(g)