Merge pull request #12423 from dotty-staging/add-Type-valueOfTuple

Add quoted.Type.valueOfTuple

Author: nicolasstucki

library/src/scala/quoted/Type.scala

@@ -1,6 +1,6 @@
 package scala.quoted
 
-import scala.annotation.compileTimeOnly
+import scala.annotation.{compileTimeOnly, experimental}
 
 /** Type (or type constructor) `T` needed contextually when using `T` in a quoted expression `'{... T ...}` */
 abstract class Type[T <: AnyKind] private[scala]:
@@ -35,11 +35,50 @@ object Type:
    *  @syntax markdown
    */
   def valueOfConstant[T](using Type[T])(using Quotes): Option[T] =
+    ValueOf.unapply(quotes.reflect.TypeRepr.of[T]).asInstanceOf[Option[T]]
+
+  /** Extracts the value of a tuple of singleton constant types.
+   *  Returns Some of the tuple type if it is a tuple singleton constant types.
+   *  Returns None if the type is not a tuple singleton constant types.
+   *
+   *  Example usage:
+   *  ```scala
+   *  ... match
+   *    case '{ $mirrorExpr : Mirror.Sum { type MirroredElemLabels = label } } =>
+   *      Type.valueOfTuple[label] // Option[Tuple]
+   *  }
+   *  ```
+   *  @syntax markdown
+   */
+  @experimental
+  def valueOfTuple[T <: Tuple](using Type[T])(using Quotes): Option[T] =
+    valueOfTuple(quotes.reflect.TypeRepr.of[T]).asInstanceOf[Option[T]]
+
+  private def valueOfTuple(using Quotes)(tpe: quotes.reflect.TypeRepr): Option[Tuple] =
     import quotes.reflect.*
-    def valueOf(tpe: TypeRepr): Option[T] =
-      tpe.dealias.widenTermRefByName match
-        case ConstantType(const) => Some(const.value.asInstanceOf[T])
+    val cons = Symbol.classSymbol("scala.*:")
+    def rec(tpe: TypeRepr): Option[Tuple] =
+      tpe.widenTermRefByName.dealias match
+        case AppliedType(fn, tpes) if defn.isTupleClass(fn.typeSymbol) =>
+          tpes.foldRight(Option[Tuple](EmptyTuple)) {
+            case (_, None) => None
+            case (ValueOf(v), Some(acc)) => Some(v *: acc)
+            case _ => None
+          }
+        case AppliedType(tp, List(ValueOf(headValue), tail)) if tp.derivesFrom(cons) =>
+          rec(tail) match
+            case Some(tailValue) => Some(headValue *: tailValue)
+            case None => None
+        case tpe =>
+          if tpe.derivesFrom(Symbol.classSymbol("scala.EmptyTuple")) then Some(EmptyTuple)
+          else None
+    rec(tpe)
+
+  private object ValueOf:
+    def unapply(using Quotes)(tpe: quotes.reflect.TypeRepr): Option[Any] =
+      import quotes.reflect.*
+      tpe.widenTermRefByName.dealias match
+        case ConstantType(const) => Some(const.value)
         case _ => None
-    valueOf(TypeRepr.of[T])
 
 end Type

project/MiMaFilters.scala

@@ -14,8 +14,7 @@ object MiMaFilters {
     exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.typeMember"),
     exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.typeMembers"),
     exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TermParamClauseMethods.isErased"),
-    exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TermParamClauseMethods.isErased"),
-    exclude[MissingClassProblem]("scala.annotation.experimental"),
+    exclude[DirectMissingMethodProblem]("scala.quoted.Type.valueOfTuple"),
     exclude[MissingClassProblem]("scala.annotation.experimental"),
     exclude[MissingClassProblem]("scala.annotation.internal.ErasedParam"),
     exclude[MissingClassProblem]("scala.annotation.internal.ErasedParam"),

tests/run-macros/i12417/Macros_1.scala

@@ -0,0 +1,13 @@
+import scala.deriving.Mirror
+import scala.compiletime.{constValue, error}
+import scala.quoted.*
+
+object TestMacro {
+  inline def test1[CASE_CLASS <: Product](using m: Mirror.ProductOf[CASE_CLASS]): String =
+    ${ code('m) }
+
+  def code[CASE_CLASS <: Product: Type](m: Expr[Mirror.ProductOf[CASE_CLASS]])(using Quotes): Expr[String] =
+    m match
+      case '{ type t <: Tuple; $_ : Mirror { type MirroredElemLabels = `t` } } =>
+        Expr(Type.valueOfTuple[t].toString)
+}

tests/run-macros/i12417/Test_2.scala

@@ -0,0 +1,7 @@
+import scala.deriving.Mirror
+import scala.compiletime.{constValue, error}
+
+object Test extends App {
+  case class A(x: String, y: Int)
+  assert(TestMacro.test1[A] == "Some((x,y))")
+}

tests/run-macros/i12417b.check

@@ -0,0 +1,6 @@
+Some(())
+Some((1))
+Some((1,2))
+Some((1,2,3))
+Some((1,2,3,4))
+Some((1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26))

tests/run-macros/i12417b/Macros_1.scala

@@ -0,0 +1,18 @@
+import scala.deriving.Mirror
+import scala.compiletime.{constValue, error}
+import scala.quoted.*
+
+object TestMacro {
+  inline def test1: Unit =
+    ${ code() }
+
+  def code()(using Quotes): Expr[Unit] =
+    '{
+      println(${Expr(Type.valueOfTuple[EmptyTuple].toString)})
+      println(${Expr(Type.valueOfTuple[1 *: EmptyTuple].toString)})
+      println(${Expr(Type.valueOfTuple[(1, 2)].toString)})
+      println(${Expr(Type.valueOfTuple[(1, 2, 3)].toString)})
+      println(${Expr(Type.valueOfTuple[(1, 2, 3, 4)].toString)})
+      println(${Expr(Type.valueOfTuple[(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)].toString)})
+    }
+}

tests/run-macros/i12417b/Test_2.scala

@@ -0,0 +1 @@
+@main def Test = TestMacro.test1