`Ycheck` fail when `map`ping `Option` on `Tuple`

[Sporarum]

Compiler version

tasty-core / scalaVersion
        3.1.1-RC2
scala3-sbt-bridge / scalaVersion
        3.1.1-RC2
scala3-interfaces / scalaVersion
        3.1.1-RC2
scala3-compiler / scalaVersion
        3.1.1-RC2
scala3-library / scalaVersion
        3.1.1-RC2
scalaVersion
        3.1.1-RC2

Minimized code

val p: (Option[Int], Option[String]) = (1,"foo").map([T] => (x: T) => Option.apply[T](x))

(works correctly with a 1-Tuple, like 1 *: EmptyTuple)

Output

When running scalac <file>:

[success] Total time: 4 s, completed 25 janv. 2022 à 22:29:17

When running scalac -Ycheck:all <file>:

checking tests\pos\mapOnPair.scala after phase typer
exception while typing val p: Tuple2[Option[Int], Option[String]] =
  Tuple2.apply[Int, String](1, "foo").map[Option](
    {
      final class $anon() extends Object(), PolyFunction {
        def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
      }
      new $anon():([T] => (T) => Option[T])
    }
  ) of class class dotty.tools.dotc.ast.Trees$ValDef # -1
exception while typing final module class mapOnPair1() extends Object() { this: mapOnPair1.type =>
  val p: Tuple2[Option[Int], Option[String]] =
    Tuple2.apply[Int, String](1, "foo").map[Option](
      {
        final class $anon() extends Object(), PolyFunction {
          def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
        }
        new $anon():([T] => (T) => Option[T])
      }
    )
} of class class dotty.tools.dotc.ast.Trees$TypeDef # -1
exception while typing package <empty> {
  final lazy module val mapOnPair1: mapOnPair1 = new mapOnPair1()
  final module class mapOnPair1() extends Object() { this: mapOnPair1.type =>
    val p: Tuple2[Option[Int], Option[String]] =
      Tuple2.apply[Int, String](1, "foo").map[Option](
        {
          final class $anon() extends Object(), PolyFunction {
            def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
          }
          new $anon():([T] => (T) => Option[T])
        }
      )
  }
} of class class dotty.tools.dotc.ast.Trees$PackageDef # -1
*** error while checking tests\pos\mapOnPair.scala after phase typer ***
exception occurred while compiling tests\pos\mapOnPair.scala
Exception in thread "main" java.lang.AssertionError: assertion failed: Types differ
Original type : Option[Int] *: Nothing *: EmptyTuple
After checking: (Int, String) match {
  case EmptyTuple => EmptyTuple
  case h *: t => Option[h] *: scala.Tuple.Map[t, Option]
} <: Tuple
Original tree : Tuple2.apply[Int, String](1, "foo").map[Option](
  {
    final class $anon() extends Object(), PolyFunction {
      def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
    }
    new $anon():([T] => (T) => Option[T])
  }
)
After checking: Tuple2.apply[Int, String](1, "foo").map[Option](
  {
    final class $anon() extends Object(), PolyFunction {
      def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
    }
    new $anon():([T] => (T) => Option[T])
  }
)
Why different :
             Subtype trace:
 } <: Tuple  <:  Option[Int] *: Nothing *: EmptyTupleion]
    ==> Option[Int] *: Option[String] *: EmptyTuple  <:  Option[Int] *: Nothing *: EmptyTuple
      ==> scala.type  <:  scala.type
      <== scala.type  <:  scala.type = true
      ==> Option[Int]  <:  Option[Int]
        ==> Option[Int]  <:  Option[Int]
        <== Option[Int]  <:  Option[Int] = true
      <== Option[Int]  <:  Option[Int] = true
      ==> Option[String] *: EmptyTuple  <:  Nothing *: EmptyTuple
        ==> scala.type  <:  scala.type
        <== scala.type  <:  scala.type = true
        ==> Option[String]  <:  Nothing
        <== Option[String]  <:  Nothing = false
      <== Option[String] *: EmptyTuple  <:  Nothing *: EmptyTuple = false
    <== Option[Int] *: Option[String] *: EmptyTuple  <:  Option[Int] *: Nothing *: EmptyTuple = false
 } <: Tuple  <:  Option[Int] *: Nothing *: EmptyTuple = false while compiling tests\pos\mapOnPair.scala
java.lang.AssertionError: assertion failed: Types differ
Original type : Option[Int] *: Nothing *: EmptyTuple
After checking: (Int, String) match {
  case EmptyTuple => EmptyTuple
  case h *: t => Option[h] *: scala.Tuple.Map[t, Option]
} <: Tuple
Original tree : Tuple2.apply[Int, String](1, "foo").map[Option](
  {
    final class $anon() extends Object(), PolyFunction {
      def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
    }
    new $anon():([T] => (T) => Option[T])
  }
)
After checking: Tuple2.apply[Int, String](1, "foo").map[Option](
  {
    final class $anon() extends Object(), PolyFunction {
      def apply[T >: Nothing <: Any](x: T): Option[T] = Option.apply[T](x)
    }
    new $anon():([T] => (T) => Option[T])
  }
)
Why different :
             Subtype trace:
 } <: Tuple  <:  Option[Int] *: Nothing *: EmptyTupleion]
    ==> Option[Int] *: Option[String] *: EmptyTuple  <:  Option[Int] *: Nothing *: EmptyTuple
      ==> scala.type  <:  scala.type
      <== scala.type  <:  scala.type = true
      ==> Option[Int]  <:  Option[Int]
        ==> Option[Int]  <:  Option[Int]
        <== Option[Int]  <:  Option[Int] = true
      <== Option[Int]  <:  Option[Int] = true
      ==> Option[String] *: EmptyTuple  <:  Nothing *: EmptyTuple
        ==> scala.type  <:  scala.type
        <== scala.type  <:  scala.type = true
        ==> Option[String]  <:  Nothing
        <== Option[String]  <:  Nothing = false
      <== Option[String] *: EmptyTuple  <:  Nothing *: EmptyTuple = false
    <== Option[Int] *: Option[String] *: EmptyTuple  <:  Option[Int] *: Nothing *: EmptyTuple = false
 } <: Tuple  <:  Option[Int] *: Nothing *: EmptyTuple = false
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:339)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:310)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3057)
        at dotty.tools.dotc.typer.Typer.typedValDef(Typer.scala:2192)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2783)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2871)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:326)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:310)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2963)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3013)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:549)
        at dotty.tools.dotc.typer.Typer.typedClassDef(Typer.scala:2454)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedClassDef(TreeChecker.scala:484)
        at dotty.tools.dotc.typer.Typer.typedTypeOrClassDef$1(Typer.scala:2797)
        at dotty.tools.dotc.typer.Typer.typedNamed$1(Typer.scala:2801)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2871)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:326)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:310)
        at dotty.tools.dotc.typer.Typer.traverse$1(Typer.scala:2963)
        at dotty.tools.dotc.typer.Typer.typedStats(Typer.scala:3013)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedStats(TreeChecker.scala:549)
        at dotty.tools.dotc.typer.Typer.typedPackageDef(Typer.scala:2581)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedPackageDef(TreeChecker.scala:575)
        at dotty.tools.dotc.typer.Typer.typedUnnamed$1(Typer.scala:2842)
        at dotty.tools.dotc.typer.Typer.typedUnadapted(Typer.scala:2872)
        at dotty.tools.dotc.typer.ReTyper.typedUnadapted(ReTyper.scala:121)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typedUnadapted(TreeChecker.scala:326)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2937)
        at dotty.tools.dotc.typer.Typer.typed(Typer.scala:2941)
        at dotty.tools.dotc.transform.TreeChecker$Checker.typed(TreeChecker.scala:310)
        at dotty.tools.dotc.typer.Typer.typedExpr(Typer.scala:3057)
        at dotty.tools.dotc.transform.TreeChecker.check(TreeChecker.scala:144)
        at dotty.tools.dotc.transform.TreeChecker.run(TreeChecker.scala:111)
        at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:308)
        at scala.collection.immutable.List.map(List.scala:246)
        at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:309)
        at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:259)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1328)
        at dotty.tools.dotc.Run.runPhases$1(Run.scala:270)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:278)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:287)
        at dotty.tools.dotc.Run.compileSources(Run.scala:220)
        at dotty.tools.dotc.Run.compile(Run.scala:204)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:39)
        at dotty.tools.dotc.Driver.process(Driver.scala:199)
        at dotty.tools.dotc.Driver.process(Driver.scala:167)
        at dotty.tools.dotc.Driver.process(Driver.scala:179)
        at dotty.tools.dotc.Driver.main(Driver.scala:209)
        at dotty.tools.dotc.Main.main(Main.scala)

Expectation

Ycheck should probably succeed, given the code can even execute:
https://scastie.scala-lang.org/xHL4deBNRwaCvqAn71H5og

[nicolasstucki]

Workarround

- val p: (Option[Int], Option[String]) = (1,"foo").map([T] => (x: T) => Option.apply[T](x))
+ val p: (Option[Int], Option[String]) = (1,"foo").map[Option]([T] => (x: T) => Option.apply[T](x))

[nicolasstucki]

It is strange that the first time we type check it we get

Original type : Option[Int] *: Nothing *: EmptyTuple