diff --git a/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala b/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala index a863a982a44d..bb65cce84042 100644 --- a/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala +++ b/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala @@ -3,6 +3,7 @@ package dotc package core import Contexts.*, Decorators.*, Symbols.*, Types.* +import NameKinds.UniqueName import config.Printers.{gadts, gadtsConstr} import util.{SimpleIdentitySet, SimpleIdentityMap} import printing._ @@ -71,16 +72,29 @@ class GadtConstraint private ( externalize(constraint.nonParamBounds(param)).bounds def fullLowerBound(param: TypeParamRef)(using Context): Type = - constraint.minLower(param).foldLeft(nonParamBounds(param).lo) { - (t, u) => t | externalize(u) + val self = externalize(param) + constraint.minLower(param).foldLeft(nonParamBounds(param).lo) { (acc, p) => + externalize(p) match + // drop any lower param that is a GADT symbol + // and is upper-bounded by a non-Any super-type of the original parameter + // e.g. in pos/i14287.min + // B$1 had info <: X and fullBounds >: B$2 <: X, and + // B$2 had info <: B$1 and fullBounds <: B$1 + // We can use the info of B$2 to drop the lower-bound of B$1 + // and return non-bidirectional bounds B$1 <: X and B$2 <: B$1. + case tp: TypeRef if tp.symbol.isPatternBound && self =:= tp.info.hiBound => acc + case tp => acc | tp } def fullUpperBound(param: TypeParamRef)(using Context): Type = - constraint.minUpper(param).foldLeft(nonParamBounds(param).hi) { (t, u) => - val eu = externalize(u) - // Any as the upper bound means "no bound", but if F is higher-kinded, - // Any & F = F[_]; this is wrong for us so we need to short-circuit - if t.isAny then eu else t & eu + val self = externalize(param) + constraint.minUpper(param).foldLeft(nonParamBounds(param).hi) { (acc, u) => + externalize(u) match + case tp: TypeRef if tp.symbol.isPatternBound && self =:= tp.info.loBound => acc // like fullLowerBound + case tp => + // Any as the upper bound means "no bound", but if F is higher-kinded, + // Any & F = F[_]; this is wrong for us so we need to short-circuit + if acc.isAny then tp else acc & tp } def externalize(tp: Type, theMap: TypeMap | Null = null)(using Context): Type = tp match diff --git a/tests/pos/i14287.min.scala b/tests/pos/i14287.min.scala new file mode 100644 index 000000000000..8f7773ab0ac8 --- /dev/null +++ b/tests/pos/i14287.min.scala @@ -0,0 +1,7 @@ +enum Foo[+F[_]]: + case Bar[B[_]](value: Foo[B]) extends Foo[B] + +class Test: + def test[X[_]](foo: Foo[X]): Foo[X] = foo match + case Foo.Bar(Foo.Bar(x)) => Foo.Bar(x) + case _ => foo diff --git a/tests/pos/i14287.scala b/tests/pos/i14287.scala new file mode 100644 index 000000000000..1291dc8adefc --- /dev/null +++ b/tests/pos/i14287.scala @@ -0,0 +1,16 @@ +// scalac: -Yno-deep-subtypes +enum Free[+F[_], A]: + case Return(a: A) + case Suspend(s: F[A]) + case FlatMap[F[_], A, B]( + s: Free[F, A], + f: A => Free[F, B]) extends Free[F, B] + + def flatMap[F2[x] >: F[x], B](f: A => Free[F2,B]): Free[F2,B] = + FlatMap(this, f) + + @scala.annotation.tailrec + final def step: Free[F, A] = this match + case FlatMap(FlatMap(fx, f), g) => fx.flatMap(x => f(x).flatMap(y => g(y))).step + case FlatMap(Return(x), f) => f(x).step + case _ => this diff --git a/tests/pos/i15523.avoid.scala b/tests/pos/i15523.avoid.scala new file mode 100644 index 000000000000..afbfc1a69d60 --- /dev/null +++ b/tests/pos/i15523.avoid.scala @@ -0,0 +1,8 @@ +// scalac: -Werror +// like the original, but with a case body `a` +// which caused type avoidance to infinitely recurse +sealed trait Parent +final case class Leaf[A, B >: A](a: A, b: B) extends Parent + +def run(x: Parent) = x match + case Leaf(a, _) => a diff --git a/tests/pos/i15523.scala b/tests/pos/i15523.scala new file mode 100644 index 000000000000..cf63613c29ac --- /dev/null +++ b/tests/pos/i15523.scala @@ -0,0 +1,7 @@ +// scalac: -Werror +sealed trait Parent +final case class Leaf[A, B >: A](a: A, b: B) extends Parent + +def run(x: Parent): Unit = x match { + case Leaf(a, b) => +} diff --git a/tests/pos/i16777.scala b/tests/pos/i16777.scala new file mode 100644 index 000000000000..4218aea29d9f --- /dev/null +++ b/tests/pos/i16777.scala @@ -0,0 +1,52 @@ +// scalac: -Ykind-projector:underscores + +sealed abstract class Free[+S[_, _], +E, +A] { + @inline final def flatMap[S1[e, a] >: S[e, a], B, E1 >: E](fun: A => Free[S1, E1, B]): Free[S1, E1, B] = Free.FlatMapped[S1, E, E1, A, B](this, fun) + @inline final def map[B](fun: A => B): Free[S, E, B] = flatMap(a => Free.pure[S, B](fun(a))) + @inline final def as[B](as: => B): Free[S, E, B] = map(_ => as) + @inline final def *>[S1[e, a] >: S[e, a], B, E1 >: E](sc: Free[S1, E1, B]): Free[S1, E1, B] = flatMap(_ => sc) + @inline final def <*[S1[e, a] >: S[e, a], B, E1 >: E](sc: Free[S1, E1, B]): Free[S1, E1, A] = flatMap(r => sc.as(r)) + + @inline final def void: Free[S, E, Unit] = map(_ => ()) + + // FIXME: Scala 3.1.4 bug: false unexhaustive match warning + /// @nowarn("msg=pattern case: Free.FlatMapped") + @inline final def foldMap[S1[e, a] >: S[e, a], G[+_, +_]](transform: S1 ~>> G)(implicit G: Monad2[G]): G[E, A] = { + this match { + case Free.Pure(a) => G.pure(a) + case Free.Suspend(a) => transform.apply(a) + case Free.FlatMapped(sub, cont) => + sub match { + case Free.FlatMapped(sub2, cont2) => sub2.flatMap(a => cont2(a).flatMap(cont)).foldMap(transform) + case another => G.flatMap(another.foldMap(transform))(cont(_).foldMap(transform)) + } + } + } +} + +trait ~>>[-F[_, _], +G[_, _]] { + def apply[E, A](f: F[E, A]): G[E, A] +} + +object Free { + @inline def pure[S[_, _], A](a: A): Free[S, Nothing, A] = Pure(a) + @inline def lift[S[_, _], E, A](s: S[E, A]): Free[S, E, A] = Suspend(s) + + final case class Pure[S[_, _], A](a: A) extends Free[S, Nothing, A] { + override def toString: String = s"Pure:[$a]" + } + final case class Suspend[S[_, _], E, A](a: S[E, A]) extends Free[S, E, A] { + override def toString: String = s"Suspend:[$a]" + } + final case class FlatMapped[S[_, _], E, E1 >: E, A, B](sub: Free[S, E, A], cont: A => Free[S, E1, B]) extends Free[S, E1, B] { + override def toString: String = s"FlatMapped:[sub=$sub]" + } +} + +type Monad2[F[+_, +_]] = Monad3[λ[(`-R`, `+E`, `+A`) => F[E, A]]] + +trait Monad3[F[-_, +_, +_]] { + def flatMap[R, E, A, B](r: F[R, E, A])(f: A => F[R, E, B]): F[R, E, B] + def flatten[R, E, A](r: F[R, E, F[R, E, A]]): F[R, E, A] = flatMap(r)(identity) + def pure[A](a: A): F[Any, Nothing, A] +}