Merge pull request #13663 from dotty-staging/fix-13660

Remember compared polytypes

Author: smarter

community-build/test/scala/dotty/communitybuild/CommunityBuildTest.scala

@@ -45,7 +45,7 @@ class CommunityBuildTestB:
  @Test def fs2 = projects.fs2.run()
  @Test def munit = projects.munit.run()
  @Test def munitCatsEffect = projects.munitCatsEffect.run()
- // @Test def perspective = projects.perspective.run()
+ @Test def perspective = projects.perspective.run()
  @Test def scalacheckEffect = projects.scalacheckEffect.run()
  @Test def scodec = projects.scodec.run()
  @Test def scodecBits = projects.scodecBits.run()

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

@@ -184,6 +184,12 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
  val bounds = gadtBounds(sym)
  bounds != null && op(bounds)
 
+ private inline def comparingTypeLambdas(tl1: TypeLambda, tl2: TypeLambda)(op: => Boolean): Boolean =
+ val saved = comparedTypeLambdas
+ comparedTypeLambdas += tl1
+ comparedTypeLambdas += tl2
+ try op finally comparedTypeLambdas = saved
+
  protected def isSubType(tp1: Type, tp2: Type, a: ApproxState): Boolean = {
  val savedApprox = approx
  val savedLeftRoot = leftRoot
@@ -629,12 +635,10 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
  migrateTo3 ||
  tp1.typeParams.corresponds(tp2.typeParams)((tparam1, tparam2) =>
  isSubType(tparam2.paramInfo.subst(tp2, tp1), tparam1.paramInfo))
- val saved = comparedTypeLambdas
- comparedTypeLambdas += tp1
- comparedTypeLambdas += tp2
- val variancesOK = variancesConform(tp1.typeParams, tp2.typeParams)
- try variancesOK && boundsOK && isSubType(tp1.resType, tp2.resType.subst(tp2, tp1))
- finally comparedTypeLambdas = saved
+ comparingTypeLambdas(tp1, tp2) {
+ val variancesOK = variancesConform(tp1.typeParams, tp2.typeParams)
+ variancesOK && boundsOK && isSubType(tp1.resType, tp2.resType.subst(tp2, tp1))
+ }
  case _ =>
  val tparams1 = tp1.typeParams
  if (tparams1.nonEmpty)
@@ -704,9 +708,11 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
  case tp2: PolyType =>
  def comparePoly = tp1 match {
  case tp1: PolyType =>
- (tp1.signature consistentParams tp2.signature) &&
- matchingPolyParams(tp1, tp2) &&
- isSubType(tp1.resultType, tp2.resultType.subst(tp2, tp1))
+ comparingTypeLambdas(tp1, tp2) {
+ (tp1.signature consistentParams tp2.signature)
+ && matchingPolyParams(tp1, tp2)
+ && isSubType(tp1.resultType, tp2.resultType.subst(tp2, tp1))
+ }
  case _ => false
  }
  comparePoly

tests/pos/i13660.scala

@@ -0,0 +1,15 @@
+type Const[A] = [_] =>> A
+type FunctionK[A[_], B[_]] = [Z] => A[Z] => B[Z]
+
+type #~>#:[T, R] = FunctionK[Const[T], Const[R]]
+
+object FunctionK:
+ def liftConst[A, B](f: A => B): /*FunctionK[Const[A], Const[B]]*/ A #~>#: B =
+ [Z1] => (a: A) => f(a)
+
+trait FoldableK[F[_[_], _]]:
+
+ def foldMapK1[A[_], C, B](fa: F[A, C])(f: FunctionK[A, Const[B]]): B
+
+ def toListK[A, C](fa: F[Const[A], C]): List[A] =
+ foldMapK1(fa)(FunctionK.liftConst(List(_: A)))

tests/pos/i7888.scala

@@ -0,0 +1,8 @@
+def usingSeq[B](f: [A] => Seq[A] => B): B = {
+ f(Nil)
+}
+def crash() = {
+ usingSeq { [A] => (a: Seq[A]) =>
+ a
+ }
+}