From 27fe00e9e19a1596f3ab40dfbec0747986832ab7 Mon Sep 17 00:00:00 2001
From: Eugene Flesselle <eugene@flesselle.net>
Date: Thu, 4 Jul 2024 19:15:59 +0200
Subject: [PATCH] Fix isomorphism tests of `AndOrType`s under non-empty
 `BinderPairs` (#21017)

Before the changes, when comparing two `HKTypeLambda` result types, the
list of binding pairs was lost when entering comparison of `AndOrType`s,
which caused the `equals` to fail, and hence prevented hash-consing.

Even though `M1` and `M2` in pos/i20858-min should still conform to
one-another, we entered a deep-subtype comparison because of the order
in which the TypeComparer does dealiasing of AppliedTypes, and
comparison of MatchCases and AndTypes.

Fix #20858
[Cherry-picked f2829c3fab28cc6ab47a5627abda855884476572]
---
 .../src/dotty/tools/dotc/core/Types.scala     | 10 +++++++
 tests/pos/i20858-min.scala                    | 10 +++++++
 tests/pos/i20858/defns_1.scala                | 27 +++++++++++++++++++
 tests/pos/i20858/usages_2.scala               |  2 ++
 4 files changed, 49 insertions(+)
 create mode 100644 tests/pos/i20858-min.scala
 create mode 100644 tests/pos/i20858/defns_1.scala
 create mode 100644 tests/pos/i20858/usages_2.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 2d3027504936..4be905beefcc 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -3348,6 +3348,8 @@ object Types extends TypeUtils {
       else this match
         case tp: OrType => OrType.make(tp1, tp2, tp.isSoft)
         case tp: AndType => AndType.make(tp1, tp2, checkValid = true)
+
+    override def hashIsStable: Boolean = tp1.hashIsStable && tp2.hashIsStable
   }
 
   abstract case class AndType(tp1: Type, tp2: Type) extends AndOrType {
@@ -3393,6 +3395,10 @@ object Types extends TypeUtils {
       case that: AndType => tp1.eq(that.tp1) && tp2.eq(that.tp2)
       case _ => false
     }
+
+    override protected def iso(that: Any, bs: BinderPairs) = that match
+      case that: AndType => tp1.equals(that.tp1, bs) && tp2.equals(that.tp2, bs)
+      case _ => false
   }
 
   final class CachedAndType(tp1: Type, tp2: Type) extends AndType(tp1, tp2)
@@ -3542,6 +3548,10 @@ object Types extends TypeUtils {
       case that: OrType => tp1.eq(that.tp1) && tp2.eq(that.tp2) && isSoft == that.isSoft
       case _ => false
     }
+
+    override protected def iso(that: Any, bs: BinderPairs) = that match
+      case that: OrType => tp1.equals(that.tp1, bs) && tp2.equals(that.tp2, bs) && isSoft == that.isSoft
+      case _ => false
   }
 
   final class CachedOrType(tp1: Type, tp2: Type, override val isSoft: Boolean) extends OrType(tp1, tp2)
diff --git a/tests/pos/i20858-min.scala b/tests/pos/i20858-min.scala
new file mode 100644
index 000000000000..9c47b04031e6
--- /dev/null
+++ b/tests/pos/i20858-min.scala
@@ -0,0 +1,10 @@
+
+type M[F[_,_]] = Int match
+  case 0 => String & M[F]
+
+type M1 = M[[x,y] =>> x | y]
+type M2 = M[[x,y] =>> x | y]
+
+def Test: Unit =
+  val x: M1 = ???
+  val _: M2 = x // was error
diff --git a/tests/pos/i20858/defns_1.scala b/tests/pos/i20858/defns_1.scala
new file mode 100644
index 000000000000..7b4b84745b58
--- /dev/null
+++ b/tests/pos/i20858/defns_1.scala
@@ -0,0 +1,27 @@
+import scala.compiletime.*
+import scala.deriving.*
+
+sealed trait ZIO[-R, +E, +A]
+sealed abstract class ZLayer[-RIn, +E, +ROut]
+object ZLayer:
+  def apply[RIn, E, ROut](zio: => ZIO[RIn, E, ROut]): ZLayer[RIn, E, ROut] = ???
+type URIO[-R, +A] = ZIO[R, Nothing, A]
+type IAnyType[T <: Tuple] = Tuple.Fold[T, Any, [x, y] =>> x & y]
+type UAnyType[T <: Tuple] = Tuple.Fold[T, Any, [x, y] =>> x | y]
+
+
+trait AutoLayer[A]:
+  def zlayer(using
+             p: Mirror.ProductOf[A]
+            ): ZLayer[IAnyType[p.MirroredElemTypes], Nothing, A]
+
+object AutoLayer:
+  inline given derived[A](using p: Mirror.ProductOf[A]): AutoLayer[A] = {
+    val a: ZIO[IAnyType[p.MirroredElemTypes], Nothing, A] = ???
+    new AutoLayer[A]:
+      override def zlayer(using
+                          pp: Mirror.ProductOf[A]
+                         ): ZLayer[IAnyType[pp.MirroredElemTypes], Nothing, A] = ZLayer {
+        a.asInstanceOf[ZIO[IAnyType[pp.MirroredElemTypes], Nothing, A]]
+      }
+  }
\ No newline at end of file
diff --git a/tests/pos/i20858/usages_2.scala b/tests/pos/i20858/usages_2.scala
new file mode 100644
index 000000000000..3a05ba54e97a
--- /dev/null
+++ b/tests/pos/i20858/usages_2.scala
@@ -0,0 +1,2 @@
+
+case class TestService(port: Int) derives AutoLayer // was error