From 0b7c5990b43b235df5931b8bc1383e7540a64f83 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Sun, 5 Jun 2022 15:28:09 +0200
Subject: [PATCH] Handle Range cases when reducing match types

Fixes #15362
---
 .../dotty/tools/dotc/core/TypeComparer.scala    |  2 ++
 compiler/src/dotty/tools/dotc/core/Types.scala  |  2 +-
 tests/neg/i15362.scala                          | 17 +++++++++++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 tests/neg/i15362.scala

diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 134a5006b887..c07e8bc51790 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -2912,6 +2912,8 @@ class TrackingTypeComparer(initctx: Context) extends TypeComparer(initctx) {
         case cas: HKTypeLambda =>
           caseLambda = constrained(cas)
           caseLambda.resultType
+        case _: Range =>
+          return Some(NoType)
         case _ =>
           cas
       }
diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala
index 8b9f8690604e..d9f423575a46 100644
--- a/compiler/src/dotty/tools/dotc/core/Types.scala
+++ b/compiler/src/dotty/tools/dotc/core/Types.scala
@@ -5989,7 +5989,7 @@ object Types {
   /** A range of possible types between lower bound `lo` and upper bound `hi`.
    *  Only used internally in `ApproximatingTypeMap`.
    */
-  private case class Range(lo: Type, hi: Type) extends UncachedGroundType {
+  private[core] case class Range(lo: Type, hi: Type) extends UncachedGroundType {
     assert(!lo.isInstanceOf[Range])
     assert(!hi.isInstanceOf[Range])
 
diff --git a/tests/neg/i15362.scala b/tests/neg/i15362.scala
new file mode 100644
index 000000000000..2d30cd92e6d4
--- /dev/null
+++ b/tests/neg/i15362.scala
@@ -0,0 +1,17 @@
+import scala.compiletime.*
+import scala.compiletime.ops.int.*
+
+abstract sealed class HList :
+  def ::[H](head: H): HNonEmpty[H, this.type] = HNonEmpty(head, this)
+
+case object HNil extends HList
+case class HNonEmpty[H, T <: HList](head: H, tail: T) extends HList :
+  type Elem[N <: Int] =
+    N match
+      case 0 => H
+      case S[n1] => Elem[n1]
+
+  inline def apply[N <: Int](n: N): Elem[N] =
+    n match
+      case _: 0 => head
+      case _: S[n1] => tail.asInstanceOf[HNonEmpty[?, ?]].apply(constValue[n1]) // error