From cecd05356beecd232053d4c593af54bcc12cad0e Mon Sep 17 00:00:00 2001
From: Hamza Remmal <hamza@remmal.net>
Date: Wed, 6 Nov 2024 18:16:33 +0100
Subject: [PATCH] Revert "Drop inaccessible subclasses from refineUsingParent"

---
 .../src/dotty/tools/dotc/core/Decorators.scala     |  2 +-
 compiler/src/dotty/tools/dotc/core/TypeOps.scala   |  6 +-----
 tests/pos/i21790.scala                             | 14 --------------
 3 files changed, 2 insertions(+), 20 deletions(-)
 delete mode 100644 tests/pos/i21790.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Decorators.scala b/compiler/src/dotty/tools/dotc/core/Decorators.scala
index 96a2d45db80d..29d4b3fa4052 100644
--- a/compiler/src/dotty/tools/dotc/core/Decorators.scala
+++ b/compiler/src/dotty/tools/dotc/core/Decorators.scala
@@ -292,7 +292,7 @@ object Decorators {
       case _ => String.valueOf(x).nn
 
     /** Returns the simple class name of `x`. */
-    def className: String = if x == null then "<null>" else x.getClass.getSimpleName.nn
+    def className: String = x.getClass.getSimpleName.nn
 
   extension [T](x: T)
     def assertingErrorsReported(using Context): T = {
diff --git a/compiler/src/dotty/tools/dotc/core/TypeOps.scala b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
index 79eac7bde38d..2403a6e22bc6 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeOps.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeOps.scala
@@ -930,11 +930,7 @@ object TypeOps:
       for tp <- mixins.reverseIterator do
         protoTp1 <:< tp
       maximizeType(protoTp1, NoSpan)
-      val inst = wildApprox(protoTp1)
-      if !inst.classSymbol.exists then
-        // E.g. i21790, can't instantiate S#CA as a subtype of O.A, because O.CA isn't accessible
-        NoType
-      else inst
+      wildApprox(protoTp1)
     }
 
     if (protoTp1 <:< tp2) instantiate()
diff --git a/tests/pos/i21790.scala b/tests/pos/i21790.scala
deleted file mode 100644
index 0cc7db935ac7..000000000000
--- a/tests/pos/i21790.scala
+++ /dev/null
@@ -1,14 +0,0 @@
-package p
-
-trait S:
-  sealed trait A
-  private class CA() extends A
-
-object O extends S
-
-trait T
-
-class Test:
-  def f(e: T) = e match
-    case _: O.A =>
-    case _      =>