Fix #13495: break completion cycles

Author: OlivierBlanvillain

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

@@ -1605,10 +1605,10 @@ object SymDenotations {
         // children that are defined in the same file as their parents.
         def maybeChild(sym: Symbol) =
           (sym.isClass && !this.is(JavaDefined) || sym.originDenotation.is(EnumVal))
-          && !owner.is(Package)
+          && (!owner.is(Package)
              || sym.originDenotation.infoOrCompleter.match
                   case _: SymbolLoaders.SecondCompleter => sym.associatedFile == this.symbol.associatedFile
-                  case _ => false
+                  case _ => false)
 
         if owner.isClass then
           for c <- owner.info.decls.toList if maybeChild(c) do

tests/pos/13495.scala

@@ -0,0 +1,20 @@
+import scala.annotation.showAsInfix
+
+object Test {
+  trait Component
+  sealed trait Deleted extends Component
+
+  type Deletable[L <: CList] <: CList = L match {
+    case h &: t => (h | Deleted) &: Deletable[t]
+    case CNil => CNil
+  }
+
+  sealed trait CList
+  sealed trait CNil extends CList
+  @showAsInfix case class &:[+C <: Component, +L <: CList](h: C, t: L) extends CList
+
+  case class A(x: Int, y: Int) extends Component
+  case class B(x: Int, y: Int) extends Component
+
+  val x: Deletable[A &: B &: CNil] = ???
+}