Properly map children of mapped classes

If sealed classes are mapped in TypeTreeMap or mapSymbols, their
children have to be mapped accordingly.

Author: odersky

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

@@ -826,11 +826,19 @@ object Symbols {
         copy.info = completer
         copy.denot match
           case cd: ClassDenotation =>
-            cd.registeredCompanion = cd.unforcedRegisteredCompanion.subst(originals, copies)
+            cd.registeredCompanion = original.registeredCompanion.subst(originals, copies)
           case _ =>
       }
 
       copies.foreach(_.ensureCompleted()) // avoid memory leak
+
+      // Update Child annotations of classes encountered previously to new values
+      // if some child is among the mapped symbols
+      for orig <- ttmap1.substFrom do
+        if orig.is(Sealed) && orig.children.exists(originals.contains) then
+          val sealedCopy = orig.subst(ttmap1.substFrom, ttmap1.substTo)
+          sealedCopy.annotations = sealedCopy.annotations.mapConserve(ttmap1.apply)
+
       copies
     }
 

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -1040,7 +1040,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       else if (sym.is(ModuleClass) && sym.isPackageObject && sym.name.stripModuleClassSuffix == tpnme.PACKAGE)
         nameString(sym.owner.name)
       else if (sym.is(ModuleClass))
-        nameString(sym.name.stripModuleClassSuffix)
+        nameString(sym.name.stripModuleClassSuffix) + idString(sym)
       else if (hasMeaninglessName(sym))
         simpleNameString(sym.owner) + idString(sym)
       else

compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala

@@ -140,7 +140,7 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
           val parentEnum = vdef.owner.companionClass
           val children = parentEnum.children.zipWithIndex
           val candidate: Option[Int] = children.collectFirst { case (child, idx) if child == vdef => idx }
-          assert(candidate.isDefined, i"could not find child for $vdef")
+          assert(candidate.isDefined, i"could not find child for $vdef in ${parentEnum.children}%, % of $parentEnum")
           Literal(Constant(candidate.get))
 
       def toStringBody(vrefss: List[List[Tree]]): Tree =

tests/pos/i12508c.scala

@@ -0,0 +1,12 @@
+def fun(a: Any, b: Any = 2): Any = ???
+
+def test =
+  fun(
+    b = println(1),
+    a = {
+      enum Option[+X]:
+        case Some(x: X)
+        case None
+      if ??? then Option.Some(1) else Option.None
+    }
+  )