From e0ff75d7e3d609087990f77f5f1046d34ee5bb7e Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Tue, 22 Feb 2022 20:21:35 +0100
Subject: [PATCH] Properly map children of mapped classes

If sealed classes are mapped in TypeTreeMap or mapSymbols, their
children have to be mapped accordingly.
---
 compiler/src/dotty/tools/dotc/core/Symbols.scala     | 10 +++++++++-
 .../dotty/tools/dotc/printing/RefinedPrinter.scala   |  2 +-
 .../tools/dotc/transform/SyntheticMembers.scala      |  2 +-
 tests/pos/i12508c.scala                              | 12 ++++++++++++
 4 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 tests/pos/i12508c.scala

diff --git a/compiler/src/dotty/tools/dotc/core/Symbols.scala b/compiler/src/dotty/tools/dotc/core/Symbols.scala
index 7f0969d55f07..93255f8d757d 100644
--- a/compiler/src/dotty/tools/dotc/core/Symbols.scala
+++ b/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
     }
 
diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
index cf5942a178f0..23c7f3b0e3e0 100644
--- a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
+++ b/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
diff --git a/compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala b/compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala
index 3a94a78b3d8e..eb6fc2feff7e 100644
--- a/compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala
+++ b/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 =
diff --git a/tests/pos/i12508c.scala b/tests/pos/i12508c.scala
new file mode 100644
index 000000000000..97c81cd61fcd
--- /dev/null
+++ b/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
+    }
+  )
\ No newline at end of file