From 3a26fe814d3e70c7c6a5ddf699203c9edab6ed42 Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Fri, 20 Dec 2024 00:07:04 +0100
Subject: [PATCH] Fix: Skip existentials in when accessing result type in
 augmentConstructorType

---
 compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala b/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
index e104a52fd774..e52b5b6a9329 100644
--- a/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
+++ b/compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala
@@ -23,6 +23,7 @@ import CCState.*
 import StdNames.nme
 import NameKinds.{DefaultGetterName, WildcardParamName, UniqueNameKind}
 import reporting.{trace, Message, OverrideError}
+import Existential.derivedExistentialType
 
 /** The capture checker */
 object CheckCaptures:
@@ -770,6 +771,8 @@ class CheckCaptures extends Recheck, SymTransformer:
           // can happen for curried constructors if instantiate of a previous step
           // added capture set to result.
           augmentConstructorType(parent, initCs ++ refs)
+        case core @ Existential(boundVar, core1) =>
+          core.derivedExistentialType(augmentConstructorType(core1, initCs))
         case _ =>
           val (refined, cs) = addParamArgRefinements(core, initCs)
           refined.capturing(cs)