From 02533edc8c1e795f45b90c87bc1fbb6ad8004dab Mon Sep 17 00:00:00 2001
From: odersky <odersky@gmail.com>
Date: Thu, 18 Apr 2024 13:38:00 +0200
Subject: [PATCH] Fix overloaded default methods test in RefChecks

It used `cls.info` instead of `cls.thisType`, which caused symbols
accessible only through the self type of `cls` to be forgotten.

Fixes #18555
---
 .../src/dotty/tools/dotc/typer/RefChecks.scala     |  2 +-
 tests/pos/i18555.scala                             | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i18555.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
index 1397b05ec3b5..cdfd137e5661 100644
--- a/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
+++ b/compiler/src/dotty/tools/dotc/typer/RefChecks.scala
@@ -52,7 +52,7 @@ object RefChecks {
       }}
 
       for (name <- defaultMethodNames) {
-        val methods = clazz.info.member(name).alternatives.map(_.symbol)
+        val methods = clazz.thisType.member(name).alternatives.map(_.symbol)
         val haveDefaults = methods.filter(_.hasDefaultParams)
         if (haveDefaults.length > 1) {
           val owners = haveDefaults map (_.owner)
diff --git a/tests/pos/i18555.scala b/tests/pos/i18555.scala
new file mode 100644
index 000000000000..84198409370e
--- /dev/null
+++ b/tests/pos/i18555.scala
@@ -0,0 +1,14 @@
+trait GenericCollectionWithCommands {
+  self: PackSupport =>
+
+  def bar(foo: Int = 1): Any = ???
+  def bar(writer: GenericCollectionWithCommands.this.pack.Writer[Any]): Any = ???
+}
+
+trait PackSupport {
+  val pack: SerializationPack
+}
+
+trait SerializationPack {
+  type Writer[A]
+}
\ No newline at end of file