From cb97c40930d335e0fca38238682d218c3e718bd8 Mon Sep 17 00:00:00 2001
From: Matt Bovel <matthieu@bovel.net>
Date: Mon, 31 Mar 2025 19:50:37 +0000
Subject: [PATCH] Approximate annotated types in `wildApprox`

---
 compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala | 6 ++++++
 tests/pos/annot-default-arg-22839.scala              | 7 +++++++
 2 files changed, 13 insertions(+)
 create mode 100644 tests/pos/annot-default-arg-22839.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index 0cc4aaabfc93..278352ed62f4 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -1017,6 +1017,12 @@ object ProtoTypes {
         paramInfos = tl.paramInfos.mapConserve(wildApprox(_, theMap, seen, internal1).bounds),
         resType = wildApprox(tl.resType, theMap, seen, internal1)
       )
+    case tp @ AnnotatedType(parent, _) =>
+      val parentApprox = wildApprox(parent, theMap, seen, internal)
+      if tp.isRefining then
+        WildcardType(TypeBounds.upper(parentApprox))
+      else
+        parentApprox
     case _ =>
       (if (theMap != null && seen.eq(theMap.seen)) theMap else new WildApproxMap(seen, internal))
         .mapOver(tp)
diff --git a/tests/pos/annot-default-arg-22839.scala b/tests/pos/annot-default-arg-22839.scala
new file mode 100644
index 000000000000..7a983f4d3351
--- /dev/null
+++ b/tests/pos/annot-default-arg-22839.scala
@@ -0,0 +1,7 @@
+package defaultArgBug
+
+class staticAnnot(arg: Int) extends scala.annotation.StaticAnnotation
+class refiningAnnot(arg: Int) extends scala.annotation.RefiningAnnotation
+
+def f1(a: Int, b: Int @staticAnnot(a + a) = 42): Int = b
+def f2(a: Int, b: Int @refiningAnnot(a + a) = 42): Int = b