From 8246cb93486cf6b3b7215aec5ad45ed972d6fee4 Mon Sep 17 00:00:00 2001
From: Matt Bovel <matthieu@bovel.net>
Date: Wed, 16 Jul 2025 13:35:21 +0000
Subject: [PATCH] Use base types to compute classOf args of applyDynamic

As suggested in https://github.com/scala/scala3/issues/11043#issuecomment-820518493

Fixes #11043
---
 compiler/src/dotty/tools/dotc/typer/Dynamic.scala |  2 +-
 tests/pos/i11043.scala                            | 14 ++++++++++++++
 tests/pos/i11043min.scala                         |  5 +++++
 3 files changed, 20 insertions(+), 1 deletion(-)
 create mode 100644 tests/pos/i11043.scala
 create mode 100644 tests/pos/i11043min.scala

diff --git a/compiler/src/dotty/tools/dotc/typer/Dynamic.scala b/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
index 14cc7bf963a6..18ba94260d14 100644
--- a/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Dynamic.scala
@@ -268,7 +268,7 @@ trait Dynamic {
             if tpe.paramInfoss.nestedExists(!TypeErasure.hasStableErasure(_)) then
               fail(i"has a parameter type with an unstable erasure") :: Nil
             else
-              TypeErasure.erasure(tpe).asInstanceOf[MethodType].paramInfos.map(clsOf(_))
+              tpe.paramInfoss.flatten.map(tp => clsOf(tp.baseType(tp.classSymbol)))
           structuralCall(nme.applyDynamic, classOfs).maybeBoxingCast(tpe.finalResultType)
         }
 
diff --git a/tests/pos/i11043.scala b/tests/pos/i11043.scala
new file mode 100644
index 000000000000..955350c71091
--- /dev/null
+++ b/tests/pos/i11043.scala
@@ -0,0 +1,14 @@
+import scala.reflect.Selectable.reflectiveSelectable
+
+object Test {
+  type Runner = { def run(args: Array[String]): Unit }
+
+  def test(args: Array[String], runner: Runner): Unit =
+    runner.run(args)
+
+  def main(args: Array[String]): Unit = {
+    test(Array("foo", "bar"), new {
+      def run(args: Array[String]): Unit = args foreach println
+    })
+  }
+}
diff --git a/tests/pos/i11043min.scala b/tests/pos/i11043min.scala
new file mode 100644
index 000000000000..89b8005387e4
--- /dev/null
+++ b/tests/pos/i11043min.scala
@@ -0,0 +1,5 @@
+import scala.reflect.Selectable.reflectiveSelectable
+
+type Runner = { def run(args: Array[String]): Unit }
+
+def test(runner: Runner): Unit = runner.run(???)