test: add in a regression test for #15913

[skip community_build]

closes #15913

Author: ckipp01

tests/run/i15913.scala

@@ -0,0 +1,20 @@
+// https://github.com/lampepfl/dotty/issues/15913
+
+class injector[F]
+
+object injectorFactory {
+  def apply[F](overrides: String*): injector[F] = new injector[F]
+
+  def apply[F](
+    bootstrapActivation: Int = ???,
+    overrides: Seq[String] = Seq.empty,
+  ): injector[F] = new injector[F]
+}
+
+object Test extends App {
+  println(
+    injectorFactory[String](
+      bootstrapActivation = 0
+    )
+  )
+}