Merge pull request #12060 from dotty-staging/fix-fix-#8276-2

Add regression test

Author: anatoliykmetyuk

tests/pos/i8276.scala

@@ -0,0 +1,7 @@
+object NOTHING
+
+inline given [A]: Conversion[NOTHING.type, Option[A]] = _ => None
+
+def apply[A](p: Vector[A], o: Option[A] = NOTHING): Unit = ???
+
+def test = apply[String](Vector.empty)