Merge pull request #14862 from dotty-staging/test-8424

Regression test for #8424

Author: odersky

tests/pos/i8424.scala

@@ -0,0 +1,9 @@
+
+trait T
+trait U
+
+class Test(x: Any)(using val t: T = ???)(using val u: U = ???, disregard: Any = ???)
+
+object Test {
+  def apply() = new Test(???)
+}