Regression tests (scala#22521)

Tests for scala#19413, scala#20070 and scala#23122

Author: som-snytt

tests/neg/i19413.scala

@@ -0,0 +1,14 @@
+
+import hello.bla.* // error
+
+//transparent inline def hello: kla.type = kla // ok
+def hello: kla.type = kla
+
+object kla:
+  def ra = ???
+  object bla { val ra1 = 31 }
+
+//import kla.bla.ra1
+
+@main def test = println:
+  ra1

tests/pos/i20070.scala

@@ -0,0 +1,7 @@
+
+trait F[A]
+given F[Int] = new F {}
+def f[A: F] = { (x: A) => x }
+
+@main def test =
+  println(f[Int](1))

tests/warn/i23033.scala

@@ -9,3 +9,5 @@ object Test {
 }
 object Useful:
   given [T](using @unused ec: ExecutionContext): AnyRef with {}
+
+class i23122(@unused param: AnyRef)