Add corner case tests for protected constructor access

Neg tests: new in constructor body, lambda in super args,
transitive parent in super args, direct parent in super args,
mixed visibility constructors.

Pos tests: super calls, inner class super calls, public secondary
constructor in super args.

Author: bracevac

tests/neg/i25442/protected-constructors.scala

@@ -1,3 +1,5 @@
+package protectedCtors
+
 class A protected (x: Int)
 
 // Protected constructor in super call arguments (transitive parent)
@@ -15,3 +17,12 @@ class F protected (x: Int) {
 class G(f: F) extends F(f.hashCode)
 class H extends G(new F())   // ok: public secondary in super args
 class J extends G(new F(1))  // error: protected primary in super args
+
+// new in primary constructor body
+class K extends A(42) {
+  val k = new A(1) // error
+}
+
+// Lambda in super call arguments
+class M(f: () => A) extends A(1)
+class N extends M(() => new A(2)) // error

tests/pos/i25442.scala

@@ -0,0 +1,18 @@
+package protectedCtorsPos
+
+class A protected (x: Int)
+
+// Super calls are allowed
+class B extends A(42)
+
+// Inner class extending protected parent
+class C extends A(42) {
+  class Inner extends A(1)
+}
+
+// Mixed visibility: public secondary constructor is accessible
+class D protected (x: Int) {
+  def this() = this(0)
+}
+class E(d: D) extends D(d.hashCode)
+class F extends E(new D())