SI-7007 Test case shows we disallow premature `this` access

Rather than the old behaviour, which compiled successfully
but led us into the jaws of a LinkageError.

Related to SI-6666.

2 files changed, 21 insertions, 0 deletions

diff --git a/test/files/neg/t7007.check b/test/files/neg/t7007.check
new file mode 100644
index 0000000000..e22ecb9e4e
--- /dev/null
+++ b/test/files/neg/t7007.check
@@ -0,0 +1,7 @@
+t7007.scala:5: error: Implementation restriction: <$anon: A => B> requires premature access to class Crash.
+  def this(a: Seq[A]) = this(a.collect{ case b: B => b}, a.collect{ case b: B => b})
+                                      ^
+t7007.scala:5: error: Implementation restriction: <$anon: A => B> requires premature access to class Crash.
+  def this(a: Seq[A]) = this(a.collect{ case b: B => b}, a.collect{ case b: B => b})
+                                                                  ^
+two errors found
diff --git a/test/files/neg/t7007.scala b/test/files/neg/t7007.scala
new file mode 100644
index 0000000000..e41dccf550
--- /dev/null
+++ b/test/files/neg/t7007.scala
@@ -0,0 +1,14 @@
+class A
+class B extends A
+
+class Crash(b1: Seq[B], b2: Seq[B]) {
+  def this(a: Seq[A]) = this(a.collect{ case b: B => b}, a.collect{ case b: B => b})
+}
+
+object Main extends App {
+
+  // runtime exception with either constructor
+  val c1 = new Crash(Seq(new B, new B))
+  val c2 = new Crash(Seq(new B), Seq(new B))
+
+}