SI-6666 Restrict hidden `this` access in self/super calls.

Detect when classes (user authored or compiler generated)
local to a self or super constructor argument would require
premature access to the in-construction instance.

The same restriction applies for classes and objects; for objects,
the premature access would result in a null via MODULE$ field.

A residual error has been lodged as SI-6997.

I'd like to remove calls to `Symbol#outerClass` (which relies on
the flaky flag INCONSTRUCTOR, see my comments in the JIRA issue
for more discussion) from `LambdaLift` and `ExplicitOuter`, and
instead use the stack of active self/super calls to know when to
skip an enclosing class. That will obviate that flag.

1 files changed, 132 insertions, 0 deletions

diff --git a/test/files/neg/t6666.scala b/test/files/neg/t6666.scala
new file mode 100644
index 0000000000..d37ffaf141
--- /dev/null
+++ b/test/files/neg/t6666.scala
@@ -0,0 +1,132 @@
+class C(a: Any)
+object F {
+  def byname(a: => Any) = println(a)
+  def hof(a: () => Any) = println(a())
+}
+
+class COkay extends C(0) {
+  def this(a: Any) {
+    this()
+    def x = "".toString
+    F.byname(x)
+  }
+}
+
+//
+// The thunk's apply method accesses the MODULE$
+// field before it is set.
+//
+//   0: getstatic #23; //Field O1$.MODULE$:LO1$;
+//   3: invokevirtual #26; //Method O1$.O1$$x$1:()Ljava/lang/String;
+object O1 extends C({
+  def x = "".toString
+  F.byname(x)
+})
+
+// java.lang.NullPointerException
+//   at O2$$anonfun$$init$$1.apply(<console>:11)
+object O2 extends C({
+  lazy val x = "".toString
+  F.byname(x)
+})
+
+// java.lang.NullPointerException
+//   at O3$$anonfun$$init$$1.apply(<console>:11)
+object O3 extends C({
+  def x = "".toString
+  F.hof(() => x)
+})
+
+// Okay, the nested classes don't get an outer pointer passed,
+// just an extra param for `x: String`.
+object O6 extends C({
+  val x = "".toString
+  F.byname(x); F.hof(() => x); (new { val xx = x }.xx)
+})
+
+
+class C1 extends C({
+  def x = "".toString
+  F.byname(x)
+})
+class C2 extends C({
+  lazy val x = "".toString
+  F.byname(x)
+})
+class C3 extends C({
+  def x = "".toString
+  F.hof(() => x)
+})
+class C4 extends C({
+  def x = "".toString
+  object Nested { def xx = x}
+  Nested.xx
+})
+class C5 extends C({
+  def x = "".toString
+  val y = {
+    object Nested { def xx = x}
+    Nested.xx
+  }
+})
+
+// okay, for same reason as O6
+class C6 extends C({
+  val x = "".toString
+  F.byname(x); F.hof(() => x); (new { val xx = x }.xx)
+})
+
+class C11(a: Any) {
+  def this() = {
+    this({
+     def x = "".toString
+      F.byname(x)
+    })
+  }
+}
+
+// Crashes earlier in lazyVals.
+// class C12(a: Any) {
+//   def this() = {
+//     this({
+//       lazy val x = "".toString
+//       F.byname(x)
+//     })
+//   }
+// }
+
+class C13(a: Any) {
+  def this() = {
+    this({
+      def x = "".toString
+      F.hof(() => x)
+    })
+  }
+}
+
+class C14(a: Any) {
+  def this() = {
+    this({
+      def x = "".toString
+      object Nested { def xx = x}
+      Nested.xx
+    })
+  }
+}
+
+class C15(a: Any) {
+  def this() = {
+    this({
+      def x = "".toString
+      val y = {
+        object Nested { def xx = x}
+        Nested.xx
+      }
+    })
+  }
+}
+
+class COuter extends C({
+  def foo = 0
+  class CInner extends C({foo})
+})
\ No newline at end of file