SI-9946 don't null field in lazy accessors that turn out to be live

If a non-transient lazy val is the only user of a private field in
a class, the field is nulled out at the end of the lazy initializer.
This is tested in the existing test `run/lazy-leaks.scala`.

The analysis of which fields could be nulled out was recently moved
from `mixin` to the new `fields` phase. This introduced a regression
as a reference from an inner- or companion-classes had not yet
been processed by `explicitouter` to publicise private fields.

This commit delays the analysis to mixin (after explicit outer has
done its work.)

Navigating from `foo$lzycompute()` to `foo()` to `foo` is a little
dirty now. I'm not sure whether there is a more robust way to
structure things.

2 files changed, 22 insertions, 0 deletions

diff --git a/test/files/run/t9946b.scala b/test/files/run/t9946b.scala
new file mode 100644
index 0000000000..ac102a38f7
--- /dev/null
+++ b/test/files/run/t9946b.scala
@@ -0,0 +1,12 @@
+class Test(private val x: String) {
+  lazy val y = x.reverse
+}
+object Test {
+  def getX(t: Test) = t.x
+  def main(args: Array[String]): Unit = {
+    val t = new Test("foo")
+    assert(t.y == "oof", t.y)
+    assert(t.x == "foo", t.x)
+  }
+}
+
diff --git a/test/files/run/t9946c.scala b/test/files/run/t9946c.scala
new file mode 100644
index 0000000000..f9fe68d48f
--- /dev/null
+++ b/test/files/run/t9946c.scala
@@ -0,0 +1,10 @@
+class Test(private[this] val x: String) {
+  lazy val y = x.reverse
+}
+object Test {
+  def main(args: Array[String]): Unit = {
+    val t = new Test("foo")
+    assert(t.y == "oof", t.y)
+  }
+}
+