Warn on selection of vals from DelayedInit subclasses.

Which are likely to yield null, if the program didn't start.

This is a common source of confusion for people new to
the language, as was seen during the Coursera course.

The test case shows that the usage pattern within Specs2
won't generate these warnings.

1 files changed, 10 insertions, 0 deletions

diff --git a/test/files/neg/delayed-init-ref.check b/test/files/neg/delayed-init-ref.check
new file mode 100644
index 0000000000..42ccabed1b
--- /dev/null
+++ b/test/files/neg/delayed-init-ref.check
@@ -0,0 +1,10 @@
+delayed-init-ref.scala:17: error: Selecting value vall from object O, which extends scala.DelayedInit, is likely to yield an uninitialized value
+  println(O.vall)     // warn
+            ^
+delayed-init-ref.scala:19: error: Selecting value vall from object O, which extends scala.DelayedInit, is likely to yield an uninitialized value
+  println(vall)       // warn
+          ^
+delayed-init-ref.scala:40: error: Selecting value foo from trait UserContext, which extends scala.DelayedInit, is likely to yield an uninitialized value
+    println({locally(()); this}.foo)  // warn (spurious, but we can't discriminate)
+                                ^
+three errors found