More repl work.

Hardened the repl against a bunch of erroneous conditions. Added a
:reset command which causes the repl to forget everything you have told
it. Added classloader tracing when repl tracing is enabled. :reset is
not that useful in its current form but it's the precursor to something
more interesting. No review.

1 files changed, 57 insertions, 0 deletions

diff --git a/test/files/run/repl-reset.check b/test/files/run/repl-reset.check
new file mode 100644
index 0000000000..652948c63b
--- /dev/null
+++ b/test/files/run/repl-reset.check
@@ -0,0 +1,57 @@
+Type in expressions to have them evaluated.
+Type :help for more information.
+
+scala> 
+
+scala> val x1 = 1
+x1: Int = 1
+
+scala> val x2 = 2
+x2: Int = 2
+
+scala> val x3 = 3
+x3: Int = 3
+
+scala> case class BippyBungus()
+defined class BippyBungus
+
+scala> x1 + x2 + x3
+res0: Int = 6
+
+scala> :reset
+Resetting interpreter state.
+Forgetting this session history:
+
+val x1 = 1
+val x2 = 2
+val x3 = 3
+case class BippyBungus()
+x1 + x2 + x3
+
+Forgetting all expression results and named terms: BippyBungus, x1, x2, x3
+Forgetting defined types: BippyBungus
+
+scala> x1 + x2 + x3
+<console>:8: error: not found: value x1
+              x1 + x2 + x3
+              ^
+
+scala> val x1 = 4
+x1: Int = 4
+
+scala> new BippyBungus
+<console>:8: error: not found: type BippyBungus
+              new BippyBungus
+                  ^
+
+scala> class BippyBungus() { def f = 5 }
+defined class BippyBungus
+
+scala> { new BippyBungus ; x1 }
+res2: Int = 4
+
+scala> :javap BippyBungus
+Compiled from "<console>"public class BippyBungus extends java.lang.Object implements scala.ScalaObject{    public int f();    public BippyBungus();}
+scala> 
+
+scala>