SI-6507 do not call .toString on REPL results when :silent is on.

Member handlers used to always call .toString on REPL results, even when
:silent was on, which could force evaluation or cause unwanted side
effects.

This forwards the current value of `printResults` to the member
handlers (through Request) for them to decide what to do when the
results must not be printed.

2 handlers now do not return any extraction code when silent:
 - ValHandler, so that it doesn't call toString on the val
 - Assign, so that it doesn't call toString on the right-hand side
   of the assignement.

1 files changed, 26 insertions, 0 deletions

diff --git a/test/files/run/t6507.check b/test/files/run/t6507.check
new file mode 100644
index 0000000000..336db0aeaf
--- /dev/null
+++ b/test/files/run/t6507.check
@@ -0,0 +1,26 @@
+Type in expressions to have them evaluated.
+Type :help for more information.
+
+scala> 
+
+scala> :silent
+Switched off result printing.
+
+scala> class A { override def toString() = { println("!"); "A" } }
+
+scala> val a = new A
+
+scala> var b: A = new A
+
+scala> b = new A
+
+scala> new A
+
+scala> :silent
+Switched on result printing.
+
+scala> res0
+!
+res1: A = A
+
+scala>