SI-6923 Context now buffers warnings as well as errors

Code that was silently typed would not report warnings, even if it
returned a successful result.

This appeared in the following code which didn't show warnings even
with -Ywarn-adapted-args:

    def foo(a: Any) = a; foo(1, 2)

While the following would show the expected warning:

    def foo[A](a: Any) = a; foo(1, 2)

1 files changed, 5 insertions, 0 deletions

diff --git a/test/files/neg/t4851/S.scala b/test/files/neg/t4851/S.scala
index 1550892967..0a442ac7a9 100644
--- a/test/files/neg/t4851/S.scala
+++ b/test/files/neg/t4851/S.scala
@@ -10,6 +10,9 @@ object Test {
   val z2 = new J2()
   val z3 = new J2(())
 
+  def anyId(a: Any) = a
+  val w1 = anyId(1, 2 ,3)
+
   def main(args: Array[String]): Unit = {
     println(x1)
     println(x2)
@@ -19,5 +22,7 @@ object Test {
     println(z1)
     println(z2)
     println(z3)
+
+    println(w1)
   }
 }