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, 7 insertions, 1 deletions

diff --git a/test/files/neg/t4851.check b/test/files/neg/t4851.check
index 8011350f23..9633fdffed 100644
--- a/test/files/neg/t4851.check
+++ b/test/files/neg/t4851.check
@@ -40,4 +40,10 @@ S.scala:10: error: Adapting argument list by inserting (): this is unlikely to b
  after adaptation: new J2((): Unit)
   val z2 = new J2()
            ^
-7 errors found
+S.scala:14: error: Adapting argument list by creating a 3-tuple: this may not be what you want.
+        signature: Test.anyId(a: Any): Any
+  given arguments: 1, 2, 3
+ after adaptation: Test.anyId((1, 2, 3): (Int, Int, Int))
+  val w1 = anyId(1, 2 ,3)
+                ^
+8 errors found