Add test

Author: odersky

tests/neg-custom-args/conditionalWarnings.scala

@@ -0,0 +1,14 @@
+
+// run with -deprecation -Xfatal-warnings
+object Test {
+  @deprecated def foo = ???
+
+  implied for Conversion[String, Int] = _.length
+
+  foo    // error
+
+  val x: Int = "abc"
+    // OK, since -feature warnings are not enabled.
+    // The program compiles with final line
+    // there were 1 feature warning(s); re-run with -feature for details
+}