SI-8035 Deprecate automatic () insertion in argument lists

This promotes the () insertion warning from -Ywarn-adapted-args to a
deprecation warning. -Xfuture tunrs it into a compiler error.

Auto tupling remains unchanged for now.

The tests have been fixed the following way:
- Warnings caused by general sloppiness (Try(), Future(), ...) have been
  fixed.
- Warnings which raise interesting questions (x == (), ...) received an
  updated checkfile for now.

1 files changed, 21 insertions, 0 deletions

diff --git a/test/files/neg/t8035-deprecated.check b/test/files/neg/t8035-deprecated.check
new file mode 100644
index 0000000000..01f27e5310
--- /dev/null
+++ b/test/files/neg/t8035-deprecated.check
@@ -0,0 +1,21 @@
+t8035-deprecated.scala:2: warning: Adaptation of argument list by inserting () has been deprecated: this is unlikely to be what you want.
+        signature: GenSetLike.apply(elem: A): Boolean
+  given arguments: <none>
+ after adaptation: GenSetLike((): Unit)
+  List(1,2,3).toSet()
+                   ^
+t8035-deprecated.scala:5: warning: Adaptation of argument list by inserting () has been deprecated: this is unlikely to be what you want.
+        signature: A(x: T): Foo.A[T]
+  given arguments: <none>
+ after adaptation: new A((): Unit)
+  new A
+  ^
+t8035-deprecated.scala:9: warning: Adaptation of argument list by inserting () has been deprecated: leaky (Object-receiving) target makes this especially dangerous.
+        signature: Format.format(x$1: Any): String
+  given arguments: <none>
+ after adaptation: Format.format((): Unit)
+  sdf.format()
+            ^
+error: No warnings can be incurred under -Xfatal-warnings.
+three warnings found
+one error found