Disallow subtypes of Function1 acting as implicit conversions

The new test `falseView.scala` shows the problem. We might create
an implicit value of some type that happens to be a subtype of Function1.
We might now expect that this gives us an implicit conversion, this
is most often unintended and surprising.

See the comment in Implicits#discardForView for a discussion why
we picked the particular scheme implemented here.

1 files changed, 2 insertions, 1 deletions

diff --git a/tests/run/t8280.scala b/tests/run/t8280.scala
index f433dcc32..1d2c56b85 100644
--- a/tests/run/t8280.scala
+++ b/tests/run/t8280.scala
@@ -37,7 +37,8 @@ object Moop1 {
     implicit object f1 extends (Int => String) { def apply(x: Int): String = "Int" }
     implicit val f2: Long => String = _ => "Long"
 
-    println(5: String)
+    //println(5: String)
+      // This picked f1 before, but is now disallowed since subtypes of functions are no longer implicit conversions
   }
 }