Downwards comparisons for implicit search and overloading resolution

Compare selected contravariant arguments as if they were covariant.
Which ones is explained in the doc comment for method `isAsSpecificValueType`
in Applications.scala.

This has the same motivation than what @paulp proposed around 2012. The solution is a bit
different from the one proposed then because it only affects top-level parameters.

1 files changed, 8 insertions, 0 deletions

diff --git a/tests/pos-scala2/t2030.scala b/tests/pos-scala2/t2030.scala
new file mode 100644
index 000000000..cbd62baba
--- /dev/null
+++ b/tests/pos-scala2/t2030.scala
@@ -0,0 +1,8 @@
+import scala.collection.immutable._
+
+object Test extends dotty.runtime.LegacyApp {
+  val res0 = TreeSet(1, 2, 3, 4, 5, 6)
+  val res1 = res0.map(x => x)
+  println(res0.toList == res1.toList)
+  println(res1.getClass)
+}