Add tests for infix types with wildcard parameters

Author: cswinter

tests/pos/wildcardInInfixType.scala

@@ -0,0 +1,9 @@
+object wildcardInInfixType {
+
+  val useless: _ => _ = (x: Int) => 1
+
+  val pointless: (_ <: Int) => _ = (x: Int) => 1
+
+  val answer: Int Either _ = Left(42)
+}
+