Fix #2774: Add regression test

Author: nicolasstucki

tests/pos/i2774.scala

@@ -0,0 +1,12 @@
+object Test {
+  trait T; trait Q
+  val a: given T => given Q => Int = 1
+
+  implied for Q = new Q {}
+  val i1: Int = a given (new T{})
+  implied for T = new T {}
+  val i2: Int =  a
+
+  def a given (t: T) given (q: Q): Int = 1
+
+}