Test for #12945

Author: odersky

tests/pos/i12945/A_1.scala

@@ -0,0 +1,10 @@
+opaque type Lie[W <: Int] = Int
+object Lie:
+  trait TC[-T]:
+    type Out
+  object TC:
+    given [W <: Int]: TC[Lie[W]] with
+      type Out = W
+
+val x  = summon[Lie.TC[Lie[7]]]
+val works = summon[x.Out =:= 7]

tests/pos/i12945/B_2.scala

@@ -0,0 +1,3 @@
+object Test:
+  val x  = summon[Lie.TC[Lie[7]]]
+  val fails = summon[x.Out =:= 7]