KT-668 Failed to resolve generic parameter

Same lower and upper bounds cause an equality constraint to be created

compiler/testData/checkerWithErrorTypes/quick/regressions/kt688.jet

@@ -0,0 +1,14 @@
+// KT-668 Failed to resolve generic parameter
+open class A()
+open class B() : A() {
+  fun b(): B = B()
+}
+
+
+class C() {
+  fun a<T>(x: fun(T):T, y: T): T {
+    return x(x(y))
+  }
+
+  val x: B = a({it.b()}, B())
+}