gadts1.scala:15: error: type mismatch;
 found   : Test.Double
 required: a
    case NumTerm(n) => c.x = Double(1.0) 
                                   ^
gadts1.scala:20: error: class Cell of type Test.Cell does not take type parameters.
    case Cell[a](x: Int) => c.x = 5
             ^
gadts1.scala:20: error: type mismatch;
 found   : Int(5)
 required: a
    case Cell[a](x: Int) => c.x = 5
                                  ^
gadts1.scala:20: error: Could not typecheck extractor call: case class <none> with arguments List((x @ (_: Int)))
    case Cell[a](x: Int) => c.x = 5
                ^
four errors found