UFile (package = ) [public class ReturnMinusX {...]
    UClass (name = ReturnMinusX) [public class ReturnMinusX {...}]
        UMethod (name = foo) [public static fun foo() : int {...}]
            UBlockExpression [{...}] = Nothing
                UDeclarationsExpression [var x: int = 42] = Undetermined
                    ULocalVariable (name = x) [var x: int = 42]
                        ULiteralExpression (value = 42) [42] = 42
                UReturnExpression [return -x] = Nothing
                    UPrefixExpression (operator = -) [-x] = -42 (depending on: (var x = 42))
                        USimpleNameReferenceExpression (identifier = x) [x] = (var x = 42)
