public static UUnary create(Kind unaryOp, UExpression expression) {
    checkArgument(
        UNARY_OP_CODES.containsKey(unaryOp), "%s is not a recognized unary operation", unaryOp);
    return new AutoValue_UUnary(unaryOp, expression);
  }
@Test
  public void unaryNegation() {
    assertUnifiesAndInlines("-foo", UUnary.create(Kind.UNARY_MINUS, fooIdent));
  }