message: cargo fix --edition-idioms for group
diff: -extern crate ff;
  -extern crate rand;
  -extern crate rand_xorshift;
  +
  +
  +
  use ff::{PrimeField, PrimeFieldDecodingError, ScalarEngine, SqrtField};
  use rand::RngCore;
  @@ -180,7 +180,7 @@ impl Error for GroupDecodingError {
  }
  impl fmt::Display for GroupDecodingError {
  - fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
  + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
  match *self {
  GroupDecodingError::CoordinateDecodingError(description, ref err) => {
  write!(f, "{} decoding error: {}", description, err)
  