x509: remove unused NameRelativeToCrlIssuer field

In practice we never examine the `untrusted::Input` field of
a `DistributionPointName::NameRelativeToCrlIssuer` variant. Nightly
clippy is flagging this:

```
error: field `0` is never read
  --> src/x509.rs:89:29
   |
89 |     NameRelativeToCrlIssuer(untrusted::Input<'a>),
   |     ----------------------- ^^^^^^^^^^^^^^^^^^^^
   |     |
   |     field in this variant
   |
help: consider changing the field to be of unit type to suppress this warning while preserving the field numbering, or remove the field
   |
89 |     NameRelativeToCrlIssuer(()),
   |                             ~~
```

This commit switches
`DistributionPointName::NameRelativeToCrlIssuer` to be a variant without
any fields to resolve this finding.

src/cert.rs

@@ -408,7 +408,7 @@ mod tests {
  // We expect the distribution point name to be a sequence of GeneralNames, not a name
  // relative to the CRL issuer.
  let names = match distribution_point_name {
- DistributionPointName::NameRelativeToCrlIssuer(_) => {
+ DistributionPointName::NameRelativeToCrlIssuer => {
  panic!("unexpected name relative to crl issuer")
  }
  DistributionPointName::FullName(names) => names,
@@ -566,12 +566,10 @@ mod tests {
  .expect("missing distribution point name");
 
  // We expect the distribution point name to be a name relative to the CRL issuer.
- match distribution_point_name {
- DistributionPointName::NameRelativeToCrlIssuer(name) => {
- assert!(!name.is_empty());
- }
- DistributionPointName::FullName(_) => panic!("unexpected full name sequence"),
- };
+ assert!(matches!(
+ distribution_point_name,
+ DistributionPointName::NameRelativeToCrlIssuer
+ ));
  }
 
  #[test]
@@ -633,7 +631,7 @@ mod tests {
  .expect("failed to parse distribution point names")
  .expect("missing distribution point name")
  {
- DistributionPointName::NameRelativeToCrlIssuer(_) => {
+ DistributionPointName::NameRelativeToCrlIssuer => {
  panic!("unexpected relative name")
  }
  DistributionPointName::FullName(names) => names,

src/crl/types.rs

@@ -538,7 +538,7 @@ impl<'a> IssuingDistributionPoint<'a> {
  use DistributionPointName::*;
  match result.names() {
  Ok(Some(FullName(_))) => Ok(result),
- Ok(Some(NameRelativeToCrlIssuer(_))) | Ok(None) => {
+ Ok(Some(NameRelativeToCrlIssuer)) | Ok(None) => {
  Err(Error::UnsupportedCrlIssuingDistributionPoint)
  }
  Err(_) => Err(Error::MalformedExtensions),
@@ -944,7 +944,7 @@ mod tests {
  .expect("failed to parse distribution point names")
  .expect("missing distribution point name");
  let uri = match dp_name {
- DistributionPointName::NameRelativeToCrlIssuer(_) => {
+ DistributionPointName::NameRelativeToCrlIssuer => {
  panic!("unexpected relative dp name")
  }
  DistributionPointName::FullName(general_names) => {

src/x509.rs

@@ -86,7 +86,7 @@ pub(crate) fn remember_extension(
 /// [^1]: <https://datatracker.ietf.org/doc/html/rfc5280#section-4.2.1.13>
 pub(crate) enum DistributionPointName<'a> {
  /// The distribution point name is a relative distinguished name, relative to the CRL issuer.
- NameRelativeToCrlIssuer(untrusted::Input<'a>),
+ NameRelativeToCrlIssuer,
  /// The distribution point name is a sequence of [GeneralName] items.
  FullName(DerIterator<'a, GeneralName<'a>>),
 }
@@ -102,9 +102,7 @@ impl<'a> FromDer<'a> for DistributionPointName<'a> {
  let (tag, value) = der::read_tag_and_get_value(reader)?;
  match tag {
  FULL_NAME_TAG => Ok(DistributionPointName::FullName(DerIterator::new(value))),
- NAME_RELATIVE_TO_CRL_ISSUER_TAG => {
- Ok(DistributionPointName::NameRelativeToCrlIssuer(value))
- }
+ NAME_RELATIVE_TO_CRL_ISSUER_TAG => Ok(DistributionPointName::NameRelativeToCrlIssuer),
  _ => Err(Error::BadDer),
  }
  }