Attempt to convert OCSP Request types to GATs

This does currently work because GATs cause a type to be invariant

src/rust/cryptography-x509/src/common.rs

@@ -267,6 +267,9 @@ impl<T: asn1::SimpleAsn1Writable, U: asn1::SimpleAsn1Writable> asn1::SimpleAsn1W
 }
 
 pub trait Asn1Operation {
+    type SequenceOf<'a, T>
+    where
+        T: 'a;
     type SequenceOfVec<'a, T>
     where
         T: 'a;
@@ -280,6 +283,10 @@ pub struct Asn1Read;
 pub struct Asn1Write;
 
 impl Asn1Operation for Asn1Read {
+    type SequenceOf<'a, T>
+        = asn1::SequenceOf<'a, T>
+    where
+        T: 'a;
     type SequenceOfVec<'a, T>
         = asn1::SequenceOf<'a, T>
     where
@@ -291,6 +298,10 @@ impl Asn1Operation for Asn1Read {
     type OwnedBitString<'a> = asn1::BitString<'a>;
 }
 impl Asn1Operation for Asn1Write {
+    type SequenceOf<'a, T>
+        = asn1::SequenceOfWriter<'a, T>
+    where
+        T: 'a;
     type SequenceOfVec<'a, T>
         = asn1::SequenceOfWriter<'a, T, Vec<T>>
     where

src/rust/cryptography-x509/src/ocsp_req.rs

@@ -2,19 +2,17 @@
 // 2.0, and the BSD License. See the LICENSE file in the root of this repository
 // for complete details.
 
+use crate::common::Asn1Operation;
 use crate::{common, extensions, name};
 
 #[derive(asn1::Asn1Read, asn1::Asn1Write)]
-pub struct TBSRequest<'a> {
+pub struct TBSRequest<'a, Op: Asn1Operation> {
     #[explicit(0)]
     #[default(0)]
     pub version: u8,
     #[explicit(1)]
     pub requestor_name: Option<name::GeneralName<'a>>,
-    pub request_list: common::Asn1ReadableOrWritable<
-        asn1::SequenceOf<'a, Request<'a>>,
-        asn1::SequenceOfWriter<'a, Request<'a>>,
-    >,
+    pub request_list: Op::SequenceOf<'a, Request<'a>>,
     #[explicit(2)]
     pub raw_request_extensions: Option<extensions::RawExtensions<'a>>,
 }
@@ -35,8 +33,8 @@ pub struct CertID<'a> {
 }
 
 #[derive(asn1::Asn1Read, asn1::Asn1Write)]
-pub struct OCSPRequest<'a> {
-    pub tbs_request: TBSRequest<'a>,
+pub struct OCSPRequest<'a, Op: Asn1Operation> {
+    pub tbs_request: TBSRequest<'a, Op>,
     // Parsing out the full structure, which includes the entirety of a
     // certificate is more trouble than it's worth, since it's not in the
     // Python API.

src/rust/src/x509/ocsp_req.rs

@@ -2,20 +2,22 @@
 // 2.0, and the BSD License. See the LICENSE file in the root of this repository
 // for complete details.
 
+use cryptography_x509::common::{Asn1Read, Asn1Write};
 use cryptography_x509::ocsp_req::{self, OCSPRequest as RawOCSPRequest};
-use cryptography_x509::{common, oid};
+use cryptography_x509::oid;
 use pyo3::types::{PyAnyMethods, PyListMethods};
 
 use crate::asn1::{big_byte_slice_to_py_int, oid_to_py_oid, py_uint_to_big_endian_bytes};
 use crate::error::{CryptographyError, CryptographyResult};
 use crate::x509::{extensions, ocsp};
 use crate::{exceptions, types, x509};
 
+type ReadRawOCSPRequest<'a> = RawOCSPRequest<'a, Asn1Read>;
 self_cell::self_cell!(
     struct OwnedOCSPRequest {
         owner: pyo3::Py<pyo3::types::PyBytes>,
         #[covariant]
-        dependent: RawOCSPRequest,
+        dependent: ReadRawOCSPRequest,
     }
 );
 
@@ -26,14 +28,7 @@ pub(crate) fn load_der_ocsp_request(
 ) -> CryptographyResult<OCSPRequest> {
     let raw = OwnedOCSPRequest::try_new(data, |data| asn1::parse_single(data.as_bytes(py)))?;
 
-    if raw
-        .borrow_dependent()
-        .tbs_request
-        .request_list
-        .unwrap_read()
-        .len()
-        != 1
-    {
+    if raw.borrow_dependent().tbs_request.request_list.len() != 1 {
         return Err(CryptographyError::from(
             pyo3::exceptions::PyNotImplementedError::new_err(
                 "OCSP request contains more than one request",
@@ -60,7 +55,6 @@ impl OCSPRequest {
             .borrow_dependent()
             .tbs_request
             .request_list
-            .unwrap_read()
             .clone()
             .next()
             .unwrap()
@@ -211,13 +205,11 @@ pub(crate) fn create_ocsp_request(
         req_cert,
         single_request_extensions: None,
     }];
-    let ocsp_req = ocsp_req::OCSPRequest {
+    let ocsp_req = ocsp_req::OCSPRequest::<Asn1Write> {
         tbs_request: ocsp_req::TBSRequest {
             version: 0,
             requestor_name: None,
-            request_list: common::Asn1ReadableOrWritable::new_write(asn1::SequenceOfWriter::new(
-                &reqs,
-            )),
+            request_list: asn1::SequenceOfWriter::new(&reqs),
             raw_request_extensions: extensions,
         },
         optional_signature: None,