der crate bumps MSRV

[lumag]

Current der crate declares rust version 1.57, however it's not compatible even with 1.63:

$ cargo build
   Compiling der v0.7.0-pre (/home/lumag/Projects/Rust/RustCrypto/formats/der)
error[E0658]: generic associated types are unstable
 --> der/src/referenced.rs:6:5
  |
6 | /     type Borrowed<'a>
7 | |     where
8 | |         Self: 'a;
  | |_________________^
  |
  = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

error[E0658]: where clauses on associated types are unstable
 --> der/src/referenced.rs:6:5
  |
6 | /     type Borrowed<'a>
7 | |     where
8 | |         Self: 'a;
  | |_________________^
  |
  = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

error[E0658]: where clauses on associated types are unstable
  --> der/src/referenced.rs:19:5
   |
19 | /     type Owned: OwnedToRef<Borrowed<'a> = Self>
20 | |     where
21 | |         Self: 'a;
   | |_________________^
   |
   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

error[E0658]: generic associated types are unstable
  --> der/src/referenced.rs:31:5
   |
31 |     type Borrowed<'a> = Option<T::Borrowed<'a>> where T: 'a;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

error[E0658]: where clauses on associated types are unstable
  --> der/src/referenced.rs:31:5
   |
31 |     type Borrowed<'a> = Option<T::Borrowed<'a>> where T: 'a;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #44265 <https://github.com/rust-lang/rust/issues/44265> for more information

For more information about this error, try `rustc --explain E0658`.
error: could not compile `der` due to 5 previous errors

$ rustc --version
rustc 1.63.0

[tarcieri]

Updated in #805

[baloo]

oops, sorry I missed that.

[lumag]

Quite a pity :-( Debian unstable has 1.63, Ubuntu has 1.61.

[tarcieri]

@lumag this is a new release cycle that won't be out for several months and will likely align with another breaking minor release of the RustCrypto traits.

Speaking as a Debian user: stable (i.e. bullseye) has 1.48. This is far too old to build most modern Rust programs. For that reason I use rustup to install rustc/cargo on Debian, rather than relying on the outdated distro packages.

unstable will get to 1.65 before there is a release of this crate or any of the other crates in this repo that depend on it. But IMO that's not a terribly useful data point as stable is what really matters.