Build Fails

[jlpoolen]

git cloned my forked copy (jlpooleen/retina) into /usr/local/src

 cd retina
 cargo build
 ...
   Compiling retina v0.0.1 (/usr/local/src/retina)
error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/client/parse.rs:273:18
    |
273 |                 .split_once(' ')
    |                  ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/client/parse.rs:285:18
    |
285 |                 .split_once(' ')
    |                  ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/client/parse.rs:310:18
    |
310 |                 .split_once('/')
    |                  ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/client/parse.rs:553:18
    |
553 |                 .split_once('=')
    |                  ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/codec/aac.rs:323:14
    |
323 |             .split_once('=')
    |              ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error[E0658]: use of unstable library feature 'str_split_once': newly added
   --> src/codec/h264.rs:472:41
    |
472 |             let (key, value) = p.trim().split_once('=').unwrap();
    |                                         ^^^^^^^^^^
    |
    = note: see issue #74773 <https://github.com/rust-lang/rust/issues/74773> for more information

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0658`.
error: could not compile `retina`

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed
ares /usr/local/src/retina #

Followed suggested explanation of error:

ares /usr/local/src/retina # rustc --explain E0658
#[repr(u128)] // error: use of unstable library feature 'repr128'
enum Foo {
    Bar(u64),
}
```

If you're using a stable or a beta version of rustc, you won't be able to use
any unstable features. In order to do so, please switch to a nightly version of
rustc (by using [rustup]).

If you're using a nightly version of rustc, just add the corresponding feature
to be able to use it:

```
#![feature(repr128)]

#[repr(u128)] // ok!
enum Foo {
    Bar(u64),
}
```

[rustup]: https://rust-lang.github.io/rustup/concepts/channels.html

Here's what I have installed (high watermark from Gentoo repository):

ares /usr/local/src/retina # eix -I rust
[I] app-eselect/eselect-rust
     Available versions:  20200419
     Installed versions:  20200419(16:34:41 02/07/21)
     Homepage:            https://wiki.gentoo.org/wiki/Project:Rust
     Description:         Eselect module for management of multiple Rust versions

[I] dev-lang/rust
     Available versions:  (stable) 1.51.0-r2(stable/1.51)^t ~1.52.1(stable/1.52)^t
       {clippy debug doc miri nightly parallel-compiler rls rustfmt system-bootstrap system-llvm test verify-sig wasm ABI_MIPS="n32 n64 o32" ABI_S390="32 64" ABI_X86="32 64 x32" CPU_FLAGS_X86="sse2" LLVM_TARGETS="AArch64 AMDGPU ARM AVR BPF Hexagon Lanai MSP430 Mips NVPTX PowerPC RISCV Sparc SystemZ WebAssembly X86 XCore"}
     Installed versions:  1.51.0-r2(stable/1.51)^t(22:22:19 05/12/21)(-clippy -debug -doc -miri -nightly -parallel-compiler -rls -rustfmt -system-bootstrap -system-llvm -test -verify-sig -wasm ABI_MIPS="-n32 -n64 -o32" ABI_S390="-32 -64" ABI_X86="64 -32 -x32" CPU_FLAGS_X86="sse2" LLVM_TARGETS="X86 -AArch64 -AMDGPU -ARM -AVR -BPF -Hexagon -Lanai -MSP430 -Mips -NVPTX -PowerPC -RISCV -Sparc -SystemZ -WebAssembly -XCore")
     Homepage:            https://www.rust-lang.org/
     Description:         Systems programming language from Mozilla

[I] virtual/rust
     Available versions:  1.51.0 ~1.52.1 {ABI_MIPS="n32 n64 o32" ABI_S390="32 64" ABI_X86="32 64 x32"}
     Installed versions:  1.51.0(22:23:52 05/12/21)(ABI_MIPS="-n32 -n64 -o32" ABI_S390="-32 -64" ABI_X86="64 -32 -x32")
     Description:         Virtual for Rust language compiler

Found 3 matches
ares /usr/local/src/retina #

ares /usr/local/src/retina # cargo -V
cargo 1.51.0
ares /usr/local/src/retina #

[jlpoolen]

And, just for completeness, I only have one version staged on my system:

ares /usr/local/src/retina # eselect rust list
Available Rust versions:
  [1]   rust-1.51.0 *
ares /usr/local/src/retina #

[scottlamb]

The split_once it's complaining about was introduced in Rust 1.52 (latest stable version).

[jlpoolen]

unmasked virtual/rust and dev-lang/rust in Gentoo in /etc/portage/packages.accept_keywords/rust. Current high watermark for rust in Gentoo is 1.51.[x] :

#
# 6/4/21 jlpoole: required by retina [Moonfire]
#
>=virtual/rust-1.52.1 ~amd64
>=dev-lang/rust-1.52.1 ~amd64

and emerged virutal/rust which brought in rust 1.52.1.

retina successfully compiled.

Also researched if cargo can specify minimum version for rust and determined it cannot -- such a feature is in the Request For Comments phase: https://github.com/rust-lang/rfcs/pull/2495

Thanks.