Migrate to Rust 2021 Edition

[idavis]

With the release of Rust 1.56, the 2021 Rust Edition has been available. The there is a migration guide to new edition.

[divshacker]

Hey, I am interested in working on this issue. I have done a try updating the new version of rust but facing some errors.

• cargo fix --edition works but throws a error

  process didn't exit successfully: `/home/divshacker/pyqir/target/debug/build/llvm-ir-c75243ba21a4165f/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'llvm-ir: Please select an LLVM version using a Cargo feature.', /home/divshacker/.cargo/registry/src/github.com-1ecc6299db9ec823/llvm-ir-0.8.1/build.rs:22:14
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
  warning: build failed, waiting for other jobs to finish...
  error: build failed 

• Cargo.toml don't have the edition field.

Please help me out by resolving this error.

Thanks

[idavis]

Hi @divshacker, thank you for your interest.

Please take a look at the development guide on how to build PyQIR. The build script must be run prior to using cargo commands. Then you can use the commands in the development section of the docs.

If you want to use an existing installation of LLVM, you can set the environment variables so that the build doesn't have to compile LLVM.

[divshacker]

I have tried to run build.sh but it is exiting every time and not building the LLVM completely. First, I have tested it in my system, then I used docker and created the environment and ran build.sh but still throws error that cargo can't LLVM automatically. I don't know what happens but still this the problem. I think person who have already a working enviornment can run cargo fix --edition to fix this issue, I have tried to build a working environment but fail every time

[idavis]

@divshacker We need the exact command and error that you are getting. Also, cargo fix --edition will not work without the additional feature flags outlined in the documentation I linked to above.