Compiler suggesting non-existant flag

When compiling some code, I got the lint:

note: this error originates in the attribute macro `axum::debug_handler` (in Nightly builds, run with -Z macro-backtrace for more info)

but when executing cargo -Z help with the nighly toolchain the flag doesn't show up. Is this a problem in the compiler that I should report, or is it a problem on my side?

Should be a flag for rustc, not cargo. I’m not 100% certain off the top of my head what the proper way to set this one for a cargo invocation is, but you could try e.g. via setting the RUSTFLAGS environment variable.

Edit: This StackOverflow answer seems to agree with my guess here, so at least for Linux, the syntax on the command line would be to call something like “RUSTFLAGS="-Z macro-backtrace" cargo +nightly check” (or feel free to use other subcommands like build or run; leave out the +nightly if it’s already default anyways; etc…).

1 Like

That fix it, thanks!

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