Detect if we are running inside a proc macro?

[frigid vortex]

I have a pub function export which, for a long list of reasons, I would like users of my library to only use inside of proc macros. Is there a way I can detect that we are currently running within a proc macro, and panic if we are not?

[tribal mirage]

you could look for the environment variables that cargo adds to build scripts https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts

[frigid vortex]

thanks, that was what I had in mind actually!

anyone have any idea which env var to look for?

[tribal mirage]

Probably any combination of TARGET, NUM_JOBS, OPT_LEVEL, PROFILE

[floral bluff]

that's not exactly useful

[tribal mirage]

those are the ones that aren't included in the normal files, and are not likely to be on the system

[floral bluff]

oh ah
I thought you would have to be searching for a specific value

I'm mistaken