Why must this crate compile with nightly?

[Nicholas-Baron]

I find it strange that a crate can be installed with stable, but must use nightly to run.

Trying to compile with stable gives the following error

the option Z is only accepted on the nightly compiler

Has the source of this error been tracked down? I do not see anything in this repository explicitly so it must be in one of the dependencies.

[qryxip]

That message comes from rustc.

$ rustc +stable -Z aaaaaaaaaa /dev/null
error: the option `Z` is only accepted on the nightly compiler

The reason is because cargo-udeps relies on the -Z save-analysis option, which is only available on nightly. So cargo-udeps itself does not need to be compiled with nightly toolchains.

cargo-udeps/src/lib.rs

Line 608 in 82b1ede

cmd.arg("-Z").arg("save-analysis");

[est31]

Yeah you can switch between save-analysis and binary-depinfo backends but both currently require nightly. save-analysis will likely be removed eventually but binary-depinfo might get stabilized. Maybe a backend based on the unused dependency warning can be added, that one would work on stable, cc #70.