Depend on a no_std compatible version of chrono

[robomancer-or]

I'm running into a dependency conflict where I can't depend on uom because it depends on num-traits, which has been made no_std compatible since the most recent version of chrono. The problem is, the released version of chrono depends on a conflicting version of num-traits that requires std. Why cargo can't sort out conflicts of this sort is beyond me, but since it can't, would cortex-m-rt switching to the github version of chrono be permissible (at least until chrono gets their act together and cuts a no_std compatible release)?

To recreate the problem for yourself, all you have to do is start a blank no_std library project, add a dep for

uom = { git = "https://github.com/iliekturtles/uom", branch = "dev-num-std", default-features=false, features =["si", "f32"] }

verify that xargo can build it, then add a dep for cortex-m-rt = "*" and try to build again

[hannobraun]

would cortex-m-rt switching to the github version of chrono be permissible (at least until chrono gets their act together and cuts a no_std compatible release)?

I'd like to note that crates.io doesn't accept crates that depend on git repositories, so switching to chrono's GitHub version would effectively block new versions of cortex-m-rt from being released.

[robomancer-or]

...Oh, I definitely didn't realize that, yeah, that's definitely not worth it!

[skierpage]

https://crates.io/crates/chrono is now at 0.4.1 which is no_std compatible. \o/?

[whitequark]

Note that because of rust-lang/cargo#4866 it is not enough for chrono to support no_std to handle every case. Dropping it is the right approach.