`core::write!` is unusable.

[cgaebel]

core::write! expands to use std::fmt::Arguments::new, which isn't available with no_std. That kinda defeats the point of libcore.

[sfackler]

You can work around it with

mod std {
    pub use core::fmt;
}

[cgaebel]

Thanks.

[aturon]

cc @alexcrichton

[alexcrichton]

It's fine for the libcore definition to be wired to core::foo and then the libstd definition to be wired to std::foo as a fix for the interim.

[steveklabnik]

I believe this was fixed by #18578, please let me know if I'm wrong.