New cortex-m-rt doesn't work with Cargo "rename-dependency" feature

[little-arhat]

In 2018 edition instead of extern crate cortex_m_rt as rt one would use Cargo rename-dependency:

[dependencies]
rt = {version = "0.6.2", package='cortex-m-rt'}

cortex_m_rt_macros, however, doesn't respect this and still generates code with extern crate cortex_m_rt.

[japaric]

I haven't been following closely but isn't this a known issue? What does e.g. serde-derive do in the case you rename serde to something else?

[little-arhat]

It seems serde_derive also struggles with renames: https://github.com/serde-rs/serde/issues/953. I think there should be at least mention about this behaviour in the doc as currenaly all example in rust-embedded use extern crate cortex_m_rt as rt, and in 2018 this is done via renames.

[achan1989]

Is this build failure also an example of this issue?