As a (late) part of the #rust2020 request, I wanted to talk about one of the paper-cuts that has become decently problematic for new and experienced users of Embedded Rust:
The size costs of formatting in Rust today are unreasonably expensive for users of Rust on bare metal embedded systems.
In particular there are two root issues I can see:

Out of the box formatting machinery, including format!(), write!(), and panic!() in Rust is not program space efficient
More problematically, there is no way to change or opt-out of this cost, and it can show up in unexpected places that are outside of developer control

To be clear: I don't think that these issues are a failing of the language, but rather a sign of growth. The current formatting solution has managed to work without issue for most people (and is still okay-ish in edge cases like embedded) for the better part of 4 years. However as we push Rust to more use cases, the language will need to adapt if it would like to fill into these spaces.
This post aims to…