I write Rust for embedded systems and both effects and linear types would be meaningful improvements. Effects especially: if you have multiple cores in a coherent memory domain AND you run with interrupts enabled, you have to deal with three types of mutex:

- data accessed by multiple cores and interrupt handlers must be modified under a spin lock and with interrupts disabled

- data accessed by multiple cores but not interrupt handlers only needs the spin lock

- data accessed by one core but maybe interrupt handlers only needs to pay for disabling interrupts

Depending on your core and how performance sensitive the code is, the costs of the above can vary significantly. It would be nice to encode these rules in the type system.

(Ordered types might be useful for “critical sections” — that is, areas where interrupts are disabled and the interrupt disablement guard absolutely must be dropped in order.)