#![no_main] #![no_std] extern crate cortex_m_rt; extern crate panic_halt; use cortex_m_rt::{entry, exception}; #[entry] fn foo() -> ! { loop {} } #[exception] fn SysTick() -> u32 { //~^ ERROR `#[exception]` handlers other than `DefaultHandler` and `HardFault` must have signature `[unsafe] fn() [-> !]` 0 }