#![feature(unboxed_closures)] #![feature(const_vec_new)] #![feature(fn_traits)] pub struct PackBytes; static mut HANDLERS: Vec<Box<dyn FnMut<&mut PackBytes, Output=()>>> = Vec::new(); fn main() { let mut pack = PackBytes; unsafe { HANDLERS[0].as_mut().call_mut(&mut pack); } } 

error[E0597]: `pack` does not live long enough --> src/main.rs:15:35 | 15 | HANDLERS[0].as_mut().call_mut(&mut pack); } | ------------------------------^^^^^^^^^- | | | | | borrowed value does not live long enough | argument requires that `pack` is borrowed for `'static` 16 | } | - `pack` dropped here while still borrowed 

#![feature(unboxed_closures)] #![feature(const_vec_new)] #![feature(fn_traits)] pub struct PackBytes; static mut HANDLERS: Vec<Box<dyn for<'a> FnMut<&'a mut PackBytes, Output=()>>> = Vec::new(); fn main() { let mut pack = PackBytes; unsafe { HANDLERS[0].as_mut().call_mut(&mut pack); } } 

error: internal compiler error: src/librustc_codegen_llvm/abi.rs:433: argument to function with "rust-call" ABI is not a tuple thread 'rustc' panicked at 'Box<Any>', src/librustc_errors/lib.rs:590:9 note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace. error: aborting due to previous error note: the compiler unexpectedly panicked. this is a bug. note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports note: rustc 1.33.0-nightly (b92552d55 2019-01-06) running on x86_64-unknown-linux-gnu note: compiler flags: -C codegen-units=1 -C debuginfo=2 --crate-type bin note: some of the compiler flags provided by cargo are hidden