Error code E0744
An unsupported expression was used inside a const context.
Erroneous code example:
#![allow(unused)] fn main() { const _: i32 = { async { 0 }.await }; }
At the moment, .await is forbidden inside a const, static, or const fn.
This may be allowed at some point in the future, but the implementation is not
yet complete. See the tracking issue for async in const fn.