In particular, it can happen if you forgot the closing bracket of a register
constraint (see issue #51430):
```compile_fail,E0668
-#![feature(asm)]
+#![feature(llvm_asm)]
fn main() {
let rax: u64;
unsafe {
- asm!("" :"={rax"(rax));
+ llvm_asm!("" :"={rax"(rax));
println!("Accumulator is: {}", rax);
}
}