macro_rules! unwrap_err {
($res:expr) => { ... };
}
Expand description
Gets the value in the Err
variant.
§Panics
This panics if $res
is an Ok
, including the debug-formatted value in the panic message.
§Example
use const_panic::unwrap_err;
type Res = Result<u32, &'static str>;
const ERR: &str = unwrap_err!(Res::Err("this is an error"));
assert_eq!(ERR, "this is an error");
§Error
This is what the compile-time error looks like when attempting to unwrap an Ok
:
error[E0080]: evaluation of constant value failed
--> src/macros/unwrapping.rs:174:19
|
8 | const ERR: &str = unwrap_err!(Res::Ok(1234));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at '
invoked `unwrap_err` macro with an `Ok` value: 1234', src/macros/unwrapping.rs:8:19
|