`doctest` should not be `opt-in`

BUG

compile_fail should not be ignored on test function.

Actual

compile_fail is ignored on test function.

$ cargo test && echo OK
...
OK

pub fn add(left: usize, right: usize) -> usize {
    left + right
}

#[cfg(test)]
mod tests {
    use super::*;

    /// ```compile_fail
    /// let mut x = 5;
    /// x += 2;
    /// ```
    #[test]
    fn it_works() {
        let result = add(2, 2);
        assert_eq!(result, 4);
    }
}

Expected

compile_fail should not be ignored on test function.

Same as on non-test function.

$ cargo test
...
Test compiled successfully, but it's marked `compile_fail`.
...

/// ```compile_fail
/// let mut x = 5;
/// x += 2;
/// ```
pub fn add(left: usize, right: usize) -> usize {
    left + right
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn it_works() {
        let result = add(2, 2);
        assert_eq!(result, 4);
    }
}

Version

• rustc 1.73.0 (cc66ad468 2023-10-03)

• cargo 1.73.0 (9c4383fb5 2023-08-26)

Reproduce the report with the supplied Rust examples and cargo test, focusing on doctest handling for compile_fail on functions marked with #[test]. Compare this behavior with the non-test function example. Done means the test-function doctest is no longer ignored and reports failure when it compiles successfully despite the compile_fail marker.