Rust Programming By Example

compile_fail

The compile_fail flag ensures that the given code blocks don't compile. As simple as that. It's mostly used when you're showing bad code and demonstrating why it is bad. For example:

/// ```compile_fail
/// let x = 0;
/// x += 2; // Damn! `x` isn't mutable so you cannot update it...
/// ```

Then you just write a small explanation about what went wrong and show a working example. It's very common in tutorials, to help users understand why it's wrong and how to fix it.

In addition to this, please note that there will be a graphical indication that this block is supposed to fail at compilation:

Figure 10.8

And when you hover over ...