Just like this flag name states, ignore makes the block code ignored. As simple as that. It'll still get the Rust syntax color once rendered in the documentation. For example:
/// ```ignore /// let x = 0; /// ```
However, once rendered, it'll have a graphical notification about the fact that this block code isn't tested:
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Figure 10.6
And when you hover over the sign:
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Figure 10.7
Now let's continue with compile_fail!