It does indeed need to be proofread and that is annoying. It seems to me like the author just copy-pasted the completely wrong compiler output. Because in that section, he's trying to show how by having two distinct types for the arguments, the incorrect order would lead to a compiler error, as opposed to the case where both args were of type `bool` (and that this helps you avoid hard-to-spot mistakes at the point of invocation)
I agree LaTeX has it's uses, but... markdown can also do this trivially. See for example the Rust Book [1], and `cargo test` automatically runs example code in markdown doccomments.
