Add code block to code in documentation of List::rebase_onto

[jyn514]

Closes #73676

@bors rollup=always

[rust-highfive]

r? @eddyb

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[jyn514]

Before this change:

After this change:

[eddyb]

Doesn't ```rust require something else to have it ignored as a doctest?

r? @Manishearth

[jyn514]

I noticed a bunch more warnings while documenting this:

Warnings

warning: `[exhaustiveness]` cannot be resolved, ignoring it. --> src/librustc_mir_build/hair/pattern/_match.rs:7:69 | 7 | //! (a) the patterns cover every possible constructor for the type [exhaustiveness] | ^^^^^^^^^^^^^^ cannot be resolved, ignoring | = note: `#[warn(intra_doc_link_resolution_failure)]` on by default = help: to escape `[` and `]` characters, just add '\' before them like `\[` or `\]` warning: `[usefulness]` cannot be resolved, ignoring it. --> src/librustc_mir_build/hair/pattern/_match.rs:8:36 | 8 | //! (b) each pattern is necessary [usefulness] | ^^^^^^^^^^ cannot be resolved, ignoring | = help: to escape `[` and `]` characters, just add '\' before them like `\[` or `\]` warning: could not parse code block as Rust code --> src/librustc_mir_build/hair/pattern/_match.rs:113:9 | 113 | //! For example, the first pattern above initially gives a stack `[(Some(true), _)]`. If we | _________^ 114 | | //! pop the tuple constructor, we are left with `[Some(true), _]`, and if we then pop the 115 | | //! `Some` constructor we get `[true, _]`. If we had popped `None` instead, we would get 116 | | //! nothing back. ... | 149 | | //! Note that the OR-patterns are not always used directly in Rust, but are used to derive the 150 | | //! exhaustive integer matching rules, so they're written here for posterity. | |_________________________________________________________________________________^ | = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: character literal may only contain one codepoint = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: \u{2260} = note: error from rustc: unterminated character literal warning: could not parse code block as Rust code --> src/librustc_mir_build/hair/pattern/_match.rs:179:9 | 179 | //! For example, if `P` is: | _________^ 180 | | //! [ 181 | | //! [Some(true), _], 182 | | //! [None, 0], ... | 229 | | //! `U(P, p) := U(P, (r_1, p_2, .., p_n)) 230 | | //! || U(P, (r_2, p_2, .., p_n))` | |____________________________________________________^ | = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: \u{2203} = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` = note: error from rustc: unknown start of token: ` warning: 4 warnings emitted 

Are these tracked anywhere? Some of those look like broken links.

cc @GuillaumeGomez

[jyn514]

Doesn't ```rust require something else to have it ignored as a doctest?

Oh good point, I'll change it to ignore.

[Manishearth]

@bors r+ rollup=always

[bors]

📌 Commit d279b3c has been approved by Manishearth

[Manishearth]

@jyn514 I don't think these are tracked, but feel free to fix them!

[GuillaumeGomez]

They're not tracked for the moment until we have the intra-doc links stabilized. I definitely plan to deny this warning as soon as it's stable. :)