rust-lang/cargo · error

not implemented

Error message

not implemented

What it means

mdman converts Markdown into man-page (troff) format. When it encounters a footnote definition block (Tag::FootnoteDefinition) in the Markdown event stream, it has no man-page equivalent implemented and calls unimplemented!(), which panics with 'not implemented'. Footnotes have no direct troff/man rendering path in this formatter.

Solutions

1. Remove all footnote definitions (`[^id]: ...`) from the Markdown source before passing it to mdman.
2. Inline the footnote text as a regular paragraph or a 'Notes' section in the man page source.
3. If footnote support is required, implement a troff rendering for Tag::FootnoteDefinition in crates/mdman/src/format/man.rs (e.g. emit an .SH NOTES section) instead of unimplemented!().

Example fix

// before
Tag::FootnoteDefinition(_label) => unimplemented!(),
// after
Tag::FootnoteDefinition(_label) => {
    // footnotes are dropped for man output
}

// Before invoking mdman, scan the source for footnote definitions
let src = std::fs::read_to_string(&md_path)?;
if src.lines().any(|l| l.trim_start().starts_with("[^") && l.contains("]:")) {
    anyhow::bail!("source contains footnote definitions unsupported by mdman man output");
}

null

null

When it happens

Trigger: Running mdman to generate a man page from a Markdown source that contains a footnote definition, e.g. `[^1]: some text`. The pulldown-cmark parser emits Tag::FootnoteDefinition and the man formatter hits the unimplemented arm.

Common situations: Authors writing CLI tool docs add footnotes for citations/notes; running `mdman --format man` on such a file crashes. Mirrors of upstream docs that use footnotes also trip this.

Related errors

• not implemented
• artifact-dir was not locked during clean
• target must support `bin`

AI-assisted analysis of rust-lang/cargo@eb98b54bc9 (2026-08-11). Data as JSON: /api/errors/de09039792cfe4dc. Report an issue: GitHub.

Appendix: source

Thrown at crates/mdman/src/format/man.rs:174

                        Tag::Item => {
                            // Note: This uses explicit movement instead of .IP
                            // because the spacing on .IP looks weird to me.
                            // space down, indent 4
                            self.flush();
                            self.output.push_str(".sp\n.RS 4\n");
                            match list.last_mut().expect("item must have list start") {
                                // Ordered list.
                                Some(n) => {
                                    // move left 4, output the list index number, move right 1.
                                    write!(self.output, "\\h'-04' {}.\\h'+01'", n)?;
                                    *n += 1;
                                }
                                // Unordered list.
                                None => self.output.push_str("\\h'-04'\\(bu\\h'+03'"),
                            }
                            suppress_paragraph = true;
                        }
                        Tag::FootnoteDefinition(_label) => unimplemented!(),
                        Tag::Table(alignment) => {
                            // Table start
                            // allbox = draw a box around all the cells
                            // tab(:) = Use `:` to separate cell data (instead of tab)
                            // ; = end of options
                            self.output.push_str(
                                "\n.TS\n\
                                allbox tab(:);\n",
                            );
                            let alignments: Vec<_> = alignment
                                .iter()
                                .map(|a| match a {
                                    Alignment::Left | Alignment::None => "lt",
                                    Alignment::Center => "ct",
                                    Alignment::Right => "rt",
                                })
                                .collect();
                            self.output.push_str(&alignments.join(" "));

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