FuelLabs/fuels-rs · error · anyhow::Error

The end of the anchor appears before the beginning. End…

Error message

The end of the anchor appears before the beginning. End anchor: {end:?}. Begin anchor: {begin:?}

What it means

Doc-checking error (scripts/check-docs): an ANCHOR/ANCHOR_END pair with matching names exists in the same file, but the end marker's line number is smaller than the start marker's — the pair is inverted. check_validity_of_anchor_pair rejects pairs where begin.line_no > end.line_no.

Solutions

1. Open the file named in the error and find both markers by line numbers given in the Anchor debug output.
2. Swap the two lines so ANCHOR: <name> precedes ANCHOR_END: <name>.
3. Re-run check-docs; if the file legitimately needs the snippet order reversed, rename one pair instead of swapping.

Example fix

// before
// ANCHOR_END: snippet
fn b() {}
// ANCHOR: snippet
fn a() {}
// after
// ANCHOR: snippet
fn a() {}
// ANCHOR_END: snippet
fn b() {}

let lines: Vec<&str> = src.lines().collect();
let pos = |m: &str| lines.iter().position(|l| l.contains(m));
if let (Some(b), Some(e)) = (pos("ANCHOR: n"), pos("ANCHOR_END: n")) {
    assert!(b < e, "ANCHOR_END appears before ANCHOR");
}

When it happens

Trigger: A file contains ANCHOR_END: x physically above ANCHOR: x — markers swapped during editing, or the 'begin' marker collected from a grep of the file is the lower occurrence while the end sits above it.

Common situations: Hand-editing examples and flipping the marker comments; automated refactors that reorder blocks; duplicate names where start/end got interleaved.

Related errors

• Anchor unused: !
• Couldn't find a matching end anchor for
• No anchor available to satisfy include
• file ` ` not in SUMMARY.md
• when canonicalized gives error \ninclude_file

AI-assisted analysis of FuelLabs/fuels-rs@d9a250a518 (2026-08-16). Data as JSON: /api/errors/d3f089875e6e4426. Report an issue: GitHub.

Appendix: source

Thrown at scripts/check-docs/src/lib.rs:153

        .collect::<Vec<_>>();

    let start_only = pairs.into_iter().map(|(begin, _)| begin).collect();

    (start_only, chain!(errors, additional_errors).collect())
}

pub fn filter_unused_ends<'a>(ends: &'a [Anchor], pairs: &[(Anchor, Anchor)]) -> Vec<&'a Anchor> {
    ends.iter()
        .filter(|end| {
            let end_used_in_pairs = pairs.iter().any(|(_, used_end)| *end == used_end);
            !end_used_in_pairs
        })
        .collect()
}

pub fn check_validity_of_anchor_pair(begin: &Anchor, end: &Anchor) -> Option<anyhow::Error> {
    if begin.line_no > end.line_no {
        Some(anyhow!(
            "The end of the anchor appears before the beginning. End anchor: {end:?}. Begin anchor: {begin:?}"
        ))
    } else {
        None
    }
}

#[derive(Debug, Clone, Hash, Eq, PartialEq)]
pub struct Anchor {
    pub line_no: usize,
    pub name: String,
    pub file: PathBuf,
}

pub fn extract_starts_and_ends(
    text_w_anchors: &str,
) -> anyhow::Result<(Vec<Anchor>, Vec<Anchor>), Error> {
    let apply_regex = |regex: Regex| {

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