microsoft/edit · error

Unexpected GCB={} with InCB={} for U+{:04X} to U+{:04X}

Error message

Unexpected GCB={} with InCB={} for U+{:04X} to U+{:04X}

What it means

Indic_Conjunct_Break (InCB) values other than None/Extend are Linker/Consonant, which the generator assumes always co-occur with GCB=EX/XX (Extend or Other). If an InCB Linker/Consonant range has any other GCB, the assumption behind treating them like extenders fails and it bails.

Source

Thrown at crates/unicode-gen/src/main.rs:836

                // and treat it as an alias of EXTEND, but with the special GB11 properties.
                if cb != ClusterBreak::Other {
                    bail!(
                        "Unexpected GCB={} with ExtPict=Y for U+{:04X} to U+{:04X}",
                        char_attributes.grapheme_cluster_break,
                        range.start(),
                        range.end()
                    );
                }

                cb = ClusterBreak::ExtPic;
            }

            if !matches!(char_attributes.indic_conjunct_break, "None" | "Extend") {
                // If it's not None/Extend, it's Linker/Consonant, and currently
                // all of them are GCB=EX/XX. Since we treat them almost like extenders,
                // we need to revisit our assumptions if this ever changes.
                if !matches!(cb, ClusterBreak::Other | ClusterBreak::Extend) {
                    bail!(
                        "Unexpected GCB={} with InCB={} for U+{:04X} to U+{:04X}",
                        char_attributes.grapheme_cluster_break,
                        char_attributes.indic_conjunct_break,
                        range.start(),
                        range.end()
                    );
                }
                cb = match char_attributes.indic_conjunct_break {
                    "Linker" => ClusterBreak::InCBLinker,
                    "Consonant" => ClusterBreak::InCBConsonant,
                    _ => bail!(
                        "Unrecognized InCB={} for U+{:04X} to U+{:04X}",
                        char_attributes.indic_conjunct_break,
                        range.start(),
                        range.end()
                    ),
                };
            }

View on GitHub (pinned to 826b4c097b)

Solutions

1. Regenerate using a consistent UCD file set from the supported Unicode version.
2. If a new release legitimately changes the co-occurrence, widen the matches! guard and update the extender modeling for InCB.
3. Re-check the source UCD file if the combination looks like data corruption.

Example fix

// before
if !matches!(cb, ClusterBreak::Other | ClusterBreak::Extend) { bail!("Unexpected GCB=... with InCB=...") }
// after
// allow newly observed GCB for InCB Linker/Consonant
if !matches!(cb, ClusterBreak::Other | ClusterBreak::Extend | ClusterBreak::SpacingMark) { bail!(...) }

// ensure GraphemeBreakProperty and IndicConjunctBreak come from the same release
assert_eq!(ucd_version("GraphemeBreakProperty.xml"), ucd_version("IndicConjunctBreak.xml"));

match generate(&ucd_path) {
    Err(e) if e.to_string().contains("with InCB=") => {
        eprintln!("InCB/GCB invariant broken — check Unicode version consistency: {e}");
        std::process::exit(1);
    }
    r => r?,
}

When it happens

Trigger: A UCD release where a Linker/Consonant codepoint carries a GCB value other than Extend or Other; or mismatched UCD files where IndicConjunctBreak and GraphemeBreakProperty data come from different versions.

Common situations: Updating to a newer Unicode version (InCB was introduced in Unicode 15.1) without re-validating the assumptions; mixing GraphemeBreakProperty and IndicConjunctBreak files from different releases.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• Unexpected GCB={} with ExtPict=Y for U+{:04X} to U+{:04X}
• Unrecognized GCB={} for U+{:04X} to U+{:04X}
• Unrecognized InCB={} for U+{:04X} to U+{:04X}
• Unrecognized ea={} for U+{:04X} to U+{:04X}

AI-assisted analysis of microsoft/edit@826b4c097b (2026-09-06). Data as JSON: /api/errors/1940eb78807189ff. Report an issue: GitHub.