ANTLR installation corrupted; ANTLR messages format file +

Error message

ANTLR installation corrupted; ANTLR messages format file  + formatName + .stg incomplete

What it means

Error "ANTLR installation corrupted; ANTLR messages format file + formatName + .stg incomplete" thrown in antlr/antlr4.

Source

Thrown at tool/src/org/antlr/v4/tool/ErrorManager.java:258

				loadedFormat = new STGroupFile(url, "UTF-8", '<', '>');
				loadedFormat.load();

				loadedFormats.put(formatName, loadedFormat);
			}
		}

		this.formatName = formatName;
		this.format = loadedFormat;

		if (!initSTListener.errors.isEmpty()) {
			rawError("ANTLR installation corrupted; can't load messages format file:\n" +
					initSTListener.toString());
			panic();
		}

		boolean formatOK = verifyFormat();
		if (!formatOK && formatName.equals("antlr")) {
			rawError("ANTLR installation corrupted; ANTLR messages format file " + formatName + ".stg incomplete");
			panic();
		}
		else if (!formatOK) {
			setFormat("antlr"); // recurse on this rule, trying the default message format
		}
	}

    /** Verify the message format template group */
    protected boolean verifyFormat() {
        boolean ok = true;
        if (!format.isDefined("location")) {
            System.err.println("Format template 'location' not found in " + formatName);
            ok = false;
        }
        if (!format.isDefined("message")) {
            System.err.println("Format template 'message' not found in " + formatName);
            ok = false;
        }

View on GitHub (pinned to 7d5770395b)

Solutions

Reinstall the ANTLR tool; the named messages format .stg file is incomplete or truncated.
Restore the original .stg files from the ANTLR distribution matching your tool version.
If the file was edited locally, revert it to the released version.

Example fix

// re-download the antlr-4.x-complete.jar for your version and replace the corrupted one

When it happens

Trigger: The loaded messages format .stg file is missing required templates (incomplete).

Common situations: Reinstall ANTLR; ensure the complete messages .stg ships inside the tool jar.

AI-assisted analysis of antlr/antlr4@7d5770395b (2026-08-14). Data as JSON: /api/errors/25acbe355fea9e4e. Report an issue: GitHub.