What causes "unknown type %s" in golangci/golangci-lint?

Check the goconst settings documentation and use exact accepted values (e.g. 'compositelit', not 'compositeliteral')

unknown type

Error message

unknown type %s

What it means

goconst's toType maps user-facing string values (from config) to goconst API option types; an unrecognized string falls to the default branch and yields 'unknown type %s'. The config value for which option it applies to (e.g. match-constant vs number-minimum occurrences category or occurrence type) is not one of the accepted literals.

Solutions

Check the goconst settings documentation and use exact accepted values (e.g. 'compositelit', not 'compositeliteral')
Fix casing/typos — values are compared as raw strings
Remove the invalid option to fall back to defaults
Upgrade/downgrade golangci-lint if the valid value set changed between versions

Example fix

# before
linters-settings:
  goconst:
    ignore-type: compositeliteral
# after
linters-settings:
  goconst:
    ignore-type: compositelit

Defensive patterns

Strategy: validation

Validate before calling

validGoconstValues := map[string]bool{"string": true, "number": true, "compositelit": true}
for _, v := range goconstTypeValues {
    if !validGoconstValues[strings.ToLower(v)] {
        return fmt.Errorf("invalid goconst type value %q; allowed: string|number|compositelit", v)
    }
}

Try / catch

if err := golangci.Run(); err != nil {
    if strings.Contains(err.Error(), "unknown type") {
        fmt.Fprintln(os.Stderr, "fix goconst setting value: must be one of the documented literals (e.g. compositelit)")
        os.Exit(1)
    }
    return err
}

Prevention

Copy goconst option values from the official docs, not from memory
Keep values lowercase and exact (compositelit, not compositeliteral)
Lint the YAML config in CI with a schema check (e.g. golangci-lint config verify)

When it happens

Trigger: runGoconst read a goconst setting (e.g. the type/occurrence-related option such as 'find-duplicates' or the string-vs-compositelit selector) whose value isn't 'string' equivalent, 'number', or 'compositelit', so the switch in toType hits default.

Common situations: Typo in .golangci.yml (e.g. 'compositeliteral', 'CompositLit', 'str'), copying an option name from a newer/older goconst version with renamed values, or YAML quoting introducing unexpected characters.

Related errors

AI-assisted analysis of golangci/golangci-lint@ed7a235d2d (2026-09-02). Data as JSON: /api/errors/5671f0f0afc845a1. Report an issue: GitHub.

Appendix: source

Thrown at pkg/golinters/goconst/goconst.go:150

		return goconstAPI.Assignment, nil

	case "binary":
		return goconstAPI.Binary, nil

	case "case":
		return goconstAPI.Case, nil

	case "return":
		return goconstAPI.Return, nil

	case "call":
		return goconstAPI.Call, nil

	case "compositelit":
		return goconstAPI.CompositeLit, nil

	default:
		return 0, fmt.Errorf("unknown type %s", v)
	}
}

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