Unexpected BOOLEAN value type

Error message

Unexpected BOOLEAN value type: ${typeof value} for ${variable.name}

What it means

A Figma variable declared as BOOLEAN resolved to a value that is not a boolean nor a resolvable boolean reference. The exporter warns and substitutes the default value for a bool type instead of failing.

Solutions

Fix the alias in Figma so the BOOLEAN variable references a boolean variable or holds a literal true/false
Refresh/re-resolve the variables snapshot before exporting
Trace earlier 'Failed to resolve BOOLEAN reference' warnings to the unresolved alias
Confirm resolvedType === "BOOLEAN" matches the actual Figma variable type

Example fix

// before
formattedValue = getDefaultValueForType("bool");
// after
if (typeof value !== "boolean") {
  throw new Error(`BOOLEAN variable ${variable.name} has non-boolean value: ${JSON.stringify(value)}`);
}
formattedValue = value;

Defensive patterns

Strategy: type-guard

Validate before calling

if (variable.resolvedType === "BOOLEAN" && value !== null && typeof value !== "boolean" && typeof (value as any)?.id !== "string") {
  throw new Error(`BOOLEAN variable ${variable.name} has invalid value`);
}

Type guard

function isBoolValue(v: unknown): boolean {
  return typeof v === "boolean" || (typeof v === "object" && v !== null && typeof (v as any).id === "string");
}

Try / catch

try {
  formattedValue = formatBool(value);
} catch (e) {
  exportInfo.errors.add(`BOOLEAN format failed for ${variable.name}: ${e.message}`);
  formattedValue = getDefaultValueForType("bool");
}

Prevention

Resolve aliases before formatting boolean values
Check that aliased targets are of the same type in Figma
Run a pre-export type validation pass over all variables

When it happens

Trigger: exportFigmaVariablesToSeparateFiles handles a BOOLEAN variable whose value is typeof neither 'boolean' nor an expandable reference object (e.g. alias to a non-boolean variable, null, undefined).

Common situations: Boolean variable aliased to a string/float variable whose resolution failed; stale snapshot after a type change in Figma; API response shape drift.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of slint-ui/slint@bb937076de (2026-09-16). Data as JSON: /api/errors/808e76e559a2e710. Report an issue: GitHub.

Appendix: source

Thrown at tools/figma-inspector/backend/utils/export-variables.ts:1207

                                if (resolvedValue) {
                                    formattedValue = resolvedValue;
                                    const referenceName =
                                        variableNamesById.get(value.id) ||
                                        value.id;
                                    comment = `Resolved from reference ${referenceName}`;
                                } else {
                                    formattedValue =
                                        getDefaultValueForType("bool");
                                    const referenceName =
                                        variableNamesById.get(value.id) ||
                                        value.id;
                                    comment = `Failed to resolve reference ${referenceName}, using default`;
                                    exportInfo.warnings.add(
                                        `Failed to resolve BOOLEAN reference ${value.id} for ${variable.name}.${modeName}`,
                                    );
                                }
                            } else {
                                console.warn(
                                    `Unexpected BOOLEAN value type: ${typeof value} for ${variable.name}`,
                                );
                                formattedValue = getDefaultValueForType("bool");
                            }
                        }

                        collectionStructure
                            .get(collectionName)!
                            .variables.get(sanitizedRowName)!
                            .set(modeName, {
                                value: formattedValue,
                                type: variable.resolvedType,
                                // No refId - all references are resolved to concrete values
                                comment: comment,
                            });
                    }

                    // Store the path for each variable ID

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