Function storeAnnotation

packages/mobx/src/api/decorators.ts:29–51

(prototype: any, key: PropertyKey, annotation: Annotation)

 * so it can be inspected later by `makeObservable` called from constructor
 */
export function storeAnnotation(prototype: any, key: PropertyKey, annotation: Annotation) {
    if (!hasProp(prototype, storedAnnotationsSymbol)) {
        addHiddenProp(prototype, storedAnnotationsSymbol, {
            // Inherit annotations
            ...prototype[storedAnnotationsSymbol]
        })
    }
    // @override must override something
    if (__DEV__ && isOverride(annotation) && !hasProp(prototype[storedAnnotationsSymbol], key)) {
        const fieldName = `${prototype.constructor.name}.prototype.${key.toString()}`
        die(
            `'${fieldName}' is decorated with 'override', ` +
                `but no such decorated member was found on prototype.`
        )
    }
    // Cannot re-decorate
    assertNotDecorated(prototype, annotation, key)

    // Ignore override
    if (!isOverride(annotation)) {
        prototype[storedAnnotationsSymbol][key] = annotation
    }
}

function assertNotDecorated(prototype: object, annotation: Annotation, key: PropertyKey) {
    if (__DEV__ && !isOverride(annotation) && hasProp(prototype[storedAnnotationsSymbol], key)) {