__close(scopeManager) {
        const implicit = [];

        for (let i = 0, iz = this.__left.length; i < iz; ++i) {
            const ref = this.__left[i];

            if (ref.__maybeImplicitGlobal && !this.set.has(ref.identifier.name)) {
                implicit.push(ref.__maybeImplicitGlobal);
            }
        }

        // create an implicit global variable from assignment expression
        for (let i = 0, iz = implicit.length; i < iz; ++i) {
            const info = implicit[i];

            this.__defineImplicit(info.pattern,
                new Definition(
                    Variable.ImplicitGlobalVariable,
                    info.pattern,
                    info.node,
                    null,
                    null,
                    null
                ));

        }

        this.implicit.left = this.__left;

        return super.__close(scopeManager);
    }
List of {@link Reference}s that are left to be resolved (i.e. which
need to be linked to the variable they refer to).
@member {Reference[]} Scope#implicit#left