resolve(ident) {
        var ref, i, iz;
        assert(this.__isClosed(), 'Scope should be closed.');
        assert(ident.type === Syntax.Identifier, 'Target should be identifier.');
        for (i = 0, iz = this.references.length; i < iz; ++i) {
            ref = this.references[i];
            if (ref.identifier === ident) {
                return ref;
            }
        }
        return null;
    }
returns resolved {Reference}
@method Scope#resolve
@param {Esprima.Identifier} ident - identifier to be resolved.
@return {Reference}