function get_loose_identifier(parser, opening_token) {
	// Find the next } and treat it as the end of the expression
	const end = find_matching_bracket(parser.template, parser.index, opening_token ?? '{');
	if (end) {
		const start = parser.index;
		parser.index = end;
		// We don't know what the expression is and signal this by returning an empty identifier
		return {
			type: 'Identifier',
			start,
			end,
			name: ''
		};
	}
}
@param {Parser} parser
@param {string} [opening_token]
@returns {Expression | undefined}