function function_builder(id, params, body) {
	return {
		type: 'FunctionExpression',
		id,
		params,
		body,
		generator: false,
		async: false,
		metadata: /** @type {any} */ (null) // should not be used by codegen
	};
}
@param {ESTree.Identifier | null} id
@param {ESTree.Pattern[]} params
@param {ESTree.BlockStatement} body
@returns {ESTree.FunctionExpression}