static from_source({ source, file_basename, get_location }) {
		/**
		 * @type {{ line: number; column: number; }}
		 */
		let offset = get_location(0);
		if (!offset) offset = { line: 0, column: 0 };

		/**
		 * @type {DecodedSourceMap}
		 */
		const map = { version: 3, names: [], sources: [file_basename], mappings: [] };
		if (source == '') return new MappedCode(source, map);
		// we create a high resolution identity map here,
		// we know that it will eventually be merged with svelte's map,
		// at which stage the resolution will decrease.
		const line_list = source.split('\n');
		for (let line = 0; line < line_list.length; line++) {
			map.mappings.push([]);
			const token_list = line_list[line].split(regex_line_token);
			for (let token = 0, column = 0; token < token_list.length; token++) {
				if (token_list[token] == '') continue;
				map.mappings[line].push([column, 0, offset.line + line, column]);
				column += token_list[token].length;
			}
		}
		// shift columns in first line
		const segment_list = map.mappings[0];
		for (let segment = 0; segment < segment_list.length; segment++) {
			// @ts-ignore
			segment_list[segment][3] += offset.column;
		}
		return new MappedCode(source, map);
	}
@static
@param {Source} opts
@returns {MappedCode}