src/vs/editor/common/services/editorSimpleWorker.ts/MirrorModel/getWordUntilPosition
class MirrorModel:	public getWordUntilPosition(position: IPosition, wordDefinition: RegExp): IWordAtPosition {
		const wordAtPosition = this.getWordAtPosition(position, wordDefinition);
		if (!wordAtPosition) {
			return {
				word: '',
				startColumn: position.column,
				endColumn: position.column
			};
		}
		return {
			word: this._lines[position.lineNumber - 1].substring(wordAtPosition.startColumn - 1, position.column - 1),
			startColumn: wordAtPosition.startColumn,
			endColumn: position.column
		};
	}