setStartPosition(startLineNumber, startColumn) {
        if (this.getDirection() === 0 /* SelectionDirection.LTR */) {
            return new Selection(startLineNumber, startColumn, this.endLineNumber, this.endColumn);
        }
        return new Selection(this.endLineNumber, this.endColumn, startLineNumber, startColumn);
    }
Create a new selection with a different `selectionStartLineNumber` and `selectionStartColumn`.