Shift on sum types

[Coachonko]

Doing some testing, trying to work with x.json2

import x.json2 as json

fn new_flash(mut data map[string]json.Any, value json.Any) {
    flashes_key := 'flashes'
    if existing_data := data[flashes_key] {
        existing_data << value // add one json.Any to existing []json.Any
        data[flashes_key] = existing_data
    } else {
        mut new_array := []json.Any{}
        new_array << value
        data[flashes_key] = new_array
    }
}

fn get_flashes(mut data map[string]json.Any) ?json.Any {
    flashes_key := 'flashes'
    if existing_data := data[flashes_key] {
        data.delete(flashes_key)
        return existing_data
    }
    return none
}

fn main() {
    mut flashes := map[string]json.Any{}
    
    mut flash_zero := []json.Any{}
    flash_zero << 'test_zero'
    flash_zero << 0000
    flash_zero << json.null
    new_flash(mut flashes, flash_zero)

    mut flash_one := []json.Any{}
    flash_one << 'test_one'
    flash_one << 111111
    flash_one << json.null

    new_flash(mut flashes, flash_one)
    get_flashes(mut flashes)
}

existing_data << value gives error: invalid operation: shift on type x.json2.Any
Is this a bug or is there another way to handle this?

[Coachonko]

Solved by using type refinement

fn new_flash(mut values map[string]json.Any, value json.Any) {
	flashes_key := 'flashes'
	if existing_data := values[flashes_key] {
		if existing_data is []json.Any {
			values[flashes_key] = arrays.concat(existing_data, value)
		} else {
			mut data := []json.Any{}
			data << existing_data
			values[flashes_key] = arrays.concat(data, value)
		}
	} else {
		values[flashes_key] = value
	}
}