Conflicting overload on unrolling union type containing both string literal and string

[Schahen]

this code:

declare namespace api {
  type CalendarKey = 'sameDay' | 'nextDay' | 'lastDay' | 'nextWeek' | 'lastWeek' | 'sameElse' | string;

  interface Locale {
    calendar(key?: CalendarKey): string;
  }
}

export = api;

is converted to:

package api

external interface Locale {
    fun calendar(key: String /* 'sameDay' | 'nextDay' | 'lastDay' | 'nextWeek' | 'lastWeek' | 'sameElse' */ = definedExternally): String
    fun calendar(key: String = definedExternally): String
    fun calendar(): String
}

hence a conflicting overload.
I'm surprised to see CalendarKey definition at first place (for me it's equivalent to just declaring string) but still this shouldn't be the case - this should be merged.

[Schahen]

The same, of course, happens with numeric literals as well:

@file:JsModule("tmp")
@file:JsNonModule
@file:Suppress("INTERFACE_WITH_SUPERCLASS", "OVERRIDING_FINAL_MEMBER", "RETURN_TYPE_MISMATCH_ON_OVERRIDE", "CONFLICTING_OVERLOADS", "EXTERNAL_DELEGATION")
package api

import kotlin.js.*
import kotlin.js.Json
import org.khronos.webgl.*
import org.w3c.dom.*
import org.w3c.dom.events.*
import org.w3c.dom.parsing.*
import org.w3c.dom.svg.*
import org.w3c.dom.url.*
import org.w3c.fetch.*
import org.w3c.files.*
import org.w3c.notifications.*
import org.w3c.performance.*
import org.w3c.workers.*
import org.w3c.xhr.*

external interface Locale {
    fun calendar(key: Number /* 1 | 3 | 5 | 7 */ = definedExternally): String
    fun calendar(key: Number = definedExternally): String
    fun calendar(): String
}