KT element: KtCallExpression
FIR element: FirFunctionCallImpl
FIR source kind: KtRealSourceElementKind

FIR element rendered:
mutableListOf#<String>()

FIR FILE:
FILE: [ResolvedTo(IMPORTS)] insidePlusAssignTargetScript.kts
    context(<script>@kotlin.script.templates.standard.ScriptTemplateWithArgs)
    SCRIPT: [ResolvedTo(BODY_RESOLVE)] 
        [ResolvedTo(RAW_FIR)] lval args: R|kotlin/Array<kotlin/String>|

        public? final? [ResolvedTo(RAW_FIR)] fun foo([ResolvedTo(RAW_FIR)] x: MutableMap<Int, MutableList<String>>): R|kotlin/Unit| {
            +=(x#.getOrPut#(IntegerLiteral(1), <L> = [ResolvedTo(RAW_FIR)] getOrPut@fun <implicit>.<anonymous>(): <implicit> <inline=Unknown>  {
                mutableListOf#<String>()
            }
            ), String(str))
        }