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kotlinlang

Perhaps it's just as simple as "square braces are syntactic sugar for calling the 'set' method on the given object"?

ah, yeah, that's it. <https://spring.io/guides/tutorials/spring-boot-kotlin/> sorry, as usual i find my own answer immediately after asking the question.

The general term for this in Kotlin is “operator overloading”, and operator functions can be implemented either as member or extension functions <https://kotlinlang.org/docs/operator-overloading.html#indexed-access-operator>

Thank you very much for the reference, i appreciate it. That makes perfect sense.