given that `plus` has a single element overload, w...

# announcements

[Nir]

given that plus has a single element overload, what's the reason for plusElement existing?

[nanodeath]

might be the difference of Collection and MutableCollection receiver? I'd have to see the signatures

[nanodeath]

I think you can say mutableList += element and list += element and they mean different things

[ilya.gorbunov]

https://youtrack.jetbrains.com/issue/KT-9992#focus=Comments-27-1283874.0-0

[Nir]

@nanodeath plusElement has no relationship at all to +=

[Nir]

that's plusAssign

[Nir]

yes, += looks for plusAssign, if it doesn't find it, and the LHF is var and not val, it will try to expand to list = list + element -> list = list.plus(element)

[Nir]

plusElement isn't involved

[nanodeath]

okay well pretend I said +, still holds

[Nir]

nope, it doesn't

[nanodeath]

oh re: that YouTrack, it's lists-of-lists are a mess 😄

[Nir]

yeah

[Nir]

it's the List of Lists. I haven't read it in detail but I'm guessing that it ends up giving you a List<Any> or something like that 😞

[Nir]

hmm maybe not. At any rate, the answer is definitely there

[Nir]

@ilya.gorbunov thanks!

[Tobias Berger]

I looked into it again and yes, it's it's the list of lists.
Collection<T>.plus has an overload that allows to add multiple values from another collection. This is resolved when trying to add a list to a list of lists, resulting in an implicit cast to List<Any>. plusElement can be used to avoid that behaviour and add the list as an element.

[Nir]

Yeah, I read the issue. It's kind of nasty that the deduction works that way