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kotlinlang

`joinToString` not being inline has been a (rather mild) inconvenience for me. Is there a reason why it isn't? I know that the stdlib is using a default value of `null` for the transform lambda, but couldn't it just use `it.toString()`?

I'm surprised that the implementation missed an opportunity to avoid having to call `toString()` for non-String elements. A `StringBuilder` can have numbers appended directly to it without building a String first, but `joinToString` nevertheless creates intermediate Strings.

I think `joinToString` is called rarely enough that having a `toString` call within the lambda isn't much boilerplate while confirming that you're using the right object and intend to turn it into a string. Compare that to `StringBuilder`, where you may regularly add multiple primitive values in a row and the code becomes mostly `toString` calls.