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kotlinlang

Why is `if (list?.isEmpty())` not allowed when `if (list?.isEmpty() == true)` is? You are still not specifying null behaviour...

Yes, you are. Only `true` is equal to `true`. `false`, `null` and any other value is not equal to `true`.

`list?.isEmpty()` will return null if `list` is null

`list?.isEmpty()` returns `Boolean?` and comparing it to `true` lets you check if it’s true. `false` and `null` are two other states the if statement can’t make assumptions about. “not specifying null behavior” is only important if you’re using the `if` as an assignment expression, otherwise you just need to give it a non-nullable `Boolean`

I see. Feels a bit weird, if statement and comparing to true not being the same. I guess next question is: Why does equals operator accept nullable arguments? Java compatibility?

Why would it not? How would you do `if (a == null)` otherwise?

That would be an equals method on nullable types. Like `fun Int?.equals(other: Int?): Boolean`

I am not sure I see why that is any better than `==`.

Also, that would make it impossible to compare two things that you do not know the type of.

I guess better type safety? But yeah maybe it's not any better.

You can do `list != null &amp;&amp; list.isEmpty()` or `list?.isEmpty() ?: false` if that's better for you. 

You could also write an extension function like `Iterable?.isEmptyOrNull() = this == null || this.isEmpty()`  or make it more specific to the classes you need to use it for

There's very little that is inconvenient about Kotlin