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kotlinlang

todo and explicit cast were added after some kotlin update. when compiler started marking this piece of code as error - however if fact it is error

previously `+` operator was resolved as 
1. `public operator fun &lt;T&gt; Collection&lt;T&gt;.plus(element: T): List&lt;T&gt; //from _Collections.kt`
2a. `public operator fun &lt;T&gt; Collection&lt;T&gt;.plus(elements: Iterable&lt;T&gt;): List&lt;T&gt; //from _Collections.kt`
or as this
2b. `public operator fun &lt;T&gt; Collection&lt;T&gt;.plus(elements: Sequence&lt;T&gt;): List&lt;T&gt; //from _Collections.kt`
I'm not sure whether it was 2a. or 2b. and have no means to check it right now (maybe there was some other function as well)

however now (kotlin 1.0.0-beta-4584) `+` is resolved as
1. `public operator fun &lt;T&gt; Collection&lt;T&gt;.plus(element: T): List&lt;T&gt; //from _Collections.kt`
2. `operator fun &lt;T: Any&gt; T.plus(list: List&lt;T&gt;): List&lt;T&gt; //from utils.kt`
which makes my code behave not in a way it was intended

Why is function `2.` picked instead of `2a.` or `2b.` where the latter are more "specialized"?

P.S. yes, I shouldn't be so careless with compiler warnings in the first place, but nonetheless question on "specialization" of extension remains open.