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Is it a known problem with theming in `beta02`? My app can switch from light to dark, but not back. And I can't understand what happened with it. It worked before beta02.

<https://kotlinlang.slack.com/archives/CJLTWPH7S/p1615651080120600>

hm, `Colors`  objects are mutable (their fields are `var`s), and looks like my `LightColorPalette` singleton gets changed somewhere, but I don't see where. If I copy it before passing to `MaterialTheme` it works as expected

Yes, this is a known issue (<https://issuetracker.google.com/issues/182635582>) - for now calling `.copy()` before you pass it in is a workaround

<@UMCJAPF63> what's the reason for mutability in `Colors` ? wouldn't it be better if it was a completely immutable class?

Yes typically immutability is good (and would help avoid issues like this) but in the case of colors there are very large performance benefits from having it mutable - it means that if you are animating one color (such as primary) then only components that are actually using that color will be recomposed, instead of every component in the application