Can I do type introspection with trait objects and then downcast it?

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As you have noticed, downcasting only works with Any trait, and yes, it only supports 'static data. You can find a recent discussion on why it is so here. Basically, implementing reflection for references of arbitrary lifetimes is difficult.

It is also impossible (as of now, at least) to combine Any with your custom trait easily. However, a macro library for automatic implementation of Any for your trait has recently been created. You can also find some discussion on it here.

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