Ladislav Thon provided this answer (on the Dart forum),
I believe it's very safe to say that Dart will never have eval. But it will have other, more structured ways of dynamically generating code (code name mirror builders). There is nothing like that right now, though.
There are two ways of spawning an isolate: spawnFunction, which runs an existing function from the existing code in a new isolate, so nothing you are looking for, and spawnUri, which downloads code from given URI and runs it in new isolate. That is essentially dynamic code loading -- but the dynamically loaded code is isolated from the existing code. It runs in a new isolate, so the only means of communicating with it is via message passing (through ports).
Thank you Ladislav...
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