eval argument must be a known value

The eval function is being called with an argument that is an unknown value at Prepack time.

This means that Prepack does not have full knowledge of the heap state and control flow subsequent to the eval call, which means that it could generate a program that will behave differently at runtime from the program that is being prepacked.

To address this issue consider refining the environmental model so that Prepack can determine the value of the argument at Prepack time. If this is not possible, try rewriting the code so that eval is not necessary, using more restrictive mechanisms that Prepack can more easily deal with.