flow_impl_derive is a derive macro that inserts code to allow a flow "implementation" to be called when compiled to wasm32

flow_impl_derive

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FlowImpl is a derive macro to be used on the structure that implements a function (by implementing the FlowImpl trait), so that when compiled for the wasm32 target, code is inserted to allocate memory (alloc) and to serialize and deserialize the data passed across the native/wasm boundary.