public:

virtual ~FunctionProvider() = default;

// Returns a reference to a function implementation based on the provided

// Activation. Given the same activation, this should return the same Function

// instance. The cel::FunctionOverloadReference is assumed to be stable for

// the life of the Activation.

//

// An empty optional result is interpreted as no matching overload.

virtual absl::StatusOr<absl::optional<FunctionOverloadReference>> GetFunction(

const FunctionDescriptor& descriptor,

const ActivationInterface& activation) const = 0;