smfc: use specific types instead of generic lambdas on gen code
smfc: use specific types instead of generic lambdas on gen code

Fixes #356

Signed-off-by: Alexander Gallego <60c6d277a8bd81de7fdde19201bf9c58a3df08f4@vectorized.io>
Message-Id: <20190509145529.11626-1-60c6d277a8bd81de7fdde19201bf9c58a3df08f4@vectorized.io>

senior7515/smurf,senior7515/smurf,senior7515/smurf