// The intermediateTuple coercer gets from S --> I1 (an intermediate type).
// The current tuple's coercer gets us from I2 --> X. where I2 is assignable
// from I1 (i.e., I2 is a superclass/superinterface of I1) and X is a new
// intermediate type, hopefully closer to our eventual target type.
Coercion compoundCoercer = new CompoundCoercion(intermediateTuple.getCoercion(), tuple.getCoercion());
CoercionTuple compoundTuple = new CoercionTuple(sourceType, newIntermediateType, compoundCoercer, false);
// So, every tuple that is added to the queue can take as input the sourceType.
// The target type may be another intermediate type, or may be something