code: public MethodHandle constant(Object value) {
          return invoke(MethodHandles.constant(type().returnType(), value));
      }
docs: Apply the tranforms, binding them to a constant value that will
  propagate back through the chain. The chain's expected return type
  at that point must be compatible with the given value's type.
  
  @param value the constant value to put at the end of the chain
  @return a handle that has all transforms applied in sequence up to the constant