code: private void checkNonEmpty(Decl.Variable d, LifetimeRelation lifetimes) {
  		if (relaxedSubtypeOperator.isVoid(d.getType(), lifetimes)) {
  			syntaxError(d.getType(), EMPTY_TYPE);
  		}
  	}
docs: Check that a given variable declaration is not empty. That is, the declared
  type is not equivalent to void. This is an important sanity check.
  
  @param d