code: private WyalFile.Stmt or(WyalFile.Stmt lhs, WyalFile.Stmt rhs) {
  		if (lhs == null) {
  			return rhs;
  		} else if (rhs == null) {
  			return rhs;
  		} else {
  			WyalFile.Stmt.Block lhsBlock = new WyalFile.Stmt.Block(lhs);
  			WyalFile.Stmt.Block rhsBlock = new WyalFile.Stmt.Block(rhs);
  			return new WyalFile.Stmt.CaseOf(lhsBlock, rhsBlock);
  		}
  	}
docs: Construct a disjunct of two expressions
  
  @param lhs
  @param rhs
  @return