code: public static boolean isExpressionStatement(JCExpression tree) {
          switch(tree.getTag()) {
              case PREINC: case PREDEC:
              case POSTINC: case POSTDEC:
              case ASSIGN:
              case BITOR_ASG: case BITXOR_ASG: case BITAND_ASG:
              case SL_ASG: case SR_ASG: case USR_ASG:
              case PLUS_ASG: case MINUS_ASG:
              case MUL_ASG: case DIV_ASG: case MOD_ASG:
              case APPLY: case NEWCLASS:
              case ERRONEOUS:
                  return true;
              default:
                  return false;
          }
      }
docs: Return true if the tree corresponds to an expression statement