reproduce the json cast bug. Failed invoking the getRequests function. Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String'

json_cast_test.json

import 'dart:convert';

void main() {
  for (int i = 0; i < 5; i++) {
    print('hello ${i + 1}');
  }

  String json =
      "[ { \"customerName\":\"Jack Kal\", \"fromAddress\":\"120 King Street, \", \"fromLocation\":{ \"latitude\":123, \"longitude\":456.88 }, \"item\":\"lipstick\", \"notes\":\"small, pick up by receipeint\", \"price\":5, \"requestTimeStamp\":\"201806301359\", \"requstId\":123456, \"status\":\"pending\", \"toAddress\":\"6666 Harlow Road, L5N4T2, Mississuaga, ON \", \"toLocation\":{ \"latitude\":125, \"longitude\":458.88 } }, { \"customerName\":\"Jet Lee\", \"fromAddress\":\"240 Queen Street, \", \"fromLocation\":{ \"latitude\":1239, \"longitude\":456.88 }, \"item\":\"milk powder\", \"notes\":\"drop off\", \"price\":6, \"requestTimeStamp\":\"201806301959\", \"requstId\":123457, \"status\":\"pending\", \"toAddress\":\"8888 Harlow Road, L5N4T2, Mississuaga, ON \", \"toLocation\":{ \"latitude\":125, \"longitude\":458.88 }, \"weight\":\"8 KG\" } ]";

  List<Map<String, dynamic>> data =
      jsonDecode(json).cast<Map<String, dynamic>>();
  print('convert done');
  _generateRequests(data);
}

int _generateRequests(List<Map<String, dynamic>> requestsData) {
  var listOfRequests = [];
  for (var postData in requestsData) {
    listOfRequests.add(new RequestPost.fromJSON(postData));
  }

  return 0;
}

class RequestPost {
  final String customerName;
  final String fromLocation;
  final String toLocation;
  final String fromAddress;
  final String toAddress;
  final String notes;
  final String requestId;
  final String userId;

  const RequestPost(
      {this.customerName,
      this.fromLocation,
      this.toLocation,
      this.fromAddress,
      this.toAddress,
      this.notes,
      this.requestId,
      this.userId});

  factory RequestPost.fromJSON(Map<String, dynamic> data) {
    return new RequestPost(
      customerName: data['customerName'],
      fromLocation: data['fromLocation'],
      toLocation: data['toLocation'],
      fromAddress: data['fromAddress'],
      toAddress: data['toAddress'],
      notes: data['notes'],
      userId: data['userId'],
      requestId: data['requestId'],
    );
  }
}