Example of dartpad code

main.dart

import 'dart:io';
var x = 4;

class xyz {}

void arrexpr(num n) => (print(n));

void main() {

//   print(Platform.pathSeparator);
//   print(Platform.operatingSystemVersion);
  
  (arrexpr(10));
  
  dynamic xx = 12;
  xx = '123';
  print(xx);

  var x = 2;
  int y = 2;
  print(x + y);
  abc();
  // error because already inferred as int
  // x ='abc';

  String s1 = 'abc';
  var s2 = 'xyz';
  print(s1 + s2);
  print((s1 + s2).runtimeType);

  // Error: A value of type 'String' can't be assigned to a variable of type 'int'.
  // s2=1234;

  var l1 = [1, 2, 3, 4];
  List<int> l2 = <int>[1, 2, 3, 4];
  var l3 = <dynamic>[1, 2, 3, 'a', 'b', 'c'];

  l1.addAll(l2);
  print(l1);

  print(l1.runtimeType);
  print(l3.runtimeType);
  
  dynamic x4=11;
  x4='dddd';
  print(x4);
  
  print('THE END');
  
}

abc() {
  var x = 1;
  print(x);
}