Dart エラー「Unhandled exception:RangeError (start): Invalid value: Not in inclusive range x..x: xx」が発生した場合の対処法

void main() {

  String str = 'abcdef';

  print(str.substring(2,7));

}

Unhandled exception:
RangeError (end): Invalid value: Not in inclusive range 2..6: 7
#0      RangeError.checkValidRange (dart:core/errors.dart:363:9)
#1      _StringBase.substring (dart:core-patch/string_patch.dart:400:27)
#2      main (file:///c:/sample/main.dart:5:13)
#3      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19)
#4      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)

void main() {

  String str = 'abcdef';

  print(str.substring(2,5));

}

void main() {

  String str = 'abcdef';

  print(str[10]);

}