Fix after review

lib/domain/mistake.dart

@@ -17,6 +17,9 @@ class Mistake {
  /// Sorted by probability.
  final List<String> replacements;
 
+ /// A range of this mistake from offset to the end.
+ int get range => offset + length;
+
  /// Creates a new instance of the [Mistake] class.
  const Mistake({
  required this.message,

lib/presentation/widgets/language_tool_text_editing_controller.dart

@@ -28,40 +28,45 @@ class LanguageToolTextEditingController extends TextEditingController {
  }
 
  final lastMistakeIndex = mistakes.length - 1;
-
  for (int i = 0; i < mistakes.length; i++) {
  final mistake = mistakes[i];
- int previousMistakePosition = 0;
+ int previousMistakeEnd = 0;
  if (i > 0) {
  final previousMistake = mistakes[i - 1];
- previousMistakePosition =
- previousMistake.offset + previousMistake.length;
+ previousMistakeEnd = previousMistake.offset + previousMistake.length;
  }
  final mistakeStart = mistake.offset;
- final mistakeEnd = mistakeStart + mistake.length;
 
- if (mistakeEnd > text.length) {
+ if (mistake.range > text.length) {
  children.add(
  TextSpan(
- text: text.substring(previousMistakePosition),
+ text: text.substring(previousMistakeEnd),
  ),
  );
  break;
  }
 
  children.add(
- TextSpan(text: text.substring(previousMistakePosition, mistakeStart)),
+ TextSpan(text: text.substring(previousMistakeEnd, mistakeStart)),
  );
 
  final textStyle = style ?? const TextStyle();
- final mistakeText = text.substring(mistakeStart, mistakeEnd);
+ final mistakeText = text.substring(mistakeStart, mistake.range);
 
- // WidgetSpans with mistake text characters are used here to calculate the correct caret position, which can be incorrectly positioned because of the WidgetSpan issue, described here: https://github.com/flutter/flutter/issues/107432.
- // TextSpan recognizer to process clicks can't be used, because it requires the RichText widget instead of TextField, which we are using. Issue described here: https://github.com/flutter/flutter/issues/34931
+ // WidgetSpans with mistake text characters are used here to
+ // calculate the correct caret position, which can be
+ // incorrectly positioned because of the WidgetSpan issue,
+ // described here: https://github.com/flutter/flutter/issues/107432.
+ //
+ // TextSpan recognizer to process clicks can't be used,
+ // because it requires the RichText widget but the TextField
+ // widget does not contain one.
+ // Issue described here: https://github.com/flutter/flutter/issues/34931
 
  children.add(
  TextSpan(
  style: textStyle.copyWith(
+ color: Colors.green,
  decoration: TextDecoration.underline,
  decorationColor: Colors.red,
  decorationThickness: underlineThickness,
@@ -78,10 +83,11 @@ class LanguageToolTextEditingController extends TextEditingController {
  ],
  ),
  );
+
  if (i == lastMistakeIndex) {
  children.add(
  TextSpan(
- text: text.substring(mistakeEnd),
+ text: text.substring(mistake.range),
  ),
  );
  }