'_fontFamily' method not found Receiver: Instance of 'TextStyleRef' Arguments: []

[nullrocket]

Upgrading to Flutter 2.8.0 causes the following error. You can reproduce it running the example app.

======== Exception caught by widgets library =======================================================
The following NoSuchMethodError was thrown building Text("This is some text!", inherit: true
, color: ColorRef(0xffffffff), size: 16.0, weight: 400, dirty, dependencies: [DefaultTextStyle]):
'_fontFamily'
method not found
Receiver: Instance of 'TextStyleRef'
Arguments: []

The relevant error-causing widget was: 
  Text Text:file:///home/doug/IdeaProjects/themed/example/lib/main.dart:80:34
When the exception was thrown, this was the stack: 
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 251:49     throw_
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/operations.dart 735:3  defaultNoSuchMethod
dart-sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart 60:17                noSuchMethod
packages/themed/src/themed.dart 838:3                                            get [_fontFamily]
packages/flutter/src/painting/text_style.dart 1026:24                            merge

After digging around a bit I tried changing the following and extending instead of implementing, that fixed it but I'm not sure of what further issues that may cause.

//class TextStyleRef implements TextStyle, ThemeRef {

class TextStyleRef extends TextStyle with ThemeRef {
...

[marcglasberg]

Fixed in version [3.0.0].