SourceSpanMixin constructor Null safety

1. Flutter
2. source_span
3. SourceSpanMixin
4. SourceSpanMixin constructor

SourceSpanMixin class

1. Constructors
2. SourceSpanMixin
3. Properties
4. end
5. hashCode
6. length
7. runtimeType
8. sourceUrl
9. start
10. text
11. Methods
12. compareTo
13. highlight
14. message
15. noSuchMethod
16. toString
17. union
18. Operators
19. operator ==