ToCode extension Null safety

1. macro_builder
2. definition
3. ToCode extension

definition library

1. Classes
2. ClassDeclaration
3. ClassDeclarationBuilder
4. ClassDeclarationMacro
5. ClassDefinition
6. ClassType
7. ClassTypeMacro
8. Code
9. ConstructorDeclaration
10. ConstructorDeclarationMacro
11. ConstructorDefinition
12. ConstructorDefinitionBuilder
13. ConstructorDefinitionMacro
14. ConstructorType
15. ConstructorTypeMacro
16. Declaration
17. DeclarationBuilder
18. DeclarationMacro
19. DeclarationType
20. DefinitionBuilder
21. DefinitionMacro
22. Element
23. Expression
24. FieldDeclaration
25. FieldDeclarationMacro
26. FieldDefinition
27. FieldDefinitionBuilder
28. FieldDefinitionMacro
29. FieldType
30. FieldTypeMacro
31. Fragment
32. FunctionBody
33. FunctionDeclaration
34. FunctionDeclarationMacro
35. FunctionDefinition
36. FunctionDefinitionBuilder
37. FunctionDefinitionMacro
38. FunctionType
39. FunctionTypeMacro
40. Macro
41. MethodDeclaration
42. MethodDeclarationMacro
43. MethodDefinition
44. MethodDefinitionMacro
45. MethodType
46. MethodTypeMacro
47. NamedArgument
48. Parameter
49. ParameterDeclaration
50. ParameterDefinition
51. ParameterType
52. Scope
53. Statement
54. TypeAnnotation
55. TypeBuilder
56. TypeDeclaration
57. TypeDefinition
58. TypeMacro
59. TypeParameterDeclaration
60. TypeParameterDefinition
61. TypeParameterType
62. TypeReference
63. Extensions
64. ToCode