FunctionDefinitionBuilder constructor Null safety

1. macro_builder
2. definition
3. FunctionDefinitionBuilder
4. FunctionDefinitionBuilder constructor

FunctionDefinitionBuilder class

1. Constructors
2. FunctionDefinitionBuilder
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. implement
8. noSuchMethod
9. toString
10. typeDefinitionOf
11. wrapBody
12. Operators
13. operator ==