FunctionType constructor Null safety

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

FunctionType class

1. Constructors
2. FunctionType
3. Properties
4. hashCode
5. isAbstract
6. isExternal
7. isGetter
8. isSetter
9. name
10. namedParameters
11. positionalParameters
12. returnType
13. runtimeType
14. typeParameters
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator ==