[Typing-sig] Re: Support for sealed classes

May 28, 2021

      On Fri, May 21, 2021 at 9:38 PM Arun Sharma <arun@sharma-home.net> wrote:
...
+1 for static type checking and avoiding inheritance in the syntax.
My interest comes from working on transpiling python, including sealed
classes to other statically typed languages.
I've used syntax such as this in one of my earlier projects with good
success:
```
@sealed
class Node:
    EXPRESSION = Expression
    STATEMENT = Statement
@sealed
class Expression:
    NAME = Name
    OPERATION = Operation
@sealed
class Statement:
    ASSIGNMENT = Assignment
```
A variant of this syntax and a proof of concept implementation built on top
of adt [1] library:

https://bit.ly/3upzGSc

The upstream ADT library has some mypy plugins. Would be great if other
type checkers supported something like this out of the box.

 -Arun

[1] https://github.com/jspahrsummers/adt