Flow only type-checks files that have opted into it with the //@flow comment. It will have some trouble dealing with the compiled output of another tool like Ty

Flow only type-checks files that have opted into it with the //@flow comment. It will have some trouble dealing with the compiled output of another tool like Typescript. For example, it probably wouldn't understand that output of how Typescript compiles classes into ES5 represents a class. Even if using both of them on the same code worked, Flow and Typescript are both a bit anal about certain dynamic javascript patterns, and I think any possible extra gains from having both check your code would be canceled out by having to write your code in ways to please both type-systems.