Typescript compilation is taking a long time to run, so I used generateTrace from https://github.com/microsoft/TypeScript/pull/40063
It showed that most of the time was comparing complicated classes with their subclasses. E.g. one of the classes is the base Objection model (https://github.com/vincit/objection.js), which is the base class that all my models inherit.
E.g. I have code like:
class User extends Model {}
function doSomething(model: typeof Model) {}
doSomething(User);
I have ~50 models. I think the first time TS encounters each model is slow, then it caches it. It takes about 5s for TS to compare a specific model with the base Model. Model uses types from several libraries. Here's a screenshot of the trace, it takes 5min just to compare each model with Model:
Is there a way to get TS to skip comparing Model with itself? I.e. since User extends Model, there's no need to check the fields it inherited.
Edit:
I reduced the time to check the 50 models from 5min to 30s. I have a map of models:
type ModelType = 'user' | ...
type ModelsMap = {
user: User,
...
};
getModel<T extends ModelType>(type: T): ModelsMap[T] {}
This is slow because ModelsMap[T] is a union of all the models. It became faster if I return the base model when T is an union of all the model types:
type TypeToModel<T extends ModelType> = ModelType extends T ? Model : ModelsMap[T];
getModel<T extends ModelType>(type: T): TypeToModel<T> {}
However, it would still be nice to know if there are hacks to make comparing subclass faster. E.g. if it's possible to disable structural typing and use nominal for subclasses.
