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.