Broken inferred recursive types

[blackakula]

Bug Report

TypeScript inference on recursive types is broken since v4.1

🔎 Search Terms

• inferred
• recursive

🕗 Version & Regression Information

• This changed between versions 4.0.5 and 4.1.5

⏯ Playground Link

Playground link with 4.3.0-beta - with the TS errors

Playground link with 4.0.5 - no errors

💻 Code

const Builder = <T extends {}>(model: T) => ({
    withComment: (comment: string) => Builder({ ...model, comment }),
    withSpecialComment: () => Builder(model).withComment('Special comment'),
    withTrackingNumber: (tracking: number) => Builder({ ...model, tracking }),
    build: () => model })

const a = Builder({});
// a.withComment('test').build().tracking // OK - expected "Property 'tracking' does not exist on type '{ comment: string; }'""
console.log(a.withTrackingNumber(1234).withSpecialComment().build().tracking)

🙁 Actual behavior

TS compiler error: "The inferred type of this node exceeds the maximum length the compiler will serialize. An explicit type annotation is needed.(7056)"

🙂 Expected behavior

No errors on compilation

[weswigham]

So, the declaration emit error is very intentional, because the declaration emit that is possible for us is imprecise:

see those anys? Yeah, those are places we just had to straight up truncate the type (if you click .d.ts on the sidebar in the 4.0.5 playground and way super patiently, you might eventually get what I have pictured above. or it might loop forever.). We don't really have a way to emit better declarations here without specifically generic inline type aliases, a la #30979

[ahejlsberg]

Below is a version with an explicit type annotation. This works as expected and generates a nice and compact declaration file.

type Builder<T> = {
    withComment: (comment: string) => Builder<T & { comment: string }>,
    withSpecialComment: () => Builder<T & { comment: string }>,
    withTrackingNumber: (tracking: number) => Builder<T & { tracking: number }>,
    build: () => T
};

const Builder: <T extends {}>(model: T) => Builder<T> = <T extends {}>(model: T) => ({
    withComment: (comment: string) => Builder({ ...model, comment }),
    withSpecialComment: () => Builder(model).withComment('Special comment'),
    withTrackingNumber: (tracking: number) => Builder({ ...model, tracking }),
    build: () => model });

const a = Builder({});

[SephReed]

Currently running into this issue.

I find that everything is fine until this error comes up, then suddenly the entire language server starts taking 3-6 seconds to respond to anything.

Unfortunately, It's very, very much impossible for me to give "An explicit type annotation is needed."

Also, everything was working fine this morning, and I can't seem to figure out what has changed since then. So I know TS can do it.

I even have a demo within my installed project that works great, but converting it to an npm package appears to have made the recursion too much somehow.

[SephReed]

I made some progress on this issue by converting all my interfaces to abstract classes. Not sure why it worked, but you can read more here:

https://stackoverflow.com/a/68475392/4808079

[blackakula]

Closing this issue without a fix - means breaking backward compatibility in a minor version.
Just checked in 4.4.0-beta - still this error

[mxxnseat]

i have same issue with mongoose when i try update my document with error text:
Type instantiation is excessively deep and possibly infinite.

Product.findOneAndUpdate(
            { id: product.id },
            {
                ...product,
                productCategoryId: categoryId,
                parentGroup: groupId,
            },
            { new: true, upsert: true }
        )

[SephReed]

I haven't shared it in this thread, but one fix I found is to use abstract classes instead of interfaces in certain areas.

I have no idea why this works, but an abstract class that references itself is much happier than an interface that does. Worked for me at least...

[zomars]

This issue just started popping up without any changes made to our project.

[Qix-]

This is happening with AJV schemas (trivial ones at that), but only in my editor. The actual tsc invocation works fine.