Type instantiation is excessively deep and possibly infinite in version 4.1

[mateja176]

Motivation
I wrote a type to make [lodash get[(https://lodash.com/docs/4.17.15#get) and especially formik getFieldProps type safe by writing a generic type which is represent a union of string literal types representing a full . separated path to leaf nodes of a possibly nested record.

TypeScript Version: 4.1.0

Search Terms:

• Type instantiation is excessively deep and possibly infinite.ts(2589)
• Mapped types
• Generics
• Conditional types

Code

// @ts-ignore
type FieldKey<O extends Record<string, unknown>> = { [key in keyof O]: O[key] extends Record<string, unknown> ? `${string & key}.${string & FieldKey<O[key]>}` : key }[keyof O];
type Example = { dog: "Jacky", toys: { mouse: { color: "gray", teeth: "white" }, bone: { color: 'blue', pimples: true }, box: { cube: { ball: 'red' } } } };
type FieldKey2 = FieldKey<Example>;

Expected behavior:

No error is thrown.

Actual behavior:

Type instantiation is excessively deep and possibly infinite.ts(2589) error is thrown.

Playground Link:

This is a link to the playground.

Related Issues:

• “Type instantiation is excessively deep and possibly infinite” but only in a large codebase #34933
• "Type instantiation is excessively deep and possibly infinite" even for generated non-recursive type #31619
• New error: Type instantiation is excessively deep and possibly infinite. #37613

[paales]

Experiencing the same with a similar approach. I believe the error wasn't there with typescript 4.1.0-beta, but started to occur with 4.1.1-rc

• 4.1.0-beta: no error
• nightly: Type instantiation is excessively deep and possibly infinite.

[pedrodurek]

Hey guys, I'm facing a similar issue, but it seems to be more like a typescript limitation (despite the data size not being that large).
You can see on the examples below that when I'm handling 22 namespaces (ns), it doesn't throw any error, but from 23 namespaces (ns) it does. It infers the proper type though.

• 22 namespaces
• 23 namespaces

We're relying on those types here, so I cannot simply use @ts-ignore to suppress the error.
It'd also be great to have a flag to suppress this error and/or control the depth under tsconfig.

[bsssshhhhhhh]

Currently running into this error on 4.1.2 trying to improve the types in my library. Increasing the constraintDepth limit in getImmediateBaseConstraint() makes the error disappear.

+1 for turning this into a tsconfig setting instead of hardcoding it like this - it seems to be an arbitrary limit rather than a technical one.

[ClickerMonkey]

My code base is also plagued by this error, sometimes it goes away for a few seconds, sometimes the exact line the error is being thrown changes, even when the code is not modified. It's interestingly inconsistent!

[ahejlsberg]

This issue no longer reproduces. Closing.

[zilijonas]

Still getting this error with the 4.3.5 version.

[pedrodurek]

Same ☝️

[Walraz]

Same error still in 4.3.5

[paales]

Might be worthwhile to create a testcase in the playground https://www.typescriptlang.org/play?ts=4.4.0-beta and create a new issue

[pedrodurek]

For my case, the issue was solved on 4.5.0-beta.

[GR34SE]

Can confirm that 4.5.0-beta resolves the issue. For me, it was throwing when complex mobx-state-tree models were passed to generic types such as Instance: Instance<typeof ComplexModel>