Bug Report

Given (this is just the smaller repro I could come up with, not real code):

const p = <T>(fn: () => T): T => {return null as any}

const Base = <T>(val: T): {new(): T} => {
  return null as any;
}

class C extends Base({
 x: p<C[]>(() => [])
}) { }

With TS 4.3.2 it gives the errors:

Type 'C' recursively references itself as a base type.ts(2310)
'C' is referenced directly or indirectly in its own base expression.ts(2506)

where as there’s no such error with TS 4.2.4

If the p function parameter is changed from fn: () => T to fn: () => any or x: p<C[]>(() => []) is changed to x: p<C[]>(() => [] as any) then it does not give that error anymore.

Real impact:

This impacts a library that used to be able to do self-referenced models:

class TreeNode extends Model({ children: prop<TreeNode[]>(() => []), x: prop(0) }) {}

but with the new version it is not possible anymore

Alternative repro:

abstract class Base2 {
    abstract root() : Derived
}

class Derived extends class extends Base2 {
  root() {
    return undefined as any
  }
}
{}

🕗 Version & Regression Information

• This changed between versions 4.2.4 and 4.3.2

⏯ Playground Link

Playground Link