Complex generic does not narrow type

[qwelias]

Bug Report

🔎 Search Terms

generic narrow type guard object index

🕗 Version & Regression Information

v4.2.3

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about generics

⏯ Playground Link

Playground link with relevant code

💻 Code

type FO = 'f' | 'o'

type Foo<Type extends FO = FO> = { [T in Type]: {
    type: T,
    data: Record<T, true>,
} }[Type]

const foo = {} as Foo
if (foo.type === 'f') foo.data.f // all good, narrows the type

type Bar<Type extends FO = FO> = { [T in Type]: { foo: Foo<T> } & {
    f: { bar: Record<T, true> },
    o: unknown,
}[T] }[Type]

const bar = {} as Bar
if (bar.foo.type === 'f') bar.bar // broke

🙁 Actual behavior

Property 'bar' does not exist on type 'Bar'

🙂 Expected behavior

bar.bar identified as Record<T, true> because it's in the same indexed property as bar.foo.type for T that is equals to f

[RyanCavanaugh]

See #18758

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.