array types don't extend type with wider key type

[DetachHead]

Bug Report

🔎 Search Terms

array record extends

🕗 Version & Regression Information

4.6.0-dev.20220105

⏯ Playground Link

Playground link with relevant code

💻 Code

type A = Record<number | string, unknown>
type B = Record<number, unknown>
type C = unknown[]

type Foo = B extends A ? true : false //true

type Bar = C extends B ? true : false //true

type Baz = C extends A ? true : false //false

🙁 Actual behavior

C doesn't extend A, even though it extends B which extends A

🙂 Expected behavior

C extends A

[RyanCavanaugh]

Transitivity is not a property of assignability (this fact is easily demonstrated with optional properties, which is one way to reason about how index signatures should work).

[DetachHead]

this fact is easily demonstrated with optional properties

could you show an example of this please

[RyanCavanaugh]

{ a?: number } -> { } -> { a?: string }

[DetachHead]

i see what you mean now. however in that example it's obvious { a?: number } doesn't extend { a?: string } but i'm having trouble wrapping my head around why unknown[] doesn't extend Record<number | string, unknown>

[github-actions]

This issue has been marked as 'Not a Defect' and has seen no recent activity. It has been automatically closed for house-keeping purposes.