Type and interface have different behavior in index signature extends checking.

[ruojianll]

🔎 Search Terms

"extends", "type and interface"

🕗 Version & Regression Information

version all

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.4.2#code/C4TwDgpgBAKu0F4oG8BQUNQIYC4oDsBXAWwCMIAnVAX1VQEt9hKAzLAY2gEknWPo0mbHiJlKNOqEhQAglCRxpEAB7N8AEwDOUAEoR2AewrqAPJuAVGAcwA0BEuQoA+KAH4oFwtDxsANpugAekDPCFQpaAAheSgeZgo2TigVNS1dfSNTc0t8W3sxZzcPCi8oHyx-IMC-ANQgA

💻 Code

type Type = {
    a: number
}

interface Interface {
    a: number
}

type A = Type extends Record<string, number> ? true : false //true
type B = Interface extends Record<string, number> ? true : false //false

🙁 Actual behavior

type A is true
type B is false

🙂 Expected behavior

both true or false

Additional information about the issue

No response

[ruojianll]

I can't find any document about the difference about this.

[MartinJohns]

Duplicate of #42825. See also #15300 (comment).

Used search terms: interface type record in:title