TypeScript is broken at type-checking array/Record access

[alamothe]

const array = [1, 2, 3, 4]

a[i] // this should be of type number

type Key = "a" | "b" | "c"
const record: Record<Key, number> = { "a": 0, "b": 1, "c": 2 }

record[i] // this should be of type number

const record: Record<string, number> = { "a": 0, "b": 1, "c": 2 }

record[i] // this should be of type number | undefined

Why isn't there a way to configure TypeScript to have these most sane type assumptions? Either they're all a number, which is very unsafe for the third case, or with noUncheckedIndexedAccess they're all number | undefined which makes zero sense for the first two, as basically means to use ! for every array access.

EDIT: Note also that if Map is used in place of Record for the third case, it will correctly be number | undefined which also makes zero sense given that Record and Map are used interchangeably and should have consistent interfaces.

[MartinJohns]

You forgot to fill out the issue template. The behavior is working as intended and not broken. Also, Record and Map are not interchangeably.

[RyanCavanaugh]

The statement here that numeric access should be assumed in-bounds and string access should be assumed possibly-out-of-bounds is actually the reverse from what I hear most often.

[typescript-bot]

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