Computed type key inference inconsistent with identical explicitly declared typeΒ #59987
Description
π Search Terms
keyof required keys key evaluation reduce getReducedType
π Version & Regression Information
- This is the behavior in every version I tried
β― Playground Link
π» Code
type distilled = distill<{
// ^?
foo: "default"
bar?: number
}>
// incorrectly inferred as unknown
type requiredDistilledKey = requiredKeyOf<distilled>
// ^?
// explicit declaration identical to hover of distilled
type declared = {
bar?: number
} & {
foo?: "default"
}
// now correctly inferred as never
type requiredDeclaredKey = requiredKeyOf<declared>
// ^?
type requiredKeyOf<o> = {
[k in keyof o]-?: o extends { [_ in k]-?: o[k] } ? k : never
}[keyof o]
type distill<t> = t extends object ? distillMappable<t> : t
type distillMappable<o> = {
[k in keyof o as k extends inferredDefaultKeyOf<o> ? never : k]: distill<o[k]>
} & {
[k in inferredDefaultKeyOf<o>]?: distill<o[k]>
}
type inferredDefaultKeyOf<o> = {
[k in keyof o]: o[k] extends "default" ? k : never
}[keyof o]
π Actual behavior
requiredDistilledKey inferred as unknown
π Expected behavior
requiredDistilledKey inferred as never, consistent with the equivalent declared version
Additional information about the issue
No response