Very simple question about generics and unions

[wise bone]

export class PluginController<
  Settings extends GenericSettings | undefined = undefined,
> { //blablabla
}```
What does `undefined = undefined` mean in this context? Wouldn't that just return `true`?

Or in this context:

export interface PluginInstance<
  Settings extends GenericSettings | undefined = GenericSettings | undefined,
> {
// bla bla bla
}

[woeful ridge]

that's a default for the generic

[half otter]

type X<T = "a"> = T;
type Y = X<number>;
//   ^? - type Y = number
type Z = X;
//   ^? - type Z = "a"

[woeful ridge]

kinda like how you do function argument defaults

[wise bone]

oooooooh

but wait

[wise bone]

it says undefined = GenericSettings, and undefined is a standard type / value

In your example T isnt like undefined

[woeful ridge]

Wouldn't that just return true?
remember, equality checks are == in most programming languages

[wise bone]

oh right

[woeful ridge]

that's a generic named Settings, constrained to GenericSettings | undefined, defaulted to GenericSettings | undefined

Settings
  extends GenericSettings | undefined
  = GenericSettings | undefined

[wise bone]

ooooh

i feel like some parenthesis would make that more clear

[wise bone]

so this is Settings, which extends GenericSettings | undefined, but is defaulted to undefined

[woeful ridge]

correct

[wise bone]

oki

thank you