Route Props Helpers with params using string literal types or custom types

[joshunger]

Now that Next.js 15.5 automatically generates globally available PageProps, LayoutProps, and RouteContext types with full parameter typing and no imports required what is the best way to generate params with a string literal type or custom type?

We would want to do something like -

type Params = Promise<{
  locale: Locale;
}>;

Given something like props: LayoutProps<"/[locale]">

EDIT: from what I can see ...

validator.ts has:

// Validate ../../app/[locale]/layout.tsx
{
  const handler = {} as typeof import("../../app/[locale]/layout.js")
  handler satisfies LayoutConfig<"/[locale]">
}

from validator.ts:

type LayoutConfig<Route extends LayoutRoutes = LayoutRoutes> = {
  default: React.ComponentType<LayoutProps<Route>> | ((props: LayoutProps<Route>) => React.ReactNode | Promise<React.ReactNode> | never | void | Promise<void>)
  generateStaticParams?: (props: { params: ParamMap[Route] }) => Promise<any[]> | any[]
  generateMetadata?: (
    props: { params: Promise<ParamMap[Route]> } & any,
    parent: ResolvingMetadata
  ) => Promise<any> | any
  generateViewport?: (
    props: { params: Promise<ParamMap[Route]> } & any,
    parent: ResolvingViewport
  ) => Promise<any> | any
  metadata?: any
  viewport?: any
}

from routes.d.ts:

  type LayoutProps<LayoutRoute extends LayoutRoutes> = {
    params: Promise<ParamMap[LayoutRoute]>
    children: React.ReactNode
  } & {
    [K in LayoutSlotMap[LayoutRoute]]: React.ReactNode
  }

from routes.d.ts:

interface ParamMap {
  "/[locale]": { "locale": string; }
  // ...
}

[icyJoseph]

Mmm I am a bit mixed with contexts right now, but I think this PR #82955 is what's missing?

[joshunger]

Oooo ty closer! However, I don't think that would fix LayoutConfig @bgub any ideas?