Cannot define custom args due to missing ArgDefinition export

[mat-if]

Describe the bug

A custom re-usable Arg created in @oclif/core 3.27.0 is throwing an error when trying to upgrade to @oclif/core 4.0.9:

error TS2742: The inferred type of 'UrlArg' cannot be named without a reference to '../../node_modules/@oclif/core/lib/interfaces/parser'. This is likely not portable. A type annotation is necessary.

The Arg in question reports a type of ArgDefinition<Url, Record<string, unknown>>

Upon investigation, it appears that exporting ArgDefinition in https://github.com/oclif/core/blob/main/src/interfaces/index.ts fixes the issue, although it's not clear to me if there is a more correct way to do this.

It's also unclear as to why this started happening in 4.x since it doesn't appear there were any major changes to either interfaces/index.ts or interfaces/parser.ts

To Reproduce
Steps to reproduce the behavior:

Create a custom arg:

import { Args } from '@oclif/core'

type Url = {
  protocol: string | null
  hostname: string
  port: number | null
}

// Simplified for demonstration purposes
export function parseUrl(_input: string): Promise<Url> {
  return Promise.resolve({
    protocol: null,
    hostname: 'google.com',
    port: null,
  })
}

export const UrlArg = Args.custom<Url>({
  parse: async (input: string) => parseUrl(input),
})

Expected behavior

Typescript code compiles and arg is usable

Screenshots

Environment (please complete the following information):

• OS & version: MacOS Monterey 12.6.3
• Shell/terminal & version:
  • Shell: fish, version 3.7.0
  • Terminal: Ghostty , version 31d53849

Additional context
Add any other context about the problem here.