Intersection type kills mapped types restriction

[luxalpa]

TypeScript Version: typescript@3.1.0-dev.20180915 (also happens in 2.7.2)
tested with unmodified tsconfig generated by tsc --init

Search Terms: intersection mapped types restrictions

Code

type locales = 'us' | 'jp' | 'nz'

type YZ = {
  [routeName: string]: {someRandomProperty?:string} & { // this does not throw the error!
  // [routeName: string]: {} & {        // this will throw the error!
  // [routeName: string]: {             // just like this!
  // [routeName: string]: undefined & { // or this!
    urls: {
      [P in locales]?: string;
    }
  }
}

let value: YZ = {
  'hello': {
    urls: {
      jp: 'dragon',
      ph: 'unknown'
    }
  }
};

Expected behavior:
There should be an error message along the lines of Type '{ jp: string; ph: string; }' is not assignable to type '{ us?: string | undefined; jp?: string | undefined; nz?: string | undefined; }'. Object literal may only specify known properties, and 'ph' does not exist in type '{ us?: string | undefined; jp?: string | undefined; nz?: string | undefined; }'

Actual behavior:
No error message is thrown :(

Playground Link:
Playground never shows the error message for some reason.

Related Issues:

#19927
#22255

[mattmccutchen]

Duplicate of #13813.

[typescript-bot]

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

[jcalz]

Looks like this has been fixed as of TS3.5.