Union type not enforcing members correctly

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TypeScript Version: 3.1.1

Search Terms: unions

Code

export enum ButtonStatus {
  ENABLED = 'enabled',
  DISABLED = 'disabled',
  LOADING = 'loading',
}

export interface RegularButtonProps {
  readonly status: ButtonStatus;
}

export interface LoadingButtonProps {
  readonly status: ButtonStatus.LOADING;
  readonly loadingText: string;
}

export type ButtonProps = RegularButtonProps | LoadingButtonProps;

const buttonProps: ButtonProps = {
  status: ButtonStatus.LOADING,
  loadingText: 42,
};

Expected behavior:

Error saying loadingText should be of type string.

Actual behavior:

No error. Hovering over loadingText does tell me that loadingText is a string, so the compiler knows but doesn't raise it?

Playground Link:

https://www.typescriptlang.org/play/#src=export%20enum%20ButtonStatus%20%7B%0A%20%20ENABLED%20%3D%20'enabled'%2C%0A%20%20DISABLED%20%3D%20'disabled'%2C%0A%20%20LOADING%20%3D%20'loading'%2C%0A%7D%0A%0Aexport%20interface%20RegularButtonProps%20%7B%0A%20%20readonly%20status%3A%20ButtonStatus%3B%0A%7D%0A%0Aexport%20interface%20LoadingButtonProps%20%7B%0A%20%20readonly%20status%3A%20ButtonStatus.LOADING%3B%0A%20%20readonly%20loadingText%3A%20string%3B%0A%7D%0A%0Aexport%20type%20ButtonProps%20%3D%20RegularButtonProps%20%7C%20LoadingButtonProps%3B%0A%0Aconst%20buttonProps%3A%20ButtonProps%20%3D%20%7B%0A%20%20status%3A%20ButtonStatus.LOADING%2C%0A%20%20loadingText%3A%2042%2C%0A%7D%3B%0A

Related Issues:

Mmmaybe this one? #26450

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Ah, sorry, didn't see @DanielRosenwasser's PR: #27087