Intl.formatByParts() doesn't support the "unit" part type

[JonathanDCohen]

Search Terms:
Intl
NumberFormatPartsType
Code

const formatter = new Intl.NumberFormat('en', {style: 'unit', unit: 'kilobyte'});
return formatter.formatToParts(0).find(part => part.type === 'unit').value;

Expected behavior:
Compiles cleanly. See, for example, this MDN doc for Intl.formatByParts() which lists "unit" as a possible part type

Actual behavior:
tsc throws an error: This condition will always return 'false' since the types 'NumberFormatPartTypes' and '"unit"' have no overlap.
Playground Link:
https://www.typescriptlang.org/play?target=99&ts=4.2.0-dev.20201211#code/KYDwDg9gTgLgBAMwK4DsDGMCWEVwLYCGA1sAKoqYwBi0hMMwUAFKpQFxwDOMUmKA5gBo4AGwICkBfsA7deAgJRwA3gCg4cKMBhIouFMADucAJIoYIgHQA5JHgBGjGlDpMxEqcGHLuATxEycADkrDBBwqEAvgoA3KqRqqqgkLCIqBjYuAi0BPTAACbklCwUMLI8fEKi4vyS0uXy-EpqGmg43Ig5eVBwALz4xGSlznQMzKHC7rWeseqa2rpZXWOW2S65ACoQAAoEsJxMAAwKq3z5TExge-C9AHxwV7CWML5gwH29-SGlQQonAG4EERIYBxSJAA

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