fix: make isFalsyType() return true for 0n

[kirkwaiblinger]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: isFalsyType should return true for 0n #544
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

The type.value returns a PseudoBigInt object rather than an actual bigint for TS legacy support reasons. Therefore, to determine if a literal is a falsy value, we cannot rely on the truthiness of type.value alone, and need to check what the actual object is if it's not a primitive.

[JoshuaKGoldberg]

Unit tests are failing, could you fix those up please?

[RebeccaStevens]

Looks like the issue is caused by an update to pnpm, to a version not compatible with the version of node we're using for the testing. #531 should fix this.

[kirkwaiblinger]

Looks like the issue is caused by an update to pnpm, to a version not compatible with the version of node we're using for the testing. #531 should fix this.

I'm thinking it's best if I just wait with this PR until that gets merged then?

[JoshuaKGoldberg]

Oh, I was looking at TypeScript 4.9.5 on https://github.com/JoshuaKGoldberg/ts-api-utils/actions/runs/11544117529/job/32131517301?pr=545:

 FAIL  src/types/utilities.test.ts > isFalsyType > returns true when given 0n
 FAIL  src/types/utilities.test.ts > isFalsyType > returns true when given -0n
AssertionError: expected false to be true // Object.is equality

#531 will drop support for TS <4.8, but I reproduce this issue on TS 4.8 and 4.9 locally.

[kirkwaiblinger]

i'll take a look then! 👍

[JoshuaKGoldberg]

@all-contributors please add @kirkwaiblinger for code.

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[allcontributors]

@JoshuaKGoldberg

I've put up a pull request to add @kirkwaiblinger! 🎉