[@typescript-eslint/no-base-to-string] is complaining about boolean values

[juergenzimmermann]

Are you opening an issue because the rule you're trying to use is not found?
No

Repro

Rule definition in YAML

@typescript-eslint/no-base-to-string": error

Blamed TypeScript code fragment:

const result = compareSync(password, user.password); // result is of type boolean
logger.error(`AuthService.checkPassword(): ${result}`);

Expected Result
No output

Actual Result
152:51 error 'result will evaluate to '[Object object]' when stringified @typescript-eslint/no-base-to-string

Additional Info

Versions

package	version
@typescript-eslint/eslint-plugin	2.21.1-alpha.5
@typescript-eslint/parser	2.21.1-alpha.5
TypeScript	3.8.3
ESLint	7.0.0-alpha.2
node	13.9.0
npm	6.14.1

[bradzacher]

Could you provide more information?
The type defs for everything would be great.

A small, self contained repro would be better.

[leaumar]

I can provide a live example: please check this PR (yarn install && yarn lint to reproduce)

The rule is complaining at Restrictions.ts:59 about a boolean in a template string

[felixfbecker]

Saw the same - I would expect the no-base-to-string to only be used for object types, as restrict-template-expression can already take care of the other

[bradzacher]

This is a bug.

Self-contained repro is `${true}`.

The rule grabs the toString property's declaration for the given type, and then asserts that the declaration does not come from the base Object type.

For some reason, boolean types return Object instead of Boolean.

For comparison, for both `${''}` and `${1}` the owner of the parent type is String and Number.

It seems like this bug is caused by a bug in typescript itself..

[bradzacher]

It is a bug in typescript, the library types are wrong.

Boolean has no toString defined
https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L529-L532
Neither does Error
https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L972-L984

Whereas other base types do:

• Symbol https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L99
• Function https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L296
• String https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L396
• Number https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.es5.d.ts#L547
• etc

[felixfbecker]

Maybe we should open an issue at the TS repo with a combined list of types with missing toString()? URLSearchParams also misses it

[bradzacher]

feel free if you'd like!

We can't rely on a forward fix for this plugin, as that adds a ~3month turnaround on the fix, and forces people to upgrade their TS version (with breaking changes), so the rule will have to be fixed to workaround regardless.

[felixfbecker]

I'd rather have a fix sooner than later too :)

Also noticed with RegExp and URL (and URLSearchParams as mentioned above)

[bradzacher]

note that URL already has a toString defined: https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.dom.d.ts#L16101
as does URLSearchParams: https://github.com/microsoft/TypeScript/blob/d209092ccc0ca9fee4fe5148c554484aab95e487/lib/lib.dom.d.ts#L16152

RegExp does not though

---

I tested URL and URLSearchParams against master using the dom lib, and they passed tests fine - so there might be something to do with your setup that's causing them to fail.