Unclear error message when checking NaN against the number type

[ghost]

When testing NaN against ow.number, the following error message is emitted:

ArgumentError: Expected argument to be of type `number` but received type `number`
at ow (node_modules/ow/dist/index.js:29:28) 
{
  validationErrors: Map(1) {
    'number' => Set(1) {
      'Expected argument to be of type `number` but received type `number`'
    }
  }
}

---

This behaviour can be verified by running this two line snippet in the Node REPL:

const { default: ow } = require('ow')
ow(NaN, ow.number)

---

I think that this error message would be quite confusing for those who encounter it. I see two possible ways to solve this problem:

• Change the error message in the NaN case to be something along the lines of: Expected argument to be of type `number`, but received `NaN`.
• Add specific ow.number.nan and ow.number.not.nan checks.

[sindresorhus]

I agree. That should be improved. I think we should do both suggestions.

[panva]

@sindresorhus would you prefer the first suggestion to be a breaking change in @sindresorhus/is or a special case added to ow?

[sindresorhus]

would you prefer the first suggestion to be a breaking change in @sindresorhus/is or a special case added to ow?

How would you fix it in @sindresorhus/is?

[panva]

@sindresorhus change https://github.com/sindresorhus/is/blob/v4.4.0/source/index.ts#L112-L113

to

        case 'number':
            return Number.isNaN(value) ? 'NaN' : 'number';

[sindresorhus]

Ah yes. Let's fix it in @sindresorhus/is, but it might take a while before we can do a major version there, so better to fix it in both places, actually.

[panva]

Ok, ignore #232 then.

[sindresorhus]

See comment update.