A TypeError is shown when this empty test is run. The error only happens if the import statement is importing STATS and TSTATS

test.ts

import { expect, test } from 'vitest'
import { STATS, type TStats } from 'types'


test('add stats', () => {
    // empty!
}

types.ts

type TStats = [
    number, 
    number, 
    number, 
    number
]

const STATS = {
    get ZERO():TStats { return [0, 0, 0, 0]    },
    get IDENTITY():TStats { return  [1, 1, 1, 1]},
    get BASE():TStats { return  [ 0, 350, 0.95, 100]},
}

Somewhere else in the codebase this file exists components.ts:

export const CStats = { 
    stats: new Array(  count).fill(STATS.BASE).map(() => STATS.BASE)
}

... and the test above produces this error message:

TypeError: Cannot read properties of undefined (reading 'BASE')
 ❯ src/components.ts:76:49

   export const CStats = {
       stats: new Array(count).fill( STATS.BASE).map(() => {return STATS.BASE})
                                                  ^
   }

I have no idea why this error message appears . The normal code runs without error. I tried it on typescript playground as well without any errors. I also added console.log messages in the map function before returning STATS.BASE. The code is executed.

type TStats = [
    number, 
    number, 
    number, 
    number
]

const STATS = {
    get ZERO():TStats { return [0, 0, 0, 0]    },
    get IDENTITY():TStats { return  [1, 1, 1, 1]},
    get BASE():TStats { return  [ 0, 350, 0.95, 100]},
}


const CBaseStats = {
    stats: new Array(5).fill( STATS.BASE).map(() => {return STATS.BASE})
}

Any hints where to check are welcome.

typescript playground

The setup: Typescript 5.9.3

vite@7.3.1

vitest@4.0.16