minus operator `-` does not necessarily return a `number`

[yukulele]

🔎 Search Terms

"minus operator", "minus bigint", "minus any"

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about "operator"

⏯ Playground Link

https://www.typescriptlang.org/play?target=7#code/MYewdgzgLgBAhgLjmAnjAvDAjABjAKABsBTWAIwxgFo58KBqTAViA

💻 Code

const a:any = 10n
let b = -a
b += 5 
// - tsc: no error
// - run: can't convert BigInt to number

🙁 Actual behavior

b type is number

🙂 Expected behavior

b type should be number | bigint

Additional information about the issue

Here's another example showing that other operators can potentially be affected

class A { [Symbol.toPrimitive] = () => 1n }

const a: A = new A()

const b = a.valueOf()
const c = -a
const d = ~a
// `b`, `c` and `d` types shound be `bigint`, right?

https://www.typescriptlang.org/play?target=7#code/MYGwhgzhAECC0G9oG0DKBPAtgIwPYgDoAXXABQCcBLTSoygNwFMBdaAXmgAoBKdgPmgBGAHbQAvgCgJwXMIhFoYAFxx20YYwDucHlJlyF2NWAL0wIAK6MA8gDNd++dGBqAtGGmynAEzUA-DwB6QOgAA2xQgBow4FDFYV9Q7ziidAAHRhgIAAtcCwTobEYw7EoAc0phIlCgA

[MartinJohns]

Duplicate of #49558.

[typescript-bot]

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