microsoft / microsoft/TypeScript
Arithmetic operations on type-parameters subtyping `bigint` are incorrectly inferred to have type `number`
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Descripción
### 🔎 Search Terms
bigint, operator, arithmetic, number, subtype, extend, generic, type parameter, incorrect, inference, inferred type, operation, 2365, TS2365
### 🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about arithmetic/bigints/etc
### ⏯ Playground Link
https://www.typescriptlang.org/play/?target=99&ts=5.8.2#code/GYVwdgxgLglg9mABAIxlAzgUygSTFTAJy2gB4AhNdRTADwLABNrUBzGfAPgAoBDALkSUMAGhSDh6AJSCwIALbIiiAN4AoRJsQB6bYg4FimaPCQxqHYEUKZGiKHEQALXgDdM9gJ4AHDwAM5RSI-REJeKCdlCN4kPzYDPw0tCAR0KH18IhJYBEQAXkReRAAyFABuNSTNXUQAVgA6AA56gCZQzG84QgxEMEcoHw9rLpEqnT1kEHSiwnBYeSHCQi7EOAgIEGJ+MZqAbQBRACVDgF1BAGEYvvT5GFohGFY8aaZViKjB9DEQLBpabwANjAIGhECkwO5iKZqGMbFBNmZMkYTLkALSIACMFQAvpVweg4ADMPUAXBWNxUBhsM8ssYoNwAOxgMS1MBSKQVIA
### 💻 Code
```ts
function bitsetIntersect(a: Bits, b: Bits): number {
// intersection is inferred to have type `number` rather than `bigint`
const intersection = a & b;
// 5.8.2 reports no type error,
// but a runtime error occurs:
// [ERR]: Cannot mix BigInt and other types, use explicit conversions
return intersection - 1;
}
console.log(bitsetIntersect(7n, 5n));
```
### 🙁 Actual behavior
`intersection` is inferred to have type `number`. As a result, no type errors are reported.
When run, the code encounters a TypeError because `intersection - 1` attempts to perform arithmetic on a bigint and a number:
> [ERR]: Cannot mix BigInt and other types, use explicit conversions
### 🙂 Expected behavior
`intersection` should be inferred to have type `bigint`.
Thus the operation `intersection - 1` should report a type error:
> Operator '-' cannot be applied to types 'bigint' and 'number'. (2365)
### Additional information about the issue
This issue is most likely to be hit when _branding_ `bigint`, but it could also appear in other situations, such as using subtypes which are unions of literals.
---
I found some issues that are similar, but have a different scope. These issues were closed as intended, but in these issues, larger type bounds which include `bigint` _but also include `number`_ (such as `any` or `bigint | number`) are used:
* #39569
* #41741
* #42125
* #49558
* #60914
Guía de contribución
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Línea de trabajo
Comienza ejecutando la reproducción enlazada de Playground y confirma el tipo inferido y el comportamiento de TS2365. Después, sigue la lógica del comprobador de tipos de TypeScript para las operaciones aritméticas sobre parámetros de tipo genéricos restringidos por bigint, añadiendo o localizando una prueba de regresión para el ejemplo. Se considera terminado cuando la intersección se trata como bigint y restar un number produce el error esperado.
Escrito por el modelo de indexación a partir del texto del issue.
Evaluación
- Stack tecnológico
- typescript
- Área
- compilers
- Tipo de issue
- Error
- Dificultad
- 4/5
- Tiempo estimado
- 3-5 días
- Estado de actividad
- Estancado
- Claridad
- Bastante claro
- Aptitud para principiantes
- 38/100