# TS2320: Interface '…' cannot simultaneously extend types '…' and '…'.

> An interface extends two types that declare the same property with different types. Make them agree, or redeclare the property in the interface.

## What it means

When an interface extends several types, their members are combined. If two of them have a
member with the same name but incompatible types, the interface can't extend both.

## Example

```ts
interface A {
  id: string;
}
interface B {
  id: number;
}

export interface C extends A, B {}
```

## How to fix

- Make the member's type the same in both bases.
- Or declare the member in the extending interface with a type assignable to both.

Source: https://ts-r.dev/errors/TS2320/