# TS2654: Non-abstract class '…' is missing implementations for the following members of '…': ….

> A class extends an abstract class without implementing all of its abstract members. Implement them, or mark the subclass abstract.

## What it means

The base class has `abstract` members, and a concrete (non-abstract) subclass doesn't provide some
of them. The message lists the missing members. With only one missing member, the checker uses
TS2515 instead.

## Example

```ts
abstract class Shape {
  abstract area(): number;
  abstract name(): string;
}
class Square extends Shape {}
export {};
```

## How to fix

- Implement every listed member in the subclass.
- Or mark the subclass `abstract` and implement them further down.

Source: https://ts-r.dev/errors/TS2654/