# Augmented assignment

## Basic

```py
x = 3
x -= 1
reveal_type(x)  # revealed: Literal[2]
```

## Dunder methods

```py
class C:
    def __isub__(self, other: int) -> str:
        return "Hello, world!"

x = C()
x -= 1
reveal_type(x)  # revealed: str
```

## Unsupported types

```py
class C:
    def __isub__(self, other: str) -> int:
        return 42

x = C()
x -= 1

# TODO: should error, once operand type check is implemented
reveal_type(x)  # revealed: int
```