> For the complete documentation index, see [llms.txt](https://docs.rigoblock.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rigoblock.com/solidity-api-reference/protocol/core/sys/mixinfallback.md).

# MixinFallback

## MixinFallback

### PoolImplementationDirectCallNotAllowed

```solidity
error PoolImplementationDirectCallNotAllowed()
```

### PoolMethodNotAllowed

```solidity
error PoolMethodNotAllowed()
```

### PoolVersionNotSupported

```solidity
error PoolVersionNotSupported()
```

### onlyDelegateCall

```solidity
modifier onlyDelegateCall()
```

### fallback

```solidity
fallback() external
```

Delegate calls to pool extension.

*Extensions are persistent, while adapters are upgradable by the governance. uses shouldDelegatecall to flag selectors that should prompt a delegatecall.*

### receive

```solidity
receive() external payable
```

Allows transfers to pool.

*Prevents accidental transfer to implementation contract.*