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Improve BeaconProxy documentation for storage slot #4438

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Jul 9, 2023
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Improve BeaconProxy documentation for storage slot #4438

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12 changes: 8 additions & 4 deletions contracts/proxy/beacon/BeaconProxy.sol
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Expand Up @@ -10,11 +10,15 @@ import {ERC1967Utils} from "../ERC1967/ERC1967Utils.sol";
/**
* @dev This contract implements a proxy that gets the implementation address for each call from an {UpgradeableBeacon}.
*
* The beacon address is stored in storage slot `uint256(keccak256('eip1967.proxy.beacon')) - 1`, so that it doesn't
* conflict with the storage layout of the implementation behind the proxy.
* The beacon address can only be set once during construction, and cannot be changed afterwards. It is stored in an immutable
* variable to avoid unnecessary storage reads, and also in the beacon storage slot specified by
* https://eips.ethereum.org/EIPS/eip-1967[EIP1967] so that it can be accessed externally.
*
* CAUTION: The beacon address can only be set once during construction, and cannot be changed afterwards.
* You must ensure that you either control the beacon, or trust the beacon to not upgrade the implementation maliciously.
* CAUTION: Since the beacon address can never be changed, you must ensure that you either control the beacon, or trust the
* beacon to not upgrade the implementation maliciously.
*
* IMPORTANT: Do not use the implementation logic to modify the beacon storage slot. Doing so would leave the proxy in an
* inconsistent state where the beacon storage slot does not match the beacon address.
*/
contract BeaconProxy is Proxy {
// An immutable address for the beacon to avoid unnecessary SLOADs before each delegate call.
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