Unwrapped modifier logic

Severity: CodeSize ID: unwrapped-modifier-logic

Flags modifiers whose body contains non-trivial logic that should be moved into a helper function to reduce contract code size.

What it does

Reports modifiers whose body contains statements other than a single placeholder, simple builtin calls (require/assert), or a single library function call. Logic on either side of the placeholder is considered independently; a side containing inline assembly is not extracted, but complex logic on the other side can still be flagged.

The lint only emits a machine-applicable rewrite when the modifier has exactly one top-level placeholder and extracting the logic preserves local-variable and parameter behavior.

Why is this bad?

Solidity inlines a modifier's body at every call site, so any non-trivial logic is duplicated across all functions that use the modifier. Wrapping the logic in an internal function and calling it from the modifier keeps the bytecode small while preserving behavior.

Example

Bad

modifier onlyAuth() {
    if (!auth[msg.sender]) revert NotAuth();
    bytes32 nonce = keccak256(abi.encodePacked(msg.sender, block.number));
    seenNonce[nonce] = true;
    _;
}

Good

modifier onlyAuth() {
    _checkAuth();
    _;
}

function _checkAuth() internal {
    if (!auth[msg.sender]) revert NotAuth();
    bytes32 nonce = keccak256(abi.encodePacked(msg.sender, block.number));
    seenNonce[nonce] = true;
}

Notes

This is a CodeSize-severity lint and is not applied to test or script files.