Prefer custom errors over revert strings

Severity: Gas ID: custom-errors

Flags require(cond), require(cond, "message"), revert("message"), and revert() calls; suggests replacing them with a revert CustomError(...).

What it does

Reports require calls with no reason or whose second argument is a string literal, and revert(...) calls that are either bare or have a string-literal argument.

Why is this bad?

Custom errors:

• cost less gas than encoding/decoding a string,
• can carry typed parameters for richer diagnostics,
• shrink contract bytecode (string constants live in code).

Solidity 0.8.4+ supports custom errors natively.

Example

Bad

require(amount > 0, "amount must be > 0");
require(amount > 0);
revert("not authorized");
revert();

Good

error AmountZero();
error NotAuthorized();

if (amount == 0) revert AmountZero();
if (!authorized) revert NotAuthorized();

Notes

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