Mutable variable names should use mixedCase

Severity: Info ID: mixed-case-variable

Flags mutable variable names (locals, parameters, mutable state) that do not follow mixedCase.

What it does

Reports mutable variable identifiers that contain embedded underscores, start with an uppercase letter, or otherwise deviate from mixedCase. Leading and trailing underscores are preserved, and single-character names are not checked.

constant and immutable state variables are not flagged by this lint — see screaming-snake-case-const and screaming-snake-case-immutable.

Why is this bad?

The Solidity style guide recommends mixedCase for mutable variables. Consistent style makes code easier to scan and review.

Example

Bad

solidity

uint256 public total_supply;
address Owner;

Good

solidity

uint256 public totalSupply;
address owner;

Configuration

Set mixed_case_exceptions under [lint.lint_specific] in foundry.toml to replace the default list of allowed uppercase patterns (ERC, URI, ID, URL, API, JSON, XML, HTML, HTTP, and HTTPS):

toml

[lint.lint_specific]
mixed_case_exceptions = ["ERC", "URI", "NFT"]