State variable could be immutable

Severity: Gas ID: could-be-immutable

Flags state variables that are assigned only in the constructor and never written to afterward — making them eligible to be declared immutable.

What it does

Reports each non-constant, non-immutable state variable whose only writes occur in the constructor (or in initialization at declaration time).

Why is this bad?

immutable state variables are stored in the deployed bytecode rather than in storage, eliminating an SLOAD per access and saving substantial gas across the contract's lifetime. Declaring such variables immutable also expresses intent and prevents future writes.

Example

Bad

contract C {
    address owner;
    constructor() { owner = msg.sender; }
}

Good

contract C {
    address immutable OWNER;
    constructor() { OWNER = msg.sender; }
}

Notes

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