State variable read via this

Severity: Gas ID: var-read-using-this

Flags reads of the contract's own state through this.X(...). Calling a public state-variable getter or any view/pure function via this performs an external STATICCALL to the same address, paying the call overhead for data that could be read directly.

What it does

Reports this.<name>(<args>) calls where <name> resolves (via overload resolution by arity) to a function reachable on the contract's external interface (public or external) whose state mutability is view or pure. This includes:

• The auto-generated getter for any public state variable (simple variables, mappings, arrays).
• Any inherited public/external view/pure function declared in a base contract.

When the offending call is the auto-generated getter for a state variable, the lint emits a code fix:

• Simple state variable: this.foo() → foo (machine-applicable).
• Mapping/array getter: this.m(k) → m[k] (maybe-incorrect; double-check the rewrite).

Calls that carry call options (e.g. this.foo{gas: 1000}()) are still flagged, but no fix is suggested — the developer is intentionally reaching for the external-call machinery.

Why is this bad?

Each this.X(...) call compiles to a STATICCALL to the contract's own address. That costs a fixed amount of gas, plus the encoding/decoding of arguments and return data, in addition to the storage read itself. Reading the variable directly skips the call entirely.

Example

Bad

contract C {
    uint256 public counter;
    mapping(uint256 => address) public owners;

    function readDirect() external view returns (uint256, address) {
        // Each `this.X` performs an unnecessary STATICCALL.
        return (this.counter(), this.owners(0));
    }
}

Good

contract C {
    uint256 public counter;
    mapping(uint256 => address) public owners;

    function readDirect() external view returns (uint256, address) {
        // Direct storage reads — no external call.
        return (counter, owners[0]);
    }
}

Notes

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

For external view/pure functions, calling them via this from inside the contract is the only in-contract syntax that resolves; the recommended fix is to extract the body into an internal helper that both the external entry point and the local caller invoke.