suspicious-operator-implementation

Disallow direct operator implementations built on a different operator

Directly combining an operator receiver and operand with a different operator commonly indicates a copied or mistyped body.
Instead, you SHOULD use the operator implemented by the enclosing protocol.

- Category: suspicious
- Level: warning
- Fix: none
- Scope: module

Reported

struct Score {
    value: int32;
}

extension of Score implements Add<Score> {
    type Output = Score;

    add(&readonly this, other: Score): Score {
        return Score { value: this.value - other.value };
    }
}
Accepted

struct Score {
    value: int32;
}

extension of Score implements Add<Score> {
    type Output = Score;

    add(&readonly this, other: Score): Score {
        return Score { value: this.value + other.value };
    }
}
Prior art

- Clippy · suspiciousarithmeticimpl
- Clippy · suspiciousopassignimpl

language/linter/src/rules/suspicious/suspiciousoperatorimplementation.rs:7