Unused Setter Value

ID

swift.unused_setter_value

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Swift

Tags

dead-code, reliability, suspicious-code

Description

Reports a property or subscript setter whose body never reads the incoming value. The implicit newValue (or the explicit name in set(other)) is what the caller assigned — ignoring it makes the assignment a silent no-op for that caller.

var name: String {
    get { _name }
    set { _name = "fixed" }            // FLAW — newValue unused
}

var named: String {
    get { _named }
    set(other) { _named = "fixed" }    // FLAW — `other` unused
}

var name: String {
    get { _name }
    set { _name = newValue }           // OK
}

Rationale

Property assignments look like field assignments, so callers expect obj.prop = x to store x. A setter that ignores its argument silently breaks that contract — the most common cause is a copy-paste from a getter that was never finished. Even when the intent really is "ignore writes," that intent should be expressed with a get-only property, not a setter that drops the value.

Remediation

Use the new value:

var name: String {
    get { _name }
    set { _name = newValue }
}

If the property is meant to be read-only from the outside, drop the setter entirely and expose only the getter (or mark the storage private(set)).

References