Return Value Ignored

ID

go.return_value_ignored

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Go

Tags

dead-code, reliability

Description

Reports a statement that is just a call to a known pure function whose result is then discarded. A pure function has no observable side effect, so dropping its return value means the call does nothing.

Rationale

strings.ToUpper(s) on its own line looks like it transforms s, but strings are immutable in Go: the upper-cased copy is computed and thrown away while s is unchanged. This is almost always a typo for s = strings.ToUpper(s). The rule fires only when the call is the whole statement; a pure call whose result is assigned, returned or passed as an argument is fine. The set of functions treated as pure is conservative and configurable.

strings.ToUpper(s)               // FLAW — the upper-cased string is thrown away
s = strings.ToUpper(s)           // OK — result is assigned
fmt.Println(strings.ToUpper(s))  // OK — result is consumed as an argument

Remediation

Assign or otherwise use the result (s = strings.ToUpper(s)). If the call really is unnecessary, delete it. Tune the pureFunctions property to match the functions your project considers pure.

References