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Unused variable — CodeQL query help documentation

ID: rust/unused-variable
Kind: problem
Security severity: 
Severity: recommendation
Precision: high
Tags:
   - maintainability
   - quality
Query suites:
   - rust-code-quality.qls
   - rust-security-and-quality.qls

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This rule finds variables that are never accessed. Unused variables should be removed to increase readability and avoid confusion.

Recommendation

Remove any unused variables.

Example

In the following example, there is an unused variable average that is never used:

fn get_sum(values:&[i32]) -> i32 {
	let mut sum = 0;
	let mut average; // BAD: unused variable

	for v in values {
		sum += v;
	}

	return sum;
}

The problem can be fixed simply by removing the variable:

fn get_sum(values:&[i32]) -> i32 {
	let mut sum = 0;

	for v in values {
		sum += v;
	}

	return sum;
}

References