/
UnusedUnaryOperator.kt
78 lines (69 loc) · 2.92 KB
/
UnusedUnaryOperator.kt
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package io.gitlab.arturbosch.detekt.rules.bugs
import io.gitlab.arturbosch.detekt.api.CodeSmell
import io.gitlab.arturbosch.detekt.api.Config
import io.gitlab.arturbosch.detekt.api.Debt
import io.gitlab.arturbosch.detekt.api.Entity
import io.gitlab.arturbosch.detekt.api.Issue
import io.gitlab.arturbosch.detekt.api.Rule
import io.gitlab.arturbosch.detekt.api.Severity
import io.gitlab.arturbosch.detekt.api.internal.ActiveByDefault
import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution
import org.jetbrains.kotlin.builtins.KotlinBuiltIns
import org.jetbrains.kotlin.com.intellij.psi.PsiComment
import org.jetbrains.kotlin.com.intellij.psi.PsiWhiteSpace
import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
import org.jetbrains.kotlin.lexer.KtTokens
import org.jetbrains.kotlin.psi.KtBinaryExpression
import org.jetbrains.kotlin.psi.KtExpression
import org.jetbrains.kotlin.psi.KtPrefixExpression
import org.jetbrains.kotlin.psi.psiUtil.leaves
import org.jetbrains.kotlin.psi.psiUtil.parents
import org.jetbrains.kotlin.resolve.BindingContext
import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsExpression
import org.jetbrains.kotlin.resolve.calls.util.getResolvedCall
/**
* This rule detects unused unary operators.
*
* <noncompliant>
* val x = 1 + 2
* + 3 + 4
* println(x) // 3
* </noncompliant>
*
* <compliant>
* val x = 1 + 2 + 3 + 4
* println(x) // 10
* </compliant>
*
*/
@RequiresTypeResolution
@ActiveByDefault(since = "1.21.0")
class UnusedUnaryOperator(config: Config = Config.empty) : Rule(config) {
override val issue = Issue(
javaClass.simpleName,
Severity.Defect,
"This unary operator is unused.",
Debt.FIVE_MINS
)
@Suppress("ReturnCount")
override fun visitPrefixExpression(expression: KtPrefixExpression) {
super.visitPrefixExpression(expression)
if (expression.baseExpression == null) return
val operationToken = expression.operationToken
if (operationToken != KtTokens.PLUS && operationToken != KtTokens.MINUS) return
if (expression.node.leaves(forward = false)
.takeWhile { it is PsiWhiteSpace || it is PsiComment }
.none { it is PsiWhiteSpace && it.textContains('\n') }
) return
val parentOrSelf = expression.parentBinaryExpressionOrThis()
if (parentOrSelf.isUsedAsExpression(bindingContext)) return
val operatorDescriptor = expression.operationReference.getResolvedCall(bindingContext)
?.resultingDescriptor as? DeclarationDescriptor ?: return
if (!KotlinBuiltIns.isUnderKotlinPackage(operatorDescriptor)) return
val message = "This '${parentOrSelf.text}' is not used"
report(CodeSmell(issue, Entity.from(expression), message))
}
private fun KtExpression.parentBinaryExpressionOrThis(): KtExpression {
return parents.takeWhile { it is KtBinaryExpression }.lastOrNull() as? KtBinaryExpression ?: this
}
}