Unused symbol: don't report for finalize() method #KT-13311 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/ProtectedInFinalInspection.kt

@@ -9,16 +9,16 @@ import com.intellij.codeInsight.FileModificationService
 import com.intellij.codeInspection.*
 import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElementVisitor
-import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.idea.core.implicitVisibility
 import org.jetbrains.kotlin.idea.core.isInheritable
-import org.jetbrains.kotlin.idea.search.usagesSearch.descriptor
+import org.jetbrains.kotlin.idea.intentions.isFinalizeMethod
 import org.jetbrains.kotlin.lexer.KtTokens
-import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.KtClass
+import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.addRemoveModifier.addModifier
+import org.jetbrains.kotlin.psi.declarationVisitor
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
-import org.jetbrains.kotlin.types.typeUtil.isUnit
 
 class ProtectedInFinalInspection : AbstractKotlinInspection() {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
@@ -43,13 +43,6 @@ class ProtectedInFinalInspection : AbstractKotlinInspection() {
         })
     }
 
-    private fun KtDeclaration.isFinalizeMethod(): Boolean {
-        val function = this as? KtNamedFunction ?: return false
-        return function.name == "finalize"
-                && function.valueParameters.isEmpty()
-                && (function.descriptor as? FunctionDescriptor)?.returnType?.isUnit() == true
-    }
-
     class MakePrivateFix : LocalQuickFix {
         override fun getName(): String = "Make private"
 

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedSymbolInspection.kt

@@ -46,6 +46,7 @@ import org.jetbrains.kotlin.idea.core.toDescriptor
 import org.jetbrains.kotlin.idea.findUsages.KotlinFindUsagesHandlerFactory
 import org.jetbrains.kotlin.idea.findUsages.handlers.KotlinFindClassUsagesHandler
 import org.jetbrains.kotlin.idea.imports.importableFqName
+import org.jetbrains.kotlin.idea.intentions.isFinalizeMethod
 import org.jetbrains.kotlin.idea.isMainFunction
 import org.jetbrains.kotlin.idea.project.languageVersionSettings
 import org.jetbrains.kotlin.idea.quickfix.RemoveUnusedFunctionParameterFix
@@ -168,6 +169,7 @@ class UnusedSymbolInspection : AbstractKotlinInspection() {
             val descriptor = declaration.resolveToDescriptorIfAny() ?: return
             if (descriptor is FunctionDescriptor && descriptor.isOperator) return
             if (isEntryPoint(declaration)) return
+            if (declaration.isFinalizeMethod(descriptor)) return
             if (declaration is KtProperty && declaration.isSerializationImplicitlyUsedField()) return
             if (declaration is KtNamedFunction && declaration.isSerializationImplicitlyUsedMethod()) return
             // properties can be referred by component1/component2, which is too expensive to search, don't mark them as unused
@@ -283,7 +285,7 @@ class UnusedSymbolInspection : AbstractKotlinInspection() {
                         if (import.importedFqName != declaration.fqName) {
                             val importedDeclaration =
                                 import.importedReference?.getQualifiedElementSelector()?.mainReference?.resolve() as? KtNamedDeclaration
-                                        ?: return true
+                                    ?: return true
                             if (declaration is KtObjectDeclaration ||
                                 (declaration is KtClass && declaration.isEnum()) ||
                                 importedDeclaration.containingClassOrObject is KtObjectDeclaration

idea/src/org/jetbrains/kotlin/idea/intentions/Utils.kt

@@ -19,17 +19,17 @@ package org.jetbrains.kotlin.idea.intentions
 import com.intellij.psi.tree.IElementType
 import org.jetbrains.kotlin.KtNodeTypes
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
-import org.jetbrains.kotlin.descriptors.CallableDescriptor
-import org.jetbrains.kotlin.descriptors.PackageFragmentDescriptor
-import org.jetbrains.kotlin.descriptors.ValueParameterDescriptor
+import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.core.setType
 import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.idea.search.usagesSearch.descriptor
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.containingClass
 import org.jetbrains.kotlin.psi.psiUtil.getCallNameExpression
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 import org.jetbrains.kotlin.resolve.BindingContext
@@ -40,6 +40,7 @@ import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.resolve.source.getPsi
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.isFlexible
+import org.jetbrains.kotlin.types.typeUtil.isUnit
 import java.lang.IllegalArgumentException
 
 fun KtContainerNode.description(): String? {
@@ -311,4 +312,12 @@ fun KtBlockExpression.getParentLambdaLabelName(): String? {
     return lambdaLabelName ?: callExpression.getCallNameExpression()?.text
 }
 
-internal fun KtExpression.getCallableDescriptor() = resolveToCall()?.resultingDescriptor
+internal fun KtExpression.getCallableDescriptor() = resolveToCall()?.resultingDescriptor
+
+fun KtDeclaration.isFinalizeMethod(descriptor: DeclarationDescriptor? = null): Boolean {
+    if (containingClass() == null) return false
+    val function = this as? KtNamedFunction ?: return false
+    return function.name == "finalize"
+            && function.valueParameters.isEmpty()
+            && ((descriptor ?: function.descriptor) as? FunctionDescriptor)?.returnType?.isUnit() == true
+}

idea/testData/inspections/unusedSymbol/function/finalize.kt

@@ -0,0 +1,4 @@
+class C {
+    protected fun finalize() {
+    }
+}

idea/testData/inspections/unusedSymbol/function/inspectionData/expected.xml

@@ -87,4 +87,13 @@
     <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused symbol</problem_class>
     <description>Function &quot;foo&quot; is never used</description>
   </problem>
+
+  <problem>
+    <file>finalize.kt</file>
+    <line>1</line>
+    <module>light_idea_test_case</module>
+    <entry_point TYPE="file" FQNAME="temp:///src/finalize.kt" />
+    <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused symbol</problem_class>
+    <description>Class "C" is never used</description>
+  </problem>
 </problems>