use references search for unused symbol inspection

idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinReferencesSearcher.kt

@@ -33,6 +33,7 @@ import org.jetbrains.kotlin.idea.references.JetSimpleNameReference
 import org.jetbrains.kotlin.idea.search.KOTLIN_NAMED_ARGUMENT_SEARCH_CONTEXT
 import org.jetbrains.kotlin.idea.search.usagesSearch.UsagesSearchLocation
 import org.jetbrains.kotlin.idea.search.usagesSearch.dataClassComponentFunction
+import org.jetbrains.kotlin.idea.search.usagesSearch.getClassNameForCompanionObject
 import org.jetbrains.kotlin.idea.search.usagesSearch.getSpecialNamesToSearch
 import org.jetbrains.kotlin.idea.stubindex.JetSourceFilterScope
 import org.jetbrains.kotlin.idea.util.ProjectRootsUtil
@@ -49,7 +50,9 @@ public class KotlinReferencesSearcher : QueryExecutorBase<PsiReference, Referenc
         val unwrappedElement = element.namedUnwrappedElement
         if (unwrappedElement == null || !ProjectRootsUtil.isInProjectOrLibSource(unwrappedElement)) return
 
-        val words = unwrappedElement.getSpecialNamesToSearch()
+        val classNameForCompanionObject = unwrappedElement.getClassNameForCompanionObject()
+        val words = unwrappedElement.getSpecialNamesToSearch() +
+                    (if (classNameForCompanionObject != null) listOf(classNameForCompanionObject) else emptyList())
 
         val effectiveSearchScope = runReadAction { queryParameters.effectiveSearchScope }
 

idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/searchHelpers.kt

@@ -76,7 +76,7 @@ fun PsiNamedElement.getAccessorNames(readable: Boolean = true, writable: Boolean
 }
 
 public fun PsiNamedElement.getClassNameForCompanionObject(): String? {
-    return if (this is JetObjectDeclaration) {
+    return if (this is JetObjectDeclaration && this.isCompanion()) {
         getNonStrictParentOfType<JetClass>()?.getName()
     } else {
         null

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

@@ -33,6 +33,9 @@ import com.intellij.psi.search.PsiSearchHelper
 import com.intellij.psi.search.PsiSearchHelper.SearchCostResult.FEW_OCCURRENCES
 import com.intellij.psi.search.PsiSearchHelper.SearchCostResult.TOO_MANY_OCCURRENCES
 import com.intellij.psi.search.PsiSearchHelper.SearchCostResult.ZERO_OCCURRENCES
+import com.intellij.psi.search.SearchScope
+import com.intellij.psi.search.searches.DefinitionsScopedSearch
+import com.intellij.psi.search.searches.ReferencesSearch
 import com.intellij.refactoring.safeDelete.SafeDeleteHandler
 import com.intellij.util.Processor
 import org.jetbrains.kotlin.asJava.LightClassUtil
@@ -47,6 +50,7 @@ import org.jetbrains.kotlin.lexer.JetTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getElementTextWithContext
 import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
+import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.isAncestor
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.types.expressions.OperatorConventions
@@ -233,23 +237,31 @@ public class UnusedSymbolInspection : AbstractKotlinInspection() {
             }
         }
 
-        val searchHelper: UsagesSearchHelper<out JetNamedDeclaration> = when (declaration) {
-            is JetClassOrObject -> ClassUsagesSearchHelper(constructorUsages = true, nonConstructorUsages = true, skipImports = true)
-            is JetNamedFunction -> FunctionUsagesSearchHelper(skipImports = true)
-            is JetProperty, is JetParameter -> PropertyUsagesSearchHelper(skipImports = true, namedArgumentUsages = false)
-            else -> DefaultSearchHelper<JetNamedDeclaration>()
-        }
 
-        val request = searchHelper.newRequest(UsagesSearchTarget(declaration, useScope))
-        val query = UsagesSearch.search(request)
+        return hasReferences(declaration, useScope) ||
+               hasOverrides(declaration, useScope) ||
+               hasCompanionObjectMemberUsages(declaration, useScope)
+    }
 
-        return !query.forEach(Processor {
-            assert(it != null, { "Found reference is null, was looking for: " + declaration.getElementTextWithContext() +
-                                 " findAll(): " + query.findAll().map { it?.getElement()?.let{ it.getElementTextWithContext() } } })
-            declaration.isAncestor(it.getElement()) || it.getElement().getParent() is JetValueArgumentName
+    private fun hasReferences(declaration: JetNamedDeclaration, useScope: SearchScope): Boolean {
+        return !ReferencesSearch.search(declaration, useScope).forEach(Processor {
+            assert(it != null, { "Found reference is null, was looking for: " + declaration.getElementTextWithContext() })
+            declaration.isAncestor(it.getElement()) ||
+            it.element.parent is JetValueArgumentName ||
+            it.element.getParentOfType<JetImportDirective>(false) != null
         })
     }
 
+    private fun hasOverrides(declaration: JetNamedDeclaration, useScope: SearchScope): Boolean {
+        return DefinitionsScopedSearch.search(declaration, useScope).findFirst() != null
+    }
+
+    private fun hasCompanionObjectMemberUsages(declaration: JetNamedDeclaration, useScope: SearchScope): Boolean {
+        if (declaration !is JetObjectDeclaration || !declaration.isCompanion()) return false
+
+        return declaration.declarations.any { it is JetNamedDeclaration && hasReferences(it, useScope) }
+    }
+
     override fun createOptionsPanel(): JComponent? {
         val panel = JPanel(GridBagLayout())
         panel.add(