Refactoring: introduce method for reuse file for single class logic

idea/idea-analysis/src/org/jetbrains/kotlin/idea/KotlinIconProvider.kt

@@ -35,8 +35,8 @@ import javax.swing.Icon
 class KotlinIconProvider : IconProvider(), DumbAware {
     override fun getIcon(psiElement: PsiElement, flags: Int): Icon? {
         if (psiElement is KtFile) {
-            val mainClass = getMainClass(psiElement)
-            return if (mainClass != null && psiElement.declarations.size == 1) getIcon(mainClass, flags) else KotlinIcons.FILE
+            val mainClass = getSingleClass(psiElement)
+            return if (mainClass != null) getIcon(mainClass, flags) else KotlinIcons.FILE
         }
 
         val result = psiElement.getBaseIcon()
@@ -48,9 +48,13 @@ class KotlinIconProvider : IconProvider(), DumbAware {
     }
 
     companion object {
-
         var INSTANCE = KotlinIconProvider()
 
+        fun getSingleClass(file: KtFile): KtClassOrObject? {
+            val mainClass = getMainClass(file)
+            return if (mainClass != null && file.declarations.size == 1) mainClass else null
+        }
+
         fun getMainClass(file: KtFile): KtClassOrObject? {
             val classes = file.declarations.filterIsInstance<KtClassOrObject>()
             if (classes.size == 1 && StringUtil.getPackageName(file.name) == classes[0].name) {

idea/src/org/jetbrains/kotlin/idea/projectView/projectViewProviders.kt

@@ -49,10 +49,8 @@ class KotlinExpandNodeProjectViewProvider : TreeStructureProvider, DumbAware {
             val childValue = child.value?.asKtFile()
 
             if (childValue != null) {
-                val declarations = childValue.declarations
-
-                val mainClass = KotlinIconProvider.getMainClass(childValue)
-                if (mainClass != null && declarations.size == 1) {
+                val mainClass = KotlinIconProvider.getSingleClass(childValue)
+                if (mainClass != null) {
                     result.add(KtClassOrObjectTreeNode(childValue.project, mainClass, settings))
                 }
                 else {