Unused symbol: fix message for interface #KT-28286 Fixed

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

@@ -23,7 +23,7 @@ import org.jetbrains.kotlin.psi.psiUtil.isPropertyParameter
  * @return string description of declaration, like `Function "describe"`
  */
 fun KtNamedDeclaration.describe(): String? = when (this) {
-    is KtClass -> "Class \"$name\""
+    is KtClass -> "${if (isInterface()) "Interface" else "Class"} \"$name\""
     is KtObjectDeclaration -> "Object \"$name\""
     is KtNamedFunction -> "Function \"$name\""
     is KtSecondaryConstructor -> "Constructor"

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

@@ -79,4 +79,12 @@
     <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused symbol</problem_class>
     <description>Property ''bar'' is never used</description>
   </problem>
+  <problem>
+    <file>interface.kt</file>
+    <line>1</line>
+    <module>light_idea_test_case</module>
+    <entry_point TYPE="file" FQNAME="temp:///src/interface.kt" />
+    <problem_class severity="WARNING" attribute_key="NOT_USED_ELEMENT_ATTRIBUTES">Unused Symbol</problem_class>
+    <description>Interface 'Interface' is never used</description>
+  </problem>
 </problems>

idea/testData/inspections/unusedSymbol/class/interface.kt

@@ -0,0 +1 @@
+interface Interface