False positive "unused constructor" for local class

#KT-30637 Fixed

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

@@ -399,7 +399,10 @@ class UnusedSymbolInspection : AbstractKotlinInspection() {
 
     private fun KtCallableDeclaration.canBeHandledByLightMethods(descriptor: DeclarationDescriptor?): Boolean {
         return when {
-            descriptor is ConstructorDescriptor -> !descriptor.constructedClass.isInline
+            descriptor is ConstructorDescriptor -> {
+                val classDescriptor = descriptor.constructedClass
+                !classDescriptor.isInline && classDescriptor.visibility != Visibilities.LOCAL
+            }
             hasModifier(KtTokens.INTERNAL_KEYWORD) -> false
             descriptor !is FunctionDescriptor -> true
             else -> !descriptor.hasInlineClassParameters()

idea/testData/inspectionsLocal/unusedSymbol/secondaryLocalClassConstructor.kt

@@ -0,0 +1,10 @@
+// PROBLEM: none
+// WITH_RUNTIME
+
+fun main() {
+    class LocalClass(val number: Int) {
+        <caret>constructor(s: String) : this(s.toInt())
+    }
+
+    val l = LocalClass("42")
+}

idea/testData/quickfix/removeUnused/secondaryLocalClassConstructor.kt

@@ -0,0 +1,8 @@
+// "Safe delete constructor" "true"
+fun main() {
+    class LocalClass(val number: Int) {
+        <caret>constructor(s: String) : this(s.toInt())
+    }
+
+    val l = LocalClass(42)
+}

idea/testData/quickfix/removeUnused/secondaryLocalClassConstructor.kt.after

@@ -0,0 +1,7 @@
+// "Safe delete constructor" "true"
+fun main() {
+    class LocalClass(val number: Int) {
+    }
+
+    val l = LocalClass(42)
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -8728,6 +8728,11 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/unusedSymbol/propertyOfInlineClassType.kt");
         }
 
+        @TestMetadata("secondaryLocalClassConstructor.kt")
+        public void testSecondaryLocalClassConstructor() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unusedSymbol/secondaryLocalClassConstructor.kt");
+        }
+
         @TestMetadata("typeAlias.kt")
         public void testTypeAlias() throws Exception {
             runTest("idea/testData/inspectionsLocal/unusedSymbol/typeAlias.kt");

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -10121,6 +10121,11 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
             runTest("idea/testData/quickfix/removeUnused/notTriangle.kt");
         }
 
+        @TestMetadata("secondaryLocalClassConstructor.kt")
+        public void testSecondaryLocalClassConstructor() throws Exception {
+            runTest("idea/testData/quickfix/removeUnused/secondaryLocalClassConstructor.kt");
+        }
+
         @TestMetadata("simpleUnusedEnumEntry.kt")
         public void testSimpleUnusedEnumEntry() throws Exception {
             runTest("idea/testData/quickfix/removeUnused/simpleUnusedEnumEntry.kt");