[IR] Simplify ExpectActualCollector, remove nesting

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/actualizer/ExpectActualCollector.kt

@@ -23,7 +23,7 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
         val result = mutableMapOf<IrSymbol, IrSymbol>()
         // Collect and link classifiers at first to make it possible to expand type aliases on the callables linking
         val (allActualDeclarations, typeAliasMap) = result.appendExpectActualClassifiersMap()
-        result.appendExpectActualCallablesMap(allActualDeclarations, typeAliasMap, dependentFragments)
+        result.appendExpectActualCallablesMap(allActualDeclarations, typeAliasMap)
         return result to typeAliasMap
     }
 
@@ -44,11 +44,23 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
         return allActualDeclarations to typeAliasMap
     }
 
-    class ActualClassifiersCollector(
+    private fun MutableMap<IrSymbol, IrSymbol>.appendExpectActualCallablesMap(
+        allActualDeclarations: Set<IrDeclaration>,
+        typeAliasMap: Map<FqName, FqName>
+    ) {
+        val actualMembers = mutableMapOf<String, IrDeclarationBase>()
+
+        collectActualCallables(this, actualMembers, allActualDeclarations)
+        val collector = CallablesLinkCollector(this, actualMembers, typeAliasMap)
+        dependentFragments.forEach { collector.visitModuleFragment(it) }
+    }
+}
+
+private class ActualClassifiersCollector(
     private val actualClassifiers: MutableMap<FqName, IrSymbol>,
     private val allActualClassifiers: MutableSet<IrDeclaration>,
     private val typeAliasMap: MutableMap<FqName, FqName>
-    ) : IrElementVisitor<Unit, Boolean> {
+) : IrElementVisitor<Unit, Boolean> {
     override fun visitTypeAlias(declaration: IrTypeAlias, data: Boolean) {
         if (declaration.isActual) {
             val expandedTypeSymbol = declaration.expandedType.classifierOrFail
@@ -90,12 +102,12 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
     override fun visitElement(element: IrElement, data: Boolean) {
         element.acceptChildren(this, data)
     }
-    }
+}
 
-    class ClassifiersLinkCollector(
+private class ClassifiersLinkCollector(
     private val expectActualMap: MutableMap<IrSymbol, IrSymbol>,
     private val actualClassifiers: Map<FqName, IrSymbol>
-    ) : IrElementVisitorVoid {
+) : IrElementVisitorVoid {
     private fun addLinkOrReportMissing(expectElement: IrSymbolOwner, actualTypeId: FqName) {
         val actualClassifier = actualClassifiers[actualTypeId]
         if (actualClassifier != null) {
@@ -124,25 +136,13 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
     override fun visitElement(element: IrElement) {
         element.acceptChildrenVoid(this)
     }
-    }
+}
 
-    private fun MutableMap<IrSymbol, IrSymbol>.appendExpectActualCallablesMap(
+private fun collectActualCallables(
-        allActualDeclarations: Set<IrDeclaration>,
-        typeAliasMap: Map<FqName, FqName>,
-        dependentFragments: List<IrModuleFragment>
-    ) {
-        val actualMembers = mutableMapOf<String, IrDeclarationBase>()
-
-        collectActualCallables(this, actualMembers, allActualDeclarations)
-        val collector = CallablesLinkCollector(this, actualMembers, typeAliasMap)
-        dependentFragments.forEach { collector.visitModuleFragment(it) }
-    }
-
-    private fun collectActualCallables(
     expectActualMap: MutableMap<IrSymbol, IrSymbol>,
     actualMembers: MutableMap<String, IrDeclarationBase>,
     allActualDeclarations: Set<IrDeclaration>,
-    ) {
+) {
     fun collectActualsCallables(declaration: IrDeclaration) {
         when (declaration) {
             is IrFunction,
@@ -160,13 +160,13 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
     for (actualDeclaration in allActualDeclarations) {
         collectActualsCallables(actualDeclaration)
     }
-    }
+}
 
-    class CallablesLinkCollector(
+private class CallablesLinkCollector(
     private val expectActualMap: MutableMap<IrSymbol, IrSymbol>,
     private val actualMembers: Map<String, IrDeclarationBase>,
     private val typeAliasMap: Map<FqName, FqName>
-    ) : IrElementVisitorVoid {
+) : IrElementVisitorVoid {
     override fun visitFunction(declaration: IrFunction) = addLink(declaration)
 
     override fun visitProperty(declaration: IrProperty) = addLink(declaration)
@@ -189,5 +189,4 @@ internal class ExpectActualCollector(private val mainFragment: IrModuleFragment,
     override fun visitElement(element: IrElement) {
         element.acceptChildrenVoid(this)
     }
-    }
 }