IR: allow SymbolTable descendants

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/SymbolTable.kt

@@ -60,7 +60,7 @@ interface ReferenceSymbolTable {
     fun leaveScope(owner: IrDeclaration)
 }
 
-class SymbolTable(
+open class SymbolTable(
     val signaturer: IdSignatureComposer,
     val irFactory: IrFactory,
     val nameProvider: NameProvider = NameProvider.DEFAULT
@@ -71,7 +71,7 @@ class SymbolTable(
     @Suppress("LeakingThis")
     val lazyWrapper = IrLazySymbolTable(this)
 
-    private abstract class SymbolTableBase<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>>(val lock: IrLock) {
+    protected abstract class SymbolTableBase<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>>(val lock: IrLock) {
         val unboundSymbols = linkedSetOf<S>()
 
         abstract fun get(d: D): S?
@@ -212,7 +212,7 @@ class SymbolTable(
         }
     }
 
-    private open inner class FlatSymbolTable<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>> :
+    protected open inner class FlatSymbolTable<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>> :
         SymbolTableBase<D, B, S>(lock) {
         val descriptorToSymbol = linkedMapOf<D, S>()
         val idSigToSymbol = linkedMapOf<IdSignature, S>()
@@ -249,11 +249,11 @@ class SymbolTable(
         override fun signature(descriptor: ClassDescriptor): IdSignature? = signaturer.composeEnumEntrySignature(descriptor)
     }
 
-    private inner class FieldSymbolTable : FlatSymbolTable<PropertyDescriptor, IrField, IrFieldSymbol>() {
+    protected inner class FieldSymbolTable : FlatSymbolTable<PropertyDescriptor, IrField, IrFieldSymbol>() {
         override fun signature(descriptor: PropertyDescriptor): IdSignature? = signaturer.composeFieldSignature(descriptor)
     }
 
-    private inner class ScopedSymbolTable<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>>
+    protected inner class ScopedSymbolTable<D : DeclarationDescriptor, B : IrSymbolOwner, S : IrBindableSymbol<D, B>>
         : SymbolTableBase<D, B, S>(lock) {
         inner class Scope(val owner: IrSymbol, val parent: Scope?) {
             private val descriptorToSymbol = linkedMapOf<D, S>()
@@ -308,7 +308,7 @@ class SymbolTable(
             fun dump(): String = dumpTo(StringBuilder()).toString()
         }
 
-        private var currentScope: Scope? = null
+        protected var currentScope: Scope? = null
 
         override fun get(d: D): S? {
             val scope = currentScope ?: return null
@@ -372,13 +372,13 @@ class SymbolTable(
     private val classSymbolTable = FlatSymbolTable<ClassDescriptor, IrClass, IrClassSymbol>()
     private val constructorSymbolTable = FlatSymbolTable<ClassConstructorDescriptor, IrConstructor, IrConstructorSymbol>()
     private val enumEntrySymbolTable = EnumEntrySymbolTable()
-    private val fieldSymbolTable = FieldSymbolTable()
+    protected val fieldSymbolTable = FieldSymbolTable()
     private val simpleFunctionSymbolTable = FlatSymbolTable<FunctionDescriptor, IrSimpleFunction, IrSimpleFunctionSymbol>()
     private val propertySymbolTable = FlatSymbolTable<PropertyDescriptor, IrProperty, IrPropertySymbol>()
     private val typeAliasSymbolTable = FlatSymbolTable<TypeAliasDescriptor, IrTypeAlias, IrTypeAliasSymbol>()
 
-    private val globalTypeParameterSymbolTable = FlatSymbolTable<TypeParameterDescriptor, IrTypeParameter, IrTypeParameterSymbol>()
+    protected val globalTypeParameterSymbolTable = FlatSymbolTable<TypeParameterDescriptor, IrTypeParameter, IrTypeParameterSymbol>()
-    private val scopedTypeParameterSymbolTable by threadLocal {
+    protected val scopedTypeParameterSymbolTable by threadLocal {
         ScopedSymbolTable<TypeParameterDescriptor, IrTypeParameter, IrTypeParameterSymbol>()
     }
     private val valueParameterSymbolTable by threadLocal {
@@ -703,7 +703,7 @@ class SymbolTable(
     override fun referenceField(descriptor: PropertyDescriptor) =
         fieldSymbolTable.referenced(descriptor) { createFieldSymbol(descriptor) }
 
-    override fun referenceFieldFromLinker(sig: IdSignature) =
+    override fun referenceFieldFromLinker(sig: IdSignature): IrFieldSymbol =
         fieldSymbolTable.run {
             if (sig.isPubliclyVisible) IrFieldPublicSymbolImpl(sig) else IrFieldSymbolImpl()
         }
@@ -928,7 +928,7 @@ class SymbolTable(
             typeParameterFactory
         )
 
-    fun declareGlobalTypeParameter(
+    open fun declareGlobalTypeParameter(
         sig: IdSignature,
         symbolFactory: () -> IrTypeParameterSymbol,
         typeParameterFactory: (IrTypeParameterSymbol) -> IrTypeParameter
@@ -963,6 +963,7 @@ class SymbolTable(
             typeParameterFactory
         )
 
+    @Suppress("UNUSED_PARAMETER")
     fun declareScopedTypeParameter(
         sig: IdSignature,
         symbolFactory: (IdSignature) -> IrTypeParameterSymbol,