[FakeOverrideBuilder] Fix referencing a local type from a return type

Copying tree part happens in two stages.
1. Collect all symbols to copy and create new version of them
2. Do copy tree, replacing collected symbols

For f/o builder 1-st stage traversed more nodes, than seconds.
This led to unbound symbols in tree.

^KT-65273 Fixed

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/CopyIrTreeWithSymbolsForFakeOverrides.kt

@@ -5,10 +5,11 @@
 
 package org.jetbrains.kotlin.ir.overrides
 
-import org.jetbrains.kotlin.ir.declarations.IrClass
-import org.jetbrains.kotlin.ir.declarations.IrOverridableMember
-import org.jetbrains.kotlin.ir.declarations.IrTypeParametersContainer
+import org.jetbrains.kotlin.ir.declarations.*
+import org.jetbrains.kotlin.ir.expressions.IrBlockBody
 import org.jetbrains.kotlin.ir.expressions.IrConstructorCall
+import org.jetbrains.kotlin.ir.expressions.IrExpression
+import org.jetbrains.kotlin.ir.expressions.IrExpressionBody
 import org.jetbrains.kotlin.ir.symbols.IrClassifierSymbol
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
@@ -98,6 +99,17 @@ class CopyIrTreeWithSymbolsForFakeOverrides(
         private val typeArguments: Map<IrTypeParameterSymbol, IrType>,
         descriptorsRemapper: DescriptorsRemapper
     ) : DeepCopySymbolRemapper(descriptorsRemapper) {
+
+        // We need to avoid visiting parts of the tree that would not be visited by [FakeOverrideCopier]
+        // Otherwise, we can record symbols inside them for rebinding, but would not actually copy them.
+        // Normally, this is not important, as these local symbols would not be used anyway
+        // But they can be used in return values of functions/accessors if it is effectively a private declaration,
+        // e.g. public declaration inside a private class.
+
+        override fun visitField(declaration: IrField) {} // don't visit property backing field
+        override fun visitBlockBody(body: IrBlockBody) {} // don't visit function body and parameter default values
+        override fun visitExpressionBody(body: IrExpressionBody) {} // don't visit function body and parameter default values
+
         override fun getReferencedClassifier(symbol: IrClassifierSymbol): IrClassifierSymbol {
             val result = super.getReferencedClassifier(symbol)
             if (result !is IrTypeParameterSymbol)

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

@@ -53,10 +53,6 @@ open class DeepCopySymbolRemapper(
         element.acceptChildrenVoid(this)
     }
 
-    override fun visitCall(expression: IrCall) {
-        expression.acceptChildrenVoid(this)
-    }
-
     protected inline fun <D : DeclarationDescriptor, B : IrSymbolOwner, reified S : IrBindableSymbol<D, B>>
             remapSymbol(map: MutableMap<S, S>, owner: B, createNewSymbol: (S) -> S) {
         val symbol = owner.symbol as S
@@ -67,98 +63,98 @@ open class DeepCopySymbolRemapper(
         remapSymbol(classes, declaration) {
             IrClassSymbolImpl(descriptorsRemapper.remapDeclaredClass(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitClass(declaration)
     }
 
     override fun visitScript(declaration: IrScript) {
         remapSymbol(scripts, declaration) {
             IrScriptSymbolImpl(descriptorsRemapper.remapDeclaredScript(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitScript(declaration)
     }
 
     override fun visitConstructor(declaration: IrConstructor) {
         remapSymbol(constructors, declaration) {
             IrConstructorSymbolImpl(descriptorsRemapper.remapDeclaredConstructor(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitConstructor(declaration)
     }
 
     override fun visitEnumEntry(declaration: IrEnumEntry) {
         remapSymbol(enumEntries, declaration) {
             IrEnumEntrySymbolImpl(descriptorsRemapper.remapDeclaredEnumEntry(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitEnumEntry(declaration)
     }
 
     override fun visitExternalPackageFragment(declaration: IrExternalPackageFragment) {
         remapSymbol(externalPackageFragments, declaration) {
             IrExternalPackageFragmentSymbolImpl(descriptorsRemapper.remapDeclaredExternalPackageFragment(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitExternalPackageFragment(declaration)
     }
 
     override fun visitField(declaration: IrField) {
         remapSymbol(fields, declaration) {
             IrFieldSymbolImpl(descriptorsRemapper.remapDeclaredField(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitField(declaration)
     }
 
     override fun visitFile(declaration: IrFile) {
         remapSymbol(files, declaration) {
             IrFileSymbolImpl(descriptorsRemapper.remapDeclaredFilePackageFragment(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitFile(declaration)
     }
 
     override fun visitSimpleFunction(declaration: IrSimpleFunction) {
         remapSymbol(functions, declaration) {
             IrSimpleFunctionSymbolImpl(descriptorsRemapper.remapDeclaredSimpleFunction(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitSimpleFunction(declaration)
     }
 
     override fun visitProperty(declaration: IrProperty) {
         remapSymbol(properties, declaration) {
             IrPropertySymbolImpl(descriptorsRemapper.remapDeclaredProperty(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitProperty(declaration)
     }
 
     override fun visitTypeParameter(declaration: IrTypeParameter) {
         remapSymbol(typeParameters, declaration) {
             IrTypeParameterSymbolImpl(descriptorsRemapper.remapDeclaredTypeParameter(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitTypeParameter(declaration)
     }
 
     override fun visitValueParameter(declaration: IrValueParameter) {
         remapSymbol(valueParameters, declaration) {
             IrValueParameterSymbolImpl(descriptorsRemapper.remapDeclaredValueParameter(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitValueParameter(declaration)
     }
 
     override fun visitVariable(declaration: IrVariable) {
         remapSymbol(variables, declaration) {
             IrVariableSymbolImpl(descriptorsRemapper.remapDeclaredVariable(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitVariable(declaration)
     }
 
     override fun visitLocalDelegatedProperty(declaration: IrLocalDelegatedProperty) {
         remapSymbol(localDelegatedProperties, declaration) {
             IrLocalDelegatedPropertySymbolImpl(descriptorsRemapper.remapDeclaredLocalDelegatedProperty(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitLocalDelegatedProperty(declaration)
     }
 
     override fun visitTypeAlias(declaration: IrTypeAlias) {
         remapSymbol(typeAliases, declaration) {
             IrTypeAliasSymbolImpl(descriptorsRemapper.remapDeclaredTypeAlias(it.descriptor))
         }
-        declaration.acceptChildrenVoid(this)
+        super.visitTypeAlias(declaration)
     }
 
     override fun visitBlock(expression: IrBlock) {
@@ -167,7 +163,7 @@ open class DeepCopySymbolRemapper(
                 IrReturnableBlockSymbolImpl()
             }
         }
-        expression.acceptChildrenVoid(this)
+        super.visitBlock(expression)
     }
 
     private fun <T : IrSymbol> Map<T, T>.getDeclared(symbol: T) =