IR: introduce IrFakeOverrideFunction, IrFakeOverrideProperty

Use them instead of the implementations. This will allow to refactor
creation to a factory and allow to use other implementations in the
future.

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/overrides/FakeOverrides.kt

@@ -18,11 +18,7 @@ package org.jetbrains.kotlin.backend.common.overrides
 
 import org.jetbrains.kotlin.backend.common.serialization.signature.IdSignatureSerializer
 import org.jetbrains.kotlin.ir.IrElement
-import org.jetbrains.kotlin.ir.declarations.IrClass
-import org.jetbrains.kotlin.ir.declarations.IrFunction
-import org.jetbrains.kotlin.ir.declarations.IrModuleFragment
-import org.jetbrains.kotlin.ir.declarations.IrOverridableMember
-import org.jetbrains.kotlin.ir.declarations.impl.IrFakeOverrideFunctionImpl
+import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFakeOverridePropertyImpl
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.descriptors.WrappedPropertyDescriptor
@@ -118,13 +114,13 @@ class FakeOverrideBuilder(
 
     override fun linkFakeOverride(fakeOverride: IrOverridableMember) {
         when (fakeOverride) {
-            is IrFakeOverrideFunctionImpl -> linkFunctionFakeOverride(fakeOverride)
-            is IrFakeOverridePropertyImpl -> linkPropertyFakeOverride(fakeOverride)
+            is IrFakeOverrideFunction -> linkFunctionFakeOverride(fakeOverride)
+            is IrFakeOverrideProperty -> linkPropertyFakeOverride(fakeOverride)
             else -> error("Unexpected fake override: $fakeOverride")
         }
     }
 
-    private fun linkFunctionFakeOverride(declaration: IrFakeOverrideFunctionImpl) {
+    private fun linkFunctionFakeOverride(declaration: IrFakeOverrideFunction) {
         val signature = signaturer.composePublicIdSignature(declaration)
 
         symbolTable.declareSimpleFunctionFromLinker(WrappedSimpleFunctionDescriptor(), signature) {
@@ -133,7 +129,7 @@ class FakeOverrideBuilder(
         }
     }
 
-    private fun linkPropertyFakeOverride(declaration: IrFakeOverridePropertyImpl) {
+    private fun linkPropertyFakeOverride(declaration: IrFakeOverrideProperty) {
         // To compute a signature for a property with type parameters,
         // we must have its accessor's correspondingProperty pointing to the property's symbol.
         // See IrMangleComputer.mangleTypeParameterReference() for details.
@@ -159,15 +155,11 @@ class FakeOverrideBuilder(
 
         declaration.getter?.let {
             it.correspondingPropertySymbol = declaration.symbol
-            linkFunctionFakeOverride(it as? IrFakeOverrideFunctionImpl
-                ?: error("Unexpected fake override getter: $it")
-            )
+            linkFunctionFakeOverride(it as? IrFakeOverrideFunction ?: error("Unexpected fake override getter: $it"))
         }
         declaration.setter?.let {
             it.correspondingPropertySymbol = declaration.symbol
-            linkFunctionFakeOverride(it as? IrFakeOverrideFunctionImpl
-                ?: error("Unexpected fake override setter: $it")
-            )
+            linkFunctionFakeOverride(it as? IrFakeOverrideFunction ?: error("Unexpected fake override setter: $it"))
         }
     }
 

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/overrides/IrOverridingUtil.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.ir.declarations.*
-import org.jetbrains.kotlin.ir.declarations.impl.IrFakeOverrideFunctionImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrFakeOverridePropertyImpl
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.symbols.IrPropertySymbol
@@ -280,7 +279,7 @@ class IrOverridingUtil(
     }
 
     private fun IrSimpleFunction.updateAccessorModalityAndVisibility(newModality: Modality, newVisibility: Visibility): IrSimpleFunction? {
-        require(this is IrFakeOverrideFunctionImpl) {
+        require(this is IrFakeOverrideFunction) {
             "Unexpected fake override accessor kind: $this"
         }
         // For descriptors it gets INVISIBLE_FAKE.
@@ -307,13 +306,13 @@ class IrOverridingUtil(
 
         val fakeOverride = mostSpecific.apply {
             when (this) {
-                is IrFakeOverridePropertyImpl -> {
+                is IrFakeOverrideProperty -> {
                     this.visibility = visibility
                     this.modality = modality
                     this.getter = this.getter?.updateAccessorModalityAndVisibility(modality, visibility)
                     this.setter = this.setter?.updateAccessorModalityAndVisibility(modality, visibility)
                 }
-                is IrFakeOverrideFunctionImpl -> {
+                is IrFakeOverrideFunction -> {
                     this.visibility = visibility
                     this.modality = modality
                 }