IR: pass also unsubstituted member to external conditions

In the future version of JavaIncompatibilityRulesOverridabilityCondition
for IR, we need to compute the original JVM signature of a declaration.
In descriptors, it's possible simply by using `original`.

compiler/ir/ir.actualization/src/main/kotlin/org/jetbrains/kotlin/backend/common/actualizer/ActualFakeOverridesAdder.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.descriptors.DescriptorVisibilities
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.overrides.IrOverrideChecker
+import org.jetbrains.kotlin.ir.overrides.MemberWithOriginal
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrPropertySymbol
 import org.jetbrains.kotlin.ir.symbols.IrSymbol
@@ -91,8 +92,8 @@ internal class ActualFakeOverridesAdder(
                 val override = klass.declarations.firstOrNull {
                     it is IrOverridableMember &&
                             overrideChecker.isOverridableBy(
-                                superMember = memberFromSupertype,
-                                subMember = it,
+                                superMember = MemberWithOriginal(memberFromSupertype),
+                                subMember = MemberWithOriginal(it),
                                 checkIsInlineFlag = false,
                             ).result == OverridingUtil.OverrideCompatibilityInfo.Result.OVERRIDABLE
                 } as? IrOverridableDeclaration<IrSymbol>

compiler/ir/ir.objcinterop/src/org/jetbrains/kotlin/ir/objcinterop/IrObjCOverridablilityCondidtion.kt

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.ir.declarations.IrFunction
 import org.jetbrains.kotlin.ir.declarations.IrOverridableMember
 import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.overrides.IrExternalOverridabilityCondition
+import org.jetbrains.kotlin.ir.overrides.MemberWithOriginal
 
 /**
  * Describes method overriding rules for Objective-C methods.
@@ -25,8 +26,14 @@ object IrObjCOverridabilityCondition : IrExternalOverridabilityCondition {
     override val contract = IrExternalOverridabilityCondition.Contract.BOTH
 
     override fun isOverridable(
+        superMember: MemberWithOriginal,
+        subMember: MemberWithOriginal,
+    ): IrExternalOverridabilityCondition.Result =
+        isOverridableImpl(superMember.member, subMember.member)
+
+    private fun isOverridableImpl(
         superMember: IrOverridableMember,
-        subMember: IrOverridableMember
+        subMember: IrOverridableMember,
     ): IrExternalOverridabilityCondition.Result {
         if (superMember.name == subMember.name) { // Slow path:
             if (superMember is IrFunction && subMember is IrFunction) {
@@ -74,4 +81,4 @@ object IrObjCOverridabilityCondition : IrExternalOverridabilityCondition {
 
         return true
     }
-}
+}

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

@@ -5,8 +5,6 @@
 
 package org.jetbrains.kotlin.ir.overrides
 
-import org.jetbrains.kotlin.ir.declarations.IrOverridableMember
-
 interface IrExternalOverridabilityCondition {
     enum class Result {
         OVERRIDABLE,
@@ -31,8 +29,8 @@ interface IrExternalOverridabilityCondition {
      *     will be based on the general override checking algorithm and the other external overridability conditions.
      */
     fun isOverridable(
-        superMember: IrOverridableMember,
-        subMember: IrOverridableMember,
+        superMember: MemberWithOriginal,
+        subMember: MemberWithOriginal,
     ): Result
 
     /**

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

@@ -36,7 +36,7 @@ class IrFakeOverrideBuilder(
 ) {
     private val overrideChecker = IrOverrideChecker(typeSystem, externalOverridabilityConditions)
 
-    private data class FakeOverride(val override: IrOverridableMember, val original: IrOverridableMember)
+    internal data class FakeOverride(val override: IrOverridableMember, val original: IrOverridableMember)
 
     private var IrOverridableMember.overriddenSymbols: List<IrSymbol>
         get() = when (this) {
@@ -153,7 +153,12 @@ class IrFakeOverrideBuilder(
 
         for (fromSupertype in membersFromSuper) {
             // Note: We do allow overriding multiple FOs at once one of which is `isInline=true`.
-            when (overrideChecker.isOverridableBy(fromSupertype.override, fromCurrent, checkIsInlineFlag = true).result) {
+            val overridability = overrideChecker.isOverridableBy(
+                MemberWithOriginal(fromSupertype),
+                MemberWithOriginal(fromCurrent),
+                checkIsInlineFlag = true,
+            )
+            when (overridability.result) {
                 OverrideCompatibilityInfo.Result.OVERRIDABLE -> {
                     overridden += fromSupertype
                     bound += fromSupertype
@@ -465,7 +470,7 @@ class IrFakeOverrideBuilder(
                 iterator.remove()
                 continue
             }
-            val finalResult = overrideChecker.getBothWaysOverridability(overrider.override, candidate.override)
+            val finalResult = overrideChecker.getBothWaysOverridability(MemberWithOriginal(overrider), MemberWithOriginal(candidate))
             if (finalResult == OverrideCompatibilityInfo.Result.OVERRIDABLE) {
                 overridable.add(candidate)
                 iterator.remove()

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

@@ -17,35 +17,36 @@ import org.jetbrains.kotlin.resolve.OverridingUtil.OverrideCompatibilityInfo.*
 import org.jetbrains.kotlin.types.AbstractTypeChecker
 import org.jetbrains.kotlin.types.TypeCheckerState
 
+/**
+ * @param member declaration that should be checked for overridability.
+ * @param original the original, unsubstituted version of the declaration if the declaration is a fake override.
+ */
+class MemberWithOriginal(val member: IrOverridableMember, original: IrOverridableMember? = null) {
+    internal constructor(fakeOverride: IrFakeOverrideBuilder.FakeOverride) : this(fakeOverride.override, fakeOverride.original)
+
+    val original: IrOverridableMember = original ?: member
+}
+
 class IrOverrideChecker(
     private val typeSystem: IrTypeSystemContext,
     private val externalOverridabilityConditions: List<IrExternalOverridabilityCondition>,
 ) {
     fun getBothWaysOverridability(
-        overriderDescriptor: IrOverridableMember,
-        candidateDescriptor: IrOverridableMember,
+        overrider: MemberWithOriginal,
+        candidate: MemberWithOriginal,
     ): Result {
-        val result1 = isOverridableBy(
-            candidateDescriptor,
-            overriderDescriptor,
-            checkIsInlineFlag = false,
-        ).result
-
-        val result2 = isOverridableBy(
-            overriderDescriptor,
-            candidateDescriptor,
-            checkIsInlineFlag = false,
-        ).result
+        val result1 = isOverridableBy(candidate, overrider, checkIsInlineFlag = false).result
+        val result2 = isOverridableBy(overrider, candidate, checkIsInlineFlag = false).result
 
         return if (result1 == result2) result1 else Result.INCOMPATIBLE
     }
 
     fun isOverridableBy(
-        superMember: IrOverridableMember,
-        subMember: IrOverridableMember,
+        superMember: MemberWithOriginal,
+        subMember: MemberWithOriginal,
         checkIsInlineFlag: Boolean,
     ): OverrideCompatibilityInfo {
-        val basicResult = isOverridableByWithoutExternalConditions(superMember, subMember, checkIsInlineFlag)
+        val basicResult = isOverridableByWithoutExternalConditions(superMember.member, subMember.member, checkIsInlineFlag)
 
         return runExternalOverridabilityConditions(superMember, subMember, basicResult)
     }
@@ -146,8 +147,8 @@ class IrOverrideChecker(
 
 
     private fun runExternalOverridabilityConditions(
-        superMember: IrOverridableMember,
-        subMember: IrOverridableMember,
+        superMember: MemberWithOriginal,
+        subMember: MemberWithOriginal,
         basicResult: OverrideCompatibilityInfo,
     ): OverrideCompatibilityInfo {
         var wasSuccess = basicResult.result == OverrideCompatibilityInfo.Result.OVERRIDABLE