From 595cab2aaf163cc37d932d15e00735d31d9e3f3d Mon Sep 17 00:00:00 2001
From: "sebastian.sellmair" <sebastian.sellmair@jetbrains.com>
Date: Fri, 10 Sep 2021 11:00:24 +0200
Subject: [PATCH] [Commonizer] ClassOrTypeAliasTypeCommonizer: Implement proper
 type argument substitution

^KT-47574 Verification Pending
---
 .../kotlin/commonizer/cir/CirType.kt          | 14 ++++---
 .../core/ClassOrTypeAliasTypeCommonizer.kt    | 38 ++++++++++++++-----
 .../HierarchicalTypeAliasCommonizationTest.kt |  2 +-
 3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/CirType.kt b/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/CirType.kt
index 447f76100a7..22ee412b768 100644
--- a/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/CirType.kt
+++ b/native/commonizer/src/org/jetbrains/kotlin/commonizer/cir/CirType.kt
@@ -100,6 +100,7 @@ abstract class CirClassType : CirClassOrTypeAliasType(), CirHasVisibility {
     }
 
     override fun withArguments(arguments: List<CirTypeProjection>): CirClassOrTypeAliasType {
+        if (arguments == this.arguments) return this
         return createInterned(
             classId = classifierId,
             outerType = outerType,
@@ -162,12 +163,13 @@ abstract class CirTypeAliasType : CirClassOrTypeAliasType() {
     }
 
     override fun withArguments(arguments: List<CirTypeProjection>): CirClassOrTypeAliasType {
-        return createInterned(
-            typeAliasId = classifierId,
-            underlyingType = underlyingType,
-            arguments = arguments,
-            isMarkedNullable = isMarkedNullable
-        )
+        if (this.arguments == arguments) return this
+        return copyInterned(arguments = arguments)
+    }
+
+    fun withUnderlyingType(underlyingType: CirClassOrTypeAliasType): CirClassOrTypeAliasType {
+        if (this.underlyingType == underlyingType) return this
+        return copyInterned(underlyingType = underlyingType)
     }
 
     companion object {
diff --git a/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt b/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
index f6db63af985..cfa32781fe8 100644
--- a/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
+++ b/native/commonizer/src/org/jetbrains/kotlin/commonizer/core/ClassOrTypeAliasTypeCommonizer.kt
@@ -68,8 +68,8 @@ internal class ClassOrTypeAliasTypeCommonizer(
         val commonizedClassifier = classifiers.commonizedNodes.classNode(classifierId)?.commonDeclaration?.invoke()
             ?: classifiers.commonizedNodes.typeAliasNode(classifierId)?.commonDeclaration?.invoke()
 
-        when (commonizedClassifier) {
-            is CirClass -> return CirClassType.createInterned(
+        return when (commonizedClassifier) {
+            is CirClass -> CirClassType.createInterned(
                 classId = classifierId,
                 outerType = outerType,
                 arguments = arguments,
@@ -77,19 +77,15 @@ internal class ClassOrTypeAliasTypeCommonizer(
                 isMarkedNullable = isMarkedNullable
             )
 
-            is CirTypeAlias -> return CirTypeAliasType.createInterned(
+            is CirTypeAlias -> CirTypeAliasType.createInterned(
                 typeAliasId = classifierId,
                 arguments = arguments,
                 isMarkedNullable = isMarkedNullable,
-                underlyingType = computeSuitableUnderlyingType(
-                    classifiers, typeCommonizer, commonizedClassifier.underlyingType
-                )?.makeNullableIfNecessary(isMarkedNullable) ?: return null
+                underlyingType = commonizedClassifier.underlyingType.withParentArguments(arguments, isMarkedNullable)
             )
 
-            else -> Unit
+            else -> null
         }
-
-        return null
     }
 
     private fun selectClassifierId(types: List<CirClassOrTypeAliasType>): CirEntityId? {
@@ -105,6 +101,30 @@ internal class ClassOrTypeAliasTypeCommonizer(
     }
 }
 
+private fun CirClassOrTypeAliasType.withParentArguments(
+    parentArguments: List<CirTypeProjection>, parentIsMarkedNullable: Boolean
+): CirClassOrTypeAliasType {
+    val newIsMarkedNullable = isMarkedNullable || parentIsMarkedNullable
+
+    val newArguments = arguments.map { oldArgument ->
+        if (oldArgument is CirRegularTypeProjection) {
+            val oldArgumentType = oldArgument.type
+            if (oldArgumentType is CirTypeParameterType) {
+                return@map parentArguments[oldArgumentType.index]
+            }
+        }
+        oldArgument
+    }
+
+    return when (val newUnderlyingType = makeNullableIfNecessary(newIsMarkedNullable).withArguments(newArguments)) {
+        this -> this
+        is CirClassType -> newUnderlyingType
+        is CirTypeAliasType -> newUnderlyingType.withUnderlyingType(
+            newUnderlyingType.underlyingType.withParentArguments(newArguments, newIsMarkedNullable)
+        )
+    }
+}
+
 internal tailrec fun CirClassOrTypeAliasType.expandedType(): CirClassType = when (this) {
     is CirClassType -> this
     is CirTypeAliasType -> this.underlyingType.expandedType()
diff --git a/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/HierarchicalTypeAliasCommonizationTest.kt b/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/HierarchicalTypeAliasCommonizationTest.kt
index ab1e6efb971..a33c917543f 100644
--- a/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/HierarchicalTypeAliasCommonizationTest.kt
+++ b/native/commonizer/tests/org/jetbrains/kotlin/commonizer/hierarchical/HierarchicalTypeAliasCommonizationTest.kt
@@ -130,7 +130,7 @@ class HierarchicalTypeAliasCommonizationTest : AbstractInlineSourcesCommonizatio
         )
     }
 
-    fun `KT-47574 - test long typealias chain`() {
+    fun `test long typealias chain`() {
         val result = commonize {
             outputTarget("(a, b)")