Use TypeSystemCommonBackendContext in computeExpandedTypeForInlineClass

core/descriptors/src/org/jetbrains/kotlin/types/TypeSystemCommonBackendContext.kt

@@ -6,9 +6,7 @@
 package org.jetbrains.kotlin.types
 
 import org.jetbrains.kotlin.name.FqName
-import org.jetbrains.kotlin.types.model.KotlinTypeMarker
-import org.jetbrains.kotlin.types.model.TypeConstructorMarker
-import org.jetbrains.kotlin.types.model.TypeSystemContext
+import org.jetbrains.kotlin.types.model.*
 
 interface TypeSystemCommonBackendContext : TypeSystemContext {
     fun TypeConstructorMarker.isFinalClassOrEnumEntryOrAnnotationClassConstructor(): Boolean
@@ -24,4 +22,15 @@ interface TypeSystemCommonBackendContext : TypeSystemContext {
      * TODO: provide a more granular & elaborate API here to reduce confusion
      */
     fun KotlinTypeMarker.getAnnotationFirstArgumentValue(fqName: FqName): Any?
+
+    fun TypeConstructorMarker.getTypeParameterClassifier(): TypeParameterMarker?
+    fun TypeConstructorMarker.isInlineClass(): Boolean
+    fun TypeParameterMarker.getRepresentativeUpperBound(): KotlinTypeMarker
+    fun KotlinTypeMarker.getSubstitutedUnderlyingType(): KotlinTypeMarker?
+
+    fun KotlinTypeMarker.isMarkedNullable(): Boolean =
+        this is SimpleTypeMarker && isMarkedNullable()
+
+    fun KotlinTypeMarker.makeNullable(): KotlinTypeMarker =
+        asSimpleType()?.withNullability(true) ?: this
 }

core/descriptors/src/org/jetbrains/kotlin/types/checker/ClassicTypeSystemContext.kt

@@ -16,10 +16,12 @@ import org.jetbrains.kotlin.resolve.constants.IntegerLiteralTypeConstructor
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasExactAnnotation
 import org.jetbrains.kotlin.resolve.descriptorUtil.hasNoInferAnnotation
 import org.jetbrains.kotlin.resolve.descriptorUtil.isExactAnnotation
+import org.jetbrains.kotlin.resolve.substitutedUnderlyingType
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.model.*
 import org.jetbrains.kotlin.types.typeUtil.asTypeProjection
 import org.jetbrains.kotlin.types.typeUtil.contains
+import org.jetbrains.kotlin.types.typeUtil.representativeUpperBound
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
 
@@ -495,6 +497,26 @@ interface ClassicTypeSystemContext : TypeSystemInferenceExtensionContext, TypeSy
         require(this is KotlinType, this::errorMessage)
         return annotations.findAnnotation(fqName)?.allValueArguments?.values?.firstOrNull()?.value
     }
+
+    override fun TypeConstructorMarker.getTypeParameterClassifier(): TypeParameterMarker? {
+        require(this is TypeConstructor, this::errorMessage)
+        return declarationDescriptor as? TypeParameterDescriptor
+    }
+
+    override fun TypeConstructorMarker.isInlineClass(): Boolean {
+        require(this is TypeConstructor, this::errorMessage)
+        return (declarationDescriptor as? ClassDescriptor)?.isInline == true
+    }
+
+    override fun TypeParameterMarker.getRepresentativeUpperBound(): KotlinTypeMarker {
+        require(this is TypeParameterDescriptor, this::errorMessage)
+        return representativeUpperBound
+    }
+
+    override fun KotlinTypeMarker.getSubstitutedUnderlyingType(): KotlinTypeMarker? {
+        require(this is KotlinType, this::errorMessage)
+        return substitutedUnderlyingType()
+    }
 }
 
 fun TypeVariance.convertVariance(): Variance {