FIR: Implement fast path for classes subtyping

core/type-system/src/org/jetbrains/kotlin/types/AbstractTypeChecker.kt

@@ -17,7 +17,7 @@ import java.util.*
 abstract class AbstractTypeCheckerContext : TypeSystemContext {
 
 
-    abstract fun substitutionSupertypePolicy(type: SimpleTypeMarker): SupertypesPolicy.DoCustomTransform
+    abstract fun substitutionSupertypePolicy(type: SimpleTypeMarker): SupertypesPolicy
 
     abstract fun areEqualTypeConstructors(a: TypeConstructorMarker, b: TypeConstructorMarker): Boolean
 
@@ -379,6 +379,10 @@ object AbstractTypeChecker {
         baseType: SimpleTypeMarker,
         constructor: TypeConstructorMarker
     ): List<SimpleTypeMarker> {
+        baseType.fastCorrespondingSupertypes(constructor)?.let {
+            return it
+        }
+
         if (constructor.isCommonFinalClassConstructor()) {
             return if (areEqualTypeConstructors(baseType.typeConstructor(), constructor))
                 listOf(captureFromArguments(baseType, CaptureStatus.FOR_SUBTYPING) ?: baseType)

core/type-system/src/org/jetbrains/kotlin/types/model/TypeSystemContext.kt

@@ -219,6 +219,8 @@ interface TypeSystemContext : TypeSystemOptimizationContext {
 
     fun SimpleTypeMarker.isClassType(): Boolean = typeConstructor().isClassTypeConstructor()
 
+    fun SimpleTypeMarker.fastCorrespondingSupertypes(constructor: TypeConstructorMarker): List<SimpleTypeMarker>? = null
+
     fun SimpleTypeMarker.isIntegerLiteralType(): Boolean = typeConstructor().isIntegerLiteralTypeConstructor()
 
     fun SimpleTypeMarker.possibleIntegerTypes(): Collection<KotlinTypeMarker>
@@ -290,4 +292,4 @@ inline fun TypeArgumentListMarker.all(
         if (!predicate(get(index))) return false
     }
     return true
-}
+}