[Inference] Add ability to approximate local types in AbstractTypeApproximator

compiler/resolution.common/src/org/jetbrains/kotlin/types/AbstractTypeApproximator.kt

@@ -162,6 +162,20 @@ abstract class AbstractTypeApproximator(val ctx: TypeSystemInferenceExtensionCon
         }
     }
 
+    private fun approximateLocalTypes(type: SimpleTypeMarker, conf: TypeApproximatorConfiguration, toSuper: Boolean): SimpleTypeMarker? {
+        if (!toSuper) return null
+        if (!conf.localTypes) return null
+        val constructor = type.typeConstructor()
+        val needApproximate = conf.localTypes && constructor.isLocalType()
+        if (!needApproximate) return null
+        val superConstructor = constructor.supertypes().first().typeConstructor()
+        val typeCheckerContext = newBaseTypeCheckerContext(
+            errorTypesEqualToAnything = false,
+            stubTypesEqualToAnything = false
+        )
+        return AbstractTypeChecker.findCorrespondingSupertypes(typeCheckerContext, type, superConstructor).first()
+    }
+
     private fun isIntersectionTypeEffectivelyNothing(constructor: IntersectionTypeConstructorMarker): Boolean {
         // We consider intersection as Nothing only if one of it's component is a primitive number type
         // It's intentional we're not trying to prove population of some type as it was in OI
@@ -326,7 +340,7 @@ abstract class AbstractTypeApproximator(val ctx: TypeSystemInferenceExtensionCon
                 null
         }
 
-        return null // simple classifier type
+        return approximateLocalTypes(type, conf, toSuper) // simple classifier type
     }
 
     private fun approximateDefinitelyNotNullType(
@@ -518,10 +532,11 @@ abstract class AbstractTypeApproximator(val ctx: TypeSystemInferenceExtensionCon
             }
         }
 
-        if (newArguments.all { it == null }) return null
+        if (newArguments.all { it == null }) return approximateLocalTypes(type, conf, toSuper)
 
         val newArgumentsList = List(type.argumentsCount()) { index -> newArguments[index] ?: type.getArgument(index) }
-        return type.replaceArguments(newArgumentsList)
+        val approximatedType = type.replaceArguments(newArgumentsList)
+        return approximateLocalTypes(approximatedType, conf, toSuper) ?: approximatedType
     }
 
     private fun KotlinTypeMarker.defaultResult(toSuper: Boolean) = if (toSuper) nullableAnyType() else {

compiler/resolution.common/src/org/jetbrains/kotlin/types/TypeApproximatorConfiguration.kt

@@ -22,6 +22,7 @@ open class TypeApproximatorConfiguration {
     open val definitelyNotNullType: Boolean get() = true
     open val intersection: IntersectionStrategy = IntersectionStrategy.TO_COMMON_SUPERTYPE
     open val intersectionTypesInContravariantPositions = false
+    open val localTypes = false
 
     open val typeVariable: (TypeVariableTypeConstructorMarker) -> Boolean = { false }
     open fun capturedType(ctx: TypeSystemInferenceExtensionContext, type: CapturedTypeMarker): Boolean =