Rework nullability in IR

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/export/ExportModelGenerator.kt

@@ -469,7 +469,7 @@ class ExportModelGenerator(
             return ExportedType.ErrorType("NonSimpleType ${type.render()}")
 
         val classifier = type.classifier
-        val isNullable = type.hasQuestionMark
+        val isMarkedNullable = type.isMarkedNullable()
         val nonNullType = type.makeNotNull() as IrSimpleType
 
         val exportedType = when {
@@ -528,7 +528,7 @@ class ExportModelGenerator(
             else -> error("Unexpected classifier $classifier")
         }
 
-        return exportedType.withNullability(isNullable)
+        return exportedType.withNullability(isMarkedNullable)
     }
 
     private fun IrClass.getExportableName(): String {

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ScriptRemoveReceiverLowering.kt

@@ -74,7 +74,7 @@ class ScriptRemoveReceiverLowering(val context: CommonBackendContext) : FileLowe
                             endOffset,
                             IrSimpleTypeImpl(
                                 context.ir.symbols.functionN(newN),
-                                (type as IrSimpleType).hasQuestionMark,
+                                (type as IrSimpleType).nullability,
                                 arguments,
                                 type.annotations
                             ),
@@ -111,7 +111,7 @@ class ScriptRemoveReceiverLowering(val context: CommonBackendContext) : FileLowe
                             endOffset,
                             IrSimpleTypeImpl(
                                 (if (setter == null) getPropertyN(newN) else getMutablePropertyN(newN)),
-                                (type as IrSimpleType).hasQuestionMark,
+                                (type as IrSimpleType).nullability,
                                 arguments,
                                 type.annotations
                             ),

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/IrTypeUtils.kt

@@ -13,7 +13,6 @@ import org.jetbrains.kotlin.ir.symbols.IrScriptSymbol
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.fqNameWhenAvailable
-import org.jetbrains.kotlin.ir.util.getInlineClassUnderlyingType
 import org.jetbrains.kotlin.ir.util.isEffectivelyExternal
 import org.jetbrains.kotlin.js.backend.ast.JsNameRef
 import org.jetbrains.kotlin.types.Variance
@@ -26,7 +25,11 @@ fun IrType.asString(): String = when (this) {
     is IrDynamicType -> "dynamic"
     is IrSimpleType ->
         classifier.asString() +
-                (if (hasQuestionMark) "?" else "") +
+                when (nullability) {
+                    SimpleTypeNullability.MARKED_NULLABLE -> "?"
+                    SimpleTypeNullability.NOT_SPECIFIED -> ""
+                    SimpleTypeNullability.DEFINITELY_NOT_NULL -> if (classifier is IrTypeParameterSymbol) " & Any" else ""
+                } +
                 (arguments.ifNotEmpty {
                     joinToString(separator = ",", prefix = "<", postfix = ">") { it.asString() }
                 } ?: "")

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/utils/TypeTranformer.kt

@@ -34,11 +34,8 @@ private val IrTypeParameter.erasedUpperBound: IrClass?
 
 val IrType.erasedUpperBound: IrClass?
     get() =
-        if (this is IrDefinitelyNotNullType)
-            this.original.erasedUpperBound
-        else
-            when (val classifier = classifierOrNull) {
-                is IrClassSymbol -> classifier.owner
-                is IrTypeParameterSymbol -> classifier.owner.erasedUpperBound
-                else -> throw IllegalStateException()
-            }
+        when (val classifier = classifierOrNull) {
+            is IrClassSymbol -> classifier.owner
+            is IrTypeParameterSymbol -> classifier.owner.erasedUpperBound
+            else -> throw IllegalStateException()
+        }