Avoid object's interpretation with nullable type

#KT-56215 Fixed

compiler/ir/ir.interpreter/src/org/jetbrains/kotlin/ir/interpreter/InstructionsUnfolder.kt

@@ -256,11 +256,11 @@ private fun unfoldSetField(expression: IrSetField, callStack: CallStack) {
 }
 
 private fun unfoldGetValue(expression: IrGetValue, environment: IrInterpreterEnvironment) {
-    if (expression.isAccessToObject()) {
+    if (expression.isAccessToNotNullableObject()) {
         // used to evaluate constants inside object
         // TODO is this correct behaviour?
         val irGetObject = expression.type.classOrNull?.owner!!.createGetObject()
-        return unfoldGetObjectValue(irGetObject, environment)
+        return unfoldGetObjectValue(irGetObject, environment) // if object already exists, it will be taken from `mapOfObjects`
     }
     environment.callStack.pushState(environment.callStack.loadState(expression.symbol))
 }

compiler/ir/ir.interpreter/src/org/jetbrains/kotlin/ir/interpreter/Utils.kt

@@ -294,10 +294,10 @@ internal fun IrClass.getSingleAbstractMethod(): IrFunction {
     return declarations.filterIsInstance<IrSimpleFunction>().single { it.modality == Modality.ABSTRACT }
 }
 
-internal fun IrGetValue.isAccessToObject(): Boolean {
+internal fun IrGetValue.isAccessToNotNullableObject(): Boolean {
     val owner = this.symbol.owner
     val expectedClass = this.type.classOrNull?.owner
-    if (expectedClass == null || !expectedClass.isObject) return false
+    if (expectedClass == null || !expectedClass.isObject || this.type.isNullable()) return false
     return owner.origin == IrDeclarationOrigin.INSTANCE_RECEIVER || owner.name.asString() == "<this>"
 }
 

compiler/ir/ir.interpreter/src/org/jetbrains/kotlin/ir/interpreter/checker/IrCompileTimeChecker.kt

@@ -11,7 +11,7 @@ import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.interpreter.accessesTopLevelOrObjectField
 import org.jetbrains.kotlin.ir.interpreter.fqName
-import org.jetbrains.kotlin.ir.interpreter.isAccessToObject
+import org.jetbrains.kotlin.ir.interpreter.isAccessToNotNullableObject
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.constructors
 import org.jetbrains.kotlin.ir.util.statements
@@ -160,7 +160,7 @@ class IrCompileTimeChecker(
     }
 
     override fun visitGetValue(expression: IrGetValue, data: Nothing?): Boolean {
-        return visitedStack.contains(expression.symbol.owner.parent) || expression.isAccessToObject()
+        return visitedStack.contains(expression.symbol.owner.parent) || expression.isAccessToNotNullableObject()
     }
 
     override fun visitSetValue(expression: IrSetValue, data: Nothing?): Boolean {