FIR: record use of backing field symbol to indeed add a backing field

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrDeclarationStorage.kt

@@ -676,8 +676,10 @@ class Fir2IrDeclarationStorage(
                     val setter = property.setter
                     // TODO: this checks are very preliminary, FIR resolve should determine backing field presence itself
                     if (property.isConst || (property.modality != Modality.ABSTRACT && (irParent !is IrClass || !irParent.isInterface))) {
-                        if (initializer != null || getter is FirDefaultPropertyGetter ||
+                        if (initializer != null ||
-                            property.isVar && setter is FirDefaultPropertySetter
+                            getter is FirDefaultPropertyGetter ||
+                            property.isVar && setter is FirDefaultPropertySetter ||
+                            property.backingFieldSymbol.isReferenced
                         ) {
                             backingField = createBackingField(
                                 property, IrDeclarationOrigin.PROPERTY_BACKING_FIELD, descriptor,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt

@@ -515,6 +515,7 @@ class FirCallResolver(
                 val candidate = candidates.single()
                 val coneSymbol = candidate.symbol
                 if (coneSymbol is FirBackingFieldSymbol) {
+                    coneSymbol.isReferenced = true
                     return buildBackingFieldReference {
                         this.source = source
                         resolvedSymbol = coneSymbol

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirVariableSymbol.kt

@@ -32,7 +32,10 @@ open class FirPropertySymbol(
     constructor(name: Name) : this(CallableId(name))
 }
 
-class FirBackingFieldSymbol(callableId: CallableId) : FirVariableSymbol<FirProperty>(callableId)
+class FirBackingFieldSymbol(
+    callableId: CallableId,
+    var isReferenced: Boolean = false
+) : FirVariableSymbol<FirProperty>(callableId)
 
 class FirDelegateFieldSymbol<D : FirVariable<D>>(callableId: CallableId) : FirVariableSymbol<D>(callableId) {
     val delegate: FirExpression

compiler/testData/codegen/box/operatorConventions/augmentedAssignmentInInitializer.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 abstract class A {
     val b = B("O")
 

compiler/testData/codegen/box/secondaryConstructors/withoutPrimarySimple.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 class A {
     val value: String
         get() = field + "K"