Raw FIR: set val setter to null instead of default one

compiler/fir/dump/src/org/jetbrains/kotlin/fir/dump/HtmlFirDump.kt

@@ -849,7 +849,7 @@ class HtmlFirDump internal constructor(private var linkResolver: FirLinkResolver
 
         withIdentLevel {
             generate(property.getter)
-            generate(property.setter)
+            property.setter?.let { generate(it) }
         }
     }
 

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt

@@ -497,7 +497,7 @@ internal class Fir2IrVisitor(
         }
         getter = property.getter.accept(this@Fir2IrVisitor, type) as IrSimpleFunction
         if (property.isVar) {
-            setter = property.setter.accept(this@Fir2IrVisitor, type) as IrSimpleFunction
+            setter = property.setter!!.accept(this@Fir2IrVisitor, type) as IrSimpleFunction
         }
         property.annotations.forEach {
             annotations += it.accept(this@Fir2IrVisitor, null) as IrConstructorCall

compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -281,7 +281,7 @@ class RawFirBuilder(val session: FirSession, val stubMode: Boolean) {
                     )
                 },
                 getter = FirDefaultPropertyGetter(session, this, type, visibility),
-                setter = FirDefaultPropertySetter(session, this, type, visibility),
+                setter = if (isMutable) FirDefaultPropertySetter(session, this, type, visibility) else null,
                 delegate = null
             )
             extractAnnotationsTo(firProperty)
@@ -796,7 +796,7 @@ class RawFirBuilder(val session: FirSession, val stubMode: Boolean) {
                     isVar,
                     initializer,
                     property.getter.toFirPropertyAccessor(property, propertyType, isGetter = true),
-                    property.setter.toFirPropertyAccessor(property, propertyType, isGetter = false),
+                    if (isVar) property.setter.toFirPropertyAccessor(property, propertyType, isGetter = false) else null,
                     if (property.hasDelegate()) {
                         { property.delegate?.expression }.toFirExpression("Should have delegate")
                     } else null

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/deserialization/FirMemberDeserializer.kt

@@ -159,6 +159,7 @@ class FirMemberDeserializer(private val c: FirDeserializationContext) {
 
         val getterFlags = if (proto.hasGetterFlags()) proto.getterFlags else flags
         val setterFlags = if (proto.hasSetterFlags()) proto.setterFlags else flags
+        val isVar = Flags.IS_VAR.get(flags)
 
         return FirMemberPropertyImpl(
             c.session,
@@ -174,10 +175,12 @@ class FirMemberDeserializer(private val c: FirDeserializationContext) {
             isLateInit = Flags.IS_LATEINIT.get(flags),
             receiverTypeRef = proto.receiverType(c.typeTable)?.toTypeRef(local),
             returnTypeRef = returnTypeRef,
-            isVar = Flags.IS_VAR.get(flags),
+            isVar = isVar,
             initializer = null,
             getter = FirDefaultPropertyGetter(c.session, null, returnTypeRef, ProtoEnumFlags.visibility(Flags.VISIBILITY.get(getterFlags))),
-            setter = FirDefaultPropertySetter(c.session, null, returnTypeRef, ProtoEnumFlags.visibility(Flags.VISIBILITY.get(setterFlags))),
+            setter = if (isVar) {
+                FirDefaultPropertySetter(c.session, null, returnTypeRef, ProtoEnumFlags.visibility(Flags.VISIBILITY.get(setterFlags)))
+            } else null,
             delegate = null
         ).apply {
             typeParameters += local.typeDeserializer.ownTypeParameters.map { it.firUnsafe() }

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirStatusResolveTransformer.kt

@@ -43,7 +43,7 @@ class FirStatusResolveTransformer : FirAbstractTreeTransformer() {
                                 Modality.FINAL
                             this is FirNamedFunction && body == null ->
                                 Modality.ABSTRACT
-                            this is FirProperty && initializer == null && getter.body == null && setter.body == null ->
+                            this is FirProperty && initializer == null && getter.body == null && setter?.body == null ->
                                 Modality.ABSTRACT
                             else ->
                                 Modality.OPEN

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -350,8 +350,8 @@ class FirRenderer(builder: StringBuilder) : FirVisitorVoid() {
             println()
         }
         if (property.isVar) {
-            property.setter.accept(this)
-            if (property.setter.body == null) {
+            property.setter?.accept(this)
+            if (property.setter?.body == null) {
                 println()
             }
         }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/FirProperty.kt

@@ -22,7 +22,7 @@ interface FirProperty : @VisitedSupertype FirDeclaration, FirCallableMemberDecla
     // Should it be nullable or have some default?
     val getter: FirPropertyAccessor
 
-    val setter: FirPropertyAccessor
+    val setter: FirPropertyAccessor?
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R =
         visitor.visitProperty(this, data)
@@ -32,6 +32,6 @@ interface FirProperty : @VisitedSupertype FirDeclaration, FirCallableMemberDecla
         initializer?.accept(visitor, data)
         delegate?.accept(visitor, data)
         getter.accept(visitor, data)
-        setter.accept(visitor, data)
+        setter?.accept(visitor, data)
     }
 }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/impl/FirMemberPropertyImpl.kt

@@ -36,7 +36,7 @@ class FirMemberPropertyImpl(
     override val isVar: Boolean,
     override var initializer: FirExpression?,
     override var getter: FirPropertyAccessor,
-    override var setter: FirPropertyAccessor,
+    override var setter: FirPropertyAccessor?,
     override var delegate: FirExpression?
 ) : FirAbstractCallableMember(
     session, psi, name, visibility, modality, isExpect, isActual, isOverride, receiverTypeRef, returnTypeRef
@@ -49,7 +49,7 @@ class FirMemberPropertyImpl(
 
     override fun <D> transformChildren(transformer: FirTransformer<D>, data: D): FirElement {
         getter = getter.transformSingle(transformer, data)
-        setter = setter.transformSingle(transformer, data)
+        setter = setter?.transformSingle(transformer, data)
         initializer = initializer?.transformSingle(transformer, data)
         delegate = delegate?.transformSingle(transformer, data)