diff --git a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationArgumentVisitor.kt b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationArgumentVisitor.kt
index 4bf27093692..00d00ebad38 100644
--- a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationArgumentVisitor.kt
+++ b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationArgumentVisitor.kt
@@ -10,7 +10,7 @@ import org.jetbrains.kotlin.fir.types.arrayElementType
 import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.deserialization.Flags
 
-object FirAnnotationArgumentVisitor : AnnotationArgumentVisitor<Unit, FirAnnotationArgumentVisitorData>() {
+internal object FirAnnotationArgumentVisitor : AnnotationArgumentVisitor<Unit, FirAnnotationArgumentVisitorData>() {
     override fun visitAnnotationValue(value: AnnotationValue, data: FirAnnotationArgumentVisitorData) {
         data.builder.type = ProtoBuf.Annotation.Argument.Value.Type.ANNOTATION
         // TODO: annotation = serializeAnnotation(value.value)
diff --git a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationSerializer.kt b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationSerializer.kt
index a61d142ed50..bb590551a9d 100644
--- a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationSerializer.kt
+++ b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationSerializer.kt
@@ -29,7 +29,7 @@ class FirAnnotationSerializer(private val session: FirSession, internal val stri
         }
     }.build()
 
-    fun valueProto(constant: ConstantValue<*>): ProtoBuf.Annotation.Argument.Value.Builder =
+    internal fun valueProto(constant: ConstantValue<*>): ProtoBuf.Annotation.Argument.Value.Builder =
         ProtoBuf.Annotation.Argument.Value.newBuilder().apply {
             constant.accept(
                 FirAnnotationArgumentVisitor,
diff --git a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/AnnotationArgumentVisitor.kt b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/AnnotationArgumentVisitor.kt
index 13ab5c323a1..631761cc2e8 100644
--- a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/AnnotationArgumentVisitor.kt
+++ b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/AnnotationArgumentVisitor.kt
@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.fir.serialization.constant
 
-abstract class AnnotationArgumentVisitor<R, D> {
+internal abstract class AnnotationArgumentVisitor<R, D> {
     abstract fun visitLongValue(value: LongValue, data: D): R
     abstract fun visitIntValue(value: IntValue, data: D): R
     abstract fun visitErrorValue(value: ErrorValue, data: D): R
diff --git a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/ConstantValue.kt b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/ConstantValue.kt
index 939e8652c0a..cc91097ac05 100644
--- a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/ConstantValue.kt
+++ b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/ConstantValue.kt
@@ -15,7 +15,7 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.constants.ClassLiteralValue
 
-sealed class ConstantValue<out T>(open val value: T) {
+internal sealed class ConstantValue<out T>(open val value: T) {
     abstract fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R
 
     override fun equals(other: Any?): Boolean = this === other || value == (other as? ConstantValue<*>)?.value
@@ -27,30 +27,30 @@ sealed class ConstantValue<out T>(open val value: T) {
     open fun stringTemplateValue(): String = value.toString()
 }
 
-abstract class IntegerValueConstant<out T> protected constructor(value: T) : ConstantValue<T>(value)
-abstract class UnsignedValueConstant<out T> protected constructor(value: T) : ConstantValue<T>(value)
+internal abstract class IntegerValueConstant<out T> protected constructor(value: T) : ConstantValue<T>(value)
+internal abstract class UnsignedValueConstant<out T> protected constructor(value: T) : ConstantValue<T>(value)
 
-class AnnotationValue(value: FirAnnotationCall) : ConstantValue<FirAnnotationCall>(value) {
+internal class AnnotationValue(value: FirAnnotationCall) : ConstantValue<FirAnnotationCall>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitAnnotationValue(this, data)
 }
 
-class ArrayValue(
+internal class ArrayValue(
     value: List<ConstantValue<*>>,
 ) : ConstantValue<List<ConstantValue<*>>>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitArrayValue(this, data)
 }
 
-class BooleanValue(value: Boolean) : ConstantValue<Boolean>(value) {
+internal class BooleanValue(value: Boolean) : ConstantValue<Boolean>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitBooleanValue(this, data)
 }
 
-class ByteValue(value: Byte) : IntegerValueConstant<Byte>(value) {
+internal class ByteValue(value: Byte) : IntegerValueConstant<Byte>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitByteValue(this, data)
 
     override fun toString(): String = "$value.toByte()"
 }
 
-class CharValue(value: Char) : IntegerValueConstant<Char>(value) {
+internal class CharValue(value: Char) : IntegerValueConstant<Char>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitCharValue(this, data)
 
     override fun toString(): String = "\\u%04X ('%s')".format(value.toInt(), getPrintablePart(value))
@@ -77,19 +77,19 @@ class CharValue(value: Char) : IntegerValueConstant<Char>(value) {
     }
 }
 
-class DoubleValue(value: Double) : ConstantValue<Double>(value) {
+internal class DoubleValue(value: Double) : ConstantValue<Double>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitDoubleValue(this, data)
 
     override fun toString(): String = "$value.toDouble()"
 }
 
-class EnumValue(val enumClassId: ClassId, val enumEntryName: Name) : ConstantValue<Pair<ClassId, Name>>(enumClassId to enumEntryName) {
+internal class EnumValue(val enumClassId: ClassId, val enumEntryName: Name) : ConstantValue<Pair<ClassId, Name>>(enumClassId to enumEntryName) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitEnumValue(this, data)
 
     override fun toString(): String = "${enumClassId.shortClassName}.$enumEntryName"
 }
 
-abstract class ErrorValue : ConstantValue<Unit>(Unit) {
+internal abstract class ErrorValue : ConstantValue<Unit>(Unit) {
     @Deprecated("Should not be called, for this is not a real value, but a indication of an error", level = DeprecationLevel.HIDDEN)
     override val value: Unit
         get() = throw UnsupportedOperationException()
@@ -107,17 +107,17 @@ abstract class ErrorValue : ConstantValue<Unit>(Unit) {
     }
 }
 
-class FloatValue(value: Float) : ConstantValue<Float>(value) {
+internal class FloatValue(value: Float) : ConstantValue<Float>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitFloatValue(this, data)
 
     override fun toString(): String = "$value.toFloat()"
 }
 
-class IntValue(value: Int) : IntegerValueConstant<Int>(value) {
+internal class IntValue(value: Int) : IntegerValueConstant<Int>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitIntValue(this, data)
 }
 
-class KClassValue(value: Value) : ConstantValue<KClassValue.Value>(value) {
+internal class KClassValue(value: Value) : ConstantValue<KClassValue.Value>(value) {
     sealed class Value {
         data class NormalClass(val value: ClassLiteralValue) : Value() {
             val classId: ClassId get() = value.classId
@@ -164,29 +164,29 @@ class KClassValue(value: Value) : ConstantValue<KClassValue.Value>(value) {
     }
 }
 
-class LongValue(value: Long) : IntegerValueConstant<Long>(value) {
+internal class LongValue(value: Long) : IntegerValueConstant<Long>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitLongValue(this, data)
 
     override fun toString(): String = "$value.toLong()"
 }
 
-object NullValue : ConstantValue<Nothing?>(null) {
+internal object NullValue : ConstantValue<Nothing?>(null) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitNullValue(this, data)
 }
 
-class ShortValue(value: Short) : IntegerValueConstant<Short>(value) {
+internal class ShortValue(value: Short) : IntegerValueConstant<Short>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitShortValue(this, data)
 
     override fun toString(): String = "$value.toShort()"
 }
 
-class StringValue(value: String) : ConstantValue<String>(value) {
+internal class StringValue(value: String) : ConstantValue<String>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitStringValue(this, data)
 
     override fun toString(): String = "\"$value\""
 }
 
-class UByteValue(byteValue: Byte) : UnsignedValueConstant<Byte>(byteValue) {
+internal class UByteValue(byteValue: Byte) : UnsignedValueConstant<Byte>(byteValue) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitUByteValue(this, data)
 
     override fun toString(): String = "$value.toUByte()"
@@ -194,7 +194,7 @@ class UByteValue(byteValue: Byte) : UnsignedValueConstant<Byte>(byteValue) {
     override fun stringTemplateValue(): String = (value.toInt() and 0xFF).toString()
 }
 
-class UShortValue(shortValue: Short) : UnsignedValueConstant<Short>(shortValue) {
+internal class UShortValue(shortValue: Short) : UnsignedValueConstant<Short>(shortValue) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitUShortValue(this, data)
 
     override fun toString(): String = "$value.toUShort()"
@@ -202,7 +202,7 @@ class UShortValue(shortValue: Short) : UnsignedValueConstant<Short>(shortValue)
     override fun stringTemplateValue(): String = (value.toInt() and 0xFFFF).toString()
 }
 
-class UIntValue(intValue: Int) : UnsignedValueConstant<Int>(intValue) {
+internal class UIntValue(intValue: Int) : UnsignedValueConstant<Int>(intValue) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitUIntValue(this, data)
 
     override fun toString(): String = "$value.toUInt()"
@@ -210,7 +210,7 @@ class UIntValue(intValue: Int) : UnsignedValueConstant<Int>(intValue) {
     override fun stringTemplateValue(): String = (value.toLong() and 0xFFFFFFFFL).toString()
 }
 
-class ULongValue(longValue: Long) : UnsignedValueConstant<Long>(longValue) {
+internal class ULongValue(longValue: Long) : UnsignedValueConstant<Long>(longValue) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitULongValue(this, data)
 
     override fun toString(): String = "$value.toULong()"
diff --git a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/FirToConstantValueTransformer.kt b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/FirToConstantValueTransformer.kt
index 69ae5d19669..06e716f57df 100644
--- a/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/FirToConstantValueTransformer.kt
+++ b/compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/FirToConstantValueTransformer.kt
@@ -13,9 +13,9 @@ import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.fir.types.coneTypeUnsafe
 import org.jetbrains.kotlin.fir.visitors.FirDefaultVisitor
 
-fun FirExpression.toConstantValue(): ConstantValue<*>? = accept(FirToConstantValueTransformer, null)
+internal fun FirExpression.toConstantValue(): ConstantValue<*>? = accept(FirToConstantValueTransformer, null)
 
-object FirToConstantValueTransformer : FirDefaultVisitor<ConstantValue<*>?, Nothing?>() {
+internal object FirToConstantValueTransformer : FirDefaultVisitor<ConstantValue<*>?, Nothing?>() {
     override fun visitElement(
         element: FirElement,
         data: Nothing?